Difference Between AC and DC Generator

Dhristi JEE 2022-24

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 Alternator. 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 the 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 the magnet moves.

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 their efficiency is less.


No commutator is present in the AC Generator.

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

Distribution and Transmission 

One of the major differences between AC and DC generators 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.

Similarities Between AC and DC Generator

Both Alternating current (AC) and Direct current (DC) are produced by causing charge to flow via wires in order to convey electrical energy and power various devices.

A voltage source causes current flows in the circuits in both currents. Converting from one type of currency to another is also conceivable, however switching from AC to DC is typically seen to be easier.

Both have a permanent magnet, either a string horseshoe magnet or an electromagnet.

Both use an armature coil with a soft iron core.

Both depend on the relative motion of a coil between the coil of a wire and the magnetic field utilized in the generation of electricity.

Although the alternating current is generated, the commutator is employed to convert direct current to alternating current in DC Generators.

Induction Generator

An induction generator, also known as an asynchronous generator, has a working principle similar to that of an AC Generator and generates electric power using the principles of induction motors. It is referred to as asynchronous because the induction generator operates at a slower speed than the synchronous generator. The rotor of the generator is positioned within a spinning magnetic field, and the rotor is spun by an external source of mechanical energy such that it rotates faster than the magnetic field. The revolving shaft drags the magnetic field ahead, causing electricity to flow into the generator's coils. The output of the induction generator depends upon the magnitude of the negative slip and the speed of the rotor or how fast the motor drives above the synchronous speed in the same direction. Because they can recover energy with quite simple controls, induction generators are helpful in applications such as mini-hydropower plants, wind turbines, and decreasing high-pressure gas streams to lower pressure.

FAQs on Difference Between AC and DC Generator

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

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?

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.

3. What are the basic usage of AC and DC Generators?

The basic functions of AC and DC Generators differ. This is particularly noticeable in the kind of gadgets they individually power. AC Generators are typically used to power home electrical appliances and lightweight motors such as vacuum cleaners, juicers, and food mixers. DC Generators, on the other hand, are utilized to power larger electric motors such as those used in subway systems. Direct current generators are also utilized to charge off-grid batteries since they provide an efficient and stable energy supply. In an alternating current generator, the coil through which current travels is stationary, but the magnet normally moves. The magnet's south and north poles cause current to flow in different directions, producing an alternating current. The coil of a DC Generator motor, on the other hand, is not stationary; rather, it rotates in a fixed field. The commutator connects the coil's two ends, balancing the charges to and from the generator and resulting in a current that does not change direction.

4. What are the advantages of Induction generators?

  • Because of its sturdy structure, an induction generator requires minimal maintenance. Because it is inexpensive, an ordinary cage motor is utilized as an induction generator.

  • It is relatively less expensive.

  • It has a relatively small size per kW of output power, resulting in a high energy density.

  • It runs in the background without hunting.

  • A self-protection function is included in the induction generator. If a failure develops on the short circuit's terminals, the excitation fails, and the machine shuts off the generator.

  • It does not require synchronization to the supply line like a synchronous generator.

  • It does not need as much auxiliary equipment.

  • Induction generators are extremely durable and do not require the use of a commutator or brush.

  • The primary mover's speed varies less than the other components.

  • Because of the self-regulation effect, the control system complexity in induction generators is minimized.

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