AVR Full-Form | What is Automatic Voltage Regulator (AVR)

Where is an AVR located in a generator? Normally the generator AVR is located in one of three places. It can be in the main control box of the generator, it can be in the alternators terminal box and it could be (only on very small portable units usually) located under the alternators rear cover.

Questions & Answers on AVR Unit

An automatic voltage regulator (AVR) is an electronic device that maintains a constant voltage level to electrical equipment on the same load. The AVR regulates voltage variations to deliver constant, reliable power supply.

In general, there are two types of an Automatic Voltage Regulator. One is the Relay Type and the other is the Servo Motor type. A Relay type AVR makes use of electronic circuitry like relays and semi-conductors to regulate the voltage.

As the speed of the engine the generator increases, the voltage produced also increases. The excitation system monitors the generator output and regulates the magnetic field to maintain the desired voltage. As the load on the generator is increased, an increase in current flow causes the voltage to drop.

Droop speed control is a control mode used for AC electrical power generators, whereby the power output of a generator reduces as the line frequency increases. It is commonly used as the speed control mode of the governor of a prime mover driving a synchronous generator connected to an electrical grid.

Speed droop is a governor function which reduces the governor reference speed as fuel position (load) increases. All engine controls use the principle of droop to provide stable operation. Without some form of droop, engine-speed regulation would always be unstable. A load increase would cause the engine to slow down.

It is reported and known that power plants machines in VAr/PF control mode caused/contributed to system voltage collapse. The purpose of the AVR is to support system voltage. If you are in VAR/PF control you will do nothing to prevent a voltage collapse.

You can improve power factor by adding power factor correction capacitors to your plant distribution system. When apparent power (kVA) is greater than working power (kW), the utility must supply the excess reactive current plus the working current . Power capacitors act as reactive current generators .

The voltage regulation of the transformer is the percentage change in the output voltage from no-load to full-load. And since power factor is a determining factor in the secondary voltage, power factor influences voltage regulation. This means the voltage regulation of a transformer is a dynamic, load-dependent number.

The primary means of generator reactive power control is the generator excitation control using Automatic Voltage Regulator (AVR). The purpose of AVR is to hold the terminal voltage magnitude of a synchronous generator at specified level.

The steady state voltage and reactive power control in distribution systems can be properly controlled by coordinating the available voltage and reactive power control equipment, such as on-load tap-changers, substation shunt capacitors and feeder shunt capacitors.