Answer / vikramsenareddy

Ans: From my real experience the voltage may not come to
zero, the volltage will fluctuate from one value to another
it may not constant at any time period. with this frequency
also increases drastically. due to this there is chance of
blown down of ACB fuses and coils.

Answer / v.d.vamshinath

There wont be any excitation to the main field other than
residual magnetism which is lost drastically(within
fraction of second) if AVR failed on load.
So voltage grops and may come down to zero.

If AVR fails when there is no load on alternator, the
residual magnetism will be sufficient to build some voltage
less than the rated voltage till it exists.

Answer / p.raju

The AVR scheme comes into operation only when there is a
change in loading.......
we have AVR scheme to regulate the changes in voltage level
at the alternator terminals, because of change in reactive
power loading.when AVR fails it will not increase the
voltage, thats why further decrease in voltage takes
place ..... which leads to final voltage collapse of the
system.

Answer / culla felix

when the AVR fails in the alternator there will be no device
that will control the flactuation of the output voltage the
same thing that there will be no device that will give the
voltage excitation in the field(rotor) of an alternator, only
the residual voltage will excite the field to build up more
strong fluxes, in that matter there will be no consistent
output voltage in the alternator

Answer / kumar

i have two year experience in this field i go with
VIKRAMSENAREDDY answer .ya his answer is perfect one.

Answer / pratap k s

it depends on the alternator field excitation circuitry. In
a brushless alternator with compound excitation the
alternator produces a high voltage around 440V with the AVR
disconnected and the AVR regulates the output volatge to a
set value say 400V even if the laod varies from 0 to 100%

Answer / satya

alternator trip at loss of exitation because it can not
biuld up exitation voltage to the field. its null meter
becomes 0 position.

Answer / emeka spark

I agree with Amritpal Singh Sidhu. i had similar
experience of AVR failure at the site few days ago and i
provided 12volts from the battery. innitially the voltage
was a bit higher than normal but i adjusted the governor of
the DG till i got a normal voltage.

Answer / amritpal singh sidhu

If AVR fails to work, then we troubleshoot the same by
providing the 12V DC from DG set battery to the field
winding of DG set. But in that case we should take care
that normal load can be put on, because the battery can not
regulate the voltage as the AVR done.

Answer / s f ali

Actually when AVR damages, although the engine is running on fine RPM you will not having voltages like your required. I personally observed that engine was running on fine RPM and I was getting 14 L-N voltages.......

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