An automatic voltage regulator is a thyristor type voltage controller which will maintain the output voltage of the alternator whenever voltage fluctuations occur due to varying loads. AVR achieved this by controlling the excitation of the alternator. Whenever a voltage dip occurs then it will increase the excitation and vice versa.
There are following main functions of an AVR
In the context of power system, suppose you are generating electricity at V volts. It is highly essential that the voltage always remain at V volts no matter what happens. In order to achieve it we use AVR.
AVR senses the o/p voltage and transmits it to a comparator which compares V with the present output. The error if present is amplified and fed to the field generator which adjusts its o/p current which in turn adjusts the main field of the generator and maintains the voltage at V volts all the time.
It protects your sensitive electronic equipment from brownouts and over-voltages. Uncorrected voltage fluctuations gradually degrade the life of electronic components, potentially causing premature failure. An AVR not only adjusts voltages to safe levels, but also provides surge protection against electrical surges and spikes and lightning