AUTOMATIC VOLTAGE REGULATOR

An Automatic Voltage Regulator (AVR) is a device that regulates the voltage. It takes fluctuating voltage and changes it into a constant voltage. The fluctuation in voltage mainly occurs due to the variation in load on the supply system. The AVR works on the principle of error detection. The output voltage of an AC generator is obtained through a potential transformer, then it is rectified, filtered, and compared with a reference. The difference between the actual voltage and the reference voltage is known as the error voltage. This error voltage is amplified and then supplied to the main exciter or pilot exciter. Thus, the amplified error signals control the excitation of the main or pilot exciter through a buck or a boost action (i.e., controls the fluctuation of the voltage). Exciter output control leads to the control of the main alternator terminal voltage.