The voltage regulator are composed of automatic voltage regulator(AVR), manual voltage regulator (MEC) and over current limiter(OCL)
Automatic voltage regulator (AVR)
An automatic voltage control device "senses" changes in output voltage and causes a change in field resistance to keep output voltage constant. The AVR is capable of covering 80% to 110% of the rated voltage of the generator at no-load operation.
Manual voltage regulator (MEC)
In case of AVR trouble, the voltage control system is set automatically from “automatic” (AVR) to “manual” (MEC). To trail charge the transmission line, the generator voltage is controlled stable from 30% of the rated voltage to the full voltage using MEC.