Composition and Classification of Synchronous Generator Excitation System

The excitation system of a synchronous generator is a general term for the equipment that provides DC magnetic field current for the synchronous generator. It is an important part of the generator and directly affects the operating characteristics of the generator. The excitation control system is a feedback control system composed of the excitation system and its control object (the synchronous generator).

I. Composition of the Synchronous Generator Excitation System

1.Power Supply: It provides power for the excitation power rectifier unit. In a self - shunt excitation system, an excitation transformer is generally used.

2.Power Rectification: This part supplies DC excitation current to the rotor winding of the synchronous generator.

3.Regulating Controller: It is a device that controls the output of the excitation power unit according to the input signals required by the control and the given regulation criteria. It senses the changes in the generator voltage and operating conditions and automatically adjusts the magnitude of the excitation current output by the excitation power unit to meet the requirements of system operation.

4.Demagnetization and Initial Excitation: The function of demagnetization is to quickly cut off the generator's excitation and rapidly consume the magnetic field energy stored in the excitation winding when accidents such as short - circuits and grounding occur inside or outside the generator. The function of initial excitation is to provide the initial excitation current for the generator rotor winding.

5.Generator Rotor: It provides a rotating magnetic field for the generator.

II. Classification of the Synchronous Generator Excitation System

1. Classification by Excitation Power Source

DC exciter excitation system

AC exciter excitation system

Self - shunt excitation system

2. Classification by Response Speed

Slow - response excitation system

Fast - response excitation system

High - initial - response excitation system

(1) AC Exciter System (Three - Machine Separately - Excited)

Composition: Both the main AC exciter (ACL) and the auxiliary AC exciter (ACFL) are coaxial with the generator. The auxiliary exciter is self - excited, and its field winding is powered by the rectified voltage at the terminal of the auxiliary exciter. A permanent - magnet generator can also be used as the auxiliary exciter, which is also called a three - machine separately - excited excitation system.

Advantages: Since it is separately - excited, the excitation power is not affected by the system power supply.

Disadvantages: Slow adjustment speed, long shafting length, and prone to shafting oscillation.

(2) AC Exciter System (Two - Machine Separately - Excited)

Composition: The main AC exciter supplies excitation current to the generator rotor circuit through a thyristor rectifier device. The automatic voltage regulator (AVR) controls the firing angle of the thyristors to adjust the output current, which is also called a two - machine separately - excited excitation system. There is no auxiliary exciter in this excitation system. The excitation power of the AC exciter is obtained from the generator terminal voltage through an excitation transformer. The automatic excitation regulator controls the firing angle of the thyristors to adjust the excitation current of the AC exciter. The output voltage of the AC exciter is rectified by silicon diodes and then connected to the generator rotor, which is also called a two - machine and one - transformer excitation system.

Advantages: The elimination of the auxiliary exciter shortens the shafting length.

Disadvantages: Slow adjustment speed.

(3) Self - Excitation System (Shunt - Excited, Compound - Excited)

Composition: It consists of an excitation transformer, a high - power thyristor rectifier cabinet, demagnetization and over - voltage protection devices, initial excitation equipment, and an automatic voltage regulator.

Advantages: Simple structure and fast response speed.

Disadvantages: Complex changes in the system voltage during strong excitation.

As a professional diesel generator manufacturer, we always insist on using first-class talents to build a first-class enterprise, create first-class products, create first-class services, and strive to build a first-class domestic enterprise. If you would like to get more information welcome to contact us via [email protected].