an introduction to synchronous alternator

8/12/2019 An Introduction to Synchronous Alternator

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AN INTRODUCTION TO


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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


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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.


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Air flow through Generator

Air flow must not be restricted


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Excitation System - All Generator types

Bearing

Shaft

Rectifier

Exciter

Rotor

& Stator

Main Stator

Main Rotor

Fan


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Exciter

Stator

Excitation System - Exciter Stator

Bearing

Shaft

Rectifier

ExciterRotor

& Stator

Main Stator

Main Rotor

Fan


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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


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Exciter

Rotor

Excitation System - Exciter Rotor

Bearing

Shaft

Rectifier

Exciter

Rotor

& Stator

Main Stator

Main Rotor

Fan


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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


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Exciter Rotor and

Main Rectifier

Circuit

Excitation System - Exciter Rotor/ Main Rectifier

Bearing

Shaft

Rectifier

Exciter

Rotor

& Stator

Main Stator

Main Rotor

Fan


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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


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SHAFT

Exciter Rotor & Main Rectifier Assembly

Exciter Rotor 3 Phase

with Internal Star Point


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3 Phase A.C Exciter Rotor Connected to Rectifier input terminals

Exciter Rotor & Main Rectifier Connections

Rectifier Input Terminal

SHAFTSHAFT


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Bearing

Shaft

Rectifier

Exciter

Rotor

& Stator

Main Stator

Main Rotor

Fan

Main

Rectifier

Excitation System - The Main Rectifier


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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


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+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)

+


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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+

-


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SHAFT

Metal Oxide Varistor (Surge Suppressor)

Clamping @ 100 Amp 1365 VoltsClamping @ 30 Amp 680 Volts

Diode Protection Device

For Transient Suppression

Main Rotor

ConnectionsSHAFT


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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


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Main Rotor

Excitation System - The Main Rotor

Bearing

Shaft

Rectifier

Exciter

Rotor

& Stator

Main Stator

Main Rotor

Fan


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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


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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


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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


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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


Main Stator Coils in Slots

4 Pole Main Rotor

Main Stator Core

Air Gap


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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



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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


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


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N

N

S

SHAFT

(Damper Bars)

(Aluminium Damper Bars Welded to End Plates )

Main Rotor- Amortisseur (Damper) Windings


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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


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Bearing

Shaft

Rectifier

Exciter

Rotor

& Stator

Main Stator

Main Rotor

Fan

Main Stator

Operation - Main Stator

Wound Main Stator Assembly


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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


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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


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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)


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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


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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


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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


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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


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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


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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


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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


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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


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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


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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).


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THANK U

Manufactu ring Eng ineering Department (MED)

an introduction to synchronous alternator

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