What is the working of AVR in AC generators?

Answer Posted / geeparthi

AVR's are normally used in the Diesel Generators.They are
used to control the output voltage depending upon load
connected , such that, the load will not cause any voltage
fluctuation and damage to the DG.
Automatic Voltage Regulator.It is
important part in Synchronous Generators, it controls the
output voltage of the generator by controlling its
excitation current. Thus it can control the output Reactive
Power of the Generator.
AVR increase or decrease excitation voltage for linear
voltage.Frequency depends on primover speed.
It is a device used to maintain a constant voltage at the
alternators terminals. It functions by maintaining the
excitation required to maintain the terminal voltage of the
alternator with change in the load.

Increase in excitation voltage increases reactive voltampere
(var) which decreases powerfactor (cos(phi)).

generally, voltage(V) of the alternator is kept constant so
thE rest of the components in VIcos(phi), ie. I and cos(phi)
have to vary according to the load.

Increase in I causes decrease in Pf and Decrease in I causes
increase in Pf.

so it is clear that Excitation V is proportional to var and
load current (I) and inversely proportional to power
factor(cos(phi)).

AS the name itself indicates it is a device which maintains

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