Automatic Voltage Regulator

Automatic Voltage Regulator

•The automatic voltage regulator is used to regulate the voltage. 

• It takes the fluctuate voltage and changes them into a constant voltage. 

• The fluctuation in the voltage mainly occurs due to the variation in load on the supply system. 

• The variation in the voltage damages the equipment of the power system which can be controlled by installing the voltage control equipment at several places likes near the transformers, generator, feeders, etc.

• The voltage regulator is provided in more than one point in the power system for controlling the voltage variations.

Working Principle of Voltage Regulator

• It works on the principle of detection of errors. 

• The output voltage of an AC generator obtained through a potential transformer and then it is 

rectified, filtered and compared with reference. 

• The difference between the actual voltage and the reference voltage is known as the error voltage. 

• This error voltage is amplified by an amplifier 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 boost action (i.e. controls the fluctuation of the voltage).

• Exciter output control leads to the controls of the main alternator terminal voltage.

The main functions of an AVR are as follows:

• It controls the voltage of the system and has the operation of the machine nearer to the steady state stability.

• It divides the reactive load between the alternators operating in parallel.

• The automatic voltage regulators reduce the overvoltage's which occur because of the sudden loss  of load on the system.

• It increases the excitation of the system under fault conditions so that the maximum synchronizing power exists at the time of clearance of the fault.