Answer / thillai natarajan

practically,Synchronous Generator operated by DC self
excitation.
Totally , It consist of Synchronous generator, PMT
generator,rotating rectifier,AVR,External rectifier and
Battery arrangements.

The rotor(excitation winding) of the synchronous generator
is connected along with rotating rectifier and Permanent
magnetic generator in the same Driving shaft ,
The permanent magenatic generator generates AC Supply in
this rotor, This 3Phase AC Supply is converted into DC
supply by Rotating rectifier,
then,this DC source feed to Rotor winding (Excitation)of
Synchronous generator.
then,Synchronous generator generate the Final 3 Phase AC
supply from stator winding.
The Automatic voltage regulator(AVR) is get two DC Supply
source ,one is from DC Battery and another from External
Rectifier(AC supply from Synchronous generator is
converted into DC output),The function of AVR is maintain
Constant DC source and feed to stator of the PMT generator.

Answer / lubaba noor

I am describing function of AVR. AVR senses the terminal
voltage.If the terminal voltage is higher or lower than the
rated voltage,then AVR controls the flux.for example if the
terminal voltage is lower,AVR controls the switching of the
ckt in such a way that draws more voltage from DC src in
the rotor ckt.

Answer / kumar

AVR means automatic voltage regulator
AVR is heart of generator .initially generator produce
residual voltage only by prime mover that voltage it’s near
5 to 10% of rated voltage so we using AVR for buildup the
generator voltage. Its produce DC field voltage is also
called excitation voltage. That field voltage is fed to
excitor of generator and is converting into dc by RR
(rotating rectifier) RR output fed to main rotor depend
upon the field voltage generator produce voltage & that
output voltage we should fed as reference voltage to AVR
through transformer then depending upon the reference AVR
buildup & maintaining the constant of generator output
voltage . AVR require dc supply for operation so we require
battery or some DC source. In some standard generator they
provide AVR also otherwise we can design as per generator
excitation voltage but if you take any AVR mainly its
require dc input, generator output reference & AC auxiliary
supply.any more answer ????????

BY
kumar (AVR panel service engg )

Answer / akash mishra ( steam turbine,

Modern day practice is to use brushless excitation system. In this system Alternator, Main Exciter and PMG are mounted at the same shaft. PMG is a permanent magnet generator which generates 3 phase voltage of 150-250 volts at 100-200 HZ ( example TPDS Alternator PMG 150 Hz, Andritz Alternator PMG 100 HZ). This output voltage of PMG is feed to AVR and it act as a input power for thyristor bridge rectifer inside it. AVR is a microcontroller based device which senses terminal voltage of alternator with the help of PT ( generally 11000/110 volts PH-PH) AVR decides the firing angle of thyristor bridge depending upon the error signal generated (Setpoint minus actual value). This controlled DC output of AVR is feed to exciter field winding (stationary) which in turn induces voltage in exciter armature. The output voltage of exciter armature is connected to generator main field winding via Rotating rectifier assembly ( RRA Diode bridge). Hence the main field winding current is controlled in a closed loop manner. AVR continuously monitors terminal voltage of alternator and always tries to maintain the setpoint ( 11KV) equal to actual value. In this way AVR maintains the terminal voltage of alternator at a fixed value irrespective of variation of loads.

Answer / yengeshwar patel

What is the function of AVR in the synchronous generator?
An automatic voltage regulator (AVR) is a solid-state electronic device for automatically maintaining generator output terminal voltage at a set value. It will try and do this as the generator load or operating temperature changes. The AVR is part of the alternators excitation system.

Answer / john

You can read theory and solve objective type questions
related to synchronous generator here :

http://www.electricalquizzes.com

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