What is AC Generator? | How does AC Generator work?

Power plants use generators and turbines to generate electricity. Turbines convert the available energy into the rotation, and the generator converts the rotational energy into electrical power. Depending on the electrical output power, the generators are divided into two types: DC generator and AC generator. In the previous article, we explained the DC generator. This article describes the parts, working principle, and some other aspects of the  AC generator.

What is an AC Generator?

An AC generator is an electrical machine that converts mechanical energy into alternating current. The mechanical power supplied to the AC generator is provided by the IC engine, steam turbine, or gas turbine.

AC Generator

This generator generates power in the form of alternating current and alternating voltage. The resulting alternating current is used for the fans, AC, fridge, and many other types of machinery. 

AC generator works according to Faraday’s law of electromagnetic induction. According to this law, when a conductor rotates in a magnetic field, the magnetic lines of force intersect.

You may achieve this by rotating a magnetic field with a static conductor or by rotating the conducting coil in a static magnetic field. An ideal procedure is to keep the coil static since this method is easy to produce inductive AC current from the static armature coil than from the turning coil.

The resulting emf varies according to the rotating magnetic field speed, the number of rotations of the armature coil, and the strength of the magnetic field.

Working Principle of AC Generator

The AC generator works according to Faraday’s law of electromagnetic induction.

Working Principle of AC Generator

In this generator, the coil spins in a magnetic field, creating a strong magnetic field. When the coil is moved upward from one side by a magnetic field, an electromotive force produces in one direction.

As the coil rotates continuously, one side of the coil transfers downward, and the other side of the coil moves upward; an electromotive force is induced in the opposite direction.

Fleming’s right-hand rule uses to find the direction of the induced electromotive force. This cycle repeats continuously, and the output electromotive force is of the AC type.

Types of AC Generators

The AC generator has the following types:

  1. Asynchronous Generator
  2. Synchronous Generator

1) Asynchronous Generator

This type of alternating current generator is also referred to as an induction generator. The asynchronous generator has a slip that assists in rotating the rotor. The rotor always tries to reach the stator synchronous speed but fails.

If the synchronous speeds of the rotor and stator match, the relative speed goes to zero, so the rotor has no torque. These types of AC generators are ideal for wind turbines.

2) Synchronous Generator

The rotor of the synchronous generators turns at the synchronous speed. This generator operates on the basis of Faraday’s law of electromagnetic induction. According to Faraday’s law, an electromotive force is produced when the coil turns under a uniform magnetic field.

The synchronous generators are usually used to produce high voltage current in power plants.

Parts of AC Generator

The AC generator contains the following parts:

  1. Stator
  2. Rotor
  3. Cylindrical Pole Rotor
  4. Field
  5. Armature
  6. Prime Mover
  7. Slip Rings

Parts of AC Generator

1) Stator

The stator is a static part of the generator. It uses to hold the armature windings effectively. The main function of the armature winding is to provide power to the load. The load can be any external device that uses the generator’s electrical energy. The stator consists of three main parts:

  1. Armature winding: The armature winding is wound in the slot of the armature core.
  2. Stator Frame: This is the outer frame that holds the armature windings and stator core.
  3. Stator core: It laminates with iron or steel to decrease eddy current losses. The core slots in the inner side control the armature winding.

2) Rotor

It is a spinning component of the generator. It contains field windings. The rotor uses a DC power supply to magnetize the magnetic pole. Both ends of the field winding are connected to slip rings. This combination is attached to a mutual shaft on which the rotor turns. The AC generator rotors have two types:

  1. Salient pole rotor
  2. Cylindrical pole rotor

The silent pole rotors are utilized in medium and low-speed applications.

3) Cylindrical Pole Rotor

The cylindrical pole rotor consists of a durable, wrinkle-free cylinder with a groove on the outer surface. This rotor uses for high-speed applications.

4) Field

It has a coil of conductors that get voltage from the input source and create a magnetic flux. This produced magnetic flux in the magnetic field cuts through the armature and creates a voltage. The produced voltage is the output voltage of the alternating current generator.

6) Armature

The armature is the place where the output voltage is generated. It contains a set of enough coils of wire to transfer the generator’s full load current.

7) Prime Mover

It uses to run the AC generator. The prime mover may either be a motor, steam turbine, petrol engine, or diesel engine.

8) Slip Rings

These rings are utilized to transmit power to and fro from the generator rotor. Slip rings are also designed to carry power from a stationary device to a rotating device.

Read More: Types of DC Generators

Applications of AC Generator

  1. AC generators are used to generate electricity from wind turbines.
  2. They use in hydroelectric power plants to generate electricity.
  3. They use to generate electricity from steam turbines.

FAQ Section

What is an AC generator?

An AC generator is an electrical machine that converts mechanical energy into alternating current. The mechanical power supplied to the AC generator is provided by the IC engine, steam turbine, or gas turbine.

What factors do the generated EMF in an alternator depend upon?

The output EMF of the generator depends on the following factors:

  1. Number of armature coil rotations
  2. The speed of the rotating field
  3. Magnetic field strength

What are the uses of AC generator?

An AC generator is used to power smaller electrical items in your company – such as coffee machines, computers, etc. On the other hand, a DC generator is used to power larger electric motors, even as big as those used in subway systems.

How is AC power generated?

An alternating current is produced by switching the potential between two terminals in a fixed time interval—the frequency. The difference in potential between the positive and negative terminal is expressed in volts.

What are AC generators also called as?

AC generators are also known as alternators and are classified according to their rotor construction.

AC Generator works on which principle?

An AC generator works on the principle of Faraday’s law of electromagnetic induction.

What is the generator principle?

Electric generators work on the principle of electromagnetic induction. A conductor coil (a copper coil tightly wound onto a metal core) is rotated rapidly between the poles of a horseshoe-type magnet. The conductor coil, along with its core, is known as an armature.

What is an induction generator?

An induction generator is also known as an asynchronous generator with a working principle similar to an AC generator.

The only difference between a normal AC generator and an induction generator is that the induction generator is a rotating device. It is known as asynchronous because the speed of the induction generator is less than that of the synchronous generator. They find applications in mixers and grinders.

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