How works the AVR in DG Sets Plz explain??????????

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How works the AVR in DG Sets Plz explain??????????..

The AVR derives its power supply from the line to neutral
terminals of the AC Generator,at a level of 240V AC RMS at
50/60 hz.The sensing voltage,which is regulated voltage is
derived from the line to line terminals of the AC
Generator.The AVR forms an important part of the closed loop
system comprising of the generator field,generator armature
and the AVR.

The AVR,first builds up the generator voltage from its
residual levels to the rated value of 415V.when the
generator is loaded,the sensed voltage goes down and
generates the error voltage,which is required to drive the
closed loop system.The AVR contains a high gain
amplifier,ramp and pedestal circuitry.depending upon the
value of the amplified voltage either high or low the ramp
intersects the amplified volatage at a point which is early
or late in the half cycle.at the intersection point,a firing
pulse is produced to trigger the power device.

When the power device is trigerred early in the half
cycle,more voltage is let into the field and when trigerred
late in the half cycle,less voltage is let into the field.

in order to reduce the generated voltage at lower speed,a
signal inversely proportion to the speed is fed as an extra
input.At higher speeds,the effect is nil while at lower
speeds the voltage reduces more than proportionate with the
speed.