Introduction of Automatic Voltage Regulator for Diesel Generator

An automatic voltage regulator, commonly referred to as an AVR, is essentially a solid-state electronic device used in diesel generators.The AVR is designed to facilitate the automatic maintenance of the voltage at the generator output at a preset value, particularly in the event of a change in generator load or a change in generator operating temperature. In simple terms, the AVR can be described as an integral part of the alternator excitation system. the AVR is essentially a part of the alternator. Here, the type of AVR supplied with the alternator depends greatly on the type and the accessories installed on the alternator.

AVR placement in diesel generators

In general, the automatic voltage regulator can be found anywhere mentioned below (1) in the main generator control box

(2) in the alternator junction box (3) under the rear cover of the alternator (usually in the case of small portable generator sets)　　

How does the AVR of a diesel generator work?

The main function of the AVR is to control the alternator output voltage. It does this by first detecting the voltage from the alternator terminals and then comparing it to a preset stable reference value to check for error signals (if any). If there is a difference between the two, the ACR adjusts the excitation current by increasing or decreasing the current flowing to the exciter stator. This in turn ensures that the voltage at the main stator terminals is lower or higher.

As you may have understood by now, the AVR is used as a regulating device to ensure that the voltage output of the alternator remains within a predefined range. Thus, it ensures that the alternator voltage never drops to a level that would cause any connected electrical equipment or electrical devices to malfunction. It also helps to keep the alternator from running low on battery power.　

Adjustment of the alternator output becomes critical when the alternator speed changes - this occurs primarily when the alternator engine speed changes, as the alternator to engine ratio is fixed. A stable voltage during this time ensures the safe operation of both - the electrical equipment supplying the power as well as the alternator battery.

Types of Automatic Voltage Regulators

According to the operating principle and application, AVRs can be broadly classified into the following categories

Contact type automatic voltage regulator

In this type of AVR, the regulator contact vibration frequency is relatively slow, resulting in a lower voltage regulation accuracy. It is for this reason, as well as the relatively short service life, that contact AVRs are no longer used in  alternators.

Transistorized Automatic Voltage Regulator

Transistor AVRs were developed with the development of semiconductor technology. These regulators are characterized by high transistor switching frequency, high regulation accuracy, high reliability, and low radio interference.

IC Automatic Voltage Regulators

IC regulators, also known as integrated circuit regulators, offer all the advantages of transistor regulators. In addition to this, it has the benefit of an ultra-small size, which reduces the need for any external wiring and thus enhances its cooling effect.

Computer-controlled automatic voltage regulators

The computer-controlled regulator depends primarily on the total load current of the system communicating with the generator computer. Here, the engine computer ensures that the magnetic field circuit is turned on and off in a timely manner according to the set values, allowing the electrical system to operate properly.

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