Difference Between AC and DC Generator

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Basic Differences Between AC Generator and DC Generator

The difference between the AC generator and DC generator is one of the crucial topics studied by students during their board studies. The essential difference between AC and DC generators in a clear and precise way is provided in this article. The points of differences discussed can help students to understand the concept more effectively. 

What Does an AC Generator Mean?

An electric generator that converts the mechanical form of energy into electrical energy refers to an AC Generator or Alternators. The electrical energy produced is in the form of an alternating current sinusoidal waveform. The working of an AC Generator is based upon Faraday’s principle of Electromagnetic Induction. One of the basic differences between the AC generator and the DC generator is the components present. An AC Generator includes components:

  • Armature

  • Field

  • Slip Rings

  • Prime Rover

  • Rotor

  • Stator 

Some of the advantages and disadvantages of AC Generator include:


  • It’s effortless to step up and step down AC Generators with the use of transformers.

  • Due to the step-up feature, the transmission link size may get thinner.

  • As compared to the DC machine, there are a smaller number of losses in AC Generator.

  • Size is the main difference between AC and DC generators. AC Generators are comparatively smaller than DC motors. 


  • The production of AC power on a large scale using AC Generators can be unsafe.

  • Resistive heat is produced when electricity flows from AC Generator to transformer coils, which can damage the insulation.

What Does A DC Machine Mean?

An electrical machine that converts mechanical energy into direct current electricity refers to the DC Generator. According to the Faraday Law, an emf is induced when a conductor experiences changing magnetic flux then an emf is produced. The emf generated can cause a flow of current when the conductor circuit gets closed. As mentioned earlier, the difference between an alternator and DC generator lies in the presence of components. The essential parts of a DC Generator include:

  • Stator

  • Yoke 

  • Armature Windings

  • Commutator 

  • Rotor

  • Pole

  • Pole Shoe

  • Brushes 

Some advantages and disadvantages of DC Generator include as follows:


  • DC Generators are widely used for different purposes. For instance, it is used for lighting and power, arc lamps, to provide a power supply, and more. 


  • The input power in a DC motor is not transformed completely into the output power. Due to this reason, there is a loss in some parts of input power in different forms.

  • Due to the resistance in the winding, the current starts flowing in the winding. It results in a copper loss.

Differentiate Between AC and DC generator

AC Generators generally produce a high voltage that varies in time as well as amplitude. However, a DC machine generates a low voltage that is continuous in amplitude plus time. It is one of the main differences between DC motors and AC generators.

Other Points of Differences Include: 

Points of Difference

AC Generator

DC Generator


The construction of an AC Generator is simple. In this, the coil is fixed through which the current passes and magnet move.

The construction of the DC Generator is complex due to the presence of slip rings and commutators. The coil rotates in a fixed field through which the current passes.

Current flow

The electric current flows in the opposite direction periodically.

The current flows only in one way. 

Efficiency of Brushes

Slip-rings have an even and continuous surface. Thus, these are difficult to get wear and thus highly efficient. 

Both commutators, as well as brushes, wear out rapidly due to which it’s efficiency is less.


No commutator is present in AC Generator.

To make the current flow in one direction only, DC Generator comprises the commutator.

Rotating Parts

The rotor is the rotating part that possesses low current and high resistivity.

The rotating part is heavy in DC Generator.

Distribution and Transmission 

One of the major differences between AC and DC Generator is the distribution of output. 

It’s easy to distribute an output from an AC Generator through a transformer.

Transformers cannot be used. Hence, it’s difficult to distribute an output.


AC Generators are highly reliable and require less maintenance.

DC Generators are less reliable and hence require high maintenance. 


The starting cost of an AC Generator is high.

It’s less expensive. 

Apart from the difference between AC generators and DC motors, there are some similarities between them. Both AC and DC Generators work on the relative motion of the coil and the magnetic field used to generate electricity.

FAQ (Frequently Asked Questions)

1. What is the Output of the AC and DC Generators?

Ans: Both AC and DC generators produce electric current with the help of electromagnetic induction. The basic concept behind the production of electricity is the conversion of mechanical energy into electrical energy. When an electric current is passing from the fluctuating magnetic field, the electrical energy is produced. However, the working of both AC and DC generators is entirely different to produce the same result. However, the only similarity is these two generators work on the relative motion of the coil.

2. How can you Change an AC Generator to DC Generator?

Ans: We need a split ring commutator if you want to convert an AC generator to DC. Whenever an alternate cycle will occur, this split ring commutator will change the direction of the current. This means after half rotation occurs, the direction of current reverses. Hence the AC generator gets converted into a DC generator. Thus, the current starts remaining in the positive half cycle. This way the AC generator starts behaving as a DC generator. Or, you can also remove the coil and add armature instead.