What is Automatic Voltage Regulator(AVR)?

What is Automatic Voltage Regulator(AVR)?

An automatic voltage regulator (AVR) is a component that regulates and maintains an electric generator’s or alternator’s output voltage within a predetermined range. It is used to stabilise the generator’s output voltage in order to ensure that it maintains a fixed level despite changing load conditions.

The generator’s output voltage is continually monitored by the AVR, which then modifies the excitation current sent to the field winding. This regulates the generator’s output voltage by regulating the generator’s magnetic field intensity. The AVR may change the excitation current up (or) down as necessary to keep the output voltage constant within the designated range.

Automatic Voltage Regulator (AVR) construction

A power generator’s voltage output is controlled by an AVR, which maintains the voltage constant despite changes in the load and input voltage. The following steps are involved in building an AVR:


The transformer is the first part used in the production of an AVR. It is used to reduce the input power supply voltage to a level that the AVR can process. The transformer has to be able to handle the highest load & input voltage anticipated.


A rectifier transforms the AC voltage from the transformer’s output into DC voltage. Depending on the application, the rectifier may be either a half-wave or a full-wave rectifier.

Voltage regulator:

A voltage regulator circuit receives the rectified DC voltage and regulates it to provide a consistent output voltage regardless of changes in the input voltage (or) load. An analogue or digital circuit may be used as the voltage regulator.

Feedback circuit:

A feedback circuit, which is coupled to the voltage regulator circuit, keeps track of the output voltage and modifies the voltage regulator as required to maintain a constant output voltage.

Output circuit:

The voltage regulator circuit provides the regulated voltage to the output circuit, which then feeds it to the load.

Protection circuit:

A safety circuit for the load against overvoltage, undervoltage, & overcurrent situations should also be included of the AVR.

Depending on the exact application and required voltage, an AVR’s structure may change. The majority of AVR designs, however, often comprise the aforementioned parts.

Working of an Automatic Voltage Regulator (AVR)

An Automatic Voltage Regulator’s (AVR) operation consists of the following steps:


The output voltage of the generator (or) alternator is continually monitored by the AVR.


The target output voltage, also known as a reference voltage or set point, is contrasted with the voltage being monitored.

Error Detection:

Any output voltage variation from the set point is identified and recorded as an error signal.


The control circuit of the AVR then amplifies the incorrect signal.

Control Signal:

The excitation current transmitted to the generator’s field winding is subsequently managed using the amplified error signal. In order to maintain the proper output voltage, the AVR adjusts the excitation current upward or downward as necessary.


In order to maintain the required output voltage, the AVR continually checks the output voltage & modifies the excitation current, delivering a steady and reliable power supply.

Overall, the AVR functions as a closed-loop control system, continuously regulating the excitation current to maintain a constant output voltage despite changes in load circumstances or other potential output voltage-affecting variables.

Application of an Automatic Voltage Regulator (AVR)

For a steady and dependable power supply, AVRs are often employed in power plants, industrial settings, and in backup generators. They can be found in household voltage stabilisers, which protect electrical equipment from voltage variations and surges.