Difference Between AC Generator and DC Generator

Edited by Diffzy | Updated on: October 05, 2022

       

Difference Between AC Generator and DC Generator Difference Between AC Generator and DC Generator

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Introduction

The distinction between AC and DC generators is an issue that is regularly explored in Physics. The fundamental distinctions between AC and DC generators are tabulated in this article. I think that understanding the distinctions between AC and DC generators will be beneficial to the pupils

Before learning about comparison, we first learn about AC and DC generators in depth.

Let's read right now.

AC Generator vs DC Generator

According to experts, An AC generator transfers mechanical energy into electrical energy in the form of alternate emf or alternating current. Also, the principle of "Electromagnetic Induction" governs the operation of an AC generator.

On the other hand, A DC generator is a device that converts mechanical energy into DC electricity (direct current). The principle of energetically induced electromotive force is used in the energy alteration process (Difference Between AC and DC Generator, n.d.).

Difference Between AC Generator and DC Generator in Tabular Form

Table: AC Generator vs DC Generator
Parameters of Comparison
AC Generator
DC Generator
The definition
So, A mechanical device that converts mechanical energy into AC electrical power is known as an AC generator.
Now, A DC generator is a machine that converts mechanical energy into DC electrical power.
The direction of current
Experts say that the electrical current in an AC generator reverses direction regularly.
Also, the electrical current in a DC generator only flows in one direction.
Commutators
Commutators are not used in AC generators.
Commutators are used in DC generators to make the current flow in only one direction.
Rings
Slip-rings are used in AC generators.
Commutators are used in DC generators.
Short-circuit chances
A short circuit is improbable due to the brushes' great efficiency.
Because the brushes and commutators wear down quickly, there is a considerable risk of sparking and short-circuiting.
Rotating parts
An AC generator's rotational portion is a low-current, high-resistivity rotor.
A DC generator's rotating portion is often hefty.
Current Induction
The output current of an AC generator can be induced in either the stator or the rotor.
The output current of a DC generator can only be induced in the rotor.

What is AC Generator?

So basically, A generator is a machine that converts mechanical energy to electrical energy. Generators deployed at various power plants produce the electricity generated there. An electromotive force (emf) or potential difference is created when a coil spins in a magnetic field or moves relative to a magnet.

Principle of Electric Generator

To rotate the coil, mechanical energy is required, which is then turned into electrical energy. The induced emf regulates the flow of induced current through the coil, which is then routed to and used by our homes. Electromagnetic induction is the phenomenon that cause the emf.

Now, the electromagnetic induction principle governs the operation of an electric generator. Electromagnetic induction is the phenomenon of generating an electric current in a circuit by altering the magnetic flux connected to the circuit.

Also, the Magnetic flux is the total number of magnetic field lines that travel through a given area. When a coil is moved in relation to a magnet, the magnetic flux associated with the coil changes, causing emf in the coil.

Electromagnetic induction is governed by two laws developed by Faraday. Their names are as follows:

  • An emf is created when the amount of magnetic flux in a circuit varies. For as long as the magnetic flux fluctuates, the induced emf exists.
  • The rate of change of magnetic flux coupled with the circuit determines the amplitude of induced emf in a circuit.

Now, there are several ways to generate emf in a coil, including:

  • Due to the relative velocity of a coil and a magnet.
  • Also, The relative motion of a coil and a current-carrying wire causes
  • By adjusting the current in a conductor near the coil.

In order to determine the direction of the induced current produced in the coil, apply Fleming's Right-Hand Rule: "Stretch your right hand's thumb, the first finger, and then the center finger perpendicular to each other. The first finger points to the magnetic field, the thumb to conductor velocity, and the middle finger to generated current."

The induced current is generated by spinning the coil of an electric generator in a magnetic field. The induced current results in changes in magnitude and direction thousands of times each second. This type of energy is known as alternating current (AC).

Electric generators produce both alternating current (AC) and direct current (DC) electricity (DC). Based on this, electric generators are classified as AC generators and DC generators.

An AC generator is a mechanism that converts mechanical energy into electrical energy. Steam turbines, gas turbines, and combustion engines provide mechanical energy to the AC Generator. The output is alternating electrical power in the form of alternating voltage and current.

Principle of AC Generator

Now, we know that Faraday's law of electromagnetic induction states that when a current-carrying wire cuts a uniform magnetic field, an electromotive force (EMF or voltage) is formed. This can be accomplished by rotating a conducting coil in a static magnetic field or rotating the magnetic field enclosing the stationary conductor. Because the induced alternating current is easier to extract from a fixed armature coil than from a revolving coil.

Now, the number of armature coil turns, magnetic field intensity, and rotating field speed all influence the EMF generated.

Construction

  • Field- So basically, the field consists of conductor coils that accept electricity from the source and generate magnetic flux. Also, the magnetic flux in the field cuts the armature, resulting in a voltage. This is the output voltage of the AC generator.
  • Armature- Now, the armature is the part of an AC generator that generates voltage. Wire coils large enough to handle the generator's full-load current make up the majority of this component.
  • Prime Mover- The component that drives the AC generator is known as the prime mover. The prime mover could be a diesel engine, a steam turbine, or a motor.
  • Rotor- The rotor is the generator's rotating component. The primary mover of the generator drives the rotor.
  • Stator- Also, the stator of an AC generator is the stationary component. The stator core is made up of a lamination of steel alloys or magnetic iron to prevent eddy current losses.
  • Slip rings- Electrical connectors known as slip rings transmit power from and to the rotor of an AC generator. They're usually utilized to transmit electricity from a stationary to a rotating item.

Working of AC Generator

So now, As the armature rotates between the poles of the magnet on an axis perpendicular to the magnetic field, the flux linkage varies continuously. As a result of this, an electric current pass via the galvanometer, slip rings, and brushes. Then The galvanometer shifts from a positive to a negative reading. After this, the galvanometer is receiving an alternating current.  Next, the direction of the induced current can be determined using Fleming's Right-Hand Rule (AC Generator – Principle, Construction, Working, Applications, 2021).

Advantages of AC generators over DC generators

  • AC generators may be easily stepped up and down using transformers.
  • The transmission link size in AC Generators is less due to the step-up functionality.
  • AC generators have smaller losses than DC generators.
  • The size of an AC generator is significantly smaller than that of a DC generator

What is DC Generator?

Now, A DC generator, also known as a direct current generator, is an electrical machine whose primary purpose is to convert mechanical energy into DC (direct current) electricity. The principle of energetically induced electromotive force is used in the energy alteration process.

Now, based on the Electromagnetic Induction concept of Faraday's Laws, when a conductor slashes magnetic flux, an energetically induced electromotive force is formed in it. When the conductor circuit is not opened, this electromotive force might generate a current flow.

Without changing its structure, a DC generator can be used as a DC motor. As a result, a DC motor, also known as a DC generator, can be referred to as a DC machine. The yoke, poles, and pole shoes, as well as the field winding, an armature core, armature winding, commutator, and brushes, are all included in the generator. The stator and rotor, however, are the two most important components of this device.

Construction

Stator- So basically, the stator is an important component of a DC generator because it provides the magnetic fields that allow the coils to spin. This contains stable magnets with two reverse poles facing each other. hence, these magnets are positioned to fit within the rotor's area.

Rotor- The rotor, which is also known as the armature core, is the second most important component of a DC generator. It is made up of slotted iron laminations that are stacked to form a cylindrical armature core. These laminations are typically supplied to reduce eddy current loss.

Armature windings- The major purpose of the armature core slots is to hold the armature windings. These are wound in a closed circuit and connected in series and parallel to increase the total current produced.

Yoke- The DC generator's external structure is called a Yoke, and it is composed of cast iron or steel. It provides the mechanical power required to convey the magnetic flux generated by the poles.

Poles- These are mostly used to keep field windings in place. These windings are usually coiled on the poles, and the armature windings connect them in series otherwise parallel. Furthermore, the poles will provide a link toward the yoke using the welding method rather than screws.

Pole shoe- The pole shoe's primary function is to disperse the magnetic flux and prevent the field coil from falling.

Commutator- The commutator in a DC generator's principal function is to convert AC to DC. It functions as a reversing switch, and its function in the generator is explained further below.

The emf that is induced within the generator's armature coil is alternating. As a result, the armature coil's current flow can also be alternating current. Once the armature coil passes the magnetic unbiased axis, this current can be reversed through the commutator at the precise moment. As a result, the load achieves a DC or uni-directional current.

The commutator ensures that current from the generator flows in a single direction indefinitely. By moving on the commutator, the brushes will make high-quality electrical connections between the generator and the load.

Brushes- Brushes are used to ensure electrical contacts between the commutator and the external load circuit.

Working of DC Generator

Now, The DC generator's working concept is based on Faraday's electromagnetic induction laws. According to experts, an electromotive force is induced within a conductor when it is positioned in an unstable magnetic field. Also, the magnitude of the induced e.m.f. can be calculated using the generator's electromotive force equation.

Basically, the current that is induced will flow in the lane if the conductor is present with a closed lane. Field coils generate an electromagnetic field, and armature conductors are turned into the field in this generator. As a result, within the armature conductors, an electromagnetically induced electromotive force (e.m.f) will be generated. Fleming's right-hand rule will provide the path of induced current (What is a DC Generator : Construction and Its Working, n.d.).

Main Differences Between AC generator and DC generator In Points

  • An AC generator (alternating current generator) is a device that converts mechanical energy into electrical energy. A DC Generator (Direct Current Generator) is a device that converts mechanical energy into direct current electricity.
  • The current in an AC generator reverses direction. Current flows in one direction in a DC generator.
  • The coil of an AC generator is fixed, whereas the magnets move. The coil of a DC generator rotates in a fixed field.
  • AC generator is devoid of a commutator. DC generator is equipped with a commutator.
  • AC generators generate a lot of voltage. Low voltage is produced by DC generators.
  • AC generators outperform DC generators in terms of dependability. DC generators are not as dependable as AC generators.
  • In AC generators, the initial investment is quite high.  On the other hand, DC generators have a lower initial investment.
  • In AC generators, there are slip rings on them. DC generators don't have any slip rings (AC Generator Vs DC Generator, n.d.).

Conclusion

Thus, by now, it’s quite clear in our minds that AC and DC generators have their advantages and disadvantages as well. It was quite interesting to know their differences in detail.

References

  • AC Generator Vs DC Generator. (n.d.). Retrieved from Ox Science: https://oxscience.com/ac-generator-vs-dc-generator/#:~:text=Difference%20between%20AC%20Generator%20and%20DC%20Generator%20in,has%20a%20commutator.%20%206%20more%20rows%20
  • What is a DC Generator : Construction and Its Working. (n.d.). Retrieved from ELPROCUS: https://www.elprocus.com/what-is-a-dc-generator-construction-working-principle-and-applications/

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