Demystifying 3 Phase Generator Excitation Systems

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Demystifying 3 Phase Generator Excitation Systems

Table of Contents:

  1. Introduction
  2. What is an Alternator? 2.1 Structure Diagram of an Alternator 2.2 Major Parts of an Alternator
  3. How Does an AC Alternator Work? 3.1 Diagram Explanation 3.2 Electricity Production in an AC Alternator
  4. Types of Prime Movers 4.1 Engines 4.1.1 External Combustion Engines 4.1.2 Internal Combustion Engines 4.2 Turbines
  5. Electric Generators 5.1 Components of an Electric Generator 5.2 Control Panel and Engine
  6. Excitation Systems in Alternators 6.1 Shunt Excitation System 6.1.1 Definition and Working 6.1.2 Advantages and Disadvantages 6.2 Permanent Magnet Generator Excitation System 6.2.1 Definition and Working 6.2.2 Advantages and Disadvantages 6.3 Auxiliary Winding Regulation Excitation System 6.3.1 Definition and Working 6.3.2 Advantages and Disadvantages
  7. Conclusion

Article: Understanding Alternators and Excitation Systems


Welcome to Power Learning! In this article, we will dive into the world of alternators, prime movers, and excitation systems. Alternators play a crucial role in generating electrical energy from mechanical energy, and understanding how they work is essential for anyone involved in the field of electrical engineering. We will explore the structure of an alternator, its major parts, types of prime movers used in conjunction with alternators, and different excitation systems commonly employed. So let's get started!

What is an Alternator?

An alternator is an electricity generator that converts mechanical energy into electrical energy in the form of alternating current (AC). It is a crucial component in power generation systems and can be found in various applications, including power plants, automobiles, and portable generators.

Structure Diagram of an Alternator

To understand the internal workings of an alternator, let's take a look at its structure diagram. The primary components of an alternator include an Automatic Voltage Regulator (AVR), terminal outgoing lines, exciter rectifier, main rotor, stator, flywheel, connection plate, and fan. Familiarizing yourself with these parts is essential for a comprehensive understanding of alternators.

Major Parts of an Alternator

In addition to the components mentioned earlier, there are a few more essential parts that you should be aware of. These include the rectifier plate, also known as the diode plate, and the avr, which stands for automatic voltage aggregator. Understanding these parts and their functions will greatly contribute to your understanding of alternators.

How Does an AC Alternator Work?

Now that we have a basic understanding of an alternator's structure, let's dive into how it actually works. The diagram in this section will help us visualize the process better. In an AC alternator, the main stator generates the primary AC power output, which is then taken through four output lines. The Automatic Voltage Regulator (AVR) senses the load's voltage and generates a corresponding DC output to the exciter stator. The exciter stator produces a DC electromagnet in its coils, and the exciter rotor, with its three-phase winding, provides the supply to the rectifier assembly. The rectifiers convert the AC supply to DC, which is then supplied to the main rotor. The main rotor, acting as an electromagnet with poles, creates a magnetic flux that, when moving inside the main stator, generates electricity.

Types of Prime Movers

Prime movers are mechanical power sources coupled with alternators to provide the necessary rotational energy. There are two main types of prime movers: engines and turbines.

Engines can be further classified into external combustion engines and internal combustion engines. Examples of external combustion engines include steam engines, while internal combustion engines include petrol and diesel engines.

Turbines are another type of prime mover and can be powered by steam, gas, water, or wind. When a prime mover is coupled with an AC alternator, it is referred to as an electric generator.

Electric Generators

An electric generator consists of the alternator and its associated components. These include the control panel, power cables, and the engine. Each component plays a crucial role in ensuring the proper functioning and efficient power generation of the system.

Excitation Systems in Alternators

Excitation systems are responsible for providing the necessary current to the alternator rotor to produce a magnetic field. There are three common excitation methods used in alternators: shunt excitation system, permanent magnet generator excitation system, and auxiliary winding regulation excitation system.

The shunt excitation system is the most basic and widely used method. It relies on an Automatic Voltage Regulator (AVR) to shunt the power supply voltage onto the alternator's output terminals. The AVR regulates the excitation current based on the alternator's output voltage. While simple in design, the shunt system has limitations in terms of high overloads and short circuit capabilities.

The permanent magnet generator excitation system improves upon the shunt system by using a permanent magnet generator (PMG) to generate a constant voltage independent of the alternator winding. This system has a high overload capacity and is particularly suitable for demanding applications.

The auxiliary winding regulation excitation system, also known as the arab citation system, utilizes two separate auxiliary windings to generate the AVR power supply voltage. This voltage is proportional to the alternator output voltage and the current drawn by the alternator. The excitation current delivered by the AVR is independent of any voltage distortion or harmonics caused by the load. This system provides high short circuit capability and is ideal for certain applications.


In conclusion, alternators are essential devices in the field of electrical engineering. Understanding their structure, major parts, and working principles is crucial for professionals in this domain. Additionally, knowledge of the excitation systems used in alternators allows for optimal performance and adaptability in various applications. We hope this article has provided you with a comprehensive understanding of alternators and excitation systems, enabling you to delve deeper into this fascinating field. Remember to like, share, and comment, and stay tuned for more informative content in our upcoming videos.

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