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What is Automatic Voltage Regulator (AVR)?

Automatic Voltage Regulator (AVR): Here, we are going to learn about the Automatic Voltage Regulator, its working principle, etc.
Submitted by Anushree Goswami, on January 15, 2021

AVR: Automatic Voltage Regulator

AVR is an abbreviation of an "Automatic Voltage Regulator". It is an electronic piece of equipment that works automatically for mechanically upholding generator output terminal voltage at a fixed value under unstable and changeable load and operating temperature. It is used basically to control and regulate the voltage. It obtains the fluctuating voltage and transforms them into an unvarying stable voltage. In the voltage, the fluctuation generally takes place due to the difference in load on the system of supply. The difference or variation in voltage breaks or spoils the equipment of the power system. The difference or variation in the voltage can be managed and controlled by setting up the voltage control equipment at a number of places such as close to the transformers, generator, feeders, etc.

During the regulation of voltage, there are two conditions that take place, which are given in the following:

• Under Excitation:
  1. The condition of under excitation is a condition of the generator whose gain is too small due to small reinforcement so that it will supply the current to the system.
  2. In the condition, when the generator is less amplified, it required to supply a long-delayed current to the system for the reason that the long-delayed current will generate an anchor flux that will reinforce the rotor flux.
• Over Excitation:
  1. The condition of overexcitation is a condition of the generator whose gain is too huge due to huge amplification so that it will supply a delaying current to the system.
  2. In the condition, when the generator is highly amplified, it required to supply a delaying current to the system for the reason that the delaying current will generate an anchor flux that will offset the rotor flux to diminish strengthening that is excessively huge.

Working Principle

• The working principle of AVR, follow the process of identification of errors.
• The output voltage of an AC generator is gained through a potential transformer and then it is fixed, sorted out, and contrasted with a reference.
• The variation between the actual voltage and the reference voltage is known as the error voltage.
• The supply to the main exciter or pilot exciter is done after this error voltage is amplified by an amplifier.
• Therefore, the amplified error signals manage and control the excitation of the main or pilot exciter through resistance or an enhancement action.
• Exciter output control directs to the controls of the main alternator terminal voltage.

Reference: Voltage regulator

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