Answer Posted / joy banerjee

In transformers Output Voltage can be controlled either by
Off Circuit Tap Changer (Manual tap changing)or By On -
Load Tap Changer-OLTC (Automatic Changing).

In the transformer with OLTC, it is a closed loop system,
with follwing components:

#1. AVR (Automatic Volatge Regulator- an electronic
programable device). With this AVR we can set the Output
Voltage of the transformers. The Output Voltage of the
transformer is fed into the AVR through the LT Panel. The
AVR Compares the SET voltage & the Output Voltage and gives
the error signal, if any, to the OLTC through the RTCC
Panel for tap changing. This AVR is mounted in the RTCC.

#2. RTCC (Remote Tap Changing Cubicle):This is a panel
consisting of the AVR, Dispaly for Tap Position, Voltage,
LEDs for Raise & Lower of Taps relays, Selector Switches
for Auto Manual Selection... In AUTO MODE the voltage is
contrlled by the AVR. I manual Mode the operator can
Increase / decrease the voltage by changing the Taps
maually through the Push Button in the RTCC.

#3. OLTC is mounted on the transfomer. It consits of a
motor, controlled by the RTCC, which changes the Taps in
the transformers.

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