Electrical (B747 400)

Controls and Indicators6.10.1Electrical Panel6.10.1Standby Power, Battery, and Utility Bus Controls6.10.2APU Generator and External Power Controls6.10.4AC Bus and Generator Controls6.10.6Overhead Maintenance Panel6.10.8Generator Field Manual Reset and Split SystemBreaker Switches6.10.8Electrical Synoptic Display6.10.9Battery Condition6.10.11System Description6.20.1Introduction6.20.1AC Electrical System6.20.1Electrical Load Management and Load Shedding6.20.1AC Electrical System Power Sources6.20.1AC Electrical Power Distribution6.20.3AC Standby Power System6.20.8AC Standby Power System Schematics6.20.11AC Standby Power System Schematic6.20.12AC Standby Power System (AC Bus 3 Unpowered)6.20.14AC Standby Power System (AC Busses 1 and 3Unpowered)6.20.16AC Standby Power System (Standby Power selector- BAT)6.20.18DC Electrical System6.20.20Main DC Electrical System6.20.20Main DC Power Distribution6.20.20Battery Busses6.20.20Electrical Power System Schematic6.20.22

Electrical -

747 Flight Crew Operations ManualElectricalChapter 6

Table of ContentsSection 0April 1, 2006

Copyright The Boeing Company. See title page for details.D6-30151-4006.TOC.0.1

Table of Contents

747 Flight Crew Operations Manual

EICAS Messages6.30.1Electrical EICAS Messages6.30.1

Copyright The Boeing Company. See title page for details.6.TOC.0.2D6-30151-400

April 1, 2006

AUTO ISLNAUTO ISLNControls and IndicatorsSection 10

Electrical Panel

ONOFFONOFFONOFFA V A I LA V A I LAUTOISLNONOFF DRIVEAUTOISLNONOFF DRIVEAUTOISLNONOFF DRIVEAUTOISLNONOFFDRIVEA V A I LA V A I LAPU ONOFFSTARTL UTILITY RSTANDBY POWERAUTOOFFBAT1BATTERYEXT PWR 1APU GEN 1APU GEN 2EXT PWR 22ONONONONBUSTIEBUSBUSBUSBUS3GENCONT1234DRIVEDISCOVERHEAD PANEL

DRIVE1Standby Power and Utility Bus Controls

2External Power, APU Generator, and Battery Controls

3AC Bus and Generator Controls

Copyright The Boeing Company. See title page for details.D6-30151-4006.10.4May 1, 2002

Copyright The Boeing Company. See title page for details.D6-30151-400October 1, 20046.10.3

STANDBY POWERL UTILITYRAPUAUTOONOFFBATONONOFFSTARTOFFOFFBATTERYEXT PWR 1APU GEN 1APU GEN 2EXT PWR 2 ONAAAAVVOFFVVA ONA ONA ONA ONIIIILLLLStandby Power, Battery, and Utility Bus Controls

ONOFFONOFFOFFA V A I LAPU ONOFFSTARTA V A I LA V A I LA V A I LL UTILITY RSTANDBY POWERAUTO4OFFBAT1BATTERY5EXT PWR 1APU GEN 1APU GEN 2EXT PWR 2ONONONON3OVERHEAD PANEL

1STANDBY POWER SelectorPush to turn. OFF standby power not available006, 008 standby bus disconnected from all power sources 203 main and APU standby busses disconnected from all power sources006, 008AUTO allows standby bus to be powered from available sources.203AUTO allows main and APU standby busses to be powered from available sources.BAT powers main battery bus from main battery through the main hot battery bus with battery switch ON powers APU battery bus from APU battery through the APU hot battery bus with battery switch ON disables main and APU battery chargers 006, 008 powers standby bus from the main battery through the main hot batterybus and the standby inverter with Battery switch ON

Electrical -Controls and Indicators747 Flight Crew Operations Manual

Electrical - Controls and Indicators747 Flight Crew Operations Manual

203 powers main and APU standby busses from their related batteries through their hot battery busses and standby inverters with Battery switch ONNote: BAT position for ground maintenance use only.

2 BATTERY SwitchON -006, 008 main battery available as backup power source for main battery bus andstandby bus APU battery available as backup power source for APU battery bus203 main battery available as backup power source for main battery bus andmain standby bus APU battery available as backup power source for APU battery bus and APU standby busOFF - disconnects main and APU batteries from related battery busses.

3 BATTERY Switch OFF LightIlluminated (amber) - Battery switch off

4 UTILITY Power SwitchesON - each switch powers two utility Electrical Load Control Units (ELCUs), and on passenger and combi airplanes two galley ELCUs.OFF - removes power from related ELCUs resets fault logic circuitry

5 UTILITY Power OFF LightsIlluminated (amber) - power removed from related ELCUs by fault protection logic, or related Utility Power switch OFF, or on passenger/combi airplanes, one or more Galley Emergency Power Off switch OFF not illuminated during load shedding

STANDBY POWERL UTILITYRAPUAUTOONOFFBATONONOFFSTARTOFFOFFBATTERYEXT PWR 1APU GEN 1APU GEN 2EXT PWR 2 ONAAAAVVOFFVVA ONA ONA ONA ONIIIILLLLAPU Generator and External Power Controls

L UTILITY RSTANDBY POWERAUTOAPUONOFFBATONONOFFSTART1OFFOFFBATTERY4EXT PWR 1APU GEN 1APU GEN 2EXT PWR 2AVA ONI LAVA ONI LOFFAVA ONI LAVA ONI L536OVERHEAD PANEL

1 APU Generator (APU GEN) Control SwitchesPush AVAIL light illuminated: connects related APU generator to AC electrical systemNote: On freighter airplanes, when the main deck cargo handling bus is powered by APU generator 2, pushing APU generator 2 Control switch causes main deck cargo handling bus to lose power. ON light illuminated: disconnects related APU generator from AC electrical system

2 APU Generator Power Available (AVAIL) LightsIlluminated (white) - APU generator power quality acceptable on freighter airplanes, main deck cargo handling bus powered when APU generator 2 AVAIL light illuminated extinguishes when ON light illuminates

3 APU Generator Power ON LightsIlluminated (white) - related APU generator connected to AC electrical system extinguishes when AVAIL light illuminates

4 External Power (EXT PWR) Control SwitchesPush - AVAIL light illuminated: connects related external power to AC electrical systemNote: On freighter airplanes, when the main deck cargo handling bus is powered by external power 2, pushing External Power 2 Control switch causes main deck cargo handling bus to lose power. ON light illuminated: disconnects related external power from AC electrical system

5 External Power ON LightsIlluminated (white) - related external power connected to AC electrical system extinguishes when AVAIL light illuminates

6 External Power Available (AVAIL) LightsIlluminated (white) - related external power source plugged in, power quality acceptable extinguishes when ON light illuminates on freighter airplanes, main deck cargo handling bus powered when external power 2 AVAIL light illuminatedNote: On freighter airplanes, when both external power 2 and APU generator 2 AVAIL lights are illuminated, external power 2 powers the main deck cargo handling bus. Pushing the External Power 2 Control switch transfers main deck cargo handling loads to APU generator 2.



May 1, 2002

Copyright The Boeing Company. See title page for details.D6-30151-4006.10.5

AUTO ISLNAUTO ISLNAUTOAUTOBUSAUTOAUTOISLNISLNTIEISLNISLNBUSBUSBUSBUSONONONONGENOFFOFFCONTOFFOFF1234DRIVE DISCDRIVEDRIVEDRIVEDRIVEAUTO ISLNAUTO ISLNAC Bus and Generator Controls

AUTOISLNONOFFDRIVEAUTOISLNONOFFDRIVEAUTOISLNONOFFDRIVEAUTOISLNONOFF DRIVE12BUSTIE5BUSBUSBUSBUSGENCONT123463DRIVEDISC4OVERHEAD PANEL

DRIVEDRIVE1BUS TIE SwitchesAUTO arms automatic AC bus tie circuitry closes related DC isolation relay (DCIR) OFF - BTB and related DCIR resets fault logic circuitry

2Bus Isolation (ISLN) LightsIlluminated (amber) - BTB open AC bus isolated from synchronous bus

3Generator Drive Disconnect (DRIVE DISC) SwitchesPush - disconnects IDG from engine when above idle speed opens related Generator Control Breaker (GCB)Note: Ground maintenance action required to reconnect IDG.



Copyright The Boeing Company. See title page for details.6.10.6D6-30151-400

October 1, 2004

4 Generator DRIVE Lights008, 203(SB changes 006 ; improved generator control units for added IDG protection installed)Illuminated (amber) - IDG oil pressure low, or IDG oil temperature high, or GCB open due to uncorrectable generator frequency fault(SB changes 006 ; before SB, improved generator control units for added IDG protection not installed)Illuminated (amber) - IDG oil pressure low, or IDG oil temperature high

5 Generator Control (GEN CONT) SwitchesON - arms GCB to close when generator power quality acceptable OFF - opens generator field and GCB resets fault control logic circuitry isolates generator from its related AC bus

6 Generator OFF LightsIlluminated (amber) - GCB open



October 1, 2004

Copyright The Boeing Company. See title page for details.D6-30151-4006.10.7

Overhead Maintenance PanelGenerator Field Manual Reset and Split System Breaker Switches

FIELD OFFFIELD OFFFIELD OFFFIELD OFFFIELD OFFFIELD OFFOPENGEN FIELD MAN RESET1234121APU2SPLIT SYSTEMBREAKER34OVERHEAD MAINTENANCE PANEL

1 Generator Field Manual Reset (GEN FIELD MAN RESET) SwitchesPush - (spring-loaded toggle, guarded) opens or closes generator field if related Generator Control or APU Generator Control switch off

2 Generator FIELD OFF LightsIlluminated (white) - generator field open.

3 SPLIT SYSTEM BREAKER SwitchPush - (spring-loaded toggle, guarded) opens or closes split system breakerNote: Operative on ground only.

4 Split System Breaker OPEN LightIlluminated (white) - split system breaker open




May 1, 2002

Electrical Synoptic DisplayThe electrical synoptic displays by pushing the ELEC Synoptic switch on the display select panel. Display select panel operation is described in Chapter 10, Flight Instruments, Displays.The synoptic displays the configuration of the AC power system in a simplified schematic format. DC power flow is not represented. The depiction is generated by the status of various system breakers and conductors and does not represent actual power flow. Therefore, the display may not be an accurate representation of system operation. Symbols display in low intensity white when source data is invalid or unavailable.During autoland, with bus tie breakers 1, 2, and 3 open, the message ELECTRICAL SYNOPTIC INHIBITED FOR AUTOLAND appears on thesynoptic display.

DRIVE TEMP/ PRESS1EXT 1 APU 1APU 2 EXT 2SSB234ISLNBUS TIEISLNUTILITYGALLEYUTILITY UTILITYGALLEYBUS 1BUS 2UTILITYGALLEYGALLEYBUS 3BUS 45GEN CONTOFFOFF6DRIVE12347 POWER FLOW (green) NO POWER FLOWLOWER EICAS DISPLAY



Copyright The Boeing Company. See title page for details.D6-30151-400May 1, 20026.10.91 SSB (Split System Breaker)Closed - SSB closed, both sides of synchronous bus connected Open - synchronous bus split.

2 BUS TIE power flow bar present - BTB closed ISLN (amber) - BTB open

3 UTILITY green - utility bus powered amber - utility bus not powered

4 BUS green - AC bus powered amber - AC bus not powered

5 GEN CONT power flow bar present - GCB closed OFF (amber) - GCB open

6 DRIVE blank (green) - normal operation DRIVE TEMP/PRESS (amber) - IDG has high oil temperature or low oil pressure

7 GALLEY (passenger/combi) green - galley bus powered amber - galley bus unpowered


October 1, 2004

Battery ConditionBattery condition displays on the status page by pushing STAT Display switch on the display select panel. Display select panel operation is described in Chapter 10, Flight Instruments, Displays.

12MAIN BATTV-DC28A-DC15DIS3APU BATTV-DC27A-DC10CHGLOWER EICAS DISPLAY

1 Battery Voltage (V-DC)Main and APU battery voltage

2 Battery Current (A-DC)Main and APU battery amperage

3 Battery Charge StatusDIS (Discharge) - battery discharging CHG (Charge) battery charging if battery current is zero, charge status is blank



Copyright The Boeing Company. See title page for details.D6-30151-400May 1, 20026.10.11

Intentionally Blank


May 1, 2002


ElectricalSystem DescriptionChapter 6Section 20

IntroductionThe electrical system generates and distributes AC and DC power to other airplane systems and is comprised of main AC power, DC power, and standby power components. System operation is automatic. Electrical faults are automatically detected and isolated.

AC Electrical SystemThe AC electrical system is the main source of airplane electrical power.Electrical Load Management and Load SheddingElectrical system overload protection is provided by a load management system configured to ensure power is available to critical and essential equipment.If electrical loads exceed power available (airplane or external), the load management system sheds AC loads by priority until the loads are within the capacity of airplane or ground power generators. Loads are shed one at a time through ELCUs in a programmed sequence until the overload condition is relieved. In passenger and combi airplanes, galley busses are shed first, followed by utility busses. In the freighter airplane, utility bus loads are shed. When an additional AC power source is available, loads are restored in reverse order.During load shedding, the ELEC UTIL BUS L and R messages and utility off lights are inhibited. However, the following EICAS alert messages may display in the order shown depending upon fuel system configuration and the extent of load shedding: FUEL PUMP 3 FWD FUEL OVRD 2 FWD FUEL OVRD 3 FWD FUEL OVRD CTR L FUEL PUMP 2 FWDAC Electrical System Power SourcesThe main AC electrical power sources are: four IDGs two auxiliary power sources (APU generators) two external power sources

Copyright The Boeing Company. See title page for details.D6-30151-4006.20.10April 1, 2006

Copyright The Boeing Company. See title page for details.D6-30151-400April 1, 20066.20.9During normal operation, IDG power output to the four AC busses issynchronized. Each bus is interconnected through a single synchronous bus, which distributes electrical power and allows individual AC busses to remain powered when their related generators are inoperative. The split system breaker (SSB) divides the synchronous bus allowing each side of the AC electrical system to be powered by separate auxiliary or external power sources.IDGsOne IDG is mounted on each engine accessory gearbox. Each IDG incorporates an AC generator, drive unit with self-contained lubrication system, and automatic control and protection components.When an engine is started with auxiliary or external power connected to each side of the electrical system (SSB open), the IDG powers its side of the synchronous bus when voltage and frequency are acceptable. The previous power source is disconnected. When an engine on the opposite side of the airplane is started, the IDG powers its side of the synchronous bus. The previous power source is disconnected and the SSB closes.When a single auxiliary or external power source is powering the electrical system and an engine is started, the IDG powers the entire synchronous bus when voltage and frequency are acceptable. The SSB remains closed and the original power source is disconnected.During power source transfers on the ground, such as switching from IDG to auxiliary or external power, output from IDG and another power source is momentarily synchronized before one source is disconnected. This provides smooth, uninterrupted electrical power switching.Each IDG can be electrically disconnected from its related bus by pushing the Generator Control switch OFF. On the ground, an IDG can also be disconnected from its related bus by selecting an available auxiliary or external power source.IDG DisconnectEach IDG can be mechanically disconnected from its engine accessory gearbox by pushing the Generator Drive Disconnect switch. When an IDG is disconnected, generator power output is lost and cannot be restored by flight crew action.The EICAS message ELEC DRIVE displays for low IDG oil pressure or high IDG oil temperature.008, 203(SB changes 006 ; improved generator control units for added IDG protection installed)The ELEC DRIVE message also displays if a GCB is open due to an uncorrectable generator frequency fault.

Electrical -System Description747 Flight Crew Operations Manual

Electrical - System Description747 Flight Crew Operations Manual

Excessively high drive oil temperature disconnects the IDG automatically if notmanually disconnected by flight crew action. The resulting loss of generator power output opens the GCB and displays the EICAS message ELEC GEN OFF. Pushing the Generator Drive Disconnect switch after automatic disconnect replaces the ELEC DRIVE message with the DRIVE DISC message.Auxiliary and External PowerAuxiliary power is available only on the ground from generators mounted on the APU. External power is available from ground sources through two power receptacles located on the lower right forward fuselage. Either source can power main AC busses through connection to the synchronous bus. Auxiliary and external power sources cannot be connected to the same side of the synchronous bus simultaneously. The SSB is commanded open or closed to ensure all AC main busses are powered on the ground.On an unpowered airplane with auxiliary and external power available, when a single power source is selected, the SSB closes and power is provided to the entire synchronous bus by the selected source. When the other same-type power source is selected on the opposite side, the SSB opens and each source powers its side of the synchronous bus. If one power source is disconnected or fails, the SSB closes maintaining power to the entire synchronous bus from the remaining source.When IDGs are powering the electrical system with auxiliary or external power available, selecting a single power source disconnects IDGs on the same side and opens the SSB. The selected source powers its side of the synchronous bus, while the opposite side remains powered by IDGs. Selecting a second auxiliary or external power source on the opposite side disconnects the remaining IDGs and completes the power transfer from IDG to auxiliary/external power; the SSB remains open.Note: On the freighter airplane, when cargo handling is required, selecting only the number one auxiliary or external power source ON ensures the main deck cargo handling bus remains powered.AC Electrical Power DistributionAC power is distributed by the following busses: four main busses two transfer busses ground service and ground handling busses four galley busses (passenger and combi) four utility busses 006, 008 one standby bus

203 two standby bussesAC Main BussesEach IDG normally powers its related AC bus through a GCB. Each AC bus is connected to the synchronous bus by a BTB. With the Bus Tie switch in AUTO, the related BTB controls the AC bus connection to the synchronous bus.If power on an AC bus is unacceptable, the related BTB opens and the bus disconnects from the synchronous bus. However, the AC bus remains powered by its IDG. If the IDG is not able to maintain acceptable power quality, the GCB opens and the BTB closes to provide power from the synchronous bus.The EICAS message ELEC BUS ISLN displays if the BTB is open. Pushing the Bus Tie switch OFF, then AUTO, resets logic circuitry and allows the BTB to close if the fault is corrected. The AC bus is reconnected to the synchronous bus.The main AC busses power individual equipment items such as: TRUs navigation radios and flight control computers flight deck lighting pitot and window heatThe main AC busses also power other AC busses: AC bus 1 powers the ground service bus and provides back-up power for both transfer busses AC bus 2 powers the First Officers transfer bus Each AC bus powers a utility and galley bus (passenger and combi) 006, 008 AC bus 3 powers the Captains transfer bus and the standby bus203 AC bus 3 powers the Captains transfer bus and the main standby busGround Service BusThe ground service bus is powered on the ground and in flight whenever AC bus 1 is powered. The ground service bus powers individual equipment items such as: main and APU battery chargers fuel pumps for APU start upper deck doors flight deck flood, navigation, and service lights miscellaneous service outlets and equipment 006, 008 horizontal stabilizer fuel pump for defueling

On the ground when AC bus 1 is not powered, the ground service bus can beconnected to the same source powering the ground handling bus by pushing the Ground Service switch on the flight attendants panel at door 2L (passenger and combi), or on the cabin panel at door 1L (freighter).Ground Handling BusThe ground handling bus is powered on the ground when APU generator 1 or external power 1 is available. If both are available, external power is automatically used. The ground handling bus powers individual equipment items such as: lower cargo handling equipment and compartment lights fueling system 203 auxiliary hydraulic pumps 1 and 4006, 008 auxiliary hydraulic pump 4Transfer BussesTwo transfer busses provide AC power to critical flight-related equipment. The transfer busses have a common back-up power source. Transfer to the back-up power source is automatic.Captains Transfer Bus006, 008The Captains transfer bus is normally powered by AC bus 3. If AC bus 3 is unpowered, AC bus 1 powers the Captains transfer bus.203The Captains transfer bus is normally powered by AC bus 3. If AC bus 3 is unpowered, AC bus 1 powers the Captains transfer bus. The Captains transfer bus powers the APU standby bus.The Captains transfer bus powers individual equipment items such as: center EFIS/EICAS Interface Unit (EIU) left HF 203 center ADC006, 008 Left FMC, left ND, left PFD

First Officers Transfer BusThe First Officers transfer bus is normally powered by AC bus 2. If AC bus 2 is unpowered, AC bus 1 powers the First Officers transfer bus. The First Officers transfer bus powers individual equipment items such as: autothrottle servo lower EICAS display right ADC, right EFIS control, right EIU, right FMC right CDU, right HF, right ND, right PFDUtility and Galley BussesIn passenger and combi airplanes, each main AC bus powers one utility bus and one galley bus. Each utility/galley bus is controlled by an ELCU, which protects the electrical system from utility and galley bus faults and provides load management through automatic load shedding. With the Left Utility Power switch ON, utility busses 1 and 2 and galley busses 1 and 2 are powered according to ELCU logic. With the Right Utility Power switch ON, utility busses 3 and 4 and galley busses 3 and 4 are powered according to ELCU logic.In the freighter airplane, each main AC bus powers one utility bus. Each utility bus is controlled by an ELCU that protects the electrical system from utility bus faults and provides load management through automatic load shedding. With the Left Utility Power switch ON, utility busses 1 and 2 are powered according to ELCU logic. With the Right Utility Power switch ON, utility busses 3 and 4 are powered according to ELCU logic.Utility busses power individual equipment items such as: forward main fuel pumps 2 and 3 forward override/jettison pumps 2 and 3 center override/jettison pump recirculating fans (passenger/combi airplanes)Galley busses power the galleys located throughout the cabin of passenger and combi airplanes.The EICAS message ELEC UTIL BUS displays and the utility OFF light illuminates if one or more utility or galley (passenger and combi) bus become unpowered due to a fault. Cycling the Utility Power switch OFF, then ON restores power to the affected bus if the fault is corrected.

In passenger and combi airplanes, a guarded ON Galley Emergency Power Offswitch is located at each galley. If a Galley Emergency Power Off switch is selected OFF, the related ECAS message ELEC UTIL BUS displays and utility OFF light illuminates. Cycling the flight deck Utility Power switch OFF, then ON will not reset the indications. The flight deck Utility Power switch should remain ON after cycling, which permits the remaining utility and galley busses to be powered and controlled by their related ELCU.Main Deck Cargo Handling Bus (freighter)The main deck cargo handling bus is powered on the ground when external power 2 or APU generator 2 is available. An interlock prevents either source from powering main electrical busses and the main deck cargo handling bus simultaneously. Pushing the available Power source switch ON deengergizes the main deck cargo handling bus. When both external power 2 and APU generator 2 are available, external power is used. Pushing External Power 2 switch ON transfers main deck cargo handling loads to APU generator 2.Note: When cargo handling is required, selecting only the number one auxiliary or external power source ON ensures the main deck cargo handling bus remains powered.The main deck cargo handling bus powers equipment items such as: main deck cargo handling equipment and lighting nose and side cargo doorsMain Deck Cargo Handling Bus (Combi)The main deck cargo handling bus is powered on the ground when external power 2 or APU generator 2 is available. When both external power 2 and APU generator 2 are available, external power is used. Pushing External Power 2 switch ON transfers main deck cargo handling loads to APU generator 2.The main deck cargo handling bus powers equipment items such as: main deck cargo handling equipment and lighting side cargo doorElectrical bus Isolation during AutolandDuring automatic ILS approach below 1,500 feet radio altitude, AC and DC busses 1, 2, and 3 are automatically isolated. This provides an independent power source for each of the three autopilots. AC bus 4 continues to power the synchronous bus, and will power any other AC bus if its generator fails. During autoland, the AC bus isolation lights 1, 2, and 3 do not illuminate, the EICAS message ELEC BUS ISLN does not display, and the message ELECTRICAL SYNOPTIC INHIBITED FOR AUTOLAND appears on the electrical synoptic.

Autoland is disengaged and the electrical system returned to normal configurationunder the following conditions: TO/GA mode active autopilot disengaged loss of autoland redundancyAC Standby Power SystemThe AC standby power system provides electrical power to critical flight deck equipment.006, 008Major components of the system include: standby bus main battery standby inverter Standby Power selector203Major components of the system include: main and APU standby busses main and APU batteries main and APU standby inverters Standby Power selectorStandby Bus 006, 008The standby bus is normally powered by AC bus 3. With the Battery switch ON, Standby Power selector in AUTO, and AC bus 3 not powered, the standby bus is powered by the standby inverter. The standby inverter, normally unpowered, is activated and receives power from the main battery charger through the main hot battery bus. The main battery charger is normally powered by AC bus 1 through the ground service bus.With the Battery switch ON, Standby Power selector in AUTO, and both AC bus 1 and AC bus 3 not powered, the standby bus is powered by the standby inverter. The standby inverter, normally unpowered, is activated and receives power from the main battery through the main hot battery bus. With the main battery charger unpowered, the main battery can provide power to the standby bus for a minimum of 30 minutes.The standby bus powers individual equipment items such as: left EIU, left CDU, left ILS, left VOR various flight control components standby ignition for all engines

primary EICAS display, RMI, standby instrument lights left ADC, left EFIS control panelMain Standby Bus 203The main standby bus is normally powered by AC bus 3. With the Battery switch ON, Standby Power selector in AUTO, and AC bus 3 not powered, the main standby bus is powered by the main standby inverter. The main standby inverter, normally unpowered, is activated and receives power from the main battery charger through the main hot battery bus. The main battery charger is normally powered by AC bus 1 through the ground service bus.With the Battery switch ON, Standby Power selector in AUTO, and both AC bus 1 and AC bus 3 not powered, the main standby bus is powered by the main standby inverter. The main standby inverter, normally unpowered, is activated and receives power from the main battery through the main hot battery bus. With the main battery charger unpowered, the main battery can provide power to the main standby bus for a minimum of 30 minutes.The main standby bus powers individual equipment items such as: left EIU, left CDU, left ILS, left VOR various flight control components standby ignition for all engines primary EICAS display, RMI, standby instrument lights left ADC, left EFIS control panelAPU Standby Bus 203The APU standby bus is normally powered by the Captains transfer bus. With the Battery switch ON, Standby Power selector in AUTO, and the Captains transfer bus not powered (loss of AC busses 1 and 3), the APU standby bus is powered by the APU standby inverter. The APU standby inverter, normally unpowered, is activated and receives power from the APU battery through the APU hot battery bus. With the APU battery charger unpowered, the APU battery can provide power to the APU standby bus for a minimum of 30 minutes.The APU standby bus powers these equipment items: left FMC left ND left PFD

Standby Power Selector - BAT Position203With the Battery switch ON and Standby Power selector in BAT, main and APU battery chargers are disabled. Each AC standby bus is powered by its related battery and inverter. Each battery can provide power for a minimum of 30 minutes.006, 008With the Battery switch ON and Standby Power selector in BAT, the main and APU battery chargers are disabled. The standby bus is powered by the main battery through the main hot battery bus and standby inverter. The APU battery bus is powered by the APU battery through the APU hot battery bus. The main battery can provide power to the standby bus for a minimum of 30 minutes.Note: The Standby Power selector must be in AUTO for flight. The BAT position is for ground maintenance use only.

AC Standby Power System SchematicsThe schematics on the following pages illustrate the configuration of the AC standby power system and functional relationships of its major components under specific conditions. Sources of electrical power and system components not required for this purpose have been intentionally omitted.

Copyright The Boeing Company. See title page for details.D6-30151-4006.20.20October 1, 2004

Copyright The Boeing Company. See title page for details.D6-30151-400October 1, 20046.20.19AC Standby Power System Schematic006, 008

AC BUS 1

CAPT TRANSFER BUS

AC BUS 3

STANDBY BUS

STANDBY INVERTER

TRU

MAIN BAT BUS

DC BUS 3

MAIN HOT BAT BUS

DC TIE BUS

MAIN BATTERYMAIN BAT CHARGER

GRND SERVICE BUS

CONDITIONS1. BATTERY SWITCH - ON2. STANDBY POWER SELECTOR - AUTO3. ALL BUSSES POWERED NORMALLY

POWERED (AC) POWERED (DC) UNPOWERED

203

AC BUS 1CAPT TRANSFER BUSAC BUS 3

APU STBY BUSMAIN STBY BUS

APUSTANDBY INVERTERMAINSTANDBY INVERTER

TRU 3

APU BAT BUSMAIN BAT BUS

DC BUS 3

APU HOT BAT BUSMAIN HOT BAT BUS

DC TIE BUS

APU BATCHARGERAPUBATTERYMAINBATTERYMAIN BATCHARGER

GRND SERVICE BUS

CONDITIONS1. BATTERY SWITCH - ON2. STANDBY POWER SELECTOR - AUTO3. ALL BUSSES POWERED NORMALLY


AC Standby Power System (AC Bus 3 Unpowered)006, 008

AC BUS 1

CAPT TRANSFER BUS

AC BUS 3

STANDBY BUS

STANDBY INVERTER

TRU

MAIN BAT BUS

DC BUS 3

MAIN HOT BAT BUS

DC TIE BUS

MAIN BATTERYMAIN BAT CHARGER

GRND SERVICE BUS

CONDITIONS1. BATTERY SWITCH - ON2. STANDBY POWER SELECTOR - AUTO3. AC BUS 3 - UNPOWERED4. STANDBY POWER AVAILABLE WITHOUT LIMITATION


203



APUSTANDBY INVERTERMAINSTANDBY INVERTER

TRU 3


DC BUS 3


DC TIE BUS


GRND SERVICE BUS

CONDITIONS1. BATTERY SWITCH - ON2. STANDBY POWER SELECTOR - AUTO3. AC BUS 3 - UNPOWERED4. STANDBY POWER AVAILABLE WITHOUT LIMITATION


AC Standby Power System (AC Busses 1 and 3 Unpowered)006, 008

AC BUS 1

CAPT TRANSFER BUS

AC BUS 3

STANDBY BUS

STANDBY INVERTER

TRU

MAIN BAT BUS

DC BUS 3

MAIN HOT BAT BUS

DC TIE BUS

MAIN BATTERY

MAIN BAT CHARGER

GRND SERVICE BUS

CONDITIONS1. BATTERY SWITCH - ON2. STANDBY POWER SELECTOR - AUTO3. AC BUSSES 1 AND 3 - UNPOWERED4. STANDBY POWER AVAILABLE MINIMUM 30 MINUTES


203

AC BUS 1

CAPT TRANSFER BUS

AC BUS 3

APU STBY BUS

MAIN STBY BUS

APUMAIN

STANDBY INVERTER

STANDBY INVERTER

TRU 3

APU BAT BUS

MAIN BAT BUS

DC BUS 3

APU HOT BAT BUS

MAIN HOT BAT BUS

DC TIE BUS

APU BAT CHARGERAPU BATTERYMAIN BATTERY

MAIN BAT CHARGER

GRND SERVICE BUS

CONDITIONS1. BATTERY SWITCH - ON2. STANDBY POWER SELECTOR - AUTO3. AC BUSSES 1 AND 3 - UNPOWERED4. STANDBY POWER AVAILABLE MINIMUM 30 MINUTES


AC Standby Power System (Standby Power selector - BAT)006, 008

AC BUS 1

CAPT TRANSFER BUS

AC BUS 3

STANDBY BUS

STANDBY INVERTER

TRU

MAIN BAT BUS

DC BUS 3

MAIN HOT BAT BUS

DC TIE BUS

MAIN BATTERY

MAIN BAT CHARGER

GRND SERVICE BUS

CONDITIONS1. BATTERY SWITCH - ON2. STANDBY POWER SELECTOR - BAT3. BATTERY CHARGER DISABLED4. BATTERY POWER AVAILABLE MINIMUM 30 MINUTES


203



APUSTANDBY INVERTERMAINSTANDBY INVERTERTRU 3


DC BUS 3


DC TIE BUS


GRND SERVICE BUS

CONDITIONS1. BATTERY SWITCH - ON2. STANDBY POWER SELECTOR - BAT3. BATTERY CHARGERS DISABLED4. BATTERY POWER AVAILABLE MINIMUM 30 MINUTES


DC Electrical SystemThe DC electrical system includes the main DC electrical system and the battery busses.Main DC Electrical SystemThe main DC electrical system uses four transformer-rectifier units (TRUs) to produce DC power. Each TRU is powered by its related AC bus and provides DC power to a DC bus. The four DC busses are connected through DC isolation relays (DCIRs) to the DC tie bus, which allows each DC bus to remain powered if its related AC bus is unpowered or TRU fails. Pushing the Bus Tie switch to AUTO closes the related BTB and DCIR. Pushing the Bus Tie switch OFF opens the BTB and DCIR. This isolates the DC bus from the DC tie bus, leaving it powered by its AC bus and TRU. Automatic isolation of an AC bus due to an electrical fault opens the BTB, but does not open the DC isolation relay.Main DC Power DistributionTRU DC electrical power is distributed to four main DC busses. Main DC busses power individual equipment items such as: cabin pressure, fuel jettison, and pack temperature controllers wing anti-ice control engine-driven and hydraulic demand pump control fuel transfer and jettison valve control individual nacelle anti-ice controlBattery BussesThe following battery busses distribute DC power in addition to the four main DC busses: Main battery bus APU battery bus Main hot battery bus APU hot battery busThe main and APU battery busses are normally powered by DC bus 3. If either AC bus 3 or DC bus 3 is unpowered, each battery bus is powered by its related hot battery bus.The main battery bus provides power to individual equipment such as: APU controller (alternate), fuel valves (all engines), all crossfeed valves dome, storm, and selected indicator lights IDG disconnect (all engines), manual pressurization control, trailing edge flap control Captains interphone, left radio tuning panel, left VHF

The APU battery bus powers individual equipment items such as: APU DC fuel pump, engine start air control Cargo, First Officers, and service interphones, PA system APU and engine fire/overheat detection loops A and B APU fire warning hornEach hot battery bus is normally powered by the ground service bus through its related battery charger, which acts as a TRU for the hot battery bus while simultaneously maintaining its related battery fully charged. Each battery is directly connected to its related hot battery bus.With the Battery switch ON, the main and APU hot battery busses power their related battery busses if DC bus 3 is unpowered.The main hot battery bus powers individual equipment items such as: APU fuel shutoff valve, spar valves (all engines) APU and lower cargo fire extinguishers engine fire extinguishers (all engines), fire switch unlock (all engines) The APU hot battery bus powers individual equipment items such as: IRU left, center, right DC power left and right outflow valves APU inlet door, APU controller (primary)

Copyright The Boeing Company. See title page for details.D6-30151-4006.20.24October 1, 2004

Copyright The Boeing Company. See title page for details.D6-30151-400October 1, 20046.20.23

Electrical Power System SchematicThe Electrical Power System Schematic illustrates configuration of the electrical power system and functional relationships of its major components. System components not required for this purpose have been intentionally omitted.

DRIVE006, 008

APU BAT BUSSTANDBY INVERTERDC BUS 1DC BUS 2DC BUS 3DC BUS 4BATTERYEXT PWR 1APU GEN 1APU GEN 2EXT PWR 2ONONAV A I LONCONDITION: NOELECTRICAL SYSTEM FAULTS.AUTOAUTOAUTOAUTOBUSTIEAC BUS 1AC BUS 2AC BUS 3AC BUS 4ONONONONGENCONTOFFOFFOFFOFF1234DRIVEDISCDRIVEDRIVEDRIVEDRIVEF/O TRANSFER BUSAC BUS 2POWEREDCAPT TRANSFER BUSSTBY BUSAC BUS 3 POWEREDTTTTRRRRMAIN BAT BUSDC ISOLATIONRELAY (typical)DC TIE BUSBATTERY SWAPU HOT BAT BUSMAIN HOT BAT BUSAPU BATAPUCHARGERBATTERYMAINMAIN BATBATTERYCHARGERGND SERVICE BUSGND SERVICE SWAC BUS 1 POWEREDCOMBIMAIN DECK CARGO HANDLING BUS(FLT ATTENDANT PANEL)APU GEN 2EXT PWR 1EXT PWR 2APU GEN 1GND HANDLING BUS

DRIVE203

APU BAT BUSAPU BAT CHARGERAPU BATTERYMAIN STANDBY INVERTERDC BUS 1DC BUS 2DC BUS 3DC BUS 4BATTERYEXT PWR 1APU GEN 1APU GEN 2EXT PWR 2ONONAV A I LONCONDITION: NOELECTRICAL SYSTEM FAULTS.AUTOAUTOAUTOAUTOBUSTIEAC BUS 1AC BUS 2AC BUS 3AC BUS 4ONONONONGENCONTOFFOFFOFFOFF1234DRIVEDISCDRIVEDRIVEDRIVEDRIVEF/O TRANSFER BUSAC BUS 2POWEREDCAPT TRANSFER BUSAPU STBY BUSAC BUS 3POWEREDMAIN STBY BUSAPUSTANDBY INVERTERTTTTRRRRMAIN BAT BUSDC ISOLATIONRELAY (typical)DC TIE BUSBATTERY SWAPU HOT BAT BUSMAIN HOT BAT BUSMAINMAIN BATBATTERYCHARGERGND SERVICE BUSGND SERVICE SWAC BUS 1 POWEREDMAIN DECK CARGOHANDLING BUS(FLT ATTENDANT PANEL, DOOR 1L)APU GEN 2EXT PWR 1EXT PWR 2APU GEN 1GND HANDLING BUS

Intentionally Blank


ElectricalEICAS MessagesChapter 6Section 30

Electrical EICAS MessagesThe following EICAS messages can be displayed.

MessageLevelAuralCondition

>BAT DISCH APUAdvisoryAPU battery discharging.

>BAT DISCH MAINAdvisoryMain battery discharging.

>BATTERY OFFAdvisoryBattery switch OFF.

>DRIVE DISC 1,2, 3, 4AdvisoryGenerator Drive Disconnect switch pushed, IDG disconnected.

ELEC AC BUS 1, 2, 3, 4CautionBeeperAC bus unpowered.Additional related messages displayed for unpowered equipment items.

ELEC BUS ISLN 1, 2, 3, 4AdvisoryBus tie breaker open.Inhibited when ELEC AC BUS message displayed.

(SB changes 006 ; before SB, improved generator control units for added IDG protection not installed)


ELEC DRIVE 1, 2,3, 4AdvisoryIDG oil pressure low or oil temperature high.Inhibited when Generator Drive Disconnect switch pushed.

008, 203(SB changes 006 ; improved generator control units for added IDG protection installed)


ELEC DRIVE 1, 2,3, 4AdvisoryIDG oil pressure low, oil temperature high, or GCB open due to uncorrectable generator frequency fault.Inhibited when Generator Drive Disconnect switch pushed.

Copyright The Boeing Company. See title page for details.D6-30151-400October 1, 20046.30.1EICAS Messages


Electrical -


ELEC GEN OFF 1, 2, 3, 4AdvisoryGenerator control breaker open.Inhibited when ELEC AC BUS message displayed.


>ELEC SSB OPENAdvisorySplit system breaker (SSB) open when commanded closed.

006, 008


ELEC UTIL BUS L, RAdvisoryOne or more galley or utility busses unpowered, or Galley Emergency Power switch off.Busses may be unpowered due to electrical fault, or related Utility Power switch or Galley Emergency Power switch off.Inhibited during load shedding.

203


ELEC UTIL BUS L, RAdvisoryOne or more utility busses unpowered.Busses may be unpowered due to electrical fault, or related Utility Power switch OFF. Inhibited during load shedding.

203


>STBY BUS APUAdvisoryAPU standby bus not powered.

>STBY BUS MAINAdvisoryMain standby bus not powered.

006, 008


>STBY PWR OFFAdvisoryStandby bus not powered.


April 1, 2005

Electrical (B747 400)

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