AC Generator

What Is an AC Generator ?

The machine that transforms mechanical energy into electrical energy is known as an Electrical generator. The generator is usually classified into type based on the supply of power, namely AC and DC. For the DC generator, the supply to the machine is single directional, and the vice versa is applicable for the AC generator. With this difference in input supply, the internal operation differs for the generators.


AC Generator, its construction, how EMF is induced, its parts and applications, and more will be discussed here in this article. Slip rings are used in AC for the generation of the alternating current in the machine. The generated voltage or current is initially alternating one in both the kinds of the generator. 

AC Generator Definition

The machine which converts the mechanical energy into electrical energy in the output of alternating current or voltage is known as AC Generator. The machine works on Faraday's law of Electromagnetic induction. Here, the Direct Current voltage is made to rotate inside the fixed coil, like a huge power generator that produces the AC current.

By using Fleming's right-hand rule, the direction of the alternating current in the generator is determined. The below diagram shows the four-pole single-phase generator:

Circuit Diagram AC Generator

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What are the Parts of an AC Generator?

Here is the list of the parts of the AC generator, which mainly consists of the yoke, permanent magnets, coils or loop wound with wires, pole core, armature core, pole shoe, slip rings, and brushes. The frame acting as the protecting cover of the generator is known as a yoke. All the components mentioned above are within the yoke. The magnets generate the magnetic field between the air gaps. The coil made up of four-wire AB, BC, CD, and DC is placed inside the magnetic field. The schematic diagram of the AC generator is shown below with all the labels for your understanding.

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The pole shoe is within the pole core to house the windings—the armature windings placed in the armature core. The armature flux results in the production of the armature core. The operation is conducted smoothly, with the use of slip rings. The rings are attached to the brush through which the current passes. As the slip rings pass smoothly through the brushes, it avoids the twisting of the wires.

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Working of AC Generator – The principle of Faraday's law of electromagnetic induction is followed for the working of the AC generator.

An EMF is induced whenever a conductor cuts the lines of magnetic flux, which causes the current to pass through the conductors. For a better insight into the mechanism of an AC Generator, let's consider a simple loop generator which is placed under the influence of a magnetic field. 

Name the loop placed in the magnetic field named ABCD; as mentioned earlier, the loop of wire is named as AB, BC, CD, and DC. With the help of an external shaft which acts as the primary mover, the loop is rotated. In the below diagram, it shows the working of the AC generator.

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The magnetic flux lines will move from left to right and from north pole to south pole. With the help of the shaft, the loop is rotated as it cuts the magnetic flux. This develops the EMF, which causes the current to flow through the conductors. With the help of Fleming's right-hand rule in generators, the direction of the current is determined. 

As per Fleming's right-hand rule, the middle-finger, forefinger and thumb are positioned perpendicular to each other, which is shown in the figure below. 

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As per the diagram below, the loop rotates; rule determines the direction of the current inside the wire AB. For a half cycle, the current flows inside the wire AB. With the rotation of the loop, the current inside the wire AB reverses for the other cycle. The same procedure is performed for the other wires, i.e., in BC, CD, and DC, as the loop rotates the direction of the current changes for every half cycle. The figure shown below considers the above two cases for the working of the AC generator.

The slip rings are attached to the loop end and are responsible for the movement of the wires when the loop is rotated. The current passes through the slip ring to the brushes and then to load as it passes smoothly the slip rings through the brushes.

For every half-cycle of the loop, the direction of the current gets changed. By using a galvanometer, we can observe the alternating current at the load end. This is how the Alternating Current Generator generates an alternating voltage or current.

The Bottom Line!

From the above article, we had an overview of the Alternating Current Generator. The device converts the mechanical energy into electrical energy and gives an output of alternating current or voltage. Apart from that, the above article gives you insight into the working parts, uses, and its application in daily life.

FAQ (Frequently Asked Questions)

1. What is the Principle of the AC Generator?

Ans: On the principle of Faraday's law of electromagnetic induction, the AC generator works.

The diagram above shows the simple working of an AC generator. As shown in the figure, as the coil rotates, it experiences a change in the magnetic flux. According to Faraday's law of electromagnetic induction, the electrons are moved by the EMF induced in the coil which causes the generation of an electric current. The circuit is closed through the load (lamp), where the current generated is alternating in nature as the flux is alternating in nature.

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As shown in the figure, the rotating coil is known as rotor, and field poles as stator.

But in practice, AC generators or alternators are constructed in such a way that the rotating part (rotor) is a magnetic field. In contrast, the coil is stationary (stator) of the machine. 

2. What are the Uses of the AC Generator?

Ans: The Uses of AC Generators are a Pervasive Component in Many Applications Such as,

  • In automobiles, where they are known as alternators

  • power generation from windmills

  • power generation from hydro-electric dams

AC Generators have Many Significant Advantages over DC Generators:

  • The design is simple.

  • The maintenance cost is low.

  • Losses are less

  • The size of the equipment is compatible.

  • AC generators are cheaper to manufacture

  • It is easy to step up and step down the power generated by the AC generator with the help of the transformers

These are the explanations that AC generators are the leading technology in most applications.