An Introduction to Synchronous Alternator
-
Upload
pradeep-rajasekeran -
Category
Documents
-
view
239 -
download
0
Transcript of An Introduction to Synchronous Alternator
-
8/12/2019 An Introduction to Synchronous Alternator
1/44
AN INTRODUCTION TO
-
8/12/2019 An Introduction to Synchronous Alternator
2/44
What does BRUSHLESS Generator mean
30 years ago, A.C Generators were designed with SLIPRINGS and CARBONBRUSHES, to transfer power from the rotating component of the Generator.
BRUSHLESS Generators are designed to allow output to be taken from the GeneratorWITHOUT SLIP-RINGS AND BRUSHES.
These had a tendency to wear out, spark, burn, with vibration or high transient loadcurrents.
SLIPRINGS
CARBONBRUSHES
BEARINGS
NOW LETS LOOK AT A BRUSHLESS GENERATOR !!
OUTPUT
SHAFTA.C.ARMATURE
D.C. FIELD POLES
-
8/12/2019 An Introduction to Synchronous Alternator
3/44
Two Bearing Main Rotor AssemblyMain Rotor Fan
Bearing
Shaft
Rectifier
Exciter
Rotor
Bearing
PMG Rotor
Bearing Housings are built into the D.E and NDE Endbrackets
Bearings are sealed for life.
-
8/12/2019 An Introduction to Synchronous Alternator
4/44
Air flow through Generator
Air flow must not be restricted
-
8/12/2019 An Introduction to Synchronous Alternator
5/44
Excitation System - All Generator types
Bearing
Shaft
Rectifier
Exciter
Rotor
& Stator
Main Stator
Main Rotor
Fan
-
8/12/2019 An Introduction to Synchronous Alternator
6/44
Exciter
Stator
Excitation System - Exciter Stator
Bearing
Shaft
Rectifier
ExciterRotor
& Stator
Main Stator
Main Rotor
Fan
-
8/12/2019 An Introduction to Synchronous Alternator
7/44
High-remanence steel core
Stores Residual Magnetism12-14 pole magnet field
High frequency Generator
To A.V.R TerminalsXX- (F2)
X+ (F1)
Excitation System - Wound Exciter Stator
N S N S
COIL CONNECTIONS
-
8/12/2019 An Introduction to Synchronous Alternator
8/44
Exciter
Rotor
Excitation System - Exciter Rotor
Bearing
Shaft
Rectifier
Exciter
Rotor
& Stator
Main Stator
Main Rotor
Fan
-
8/12/2019 An Introduction to Synchronous Alternator
9/44
3 Phase A.C output, each Phase connected to 2 diodes on Main Rectifier.
High Frequency output, ( from12 to 14 Pole Exciter Stator ).
Exciter generator is a magnetic power amplifier for the main rotor current.
W
W
U
V
U
V
SHAFT
Excitation system - Exciter Rotor Assembly
-
8/12/2019 An Introduction to Synchronous Alternator
10/44
Exciter Rotor and
Main Rectifier
Circuit
Excitation System - Exciter Rotor/ Main Rectifier
Bearing
Shaft
Rectifier
Exciter
Rotor
& Stator
Main Stator
Main Rotor
Fan
-
8/12/2019 An Introduction to Synchronous Alternator
11/44
W
WU
V
U
V
SHAFT
Rectifier Assembly Mounted on Exciter rotor Core, (drive end side).
Wound Exciter Rotor
Exciter Rotor and Rectifier Assembly
Rectifier Assembly
SHAFT
-
8/12/2019 An Introduction to Synchronous Alternator
12/44
SHAFT
Exciter Rotor & Main Rectifier Assembly
Exciter Rotor 3 Phase
with Internal Star Point
-
8/12/2019 An Introduction to Synchronous Alternator
13/44
3 Phase A.C Exciter Rotor Connected to Rectifier input terminals
Exciter Rotor & Main Rectifier Connections
Rectifier Input Terminal
SHAFTSHAFT
-
8/12/2019 An Introduction to Synchronous Alternator
14/44
Bearing
Shaft
Rectifier
Exciter
Rotor
& Stator
Main Stator
Main Rotor
Fan
Main
Rectifier
Excitation System - The Main Rectifier
-
8/12/2019 An Introduction to Synchronous Alternator
15/44
SHAFT
Main Rectifier Assembly
Varistor
(Surge Suppressor)
3 Phase A.C Input
from Exciter Rotor.
(Insulated Terminals)
Rectifier Diodes
Positive PlateCathode Stud
Rectifier Diodes
Negative Plate
Anode Stud
Aluminium
Heat-sinks
Split Two-Piece
Rectifier Hub
-
8/12/2019 An Introduction to Synchronous Alternator
16/44
+VE
0
-VE
Main Rectifier Assembly- Operation of a Diode
Rectifier Diode
Positive Heatsink
Cathode Stud
Rectifier Diode
Negative Heatsink
Anode Stud
+VE
0
-VE
+VE
0
-VE
A.C Input to Rectifier Diodes
( 150 HZ to 180 HZ per second)
+
-
8/12/2019 An Introduction to Synchronous Alternator
17/44
Main Rectifier Assembly- 3 Phase Rectification
Full wave 3 Phase rectification will produce a D.C output of 1.35 X A.C input voltage
A.C Input to Rectifier Diodes (150 to 180HZ)
D.C output to Main Rotor+
-
-
8/12/2019 An Introduction to Synchronous Alternator
18/44
SHAFT
Metal Oxide Varistor (Surge Suppressor)
Clamping @ 100 Amp 1365 VoltsClamping @ 30 Amp 680 Volts
Diode Protection Device
For Transient Suppression
Main Rotor
ConnectionsSHAFT
-
8/12/2019 An Introduction to Synchronous Alternator
19/44
Metal Oxide Varistor (Surge Suppressor)
D.C supply
to Main rotor
Typical high voltage transient created byfault condition in the distribution system.
Up to 2- 3000V (peak voltage)
Varistor clamping(Protection) level.
Crash Synchronising onto live bus-bars.
Electric storm, (lightning), and field effects on
overhead lines (distribution systems).
Arcing, caused by faulty switching, motor
failure, short circuits in the distribution system.
Full load D.C
output from
main Rectifier
t = sec's.
Directionof transient
Energy absorbed
by Varistor.
High Transient surges can be created by:-
DIODE PROTECTION DEVICE
-
8/12/2019 An Introduction to Synchronous Alternator
20/44
Main Rotor
Excitation System - The Main Rotor
Bearing
Shaft
Rectifier
Exciter
Rotor
& Stator
Main Stator
Main Rotor
Fan
-
8/12/2019 An Introduction to Synchronous Alternator
21/44
SHAFT
Main Rectifier Connections to Main Rotor
D.C
Main Rotor
The Rectifier Output is a smooth D.C Supply across the Aluminium Heat Sinks
This is fed to the Main Rotor windings
Main RectifierAluminium
Heat-sinks
-
8/12/2019 An Introduction to Synchronous Alternator
22/44
Wound Main Rotor - Coil Group connections
S
S
N N
D.C InputFrom Main
Rectifier
The Rotor coils are connected in Series (4 Pole Rotor shown).
Each coil is reversed to the adjacent coil, producing the required polarity
ANTI CLOCK
ANTI CLOCK
CLOCKCLOCK
-
8/12/2019 An Introduction to Synchronous Alternator
23/44
Wound Main Rotor - Poles & Frequency
Main Stator Coils in Slots (section)
4 Pole Main Rotor
The NEGATIVE Pole of the 4 pole Rotor is directly under the slot, therefore the
coil conductors in this slot will be going fully NEGATIVE
Main Stator Core
(section)
Air Gap
N
NS
SHAFT
Consider the Coils in the slot at 12 O'clock position, marked with the ARROW.
1 Cycle
-
8/12/2019 An Introduction to Synchronous Alternator
24/44
-
8/12/2019 An Introduction to Synchronous Alternator
25/44
S
SN
SHAFT
The coil conductors in this slot will now be at the FULLY POSITIVE position
The Rotor has now rotated Clockwise 90 , until the POSITIVE Pole is DIRECTLYUNDERNEATH the 12 O'clock position.
The 4 Poles will produce 2 FULL CYCLES for each 360 FULL REVOLUTION.
1 Cycle
Wound Main Rotor - Poles & Frequency
Main Stator Coils in Slots
4 Pole Main Rotor
Main Stator Core
Air Gap
-
8/12/2019 An Introduction to Synchronous Alternator
26/44
N
N
S
SHAFT
4 Pole 2 Pole
Generator Frequency (HZ) = Speed (N) X Pairs of poles (P)
60
SHAFT
N
6 Pole Available
in Frame 7
Wound Main Rotor - Poles & Frequency
-
8/12/2019 An Introduction to Synchronous Alternator
27/44
Generator Frequency (HZ or CYCLES) = Speed (N) X Pairs of poles (P)
60
2 Pole 1 HZ =4 Pole 1 HZ = 30 RPM
6 Pole 1 HZ =
60 RPM
20 RPM
Wound Main Rotor - Poles & Frequency
FRQUENCY
HZ (CYCLES)
50
50
50
60
60
60
NUMBER
POLES (P)
2
4
6
2
4
6
ENGINE
SPEED (N)
3000
1500
1000
3600
1800
1200
-
8/12/2019 An Introduction to Synchronous Alternator
28/44
N
N
S
SHAFT
(Damper Bars)
(Aluminium Damper Bars Welded to End Plates )
Main Rotor- Amortisseur (Damper) Windings
-
8/12/2019 An Introduction to Synchronous Alternator
29/44
Stabilises the mechanical systems during large load changes.
Stabilises load sharing with other Generators in Parallel.
Improves Harmonic Distortion in the Generator waveform
Helps dampen speed oscillations resulting from cyclic irregularities in
the engine, (cause of light flicker).
Main Rotor- Amortisseur (Damper) Windings
N NS
SHAFT
-
8/12/2019 An Introduction to Synchronous Alternator
30/44
Bearing
Shaft
Rectifier
Exciter
Rotor
& Stator
Main Stator
Main Rotor
Fan
Main Stator
Operation - Main Stator
Wound Main Stator Assembly
-
8/12/2019 An Introduction to Synchronous Alternator
31/44
Wound Main Stator Assembly
Core built from high grade Electrical Steel, to reduce Iron losses (heat).
Each lamination is electrically insulated to minimise Eddy Currents in the core.
12 Ends Out Re-connectable, 6 Ends out Star / Delta, or Dedicated Windings.
Class H Insulation as standard, 125 C Temperature rise in 40 Ambient. 2/3rds Pitch windings, Harmonics virtually eliminated.
Laminated Steel core Copper Windings
Output Leads
-
8/12/2019 An Introduction to Synchronous Alternator
32/44
Wound Main Stator Assembly
OUTPUT
CONDUCTORS
COIL PHASE GROUP
OUTPUT CONDUCTORS
Stator Winding Coils (Lap winding)
The output voltage of the stator is determined by the number of turns per coil, thestator core length, the velocity of the magnetic field (rotor), and the strength of the
magnetic field.
The Current capacity of the coil is determined by the conductor cross sectional
area, and number of conductors in parallel.
STATOR
CORELENGTH
COIL END
(OVERHANG)
COILTURNS
COIL
SPAN
(PITCH)
S
-
8/12/2019 An Introduction to Synchronous Alternator
33/44
MAIN ROTOR
(4 POLE)
WINDING LEADS
FINISH OF COIL
GROUP
Typical Main Stator 12 Wire Re-connectable
WINDING LEADS
START OF COIL
GROUP
N
N
S
SHAFT
MAIN STATOR WINDING
SECTION ( 48 SLOT )
2/3RDS PITCH
8 SLOTS
( SPAN 1 TO 9)
ONE PHASE GROUP
( 4 COILS PER GROUP)
FULL PITCH
12 SLOTS
( SPAN 1 - 13)
-
8/12/2019 An Introduction to Synchronous Alternator
34/44
U
V
W
N V6
W1
V1
U1
AVR Sensing
& Power supply
from Main Stator
3 Phase Output
Neutral
Connections shown in Series Star
Typical Main Stator 12 Wire Re-connectable
6
7
8
W d M i St t 12 Wi R t bl
-
8/12/2019 An Introduction to Synchronous Alternator
35/44
Wound Main Stator 12 Wire Re-connectable
Voltage Range
380 to 440 V @ 50 HZ
416 to 480 V @ 60 HZ
Voltage Range
190 to 220 V @ 50 HZ
208 to 240 V @ 60 HZ
V5
Parallel Star
U1
U2 U6
U5
V2
W2
W5
V6
V1
W1
W6
vw
U
N
6
8
7
Series Star
U1
U2
U6
U5
V2W2
W5
V6
V1W1V5
W6
U
w v
N
8
7
6
The stator windings are connected into six groups.
The groups can be connected by Newage, or the customer, to provide different voltage
requirements.
Special Voltage requirements require special windings, e.g.; 690 Volt for Co-Generation.
W d M i St t 12 Wi R t bl
-
8/12/2019 An Introduction to Synchronous Alternator
36/44
Voltage Range
220 to 250 V @ 50 HZ, 240 to 277 V @ 60 HZ
No Neutral connection.Centre Tap for low volts 1ph only
Voltage Range
220 to 250 V @ 50 HZ, 240 to 277 V @ 60 HZ
Single Phase Only, output across U & WCentre Tap (N) for low volts
110 to 125 @ 50 HZ, 120 to 138 @ 60 HZ
Wound Main Stator 12 Wire Re-connectable
Double Delta
N
7
6
8
Series Delta
Centre
Tap
6
8
7
W d M i St t 6 E d O t
-
8/12/2019 An Introduction to Synchronous Alternator
37/44
Wound Main Stator 6 Ends Out
Star
Number of Stator leads in parallel
increases with current rating
of generator,
ie: 12, 18, 24, 36, or 48 leads out.
Voltage Range380 to 440 V @ 50 HZ , 416 to 480 V @ 60 HZ
Single Phase (N) = 3 of Phase voltage
Dropper transformer required
for AVR sensing
U
U1
U2
V2W2
V1W1
w v
N
76
8
Each phase group is producing the full line voltage, (all coil groups in each phase are in
parallel).
W d M i St t 6 E d O t
-
8/12/2019 An Introduction to Synchronous Alternator
38/44
The AVR Sensing supply is connected to the main stator via a sensing
isolation transformer, which is fitted in the main terminal box.
Sensing Supply to A.V.R for STAR connection
U
U1
U2
V2W2
V1W1
w v
N
7
6
8
7
6
Isolation transformer
Other windings producing higher voltage requirements will require a different
transformer ratio, to supply the AVR with the correct voltage adjustment range
Examples - 6 ends Stators380 to 440 V @ 50 HZ
416 to 480 V @ 60 HZ
Single Phase (N) = 3 of L-L
Wound Main Stator 6 Ends Out
8
-
8/12/2019 An Introduction to Synchronous Alternator
39/44
Main Stator Windings -Voltage Ranges
The output voltage of the generator is set by adjustment of the AVR
Voltage trimmer.
The potential voltage range of the AVR can be much higher or lower than
the design limits for the Generator windings.The Voltage Range is decided by many inter-dependant design
considerations.
Main Stator Windings Voltage Ranges
-
8/12/2019 An Introduction to Synchronous Alternator
40/44
Main Stator Windings -Voltage Ranges
D.C Excitation Current
Output Voltage
From Generator
Minimum Flux Level
Maximum flux level
Middle flux level
0
Generator Output Voltage
Open Circuit Magnetisation Curve
Each Winding is designed to operate within a specified Voltage Range.
The Generator must operate within the Optimum Voltage Range for the Windings.
Saturation
OPEN CIRCUIT MAGNETISING CURVE
Excitation System Self Excited Generators
-
8/12/2019 An Introduction to Synchronous Alternator
41/44
X+ (F1)
XX- (F2)D.C Output
From A.V.R
IntoExciter Stator
A.C Power &
Feedback Signal
(Sensing)From Main Stator
Excitation System - Self Excited Generators
A.V.R
Bearing
Shaft
Rectifier
Exciter
Rotor
& Stator
Main Stator
Main Rotor
Fan
E i i S S lf E i d G
-
8/12/2019 An Introduction to Synchronous Alternator
42/44
Exciter Rotor
Main
Rectifier
Exciter Stator
( Residual Magnetism)
AVR Input Power & Sensing
170 - 250 Volts
A.C. 2 or 3 Phase sensing
AVR Output D.C
Magnetic Flux
Excitation System - Self Excited Generators
D.C
3ph A.C
to
D.C
Main Rotor
D.C.
Main Stator1 or 3 ph. A.C.
A.V.R
Automatic
Voltage
Regulator
Shaft
X+ XX-
To Load Terminals
Generator Output
A.C. 50 or 60 HZ
A.C
S t l E it d G t
-
8/12/2019 An Introduction to Synchronous Alternator
43/44
Separately Excited Generators
ADVANTAGES OF SEPARATE EXCITATION SYSTEM
UNAFFECTED BY ADVERSE LOADING CONDITIONS SUCH AS
WAVEFORM DISTORTION CAUSED BY NON LINEAR LOADS
POWERFUL VOLTAGE BUILD UP SYSTEM ON INITIAL RUN-UP
(DOES NOT RELY UPON RESIDUAL MAGNETISM)
SUSTAINED SHORT CIRCUIT CURRENT UNDER FAULT CONDITIONS,(REQUIREMENT FOR ALL MARINE CLASSIFICATIONS).
ISOLATED POWER SUPPLY FOR THE AVR.
(PROTECTS AVR FROM TRANSIENT CONDITIONS IN THE DISTRIBUTION SYSTEM)
CAPABLE OF VOLTAGE BUILD UP AGAINST LOAD
(FREQUENCY STARTING OF LARGE MOTORS).
-
8/12/2019 An Introduction to Synchronous Alternator
44/44
THANK U
Manufactu ring Eng ineering Department (MED)