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Training Manual
747
This manual has been prepared by Alteon Seattle, Washington for theBoeing Commercial Airplane Group.
THIS MANUAL IS FOR TRAINING PURPOSES ONLY.
NO MAINTENANCE ACTION SHOULD BE TAKEN AS A RESULT OF INFORMATION CONTAINED IN THIS MANUAL.
- ALTEON PROPRIETARY RIGHTS ARE INCLUDED IN THE INFORMATION DISCLOSED HEREIN. RECIPIENT BY ACCEPTING THIS
DOCUMENT AGREES THAT NEITHER THIS DOCUMENT NOR THE INFORMATION DISCLOSED HEREIN NOR ANY PART THEREOF SHALL BE
REPRODUCED OR TRANSFERRED TO OTHER DOCUMENTS OR USED OR DISCLOSED TO OTHERS FOR MANUFACTURING OR FOR ANY
OTHER PURPOSE EXCEPT AS SPECIFICALLY AUTHORIZED IN WRITING BY ALTEON
UNPUBLISHED - ALL RIGHTS RESERVED UNDER COPYRIGHT LAWS
(c) 2003 Alteon Training L.L.C.
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ELECTRICAL POWER -- INTRODUCTION
General
The electrical power system has components that supply
and control electrical power to the airplane. These
systems include:
- External/APU power
- Engine power
- DC power
- Standby power
- Load distribution
- Indicating.
External/APU Power
External/APU power supplies electrical power during
ground operations. It includes two external power
sources and two APU generators.
Engine Power
Engine generators supply electrical power for all usual
flight operations. There are four integrated drive
generators (IDG).
DC Power
The dc power system supplies those loads for which dc
power is necessary. It includes the batteries and
transformer rectifier units.
Standby Power
Standby power supplies power for important loads when
the primary source fails.
Load Distribution
The load distribution system controls and sends ac and
dc power to all parts of the airplane.
Indicating
Indicating includes the electrical power interfaces
with EICAS and the central maintenance computer and
related displays.
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APU and main battery
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ELECTRICAL POWER - INTRODUCTION
IDG
APU
APU
IDG
EXTERNAL
MAIN
MAINIDG
INDICATING DISTRIBUTIONSTANDBY
DC
ENGINEEXTERNAL/APUPOWER
POWER CARTS
BATTERY
EQUIPMENT
CENTER
POWER
POWER
BATTERY
GENERATORS
POWER
IDG
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ELECTRICAL POWER -- SYSTEM SIMPLIFIEDELECTRICAL POWER -- SYSTEM SIMPLIFIED
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ELECTRICAL POWER -- SYSTEM SIMPLIFIED
General
The ac and dc distribution systems send electrical
power to all parts of the airplane. The ac distribution
system has these buses:
- AC 1, 2, 3, and 4
- F/O transfer (AC F/O XFR)
- Capt transfer (AC CAPT XFR)
- AC standby (AC STBY)- Ground handling (AC GH)
- Ground service (AC GS).
The dc distribution system has these buses:
- DC 1, 2, 3, and 4
- DC ground handling (DC GH)
- APU hot battery (APU HOT BAT)
- Main hot battery (MN HOT BAT)
- Main battery (MN BAT)
- APU battery (APU BAT).
AC Buses 1, 2, 3, and 4
The IDGs, APU generators, or external power carts
supply power to the ac buses. An IDG connects to its
related bus when the related generator circuit breaker
(GCB) closes. The IDGs are in parallel when the related
bus tie breakers (BTB) and GCBs close. The
synchronizing (synch) bus has two sections that connect
by a split system breaker (SSB). With correct use of
the breakers, a generator can supply power to one or
more load buses and one or more IDGs can operate in
parallel. The power output of the APU generators orexternal power carts can also connect to the load buses
through the auxiliary power breakers (APB) or external
power contactors (XPC).
Transfer Buses
There are two transfer buses, the captain and the first
officer. The captain transfer bus usually gets power
from ac bus 3. If ac bus 3 does not have power, thetransfer bus connects to ac bus 1 for power. The first
officer transfer bus usually gets power from ac bus 2
but connects to ac bus 1 if ac bus 2 does not have
power.
AC Standby Bus
The standby ac bus usually gets power from ac bus 3 but
connects to the static inverter if ac bus 3 does not
have power, the battery switch is on, and the standby
power switch is in the AUTO position.
The APU AC standby bus is an alternative power source
for the captain primary instruments when power to those
instruments fail, the battery switch is ON, and the
standby power switch is in the AUTO position.
Ground Handling Bus
The ground handling bus gets power from the APU
generator 1 or the external power receptacle 1 through
the ground handling relay (GHR). The bus gets power
automatically when external power or APU power is
- 5 -
so it's necessary to connect external powerreceptacle 1(the left one as you face the
receptacle) to operate low cargo door.
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ELECTRICAL POWER -- SYSTEM SIMPLIFIED
available. If APU and external power are available at
the same time, external power connects to the ground
handling bus. The ground handling bus does not get
power in flight.
Ground Service Bus
The ground service bus always gets power from the ac
bus 1 if that bus has power. If ac bus 1 does not have
power, the ground service bus can get power from
external power 1 or APU generator 1 through the ground
service select relay (GSSR) and ground service transfer
relay (GSTR).
DC Buses 1, 2, 3, and 4
Dc buses 1, 2, 3 and 4 gets power from transformer
rectifier units (TRUs). The dc buses supply this power
through dc isolation relays (DCIRs). The bus tie switch(P5) controls the dc isolation relays.
DC Ground Handling Bus
The dc ground handling bus gets power when the ac
ground handling bus has power. TRUs supply the dc
power. These TRUs are not the same as the TRUs on the
main dc buses.
DC Cargo Handling Bus
The dc cargo handling bus gets power when the ac cargo
handling bus has power. A TRU supplies the dc power.
The TRU is the same as the TRU used on the dc ground
handling buses.
Main and APU Hot Battery Buses
The main and APU hot battery buses get power from the
main and APU batteries. When the ground service bus has
power, the battery chargers supply power to the buses
and charge the batteries.
Main and APU Battery Buses
The main and APU battery buses usually get power from
dc bus 3. If dc bus 3 does not have power and the
battery switch is on, the buses get power from their
related batteries.
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1
1
ELECTRICAL POWER - SYSTEM SIMPLIFIED
APU AC STBY BUSAPU STAT INV
BAT SW
STAT INV
MN BAT
MN HOT BATAPU HOT BAT
DC GH
T/R B/C B/C
AC GSAC GH
GSTR
BOTH STATIC INVS ARE OFF WHEN STBY POWER SW IS OFF
AC 1
DC 1
AC 2
DC 2
AC CAPT XFRAC F/O XFR
AC STBY
APU BAT
AC 3
DC 3
AC 4
DC 4
EXT 1
XPCSSB SYNCH BUS
GSSRGHR
T/R 1 T/R 2
XPCAPB
EXT 2
BTB
GCB
DCIR
OFF
STBY
T/R 4T/R 3
AUTO
BAT
APB
APU1
PWR SW
SYNCH BUS
APU2
IDG1
IDG2
IDG3
IDG4
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ELECT PWR -- MANUAL CONTROL - SYSTEM CONTROL PANEL
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ELECT PWR -- MANUAL CONTROL - SYSTEM CONTROL PANEL
General
The electrical system panel is in the flight deck on
the P5 overhead panel. The panel has switches and a
selector which gives automatic or manual control of the
electrical power system.
Drive Disconnect
The drive disconnect switch (DRIVE DISC) is a momentaryaction switch that has a guard. You push this switch to
disconnect the IDG input drive from the engine.
The amber DRIVE light in the switch gives an indication
of low pressure or high temperature of the IDG oil.
Generator Control
The generator control switch (GEN CONT) is an alternateaction switch. Operation of the switch to the latched
in position closes the generator field relay and lets
the generator circuit breaker (GCB) close when good
power is available. Operation to the out position opens
the generator field relay and the GCB.
ON is a mechanical indication of automatic GCB
operation. OFF is an amber light indication of an open
GCB.
Bus Tie
The bus tie switch (BUS TIE) is an alternate action
switch. Operation of the switch to the latched in
position gives automatic operation of the bus tiebreaker (BTB) and dc isolation relay (DCIR). Operation
to the out position opens the BTB and the DCIR.
AUTO is a mechanical indication of automatic BTB and
DCIR operation. ISLN is an amber light indication of an
open BTB.
External Power 1 and 2
The external power switch (EXT PWR 1/EXT PWR 2) is a
momentary action switch. You push the switch to open or
close the external power contactor if external power is
available.
AVAIL is a white light indication of good external
power connected to the airplane. ON is an indication of
a closed external power contactor.
APU Generator 1 and 2
The APU generator switch (APU GEN1/APU GEN 2) is a
momentary action switch. You push the switch to open or
close the auxiliary power breaker (APB) if auxiliary
power is available.
AVAIL is a white light indication of good APU power. ON
is an indication of a closed APB.
Battery
The battery switch (BATTERY) is an alternate action
switch that has a guard. Operation of the switch to the
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switchWlatchedinv—OM
GCBW(openv—rÀaK
switchW(latched inv—OM
BTBW(openv—r a
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ELECT PWR -- MANUAL CONTROL - SYSTEM CONTROL PANEL
latched in position connects the battery to the main
battery bus.
ON is a mechanical indication of a closed battery
switch. OFF is an amber light indication that the
battery switch is off.
Utility
The utility bus switch (L-UTILITY-R) is an alternate
action switch. Operation of the switch opens or closes
the electrical load control unit (ELCU) relays. The
left and right utility bus switches each control two
galley ELCUs and two utility bus ELCUs.
ON is a mechanical indication of a closed utility bus
switch. OFF is an amber light indication of an open
ELCU(s). The OFF indication does not show during load
shedding.
Standby Power
The standby power switch is a three position rotary
switch. In OFF the standby power is off.
In AUTO if there is a loss of ac bus three:
- Ac standby bus moves to the static inverter- Main battery bus moves from dc bus 3 to the main
battery
- APU battery bus moves from dc bus 3 to the APU
battery.
In BAT the main battery connects to the main battery
bus and the APU battery connects to the APU battery bus
if the battery switch is on. The static inverter also
supplies the ac standby bus.
- 10 -
static inverters are off when standbypower SW is off.
ON,OFFSêf/Nã‹hswitchvîRMv—OMn
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ELECT PWR - MANUAL CONTROL - SYSTEM CONTROL PANEL
wAUTO
ISLNa
DRIVE
w
a
w
a
ON
OFF
1 32
BUSTIE
GENCONT
DRIVEDISC
BUS
wAUTO
ISLNa
DRIVE
w
a
w
a
ON
OFF
BUS
wAUTO
ISLNa
DRIVE
w
a
w
a
ON
OFF
BUS
wAUTO
ISLNa
DRIVE
w
a
w
a
ON
OFF
BUS
4
STANDBY POWER
OFFAUTO
BAT
L - UTILITY - R
EXT PWR 1 APU GEN 1
ON
OFF
BATTERY
ONw
aOFF
ONw
a
OFF
ONw
aON ON ON
w
AVAIL
APU GEN 2 EXT PWR 2
APU
ONOFF START
SHUTTER CLOSED
w
AVAIL w
AVAIL w
AVAIL w
SHUTTEROPEN/ON EXPOSED
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General
The generator manual reset panel is in the flight deck
on the aft overhead panel (P461). The panel has seven
momentary toggle switches that have guards. It gives
indication and manual control for the:
- Engine generator field relays
- APU generator field relays
- Split system breaker (SSB).
ELECT PWR -- MANUAL CONTROL - GENERATOR MANUAL RESET PANEL
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ELECT PWR - MANUAL CONTROL - GENERATOR MANUAL RESET PANEL
GEN FIELD MAN RESET
1 2 3 4
FIELDOFF w
1 APU 2SPLIT SYSTEM
BREAKER
OPENw
FIELDOFF w
FIELDOFF w
FIELDOFF
w
FIELDOFF w
FIELDOFF w
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General
You can connect one or two external power sources to
the airplane.
External power comes from external power carts or gate
power through two receptacles on the right forward side
of the airplane. From the receptacles the power goes to
external power contactors in P714 and P715. These
contactors connect the external power to the airplane
electrical system.
ELECT PWR -- EXT POWER - SOURCES
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ELECT PWR - EXT POWER - SOURCES
P714
P715
EXTERNAL
EXTERNALPOWER CARTS
POWERRECEPTACLES
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General
All of the components in the external power system are
in the main equipment center (MEC) except the
electrical system control panel, generator manual reset
panel, and the external power panel. The external power
system includes these components:
- External power panel with two receptacles
- Ground handling relays (2)
- Current transformers (4)- External power contactors (2)
- Bus control units (2)
- Transformer rectifier units (2)
- Ground service relays (4)
- Split system breaker
- Generator manual reset panel
- Electrical system control panel.
ELECT PWR -- EXT POWER - COMPONENTS
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ELECT PWR - EXT POWER - COMPONENTS
GENERATOR MANUAL
EXTERNAL POWER
ELECTRICAL SYSTEM
BUS CONTROL
TRANSFORMER
EXTERNAL POWER PANEL
CURRENT
GROUND SERVICE
SPLIT SYSTEM
GROUND HANDLING
w
FIELD
GEN FIELD MAN RESET
wOFFFIELD
wOFFFIELD
wOFFFIELD
OFF wOFFFIELD
w
OPEN
BREAKERSPLIT SYSTEM
2APU1
wOFFFIELD
4321
BREAKER
RESET PANEL (P461)
RELAY (4)
RECTIFIERUNIT (2)
UNIT (2) CONTACTOR (2)
TRANSFORMER (4)
RELAY (2)
(P36)
CONTROL PANEL (P5)
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General
Two external power carts supply three-phase, 400 Hz,
115v ac to the airplane through the external power
receptacles. Before the power can connect to the
airplane systems, two bus control units (BCUs) monitor
the power for quality. BCU 1 monitors the power from
the aft receptacle. BCU 2 monitors the power from the
forward receptacle. The BCUs make a check for these:
- Plugs are fully in- Voltage, frequency, and phase are correct
- Plug interlock system does not have a short to the
main feeder wires.
When the BCUs find that all of these conditions are
correct, they cause the external power AVAIL lights to
come on at the electrical system control panel in the
flight compartment.
Ground Handling Bus
When BCU 1 causes the external power AVAIL light to
come on, it also energizes the ground handling relay
(GHR). This gives power to the ground handling bus
(GHB). Cargo loading, cleaning outlets, and fueling are
some of the systems on the GHB.
Ground Service Bus
There is a ground service switch at door 2 left.
Operation of this switch gives a signal to BCU 1 to
energize the ground service relays. These relays
connect power to the ground service bus (GSB). Cabin
lights and the battery chargers are some of the systemson the GSB.
External Power
The two momentary switches EXT PWR 1 and EXT PWR 2 are
on the electrical system control panel. When you push
EXT PWR 1, it gives a signal to BCU 1 to close its
related external power contactor (XPC). The ON light in
the switch comes on, and the AVAIL light goes off. BCU2 closes the split system breaker (SSB) at this time if
no other power is on the synchronizing (synch) bus. The
aft power cord now supplies power to the airplane. When
you push EXT PWR 2, it gives a signal to BCU 2 to open
the SSB and close its related XPC. The ON light in the
switch comes on, and the AVAIL light goes off. EXT PWR
1 now supplies power to the left side of the synch bus,
and EXT PWR 2 supplies power to the right side of the
synch bus.
ELECT PWR -- EXT POWER - OPERATION
- 18 -
E,F pin
using the power from GHB , it's not necessary to
operate the EXT POWER 1&2 SW.
GSSRGSTR
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GROUNDGROUND
SSB
TRIP
CLOSE SSB
wAUTO
BUSwAUTO
wAUTO
wAUTO
STANDBY POWER
OFFAUTO
BAT
L - UTILITY - R
EXT PWR 1 APU GEN 1
ON
OFF
BATTERY
ONw
a
w w
AVAIL
OFF
ONw
a
OFF
ONw
aON
w
AVAIL
ON
w w
AVAIL
ON
w
AVAIL
APU GEN 2 EXT PWR 2
APU
ONOFF START
BCU 1
EXTERNAL
TRIP
BCU 2
LEFT
GSR
RIGHT
AFT (LEFT) (NO. 1) FWD (RIGHT) (NO. 2)
OPEN/CLOSEOPEN/CLOSE
XPC 1
XPC 1 XPC 2
XPC 2
ELECTRICAL SYSTEM CONTROL
EXTERNAL POWERRECEPTACLE
EXTERNAL POWERRECEPTACLE
PANEL (P5)
POWER OK
OPEN/CLOSE
SERVICE
OPEN/CLOSE
SERVICESELECTED
CLOSE
SYNCH BUS SYNCH BUS
GHB
GSB
ELECT PWR - EXT POWER - OPERATION
GHR
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General
The external power panel is on the right side of the
fuselage aft of the nose wheel well doors. The panel
includes:
- Two 250 ampere receptacles (the aft receptacle is
primary because the ground handling bus gets power
through it)
- AC CONNECTED lights that come on when good quality
power is available to the airplane.- POWER NOT IN USE lights that show when external
power or ground service is not in use.
ELECT PWR -- AC EXT POWER - POWER PANEL
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ELECT PWR - AC EXT POWER - POWER PANEL
AC CONNECTED LIGHT
AC CONNECTED
FWDAFT
POWER
EXTERNAL
NOT IN USE
LIGHTSLIGHT
POWERRECEPTACLE
(LEFT NO. 1) (RIGHT NO. 2)
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E,F pin
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General
There are two inter-changeable ground handling relays
(GHR) in P714 in the MEC. They use 28 volts dc for
control and are 3 pole, double throw, center off type
relays. BCU 1 energizes these relays to connect the
correct power source for the ground handling bus. The
two power sources are external power 1 and APU
generator 1.
ELECT PWR -- AC PWR DISTRIBUTION - GROUND HANDLING RELAYS
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ELECT PWR - AC PWR DISTRIBUTION - GROUND HANDLING RELAYS
DC FROM
FROM APU
DC FROM
TO
FROM AFT EXTERNAL
P714
POWER RECEPTACLE3 PHASE 400 HZ 115/200V
BCU 1
GROUNDHANDLING
BUSSES
BCU 1
GENERATOR 13 PHASE
400HZ115/200V
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General
There are four current transformers (CT) related to
external power. They are in P714 and P715 in the MEC.
The CTs are used for:
- Metering (data sent to BCUs for percent load
indications on EICAS)
- Differential fault protection (data used by the
BCUs)
- Load reduction (data sent to BCUs for loadreduction circuits).
Characteristics
Each transformer assembly has a toroidal shaped core
with secondary winding wires that connect to an output
connector. Main ac feeder lines goes through the large
holes in the transformer and are the primary winding
for each transformer core. The turns ratio of all thewindings is 1000 to 1. If the primary winding (feeder
line) is 115 volts ac, secondary winding voltage is as
much as 115,000 volts with the connector off (no load).
Usually secondary voltages are very low because the
secondary loads have a low resistance.
WARNING: DO NOT DISCONNECT THE TRANSFORMER OUTPUT
CONNECTION WITH THE FEEDER LINES POWERED. THE
POTENTIALLY HIGH VOLTAGES COULD DAMAGE THETRANSFORMER OR RESULT IN INJURY TO PERSONNEL.
ELECT PWR -- AC EXT POWER - CURRENT TRANSFORMER
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ELECT PWR - AC EXT POWER - CURRENT TRANSFORMER
CONNECTOR
P714
P715
1000
1000
1000
A PHASE
B PHASE
C PHASE
FEEDERLINES
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General
There are two external power contactors (XPC) that
connect external power to the airplane synch bus. They
are in the MEC. The contactor for the aft external
power receptacle is in P714. The contactor for the
forward external power receptacle is in P715.
Characteristics
Each external power contactor has these properties:
- Conducts three phase ac
- Can operate at 260 amperes continuous and 350
amperes for 15 seconds
- Can open 2000 amperes
- Uses 28 volts dc for control
- Electrically held closed
- Spring loaded open.
Operation
The contactor closes when the BCU energizes the coils
of the contactor with 28 volts dc. After the contactor
closes, contacts remove power from one of the two
coils. This is because less power is necessary to hold
the contactor closed than to initially close it. This
decreases the power necessary to keep the contactor
closed.
The contactor opens when the BCU removes the coil
power. This lets the spring open the contactor.
ELECT PWR -- AC EXT POWER - POWER CONTACTORS
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ELECT PWR - AC EXT POWER - POWER CONTACTORS
P714
A
B
C
A
B
C
CLOSE AND
SPRING
P715HOLD INPUT28V DC
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General
There are two bus control units (BCU) in the MEC on the
E-1 and E-2 equipment shelves. They operate on 28 volt
dc. The units are the same and inter-changeable. The
BCUs monitor their related external power and APU power
channels and the airplane electrical system to give
control and protection. Circuit breakers on the front
panel give the internal circuits protection from shorts
on control and indication lines.
The BCUs control the XPCs, APBs and SSB. They are also
the primary communication link between the electrical
system and the EFIS/EICAS interface units (EIU).
Control Functions
Each BCU has these control functions:
- Ground power- APU interface signals
- APU generator interface
- APU generator field
- Auxiliary (APU) generator control unit (AGCU)
interface signals
- APB
- XPC
- SSB
- Anticycle and lockout functions- Master frequency reference
- No-break power transfer
- Ground service and ground handling bus
- Load management
- Autoland control (electrical system)
- DC and standby systems interface- Instrument bus voltage sensing unit (IBVSU)
interface
- System BITE
- Interface with the EIU and CMC.
Protection Functions
Each BCU has these protective functions:
- Ground power over/under voltage
- Ground power over/under frequency
- Ground power phase rotation
- Ground power plug fault
- Synch bus negative sequence voltage
- Synch bus differential fault
- Sustained unlike source protection
- CPU failure
- BCU power supply failure- APU generator bearing failure.
ELECT PWR -- AUTOMATIC CONTROL - BUS CONTROL UNITS
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and GHR,GSTR,GSSR
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ELECT PWR - AUTOMATIC CONTROL - BUS CONTROL UNITS
- CONTROL- PROTECTION
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General
Two external power transformer rectifier units (TRU)
are in the forward left MEC at the station 400
bulkhead. They are TRU A and TRU B.
The TRUs are solid state devices that change 115 volts
ac to 28 volts dc. They keep the dc output up to a 20
ampere load. Both TRU A and TRU B get power from the
GHB. Each TRU supplies a separate dc GHB.
ELECT PWR -- AC EXT POWER - TRANSFORMER RECTIFIER UNITS
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AC GHBTRU
TRU
DC GHB
DC GHB
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ELECT PWR - AC EXT POWER - TRANSFORMER RECTIFIER UNITS
FWD
TRU (A)
TRU (B)
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General
There are four ground service relays (GSR) in P714 in
the MEC. Each relay is a 3 pole, double throw type
relay and is inter-changeable with the others. BCU 1
energizes the relays to connect power for the ground
service bus. The three possible sources of ground
service power are:
- AC bus No. 1
- APU generator No. 1- External power No. 1.
ELECT PWR -- AC PWR DISTRIBUTION - GROUND SERVICE RELAYS
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ELECT PWR - AC PWR DISTRIBUTION - GROUND SERVICE RELAYS
P714
EXT 1
(4)
28V DC FROM
APU 1
PERMANENT
GSSR (2) GSTR (2)
28V DC FROM
GROUND
PERMANENT
AC 1MAGNET
BCU 1BCU 1
SERVICEBUS
MAGNET
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General
The split system breaker (SSB) electrically connects
the left and right synch buses. It is in the P92 panel
in the MEC. The breaker is a magnetic latch type and
can operate at 450 amperes continuous. It can open up
to 5000 amperes. The breaker must get 28 volts dc to
close or to open. The control signals to the SSB come
from the BCUs. BCU 1 or BCU 2 can open the SSB. Only BCU
2 can close it. The SSB is not inter-changeable with
the other breakers on the airplane.
ELECT PWR -- MANUAL CONTROL - SPLIT SYSTEM BREAKER
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ELECT PWR - MANUAL CONTROL - SPLIT SYSTEM BREAKER
P92
CLOSE28V DC
TRIP28V DC
COMMON
CLOSE (PERMANENT MAGNET)
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General
You use the ground handling bus (GHB) for ground
operations. It can only get power on the ground. The
bus has two sections and can get power from external
power 1 or APU generator 1. BCU 1 controls the
connection of power to the GHB.
External Power
When there is external power at the aft external powerreceptacle, BCU 1 monitors the average of all three
phases for these:
- Voltage (104.5 to 125v ac)
- Frequency (375 to 425 hz)
- Phase rotation (A B C)
- No overcurrent or overvoltage on pins E and F (this
can occur if the external power plug had damage and
there was a short between the main ac voltage andpins E or F)
- Pin E/F connected (this makes sure that the
external power plug is fully in).
After BCU 1 finds these conditions, it gives an
external power available signal. At this time, these
conditions can keep external power off the GHB:
- Airmode (BCU 1 gets data that three IDGs are above6100 rpm)
- GHR has a failure (BCU 1 monitors for a short to
ground on the control wire to the GHRs. If itsenses a short, the BCU removes the close command
to the relay).
If the conditions for input power are true, and the
inhibit conditions are not true, the BCU energizes the
two GHRs. The GHB then gets external power.
APU Power
The auxiliary generator control unit (AGCU) monitors
power from APU generator 1. When the APU is above 95
percent, and the voltage is between 104 and 130v ac,
the AGCU sends an APU power ready signal to the BCU. If
external power is not available, and the inhibit
conditions are not true, APU generator 1 gives power to
the GHB.
ELECT PWR -- AC PWR DISTRIBUTION - GROUND HANDLING BUS CONTROL
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ELECT PWR - AC PWR DISTRIBUTION - GROUND HANDLING BUS CONTROL
PIN E/F
AIR MODE
BAT SW
HOT BAT BUS
DC GHB
BCU STBY
R117 GHR 1
R118 GHR 2
TO APB
MAIN BATTERY
AC
NOT IN
PHASE
VOLTS/FREQ
NO FAULTS ON
POWER LOGIC
F
E
N
C
BA
TO
BCU 1
TO
GSTRXPCR284 GND
G
A
APU RPM >95%
APU GEN 1AGCU 1
GHB
TRU TRU GHB
EXT PWRAVAILABLE
GHR FAILED
APU POWERREADY
USE
CONN
PWR RECEPTACLE 1(AFT) (P36)
INTERLOCK
ROTATION OK
OK
BUS
(APU-BCU 1)
(MAIN-BCU 2)
SAFETY(P414)
(P714)
(P714)
SECT 1
SECT 2
INTERNALCIRCUITS
XPC
PWR XFRRLY (P414)
A B
CONNECTED
W
W
B
A
TRU
B
VOLTS OK
A
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General
Power for the ground service bus (GSB) comes from AC 1
if AC 1 has power. If AC 1 does not have power, power
for the GSB is selected by a push of the ground
services switch on the attendants panel at door 2L.
This connects power from either external or APU
sources. The external source has priority. When GSB
power is from a selected source, a light in the ground
services switch on the attendants panel comes on.
ELECT PWR -- AC PWR DISTRIBUTION - GROUND SERVICE BUS POWERELECT PWR -- AC PWR DISTRIBUTION - GROUND SERVICE BUS POWER
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ELECT PWR - AC PWR DISTRIBUTION - GROUND SERVICE BUS POWER
GSB
ATTENDANTS PANEL
LIGHTS/CHIME
FORWARD
CHIME OFF
AFT
CHIME OFF
LIGHT
WORK
LIGHT
GROUND
LIGHTS
EMERGENCY
ACCESS
UPPER DECK
w w w w
rw w w
OVERSTAIR
THRESHOLD
DOOR 2L
SERVICESLIGHT
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ELECT PWR -- AC PWR DISTRIBUTION - GROUND SERVICE BUS CONTROL
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ELECT PWR -- AC PWR DISTRIBUTION - GROUND SERVICE BUS CONTROL
General
The ground service bus (GSB) is for ground and flight
operations. The GSB has two buses. They are the GSB and
the ground service utility bus. The control logic is
the same for the two buses. Power for the ground
service utility bus goes through the energized contacts
of utility ELCU 1 before it goes to the transfer relay.
The data that follows refers to the GSB and the ground
service utility bus unless it tells you differently.
There are three possible power sources for the GSB:
- AC bus 1
- External power 1
- APU generator 1.
Components
These components have a relation to the GSB:
- BCU 1 in MEC
- Ground service switch at the flight attendant
station, door 2 left
- Two ground service transfer relays (GSTR) in P714
in the MEC
- Two ground service select relays (GSSR) in P714 in
the MEC.
One of the two GSTRs is for the ground service bus and
the other for the ground service utility bus. When they
close, the relays connect the APU or external power to
the GSB. When they open, the relays connect ac 1 power
to the GSB.
One of the two GSSRs are for the ground service bus and
the other for the ground service utility bus. When they
close, the relays connect external power for the GSB
through the GSTRs. When they open, they connect APU
power.
AC Bus No. 1 Power
When ac 1 has power, the GSTR deenergizes. This lets ac
1 give power to the GSB. For the ground service utility
bus to get power from ac bus 1, the left utility switch
on the electrical system control panel must be on.
External Power
If ac 1 does not have power, you must push the groundservice switch to get ground service power. When the
conditions that follow are true, the BCU energizes the
GSTRs and GSSRs to let external power 1 give power to
the GSB:
- External power in limits
- GSSR or GSTR not failed (if the BCU finds a short
to ground on the control wire to the GSSR and GSTR,
it removes the close command to the relays).
NOTE: A reset is accomplished by cycling the ground
service switch.
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ELECT PWR -- AC PWR DISTRIBUTION - GROUND SERVICE BUS CONTROL
APU Power
If ac 1 does not have power, you must push the ground
service switch to get ground service power. When the
conditions that follow are true, the BCU energizes the
GSTRs to let APU generator 1 give power to the GSB:
- External power not available (ground service uses
external power 1 if it is available)
- APU power in limits
- GSTR not failed (if the BCU finds a short to groundon the control wire to the GSSR, it removes the
close command to the relay).
NOTE: A reset is accomplished by cycling the ground
service switch.
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ELECT PWR - AC PWR DISTRIBUTION - GROUND SERVICE BUS CONTROL
GSSR
GSTR
GSTR
GSTR FAULT
CYCLE GS
FAULT
FAULT
GSSR FAULT
EXT PWR RDY
28V DC
ON
GROUND SERVICE
FLIGHT ATTENDANT
AC 1
AIRMODE
GSSR
TRIP/CLOSE
AGCU 1
APU PWRBCU NO. 1
TO GHR(S)
EXT 1
APB
BTB
APU1
XPC
U-ELCU-1
BAT
POWERED
SWITCH
PANEL (DOOR 2 LEFT)
CHGR
READY
SWITCHTO RESET
SENSING
LOGIC
SENSING
DC GND HDLG BUS
AC 1
BATCHGR
GND SERV BUS
GND SERV UTIL BUS
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General
There are two external power contactors (XPCs) that
connect external power to the airplane synch bus. One
contactor is in P714, and one is in P715 in the MEC.
These are the components related to the XPCs:
- External power panel (P36)
- BCU 1
- BCU 2
- EXT PWR 1 switch- EXT PWR 2 switch.
Control
DC power for the BCUs comes from one of four power
sources. This lets the BCU operate and give control and
protection during all normal conditions of operation.
These are the sources:
- Three-phase ac from external power (an internal
TRU in the BCU makes this dc)
- Main battery bus
- DC ground handling bus
- APU hot battery bus with the battery switch on for
BCU 1 (BCU 2 uses the main hot battery bus with the
battery switch on).
The BCUs look at the external power and do a check forthese:
- Voltage (104.5 to 125v ac)
- Frequency (375 to 425 hz)
- Phase rotation (A B C)
- No faults on pins E or F (over current or overvoltage on these pins E and F give an indication of
a short in the power plug)
- Pin E and F connected (this makes sure that the
external power plug is fully in).
When the above conditions are true, the BCUs cause the
external power AVAIL lights in the P5 external power
switches, the NOT IN USE, and the AC CONNECTED lights
to come on. The NOT IN USE light goes off when the XPCor GSTR closes.
These are the conditions necessary for the external
power close command:
- External power available
- No inputs from trip logic (These inputs open the
XPC for system protective trips, power transfers
and last source on logic)- A close command from the external power switch and
not in air mode (There is a 4.5 second interval if
there was a close command before this one).
When these conditions are true, the BCU sends an
external power close command to the no break power
transfer logic. This logic sends the close command to
the XPC. When the XPC closes, these things occur:
- Sync bus gets three-phase, 400 hz ac
- External power ON light comes on
- AVAIL light goes off
- NOT IN USE light on P36 goes off.
ELECT PWR -- EXT POWER - CONTACTOR CONTROL
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ELECT PWR - EXT POWER - CONTACTOR CONTROL
DC GHB
SYNCH
PIN E/F
TRIP LOGIC
AC
XPCGSTR
EXT PWR AVAIL
PHASE
VOLTS/FREQ
TRU
TO INTERNAL
MAIN
EXT POWER
F
E
N
C
B
A
EXT PWR AVAIL
BCU 1
TRIP/CLOSE
NOT IN
NO FAULTS ON
AIR
EXT PWR
EXT
ELECTRICAL SYSTEM
NO BREAKXPC
POWER LOGIC
BCU STBY PWR
HOT BAT BUS
BAT SW
AV
ILw
w
ONA
BATTERYBUS
XFR RLY (P414)
(APU-BCU 1)(MAIN-BCU 2)
CONTROL PANEL (P5)
PWRON
USE
CONN
(P36)
NOTE: SYSTEM 1 SHOWN SYSTEM 2 SIMILAR
LOGIC(4.5 SEC TD)
POWERTRANSFER
BUS
CIRCUITS
OK
ROTATION OK
INTERLOCK
CONNECTED
CLOSECOMMAND
MODE
W
W
RECEPTACLE 1
EXT PWR 1
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Manual Operation
The SSB control switch manually controls the split
system breaker (SSB). The switch is a momentary type
with a guard. It is on the generator manual reset panel
in the flight deck. Each operation of the switch
changes the position of the SSB from open to closed or
closed to open. The switch does not cause operation of
the SSB when the BCUs are in air mode or there are
sources on each side of the synch bus that cannot
connect together.
If there is IDG power on both sides of the synch bus,
you can manually open the SSB with the SSB control
switch. If you operate the switch again, the SSB does
not close until an auto parallel sequence is done.
SSB Close
The SSB automatically closes for these conditions:
- First source on the synch bus
- A close command from BCU 1 (a close signal from BCU
1 goes to BCU 2 and BCU 2 closes the SSB)
- IDG power is on each side of the synch bus, and
parallel conditions and a 300 MS time delay is true
- One side of the synch bus loses power after each
side had power (not as a result of a synch bus
malfunction, break power transfer, or the SSBcontrol switch).
The close signal goes to the SSB through the usually
closed contacts of the SSB protection relay.
SSB Trip
The SSB automatically opens for:
- No break power transfer (NBPT) logic under some
electrical system configurations
- Sources on each side of the synch bus that cannot
connect together
- Loss of power to the opposite BCU (loss of
protection to one side of the synch bus)
- A negative sequence or differential fault on thesynch bus.
A negative sequence or differential fault resets for
these conditions:
- IDG power on each side of the synch bus and auto
parallel conditions are true
- Operation of the SSB switch
- Power removed from the airplane (the first sourceon resets the fault).
Indication
A light below the SSB control switch shows SSB
position. The light is on when the SSB is open. The
light gets power through a set of auxiliary contacts in
the SSB.
ELECT PWR -- EXT POWER - SPLIT SYSTEM BREAKER CONTROL
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ELECT PWR - EXT POWER - SPLIT SYSTEM BREAKER CONTROL
300 MS
BPT LOGIC
FIRST SOURCE ON SYNCH BUS
CLOSE COMMAND (BCU 1)
POWER ON BOTH SIDES
S
CLOSE
OPEN
R
AUTO PARALLEL COMPLETE
IDG POWER ON BOTH
EXT/APU/UNLIKE POWER ON
EXT/APU/UNLIKE POWER ON
FIRST SOURCE ON SYNCH BUS
AUTO PARALLEL COMPLETE
OPP BCU SYNCH BUS FAULTS
LOGICTRIP/CLOSE
AIRMODE
SR
SYNCH BUS FAULTS
TRIP
CLOSEOS
OS
IDG POWER ON BOTH
S R
NBPT LOGIC
OPPOSITE BCU NOT POWERED
SYNCH BUS FAULTS
AIRMODE
CYCLE SSB SW
AIRMODE
SSB (P92)
BCU 2 (E2-2)
SPLIT SYSTEM
OPEN
SSB CONT SW
CLOSE
OPEN
FROM
R8128 SSB
SIDES OF SYNCH BUS
OF SYNCH BUS
TD
BOTH SIDES OF SYNCH BUS
SIDES OF SYNCH BUS
BOTH SIDES OF SYNCH BUS
AUXCON-TACTS
PROTECTION(P92)
BCU 1
(P461)
BREAKER
A
A
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General
The electrical system can do no break power transfers
(NBPTs). A NBPT is a change of an ac power source
without a break in power. To do this, power sources
momentarily operate in parallel. All power transfers
between engine generators, APU generators and external
power are no break power transfers. The only time power
breaks occur are when two external power sources or two
APU generators connect to an airplane that has no other
electrical sources connected. If all buses get powerfrom one external power source and you connect the
second external source, the SSB opens before the second
XPC closes. This causes a momentary break in power. If
all buses get power from an APU generator and you
connect the second APU generator, there is also a
momentary break in power. The two BCUs have the primary
control for NBPT.
Power Configurations
Before you connect EXT power to the airplane, the NBPT
logic in the BCUs finds the power configuration of the
synch bus. These are the seven possible power
configurations of the synch bus:
- No power
- Adjacent APU generator
- Adjacent IDG- Opposite APU generator with SSB closed
- Opposite IDG with SSB closed
- Adjacent and opposite IDG
- Opposite external power with SSB closed.
ELECT PWR -- EXT POWER - NO BREAK POWER TRANSFER
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ELECT PWR - EXT POWER - NO BREAK POWER TRANSFER
EXTERNAL
NO POWER
OPPOSITE APU
OPPOSITE
SSB
SYNCH BUS POWER
NO BREAK POWER
POWER INTERRUPT
ADJACENT IDG
OPPOSITE IDG
ADJACENT
ADJ AND OPP
APU GENERATORPOWER
CLOSED
GENERATOR
IDG
EXTERNAL POWER
TRANSFER
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General
When the no break power transfer logic in BCU 1 senses
no power on the synch bus and an external power close
command, it closes its XPC and sends a signal to BCU 2
to close the SSB. If the close command goes to BCU 2
with a dead synch bus, BCU 2 closes its XPC and the SSB.
BCU 1 and BCU 2 can open the SSB, but only BCU 2 can
close it.
ELECT PWR -- EXT POWER - NBPT - DEAD SYNCH BUS
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ELECT PWR - EXT POWER - NBPT - DEAD SYNCH BUS
NO BREAK POWERCLOSE
XPC
SSB
BCU 2BCU 1 (E1-2)
CLOSEEXT PWR 1
POWER ON ADJ
SSB
CLOSECOMMAND
SYNCH BUS
TRANSFER LOGIC
LOGIC
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General
If the synch bus has power from an APU generator and
you connect power from an adjacent external source, the
no break power transfer (NBPT) logic momentarily
connects the two sources in parallel. The adjacent APB
then opens to remove the APU generator power from the
synch bus.
Operation
Before the NBPT logic in the BCU connects the two power
sources in parallel, a comparator circuit compares
voltage, frequency and phase between the synch bus
power and the external power. Differences must be less
than:
- Voltage, 10 volts
- Frequency, 3 Hz
- Phase, 20 degrees
If there is a frequency difference of more than 3 Hz,
the BCU gives a speed command to the APU controller
(APUC). This increases or decreases the APU speed. All
speed signals that go to the APUC go through BCU 1.
When the voltage, frequency and phase are in limits,
the XPC closes. The BCU senses the position of the XPC
through a set of auxiliary contacts in the XPC. Afterthe XPC closes, the BCU opens the APB. The power on the
synch bus now comes from the external source.
The BCU has a 6 second time delay that becomes active
when the close command signal goes to the BCU. This
time delay causes the APB to open if voltage, frequency
and phase are not in limits after 6 seconds. After this
time delay the APB opens and removes power from the
synch bus, and the XPC closes. This causes a momentary
break in power. When the XPC closes, the 6 second time
delay resets.
Sustained Unlike Source Protection
Sustained unlike source protection (SUSP) is a
protection circuit in the BCU. Its primary function is
to put a maximum limit on the time (110 ms) that two
power sources of different types are in parallel. SUSP
starts when the XPC closes. It resets when the APB
opens. If the APB does not open in the time limit, the
SUSP opens the APB and the XPC. This removes the two
sources from the sync bus. After a SUSP trip you must
connect the necessary power source again.
ELECT PWR -- EXT POWER - NBPT - ADJACENT APU
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ELECT PWR - EXT POWER - NBPT - ADJACENT APU
6
SUSP TRIP
SUSP RESET
APBTRIP
TRIP
TRIPSPEED
POWER ON ADJ
V/F/PHASE
BCU
XPC CLOSEDXPC
EXT PWR
POWER ON
RESET
TRIP
ADJ APB
EXT PWR
SUSP XPC CLOSED
TD
SYNCH BUS
CLOSED
CLOSECOMMAND
COMMANDTO APUC
SYNCH BUS
COMPARATOR
110 MS LOGIC
- 53 -
if the XPC fails to close in 6 second,theTD outlet a trip discrete to trip APB.AfterAPB triping,the XPC closes.
if APB fails to open in 110 ms after XPCclosing,the SUSP output a trip discrete to tripXPC and APB simultaneously.
the SUSP provides a tiime-limit for maximumperiod different type sources are in parallel.
for increasing or decreasing the
speed of APU .In order tosynchronize the voltage,frequencyand phase .
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General
If the synch bus has power from an IDG and you connect
power from an adjacent external source, the no break
power transfer (NBPT) logic momentarily connects the
two sources in parallel. The adjacent GCB then opens to
remove the IDG power from the synch bus. If there are
two IDGs in operation, they operate the same.
Operation
Before the NBPT logic in the BCU connects the two power
sources in parallel, a comparator circuit compares
voltage, frequency and phase between the synch bus
power and the APU power. Differences must be less than:
- Voltage, 10 volts
- Frequency, 3 Hz
- Phase, 20 degrees
The BCU monitors external power C phase frequency and
sends this data as a digital reference frequency to the
GCU. The GCU increases or decreases IDG speed until the
difference between the frequency of IDG and external
power is in limits. When the voltage, frequency and
phase are in limits, the XPC closes. The BCU senses the
position of the XPC through a set of auxiliary contacts
in the XPC. After the XPC closes, the BCU sends an open
signal on the digital data bus to the GCU. The GCUopens the GCB if the BTB is closed. If the BTB is open,
the GCB stays closed. The power on the synch bus now
comes from the external source.
The BCU has a 6 second time delay that becomes active
when the close command signal goes to the BCU. This
time delay causes the BCU to send a trip signal to the
GCU over the digital data bus if voltage, frequency and
phase are not in limits after 6 seconds. After this
time delay the GCU opens the GCB and removes power from
the synch bus. The XPC then closes. This causes a
momentary break in power. When the XPC closes, the 6
second time delay resets.
Sustained Unlike Source Protection
Sustained unlike source protection (SUSP) is a
protective circuit in the BCU. Its primary function is
to put a maximum limit on the time (110 ms) that two
power sources of different types are in parallel. SUSP
starts when the XPC closes. It resets when IDG power is
no longer on the adjacent synch bus. If the GCB does
not open in the time limit, the SUSP sends a trip
signal over the digital data bus to the GCU. The GCU
opens the BTB on IDGs where the GCB did not open.
ELECT PWR -- EXT POWER - NBPT - ADJACENT IDG
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ELECT PWR - EXT POWER - NBPT - ADJACENT IDG
6
NOTE: TYPICAL OF BCU AND 2 ADJACENT IDG CHANNELS
POWER ON ADJ
V/F/PHASE
GCU
BCU
BTBGCB
TRIPTRIP
BTBGCB
TRIP
SUSP TRIP
XPC CLOSEDXPC
CLOSE XPC
EXT PWR C PHASE
EXT PWR
POWER ON
RESET
TRIP
SUSP RESET WITH NO IDG
ADJ BTB AND
EXT PWR
SUSP XPC CLOSED
POWER ON ADJ SYNCH BUS
SYNCH BUS
GCB CLOSED
CLOSECOMMAND
REF FREQ TO GCU(S)
SYNCH BUS
COMPARATOR
TD LOGIC LOGIC
LOGIC110 MS
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for increasing or decreasing theIDG speed .In order to
synchronize thevoltage,frequency and phase .
trip the BTB where theGCB didn't open.
trip the GCB where
the BTB is closed.
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General
If the synch bus has power from an APU generator and
you connect power from an opposite external source, the
no break power transfer (NBPT) logic momentarily
connects the two sources in parallel. If the two
external power sources are available, the SSB opens. If
only one external power is available, the opposite APB
opens.
Operation
Before the NBPT logic in the BCU connects the two power
sources in parallel, a comparator circuit compares
voltage, frequency and phase between the synch bus
power and the external power. Differences must be less
than:
- Voltage, 10 volts
- Frequency, 3 Hz
- Phase, 20 degrees
If there is a frequency difference of more than 3 Hz,
the BCU gives a speed command to the APU controller
(APUC). This increases or decreases the APU speed. All
speed signals that go to the APUC go through BCU 1.
When the voltage, frequency and phase are in limits,
the XPC closes. The BCU senses the position of the XPC
through a set of auxiliary contacts in the XPC. After
the XPC closes, the BCU opens the SSB or the APB. If the
two external power sources are available the SSB opens.
If only one external power source is available, the
opposite APB opens.
The BCU has a 6 second time delay that becomes active
when the close command signal goes to the BCU. This
time delay causes the SSB or APB to open if voltage,
frequency and phase are not in limits after 6 seconds.
This removes power from the synch bus, and the XPC
closes. This causes a momentary break in power. When
the XPC closes, the 6 second time delay resets.
Sustained Unlike Source Protection
Sustained unlike source protection (SUSP) is a
protection circuit in the BCU. Its primary function is
to put a maximum limit on the time (110 ms) that two
power sources of different types are in parallel. SUSP
starts when the XPC closes. It resets when APU power is
no longer on the adjacent synch bus. If the APB (one
external source available) or SSB (two external sources
available) does not open in the time limit, the SUSP
opens the XPC and the APB. This removes the two sources
from the sync bus. After a SUSP trip you must connect
the necessary power source again.
ELECT PWR -- EXT POWER - NBPT - OPPOSITE APU
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if the two external power sources and the two APU powersources are used, After pressing in the external powerswitch,the adjacent APB and SSB open. After pressing inthe opposite external power switch,the SSB stays opened
and opposite APB opens.
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ELECT PWR - EXT POWER - NBPT - OPPOSITE APU
6TRIP
SSB
SUSP
BOTH EXT
APB
XPC CLOSED
XPC
TRIP
RESET
V/F/PHASE
SPEED
BCU
EXT PWR
POWER ONTRIP
CLOSE XPC
SUSP
OPP APB
SSB
TRIP
EXT PWR
POWER ON ADJ
SUSP RESET WITH NO APU
XPC CLOSED
TD
SYNCH BUS
CLOSED
CLOSED
CLOSECOMMAND
COMMANDTO APUC
SYNCH BUS
COMPARATOR
POWER ON ADJ SYNCH BUS
PWR AVAILABLE
110 MS
LOGIC
TRIP
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General
If the synch bus has power from an IDG and you connectpower from an opposite external power source, the no
break power transfer (NBPT) logic momentarily connects
the two sources in parallel. If the two external power
sources are available, the SSB opens. If only one
external power source is available, the opposite GCB
opens. If there are two IDGs in operation, they operate
the same.
Operation
Before the NBPT logic in the BCU connects the two power
sources in parallel, a comparator circuit compares
voltage, frequency and phase between the synch bus
power and the external power. Differences must be less
than:
- Voltage, 10 volts
- Frequency, 3 Hz
- Phase, 20 degrees
The BCU monitors external power C phase frequency and
sends this data as a digital reference frequency to the
GCU. The GCU increases or decreases IDG speed until the
difference between the frequency of IDG and APU power C
phase power is in limits.
When the voltage, frequency and phase are in limits,
the XPC closes. The BCU senses the position of the XPC
through a set of auxiliary contacts in the XPC. After
the XPC closes, the BCU then finds if opposite external
power is available. If the opposite external power is
available, then the SSB opens. If the opposite external
power is not available, then the GCB opens.
The BCU has a 6 second time delay that becomes active
when the close command signal goes to the BCU. This
time delay causes the SSB or GCB to open if voltage,
frequency and phase are not in limits after 6 seconds.
After this time delay the SSB opens if two external
power sources are available, or the GCB opens if only
one external power source is available. This removes
power from the synch bus, and the XPC closes. This
causes a momentary break in power. When the XPC closes,
the 6 second time delay resets.
Sustained Unlike Source Protection
Sustained unlike source protection (SUSP) is a
protection circuit in the BCU. Its primary function is
to put a maximum limit on the time (110 ms) that two
power sources of different types are in parallel. SUSP
starts when the XPC closes. It resets when IDG power is
no longer on the adjacent synch bus. If the SSB or GCB
does not open in the time limit, the SUSP sends a trip
signal over the digital data bus to the GCU. The GCU
opens the BTB on IDGs where the GCB did not open.
ELECT PWR EXT POWER NBPT OPPOSITE IDG
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ELECT PWR - EXT POWER - NBPT - OPPOSITE IDG
6
XPC CLOSED
EXT PWR
SSB
XPC CLOSED
SUSP TRIP
POWER ON ADJ
OPP BTB AND
TRIP
RESET
POWER ON
EXT PWR
BCU
V/F/PHASE
EXT PWR C PHASE
CLOSE
BTBGCB
TRIPTRIP
GCU
OPEN
SUSP
OPP EXT
SUSP RESET WITH
SYNCH BUS
GCB CLOSED
CLOSED
CLOSECOMMAND
REF FREQ TO GCU(S)
SYNCH BUS
NO IDG POWER ONADJ SYNCH BUS
PWR AVAIL
LOGIC
COMPARATOR
TD
XPC SSB
LOGIC LOGIC
110 MS
XPC SSB GCB BTB
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signal over the digital data bus to the GCU. The GCU
opens the BTB on IDGs where the GCB did not open.
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CLOSEOPENSSB
SSBOPENED
XPCCLOSEDXPC
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ELECT PWR - EXT POWER - NBPT - ADJACENT AND OPPOSITE IDG
6
SUSP
RESET
SUSP RESET WITH
BCU
EXT PWR
ANY OPP
ANY ADJ
OPP EXTTO ALL
TO ADJ GCU(S)
TO ALL GCU(S)
OPP EXT
EXT PWR C PHASE
EXT PWR
POWER ON
V/F/PHASE TRIP
TRIP
XPC
GCB ANDBTB CLOSED
GCB ANDBTB CLOSED
CLOSEDCOMMAND
PWR AVAIL
COMPARATOR
SYNCH BUS
NO IDG POWER ONADJ SYNCH BUS
110 MS
CLOSEDLOGIC
PWR AVAILFOUR GCU(S)
TO TRIPGCB(S)
TO TRIP GCB(S)
FOR BTB SUSP TRIPREF FREQ TO GCU(S)
TD
SSB XPC
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General
If the synch bus has power from the opposite externalpower source and you connect power from the adjacent
external power source, the system does not use the no
break power transfer (NBPT) logic. When the BCU gets
the external power close command, it opens the SSB.
This causes a momentary break in power. When the BCU
senses that the SSB is open, it closes the XPC. The BCU
monitors SSB position through the auxiliary contacts in
the SSB.
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ELECT PWR - EXT POWER - NBPT - OPPOSITE EXTERNAL POWER
BCU
TRIP
CLOSE
SSB OPEN
CLOSE XPC
OPPOSITE XPC
POWER ON ADJ
SSB CLOSED
EXTERNAL POWER
SYNCH BUS
CLOSED
CLOSE COMMAND
ADJ XPC
SSB
XPC
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ELECT PWR -- AC GENERATION - APU POWER SOURCES
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General
The airplane can use the two APU power sources while onthe ground.
The two APU generators on the APU load gearbox supply
400 Hz, 3 phase, 115 volts ac and can supply a maximum
of 90 kva. The generator feeders are AWG 0 copper in
the APU compartment and have a splice to AWG 00
aluminum forward of the APU firewall. The AWG 00
aluminum feeders go to the main equipment center. They
connect at their related auxiliary power breakers (APB)in P714 and P715.
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ELECT PWR - AC GENERATION - APU POWER SOURCES
APU DRIVEN
APU GENERATOR
P714
P715
GENERATORS
FEEDERS
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General
ELECT PWR -- AC GENERATION - APU POWER COMPONENTS
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General
The APU power system components are in the MEC, flightdeck and in the APU compartment in the tail. The APU
power system includes:
- APU generators (2)
- Generator manual reset panel
- Electrical system control panel
- Current transformers (5)
- Auxiliary power breakers (2)
- Bus control units (2)- Auxiliary generator control units (2).
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747 TRAINING MANUAL
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GEN FIELD MAN RESET
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ELECT PWR - AC GENERATION - APU POWER COMPONENTS
GENERATOR MANUAL
QAD RINGS
AUXILIARY GENERATOR
ELECTRICAL SYSTEM
AUXILIARY POWER
BUS CONTROL UNITS
CURRENT
APU GENERATORS
ww
ww
w
w
21
w
FIELDOFF
FIELD
OFFFIELD
OFFFIELD
OFF OFFFIELD
OPEN
BREAKERSPLIT SYSTEM
APU
OFFFIELD
RESET PANEL (P461)
CONTROL UNITS
BREAKERS
TRANSFORMERS
CONTROL PANEL (P5)
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747 TRAINING MANUAL
General close its related auxiliary power breaker (APB). The ON
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General
Two APU generators supply three-phase, 400 Hz ac powerto the airplane. Before the power connects to the
airplane systems, two auxiliary generator control units
(AGCU) monitor the power to make sure that it is at the
correct voltage and frequency. When the AGCUs find that
the power is good, they send a signal to the BCUs to
turn on the two APU generator AVAIL lights on the
electrical system control panel in the flight deck.
Ground Handling Bus
When BCU 1 turns on the APU generator AVAIL light, it
also energizes the ground handling relay (GHR) to give
power to the ground handling bus (GHB). Cargo loading,
cleaning outlets and fuel are some of the systems on
the GHB.
Ground Service Bus
The ground service switch is at the flight attendant
panel at door 2L. When you push this switch, BCU 1
energizes the ground service relays to give APU power
to the ground service bus (GSB). APU power does not
connect to the GSB if ac bus 1 has power or external
power 1 is available.
APU Power
The two momentary switches, APU GEN 1 and APU GEN 2,
are on the electrical system control panel. When you
push APU GEN 1, BCU 1 sends a close signal to AGCU 1 to
close its related auxiliary power breaker (APB). The ON
light in the switch comes on and the AVAIL light goes
off. BCU 2 closes the SSB at this time if no other poweris on the synch bus. APU GEN 1 now supplies power to the
airplane. When you push APU GEN 2, BCU 2 opens the SSB
then sends a close signal to AGCU 2 to close its
related APB. The ON light in the switch comes on and
the AVAIL light goes off. APU GEN 1 now supplies power
to the left side of the synch bus and APU GEN 2 supplies
power to the right.
If you push the APU GEN switch with the APB closed, theBCU sends an open command to the AGCU and APB. The AGCU
then also sends an open command to the APB. This makes
sure that the APB opens.
The BCU or AGCU can open the APB for electrical
malfunctions.
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747 TRAINING MANUAL
STANDBY POWER
OFFAUTO
BAT
L - UTILITY - R
OFF
ONw
aOFF
ONw
a
APU
ONOFF START
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FAULT TRIP/FAULT TRIP/
GROUND
APU GEN 1 APU GEN 2
AUX PWR
GROUND
GHB
GSB
AGCUSSB
TRIP
TRIP
AGCU
CLOSESSB
APBAPB
wAUTO BUSw
AUTOw
AUTOw
AUTO
EXT PWR 1 APU GEN 1
ON
BATTERY
w w
AVAIL
OFF
ONw
aON
w
AVAIL
ON
w w
AVAIL
ON
w
AVAIL
APU GEN 2 EXT PWR 2
APBAPB
FAULT TRIP
BCU 1 BCU 2
FAULT TRIP
SYNCH
OPEN/CLOSE
OPEN/CLOSE
OPEN/CLOSE
OPEN/CLOSE
OPEN/CLOSE
OK
OPEN
SERVICE
OPEN/CLOSE
OPEN
CLOSE
BUSSYNCHBUS
SELECTEDSERVICE
ELECT PWR - AC GENERATION - APU POWER GENERAL OPERATION
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747 TRAINING MANUAL
General dc goes to the field of the main generator. The main
ELECT PWR -- AC PWR GEN AND PROTECTION - APU GENERATORS
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There are two inter-changeable generators on theforward face of the APU load gearbox. Each generator
supplies the airplane on the ground with ac power up to
90 kva. The generator contains three generators in one:
- Permanent magnet generator (PMG)
- Exciter generator
- Main generator.
Characteristics
Bendix makes the APU generators. The generators have
these properties:
- Weight, 68 lbs
- Rated voltage (line-to-neutral), 120 volts ac
- Rated voltage (line-to-line), 208 volts ac
- Phase, 3
- Frequency, 375-425 Hz- Rated speed, 7600-8400 rpm
- Rated load (continuous), 90 kva
Operation
There are six permanent magnets attached to the rotor
shaft. These supply three phase, 80 volts ac (at zero
load). The AGCU changes the voltage to dc, controls it,
and sends it back to the generator exciter field. Thearmature of the exciter generator supplies three phase
ac to the field of the main generator. Three diodes
turn with the field and change the voltage to dc. This
generator supplies three phase, 400 Hz, 120/208 volts
ac.
There is a current transformer on each phase of the
ground side of the main generator leads. These current
transformers monitor for differential protection and
total current output of the generator.
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CURRENT
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ELECT PWR - AC PWR GEN AND PROTECTION - APU GENERATORS
3 PHASE
3 PHASE
DIFFERENTIAL
DC
MAIN
EXCITERPMG
AGCU
QAD RING
TERMINAL
CURRENTTRANSFORMERASSEMBLY
BLOCK
400 HZPROTECTIONCURRENTTRANSFORMERS
GENERATOR
GENERATOR
80V AC
115/200V
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747 TRAINING MANUAL
General
ELECT PWR -- AC PWR GEN AND PROTECTION - APU GENERATOR INSTALLATION
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Each APU generator attaches to the APU load gearboxwith a quick attach detach (QAD) ring or clamp. An
adapter plate attaches to the gearbox pad with machine
screws. The QAD ring pulls the generator toward the
plate as you tighten the ring. This is because of the
slope of the surface on the ring and adapter plate.
Before you install the generator, you must put on a new
lubricated O-ring. Be careful to make sure that the
index pin correctly engages with the generator indexpin hole before you torque the ring. It is possible to
install the QAD ring and not have the index pin in the
hole.
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ELECT PWR - AC PWR GEN AND PROTECTION - APU GENERATOR INSTALLATION
1
3
2
N
QAD RING
QUICK
INDEX PIN
APU O-RING
TERMINAL
ADAPTER
APU LOAD
GENERATOR
PLATE
GEARBOX
ATTACH-DETACHMOUNTING DEVICE
APU LOAD GEAR-BOXBLOCK
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747 TRAINING MANUAL
General WARNING: DO NOT DISCONNECT THE TRANSFORMER OUTPUT
CONNECTION WITH THE FEEDER LINES POWERED THE
ELECT PWR -- AUTOMATIC CONTROL - APU POWER CURRENT TRANSFORMERS
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The current transformers (CT) related to APU power arein P714 and in P715. The CTs have these functions:
- Metering (data sent to the BCUs for percent load
indications on EICAS, Sundstrand CTs)
- Load reduction (data sent to the BCUs for load
reduction circuits, Sundstrand CTs)
- Differential fault protection (data used by the
AGCUs, Bendix CTs)
In addition each APU generator has one CT in the
generator for differential fault protection.
Characteristics
There are two different types of CTs related to the APU
power system. Sundstrand makes one and Bendix makes the
other. Each transformer assembly has a toroidal shaped
core with secondary winding wires that connect to anoutput connector. Main ac feeder lines goes through the
large holes in the transformer and are the primary
winding for each transformer core. The turns ratio of
all of the windings of the Sundstrand transformers is
1000 to 1. The Bendix CTs are 500 to 1. If the primary
winding (feeder line) is 115 volts ac, secondary
winding voltage is as much as 115,000 volts with the
connector off (no load). Usually secondary voltages are
very low because the secondary loads have a lowresistance.
CONNECTION WITH THE FEEDER LINES POWERED. THE
POTENTIALLY HIGH VOLTAGES COULD DAMAGE THETRANSFORMER OR RESULT IN INJURY TO PERSONNEL.
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747 TRAINING MANUAL
General
ELECT PWR -- AC PWR GEN AND PROTECTION - AUXILIARY POWER BREAKERS
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There are two auxiliary power breakers (APB) thatconnect APU power with the airplane synch bus. They are
in the MEC in P714 and P715. The breakers are a
magnetic latch type and can operate at 275 amperes
continuous or 350 amperes for 15 seconds. Each can open
at up to 5000 amperes. The breakers must get 28 volts
dc to close or to open. The control signals to the APBs
come from the BCUs and AGCUs. The APBs are inter-
changeable with all of the other generator circuit
breakers and bus tie breakers.
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ELECT PWR - AC PWR GEN AND PROTECTION - AUXILIARY POWER BREAKERS
COMMON
28V DCTRIP
CLOSE
28V DCCLOSE
P715
P714
(PERMANENT MAGNET)
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747 TRAINING MANUAL
General
ELECT PWR -- AC PWR GEN AND PROTECTION - AUXILIARY GENERATOR CONTROL UNITS
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There are two auxiliary generator control units (AGCU)in the MEC on the E1 and E2 equipment racks. They have
functions as voltage regulators and interface units
between the BCUs, APU generators and APBs.
Control Functions
Each AGCU has these control functions:
- Generator field control and indication- APB control
- APU generator power ready
- Auto parallel
- Anti-cycle.
Protective Functions
Each AGCU has these protective functions:
- Underspeed
- Overvoltage
- Undervoltage
- Differential fault
- Overcurrent.
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ELECT PWR - AC PWR GEN AND PROTECTION - AUXILIARY GENERATOR CONTROL UNITS
- CONTROL- PROTECTION
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747 TRAINING MANUAL
General you operate the field switch again the GCR opens. A GCR
open signal can occur because of:
ELECT PWR -- AC PWR GEN AND PROTECTION - AGCU OPERATION
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The two auxiliary generator control units (AGCU) in theMEC have functions as voltage regulators, generator
controllers and interface units between the BCUs, APU
generators and APBs.
Voltage Regulation
The PMG supplies three-phase 80-volt ac to the AGCU. A
TRU changes this voltage to dc for use by internal
control circuits and the APB. PMG voltage goes to thegenerator control relay (GCR). With the GCR closed
three-phase ac goes to a field current regulator
circuit which changes it to dc pulses. This dc goes to
the exciter generator which supplies the main generator
field. The main generator supplies the three-phase, 400
Hz, 115 volts ac. A circuit in the AGCU senses the
voltage and controls the field current regulator to
keep the correct voltage output of the generator.
GCR Control
The GCR in the AGCU is a latch type relay with an open
and a close coil. Power from the generator output goes
through the GCR to the field current regulator. The
relay is open by internal protective circuits, the
flight deck fire switch and the BCU. You momentarily
operate the APU generator field switch on the generator
manual reset panel to close the GCR. Each operationchanges the position of the GCR. The trip/close logic
in the BCU sends a close signal to the AGCU, and if
there is no malfunction, the AGCU closes the GCR. If
- An under voltage not caused by under speed or GCR
open
- An over voltage
- Fire switch operation
- APU generator bearing malfunctions: 5-minute time
delay (Reset with field switch)
- APU generator field switch operation.
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747 TRAINING MANUAL
TO APBT1
T2
T3
VOLTAGESENSING
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ELECT PWR - AC PWR GEN AND PROTECTION - AGCU OPERATION
5 MIN
GENERATOR MANUAL
APU GEN
PMGGCR
FIELD
CLOSE
TRU
AGCU
TRIP
UNDER SPEED
GCR TRIPPED
UNDER VOLTAGE
DIFF FAULT
FIRE SWITCH
OVER VOLTAGE
POWER
EXCITER
TRIP/CLOSE
BCU
MAIN
PRIMARY
AUX
S
CLOSE
TRIP
R
1
FIELDOFF W
NO. 1
BEARINGFAIL
BAT BUS
CONTACTS
RESET PANEL (P461)
LOGIC
CURRENTREGULATOR
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General
ELECT PWR -- AC GENERATION - APU GENERATOR AVAILABLE LIGHT
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The APU generator AVAIL lights are on the electricalsystem control panel in the flight deck. The two
lights, one for APU GEN 1 and one for APU GEN 2, show
when APU power is in limits for frequency and voltage
and the APB is open.
Operation
The AGCUs give a power ready signal when:
- APU speed is above 95 percent
- Voltage is 104 to 130 volts ac
- There are no trip signals to the GCR.
After the BCUs get the power ready signal, the power
available driver turns on the APU generator AVAIL
lights. R230 in P414 inhibits the lights when the
airplane is in flight.
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747 TRAINING MANUAL
STANDBY POWER
OFFAUTO
BAT
L - UTILITY - R
ONw
ONw
APU
ONOFF START
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ELECT PWR - AC GENERATION - APU GENERATOR AVAILABLE LIGHT
APU
VOLT
VOLT
GCR NOT
AGCU
APU
POWER AVAIL
GND
AIR
ELECTRICAL SYSTEM
ON
wIAVA
APU GEN
R230 AIR/
BCU
EXT PWR 1 APU GEN 1
ON
OFF
BATTERY
a
w w
AVAIL
OFFa
OFF
ONw
aON
w
AVAIL
ON
w
AVAIL
ON
w
AVAIL
APU GEN 2 EXT PWR 2
w
APB
SPEED>95%
>104+/-1.5
<130+/-3
TRIPPEDCLOSED
GND SAFETY(P414)
CONTROL PANEL (P5)
DRIVER
POWERREADY
w
w
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747 TRAINING MANUAL
General When the APB closes, auxiliary contacts in the APB turn
on the APU GEN ON light. The light does not show when
ELECT PWR -- AC GENERATION - AUXILIARY POWER BREAKER CONTROL
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Two auxiliary power breakers (APB) connect APUgenerator power to the airplane synch bus. They are in
P714 and P715 in the MEC. These components have a
relation to the control of the APBs:
- AGCUs (2), BCUs (2)
- APU generator switches (2), APB close protection
relays (2).
APB Close
Each time you push the momentary APU generator switch,
it causes an APB close or APB open command. The
trip/close logic ignores new switch commands until it
completes the last command (APB open or closed) or a
4.5 second time delay. The BCU gives an APB close
command if all of these conditions are true:
- trip/close logic gives a close command- opposite APB is open or closed for 3.5 seconds
- no air mode inhibit with any GCB closed
- power ready signal from the AGCU.
The close APB signal goes to the no break power
transfer and auto parallel logic. The BCU then closes
the APB close protection relay and sends an APB close
signal to the AGCU. When the AGCU finds that the
generator can parallel or the bus is dead, it closesthe APB.
the airplane is in flight.
APB Open
The BCU or AGCU can send signals to open the APB. The
AGCU opens the APB for:
- Underspeed
- GCR trip signal.
The BCU opens the APB for:
- Synch bus faults
- CPU failure (BCU internal failure)
- Sustained unlike source protection
- Trip logic (power transfer complete, last source
on, bearing failure)
- No APU power ready signal.
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747 TRAINING MANUAL
AIR
GNDAPU GEN 1
ON
AVA
I
APB CLOSED
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ELECT PWR - AC GENERATION - AUXILIARY POWER BREAKER CONTROL
AIRMODE
T
RS
C
AIRIL w w
ELECT SYSTEM
TRIP/CLOSE
GCR TRIP
AGCU 1
CLOSE
R301 APB CLOSE
APB
TRIP
POWER
NOTE: SYSTEM 1 SHOWN,
TRIP
R229 AIR
UNDER SPEED
DEAD BUS
V/F/PHASE OK
CPU FAIL
TRIP LOGIC
SYNCH BUS FAULTAPU POWER READY
SUSP
NBPT
BCU 1
ANY GCB
CLOSEOPP APB CLSD 3.5 SEC
CONT PANEL (P5)
LOGIC
(4.5 SEC TD)
CLOSED
READY
APB
GROUND SAFETY(P414)
PROTECTION (P714)
SYSTEM 2 SIMILAR
APB
ANDAUTO PAR
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747 TRAINING MANUAL
General
The electrical system can do no break power transfers
ELECT PWR -- AC GENERATION - APU POWER NO BREAK POWER TRANSFER
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The electrical system can do no break power transfers(NBPT). A NBPT is a change of an ac power source
without the momentary break in power. To do this power
sources momentarily operate in parallel. All power
transfers between engine generators, APU generators and
external power are no break power transfers. The only
time power breaks occur are when two external power
sources or two APU generators connect to an airplane
that has no other electrical sources connected. If all
buses get power from one external power source and youconnect the second external source, the SSB opens
before the second XPC closes. This causes a momentary
break in power. If all buses get power from an APU
generator and you connect the second APU generator,
there is also a momentary break in power. The two BCUs
have the primary control for NBPT.
Power Configurations
Before you connect APU power to the airplane, the NBPT
logic in the BCUs finds the power configuration of the
synch bus. The seven possible power configurations of
the synch bus are:
- Dead (no power)
- Adjacent external power
- Adjacent IDG
- Opposite external power with SSB closed- Opposite IDG with SSB closed
- Adjacent and opposite IDG
- Opposite APU generator with SSB closed.
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747 TRAINING MANUAL
DEAD
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ELECT PWR - AC GENERATION - APU POWER NO BREAK POWER TRANSFER
OPPOSITE
SSB
NO BREAK POWER
POWER INTERRUPT
ADJACENT IDG
OPPOSITE IDG
ADJACENT
OPPOSITE
APU
SYNCH BUS POWER
ADJ AND OPP
POWER
CLOSED
EXTERNAL POWER
EXTERNAL POWER
IDG
APU GENERATOR
TRANSFER
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747 TRAINING MANUAL
General
When the no break power transfer logic in BCU 1 sensesl APB d ith th h b
ELECT PWR -- AC GENERATION - APU POWER NBPT - DEAD SYNCH BUS
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When the no break power transfer logic in BCU 1 sensesa close APB command with no power on the synch bus, a
signal goes to the APB close protection relay, to the
AGCU and to BCU 2 to close the SSB. The AGCU does a
check to find that the adjacent synch bus does not have
power then closes the APB. There is now APU power on
the left and right synch bus.
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ELECT PWR - AC GENERATION - APU POWER NBPT - DEAD SYNCH BUS
APU PWR 1 APB
SSBSSB CLOSE
BCU 2
POWER ON ADJ
BCU 1 (E1-2)
NO BREAK POWER
NO POWER ON ADJ
AGCU
R301 APB CLOSE
LOGIC
CLOSECOMMAND
SYNCH BUSTRANSFER LOGIC
PROTECTION(P714)
SYNCH BUS
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747 TRAINING MANUAL
General
If the synch bus has power from an external power
source and you connect power from an adjacent APU
The BCU has a 6 second time delay that becomes active
when the close command signal goes to the BCU. This
time delay causes the XPC to open if voltage, frequency
and phase are not in limits after 6 seconds After this
ELECT PWR -- AC GENERATION - APU POWER NBPT - ADJACENT EXERNAL POWER
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source and you connect power from an adjacent APU
source, the no break power transfer (NBPT) logic
momentarily connects the two sources in parallel. The
adjacent XPC then opens to remove the external power
from the synch bus.
Operation
Before the NBPT logic in the BCU connects the two powersources in parallel, a comparator circuit compares
voltage, frequency and phase between the synch bus
power and the APU power. Differences must be less than:
- Voltage, 10 volts
- Frequency, 3 Hz
- Phase, 20 degrees
If there is a frequency difference of more than 3 Hz,the BCU gives a speed command to the APU controller
(APUC). This increases or decreases the APU speed. At
the same time the APU close protection relay energizes
and a close APB signal goes to the AGCU. The AGCU
comparator monitors the voltage, frequency and phase
and closes the APB when they are in limits. The BCU
senses the position of the APB through a set of
auxiliary contacts in the APB. After the APB closes,
the BCU removes power from the XPC and it opens. Thepower on the synch bus now comes from the APU source.
and phase are not in limits after 6 seconds. After this
time delay the XPC opens and removes power from the
synch bus, and the APB closes. This causes a momentary
break in power. When the APB closes, the 6 second time
delay resets.
Sustained Unlike Source Protection
Sustained unlike source protection (SUSP) is aprotection circuit in the BCU. Its primary function is
to put a maximum limit on the time (110 ms) that two
power sources of different types are in parallel. SUSP
starts when the APB closes. It resets when the XPC
opens. If the XPC does not open in the time limit, the
SUSP opens the XPC and the APB. This removes the two
sources from the sync bus. After a SUSP trip you must
connect the necessary power source again.
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747 TRAINING MANUAL
CLOSE APB
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ELECT PWR - AC GENERATION - APU POWER NBPT - ADJACENT EXERNAL POWER
6
SUSP
SUSP
XPC
APB
ADJ XPC
POWER ON
SUSP TRIP
TRIP
BCU
APB
APB CLOSED
28V
AGCU
V/F/PHASE
APU PWR
APB
SPEED COMMAND
RESET
TRIP
APB/SPEED
POWER ON ADJ CLOSE
APU PWR
APU PWR
POWER ONSYNCH BUS
COMPARATOR
SYNCH BUS
CLOSED
CLOSECOMMAND
TO APUC
SYNCH BUS
TD
CONTROL
APB
CLOSEPROTECTIONRELAY
CLOSED
LOGIC
110 MS
RESET
DC
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747 TRAINING MANUAL
General
If the synch bus has power from an IDG and you connect
power from an adjacent APU source, the no break power
the GCU. The GCU opens the GCB if the BTB is closed. If
the BTB is open, the GCB stays closed. The power on the
synch bus now comes from the APU source.
ELECT PWR -- AC GENERATION - APU POWER NBPT - ADJACENT IDG
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p j , p
transfer (NBPT) logic momentarily connects the two
sources in parallel. The adjacent GCB then opens to
remove the IDG power from the synch bus. If there are
two IDGs in operation, they operate the same.
Operation
Before the NBPT logic in the BCU connects the two powersources in parallel, a comparator circuit compares
voltage, frequency and phase between the synch bus
power and the APU power. Differences must be less than:
- Voltage, 10 volts
- Frequency, 3 Hz
- Phase, 20 degrees
The BCU monitors APU power C phase frequency and sendsthis data as a digital reference frequency to the GCU.
The GCU increases or decreases IDG speed until the
difference between the frequency of IDG and APU power C
phase power is in limits.
The BCU energizes the APB close protection relay and
sends a close APB signal to the AGCU. The AGCU
comparator monitors the voltage, frequency and phase
and closes the APB when they are in limits. The BCUsenses the position of the APB through a set of
auxiliary contacts in the APB. After the APB closes,
the BCU sends a trip signal on the digital data bus to
The BCU has a 6 second time delay that becomes active
when the close command signal goes to the BCU. This
time delay causes the BCU to send a trip signal to the
GCU over the digital data bus if voltage, frequency and
phase are not in limits after 6 seconds. After this
time delay the GCU opens the GCB and removes power from
the synch bus. The APB then closes. This causes a
momentary break in power. When the APB closes, the 6second time delay resets.
Sustained Unlike Source Protection
Sustained unlike source protection (SUSP) is a
protective circuit in the BCU. Its primary function is
to put a maximum limit on the time (110 ms) that two
power sources of different types are in parallel. SUSP
starts when the APB closes. It resets when IDG power isno longer on the adjacent synch bus. If the GCB does
not open in the time limit, the SUSP sends a trip
signal over the digital data bus to the GCU. The GCU
opens the BTB on IDGs where the GCB did not open.
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747 TRAINING MANUAL
APB
V/F/PHASE
CLOSE APB
R301 APB
APB SSB
OPEN
APU PWR
CLOSED SSB
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ELECT PWR - AC GENERATION - APU POWER NBPT - OPPOSITE IDG
6
SUSP
CLOSE
GCB BTB
BTB
TRIP
POWER ON ADJ
APU PWR
V/F/PHASE
APU POWER
AGCU
RESET
TRIP
OPPOSITE BTB
APU PWR
SUSP RESET
BCU
APB/FREQ
GCB
TRIP
GCU
APB CLOSED
OPP APU
POWER ON
SSB CLOSED
SUSP
TRIP
SYNCH BUSCOMPARATOR
CLOSEPROTECTION(P714)
SYNCH BUS
AND GCB CLOSED
CLOSECOMMAND
C PHASE REF FREQTO GCU(S)
TD
CONTROL
APBLOGIC
110 MS
WITH NO IDGPOWER ON ADJSYNCH BUS
TRIP
PWR AVAIL
LOGIC LOGIC
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747 TRAINING MANUAL
ELECT PWR -- AC GENERATION - APU POWER NBPT - ADJACENT AND OPPOSITE IDG
starts when the APB closes. It resets when IDG power is
no longer on the adjacent synch bus. If the GCB does
not open in the time limit, the SUSP sends a trip
signal over the digital data bus to the GCU. The GCUopens the BTB on IDGs where the GCB did not open.
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p p
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747 TRAINING MANUAL
SSB
V/F/PHASE
AGCU
APU PWR
POWER ON SYNCH BUS
APB
APB
COMPARATOR
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ELECT PWR - AC GENERATION - APU POWER NBPT - ADJACENT AND OPPOSITE IDG
6
RESET
APB/FREQ
TO ALL
TO ALL GCU(S)APU POWER C PHASE
OPP APU
SSBOPEN
TO ADJ GCU(S)
OPP APU
ONE OR TWO
ONE OR TWO
APU PWR
APU PWR
SUSP RESETSUSP
APB CLOSED
APB
CLOSE
BCU
CPR
TRIP
TRIP
SSB OPENED
ADJ GCBS ANDBTB CLOSED
OPP GCBS ANDBTB CLOSED
CLOSECOMMAND
PWR AVAIL
APB
CONTROL
WITH NO IDGPOWER ONADJ SYNCH BUS
110 MS
LOGIC
CLOSED
TO TRIP GCB(S)
TD
PWR AVAILFOUR GCU(S)TO TRIPGCB(S)
REF FREQ TO GCU(S) FOR BTB SUSP TRIP
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747 TRAINING MANUAL
General
The airplane has four integrated drive generators
(IDG). Each IDG is a combined generator and constantspeed drive (CSD). The generator part gives 3 phase,
400 Hz 115 volts ac at 90 kva The CSD part keeps the
ELECT PWR -- GEN DRIVE - INTRODUCTION
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400 Hz, 115 volts ac at 90 kva. The CSD part keeps the
generator at a constant 12,000 rpm during usual
operation. This makes sure that the generator supplies
a constant 400 Hz.
The IDG power goes to the airplane through generator
feeders. The feeders have a short length of AWG 0
copper spliced to AWG 00 aluminum. The length of coppergoes in the engine compartment and connects to the
aluminum at the copper-aluminum splice in the strut.
The part of the feeders from the IDG to the bottom of
the strut has quick disconnect clamps to aid in engine
removal. The aluminum feeders go along the wing leading
edge and connect at their related generator circuit
breakers in the generator power centers.
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ELECT PWR - GEN DRIVE - INTRODUCTION
INTEGRATED
GENERATOR
MEC
P615
P614P514
IDG 4
IDG 1IDG 2 DRIVE
GENERATOR
FEEDER
P515IDG 3
INTEGRATEDDRIVE
GENERATOR
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BOEING 747-400
TRAINING MANUALATA 24
ELECTRIC PWRVersion 1
Oct 1, 2009
NOTES
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FOR TRAINING PURPOSE ONLY PAGE 108 TECHNICAL TRAINING DEP
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BOEING 747-400
TRAINING MANUALATA 24
ELECTRIC PWRVersion 1
Oct 1, 2009
IDG Operation and Control (cont)
The heat generated by the IDG is carried by the oil tothe air/oil heat exchanger and oil cooler then back to theIDG. The position of the air/oil heat exchanger valve is
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p gnormally controlled by the GCU but can be overriddenby the electronic engine control (EEC) under someoperating conditions.
FOR TRAINING PURPOSE ONLY PAGE 109A TECHNICAL TRAINING DEP
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747 TRAINING MANUAL
General
The engine power system includes:
- Electrical system control panel
- Generator manual reset panel
iff i l i f ( 2)
ELECT PWR -- GEN DRIVE - ENGINE POWER COMPONENTS
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- Differential protection current transformers (12)
- Generator control current transformers (GCCT) (4)
- Generator circuit breakers (GCB) (4)
- Bus tie breakers (BTB) (4)
- Generator control units (GCU) (4)
- Integrated drive generators (IDG) (4)
- Lightning protectors (12).
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747 TRAINING MANUAL
2
APU
FIELDOFF OFF
FIELDOFFFIELD
BREAKERSPLIT SYSTEM
21
OFFFIELD
431
GEN FIELD MAN RESET
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ELECT PWR - GEN DRIVE - ENGINE POWER COMPONENTS
GENERATOR MANUAL
IDG
ELECTRICAL SYSTEM
DIFFERENTIAL PROTECTION
GCBBTB LIGHTING PROTECTOR
OFFFIELD
OFFFIELD
OPEN
CONTROL PANEL
GENERATOR CONTROL UNITGENERATOR CONTROL
CURRENT TRANSFORMER
RESET PANEL (P461)
CURRENT TRANSFORMER(4)(12)(4)(4)(4)(4)
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747 TRAINING MANUAL
General
Power from each IDG goes to its related load bus
through the GCB and to the synch bus through the BTB.The GCUs and the electrical system control panel
control the related BTBs and GCBs.
monitors real load and uses speed signals to keep the
correct real load balance with the other IDGs.
Excitation
The GCUs receives ac voltage from the PMG and changes
it to dc The IDG uses PMG voltage for excitation The
ELECT PWR -- GEN DRIVE - ENGINE POWER GENERATION CONTROL
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BTB Control
The electrical system control panel has a bus tie
switch for each IDG. When you set the switch to ISLN
(isolation), the BTB opens, and the ISLN light comes
on. When you set the bus tie switch to AUTO, the BTBcloses. In the AUTO position the BTB opens for a fault
trip or autoland command.
GCB/GCR Control
The electrical system control panel has a generator
control switch for each IDG. When you set the switch to
off, the generator control relay (GCR) and GCB open.
The OFF light in the generator control switch showsthat the GCB is open. When you set the control switch
to ON, the GCR closes. When the GCU senses good power
from the IDG, it closes the GCB.
Speed Control
BCU 1 sends a reference frequency to the GCUs. The GCUs
monitor the output frequency of the IDGs and compare it
to the reference frequency. A difference gives a speedcommand to the IDG. When IDGs are in parallel, the GCU
it to dc. The IDG uses PMG voltage for excitation. The
GCU controls the excitation to control the voltage and
reactive load of the generator.
Drive Disconnect
When you push the DRIVE DISC switch, the disconnectsolenoid in the IDG energizes, and the generator field
relay in the GCU opens. When you use the DRIVE DISC
switch to disconnect the IDG, you can only connect it
again on the ground at the IDG.
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747 TRAINING MANUAL
SYNCH BUS
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ELECT PWR - GEN DRIVE - ENGINE POWER GENERATION CONTROL
IDG
GCB/GCR
GCR TRIPEXCITATION
BTB CONTROL
DRIVE DISCONNECT
GCB
BTB
GCB CONTROL
SPEED
BTB CONTROL
GCU
ELECTRICAL SYSTEM
REFERENCEBCU 1
AC BUS
OFF
BUS
ON
a
w
a
w
DRIVE
aISLN
AUTOw
DISCDRIVE
CONT
GEN
TIEBUS
CONTROL
CONTROL PANEL (P5)
FREQUENCY
PMG
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747 TRAINING MANUAL
GCR
VOLTAGEREGULATOR
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ELECT PWR - GEN DRIVE - GENERATOR
3 PHASE
GCUCURRENT
IDG
PMG
EXCITER
MAIN
DC
3 PHASE
TRANSFORMERS
GENERATOR
GENERATOR
400HZ115/200V
1200HZ100V AC
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ELECT PWR - AUTOMATIC CONTROL - GENERATOR CONTROL UNITS
- CONTROL- PROTECTION
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747 TRAINING MANUAL
General
There are four GCBs and four BTBs that connect engine
power to the airplane main load buses and the synchbus. They are in the MEC in P514, P614, P515 and P615.
The breakers are a magnetic latch type and can operate
275 i 350 f 15
ELECT PWR -- MANUAL CONTROL - BTB/GCB POWER BREAKER
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at 275 amperes continuous or 350 amperes for 15
seconds. They can open up to 5000 amperes. The breakers
must get 28 volts dc to close or to open. The control
signals to the GCBs and BTBs come from the GCUs. The
GCBs and BTBs are inter-changeable with each other and
with the auxiliary power breakers.
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747 TRAINING MANUAL
P515
P615
CLOSE28V DC
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ELECT PWR - MANUAL CONTROL - BTB/GCB POWER BREAKER
P514
P614TRIP
28V DC
COMMON
CLOSE (PERMANENT MAGNET)
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747 TRAINING MANUAL
General
Lightning protectors give protection for the electrical
system from transients caused by lightning strikes.There are three for each generator channel. The
protectors are in P514, P614, P515 and P615.
The lightning protectors prevent equipment damage from
ELECT PWR -- AC PWR GEN AND PROTECTION - LIGHTNING PROTECTORS
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The lightning protectors prevent equipment damage from
transient voltages that are more than 252 volts. These
transient voltages go to ground through the lightning
protectors. The lightning protectors connect from the
load side of the GCBs to ground on all three phases. A
one-ampere circuit breaker is in series with eachlightning protector. This is to prevent loss of a load
bus because of a short to ground in a one related
lightning protector.
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747 TRAINING MANUAL
P515
TOIDGLOAD
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ELECT PWR - AC PWR GEN AND PROTECTION - LIGHTNING PROTECTORS
GCBP614
P615
P514LIGHTNINGPROTECTORS
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747 TRAINING MANUAL
Location
Six voltage harmonic distortion filter units are on the
floor beam in the right main equipment center above themain battery.
Operation
ELECT PWR -- AC PWR DISTRIBUTION - HARMONIC DISTORTION FILTER UNIT
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Voltage harmonic distortion filters minimize electrical
power degradation from the interactive video system
(IVS) and the overhead video system. The active filters
are on each phase. They sense excessive voltage
harmonics on the AC bus 3 and 4, and produce an equalharmonic 180 degrees out of phase to cancel the
harmonic.
The green light is on when there is power through the
unit. The red light stays off.
Maintenance Practices
The filter units have BIT which detects variousinternal failures. Push and hold the test switch for
five seconds. The green light goes off and the red
light comes on. A failure results in these:
- Filter shuts down
- Green light is off
- Red light is on
- ELEC FILTER FAIL status message.
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747 TRAINING MANUAL
P180 DCE30EQUIPMENTRACK DISTRIBUTION
PANEL
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ELECT PWR - AC PWR DISTRIBUTION - HARMONIC DISTORTION FILTER UNIT
FWD
INBD
NOSE GEAR
MAINGREEN LED
RED LED
TEST SWITCH
BATTERY
WHEEL WELL(FAULT)
(NORM)
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747 TRAINING MANUAL
General
The airplane has four generator control current
transformers (GCCT). The GCCTs give the GCUs datanecessary for control and protection. They are in the
generator power centers, P515, P615, P514 and P614.
Operation
WARNING: DO NOT DISCONNECT THE TRANSFORMER OUTPUT
CONNECTION WITH THE FEEDER LINES POWERED. THE
POTENTIALLY HIGH VOLTAGES COULD DAMAGE THE
TRANSFORMER OR RESULT IN INJURY TO PERSONNEL.
ELECT PWR -- AUTOMATIC CONTROL - GENERATOR CONTROL CURRENT TRANSFORMERS
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The generator feeders go through the holes in the GCCT.
During system operation the coils in the GCCTs make a
current that has a relation to the current that goes
through the feeders. The GCU uses this current for:
- Over/under excitation protection
- Difference current protection
- Reverse power protection
- Real/reactive load control
- Over/under frequency protection (Real load sensing
bias).
Characteristics
Each transformer assembly has toroidal shaped cores
with secondary winding wires that connect to an output
connector. Main ac feeder lines go through the large
holes in the transformer and become the primary winding
for each transformer core. The turns ratio of all the
windings is 1000 to 1. If the primary winding (feeder
line) is 115 volts ac, secondary winding voltage is as
much as 115,000 volts with the connector off (no load).Usually secondary voltages are very low because the
secondary loads have a low resistance.
- 124 -
747 TRAINING MANUAL
P615
P515
A PHASE
B PHASE
C PHASE
DIFFERENCE
REVERSE
OVER/UNDERCURRENT EXCITATION
POWER
1 1
1
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ELECT PWR - AUTOMATIC CONTROL - GENERATOR CONTROL CURRENT TRANSFORMERS
REAL/
THESE COILS CONNECT IN
P614
P514
OF/UFBIAS REACTIVE
LOAD
1SEPARATE EQUALIZATION LOOPS
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747 TRAINING MANUAL
C PHASE
1000
1000
P615
P515
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ELECT PWR - AUTOMATIC CONTROL - DIFFERENTIAL PROTECTION CURRENT TRANSFORMERS
A PHASE
B PHASE1000
1000
P614
P514
- 127 -
747 TRAINING MANUAL
General
To get maximum system capacity and prevent IDG overload
during parallel operation, the system must balance realand reactive loads between generators. To do this the
system compares the real and reactive loads on each
generator with the average load. The system controls
the IDG to this average value.
The example that shows uses a 10 to 1 ratio in the GCCT.
The four parallel IDGs supply a total reactive load of
210 amperes. The average current in the equalizing loop
is 21/4 or 5.25 amperes. If there are 2 amperes in thecurrent loop of IDG 1, GCU 1 senses the differential
current of 3.25 amperes. This causes more excitation to
the IDG so it gets more of the reactive load. In GCU 2
the differential current is in the reverse direction.
This causes less excitation to IDG 2
ELECT PWR -- AUTOMATIC CONTROL - EQUALIZING LOOP
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A coil in the generator control current transformer
(GCCT) senses load current from its related IDG. The
real/reactive load coils in each GCCT connect in series
to make an equalizing loop. The current in this loop isan average of the load current of all the generators in
parallel. A generator control unit (GCU) senses the
difference in the average loop current and the related
IDG current. The GCU circuits find the real and
reactive components of the load current to give speed
and electrical control of the IDG.
There are three other equalizing loops in the system:
- Over-excitation and under-excitation protection
- Over-frequency and under-frequency protection
- Difference current protection.
The loops give an out-of-balance indication to the GCU.
When an IDG is not in parallel, auxiliary contacts in
the related open BTB or GCB short the coils in the
GCCT. Auxiliary contacts of the SSB make two loops ifthe SSB is open.
This causes less excitation to IDG 2.
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747 TRAINING MANUAL
5.255.25
REACTIVE REACTIVE REACTIVE REACTIVELOAD 20 LOAD 70 LOAD 60 LOAD 60
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ELECT PWR - AUTOMATIC CONTROL - EQUALIZING LOOP
SSB
CTGENERATOR2
CT CT66
CT
GCB
BTB
AUX
GCB
BTB
AUX
GCU 3 GCU 4
5.25
KW/KVAR CUR
GCB
BTB
GCB
BTB
AUX
GCU 2GCU 1
5.25
AUX
7
5.25
ALL CONTACTORS SHOWN
IDG 2IDG 1 IDG 3 IDG 4
CONTROLCURRENTTRANSFORMER
IN CLOSED POSITION(AUX CONTACTS ARE OPEN)
SENSE MONITOR
CONTACTS3.25
CONTACTS1.75
CONTACTS.75
CONTACTS.75
AUXCONTACTS
- 129 -
747 TRAINING MANUAL
General
An electrically controlled mechanical governor controls
IDG speed. The electrical portion of the governor (trimhead) gets speed commands from the GCU trim head
control. When it is active, this trim head can keep the
output frequency of the IDG between 375 and 425 Hz.
Operation
- Master frequency: The master frequency comes from
BCU 1. It is the reference frequency when the
generator is in parallel.
- External power C phase: When you push externalpower switch 1, BCU 1 momentarily sends external
power 1 C phase frequency to the related GCUs. (GCU
1 and 2 if the SSB is open and all four if the SSB
is closed). When you push the external power 2
switch, BCU 2 sends external power 2 C phase
ELECT PWR -- GEN DRIVE - IDG SPEED CONTROL
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Operation
To find the correct speed command the GCU monitors the
frequency of the generator output and compares it to
the reference frequency in use. A difference betweenthe two frequencies causes a speed command to go to the
trim head.
To keep the real load in balance during parallel
operation, the trim head control gets A phase voltage
from the point of regulation and load current data from
the kw/kvar sense monitor. The kw/kvar current sense
monitor gets current inputs from the GCCT.
Reference Frequency
The reference frequency select circuit finds what
frequency the trim head control is to use. There are
five possible sources for the reference frequency:
- Synch bus C phase: With the GCB or BTB open and
synch bus frequency between 375-425 Hz, the GCU
uses synch bus C-phase. The exception to this iswhen the GCB opens for an underspeed or the BTB
opens for autoland.
switch, BCU 2 sends external power 2 C phase
reference frequency to BCU 1. BCU 1 sends it to the
related GCUs.
- APU power C phase: When you push the APU power 1
switch, BCU 1 momentarily sends APU power 1 C phasefrequency to the related GCUs (GCU 1 and 2 if the
SSB is open and all four if the SSB is closed).
When you push the APU power 2 switch, BCU 2 sends
APU power 2 C phase reference frequency to BCU 1.
BCU 1 sends it to the related GCUs.
- Internal reference frequency: The GCU uses an
internal reference when the reference frequency
from the BCU is more than 425 Hz or less than 375
Hz, or there is no BCU reference frequency signal.
- 130 -
747 TRAINING MANUAL
GCB
TO LOAD BUS
APU GEN 1EXT PWR 1
LIA
VA
wwON
LIA
VA
wwON
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ELECT PWR - GEN DRIVE - IDG SPEED CONTROL
GCU 1/2
GOV
TRIM
REFERENCETRIM HEAD
GCCT
GCBBTB
IDG
US
GCB OPEN
BTB OPEN
AUTOLAND
APU 1
APU GEN 2EXT PWR 2
LIAVA
ww
ON
BCU 2
MASTER
BCU 1SYNCH
EXTERNAL
SYNCH APU 2 C
EXTERNAL PWR
GCU
REFERENCE
INTERNAL
SYNCH BUS
HEAD
CONTROL
LOAD
FREQUENCY
SELECT
FREQUENCY
420-380 HZ
ENABLE
PHASE
3/4
FREQUENCY
POWER 1C PHASE
C PHASE
FREQUENCY
2 C PHASE
PHASE
LIAVA
ww
ON
CURRENT KW/KVARCUR SENSEMONITOR
REFERENCE BUS
BUS C
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ELECT PWR -- GEN DRIVE - GCR AND VOLTAGE CONTROL
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- 132 -
747 TRAINING MANUAL
ELECT PWR -- GEN DRIVE - GCR AND VOLTAGE CONTROL
General
The PMG supplies three phase, 100v ac and sends it to
the GCU for:
- Voltage regulation
- Internal power supplies
- Frequency indication (metering)
Frequency sensing (over/under frequency
the power to the exciter generator field to keep 115v
ac. During parallel operation the kw/kvar current sense
monitor gets inputs from the GCCT.
The voltage regulator gets inputs from the monitor. The
monitor uses the output of the GCCT to find the
reactive load of the generator. The voltage regulator
uses this data to increase or decrease the excitation
current to keep the correct reactive load of the
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- Frequency sensing (over/under frequency
protection)
- Field current (excitation).
Power to the GCU comes from three possible sources.
This makes sure that the bus protection circuits in the
GCU have power when the bus has power. These are the
possible sources:
- PMG voltage
- Main hot battery bus (battery switch on)
- DC ground handling bus.
Voltage Regulation
PMG voltage goes to the GCR. When the GCR closes, PMG
voltage goes to the voltage regulator. The voltage
regulator controls the PMG voltage and makes it a
pulsed dc current.
The dc current (excitation) goes to the exciter
generator field. This gives excitation power to the
main generator field. This excitation power causes the
main generator to supply 3 phase, 400 Hz, 115v ac. The
voltage regulator monitors this voltage and controls
current to keep the correct reactive load of the
generator.
GCR Control
The GCR is in the GCU and is a latch type relay with a
trip and a close coil. This relay opens or closes to
remove or connect the generator output to the voltage
regulator. These manually control the GCR:
- Generator control switch
- Field reset switch
- Fire switch
- Drive disconnect switch.
The control function of the generator field reset
switch on the P461 panel is active only when the
generator control switch is off.
The GCR automatically opens for one of these faults:
- SPMG (short on PMG)
- Overvoltage
- Undervoltage
- Differential fault
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747 TRAINING MANUAL
ELECT PWR -- GEN DRIVE - GCR AND VOLTAGE CONTROL
- Overfrequency
- Underfrequency
- Generator diode failure
- Open phase
- GCU internal failure.
After a fault trip occurs, you must set the GCB switch
to the off position then back to the on position to
make the field operate again.
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If there is still an overfrequency or underfrequency
after a reset, the GCR and GCB does a trip again. If
this occurs, disconnect the IDG. The software causesthe drive light to come on and makes the EICAS message
ELECT DRIVE show after the second trip.
- 134 -
747 TRAINING MANUAL
LOAD
GCCT
VOLTAGEEXCITER
MAIN GEN
BUS
1
OFF
ON
a
w
GEN REGULATOR
CURRENTCONT
GCBBTB
KW/KVARCUR SENSEMONITOR
GEN
CLOSE
OPEN
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ELECT PWR - GEN DRIVE - GCR AND VOLTAGE CONTROL
TRUPOWER
OF/UF
FREQUENCY
GCU
TO BCU FOR
PMG
IDG
ELECTRICAL SYSTEM
DRIVE
GENERATOR MANUAL
MAIN HOT
FIRE
S
TRIP
RFAULT
DRIVE
GCR
CLOSE
TRIP
wOFFFIELD
CYCLE
TRIP/
CLOSE
TRIP
BCU STBYBAT SW
DC
GEN
BAT BUS
PWR XFR
FREQUENCYINDICATION
PROTECTION
SENSE
SUPPLY
REGULATOR
GCS ORFIELD SWTO RESET
LOGIC
TRIPS
RESET PNL (P461)
CONTROL PNL (P5)
DISC
GCB
GHB
a
w
CLOSE
OS
OS
SW
RLY (P414)
2ND TRIP COUNTER
TO EICAS
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ELECT PWR -- GEN DRIVE - GCB CONTROL
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747 TRAINING MANUAL
ELECT PWR -- GEN DRIVE - GCB CONTROL
General
The generator control switch (P5) and the GCU control
the GCB. When you put the generator control switch tothe OFF position, the GCB automatically opens. When you
put the switch to the ON position, the GCU closes the
GCB if related system conditions are true.
GCB Close
reset the SUSP circuit (two unlike sources in parallel
for more than 110 ms). With the GCB and BTB closed a
digital signal goes to the BCU to open the XPC or APB
that gives power to the adjacent synch bus.
GCB Trip
The GCB opens for:
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These system conditions must all be true for the GCU to
close the GCB:
- Generator control switch to on
- GCR closed (no faults)
- No underspeed
- Dead load bus or generator voltage, frequency and
phase match the power on the synch bus (auto
parallel)
- No APB or XPC closed inputs with BTB closed
- No inputs from last source on logic
- Good power: voltage between 104.5 and 131 volts
sensed at the point of regulation (generator side
of GCB) and frequency between 375 and 425 Hz (input
from the PMG).
When these conditions are true, a close signal goes to
the GCB through a one shot that gives power to the GCB
for 300 ms. This close signal goes to the GCB through
the usually closed contacts of the GCB protection
relay. After the GCB closes, a set of auxiliary
contacts in the GCB causes the generator off light (P5)
to go off. Another set of contacts cause the BCU to
- Generator control switch to off
- Any malfunction that causes the GCR to open
- Underspeed
- An XPC or APB closed signal with the BTB closed(APU or external power no break power transfer
logic trip of a GCB)
- Last source on logic trip; last source logic trip
comes from the BCU for power transfers that use the
BTB. Last source on is the power source connected
to the airplane.
These are examples of last source on power:
- Example 1; The BTB is open and the IDG gives power
to its related load bus. If you put APU power on
the synch bus, the APU is the last source on. If
you then close the BTB, the GCB opens.
- Example 2; The BTB is open and external power gives
power to the synch bus. If you close the generator
control switch, and the IDG gives power to its
related load bus, the IDG is the last source on. If
you then close the BTB, external power
disconnects.
- 137 -
747 TRAINING MANUAL
ELECT PWR -- GEN DRIVE - GCB CONTROL
Signals that open the GCB also energize the GCB
protection relay. This opens the close circuit from the
GCU.
Break Power Transfer
A break power transfer occurs when the XPC or APB opens
before the GCB closes. This causes an interruption of
power on the synch bus. The break power transfer lets
the IDG give power to the synch bus when it cannot auto
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the IDG give power to the synch bus when it cannot auto
parallel with external or APU power. The break power
transfer occurs when APU or external power give power
to the synch bus and:
- Generator control switch is on
- GCR closed (no faults)
- No underspeed
- BTB is closed
- there is a 6 seconds time delay.
If the synch bus has power by one IDG, and you try to
connect another IDG that cannot match the synch busfrequency, the GCB does not close.
- 138 -
747 TRAINING MANUAL
ON w
OFFa
DRIVE
w
a
P5
ARINCRCVR
TD 6
TO BCUFOR XPCAND APBTRIPS(ADJ SYNCHBUS PWR)
A
DTUNDERSPEED
GCR CLOSED
BTB CLOSEDGCS ON
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ELECT PWR - GEN DRIVE - GCB CONTROL
FROM
TO
GCU GCB PROTECTION
CLOSE
OPEN
AUX
GCB
SO
GCS CYCLED
CONTACTS
O
AUTO PARALLEL
GCB CLOSED
CONT
LT &BCU
SUSP
GOOD PWR
ARINCRCVRBCU
A
LAST SOURCE ON LOGIC TRIP
GCB TRIP AND RESET LOGIC
APBOR XPCCLOSED
S
R
UNDERSPEED
DEAD LOAD BUS
SW
GEN
FOR
OFF
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747 TRAINING MANUAL
ELECT PWR -- GEN DRIVE - BTB CONTROL
General
The BTB manually operates with the bus tie switch. If
you put the switch to the isolation (out) position, theBTB opens and the ISLN light comes on. If you put the
switch to the AUTO (in) position, the BTB closes
through auto parallel, dead synch bus or GCB logic.
With the BTB closed the ISLN light goes out.
BTB Close
- Load bus malfunction (differential malfunction)
- Synch bus malfunction
- SUSP with the GCB closed
- Over or under excitation; A parallel conditionmalfunction that opens the BTB first. If the
condition continues, the system thinks it is a
voltage fault and the GCR and GCB open
- Difference current; Generator output is different
than the average of the other generators that
operate in parallel by 35 to 40 amperes
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BTB Close
The BTB closes if all of these conditions are true:
- No load bus malfunction (differential malfunction)
- No synch bus malfunctions (differential or
negative sequence)
- No SUSP fault with the GCB closed
- No generator power faults (over or under
excitation, reverse power, difference current,
open phase, over or under frequency)
- No autoland request
- Bus tie switch in AUTO- No adjacent synch bus power, auto parallel
conditions true or GCB open. If the generator
cannot match the synch bus power, the BTB does not
close.
Close signals to the BTB go through the usually closed
contacts of the BTB protection relay.
BTB Trip
The BTB opens for:
operate in parallel by 35 to 40 amperes
- Reverse power; This does not let the electrical
system operate the IDG as a motor (8+/-1 kw)
- Open phase; This is when the lowest phasegenerator feeder current is less than 6+/-5
amperes and the next lowest is 55+/-5 amperes or
more
- Over and under frequency; below 370 Hz and above
430 Hz
- Autoland request; When the autoland signal goes
away, the BTB closes again
- Bus tie switch to ISLN; With the BTB switch in the
ISLN position a signal goes directly to open theBTB and reset internal fault latches in the GCU.
Signals that open the BTB also energize the BTB
protection relay. This opens the close circuit from the
GCU.
Auto Reclose
Auto reclose of the BTB occurs when the BTB opensautomatically in any channel, and subsequently the GCB
opens automatically in the same channel. The BTB does
- 141 -
747 TRAINING MANUAL
ELECT PWR -- GEN DRIVE - BTB CONTROL
not close again by the auto reclose logic if the BTB
opened because of load bus malfunctions, synch bus
malfunctions, SUSP, autoland or by manual operation of
the bus tie switch. You must put the bus tie switch to
the ISLN position then to the AUTO position to get the
BTB to close.
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- 142 -
747 TRAINING MANUAL
LOAD
SUSP
RESET
GENERATOR
ISLNa
SYNCH
FROM ARINCBCU RCVR
POWERFAULTS
S
R
GCB
BUS FAULT
BUS FAULT
CLOSED
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ELECT PWR - GEN DRIVE - BTB CONTROL
TO BCU FOR
AUTO PARALLEL
DEAD ADJ SYNC BUS
BTB OPEN
LIGHT
AUTO
AUTO LAND
GCU
CYCLE
ISLNa
AUTOw
BUS TIE
GCB OPEN
BTB
CLOSE
OPEN
AUX
BTB
SO
S
GCS ON
BTB
AUTO RECLOSE
GCB
POSITIONLOGICCONTACT
PROTECTION
SWITCH
TO RESET
R
SO
OPENS
OPEN
- 143 -
BOEING 747-400TRAINING MANUAL
ATA 24
ELECTRIC PWRVersion 1
Oct 1, 2009
POWER TRANSFER SUMMARY
This chart summarizes all power transfers to sources on
the left side. The chart shows contactors or breakerstripped during normal no break power transfers andnon-normal break power transfers.
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FOR TRAINING PURPOSE ONLY PAGE 143A TECHNICAL TRAINING DEP
BOEING 747-400TRAINING MANUAL
ATA 24
ELECTRIC PWRVersion 1
Oct 1, 2009
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FOR TRAINING PURPOSE ONLY PAGE 143B TECHNICAL TRAINING DEP
BOEING 747-400TRAINING MANUAL
ATA 24
ELECTRIC PWRVersion 1
Oct 1, 2009
NOTES
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FOR TRAINING PURPOSE ONLY PAGE 144 TECHNICAL TRAINING DEP
BOEING 747-400TRAINING MANUAL
ATA 24
ELECTRIC PWRVersion 1
Oct 1, 2009
ENGINE POWER SYSTEM (IDG)
General
The IDG portion of the engine power system involvesthe mechanical aspects of the IDG and its oil coolingcomponents.
Operation
Control
Control and monitoring of the IDG is done by the GCU.The GCU receives oil temperature, oil pressure, andIDG speed signals. It sends speed commands to theIDG governor and control signals to the air/oil heatexchanger valve
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Operation
The CSD portion of the IDG is a hydromechanicaldevice. It adds or subtracts speed from the variableinput of the engine gearbox to maintain the IDGgenerator at 12,000 rpm.
IDG oil is used for speed control, lubrication and cooling.
Heat generated by the IDG is cooled by passing the oilthrough an air/oil heat exchanger and a fuel cooled oilcooler. The cooled oil is then returned to the IDG. Theoil cooler is the primary means of cooling the oil but isassisted by the air/oil heat exchanger under certainoperating conditions.
exchanger valve.
Oil temperature comes from two temperature bulbsinside the IDG and is used for:- High oil temperature light- Oil out temperature indication- oil rise temperature indication- Air/oil heat exchanger valve control
oil pressure comes from an oil pressure switch insidethe IDG and is used for the IDG DRIVE light.
Speed inputs come from the magnetic pickup unit (MPU)and are used for underspeed trips and airmode inhibits.
Speed commands from the GCU to the IDG are used tocontrol IDG speed to maintain reference frequency andreal load division.
FOR TRAINING PURPOSE ONLY PAGE 144A TECHNICAL TRAINING DEP
BOEING 747-400TRAINING MANUAL
ATA 24
ELECTRIC PWRVersion 1
Oct 1, 2009
Control (cont)
Air/oil heat exchanger valve control signals are sent to
the valve to control the opening and closing of the valve.The signal must pass through an override pressureswitch. The pressure switch along with the air/oil heatexchanger valve override solenoid allow the EEC tooverride the GCU signal and control the valve.
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FOR TRAINING PURPOSE ONLY PAGE 144B TECHNICAL TRAINING Dep
BOEING 747-400TRAINING MANUAL
ATA 24
ELECTRIC PWRVersion 1
Oct 1, 2009
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FOR TRAINING PURPOSE ONLY PAGE 145 TECHNICAL TRAINING DEP
747 TRAINING MANUAL
General
The IDG system includes these components:
- Air/oil heat exchanger valve override solenoid -controls the position of the override pressure
switch. It is controlled by the EEC and is at the
1:00 position under the intermediate fan case
- Override pressure switch - when closed it lets the
GCU control the air/oil heat exchanger valve. When
open, it causes the air/oil heat exchanger valve
t It i t th 1 00 iti d th
ELECT PWR -- GEN DRIVE - IDG COMPONENTS
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to open. It is at the 1:00 position under the
intermediate fan case
- Oil cooler and bypass valve - cools IDG oil withfuel. They are at the 9:00 position below the 2.9
bleed valve.
- IDG - Maintains the IDG generator speed at 12000
rpm. It is on the aft, left side of the main
gearbox.
- Air/oil heat exchanger and valve - cools IDG oil.
They are at the 3:00 position under the
intermediate fan case.
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747 TRAINING MANUAL
OVERRIDE
IDG AIR/OIL HEAT EXCHANGER
VALVE OVERRIDE SOLENOID
HPC SECONDARY FLOW CONTROL
VALVE AND IDG AIR/OIL
HEAT EXCHANGER VALVE
PRESSURE
SWITCH
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ELECT PWR - GEN DRIVE - IDG COMPONENTS
OIL COOLER AND BYPASS VALVEIDG AIR/OIL HEAT
EXCHANGER AND VALVEIDG
HEAT EXCHANGER VALVE
OVERRIDE SOLENOID ASSEMBLY
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747 TRAINING MANUAL
Right Side
These are on the right side of the IDG:
- IDG housing - a two part magnesium casting with adry weight of 118 pounds
- Oil ports - the oil in and oil out ports give a
connection point between the IDG and the external
oil cooling system; a pressure relief valve at the
oil in port gives protection to the IDG housing
from overpressure if there is a core rupture of the
fuel/oil cooler
60 psid; the differential pressure indicator does
not operate below 145 F to prevent a nuisance
indication
- Electrical connectors - two connectors (A and B)
make an interface with airplane wiring forcontrol, protection, and monitor circuits.
Left Side
These are on the left side of the IDG:
- Terminal block - the main generator stator three
ELECT PWR -- GEN DRIVE - IDG GENERATOR
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fuel/oil cooler
- Governor adjustment - a mechanical adjustment that
sets the basic speed of the IDG- Drain and fill ports - you remove the case drain
plug to drain the oil from the IDG case; the
service couplings connect to the pressure fill
port and overflow drain port to do servicing of the
IDG; the overflow drain connects to an internal
standpipe
- Case thermal relief valve - lets hot IDG oil drain
overboard if the IDG oil temperature is more than
430F (221C)- Oil level indicator - a prismatic sight glass that
gives a visual indication of low IDG oil
- Scavenge filter and delta pressure indicator - a
non-bypass filter on the discharge side of the
scavenge pump removes contamination from the oil
that goes out of the IDG; the scavenge filter
contains a pop-out delta pressure indicator; the
red button comes out when the pressure drop gets to
Terminal block the main generator stator three
phase output and neutral output leads connect at a
four stud terminal block- Disconnect reset ring - lets you do a reset of a
disconnected IDG on the ground; this engages the
IDG input and interconnect shafts
- Muff spline - a 1.5-inch, male spline on the input
drive shaft that you can remove; it connects the
IDG shaft to the engine gearbox; the input shaft
shear section breaks if there is an input torque of
9000 +/-400 inch-pounds.
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747 TRAINING MANUAL
SCAVENGE FILTER CASE THERMALRELIEF VALVEDELTA P INDICATOR
(ACTIVATED)
ADJUSTMENTGOVERNOR
FILL PORTPRESSURE
OIL IN
OIL OUT
DRAIN PORTOVERFLOW
CONNECTOR BELECTRICAL
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ELECT PWR - GEN DRIVE - IDG GENERATOR
CONNECTOR A
RIGHT SIDE
LEFT SIDE
FILTER
INDICATORLOW OIL LEVEL
CASE
SERVICE
RESET RINGDISCONNECT
SHEAR SECTIONDRIVE SHAFT
SPLINEMUFF
COVERTERMINAL
GENERATOR
ELECTRICAL
OIL OUT
SCAVENGE COUPLINGS
DRAIN
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747 TRAINING MANUAL
THIS PAGE INTENTIONALLY LEFT BLANK
ELECT PWR -- GEN DRIVE - IDG OPERATION
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747 TRAINING MANUAL
ELECT PWR -- GEN DRIVE - IDG OPERATION
clutch to disconnect and stop the operation of the IDG.
You cannot reset the thermal disconnect. You can reset
the electrical solenoid disconnect.
Case Thermal Relief
If the IDG temperature goes above 450F (232C), a solder
pellet melts and lets all of the oil drain from the
IDG.
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747 TRAINING MANUAL
VARIABLE
OIL-IN
LEFT PUMP
RIGHT PUMP TO
GOVERNORMAG
CHARGE
CONT CYL
FIXED
DEAERATOR
EXTERNAL
FROM
TO SUMP
CHARGE
DISPLACEMENTHYDRAULICUNITS AND MOTOR
AND MOTOR SUMP
TRIM
DISPLACEMENTHYDRAULICUNITS
PUMP
TEMP BULB
CIRCUITBYPASSVALVE
COOLER
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ELECT PWR - GEN DRIVE - IDG OPERATION
OUTPUT
PLANETARY
GENERATOR
CHARGE PUMP
CONTROL
WORKING
CHARGE
RETURN OILSUMP OIL
CHARGE
TO
TO EXT
DISCONNECT
INPUT
DISCONNECTINVER SCAV
SCAV SCAV
OIL-OUT
CHARGE
INPUT
PRESSURE DIFFERENTIAL
CASE THERMAL
PRESSURESWITCH
PRESSURE
PRESSURE
PRESSURE
SUPPLY OILRELIEF VALVE
GEAR
DIFF
SPEED SENSOR
SOLENOIDPUMP
PUMP FILTER
INDICATOR
RELIEFVALVE
SHAFT
RESET RING
CIRCUITBYPASSVALVE
COOLER
TEMP BULB
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747 TRAINING MANUAL
General
You can disconnect the IDG input shaft from the
interconnect shaft from the flight compartment. This
lets the engine continue to operate while a defectiveIDG stops.
Operation
Push the guarded drive disconnect switch on the P5
panel to disconnect the IDG. A disconnect solenoid
energizes and lets a spring-loaded plunger engage the
interconnect shaft This ca ses the interconnect shaft
the solenoid nose pin moves into position, and you hear
a click.
Thermal Disconnect
The IDG also has a thermal disconnect in the disconnect
solenoid. The thermal material uses solder in a closed
chamber. At temperatures more than 213C (415F), the
solder melts and lets a spring retract the solenoid
pin. This lets the plunger engage the interconnect
shaft to disconnect the IDG.
Yo can not reset a thermal disconnect
ELECT PWR -- GEN DRIVE - IDG DISCONNECT - FUNCTIONAL DESCRIPTION
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interconnect shaft. This causes the interconnect shaft
to move away from the input shaft. This disconnects theIDG from the input shaft.
The same disconnect signal goes to the GCU to open the
GCR and GCB. This isolates the generator from its
electrical load. When the IDG disconnects, a DRIVE DISC
advisory and status message show on EICAS.
Maintenance Practices
Do not push the disconnect switch unless the engine is
at or above idle speed. You can push the disconnect
switch with the engine off. You must then reset the IDG
before you start the engine. The dog teeth do not fully
disconnect if the engine is less than idle speed or
off.
You can only reset the IDG on the ground with the
engine off. To do this, pull out the reset ring until
You can not reset a thermal disconnect.
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747 TRAINING MANUAL
DISCONNECT
DRIVE
DISCONNECT
PLUNGER
RAMP
GEN DR DISC
THERMAL
P180CLUTCH
SOLENOID
DISCONNECTSOLDER
RESET RING
28V DCBAT BUS
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ELECT PWR - GEN DRIVE - IDG DISCONNECT - FUNCTIONAL DESCRIPTION
TRIP
GCU BCU(S) EIU(S)
GCR
GCB
GEN
DRIVE
INTERCONNECT
DRIVE DISC 1
AUX EICAS
>DRIVE DISC 1
MAIN EICAS
BUS
DRIVE
w
a
w
a
ON
OFF
DISC
CONT
DISCSWITCH
TRIP
STATUS PAGE
ADVISORY
INPUTSHAFT
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747 TRAINING MANUAL
General
A speed sensor on the interconnect shaft senses the IDG
speed. The speed sensor is a magnetic pickup unit
(MPU). As each tooth on the shaft comes near to thesensor, it causes a current in the sensor. This signal
goes to the speed detector circuit in the GCU. At less
than 4525 rpm a trip signal goes to the GCB for an
underspeed condition. The sensor also sends signals to
inhibit undervoltage or underfrequency trips until the
IDG input speed is more than 4525 rpm. At 6100 rpm and
above the GCU sends a digital signal to the bus control
units The BCUs use this signal to cause airmode
ELECT PWR -- GEN DRIVE - IDG SPEED SENSING
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units. The BCUs use this signal to cause airmode
inhibits.
These are the related engine values for IDG input
speeds of 4525 and 6100 rpm:
- PW 54.3 and 73.3% N2
- GE 55.3 and 74.6% N2
- RR 50.0 and 67.4% N3.
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747 TRAINING MANUAL
INPUT
MPUINPUT
IDG
SHAFT
SPEEDSENSOR
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ELECT PWR - GEN DRIVE - IDG SPEED SENSING
AIR
BCU 1
BCU 2
<4525
>6100
SPEED DETECTOR
US LOGIC
ARINC
US TRIPGCB
GCU
UNDER SPEED
RPM
RPM429 XMTR
CIRCUITS MODE
AIRMODE
INHIBITS
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747 TRAINING MANUAL
General
There is a mechanical governor in the IDG that controls
its speed. The governor is a spring-biased flyweight
operated hydraulic control valve. During usualoperations there is a relation between the position of
the flyweights and a magnetic field supplied by a coil
above the flyweights. The GCU controls the current in
the coil. This sets the position of the flyweights and
thus the speed of the IDG. This lets the GCU adjust the
speed of the IDG to keep the reference frequency and kw
load balance.
ELECT PWR -- GEN DRIVE - IDG SPEED CONTROL
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747 TRAINING MANUAL
KW CURRENT
TRIM
IDG VOLTAGE
GENERATOR CONTROL UNIT
REFERENCE
CONNECTOR A
MAGTRIMCOIL
HEADCONTROL
FREQUENCY
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ELECT PWR - GEN DRIVE - IDG SPEED CONTROL
IDGGOVERNOR
FLYWEIGHTS
DRAIN TO
CHARGE OILCONTROLCYLINDER
(SUPPLY)
CASE
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747 TRAINING MANUAL
General
The GCU monitors oil temperature to and from the IDG
cooling loop. It gets these temperatures from two
resistive type temperature bulbs. The oil outtemperature bulb senses the temperature of the oil that
goes out of the IDG to the cooling loop. The oil in
temperature bulb senses the temperature of the oil that
comes in from the cooling loop. The oil in and oil out
temperatures go to the oil temperature processor
circuit in the GCU. The temperature processor supplies
signals to the BCU for:
DRIVE X TEMP SNS status message shows if oil out or oil
in temperature is more than 260C or less than -70C.
Maintenance Page
Oil out and Oil rise temp shows on the maintenance page
at all times. EICAS makes a snapshot if IDG rise
temperature is more than 10C above than the other
generators.
CMC Messages
To find low IDG oil quantity, the GCU software monitors
ELECT PWR -- GEN DRIVE - IDG OIL TEMPERATURE
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- Main EICAS (advisory message)- Auxiliary EICAS (status message)
- Maintenance page (indication).
Main EICAS
If oil pressure is less than 140 psi, or oil out
temperature is more than 185 C, EICAS shows an ELEC
DRIVE 1-4 advisory message and makes an auto snapshot.
For this to occur the engine must be on, and the IDGconnected.
Auxiliary EICAS
IF the IDG outlet temperature is more than 155C but
less than 260C for 10 minutes, or oil pressure is less
than 140 psi, EICAS shows an ELEC DRIVE 1-4 status
message and makes an auto snapshot. For this to occur,
the engine must be on, and the IDG connected.
the cycle rate of the charge pressure switch and makesa CMC message IDG-X LOW OIL QUANTITY.
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747 TRAINING MANUAL
General
The IDG air/oil heat exchanger gives more cooling as
necessary for the IDG oil. This occurs when engine
power is low or IDG oil temperature is high. The heatexchanger valve controls air to the heat exchanger.
Heat Exchanger
The air/oil heat exchanger is a tube and fin assembly
in one housing. The oil in and return ports are on the
aft face of the heat exchanger.
position. Switches on the bottom edge of the valve body
provide valve position signals to the GCU. A visual
valve position indicator is on the top edge of the
valve body.
ELECT PWR -- GEN DRIVE - IDG AIR/OIL HEAT EXCHANGER AND VALVE
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Valve
The air/oil heat exchanger valve is a two-position
valve that ducts fan air or 2.5 bleed air to the heat
exchanger. Which air is used for cooling depends on the
position of the 2.5 bleed ring of the engine. When the
2.5 bleed ring is open (low engine power), 2.5 air is
used for IDG oil cooling. At high engine power the 2.5
bleed ring is closed and fan air is used for cooling.
The heat exchanger valve is on the forward face of theheat exchanger. It consists of these three main
subassemblies:
- Solenoid
- Dual butterfly valves mounted on a single shaft
- Fuel pressure driven actuator.
The valve is solenoid controlled and hydraulically
operated. It is either fully open or fully closed. Thevalve is spring loaded to the open (fail safe)
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747 TRAINING MANUAL
CASE
INTERMEDIATE
2.5ORAIRFAN
VALVEEXCHANGERIDG AIR/OIL
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ELECT PWR - GEN DRIVE - IDG AIR/OIL HEAT EXCHANGER AND VALVE
OIL-INPORT
AIRBLEED
VALVESBUTTERFLY
CONNECTORELECTRICAL
HEAT EXCHANGERIDG AIR/OIL
PORTOIL-OUT
FWD
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747 TRAINING MANUAL
FUEL OUT
COOLING COREENGINE OIL
CORECOOLINGIDG OIL
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ELECT PWR - GEN DRIVE - IDG OIL COOLER
PUMP FILTER)(TO FUELFUEL OUT
OIL INIDG
OUTIDG OIL
BOOST STAGE)(FUEL PUMPFUEL SUPPLY
BYPASS VALVEFUEL PUMPFUEL FROM
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747 TRAINING MANUAL
General
When the engine oil temperature is less than 160C or N2
speed is more than 72%, the EEC energizes the IDG
air/oil heat exchanger valve override solenoid to letPs3 air pressure close the override pressure switch.
This connects the GCU to the IDG air/oil heat exchanger
valve so that the GCU can control it.
When IDG oil temperature is less than 127C, the GCU
supplies 28v dc through the pressure switch to the heat
exchanger valve control solenoid. When the control
solenoid is energized, fuel pressure (PF) closes the
heat exchanger valve
ELECT PWR -- GEN DRIVE - IDG AIR/OIL HEAT EXCHANGER VALVE CONTROL
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heat exchanger valve.
If the IDG oil temperature is more than 127C, the GCU
removes power from the control solenoid of the heat
exchanger valve. When power is removed, the solenoid
de-energizes and removes fuel pressure to let the
spring open the valve. On decreasing IDG oil
temperature, the GCU closes the valve at 104C.
There is a switch in the heat exchanger valve thatsenses valve position for the GCU. This lets the GCU
determine proper operation of the valve.
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747 TRAINING MANUAL
EEC
GCU
SUPPLYPOWER
>127CPROCESSORTEMP
SWITCHPRESSOVERRIDE
PS3
TO GCUPOSITIONVALVE
CLOSED
OVERRIDE SOLENOID
EXCHANGER VALVEIDG AIR/OIL HEAT
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ELECT PWR - GEN DRIVE - IDG AIR/OIL HEAT EXCHANGER VALVE CONTROL
IDG
PFOUTFUEL
INFUEL
COOLEROILFUEL
OIL OUT
AIRBLEED2.5ORAIR
TEMPERATURE
EXCHANGER VALVEIDG AIR/OIL HEAT
FAN
INLET OIL
SENSOR
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747 TRAINING MANUAL
General
The GCU provides 28v dc to close the IDG air/oil heat
exchanger valve and removes the voltage to open the
valve. The GCU monitors these valve command signals aswell as valve position. From these, the GCU can
determine if the valve fails.
EIU Logic
If the GCU senses a difference between the commanded
position and the actual valve position, a disagreement
condition exists. If the disagreement exists for longer
than 6 seconds the GCU sends a valve failed signal to
ELECT PWR -- GEN DRIVE - IDG COOLING VALVE FAILURE
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than 6 seconds, the GCU sends a valve failed signal tothe BCUs. When it receives the valve failed signal, BCU
1 (BCU 2 if BCU 1 has failed) sends a valve failed
signal to the EIUs. If engine N2 speed is 88% or more
and the valve is not being commanded open by the EEC
then after 60 seconds, the EIUs cause ELEC IDG VALVE to
show on the EICAS status page.
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747 TRAINING MANUAL
6 SECTD
TEMPERATUREPROCESSOR
VALVEPOSITIONCONTROLLOGIC
IDG 1
DISAGREEMENT
TRANSMITTER429
BCU 1 BCU 2
- N2 >88%
IDGTEMPERATURE
VALVECOMMANDS
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ELECT PWR - GEN DRIVE - IDG COOLING VALVE FAILURE
GCU 1
2, 3, AND 4 ARE SIMILARNOTE: SYSTEM 1 SHOWN,
EIU
ELEC IDG 1 VALVE
EICAS STATUS PAGE
OPEN BY EEC
N2 >88%- NOT COMMANDED
- (60 SEC TD)
AOC VLV 1
VALVE POSITION
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747 TRAINING MANUAL
General
The IDG air/oil heat exchanger valve override solenoid
is one of two solenoids mounted to a common valve
housing. the solenoid controls filtered Ps3 air to theoverride pressure switch. This solenoid is controlled
by the electronic engine control (EEC) and is used to
override GCU commands. The EEC de-energizes the
override solenoid when it senses engine oil temperature
above 160`C or engine speed below 72% N2. De-energizing
the solenoid vents Ps3 air from the pressure switch
causing it to open. This removes power from the IDG
air/oil heat exchanger valve control solenoid causing
the valve to go open. The override solenoid is not linereplaceable
ELECT PWR -- GEN DRIVE - OVERRIDE SOLENOID AND PRESSURE SWITCH
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the valve to go open. The override solenoid is not linereplaceable.
Pressure Switch
The IDG air/oil heat exchanger valve override pressure
switch is a single pole, double throw type switch. It
is spring loaded open when no air pressure is applied
to it. The switch is a line replaceable unit.
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747 TRAINING MANUAL
INTERMEDIATE
PS3 MUSCLE
PS3
LEFT SOLENOID
NORMAL MODE (ENERGIZED)
IDG AIR/OIL HEATPRESSURETO PRESSURESWITCH
CASE
EXCHANGER VALVEOVERRIDE SOLENOID
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ELECT PWR - GEN DRIVE - OVERRIDE SOLENOID AND PRESSURE SWITCH
FWD
IDG AIR/OIL HEAT
VENT
PRESSURE
PS3
LEFT SOLENOID
SWITCH VENTPRESSURE
OVERRIDE MODE (DEENERGIZED)
EXCHANGER VALVEOVERRIDE PRESSURESWITCH
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747 TRAINING MANUAL
General
You service the IDG with a pressure fill type system.
Pressure and drain lines attach to the related
couplings on the IDG. When you attach the pressure fillline to the IDG, a check valve in the elbow coupling
opens to let the IDG fill by pressure. When you fill
the IDG through the pressure fill coupling, oil flows
first through the IDG scavenge filter then through the
external oil circuit and back to the IDG. Air in the
circuit goes out in front of the oil to the overflow
drain. The oil level goes up until it gets to the top of
the overflow drain. This is the correct fill level for
the IDG oil system. The IDG oil level is correct whenoil goes out of the overflow drain and the flow
ELECT PWR -- GEN DRIVE - IDG SERVICING
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oil goes out of the overflow drain and the flow
decreases to a drip after you turn off the fill
pressure. You must let a minimum of one quart of oil go
out of the IDG overflow drain to make sure that you
serviced the IDG correctly.
WARNING: MANY WARNINGS AND CAUTIONS ARE CONTAINED IN
THE MAINTENANCE MANUAL REGARDING IDG
SERVICING. FAILURE TO ADHERE TO THEMAINTENANCE MANUAL PROCEDURES MAY RESULT IN
IMPROPER IDG SERVICING AND SUBSEQUENT IDG
FAILURE OR INJURY TO PERSONNEL.
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747 TRAINING MANUAL
TO SUMPSCAVENGE
AIR/OIL
FUEL/OIL
AIR EXHAUST
250 PSI
CHARGE
DE-AERATORCHARGEPRESSURE
RELIEFVALVE
COOLER
HEAT
EXCHANGER
PUMP
OIL IN
OIL OUT
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ELECT PWR - GEN DRIVE - IDG SERVICING
OVERFLOW
SCAVENGE
350 PSI
SUMP
PRESSURE
STAND
IDG
PRESSURE
OIL LEVEL
CONTAINER
OVERFLOW
IDG
FILTER
SCAVENGEPRESSURE
RELIEFVALVE
OIL LEVEL
SIGHT GAUGE PIPE DRAIN COUPLING
DRAIN
FILLCOUPLING
FILL
COUPLING
INDICATOR
FWD
COUPLING
SCAVENGEPUMPS
CASETHERMALRELIEFVALVE
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747 TRAINING MANUAL
General
The IDG oil level indicator is on the lower right side
of the IDG. You use it to do a visual check of the IDG
oil level. The graphic shows the indicator with the IDGoil at three different levels.
The left view shows a very low oil level. The indicator
shows a large bright spot.
The middle view shows an oil level approximately one
quart low. The indicator shows a light area in the
center.
The right view shows a full IDG. The indicator shows a
ELECT PWR -- GEN DRIVE - IDG OIL LEVEL INDICATOR
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g
fully dark area with an OK.
You must service an IDG that shows the left and middle
indications.
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747 TRAINING MANUAL
General
The scavenge filter does not have a bypass. It removes
contamination from the oil that goes out of the IDG. It
has a filter element and a differential indicator on
the aft face of the IDG.
The differential pressure indicator does not operate
below 145 F. This prevents a nuisance indication.
If the indicator is out, you must replace the IDG. If
the filter shows damage or there is indications that
contaminated oil went through it, you must flush the
external oil circuit before you can operate a new IDG.If there is no filter damage and no indication the
i d il h h i d h
ELECT PWR -- GEN DRIVE - IDG SCAVENGE FILTER
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contaminated oil went through it, you do not have to
flush the external oil cooling circuit.
CAUTION: BE SURE FILTER COMPONENTS ARE SEATED IN THE
IDG SCAVENGE FILTER CAVITY BEFORE INSTALLING
FILTER COVER. DO NOT FORCE FILTER COMPONENTS
INTO HOUSING BY TIGHTENING FILTER COVER.
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747 TRAINING MANUAL
SCAVENGE
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ELECT PWR - GEN DRIVE - IDG SCAVENGE FILTER
SCAVENGE
"O" RING
USUAL (RESET)OUT
"O" RING
DELTA PINDICATOR
RED BUTTON RED BUTTON
FILTER
FILTER
FWD
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747 TRAINING MANUAL
ACCESSORY
LOCKWIRE
GEARBOX
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ELECT PWR - GEN DRIVE - IDG REMOVAL AND INSTALLATION
QAD RING AND
LOCKWIRE
TENSION
ALIGNMENT MARKS
QAD TENSION
ADAPTER PLATE
BOLT
(CLOSED POSITION)
BOLT
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747 TRAINING MANUAL
General
These supply power for airplane dc power:
- Main battery - forward-right main equipment center
- Main battery charger - forward-right main
equipment center, E30-2
- Transformer rectifier units (TRU) (4) - forward-
right main equipment center, E30-2
- APU battery - aft equipment center, E33-2
- APU battery charger - aft equipment center, E33-1.
ELECT PWR -- DC GENERATION - INTRODUCTION
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- 180 -
747 TRAINING MANUAL
APU BATTERY
APU BATTERY CHARGER
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ELECT PWR - DC GENERATION - INTRODUCTION
TRU(S)
MAIN MAINBATTERY
CHARGER
BATTERY
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747 TRAINING MANUAL
Power Components
The dc power system components are in the MEC, flight
deck and in the aft equipment center. The dc power
system includes:
- TR Units (4)
- Electrical system control panel
- Remote Control Circuit Breakers
- Battery Chargers (2)
- DC Current Sensors (6)
- Batteries (2)
- APU TR Unit.
ELECT PWR -- DC GENERATION - DC POWER COMPONENTS
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747 TRAINING MANUAL
ELECTRICAL SYSTEM
BATTERY (2)
DCCS (6)
CONTROL PANEL (P5)
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ELECT PWR - DC GENERATION - DC POWER COMPONENTS
TRU
APU TRUBATTERY
RCCB(4)
CHARGER (2)
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747 TRAINING MANUAL
THIS PAGE INTENTIONALLY LEFT BLANK
ELECT PWR -- DC GENERATION - DC POWER SYSTEM
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747 TRAINING MANUAL
ELECT PWR -- DC GENERATION - DC POWER SYSTEM
General
The dc power system supplies and distributes 24/28
volts dc to the airplane. These supply dc power to the
system:
- 75 ampere TRUs (4)
- 24 volt 40 amp-hr batteries (2)
- Battery chargers (2).
These are the dc buses:
- DC buses 1, 2, 3, and 4
- Main hot battery bus- APU hot battery bus
- Main battery bus
ampere TRU and keeps a constant potential on the main
hot battery bus.
APU Hot Battery Bus
The APU hot battery bus gets power from the APU battery
and the APU battery charger. Under some conditions, the
APU battery charger operates as a 64 ampere TRU and
keeps a constant potential on the APU hot battery bus.
Main Battery Bus
The main battery bus gets power through RCCBs from two
possible power sources, the dc bus 3 source or the mainhot battery bus source. Under usual conditions, dc bus
3 gives power to the main battery bus through the
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Main battery bus
- APU battery bus.
DC Buses
The four dc buses get power from four 75 ampere TRUs.
DC current sensors (DCCSs) monitor current from the
TRUs. Each dc bus can be in parallel with the othersthrough the contacts of a dc isolation relay (DCIR).
The DCIRs open and close by the bus tie switches on the
P5 electrical system control panel.
Main Hot Battery Bus
The main hot battery bus gets power from the main
battery and the main battery charger. Under some
conditions, the main battery charger operates as a 64
3 gives power to the main battery bus through the
contacts of the energized battery transfer relay. If
the dc bus 3 source loses power, the battery transfer
relay deenergizes and the main battery relay energizes.
The main hot battery bus then gives power to the main
battery bus.
APU Battery Bus
The APU battery bus gets power through RCCBs from three
possible power sources; the dc bus 3 source, APU hot
battery bus source, or the main hot battery bus source.
Under usual conditions, dc bus 3 gives power to the APU
battery bus through the contacts of the energized
battery transfer relay. If dc bus 3 loses power, the
battery transfer relay deenergizes and the main battery
relay energizes. The APU hot battery bus then givespowers to the APU battery bus.
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747 TRAINING MANUAL
ELECT PWR -- DC GENERATION - DC POWER SYSTEM
The APU battery bus can also get power from the main
hot battery bus. During an APU start on an airplane
with no power, the APU transfer relay energizes and
connects the main hot battery bus to the APU battery
bus. This is to make sure that the decrease in voltage
on the APU hot battery bus (caused by the APU startermotor) does not have an effect on the APU control
circuits on the APU battery bus.
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- 186 -
747 TRAINING MANUAL
INVERTER
DCCS
DCIR
DC
DC BUS 3
TRUTRUTRU
APU BATXFER RLY BUS XFR
2 3LOADS
APU HOT BAT BUSAPU
DCCS APU BATCHARGER
BATAPU BAT BUS
RCCB
1
DCCS
DCIR
DC
DC BUS 2
LOADS
RCCB
DCCS
DCIR
DC
DC BUS 1
LOADS
RCCB
TRU4
DCCS
DCIR
DC
DC BUS 4
LOADS
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ELECT PWR - DC GENERATION - DC POWER SYSTEM
APU STAT
TO APU
RCCB
MAIN HOT BAT BUSMAIN
DCCS MAIN BAT
TO AC
STATIC
MAIN BATBAT RLY
INVERTER
XFR RLY
CHARGER
BAT
INVERTER
XFER RLY
STANDBY BUS
BUS XFRRELAY
STANDBY BUS
CHARGER
RCCB
RCCB
RCCB
MAIN BAT BUS
RCCB
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747 TRAINING MANUAL
General
The controls for the dc system are on the electrical
system control panel in the flight deck. These controls
are the battery switch, bus tie switches and standby
power switch.
Battery Switch
The battery switch is a latch type switch; push in
(latched on), push out (latched off). With the battery
switch latched in the ON light in the switch comes on.
With the battery switch out the OFF light comes on.
Bus Tie Switch
Operation to the latched in position enables automatic
ELECT PWR -- DC GENERATION - DC CONTROL
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Operation to the latched in position enables automatic
operation of the bus tie breaker and the dc isolation
relay. Operation to the out position opens the BTB and
the dc isolation relay.
Standby Power Switch
The standby power switch is a rotary-type, three-
position switch. With the switch in AUTO or OFF the hot
battery bus sources give power to their related battery
buses only with a loss of power from the dc bus 3
source. If you put the switch to BAT, the hot battery
bus sources give power to their related battery buses.
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747 TRAINING MANUAL
wAUTO
ISLNa
BUS
TIEw
AUTO
ISLNa
wAUTO
ISLNa
wAUTO
ISLNa
L - UTILITY - R
EXT PWR 1 APU GEN 1
ON
OFF
BATTERY
ONw
a
w w
AVAIL
OFF
ONw
a
OFF
ONw
aON
w
AVAIL
ON
w w
AVAIL
ON
w
AVAIL
APU GEN 2 EXT PWR 2
APU
ONOFF STARTBAT
AUTOOFF
STANDBY POWER
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ELECT PWR - DC GENERATION - DC CONTROL
ELECTRICAL SYSTEM CONTROL PANEL (P5)
DRIVE
w
a
w
a
ON
OFF
1 32
GEN
CONT
DRIVE
DISC
BUS
DRIVE
w
a
w
a
ON
OFF
BUS
DRIVE
w
a
w
a
ON
OFF
BUS
DRIVE
w
a
w
a
ON
OFF
BUS
4
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747 TRAINING MANUAL
General
There are four inter-changeable 75 ampere TRUs on the
E30-2 equipment shelf in the forward right main
equipment center. All are static devices change three-
phase, ac power into 28 volts dc power for the dcbuses.
Forced air cooling is necessary when the TRUs supply
maximum output current. The units can operate at 25% to
30% of their maximum current with convection cooling
only.
ELECT PWR -- TRANSFORMER RECTIFIER UNITS - INTRODUCTION
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747 TRAINING MANUAL
P180 DCDISTRIBUTIONPANEL
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ELECT PWR - TRANSFORMER RECTIFIER UNITS - INTRODUCTION
FWD
INBD
E30
NOSE GEAR
TRU 1, 2,
EQUIPMENTRACK
WHEEL WELL
3 & 4
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747 TRAINING MANUAL
General
A DCCS is an electronic unit that senses dc current.
The DCCSs are in six locations in the airplane dc
system:
- Four in the P180 to monitor TRU output current
- One at the main battery to monitor main battery
current
- One at the APU battery to monitor APU battery
current.
Function
The DCCSs do these functions:
Gi TRU t d t t th GCU d BCU f
DC CURRENT SENSORS (DCCS) --
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- Gives TRU current data to the GCUs and BCUs for
indication on the EICAS maintenance page
- Gives TRU current data to the GCUs and BCUs for TRU
malfunction indication on EICAS and triple channel
autoland operation
- Gives battery current data to the BCUs for
indication on the EICAS maintenance page andbattery discharge indication at an advisory level
on EICAS.
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747 TRAINING MANUAL
(4) (1)
P180 DC AFT
APU
CLOSET
DISTRIBUTIONPANEL
BATTERY
LEFTDOOR 5
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DC CURRENT SENSORS (DCCS)
FWD
INBD
FWDINBD
(1)
NOSE GEAR
MAIN
CLOSET
WHEEL WELL
BATTERY
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747 TRAINING MANUAL
General
Remote control circuit breakers (RCCB) are in P180 and
P183. The RCCB is a circuit breaker that uses a remote
1/2 ampere circuit breaker for control and indication.
The 1/2 ampere circuit breakers are in the flight deck.When the RCCB senses an overload, it opens the circuit
internally and opens the breaker in the flight deck.
You push in the flight deck circuit breaker to reset
the RCCB. The physical position of the RCCB shows in a
window on it as a red flag (closed) or a green flag
(open).
ELECT PWR -- AC ELECT LOAD DISTRIBUTION - REMOTE CONTROL CIRCUIT BREAKERS
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747 TRAINING MANUAL
P180 DC
E30
P183
DISTRIBUTIONPANEL
DISTRIBUTIONPANEL
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ELECT PWR - AC ELECT LOAD DISTRIBUTION - REMOTE CONTROL CIRCUIT BREAKERS
RCCB
POWER LOAD
DOORGREEN (OPEN)
(P6)
RED (CLOSED) 5L
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747 TRAINING MANUAL
General
The four dc buses get power from four 75 ampere TRUs.
The GCUs monitor voltage and current from the TRUs.
Each TRU can be in parallel with the others through the
contacts of a dc isolation relay (DCIR). The DCIRs openand close with the bus tie switches (P5).
DC Bus Power
The dc buses can get power from their related TRU or
from the other TRUs through the dc isolation relays.
Each TRU gets 3-phase, 400 Hz, 115 volts ac power from
its ac load bus. The TRU changes the 115 volts ac to 28
volts dc.
DCIR Control
ELECT PWR -- DC GENERATION - DC BUS CONTROL
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Each DCIR gets manual control from its related bus tie
switch in the flight deck or automatic control from its
related GCU when there is an autoland mode request.
With the bus tie switch in the isolation position 28
volts goes to energize the DCIR. This isolates the dcbus.
When the GCU gets an autoland request from the BCUs and
3 or more IDGs are available, the GCU energizes the
DCIR and isolates the dc bus. The two BCUs monitor the
auxiliary contacts of the DCIRs for an indication of dc
bus isolation.
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747 TRAINING MANUAL
DCCS
TO OTHER
TO
RCCB
R7219 DC
EIU
BCU 2
BCU 1TRU 1
DC BUS 1
+28V DC
AUTO
BUS TIE SW (P5)
P6
TRANSFORMER
115V AC
ISLN
BUS 1
RECTIFIERUNIT 1
(E30-2) (P180)
(P180)
DC LOADS
ISOLATION(P180)
DCIR
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ELECT PWR - DC GENERATION - DC BUS CONTROL
+28V DC
BCU 1
NOTE: SYS 1 SHOWNTRU 2, 3, AND 4 SIMILAR
GCU 1
3 IDGS
3 IDGS
AUTOLAND MODEAVAILABLEBCU 1
AVAILABLEBCU 2
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747 TRAINING MANUAL
General
To find if a TRU has a malfunction the GCU first does a
check to see if the DCIR is open or closed.
If the DCIR is open (dc bus isolated), the GCU looks atthe dc bus voltage to find if it is less than 18 volts
and TRU current is less than 2.5 amperes.
If the DCIR is closed, the GCU only looks at TRU
current to find if it is less than 2.5 amperes. It does
not look at dc bus voltage because the voltage on the
bus could be from a different TRU.
When one of these two conditions is true and therelated ac bus has power and the DCCS is in operation,
a digital TRU fail signal goes to BCU 1 and 2. BCU 1
(BCU 2 if BCU 1 has a malfunction) causes ELECT TR UNIT
ELECT PWR -- TRANSFORMER RECTIFIER UNITS - FAILURE INDICATION
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to show on the EICAS status page. This message shows
that the TRU has a malfunction.
- 198 -
747 TRAINING MANUAL
TRU 1 DCCS
ELEC TR UNIT 1
DC BUS 1
EIU
TRU 1
TRU DC VOLTS <18
DC CURRENT <2.5
DCIR OPEN
(E30-2) (P180)VOLTAGE(P180)
VOLTAGECURRENT
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ELECT PWR - TRANSFORMER RECTIFIER UNITS - FAILURE INDICATION
EICAS STATUS PAGE
GCU 1
NOTE: TRU 1 SHOWN
BCUBCU1 2
TRU FAILED
FROM
DCIR CLOSED
AC BUS 1 POWERED
DCCS NOT FAILEDOTHER GCU(S)
TRU 2, 3, AND 4
SIMILAR
- 199 -
747 TRAINING MANUAL
General
The main and APU battery buses usually get power from
dc bus 3 through the contacts of the energized battery
transfer relay (R7224). If a condition occurs that
deenergizes the battery transfer relay, the mainbattery relay energizes. This connects the main and APU
battery buses to their related hot battery buses for dc
standby power.
Battery Transfer Relay
Power from dc bus 3 energizes the battery transfer
relay. The power goes through the contacts of the
energized dc voltage sense relay (R7228) and thecontacts of the deenergized single TRU operation relay
(R7225). The battery transfer relay deenergizes when:
P i l t f d b 3
APU Battery Bus Transfer Relay
During an APU start the APU battery bus transfer relay
(R7687) energizes. If the main battery relay energizes
(such as on an airplane with no power), the main hot
battery bus connects to the APU battery bus. This isdone to make sure that the decrease in voltage on the
APU hot battery sources (caused by the APU starter
motor) does not have an effect on the APU control
circuits on the APU battery bus.
ELECT PWR -- BATTERIES - MAIN/APU BATTERY BUS POWER
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- Power is lost from dc bus 3 sources
- The standby power switch is in the BAT position
(this causes the dc voltage senses relay to
deenergize and remove power from R7224)
- The single TRU operation relay energizes (if one
of the two BCUs sense only one TRU in operation,R7225 energizes and removes power from R7224).
Main Battery Relay
The main battery relay (R7223) gets power from the main
hot battery bus sources. With the battery switch on and
the battery transfer relay deenergized the main battery
relay energizes and connects the main and APU hot
battery buses to their related battery buses.
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747 TRAINING MANUAL
General
The BCUs use the single TRU operation relay (R7225) to
control the battery transfer relay (R7224). When one of
the two BCUs sense that only one TRU is in operation,
the single TRU operation relay energizes. Thisdeenergizes the battery transfer relay and removes the
main and APU battery bus loads from the one TRU.
Operation
The DCCSs sense the current output of the four TRUs.
This data goes to the related GCU. If the GCU finds
that the output of the TRU is less than 2.5 amperes, it
sends a TRU fail signal to the BCUs. When one of the twoBCUs find that only one TRU is in operation, the single
TRU operating relay energizes.
ELECT PWR -- TRANSFORMER RECTIFIER UNITS - SINGLE TRU OPERATION
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- 202 -
747 TRAINING MANUAL
TRU TRU FAIL
TRU
DCCSARINC
GCU 1
ARINCSINGLE
TRU FAIL
GCU 2 GCU 3 GCU 4
FAILLOGIC
429XMITTER
429RECEIV
TRU
DC BUS 1
DC BUS 3
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ELECT PWR - TRANSFORMER RECTIFIER UNITS - SINGLE TRU OPERATION
R7228 DC
R7225 SINGLE
R7224
BCU 2
BCU 1 VOLTAGESENSE (P6)
TRU OPERATION
(P180)
BAT. XFR(P180)
RECEIV-ERS
LOGICDC BUS 3
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747 TRAINING MANUAL
R7219 - R7222
DC CURRENT
P180
RCCB
RCCB
DC ISOLATIONRELAYS
SENSORS
P180 DC
FWD
DISTRIBUTIONPANEL
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ELECT PWR - DC GENERATION - P180 INSTALLATION
OPTIONAL BATTERY OR
OPTIONAL BATTERY POWERED
P180-1 DC
R7224 BATR1195 TOWING
R8154 TOWING
R7223 MAIN
R7225 SINGLE TRU
R7687 APU BAT
DISTRIBUTION PANEL
BUS XFER RELAY
POWER XFER
TOWING BUS
GHB POWERED TOWING BUS OPERATION RELAY
GHB/BAT XFERCONT
XFER RELAY
BAT RELAY
1
2
2
1
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747 TRAINING MANUAL
General
The main battery is in the forward right main equipment
center. The APU battery is aft of the 5L door on the
E33-2 equipment rack. These are 40 amp-hr, 24 volt dc
nickel-cadmium batteries. Natural convection removesheat from these batteries. They have a vent into the
related equipment center. Each battery has:
- case
- cover
- twenty cell assemblies
- temperature sensor assembly.
The sensor assembly includes a thermoswitch and acharge control thermistor. The thermoswitch removes
power to the battery charger if the battery temperature
goes above safe operation limits. The charge control
thermistor gives a signal to the battery charger to
ELECT PWR -- BATTERIES - MAIN/APU BATTERY
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control the charge in relation to the battery
temperature.
The APU battery ground is a dual ground configuration
connection connected to a bracket on the airframe.Other electrical components in the aft equipment center
having similar connections are the APU battery charger
and TRU.
NOTE: To prevent possible arcing or overheating at the
ground, maintenance procedures require these
connections be properly torqued.
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747 TRAINING MANUAL
APU BATTERY(E33-2 RACK)
APU TRU
APU BATTERYCHARGER SEEPANEL
DISTRIBUTIONP180 DC
RACKEQUIPMENTE30
DUAL GROUNDCONFIGURATION(TYPICAL)
WIRE
LUG
BRACKET
DUAL GROUND
A
A
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ELECT PWR - BATTERIES - MAIN/APU BATTERY
NO. 5L MAINENTRY DOOR
AFT EQUIPMENT CENTER (E8)
BATTERYMAIN
INBD FWD
WHEEL WELLNOSE GEAR
FWD
INBD
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747 TRAINING MANUAL
General
The main battery charger is on the E30-2 shelf in the
forward right main equipment center. The APU battery
charger is aft of the 5L door on the E33-1 equipment
rack. These chargers have two different functions. Theygive a dc output to charge the related battery and
operate as a TRU during some conditions.
The battery chargers get forced air cooling and are
inter-changeable. AC power for the charger comes from
the ground service bus.
Charge Mode
In the charge mode, the battery charger starts the
battery charge cycle in the constant current mode (38
amperes). As the battery charges, the output voltage
increases with the battery condition of charge and load
i t At th t t it i 28 lt d ith th
TR Mode
In the TR mode, the charger supplies a constant 27.75v
dc up to 64 amperes. This voltage keeps the battery
charge with minimum electrolyte loss.
Charger Off
The battery charger goes off for these conditions:
- Battery connector off when power connected
- Battery interlock open (small connector off)
- Overcurrent (internal fault)
- Battery overtemperature
- Loss of input power- Input ac voltage more than 134 volts or less than
94 volts.
ELECT PWR -- BATTERIES - MAIN/APU BATTERY CHARGER
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resistance. At the start, it is 28 volts dc with the
current at 38 amperes. As the battery charge increases,
the output voltage increases until it gets to the
inflection voltage. The inflection voltage changes with
battery temperature but is 31v dc at normal ambienttemperatures. At the inflection voltage, the battery
voltage continues to increase during an overcharge
period. The quantity of overcharge is percentage (12%)
of the time necessary for the battery to get to the
inflection voltage. The battery charger then changes to
the constant potential mode of 27.75 volts dc. In the
constant potential mode, there is a current limit of 38
amperes.
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747 TRAINING MANUAL
Operational Test
The following is a battery charger test for the APU
battery charger: (Main battery charger test is
similar.)
- Proper operation of an APU battery charger can be
verified by observing a charge cycle. A new charge
cycle is initiated when input power is removed for
more than 500 MSEC and then reapplied. When an APU
battery is replaced, the charge cycle will be
initiated by the opening and closing of circuit
breaker /APU BAT CHGR/ on the P183 panel. On the
EICAS ELEC MAINTENANCE page, the APU BAT current
will indicate /CHG/ with 31 to 43 AMPS. APU batteryvoltage will start at 27 to 29 volts, rise to 31
volts as the battery state of charge increases,
then drop to 28 volts. When the voltage drops to 28
volts, the current also reduces to /CHG/ or /DIS/
of 0 to 5 amps
minimum battery voltage is 4 volts dc to initiate the
charge cycle.
Charger Off
The battery charger turns off under the followingconditions:
- Battery connector off when power applied
- Battery interlock open (small connector off)
- Overcurrent (internal fault)
- Battery over temperature
- Loss of input power
- Input ac voltage over 134 volts or under 94 volts.
ELECT PWR -- BATTERIES - BATTERY CHARGER CHARGE MODE
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of 0 to 5 amps.
NOTE: The state of charge of a nickel-cadmium battery
cannot be determined by measurement of battery
voltage. With the exception of dead batteries,the voltage at both open circuit and under load
conditions do not significantly vary with respect
to state of charge. The only dependable method to
determine a battery's state of charge is through
a measured complete discharge.
The battery charger is capable of fully recharging a
battery within a 75 minute time period, provided the
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747 TRAINING MANUAL
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ELECT PWR -- BATTERIES - MAIN HOT BATTERY BUS POWER
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747 TRAINING MANUAL
ELECT PWR -- BATTERIES - MAIN HOT BATTERY BUS POWER
in the MEC. For this condition the battery charger does
not go into the constant current charge mode so that it
does not release gas into the MEC.
Charger Failed
A charger malfunction signal goes to BCU 1 when:
- The interlock opens (small connector off)
- The battery temperature is more than 63C
- There is no input power.
NOTE: The battery charger does not turn on unless the
battery voltage is above 4 volts when power is
first applied to the battery charger.
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747 TRAINING MANUAL
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ELECT PWR -- BATTERIES - APU HOT BATTERY BUS POWER
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747 TRAINING MANUAL
ELECT PWR -- BATTERIES - APU HOT BATTERY BUS POWER
deenergizes, or the two primary and secondary
lavatory/galley vent control relays deenergize. When
the battery transfer relay deenergizes, or the APU
inverter relay energizes, the higher current limit is
available to supply the APU battery bus loads. If the
two lavatory/galley vent control relays deenergize, thebattery charger does not go into the constant current
charge mode so that it does not release gas around the
battery.
Charger Failed
A charger malfunction signal goes to BCU 2 when the:
- Interlock opens (small connector off)- Battery temperature is more than 63 C
- Input power is removed.
NOTE: The battery charger does not come on unless the
battery voltage is above 4 volts when power is
first connected to the battery charger
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first connected to the battery charger.
- 218 -
747 TRAINING MANUAL
APU BAT
R7498 PRI LAV-GLY
R1434 APU INV
APU BAT
R7218 APU BATP183
28V DC APU
115V AC
APU HOT
- LOSS OF POWER- BAT TEMP >63C- CONNECTOR OFF BAT CHARGER
CONT
- 28V DC CONSTANT
- 28V DC CONSTANT
- 38A CONSTANT
APU BAT
P183
DC
RCCB
GSB XFR
CHARGER
OVHT PROT
(P183)
XFR (P183)
VENT CONT (E8)
CUR CHARGE
POTENTIAL 38A
POTENTIAL
MALFUNCTION
CHARGEROUTPUT
BAT BUS
(P183)
LOADS
TO BCU 2
LIMIT
64A LIMIT
HOT BAT BUS
R7188 APUSTART (P83)
1
CHARGER DISABLE
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ELECT PWR - BATTERIES - APU HOT BATTERY BUS POWER
DCCS
STANDBY PWR SW (P5)
OFF
AUTO
BAT
TO
T
-
+
APU BATTERY
69C59C
INTER-
BCU 2
LOCK
APU BAT CHARGER(E33-2)
R7224 BAT XFR (P180)
R7498 SEC LAV-GLYVENT CONT (E8)
1 ENERGIZED DURING APU START
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747 TRAINING MANUAL
60 SEC
BAT TEMP
OPEN = 1
BAT CHARGER MAINCHARGER
AUTOOFF
BAT
STANDBY PWR
BATTERY CHARGER
INTERLOCK OPEN
LOSS OF
BAT CHARGER APU
SW (P5)
TD
>63C
INPUT PWR
MALFUNCTIONARINC429XMTR
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ELECT PWR - BATTERIES - MAIN/APU BATTERY CHARGER FAILURE INDICATION
EIU
EICAS STATUS PAGE
GSB
- MAIN BATTERY CHARGER - BCU 1
BCU
- APU BATTERY CHARGER - BCU 2
TD
POWERED
- 221 -
747 TRAINING MANUAL
General
A DCCS senses battery current. This sensor is on the
battery ground wire adjacent to the battery. Current
data from this sensor goes to BCU 1 for the main
battery and BCU 2 for the APU battery. When the BCU
finds a battery discharge of two amperes or more, it
tells the EIUs to show the advisory message BAT DISCH
APU or BAT DISCH MAIN. Logic circuits in the EIUs make
the decision when to show the messages. This includes
an APU start inhibit for BAT DISCH APU and possible
time delays necessary for the message.
ELECT PWR -- BATTERIES - MAIN/APU BATTERY DISCHARGE INDICATION
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O Æ
致 獨 鐘 ~
MAINTENANCE
TRAINING
M NU L
APU
TRU
The
APU t r ansformer
r e c t i f i e r
un i t
TRU)
i s an l t e r n dc power source
for
s t a r t i n g
the APU.
The un i t
cons i s t s
of a
cool ing
fan ,
power
t r ansformer
, thermal
switches and
two
three phase f u l l wave
r ec t i f i e r s .
The
TRU produces 28 vo l t s dc from
an
input
h r e e p h s e
400
Hz
,
115
vo l t s
ac.
The TRU i s in the e q u i p m e n t cen te r .
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747
FEB 11/93
--\
24.32.504.003
AGE
2
PAGE 223A
AFT LEFT
DOOR
5
E33-1
EQUIPMENT
R CK
~
NEGATIVE
C
POSITIVE
C
INBD ~
UNITECTIFIER
R N S F O R
PU
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24.32 .004 .003
PAGE
275
APU TRU
747
JAN 05/93 PAGE 223B
O Æ
W 間
MAINTENANCE
TRAINING
M NU L
APU TRU
POWER
The APU TRU i s used for APU s t a r t i n g
power when the
APU s t a r t
source swi tch
on
P461
i s in
TR
dur ing an APU s t a r t .
AC power
for
the
APU
TRU
i s
suppl ied
from AC
Bus
4 th ru t he
u t i l i t y
ELCU 4 ,
and t he r i gh t u t i l i t y swi tch
placed
in
t he ON
l l l
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747
AUG 13/97 PAGE 223C
24.32.506.002
PAGE
276
\
--\
\
E33-1)
TRU
R700
GALLEY/
TRU
XFER P30)
APU
SW
RIGHT
UTILITY
APU
SOURCE
BATTERY
@
APU
ON
O?@ RT
APU
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ELCU
4
P5
24.32.006.002
PAGE 277
POW R
PU TRU
29/97
PAGE 223D
747
AUG
H Æ W 唔 ~
I N T E N N E
TRAINING
M NU L
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747
SEP 10/87 PAGE 223E
r:
( ì
00.00.001.
001
PAGE
278
r .
H D ~ w ~ 7
MAINTENANCE
TRAINING
M NU L
APU TRU OPERATION
旦 旦 旦 旦 主 主
The
APU
TRU
i s
in the a f t e q u i p m e n
cen te r on
the
she l f . Three-phase
115 ac
power i s suppl ied to the
TRU from
the
u t i l i t y ELCU in P414.
Wh
en us ing the TRU
to
s t a r t the
APU ,
power
i s
t r ans fer red
f r o m h e u t i l i
Y
bus
to the APU TRU. with power
app l i ed
the TRU supp l i e s 28 vo l t s dc d i r e c t l y
to
the APU s t a r t e r
motor.
To
APU TRU
for s t a r t i n g the
APU , power must be ava i l ab le on the GSB
and on main ac bus No. 4
,
and
the
r i gh t
u t i l i t y bus switch
la tched
on.
TRU s t a r t s a re
accomplished by plac ing
APU s t a r t
source
se l ec t
P461)
to
TR
and
ro t a t i ng
the
APU
master
control
s w i t c h START.
During s t a r t with
u t i l i t y
4
power ava i l ab le the
ac
power sense-TRU
APU s t a r t r e l ay R8225) energized.
This arms the t r a n s f e r c i r c u i t .
At
the
same t ime
the
APU-TRU
t rans fe r
re l ay
R8204) i s energized arming
the
APU
s t a r t and TRU
l a t ch
re l ay r c u i t s
With a TRU s t a r t se lec ted
the
APU
TRU
d isab le
r e l ay R8203) i s
also
energized . This
u a l l y
d isab le s the
APU b a t t e r y
c i r c u i t and
ac t iva t es
the APU TRU s t a r t r c u i t
The
galley/TRU
t rans fe r
r e l ay R700)
i s
energized through R8203. This
t r an s f e r s u t i l i t y
4 ga l l ey power to
the
APU
TRU. The output of the APU TRU
i s
c o n n e c d i r e c t l y to
the
APU
s t a r t e r
motor.
Energiz ing
R700 causes the
r e l ay R704) to energize .
connects ground service ac
APU
TRU cool ing
fan.
APU TRU
This
power to the
Wh en
the
APU i s completed, power
i s
t r ans fer red
from
the
TRU back
to the
ga l l ey .
Protec t ion
r i n g an APU TRU
s t a r t the
TRU
cool ing
fan
i s
always r u n n i n g the TRU
tempera ture exceeds 50
o
C
, the
cool ing
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747
NOV 28/94 PAGE 223F
fan s tays on un t i l e m p e r a t u r e
lowers.
24.32.505A.002
PAGE 279
Æ 致 W G
M INTEN NCE
TR INING
M NU L
王 旦 主 豆 豆 且
cont)
the TRU
tempera ture exceeds
12 0
o
C
,
the APU TRU
l a t ch
re l ay R8202) i s
energized . This disarms the APU TRU
c i r c u i t
t r ans fer r ing
s t a r t e r
motor
power
to
the
APU bat t e ry .
R8202
remains
energized as
long
as
the
APU
TRU
tempera ture
i s above
12 0
0
C or the
APU
i s
s ta r t ing .
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747
NOV
28/94 PAGE 223G
2 4 . 3 2 . 5 5 B . 0 0 2
PAGE
280
1)
f
DC
PWR
TO APU
STARTER
O T O R
f
f 九
APU
BA
T.
TO
LOAD
APU
TRU
斗
E33-1
OVERHEATRU
PU
120
0
C
訂
已
ι 一 ÷ →
UTIL
B
BUS 4
P414)
28V
DC
BAT.
BUS APU TRU
CONTROL
R8204 APU
TRU
XFR
DURING
江 百
午 址
1 1
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P183)
b i l i R ; ; 需
需 可 言 : : E
〉
斗
3 2 5 2
PAGE 281
APU TRU
OPERATION
P461)
13/94 PAGE 223H
747
DEC
747 TRAINING MANUAL
General
The ac standby power system gives power to flight
critical loads if there is a loss of airplane
electrical power. The system has these components:
- Transfer relay- AC standby bus
- Static inverter
- Control switch.
The flight critical loads connect to the ac standby
bus, which receives power from ac bus 3 or the static
inverter. Manual control of the static inverter is from
the standby power switch on the electrical system
control panel in the flight compartment.
ELECT PWR -- AC STANDBY PWR GENERATION - INTRODUCTION
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- 224 -
747 TRAINING MANUAL
STANDBY POWER
OFFAUTO
BAT STANDBY POWER
ELECTRICAL SYSTEM
CONTROL
TRANSFER RELAY(P6)
CONTROL PANEL (P5)
AC BUS 3AC STBY
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ELECT PWR - AC STANDBY PWR GENERATION - INTRODUCTION
STATIC INVERTER(E30-2)
- 225 -
747 TRAINING MANUAL
General
The position of the standby power switch causes manual
or automatic control of the ac standby power system.
The static inverter always has power but is not always
on. When it gets an on command, the static inverter
gives power to the ac standby bus.
Automatic Operation
When ac bus 3 has power, and the standby power switch
is in AUTO, the standby power transfer relay energizes.
This connects ac bus 3 to the ac standby bus. Another
set of contacts in the relay puts a ground on the
remote control lead of the static inverter. This keeps
it off. If ac bus 3 loses power, the standby powertransfer relay deenergizes. This connects the ac
standby bus to the output of the static inverter and
removes the ground from the remote control lead. The
static inverter comes on and supplies 115 volts ac
power to the ac standby bus.
Manual Operation
deenergizes and R7223 energizes. This connects the
inverter to the main hot battery bus. The static
inverter then gets power from the battery and gives
power to the ac standby bus.
ELECT PWR -- AC STANDBY PWR GENERATION - OPERATION
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Manual Operation
If you put the standby power switch to OFF, a ground onthe remote control lead keeps the static inverter off.
If you put the standby power switch to BAT, the standby
power relay deenergizes. This causes the static
inverter to come on and moves the inverter's 28 volts
dc input power. Under usual conditions R7224 contacts
are closed. This gives the static inverter power from
dc bus 3. With the standby power switch in BAT R7224
- 226 -
747 TRAINING MANUAL
REMOTE CONTROL
115V AC
M7438 STATIC
115V AC
AC 3 STANDBY
STANDBY
AC STANDBY BUS
28V DC
R7223 MAIN
R7224 BATTERY
MAIN HOT
DC BUS 3
BAT. BUS
BATTERY (P180)
TRANSFER (P180)
INVERTER (E30)
(GND = OFF)
BUS 3
POWER
TRANSFER RELAY
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ELECT PWR - AC STANDBY PWR GENERATION - OPERATION
OFF
AUTO
BAT
STANDBY POWER
P6 R7227 STANDBY
TRANSFER RELAY
SWITCH (P5)
POWER TRANSFER(P6)
- 227 -
747 TRAINING MANUAL
General
The APU static inverter provides power for the left FMC
and the captain's integrated display units (IDU) in the
event of a power loss to the captain's transfer bus.
The output of the static inverter is connected to the
PFD-L, ND-L and the FMC-L through the relaxed contactsof the transfer relay.
NOTE: Circuit diagrams refer to the captain's outboard
IDU as the left primary flight display (PFD-L)
and the captain's inboard IDU as the left
navigation display (ND-L).
ELECT PWR -- AC STANDBY PWR GENERATION - APU STATIC INVERTER POWER
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- 228 -
747 TRAINING MANUAL
CAPT XFER
CAPT PFD-LEFT
APU HOT
TO STANDBYPOWER SW
BAT. BUS
XFER BUS
RELAY (P6)
ND-LEFTFMC-LEFT
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ELECT PWR - AC STANDBY PWR GENERATION - APU STATIC INVERTER POWER
APU STATIC INVERTER
R1434 APU
E8
INV XFR(P183)
POWER SW
(P5)
- 229 -
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747 TRAINING MANUAL
APU STATIC
C10680 APU STBY
PFD-L
ND-L
FMC-L
24V DC GND=OFF
APU HOT
CONT
C10416
C10412
CONT
R1434 APU
BAT. SW
BAT.
OFF
AUTO
R7188
R7853
C10415
APU INVRLY PWR
(P183)
APU INVPWR (P183)
BAT. BUS
INV XFER(P183)
INVERTER (E8)
ALT PWR (P6)
APU START(P83)
APU STBY
APU STBYXFR PWR(P6)
(P5)
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ELECT PWR - AC STANDBY PWR GENERATION - APU BATTERY STBY PWR - OPERATION
CAPT XFER BUS
AC BUS 3
AC BUS 1IBVSU
STANDBY POWERSWITCH (P5)
BUS XFER(P6)
- 231 -
747 TRAINING MANUAL
General
Two instrument bus voltage sense units (IBVSU) in P6
provide automatic transfer of the captain's and first
officer's flight instrument transfer buses. The IBVSUs
transfer the associated flight instrument transfer
buses from their primary source to ac bus No. 1 if theprimary source voltage drops below 97 volts for 180 ms.
The instrument buses primary sources are ac bus No. 2
for the first officer and ac bus No. 3 for the captain.
Return to the primary source takes place when the
primary source recovers to 106 volts for 1.2 seconds.
Control power for the IBVSUs comes from dc bus No. 1.
If this control power is lost for 20 ms or longer, the
associated IBVSU remains in or returns to its primary
position.
ELECT PWR -- AC PWR DISTRIBUTION - INSTRUMENT BUS VOLTAGE SENSE UNITS
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- 232 -
747 TRAINING MANUAL
LOW
LOW
AC-F/O XFR
POWER
M7508 (P6)
POWER
P6
CAPT XFER
28V DC
F/O XFER
28V DC
AC 1
AC 2
AC-CAPT XFRAC 3
BUS 1
BUS CONT
BUS 1
BUS CONT
SUPPLY
VOLTAGESENSING
SUPPLY
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ELECT PWR - AC PWR DISTRIBUTION - INSTRUMENT BUS VOLTAGE SENSE UNITS
LOW
M7507 (P6)
VOLTAGESENSING
- 233 -
747 TRAINING MANUAL
General
The basic electrical power distribution system has
power control components and functions that aid the
basic electrical power system. These include:
- Electrical load control units (ELCUs) that controlpower to the galleys and utility buses
- Autoland isolation that gives automatic bus
isolation during autoland operations.
ELECT PWR -- AC ELECT LOAD DISTRIBUTION - INTRODUCTION
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- 234 -
747 TRAINING MANUAL
AUTOLANDISOLATION
DISTRIBUTION
ELCU
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ELECT PWR - AC ELECT LOAD DISTRIBUTION - INTRODUCTION
LOADMANAGEMENT
- 235 -
747 TRAINING MANUAL
General
There are eight ELCUs used for load distribution. Two
each are in P514, P614, P515, and P615. Four are used
for the galleys and four for the utility load buses.
Each ELCU has internal circuits for control and
indication and for differential fault and overcurrentprotection.
ELECTRICAL LOAD CONTROL UNIT (ELCU) --
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- 236 -
747 TRAINING MANUAL
P614P514
P615
P515
UTILITY
GALLEY
AC BUS
ELCU
ELCU
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ELECTRICAL LOAD CONTROL UNIT (ELCU)
- 237 -
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747 TRAINING MANUAL
FROM
O
S
POWER
S
P5
KVA
AC BUS LOAD
R
OVER CURRENT DIFF FAULT
BCU 1 OR BCU 2
28V DC
ELCU
UTILITY
OFF
RL
OFF
ONON
JUMPER
LOADCT(S)
POSITIONTO BOTHBCU(S)
FROMBCU 1(BCU 2)
PROTECTION PROTECTION
SUPPLY
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ELCU OPERATION
BCU 2
P180
DC BUS
TO BCU(S) FOR
ELCU
ELCU CONTROL(BCU 1)
POWER
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747 TRAINING MANUAL
THIS PAGE INTENTIONALLY LEFT BLANK
LOAD MANAGEMENT SYSTEM --
LOAD MANAGEMENT SYSTEM --
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- 240 -
747 TRAINING MANUAL
LOAD MANAGEMENT SYSTEM --
General
The load management system automatically disconnects
and connects the galley and utility loads. When the
system senses an overload condition because demand is
more than capacity, the system opens and closes ELCUs.
Load Shed
During an overload condition, the load management
system opens the applicable galley ELCUs one at a time
in one-second intervals until the overload condition
goes away. The galley load shed is in this order:
- G ELCU 1- G ELCU 4
- G ELCU 2
- G ELCU 3.
If the overload condition stays after all the galleys
disconnect, load shed continues in one-second intervals
with the utility ELCUs until the overload goes away.
The utility load shed is in this order:
an overload occurs on the remaining paralleled
generators, this is the trip sequence:
- G ELCU 1
- G ELCU 4
- G ELCU 3- U ELCU 1
- U ELCU 4
- U ELCU 3.
Load Restoration
Load restoration occurs in the opposite order as load
capacity increases. This is the order of load
restoration:
- One or no generators - no load restoration
- Two generators - restoration of utility loads and
G ELCU 3
- Three or four generators - restoration of all
loads.
Load restoration for APU and external power occurs as
l d it i
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- U ELCU 1
- U ELCU 4
- U ELCU 2
- U ELCU 3.
When a generator is isolated (BTB open), and there is
an overload on the remaining generators, load shed
starts with the lowest numbered G ELCU or U ELCU if all
the galleys are off. For example, if BTB 2 is open, and
load capacity increases.
IDG Load Management
Generator load sense is from current transformers (CTs)
in the IDGs. The current sensed by these CTs goes to
their applicable GCUs. The GCUs send generator load
data to the BCUs by two paths, an ARINC 429 bus and
hard-wire. The hard-wire signals are redundant and are
for backup if there is a failure of the ARINC 429 bus.
- 241 -
747 TRAINING MANUALLOAD MANAGEMENT SYSTEM --
Normally closed relays are in the BCUs that supply
power and grounds to the ELCUs. BCU 1 gives power to G
ELCU 1 and 2 and to U ELCU 1 and 2. BCU 1 gives a ground
to G ELCU 3 and 4 and to U ELCU 3 and 4.
BCU 2 gives power to G ELCU 3 and 4 and to U ELCU 3 and
4. BCU 2 gives a ground to G ELCU 1 and 2 and to U ELCU1 and 2.
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- 242 -
747 TRAINING MANUAL
0
APU GEN 2
LOAD
POWER 28V DC
BCU 1
G ELCU 3
G ELCU 2
G ELCU 4
U ELCU 1
U ELCU 4
GCU 3
G ELCU 1
APU GEN 1
UTILITY
RIGHTLEFT
POWER
SWITCHES(P5)
EXT PWR 1CTS
EXT PWR 2CTS
IDGCT
GCU 2
GCU 1
IDG
REDUNDANT
CT
LOAD
SENSETO BCU(S)
IDGCT
GEN LOADS
LOAD
GROUND
28V DC
GEN LOADS
LOADMGTLOGIC
LOAD
MGTLOGIC
LOADSENSING
LOADSENSING
LOADSENSING
REDUNDANTLOADSENSETO BCU(S)
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LOAD MANAGEMENT SYSTEM
BCU 2
GROUND
U ELCU 2
U ELCU 3
GCU 4
IDGCT
GEN LOADS MGTLOGICLOADSENSING
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747 TRAINING MANUAL
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UTILITY LOAD MANAGEMENT --
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- 244 -
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747 TRAINING MANUAL
9 9
DC
LEFT
P180
DC
POWER
GROUNDEX PWR 1
APU GEN 1
EXT PWR 2
LOAD
SYSTEM
GEN LOAD
ON
OFF
BCU 1
BTB GCB SSB XPC
POWER
SYSTEM
GEN LOAD BTB GCB SSB XPC
EX PWR 2
APU GEN 2
U ELCU 1
UTILITY
UTILITYU ELCU 1
U ELCU 4
ON
BUS 1
BUS 1 CONT
BUS 4
BUS 2 CONT
UTILITYSW (P5)
FROM GCU1, 2, 3, 4
LOAD
LOAD
APU PWR 2LOAD FROMBCU 2
FROM GCU1, 2, 3, 4
LOAD
LOAD
CONFIGURATION
APB POSITION
APB POSITION
CONFIGURATION
MGTLOGIC
LOADMGT
LOGIC
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UTILITY LOAD MANAGEMENT
BCU 2
GROUNDEXT PWR 1OFF
RIGHTU ELCU 4UTILITY
SW (P5)
APU PWR 1LOAD FROMBCU 1
- 247 -
747 TRAINING MANUAL
General
Autoland isolation divides the airplane electrical
system into three isolated power sources. This is done
to give the three flight control computers (FCC)
isolated power sources when they are in an autoland
approach mode.
Operation
During a triple channel autoland the three FCCs send an
isolation request to BCU 1. BCU 1 makes the decision on
how to divide the electrical system. BCU 1 uses the
position of the BTBs, GCBs, and SSB and the operation
of the TRUs to make this decision. When BCU 1 makes a
decision on how to divide the system, it sends anisolation command to BCU 2 and the GCUs to open the
related BTBs and DCIRs. When these components are in
the correct position, BCU 2 sends a signal back to the
FCCs.
ELECT PWR -- AC ELECT LOAD DISTRIBUTION - AUTOLAND ISOLATION
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747 TRAINING MANUAL
9 9 9
ISOLATION
TRU
TRU
AUTOLAND
FCC (3)
BTB(S)
POSITION
POSITIONISOLATIONREQUEST
DCIR(S)
CONDITION
COMMAND
CONDITION
FCC
GCU(S) 1-4
BCU 1
DCCS 1-4
SSB
CONTROLCOMMANDS
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ELECT PWR - AC ELECT LOAD DISTRIBUTION - AUTOLAND ISOLATION
POSITIONISOLATION CONFIRMEDBCU 2
- 249 -
9
747 TRAINING MANUAL
General
After BCU 1 gets an autoland isolation request from the
FCCs, it finds the number of generators and TRUs that
are in operation. BCU 1 then sends signals to the
related GCUs to divide the electrical system in one offive possible configurations (A, B, C, D and E).
Autoland Request
If there are four generators and four TRUs in
operation, BCU 1 tells the GCUs to go to configuration
A. This is the usual configuration for triple channel
autoland. If more than one generator channel does not
operate, BCU 1 ignores the autoland request.
NOTE: One generator and one TRU is considered an
individual generator channel (GC) by the autoland
logic. For example No. 2 generator and No. 2 TRU
make up one generator channel.
If one GC does not operate, BCU 1 sets the system to
configuration B, C, D or E.
NOTE: The SSB or any BTB opened prior to the autoland
If more than one GC stops operation during autoland,
BCU 2 removes its signal to the FCCs. If the airplane
is above 200 feet at this time, the BTBs and DCIRs go
back to their positions before autoland. If the
airplane is below 200 feet, only the DCIRs close. AC
power isolation does not change. The BTBs remain in the
last configuration until the FCCs remove the autolandisolation request.
ELECT PWR -- AC ELECT LOAD DISTRIBUTION - AUTOLAND ISOLATION LOGIC
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NOTE: The SSB or any BTB opened prior to the autoland
isolation request will not be closed during the
autoland mode.
Autoland Operation
If a GC fails while in configuration A, BCU 1 changes
the system to configuration B, C, D or E.
- 250 -
747 TRAINING MANUAL
1 9 9 9
ABOVE
INOP
BTB(S) STAY
YES
INOP NO
YES
INOP NO
NO
YES
YES
NO
NO
NO
NO
NO
YES
YES
YES
YES
NO. 3 GEN
NO. 2 GEN
NO. 1 GEN
NO
IGNORE
RETURN ELECT
INOP
4 GEN
INOP
YES
NO
AUTOLAND REMOVE AUTO
AUTOLAND
YES
SET
SET
SET
SET
REQUESTFROM FCC
AND TRUSOPERATING
GC >1
CONFIG A
GC >0
GC >1CONFIG D
OR TRU INOP
OR TRU INOP
CONFIG C
CONFIG B
GC >1
GC >1
IN LASTPOSITION,REMAININGDCIRS CLOSE
REQUESTREMOVED
200FT
ISOLATIONCONFIRMATION
SYSTEM TOPRE-AUTOLANDCONFIG
AUTO ISOLREQUEST
OR TRU INOP
1
1
1
1
1
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ELECT PWR - AC ELECT LOAD DISTRIBUTION - AUTOLAND ISOLATION LOGIC
YES
INOP NO
YES
NO. 4
IF SSB IS OPEN
SET
AND GEN IS INOP,GO TO
TRU INOP
CONFIG E GC >11
1
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9 9
747 TRAINING MANUAL
General
There are five possible configurations that BCU 1 can
set for autoland isolation (A, B, C, D, and E). BCU 1
finds the number of generators and TRUs that are in
operation to make a decision which configuration to
use. These are the configurations and related generatoroperation:
- A all generators in operation
- B No. 1 generator not in operation
- C No. 2 generator not in operation
- D No. 3 generator not in operation
- E No. 4 generator not in operation.
The configuration for a TRU that does not operate isthe same as for a related generator that does not
operate except that the related GCB does not open.
The split system breaker must be in the closed position
for configurations B and C if the related GCB is open.
ELECT PWR -- AC ELECT LOAD DISTRIBUTION - AUTOLAND CONFIGURATIONS
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747 TRAINING MANUAL
/ 1 9 9 9
G1 G2 G3 G4
CONFIG A CONFIG B CONFIG C
BTB
GCB
TRU
DCIR
BTB
GCB
TRU
DCIR
SSB SSB
BTB
GCB
TRU
DCIR
SSB
BTB
GCB
TRU
SSB
BTB
GCB
TRU
SSBTRU INOP, CONFIGURES
SSB MUST BE CLOSED IN
GEN NO. 1 INOP GEN NO. 2 INOP
THE SAME AS GENERATORINOP EXCEPT THAT GCBDOES NOT TRIP.
CONFIGURATIONS B AND CIF RESPECTIVE GCB IS OPEN.IF RESPECTIVE GCB ISOPEN IN CONFIGURATION
D AND E, SSB MAYBE OPEN.
G1 G2 G3 G4 G1 G2 G3 G4
G1 G2 G3 G4 G1 G2 G3 G4
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ELECT PWR - AC ELECT LOAD DISTRIBUTION - AUTOLAND CONFIGURATIONS
CONFIG D CONFIG E
TRU
DCIR
TRU
DCIR
GEN NO. 4 INOPGEN NO. 3 INOP
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747 TRAINING MANUAL
2 / 1 9 9 9
ENG STAT
ECS
HYD DRS GEAR
ELEC FUEL
2 3 4
OFF
ISLN
BUS 1
BUS TIE
SSB
GEN CONT
DRIVE
BUS 2 BUS 4
UTILITY
GALLEY
UTILITY
GALLEY
UTILITY
GALLEY
UTILITY
APU 1EXT 1 EXT 2APU 2
DRIVE
PRESSTEMP/
GALLEY
BUS 3
1
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ELECTRICAL POWER - SYNOPTIC PAGE
EICAS DISPLAY SELECT
CANC RCL
PANEL (P10)
- 255 -
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747 TRAINING MANUAL
2 2 / 1 9 9 9
1
LOO RC TNEGP AE I C A S
D I S P L A Y
C M C M E N U
< P R E S E N T L E G F A U L T S
C ON FI DE NC E T ES T<
<
<
S
E I C A S M A I N T P A G E S
G R O U N D
H E L P >
T E S T S
/ 2
<
R E C O R D
<
<
M AN UA L S NA PS HO TS
A UT O S NA P SH OT S
1 E C S
4 E L E C
7 F L T
I C A S MM C = E I U
< 2
< 2
< 2
EC LL
1 / 3A I N T P A G E SE I C A S = E I U --
T R I C A L
C O N T
8 F U E L< 2
ELECTRICAL
28 28 28 28 28 28
35 35 35 35
APU BAT
DC-V
145
35 35
IDG OUT.TEMP
IDG RISE TEMP
115
400
115
400
115
400
115
400
AC-V
FREQ
LOAD
1APU 2 EXT 2
2 3 4
0.00 0.75 0.75
0
0
0.00
__________
10DC-A
MAIN BAT
CHG
0
0
APU 1
DIS
24
030
145 115
0
0
0.35 0.00
0
0
0.65
38
EXT 1
0.00
E LACIRTCEL
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ELECTRICAL POWER - MAINTENANCE PAGE ACCESS
AUXILIARY EICAS
< A UT O S NA P SH OT S
DATE GMT 18:54:0402SEP87
- 257 -
/ 1 9 9 9
747 TRAINING MANUAL
General
The electrical power maintenance page shows electrical
system ac volts, frequency and percent load for these
power sources:
- APU generators 1 and 2
- External power 1 and 2
- IDG 1, 2, 3 and 4
DC volts and amperes show for:
- Main battery
- TRU 1, 2, 3 and 4
- APU battery
Temperature (C) shows for oil outlet and rise of each
IDG.
Voltage indications for the APU are from the C phase.
For IDG and external power voltage, the highest phase
voltage shows.
For percent load indications the phase with the highest
current shows as a percent of 250 amperes.
ELECTRICAL POWER -- MAINTENANCE PAGE
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- 258 -
747 TRAINING MANUAL
/ 2 2 / 1 9 9 9
28 28 28 28 28 28
35 35 35 35
APU BAT
DC-V
145
35 35
IDG OUT.TEMP
IDG RISE TEMP
115
400
115
400
115
400
115
400
AC-V
FREQ
LOAD
1APU 2 EXT 2
2 3 4
0.00 0.75 0.75
0
0
0.00
ELECTRICAL __________
10DC-A
MAIN BAT
CHG
0
0
0.00
EXT 1 APU 1
DIS
24
030
145 115
0
0
0.35 0.00
0
0
0.65
38
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ELECTRICAL POWER - MAINTENANCE PAGE
DATE GMT 18:54:0402SEP87
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2 / 1 9 9 9
747 TRAINING MANUAL
General
The AGCUs sense three-phase voltage at the point of
regulation (APU generator side of APB). The BCUs
monitor C-phase from the AGCUs to get voltage and
frequency for indication.
The CT senses three-phase current. The BCUs use this
data for percent load indications. The load shows as a
percent of 250 amperes. The BCUs exchange this data
with each other on an ARINC 429 bus. The EIUs use data
from BCU 1 unless there is a malfunction with the BCU.
If this occurs, the EIUs use the data from BCU 2.
ELECTRICAL POWER -- APU INDICATION
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0 / 2 2 / 1 9 9 9
APU
FROM
VOLT
TO EIUS
AGCU
28 28 28 28 28 28
35 35 35 35
APU BAT
DC-V
IDG OUT.TEMP
IDG RISE TEMP
400 400 400 400
115
400
AC-V
FREQ
LOAD
1APU 2 EXT 2
3 4
0
0
0.00
ELECTRICAL
10DC-A CHG
0
0
0.00
115
400
2APU 1EXT 1
0.75
0 0 0 0
0.00 0.00 0.00 0.00 0.65
CHG
24 24 24 24
0 0 0 0
MAIN BAT
38
CT
VOLTS
TO LOAD
BCU 2FREQUENCY
APB
EIU(S)
AC-V
FREQ
LOAD 0.00
0
0 115
400
0.75
EXT 1 APU 1
GEN
REG
BCU 2
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ELECTRICAL POWER - APU INDICATION
GMT18:54:0402SEP87DATE% LOAD
BCU 1NOTE: APU 1 SHOWN,
AUXILIARY EICASAPU 2 SIMILAR
- 261 -
2 2 / 1 9 9 9
747 TRAINING MANUAL
General
Voltage, frequency and percent load data for external
power 1 and 2 go to their related BCU. The BCUs
exchange this data with each other on an ARINC 429 bus.
The EIUs use data from BCU 1 unless there is a
malfunction with the BCU. If this occurs, the EIUs use
the data from BCU 2.
Voltage
The BUC senses voltage at the point of regulation
(receptacle side of XPC). The BCU senses all three
phases but only the highest phase voltage shows. This
data goes to the opposite BCU and to the EIUs.
Frequency
The BCU uses C phase to find frequency. This data goes
to the opposite BCU and to the EIUs.
Percent Load
The CT senses three-phase current and sends it directly
to the BCUs for percent load indications. The load
shows as a percent of 250 amperes. The BCU sends this
data to the opposite BCU and to the EIUs.
ELECTRICAL POWER -- EXTERNAL POWER INDICATION
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747 TRAINING MANUAL
0 / 2 2 / 1 9 9 9
28 28 28 28 28 28
35 35 35 35
APU BAT
DC-V
IDG OUT.TEMP
IDG RISE TEMP
400 400 400 400
115
400
AC-V
FREQ
LOAD
1APU 2 EXT 2
3 4
0
0
0.00
ELECTRICAL
10DC-A CHG
0
0
0.00
115
400
2APU 1EXT 1
0.75
0 0 0 0
0.00 0.00 0.00 0.00 0.65
CHG
24 24 24 24
0 0 0 0
MAIN BAT
38
BCU 2
AC-V
FREQ
LOAD 0.00
0
0 115
400
0.75
EXTERNAL
CT
XPC
% LOAD
VOLTS
FREQUENCY
BCU 1TO LOAD
EXTERNAL
EIU(S)
EXT 1 APU 1
POWERRECEPTACLE
POWER NO. 2
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ELECTRICAL POWER - EXTERNAL POWER INDICATION
GMT18:54:0402SEP87DATE
NOTE: EXTERNAL POWER 1 SHOWN,
AUXILIARY EICASEXTERNAL POWER 2 SIMILAR
- 263 -
2 2 / 1 9 9 9
747 TRAINING MANUAL
General
The GCUs sense voltage, frequency and percent load data
and send it to the BCUs on an ARINC 429 bus. The BCUs
send this data to the EIUs. The EIUs use the data from
BCU 1 unless there is a malfunction with the BCU. If
this occurs, the EIUs use the data from BCU 2.
Voltage
The GCU senses voltage at the point of regulation (IDG
side of the GCB). The GCU senses all three phases, but
only the highest phase voltage shows.
Frequency
The PMG sends three-phase voltage to the GCU. The GCU
uses the A-phase to find frequency. This data then goes
to the BCUs.
Percent Load
The percent load indication is from the total current
flow in all three phases of the IDG. The CTs in the IDG
send this data to the GCU. The GCU then sends this data
to the BCUs. The load shows as a percent of 250
amperes.
ELECTRICAL POWER -- GENERATOR POWER INDICATION
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1 0 / 2 2 / 1 9 9 9
28 28 28 28 28 28
35 35 35 35
APU BAT
DC-V
IDG OUT.TEMP
IDG RISE TEMP
400 400 400
115
400
AC-V
FREQ
LOAD
1APU 2 EXT 2
3 4
0
0
0.00
ELECTRICAL
10DC-A CHG 10
2
0
0.00 0.65
CHG
24
0
IDG
BCU 1
115 115 115
0.75
0
0.75 0.35
145 145 115
35 35 30
EIU(S)
0.00 0.00
0
0
0
0
EXT 1 APU 1
MAIN BAT
1
AC-V
FREQ
LOAD
% LOAD
FREQUENCY
TO LOAD
PMG
CT
VOLTAGE
GCU 1
400
0.75
115
0.00
0
0
0.00
0
0EXT 1 APU 1
GCB
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ELECTRICAL POWER - GENERATOR POWER INDICATION
GMT18:54:0402SEP87DATEBCU 2
NOTE: IDG 1 SHOWN,
AUXILIARY EICASOTHER IDG'S SIMILAR
- 265 -
/ 2 5 / 1 9 9 9
747 TRAINING MANUAL
General
BCU 1 senses the dc volts and dc amperes for the main
battery. This data shows on the electrical power
maintenance page.
Voltage
BCU 1 senses the battery voltage at the main hot
battery bus and sends this data to the EIUs for
indication. The voltage that shows is the battery
charger voltage if the battery charger is in operation.
Current
A dc current sensor (DCCS) next to the battery on the
negative lead senses dc current from the battery. This
data goes to BCU 1 and then to the EIUs for indication.
A charge (CHG) or discharge (DIS) message shows next to
the dc current indication for charge or discharge of
the battery.
ELECTRICAL POWER -- MAIN BATTERY INDICATION
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28 28 28 28 28 28
35 35 35
APU BAT
DC-V
IDG OUT.TEMP
IDG RISE TEMP
AC-V
FREQ
LOAD
1APU 2 EXT 2
3 4
ELECTRICAL
10DC-A CHG
2
0
0.00
CHG
0
0
0
0
0.00 0.00 0.65
115
400
0
0
115145145
35 35 30
35
28
CHG
DC-V
DC-A
115 0 0 0 0
400 0 0 0
0.75 0.00 0.00 0.00
MAIN MAIN
DCCS
P180
VOLTAGE
CURRENT
BCU 1
BAT.
MAIN HOT
MAIN BAT
MAIN BAT
38
EXT 1 APU 1
38
EIU(S)
BAT BATCHGR
BAT BUS
VOLT
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ELECTRICAL POWER - MAIN BATTERY INDICATION
GMT18:54:04
AUXILIARY EICAS
02SEP87DATE
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0 / 2 2 / 1 9 9 9
747 TRAINING MANUAL
General
BCU 2 senses dc volts and dc amperes for the APU
battery and shows this data on the electrical power
maintenance page.
Voltage
BCU 2 senses battery voltage at the APU hot battery bus
and sends this data to the EIUs for indication. The
voltage that shows is the battery charger voltage if
the battery charger is in operation.
During an APU start (crank contactor energized) the
voltage that shows changes from APU hot battery bus
voltage to the voltage at the starter side of the crank
contactor.
Current
A dc current sensor (DCCS) next to the battery on the
negative lead senses the dc current from the battery.
This data goes to BCU 2 and then to the EIUs for
indication. During an APU start the voltage on the
starter side of the APU crank contactor inhibits the
current indications that usually show. A charge (CHG)
or discharge (DIS) message shows next to the dc current
indication for charge or discharge of the battery.
ELECTRICAL POWER -- APU BATTERY INDICATION
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BAT VOLTS
28 28 28 28 28 28
35 35 35
APU BAT
DC-V
IDG OUT.TEMP
IDG RISE TEMP
AC-V
FREQ
LOAD
1APU 2 EXT 2
3 4
ELECTRICAL
10DC-A CHG
2APU 1EXT 1
0
0
0.00 0.00
115
400
0
0
145145
35 35
35
28
10
115 0
400
0.75 0.00
BCU 2
115 115 115 115
400 400 400 400
0.75 0.75 0.75 0.00
DIS
DIS
APU BAT
EIU(S)
35
145
MAIN BAT
38
VOLTAGE
CURRENT
TO APU
R7184 APU
FROM APU
DCCS
APUAPU
APU
BATBATCHGR
(P183)
CRANKVOLTAGE
(P183)
BATTERY
CRANK
CONTACTOR(P183)
STARTERMOTOR
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ELECTRICAL POWER - APU BATTERY INDICATION
GMT18:54:04
AUXILIARY EICAS
02SEP87DATE
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1 0 / 2 5 / 1 9 9 9
747 TRAINING MANUAL
General
TRU voltage and current show on the electrical system
maintenance page.
Current
The DCCSs are in the P180 panel (one for each TRU).They sense the dc current that the TRUs supply to their
dc loads. This current data goes to the related GCU.
The GCU send the data to the BCUs. The BCUs send the
data to the EIUs. The EIUs use the data from BCU 1
unless there is a malfunction with the BCU. If this
occurs, The EIUs use the data from BCU 2.
Voltage
The related GCU senses voltage directly from the dc
bus. This voltage data goes to the BCUs. The BCUs send
the data to the EIUs. The EIUs use the data from BCU 1
unless there is a malfunction with the BCU. If this
occurs, The EIUs use the data from BCU 2.
NOTE: Voltage indication is bus voltage and does not
necessarily represent the TRU voltage for that
bus. To read individual TRU voltage the dc
isolation relay for that bus must be opened to
isolate the bus.
ELECTRICAL POWER -- TRU INDICATION
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GMT18:54:04
28 28 28 28 28 28
35 35 35
APU BAT
DC-V
IDG OUT.TEMP
IDG RISE TEMP
AC-V
FREQ
LOAD
1APU 2 EXT 2
3 4
ELECTRICAL
10DC-A
2
0
0.00
CHG
0
02SEP87DATE
BCU 2
0
0.00
0
BCU 1
0
0
0.00 0.75 0.75 0.35 0.00 0.65
115
400
0
0
115115115
400 400 4000
115145145
35 35 30
TRU
DC BUS
TRU
115V
P6 TRU
28 28 28 28
35 35DC-A
DC-V
35
28
35
35
TRU
CURRENT
EIU(S)
GCU 1
38
38
EXT 1 APU 1
VOLTAGE(P180)
VOLTSCURRENT
AC
DCCS(P180)
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ELECTRICAL POWER - TRU INDICATION
AUXILIARY EICASNOTE: TRU 1 SHOWN,OTHER TRUS SIMILAR
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747 TRAINING MANUAL
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1
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9
18 54 04
28 28 28 28 28 28
35 35 35
APU BAT
DC-V
IDG OUT.TEMP
IDG RISE TEMP
AC-V
FREQ
LOAD
1APU 2 EXT 2
3 4
ELECTRICAL
10DC-A CHG 10
2
0
0.00
CHG
0
02SEP87BCU 2
0
OIL IN
OIL OUT
OIL
BCU 1
IDG GCU
OIL OUT/OIL
090286
0.75 0.75 0.35 0.00 0.65
115
400
0
0
115115115
400 400 400
75115145145
35 35 30
35EIU'S
MAIN BAT
IDG RISE TEMP
IDG OUT.TEMP 145 145 115 75
0303535
0.00
0
0
EXT 1
0
0.00
0
APU 1
TEMPPROCESSOR
RISE TEMP
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ALTEON PROPRIETARY - Copyright (c) - See title page for details
ELECTRICAL POWER - IDG OIL TEMPERATURE INDICATION
GMT18:54:04
AUXILIARY EICAS
02SEP87DATEBCU 2 DATE 090286
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747 TRAINING MANUAL
General
There is BITE circuitry in the BCUs and GCUs that can
identify an electrical power system malfunction.
Malfunctions are line relevant faults (LRF) or shop
relevant faults (SRF) (inter-wiring level). LRFs are in
CMC memory for later access. SRFs are in the related
BCU or GCU nonvolatile memory. To identify malfunctionsthe BITE system operates in these modes:
- BIT
- Ground Test
- Power up/replacement test.
BIT
There are two BIT modes. One mode is for a protectivetrip isolation (fault isolation). The other mode is the
BIT monitor which does an analysis of the electrical
system at intervals during operation.
When a protective trip occurs, the BIT identifies the
breaker/relay and the protective function that has the
possible malfunction. If the malfunction is in the GCU,
the GCU sends the LRF data to the BCU. This causes the
related EICAS message to show. The BCU also sends themalfunction data to the CMC to hold in memory.
The BIT monitor does an analysis of the electrical
monitor finds SRFs, the GCU and BCU holds them in
nonvolatile memory. If the BIT monitor finds LRFs, data
goes to the BCU. This causes the related EICAS message
to show. The BCU also sends the data to the CMC to hold
in memory. LRFs found by the BIT monitor show only
while the malfunction is active.
Ground Test
When they get a ground test request from the CMC, the
BCUs and GCUs do their ground tests. Ground tests can
start only when the GHB has power. If the ground test
finds LRFs, data goes through the BCU set by the ground
test. This data then goes to the CMC to hold in memory.
The related units hold their SRFs in non-volatile
memory.
The GCUs start the internal ground test after they get
a request from the BCUs. The two BCUs send this
request, but only one is necessary for the GCUs to
start the test.
Power Up/Replacement Test
The power up/replacement test starts automatically when
the GCUs and BCUs get power and the airplane is in theground mode. This test is the same as the ground test
except that there is no test of the non-volatile
memories of the units.
ELECTRICAL POWER -- BCU/GCU BUILT-IN TEST EQUIPMENT (BITE)
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ALTEON PROPRIETARY - Copyright (c) - See title page for details
y
system at intervals during operation for malfunctions
which do not cause a protective trip. If the monitor
finds a malfunction, it automatically starts a routine
to identify the cause of the failure. If the BIT
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747 TRAINING MANUAL
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1 0 / 2 2 / 1 9 9
9
BCU 1
GCU
GCU
GCU
GCU
P
GROUND TESTS
w
w
PAGE
DELSP
VNAV
a
w
FIX
K
L
RADNAV
MENU
HOLD
+/-0.
987
654
32
CLR/
EDCBA
O
J
N
I
M
H
L
GF
Y
T
X
SRQ
WVU
PSD
LIAF
GSM
Z
BRT
TSFO
EXECLEGS
NEXT
1
PROG
RTE ARRDEP
PAGEPREV
REFINIT
CMC
1
2
3
4
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ELECTRICAL POWER - BCU/GCU BUILT-IN TEST EQUIPMENT (BITE)
BCU 2
CDU
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747 TRAINING MANUAL
General
You make ground test selections from the CMC MENU on a
CDU. You make the electrical system ground tests
selection by pushing the line select key next to 24
ELECTRICAL. The 24 ELECTRICAL selection causes the
these tests to show:
- EPGS (BCU 1)
- EPGS (BCU 2).
ELECTRICAL POWER -- GROUND TEST SELECTION
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747 TRAINING MANUAL
R e v
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1 0 / 2 2 / 1 9 9
9
/G R O U N D T E S T S
<
X X XX
E P G S B( C U )1
/G R O U N D T E S T S
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2 4 E L E C T R I C A L
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1 / 2
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ELECTRICAL POWER - GROUND TEST SELECTION
< E P G S B( C U 2 )
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747 TRAINING MANUAL
General
This schematic shows the basic AC and DC power
distribution. Breaker control and bus protection does
not show.
ELECTRICAL POWER -- SYSTEM SCHEMATIC
ELECTRICAL POWER -- SYSTEM SCHEMATIC
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6
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0 5 / 3 1 / 2 0 0 0
1
3
3
1
2
ENERGIZED DURING APU STARTBATMAIN HOT
MAIN BAT
APU BAT
DC 4DC 3DC 2DC 1
DCIR
AC 4
AC 4AC 3AC 2
EXT 1 EXT 2
OFF
SWITCHSTANDBY POWER
BAT
AUTO
RCCB
RCCBDC VOLTAGE SINGLE TRU
OPERATION
INVERTERSTATIC
115V AC 1ñ AC STANDBY
STANDBY POWERXFER RELAY
SSB
BTB
IDG 2
TRU 2
F/O XFER
BUS VOLTAGEINSTRUMENT
SENSE UNITS
CAPT XFER
SYNCH
IDG 3
TRU 3
UTILITY
ELCU
GALLEY
ELCU
UTILITY
ELCU
GALLEY
ELCU
TRU 4
APB 2
APU 2
XPC 2
IDG 4
GCB
RCCB
RCCB
APU
RELAYSTART
APU BAT
RELAYBUS XFER
APU B/C
RELAYDISABLE
GHR
TRU1
DC GH
TRU2
DC GH
AC GHSECT 2
SECT 1AC GH
GHR GSSR GSSR
GSTR
AC GS
THERMOSWITCHMAIN BAT
RELAYDISABLEMAIN B/C
B/CMAIN APU
B/C
RCCB
RELAYSTARTAPU
THERMOSWITCHAPU BAT
GSTR
GS UTILITY
TRU 1
IDG 1
XPC 1
APU 1
APB 1
UTILITY
ELCU
ELCU
GALLEY
ELCU
UTILITY
ELCU
GALLEY
BATTERYAPU
BATAPU HOT
AC 1
XFR RLYAPU INV
APUSTATICINVERTER
1ñ
115V AC
BAT
APU STBYBUS XFR RLY
SW
APU STBYBUS XFR RLY
G H
A B
12
J
AB
J
K
BUSSYNCHBUS
D
E
F
4
F
4
K
D
E
F
G
H
RCCB
P6 APUSTBY ALTPOWER
l-PFDL-NDL-FMC
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ALTEON PROPRIETARY - Copyright (c) - See title page for details
ELECTRICAL POWER - SYSTEM SCHEMATIC
2
3
4POWER ONENERGIZED DURING NORMAL
REMOTE CONTROL (GND=OFF)
RCCB
BATTERYMAIN T/R MODE WITH GROUND REMOVED
BAT SWSENSE RELAY
RELAYOPERATION
MAIN BATRELAY
RELAYBAT XFER
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747 TRAINING MANUAL
General
This schematic shows differential protection on AC
buses. Breaker control does not show.
ELECTRICAL POWER -- BUS PROTECTION
ELECTRICAL POWER -- BUS PROTECTION
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747 TRAINING MANUAL
7
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0 5 / 3 1 / 2 0 0 0
4GCB
EXT2
(P715)T4019
XPC
P6P6
UTIL1
DIST
T4114(P715)
T4118(P715)
(P715)T4013
T4023(P715)
2
2APB
T4017(P615)
4BTB
(P615)
(P615)T4007
T4011
AGCU2
APU2
P415
P415
GLY 4LOADS
P6
P6
WINDOW
TRU 4
HEAT
(P714)
GSTR
UTIL
GSTRT4663
(P714)
GHR2 GHR1GSSRUTILGSSR
T4018
T4022(P714)
T4113(P714)
T4012(P714)
T4117(P714)
BCU1
APU1
AGCU1
GSB
UTIL BUSGND SERV
T4014(P514)
BTB1
T4008(P514)
GCB1
T4004(P514)
IDG1
GCU1
UTIL1 ELCU
GLY 1LOADS
ELCUGLY 1
GNDSERV
P414
T4024 P6
P7
TRU 1P6
T4016(P515)
BTB3
T4010(P515)
GCB3
IDG3
T4006(P515)
GCU3
T4021
(P92)
T4020
(P92)
(P614)T4015
2BTB
(P614)T4009
2GCB
(P614)T4005
IDG22GCU
P414
P414AC 2DIST B
AC 2DIST A
LOADSGLY 2ELCU
GLY 2
UTIL2 ELCU
HEATWINDOW
P6
P7
TRU 2
T4025
T4486(P515)
AC 3DIST
P415
LOADSGLY 3
GLY 3ELCU
3 ELCUUTIL
T4026
TRU 3
P6
P7
IDG44GCU
DIST B
DIST AAC 4
AC 4
4 ELCUUTIL
GLY 4ELCU
T4027
SSB
EXT1
XPC1
AC 1
T4018(P714)
SYNCH BUS
APB
SYNCH BUS
1
SECT 2GHB 1
SECT 1GHB 1 LOADS
BUS
UTIL2LOADS
UTIL3LOADS
UTIL4LOADS
BCU2
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ALTEON PROPRIETARY - Copyright (c) - See title page for details
(P614)
P415
T4484(P514)
T4485
P85 & P183
P414AC 2DIST
5 5
(P615)T4487
NOTE: DASHED LINES SHOW CONNECTIONS
CURRENT TRANSFORMERS TO DIFFERENTIAL PROTECTION
ELECTRICAL POWER - BUS PROTECTION
BUS
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BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
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FOR TRAINING PURPOSE ONLY PAGE 2 TECHNICAL TRAINING OFFICE
BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
ELECTRICAL POWER
General
The electrical power system consists of those systemsand components which generate, distribute and controlelectrical power to the airplane. The systems include:
- External/APU power - Engine power - DC power - Standby power
- Load distribution- Indicating
External/APU Power
External/APU power supplies electrical power duringground operations. It includes two external power
sources and two APU generators.
Engine Power
DC Power
The dc power system supplies those loads requiring dcpower. It includes the batteries and transformer rectifier units.
Standby Power
Standby power supplies power to selected loads whenthe primary source has failed.
Load Distribution
The load distribution system is used to control anddistribute ac and dc power throughout the airplane.
Indicating
Indicating includes the electrical power interfaces with
EICAS and the central maintenance computer andrelated displays.
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Electrical power supplied by the engines is used for allnormal flight operations. Engine power consists of four integrated drive generators (IDG).
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TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
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BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
ELECTRICAL POWER SYSTEM (SIMPLIFIED)
General
Electrical power is distributed in the airplane through theac and dc distribution systems. The ac distributionsystem is made up of buses:
- AC 1, 2, 3, 4- F/0 transfer (AC F/O XFR)- Capt transfer (AC CAPT XFR)
- AC standby (AC STBY)- Ground handling (AC GH)- Cargo handling (AC CH)- Ground service (AC GS)
The dc distribution system is made up of buses:
- DC 1, 2, 3, 4- DC ground handling (DC GH)- DC cargo handling (DC CH)- APU hot battery (APU HOT BAT)
M i h b (MN HOT BAT)
AC Buses 1, 2, 3, 4
The ac buses are powered by the IDGs, APU generatorsor external power carts.
An IDG is connected to its respective bus by closing theassociated generator circuit breaker (GCB). Paralleloperation of the IDGs is accomplished when theassociated bus tie breakers (BTB) and GCBs are closed.The synchronizing (synch) bus is divided into twosections by a split system breaker (SSB). With proper
use of the breakers any generator can supply power toany load bus, and any combination of the IDGs can beoperated in parallel. The power output of the APUgenerators or external power carts can also beconnected to the load buses by closing the auxiliarypower breakers (APB) or external power contactors(XPC).
Transfer Buses
There are two transfer buses; the captain's and the firstffi ' Th i ' f b i ll d
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- Main hot battery (MN HOT BAT)- Main battery (MN BAT)- APU battery (APU BAT)
officer's. The captain's transfer bus is normally poweredfrom ac bus 3. If ac bus 3 is not powered, the transfer bus will transfer to ac bus 1 for power. The first officer'stransfer bus is normally powered from ac bus 2 but will
BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
transfer to ac bus 1 if ac bus 2should. lose power.
AC Standby Bus
The standby ac bus is normally powered by ac bus 3 butwill switch to the static inverter if ac bus 3 is not powered,the battery switch is on and the standby power switch isin AUTO.
The APU AC standby bus is an alternate power sourcefor the captains primary instruments when power to
those instruments fail, the battery switch is ON and thestandby power switch is in the AUTO position.
Ground Handling Bus
The ground handling bus is powered from either APUgenerator 1 or external power receptacle 1 through the
ground handling relay (GHR). The bus is poweredautomatically whenever external power or APU power isavailable. If both APU and external power are available,external power powers the bus. The ground handlingb i t d i fli ht
generator 2 or external power receptacle 2 through thecargo handling relay (CHR). The bus is poweredautomatically whenever external power or APU power isavailable.
Ground Service Bus
The ground service bus is always powered by ac bus 1 if that bus is powered. If ac bus 1 is not powered, theground service bus may be powered by external power 1or APU generator 1 through the ground service select
relay (GSSR) and ground service transfer relay (GSTR).If both external and APU power are available, externalpower will power the bus.
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FOR TRAINING PURPOSE ONLY PAGE 6 TECHNICAL TRAINING OFFICE
bus is not powered in flight.
Cargo Handling BusThe cargo handling bus is powered from either APU
BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
DC 1, 2, 3, 4
Power to dc buses 1, 2, 3, and 4 is supplied bytransformer rectifier unit (TRU). The dc buses parallelthrough the dc isolation relays (DCIR). The dc isolationrelays are controlled by the operation of the bus tieswitch (PS).
DC Ground Handling Bus
The dc ground handling bus is powered when the ac
ground handling bus is powered. The dc power issupplied by two TRUs similar to but not the same as theTRUs used on the main dc buses.
DC Cargo Handling Bus
The dc cargo handling bus is powered when the ac
cargo handling bus is powered. The dc power is suppliedby one TRU. The TRU is the same as the ones used onthe dc ground handling buses.
Main and APU Hot Battery Buses
powered, the battery chargers power the buses andcharge the batteries.
Main and APU Battery Buses
The main and APU battery buses normally receivepower from dc bus 3. If dc bus 3 loses power, the busesreceive power from their respective batteries as long asthe battery switch is on.
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Main and APU Hot Battery Buses
The main and APU hot battery buses are powered by themain and APU batteries. when the ground service bus is
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TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
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BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
EXTERNAL POWER COMPONENTS
All of the components in the external power system arein the main equipment center (MEC) except the electricalsystem control panel, the generator manual reset paneland the external power panel. The external power system includes:
- External power panel with two receptacles- Ground handling relays (2)- Cargo handling relays (2)
- Current transformers (4)- External power contactors (2)- Bus control units (2)- Transformer rectifier units (3)- Ground service relays (4)- Split system breaker - Generator manual reset panel
- Electrical system control panel
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BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
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BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
NOTES
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FOR TRAINING PURPOSE ONLY PAGE 11 TECHNICAL TRAINING OFFICE
BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
EXTERNAL POWER GENERAL OPERATION
General
Three-phase, 400 HZ, 115-volt ac power is supplied tothe airplane by two external power carts through theexternal power receptacles. Before the power isconnected to the airplane systems, two bus control units(BCU) sample it. The No. 1 BCU looks at the power coming from the aft receptacle and the No. 2 BCU looksat power coming from the forward receptacle. The BCUs
check for proper seating of the plugs, voltage, frequency,phase rotation and that the plug interlock system is notshorted to the main feeder wires. When the BCUs aresatisfied that all of these conditions are met, they turn onthe external power AVAIL lights on the electrical systemcontrol panel in the flight deck.
Ground Handling Bus
When the No. 1 BCU turns on the external power AVAILlight, it also energizes the ground handling relay (GHR)to power the ground handling bus (GHB). Cargo loading,
Cargo Handling Bus
When the No. 2 BCU turns on the external power AVAILlight, it also energizes the cargo handling relay (CHR) topower the cargo handling bus (CHB) for main deckcargo loading.
Ground Service Bus
At the forward number two left door is the ground serviceswitch. Operation of this switch signals the No. 1 BCU to
energize the ground service relays to power the groundservice bus (GSB). Interior lighting and the batterychargers are some of the systems on the GSB.
External Power
There are two momentary switches labeled EXT PWR 1
and EXT PWR 2 on the electrical system control panel.Pressing EXT PWR 1 signals BCU 1 to close itsassociated external power contactor (XPC). The ONlight in the switch comes on and the AVAIL light goes off.BCU 2 closes the split system breaker (SSB) at this time
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FOR TRAINING PURPOSE ONLY PAGE 12 TECHNICAL TRAINING OFFICE
p g g ( ) g g,cleaning outlets and fueling are some of the systems onthe GHB.
p y ( )if
BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
External Power (cont)
No other power is on the synch bus. Power is not on theairplane and is being supplied by the aft power cord.Pressing EXT
PWR 2 signals BCU 2 to trip the SSB andclose its associated XPC. The ON light in the switchcomes on and the AVAIL light goes off. Now EXT
PWR 1is powering the left side of the synchronizing (synch) bus,and EXT PWR 2 is powering the right side of the synchbus.
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BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
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BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
NOTES
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FOR TRAINING PURPOSE ONLY PAGE 15 TECHNICAL TRAINING OFFICE
BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
CARGO HANDLING BUS CONTROL
General
The cargo handling bus (CHB) is used for ground
operations and can only be powered on the ground.BCU No. 2 controls the application of power to the CHB.The bus is actually divided into two sections and can bepowered by either external power No. 2 or APUgenerator No. 2. Either power source may be used, butexternal power has priority if both are available.
Power cannot be applied to the aircraft busses and thecargo handling busses from the same source, due to thehigh loads anticipated on the cargo busses on thefreighter. This is accomplished by supplying a ground for the cargo handling relays through the external power contactor and the auxiliary power breaker when they are
open.
External Power
When external power is applied to the No. 2 (fwd)t l t l th BCU l th
- Frequency (375 to 425 Hz)- Phase rotation (A B C)- No faults on the interlock (pins E and F are consideredthe interlock). The faults that the BCU is looking for areovercurrent or overvoltage on pins E and F. This could
occur if he external power plug was damaged and themain ac voltage was shorted to pins E or F.- Pin E/F connected (insures that the external power plug is properly installed)
After the above conditions are satisfied, the BCU
generates the external power available signal. Externalpower will power the cargo handling busses if thefollowing is true:- CHR not failed - Internal circuits in the BCU monitor for a short to ground on the control wire to the CHRS. If ashort is sensed the BCU removes the close command tothe relay.
NOTE: A reset is accomplished by removing power onthe No. 2 external power cord.
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external power receptacle, the BCU samples theaverage of all three phases for:
- Voltage (104.5 to 125 volts ac)
BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
External Power (cont)
- Electrical system not in the AIRMODE -airmodemeans that the any three IDG'S are above 6100 rpm.The BCU receives the information from air ground
logic and IDG speed inputs.
- External power contactor not closed -A ground for the CHR's is supplied through auxiliary contacts of the external power contactor when the contactor isopen.
If all of the conditions are satisfied and the inhibits arenot present, the BM energizes the two CHRS. Externalpower is then applied to the CHB.
APU Power
The auxiliary generator control unit (AGCU) samplespower being supplied by the No. 2 APU generator. Whenthe APU is above 95% and the voltage is between 104and 130 volts ac, the AGCU sends an APU power readysignal to the BCU.
- External power is not available
- The CHR's have not failed
- The electrical system is not in the air mode
- The Auxiliary control breaker is not closed
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The APU will power the CHB if the following is true:
BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
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BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
GROUND SERVICE BUS POWER
Power for the ground service bus (GSB) automaticallycomes from AC 1 when powered. If AC 1 is not powered,then power for the GSB is selected by pressing the
ground services switch on the panel at door 1L. Thisconnects power from either external or APU sourceswith the external source having priority. When GSBpower is from a selected source, a light in the groundservices switch on the light control panel.
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BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
CARGO HANDLING TRANSFORMER RECTIFIER
One cargo handling transformer rectifier unit (TRU) is inthe forward-right MEC mounted to the station 400bulkhead.
The TRU is a solid state device that converts 115 voltsac to 28 volts dc. It maintains the dc output up to a 20ampere load. The cargo handling TRU is. powered bythe cargo handling bus.
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BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
NOTES
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BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
APU POWER GENERAL OPERATION
General
Three phase, 400 Hz ac power is supplied to the
airplane by two APU driven generators. Before thepower is connected to the airplane systems, twoauxiliary generator control units (AGCU) monitor thepower to insure it is at the proper voltage and frequency.When the AGCUs are satisfied that the power is good,they signal the BCUs to turn on the two APU generator
AVAIL lights on the electrical system control panel in theflight deck.
Ground Handling Bus
When the No. 1 BCU turns on the APU generator AVAILlight, it also energizes the ground handling relay (GHR)
to power the ground handling bus (GHB). Cargo loading,cleaning outlets and fueling are some of the systems onthe GHB.
Cargo Handling Bus
power the cargo handling bus (CHB) for main deckcargo loading.
Ground Service Bus
At the forward number one left door is the ground serviceswitch. Operation of this switch signals the No. 1 BCU toenergize the ground service relays to power the groundservice bus (GSB). This does not occur if ac bus No. 1 ispowered or the external power No. 1 is available.
APU Power
There are two momentary switches labeled APU GEN 1and APU GEN 2 on the electrical system control panel.Pressing APU GEN 1 signals BCU 1 to send a closesignal to AGCU 1 to close its associated auxiliary power breaker (APB). The ON light in the switch comes on and
the AVAIL light goes off.
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When the No. 2 BCU turns on the APU generator AVAIL
light, it also energizes the cargo handling relay (CHR) to
BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
APU Power (cont)
BM 2 closes the SSB at this time if no other power is onthe synch bus. APU generator No. 1 is now powering theairplane. Pressing APU GEN 2 signals BM 2 to send a
close signal to AGM 2. However, BM 2 first trips the SSBand then signals AGCU 2 to close its associated APB.The ON light in the switch comes on and the AVAIL lightgoes off. APU GEN 1 is now powering the left side of thesynch bus and APU GEN 2 the right.
Pressing the APU GEN 1 switch with the APB closed,causes the BCU to send an open command to the
AGCU and APB. After receiving the open command, the AGCU also sends an open command to the APB. Either open command opens the APB.
Fault trip signals to the APB can come from either the
BCU or AGCU depending on the reason for the trip.
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BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
NOTES
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BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
ENGINE POWER SYSTEM (IDG)
General
The IDG portion of the engine power system involves the
mechanical aspects of the IDG and its oil coolingcomponents.
Operation
The CSD portion of the IDG is a hydromechanical device.It adds or subtracts speed from the variable input of theengine gearbox to maintain the IDG generator at 12,000rpm.
IDG oil is used for speed control, lubrication and cooling.Heat generated by the IDG is cooled by passing the oilthrough an air/oil heat exchanger and a fuel cooled oil
cooler. The cooled oil is then returned to the IDG. The oilcooler is the primary means of cooling the oil but isassisted by the air/oil heat exchanger under certainoperating conditions.
A pressure relief valve is installed in the oil return line toprevent a rupture in the oil cooler from severely
in line causes the valve to open, draining the fuel and oilmixture overboard. The valve stays open as indicated bya pop-out indicator and must be reset manually.
Control
Control and monitoring of the IDG is done by the GCU.The GCU receives oil temperature, oil pressure, and IDGspeed signals. It sends speed commands to the IDGgovernor and control signals to the air/oil heat exchanger valve.
Oil temperature comes from two temperature bulbsinside the IDG and is used for:- High oil temperature light- Oil out temperature indication- Oil rise temperature indication- Air/oil heat exchanger valve control
Oil pressure comes from an oil pressure switch insidethe IDG and is used for the IDG DRIVE light.
Speed inputs come from the magnetic pickup unit (MPU)and are used for underspeed trips and airmode inhibits.
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prevent a rupture in the oil cooler from severely
damaging the IDG. The high fuel pressure in the IDG oil
BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
Control (cont)
Speed commands from the GCU to the IDG are used tocontrol IDG speed to maintain reference frequency andreal load division.
Air/oil heat exchanger valve control signals are sent tothe valve to control the opening and closing of the valve.
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BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
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BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
IDG COMPONENTS
The IDG system includes the:
Air/oil heat exchanger cools IDG oil. It is located at the
four o'clock position on the HPC case.
Air/oil heat exchanger valve: controlled by the GCU andlocated on the HPC case at the 4 o'clock position.
Fuel/oil cooler: cools IDG oil with fuel. It is located on theright side just below the fuel flow transmitter.
IDG - maintains the IDG generator speed at 12,000 rpm.It is on the aft, left side of the main gearbox.
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BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
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BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
NOTES
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TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
INTEGRATED DRIVE GENERATOR
Right Side
Features of the right side of the IDG include:
- IDG housing - a two piece magnesium casting with adry weight of 117.7 lbs.
- Oil ports - the oil in and oil out ports provide aconnection point between the IDG and the externaloil cooling system. A pressure relief valve at the oil in
port protects the IDG housing fromoverpressurization in case of a core rupture of theFuel/oil cooler.
- Governor adjustment - the governor adjustment is amechanical adjustment used to set the basic speed
of the IDG.
- Drain and fill ports the oil is drained from the IDGcase by removing the case drain plug. The servicecouplings connect to the pressure fill port andoverflow drain port for IDG servicing. The overflowdrain is connected to an internal standpipe.
Case thermal relief valve - the case thermal relief valveallows hot IDG oil to drain overboard if the IDG oiltemperature exceeds 430°F/221°C.
Oil level indicator - the oil level indicator is a prismatic
sight glass. It provides a visual indication of low IDG oil.
Scavenge filter and delta pressure indicator - anon-bypassing filter on the discharge side of thescavenge pump filters all oil flow leaving the IDG. Thescavenge filter contains a pop out delta pressureindicator. A red button pops out when the pressure drop
reaches 60 psid. The differential pressure indicator islocked out below 145°F/63°C to prevent nuisancetripping.
Electrical connectors - two electrical connectors (A andB) interface with airplane wiring for control, protection
and monitoring circuits.
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p p
BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
Right Side (Cont)
Case vent system aspirator - the case vent systemaspirator allows air to enter the IDG case to overcomethe vacuum created by the operation of the
charge/scavenge pumps at startup or altitudepressurization changes.
A pressure relief valve is installed in the oil return line toprevent a rupture in the oil cooler from severelydamaging the IDG. The high fuel pressure in the IDG oilin line causes the valve to open, at about 65 to 75 psig
causing a pressure indicator to pop out. The fuel and oilmixture is drained overboard. The valve stays open andmust be reset manually.
Left Side
Features of the left side of the IDG include:
- Terminal block - the main generator stator threephase output and neutral output leads areterminated at a four stud terminal block.
- Disconnect reset ring - the disconnect reset ring
connection between the IDG input and interconnectshafts.
- Muff spline - a 1.5 inches, removable male spline onthe input drive shaft provides the engine gearbox
connection. The input shaft shear section isdesigned to break with an input torque of 9000 400in-lbs.
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allows ground restoration of the mechanical
BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
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BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
NOTES
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BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
IDG OPERATION
General
The IDG receives a mechanical input from the engine
gearbox which varies in speed. Through a network of hydromechanical components the CSD portion of theIDG drives the generator at a constant 12,000 rpm.
Mechanical Transmission
The engine gearbox drives the IDG input shaft. The input
shaft drives the planetary differential which is gearedwith the right and left pump and motor input gears. Thepump and motor output gears provide speed inputs tothe planetary differential. The combination of the inputsto the planetary differential result in a constant outputwhich drives the generator at 12,000 rpm.
Control
The IDG speed is determined by the governor. Thegovernor is a spring-biased flyweight type unit. Itreceives an oil pressure supply from the charge pumpand senses output speed of the planetary differential.
the position of the flyweights and thus the IDG speed.The coil is powered by the GCU and is used for frequency matching and real load balancing.
The governor controls the oil pressure to the control
cylinder which physically moves wobbler plates insidethe pump and motors. The position of the wobbler platesdetermine the direction and speed of the motor andpump output gears.
Oil
As oil enters from the external cooling system it passesthrough a deaerator. The deaerator removes air from theoil. The charge pump pressurizes the oil and delivers itfor lubrication, cooling and control. The nominal chargepressure is 250 psi as regulated by the charge relief valve. If the oil pressure falls below 140 psi, the charge
pressure switch closes causing the DRIVE light in theIDG disconnect switch to come on. An EICAS messageis also initiated.
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The governor has a magnetic trim coil which influences
BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
Oil (cont)
Leakage from all of the hydraulic components as well aslubrication and generator cooling flow return to acommon sump by gravity. Two scavenge pumps are
used to remove oil from the sump and deliver it to theexternal cooling circuit through the scavenge filter. If thepressure differential in the external cooling circuitexceeds 250 psid, the external circuit bypass valveallows the oil to bypass the circuit.
Disconnect
In addition the IDG is equipped with a disconnect. Thethermal disconnect is integrated with the electricaldisconnect solenoid. The thermal material consists of solder in a closed chamber and is sensitive totemperatures above 199°C. Above 199°C solder melts
allowing a spring to retract the solenoid pin. Retractingthe solenoid pin allows the spring loaded disconnectplunger to engage a ramp, the clutch disconnects andthe IDG no longer operates. The thermal disconnect cannot be reset, the electrical solenoid disconnect can bereset.
Case Vent System
The case vent system consists of an aspirator mountedin the end housing and an aneroid Valve installed in theinput shaft. Air enters the IDG through the aspirator and
escapes through the aneroid valve. The constantexchange of air removes water from the IDG oil whichdecreases the formation of acid, and extends the servicelife of the oil and filters. IDG case pressure is controlledby the aneroid valve.
Case Thermal Relief
If the IDG temperature exceeds 232°C, a solder pelletwill melt allowing all oil to be drained from the IDG.
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BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
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BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
IDG DISCONNECT
General
The IDG input shaft and interconnect shaft may be
disconnected at the flight deck. This allows the engine tocontinue running while shutting down a faulty IDG.
Operation
IDGs are disconnected by pressing one of the guardeddrive disconnect switches on the electrical system
control panel (P5). When the switch is pressed adisconnect solenoid in the IDG is energized allowing aspring-loaded plunger to engage threads on theinterconnect shaft. This causes the interconnect shaft tomove away from the input shaft, disconnecting the IDGfrom the input shaft. With the IDG disconnected a DRIVEDISC advisory and status message appear on EICAS.
The same disconnect signal is sent to the GM to trip theGCR and GCB. This action isolates the generator fromits electrical load.
Maintenance Practice
The disconnect switch should not be operated unless theengine is at or above idle speed. The switch may beoperated with the engine shut down, but the IDG must
be reset before the engine is started. Disconnectingbelow idle speed or with the engine shut down does notresult in a complete separation of the dog teeth.
Resetting is only on the ground following engine shutdown. This is done by pulling out on the reset ring untilthe solenoid nose pin snaps into position.
Thermal Disconnect
In addition the IDG is equipped with a ThermalDisconnect. It is integrated in the electrical disconnectsolenoid. The material consists of a solder pellet in achamber and is sensitive to greater than 199 degrees C(390 degrees F). When the IDG operating temperaturereaches this temperature the solder melts, an internallock pin sets as the disconnect pin retracts, thus the IDGclutch disconnects.
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BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
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BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
IDG OIL COOLER
The IDG oil cooler provides the primary cooling for theIDG during normal flight operations. It is on theright-hand side of the engine just below the fuel flow
transmitter. The heat exchanger consists of a tublar coremounted inside a welded case. Oil from the IDGcirculates continuously through the heat exchanger unless the IDG is disconnected. The oil is directed byflow control ribs across the core tubes. Metered fuel fromthe fuel flowmeter passes through core tubes absorbingIDG oil heat.
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BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
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BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
IDG AIR/OIL HEAT EXCHANGER AND VALVE
General
The IDG air/oil heat exchanger provides supplemental
cooling for the IDG oil. This occurs in cases of lowengine power, or high IDG oil temperature. The air for the heat exchanger is controlled by the heat exchanger valve.
Heat Exchanger
When the fuel/oil cooler has insufficient fuel flow to coolthe IDG oil or the oil outlet temperature is high, the air/oilheat exchanger will assist in cooling the IDG oil. Theair/oil heat exchanger is a tube and fin-type heatexchanger with fan air passing over the heatexchanger's fins and absorbing heat from the IDG oil.IDG oil is directed from the inlet port through tubes to anoutlet port. The heat exchanger includes a pressurerelief valve to bypass oil in the event that it becomesclogged due to contamination or high oil viscosityconditions (Open 50 ± 5 psid, close 45 psid minimum).
Valve
The IDG air/oil heat exchanger valve is a butterfly-typevalve coupled to the inlet of the IDG air/oil heatexchanger and to the fan air supply duct. It is operated
by 11th stage compressor bleed air and controlled by a28 volt dc solenoid. When the valve is signaled to open,it allows fan air to pass through the IDG air/oil heatexchanger.
On top of the valve is a position indicator arm andmanual lockout screw. The arm is attached to the valve
shaft and will point to embossed position labels on top of the valve. The lockout screw may be removed andinserted through a hole in the position indicator arm tolock the valve in the open position.
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BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
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BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
IDG AIR/OIL HEAT EXCHANGER VALVE CONTROL
Two inputs are applied to the valve; a 28 volt dc enablingsignal and 11th stage bleed air. With 28 volts present thevalve will close by 50 psig and open by 35 psig. If the 28
volt dc signal is not present, the valve will remain open atall air pressures.
In the normal mode the generator control unit (GCU)applies 28 volts to one side of a switch in the valve.When the air pressure is less than 35 psig (low enginespeed), the switch is open keeping 28 volts from the
solenoid. With the solenoid relaxed the air is not allowedto close the valve. The valve remains open at this low air pressure and supplements the IDG oil cooling. As the air pressure increases above 50 psig, the switch closes andenergizes the solenoid which allows the air to close thevalve.
The GCU is constantly monitoring IDG oil temperature. If for any reason the oil temperature should reach 127°C,the GCU removes the 28 volts to the valve. This relaxesthe solenoid and blocks the air to the valve. The valveopens and supplements the IDG cooling.
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BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
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TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
IDG COOLING VALVE FAILURE
General
The GCU provides 28 volts dc to close the IDG air/oil
heat exchanger valve and removes the voltage to openthe valve. The GCU monitors these valve commandsignals as well as valve position.
If the GCU senses a difference between the commandedposition and the actual. valve position a disagreementcondition will be set and sent to the BCU's. Upon
receiving the valve disagreement signal BCU 1 (BCU 2 if BCU 1 has failed) sends a valve disagreement signal tothe EIU's.
EIU Logic
The EIU receives the IDG oil temperature of all IDG's.The EIU uses these temperatures and the disagreementsignal to set the ELEC IDG X VALVE status message.This message will be set if the valve fails to open or close when directed by the GCU.
Failed to open - The IDG oil on the engine with a valve
disagreement is 20 deg C higher than an average of the
others.
Failed to close - Any IDG oil temp is more than 20 deglower than the average of the others.
NOTE: In addition to the above, the following EIU logicmust also be. satisfied prior to setting the message:
- All engines running
- All generators on line
- Valid IDG sensing
- N1 greater than 60% or less than 27%
- 600 seconds (10 min) time delay
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disagreement is 20 deg C higher than an average of the
BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
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BOEI NG 747- 400F
TRAI NI NG MANUALATA-24
ELEC POWER Version 0
Jun 1, 2002
IDG SERVICING
General
The scavenge pump recirculates heated oil through the
scavenge filter, air cooled oil cooler and fuel cooled oilcooler to the deaerator. Pressure filling will add oilthrough the cooling circuit to the IDG.
Servicing (Replenishment)
Regular servicing of the IDG does not require complete
case drain. The pressure and drain lines are attached tothe pressure and over flow drain couplings. Pressure fillthe IDG from a proper servicing cart at 5 to 15 psi. Theoil level rises above the top of the overflow drain whichestablishes the correct fill level. Continue to put oil intothe IDG until a minimum of 1 quart of oil flows into thecontainer and flow slows to a dripping condition.
NOTE: The 1 quart of oil does not include the oil thatdrained when the hose was connected to the overflowdrain coupling.
Servicing (Oil Change)
Changing the IDG oil is required for regular interval or scavenge filter damage. Procedures are similar toreplenishing the IDG. Attach the pressure and drain lines.
Remove the case drain plug and allow 1 to 1.5 gallons (4to 6 liters) to exit the case. Replace the scavenge filter as required. Pressure fill until the oil that comes out isthe same color as the oil in the service cart or 1 to 1.5gallons of oil flow from the IDG case. Install the casedrain plug and replenish the IDG with oil normally.
NOTE: After servicing, the IDG oil temperature riseshould be monitored on the EICAS electricalmaintenance page upon engine start. An abnormal risein temperature may indicate improper servicing.
WARNING:MANY WARNINGS AND CAUTIONS ARECONTAINED IN THE MAINTENANCE MANUALREGARDING IDG SERVICING. SEE SERVICINGCHAPTER 12-13-03 AND 12-22-00.
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ELEC POWER Version 0
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LOAD MANAGEMENT SYSTEM
General
The load management system provides automatic
shedding and restoration of the galley and utility loads.This is done by opening and closing the associatedELCUs when an overload condition is sensed (demandexceeds capacity).
Load Shedding
During an overload condition the load managementsystem sheds the associated utility ELCUs one at a timein one-second intervals until the overload condition isremoved. The utility loads shed in the following order:
- U ELCU 1- U ELCU 4
- U ELCU 2- U ELCU 3
When a generator is running isolated (BTB open) and anoverload is experienced on the remaining generators,load reduction starts with the lowest numbered U ELCU.
For example, BTB No. 2 is open and an overload occurs
on the remaining paralleled generators. The tripsequence would be:
- U ELCU 1- U ELCU 4
- U ELCU 3
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Load Restoration
Load restoration occurs automatically in reverse order as load capacity is increased. The order of loadrestoration for:
- One or no generators: restore no loads.
- Two or more generators: restore all Utility loads.
Load restoration for APU and external power will occur automatically as load capacity is increased.
IDG Load Management
Generator load sensing is provided by currenttransformers (CT) in the IDGs. The current sensed bythese CTs is sent to their respective GCUs for processing. The GCUs send generator load information
to the BCUs by two separate means; an ARINC 429 busand by hard wire. The hard wire signals are redundantand are for backup in the event of a failure of the ARINC429 bus.
Inside the BCUs are normally closed relays which supply
power and grounds to the ELCUs. BCU 1 provides
power to:
- U ELCU 1 and 2 and a ground for:
- U ELCU 3 and 4 BCU 2 provides power for:
- U ELCU 3 and 4 and ground for:
- U ELCU 1 and 2
NOTE: In this way both BCUs can separately controlload shedding by either removing the power or the
ground.
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External/APU Load Management
External and APU power CTs provide currentinformation directly to the BCUs for load sheddingprotection. Whenever the external or APU load exceeds
290 amperes (on each generator or receptacle), loadshedding occurs in. the same order as with IDG loadshedding.
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ELEC POWER Version 0
Jun 1, 2002
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NOTES
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ELECTRICAL POWER SYNOPTIC PAGE
General
Pressing the switch labeled ELEC on the EICAS display
select panel calls up the electric power synoptic page onthe auxiliary EICAS display. The synoptic page is aschematic of the electrical system. It uses a combinationof messages and color to show the condition to theelectrical system. The condition of the following isrepresented on the synoptic page:
- Electrical power flow- Integrated drive generators (IDG)- Generator circuit breakers (GCB)- Buses- Bus tie breakers (BTB)- Split system breaker (SSB)- Utility buses
Electrical Power Flow
Electrical power flow is indicated by green-colored flowsegments.
Drive
Normally the DRIVE box is white. If an IDGovertemperature or low oil pressure condition occurs,the DRIVE TEMP/PRESS message appears in the boxand the message and box turn amber.
Generator Control
When the generator is operating and the GCB is closed,the GEN CONT box is white. If the GCB opens, OFFappears in the box and the message and box turnamber.
Buses
When the main buses are powered, the bus outline andmessage are green. If the bus loses power, the busoutline and message turn amber.
Bus Tie Breakers
When the bus tie breaker is closed, the box is white. If the BTB opens, ISLN appears in the box and themessage and box turn amber.
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Utility Buses
The condition of the utility buses is indicated by usingamber to show unpowered and green to show powered.
SSB
The SSB is either displayed open (white) or closed(green).
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O A G OS O AG 60 C CA A G O C
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ELECTRICAL SYSTEM SCHEMATIC
This is an overall schematic showing basic AC and DCpower distribution. Breaker control and bus protection isnot shown.
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ELECTRICAL SYSTEM BUS PROTECTION
This is an overall schematic showing differentialprotection on AC buses. Breaker control is not shown.
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