Difference Between AC And DC Generators

A commutator is one of the most critical parts of the DC generator. It converts the Alternating Current (AC) voltage to a Direct Current (DC) voltage. The commutator make up of segments of copper. The copper segments separate from each other with mica sheets.
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Wanna know the difference between AC and DC generators? This guide provides an inclusive answer.

At first, we should better have a little understanding of what the electric generators are.

What are electrical generators?

Electrical generators are the machines that produce electricity when the primary source, i.e., the central area grid, fails to do so. Electrical generators are the best options to resort to when you face severe power shortages.

What are the types of electrical generators?

As electrical generators use to provide electricity, so based on the output, they classify into two types:

  • DC Generators
  • AC Generators

What is a DC Generator?

The acronym DC stands for Direct Current. A DC generator is the one that converts mechanical energy into electrical energy. It also works on the principle of electromotive force, which induce (BYJUS, 2017). It states:

“When a conductor rotates through a changing magnetic field, the electromotive force (emf) generate.”

The electromotive force causes the current to flow in a closed circuit.

Generator for alternator

What are the parts of a DC generator?

Below mentioned parts that combine to form a DC generator:

1. Stator:

Two magnets of opposite polarity place two sides to each other to make a stator. These magnets place at a definite distance so that a coil can rotate between them. The function of a stator is to provide an actual magnetic field.

2. Shaft:

The shaft is a mechanical piece of a DC generator. It brings about rotation and produces a rotational force called torque. Which helps transfer mechanical energy through itself. The makeup of mild steel and has the most massive breaking strength.

3. Rotor or Armature core:

A group of small electromagnets arranged around a cylinder to make a rotor. As the name implies, it is a rotating component of the generator. It fits inside the stator. The poles of the rotor adjust to face the bars of the stator.

The magnetic fields of the stator produce the torque around the rotor’s axis. The rotor laminate with iron. The laminations help decrease the loss of current. The rotor is also called an Armature core.

4. Commutator:

A commutator is one of the most critical parts of the DC generator. It converts the Alternating Current (AC) voltage to a Direct Current (DC) voltage. The commutator makes up of segments of copper. The copper segments separate from each other with mica sheets.

The mica sheets help protect the copper segments from attaching. The commutator locates in the shaft of the generator.

5. Carbon brushes:

The carbon brushes fit between the commutators and the external circuit. They ensure the smooth flow of current.

6. Yoke or Outer frame:

The yoke or outer frame provides an external covering to the inside mechanism of the generator. It has two purposes:

  • To hold the magnetic poles in their place.
  • To carry the flux of the magnetic field provided through the bars.

It is either made up of steel (for large size) or cast iron (small size).

7. Armature Windings:

The armature windings close-circuit windings connected either in series or parallel. They provide to increase the total sum of the produced current.

8. Pole shoe:

The pole shoes hold the field windings. The field windings wound on the poles. Also, it prevents the fall of the field coil by spreading the magnetic flux.

To understand the main differences, you will have to study both the AC and a DC generator.

For a detailed account of AC generators’ working, refer to the article entitled: What is an AC generator?

brushless ac generator

Difference between AC and DC Generators:

This guide provides extensive information about the difference between AC and DC generators (Elprocus, 2020).

1. The direction of current:


The AC generator and a DC generator both use electromagnetic induction. Their current direction is different.

As the name implies, an AC generator produces an Alternating Current that changes direction. But in a DC generator, a direct current is created, which flows in one direction.

2. Movement of the coil:

In an AC generator, the current-carrying coil fix. Instead, the magnet moves.

While in a DC generator, the coil rotates in a magnetic field to produce the current.

3. Different purposes:

Although both of them are backup generators, their purpose is different. The AC generator helps in powering smaller electrical items of daily use, e.g., coffee machines etc.

Instead, the DC generator uses to power heavier electrical items, e.g., subway systems.

4. Cost:

The AC generators are cost-effective and easy on the pocket. Also, their maintenance cost is low.

Generally speaking, DC generators have smooth voltage and have a simple design, but they are costly.

5. Commutators:

There’s no need to provide commutators in an AC generator.

While in a DC generator, commutators are a must to ensure one-directional current flow.

6. Rings:

The AC generator provides slip rings.

The DC generators provide split rings (commutators) for uni-directional flow.

7. Carbon brushes:

The carbon brushes do not wear out in AC generators due to slip rings. Hence, the low maintenance cost.

On the other side, Carbon brushes and split rings in DC generators wear out. As a result, they must provide occasional maintenance.

8. Possibility of a short circuit:

The carbon brushes in an AC generator are of high efficiency. Due to this, they have low chances of short circuit.

The carbon brushes and split rings wear out in a DC generator. As a result, they have more possibility of a short circuit.

9. Induction of the current:

In an AC generator, the current is either induced in the rotor or a stator.

In a DC generator, the current is bound to induce in the rotor due to manufacture.

10. Output distribution:

The output distribution of current is comfortable in an AC generator.

The output transmission of current is quite tricky in a DC generator.

11. Divergent types:

AC generators come in 3-phase, single-phase with a rotating field and rotating armature types.

DC generators come in self-excited, excited, and with permanent magnet types.

12. Energy efficiency:

The AC generators lead in efficiency as they incur fewer energy losses. Results in high energy efficiency.

The DC generators prove to be less efficient due to chances of wear-and-tear sparkling. And other small losses like eddy currents and hysteresis.

13. The need for transformers:

As the AC generators produce alternating current, transformers use to distribute the draft.

No transformers need in DC generators to distribute the current.

14. Magnet types:

The AC generator uses Concave shaped magnets to make a dense and concentrated magnetic field (Michael, 2020). The AC generator uses a horseshoe magnet suitable to its manufacturing needs.

brushless ac generator

Can we convert an AC generator to a DC generator? If so, how?

Yes, you can convert an AC generator to a DC generator (Brainly, 2018). There are two ways to do so:

  • The first way is to buy a new ‘rectifier’ and attach it with an AC generator. The rectifier is itself an electrical device. It converts the periodically-changing (alternating) current to a one-directional (direct) current. As a result, the current will flow in only one direction due to the rectifier.

The reversal of the current does by the inverter enclosed inside the rectifier. That’s why the process of converting the AC generator to a DC one is also called rectification. Here rectification stands for straightening up of the sinusoidal (alternating) current.

  • The second way is to make a few changes to the construction of the AC generator. That is:
  1. Replace concave-shaped magnets with horseshoes magnets.
  2. Remove the coil of the AC generator with an armature of the DC generator.
  3. Replace the slip rings of the AC generator with the slip rings.

After these fundamental changes to the AC generator, the AC generator will start working as a DC generator.

What is the difference between a DC motor and a DC generator?

Construction-wise, a DC motor and a DC generator are the same thing (Pule, 2019). So DC generator can adjust to work out as a DC motor without making any changes. It would help if you spun the shaft so that the direct current/voltage produce.

In the order of the easy interchangeability of a DC motor and a DC generator, it calls a DC machine.


That is all you need to know about the difference between AC and DC generators. We hope all your queries answer. In case we have missed something, let us know.

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Hey all, I'm Baymax Yan, working at a generator manufacturer and Having more than 15 years of experience in this field, and I belives that “learn and lives.” The sure thing is that I can often help my work. So I have created the blog to share all my knowledge with you. Hope my sharing helps!

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