PSG COLLEGE OF TECHNOLOGYME – Power Electronics & Drives

Dept. of EEE

STATIC EXCITATION OF SYNCHRONOUS GENERATOR

-BYR.RAMESH BABU(10MQ10)

J.NETTIKANTAIHA(10MQ04)RAJESH KUMAR(10MQ38)

PSG COLLEGE OF TECHNOLOGYME – Power Electronics & Drives

Dept. of EEESynchronous Machines

Synchronous generators or alternators are used to convert mechanical power derived from steam, gas, or hydraulic-turbine to ac electric power

Synchronous generators are the primary source of electrical energy we consume today

Large ac power networks rely almost exclusively on synchronous generators

Synchronous motors are built in large units compare to induction motors (Induction motors are cheaper for smaller ratings) and used for constant speed industrial drives

PSG COLLEGE OF TECHNOLOGYME – Power Electronics & Drives

Dept. of EEE

Number of Poles:The number of poles on a synchronous generator

depends upon the speed of rotation and desired frequency

P=120*f/n f = frequency of the induced voltage (Hz)p = number of poles on the rotorn = speed of the rotor (rpm)

3

PSG COLLEGE OF TECHNOLOGYME – Power Electronics & Drives

Dept. of EEE

1.Dynamic excitation-by using auxiliary generators

a) Dc excitation systemb)Ac excitation systemc)brushless excitation

2.Static excitation system-by using power electronics devices

Types of excitation

PSG COLLEGE OF TECHNOLOGYME – Power Electronics & Drives

Dept. of EEE

DC exciter: A DC generator mounted on the main shaft may be of either the shunt-wound or the separately-excited type. The output current is fed to the rotor of the synchronous machine through slip-rings.

AC exciter: The AC exciter is mounted on the main shaft. Its field is fed from a pilot exciter, The AC exciter output voltage is rectified and fed to the field of the synchronous machine via slip-rings.

Brushless excitation system:An exciter of rotating-armature type is mounted on the main shaft. The AC output is converted to DC by means of a rotating rectifier. The direct current is fed directly to the field winding of the synchronous machine.

PSG COLLEGE OF TECHNOLOGYME – Power Electronics & Drives

Dept. of EEEExcitation system

From excitation generator

To main generator

PSG COLLEGE OF TECHNOLOGYME – Power Electronics & Drives

Dept. of EEE

primover

generator

gridPower electronic converter

Firing pulse generator

C

vact

vref

Step down

T/f

Firing angle

controller

verrά

Primover

contoller

Cfgrid

fact

Micro processor

PSG COLLEGE OF TECHNOLOGYME – Power Electronics & Drives

Dept. of EEEFullwave rectifier

PSG COLLEGE OF TECHNOLOGYME – Power Electronics & Drives

Dept. of EEEControlle stategy

PSG COLLEGE OF TECHNOLOGYME – Power Electronics & Drives

Dept. of EEESemi converter

PSG COLLEGE OF TECHNOLOGYME – Power Electronics & Drives

Dept. of EEE

PSG COLLEGE OF TECHNOLOGYME – Power Electronics & Drives

Dept. of EEE

Advantages: Can be operated at desired power factor - Source of

reactive power Constant speed (motor) / frequency (generator)

with load changes High efficiency - Brushless applications – reliable

operation