Difference between Generator and Alternator | Alternator Vs Generator

The alternator and generator are most commonly used for different household and industrial applications. These are electrical devices. The main difference between an alternator and a generator is that the alternator has a smaller size and lower weight than the generator. This article mainly explains the difference between the generator and alternator, which explains how they differ from each other regarding efficiency, output, reliability, design, etc.

What is an Alternator?

An alternator is an electromechanical device used to produce alternating current (AC) electrical power from mechanical energy. The alternators are usually used in various vehicles to charge the battery and supply electrical energy to the electrical system while the engine is operating.


The alternator of your vehicle contains a rotor rotating inside a stator. This rotor is usually connected to the belt, which is further attached to the engine’s crankshaft. There are multiple electromagnets installed in the rotor. The belt takes mechanical power from the engine through the crankshaft and drives the rotor.

Alternators also contain a stator. It is a stationary component. It has a series of wire coils installed in a circular pattern.

When the rotor rotates within the stator, the rotor’s electromagnets also rotate and create a changing magnetic field that generates an AC voltage in the stator coils.

This output AC voltage of the alternator is rectified into DC voltage using diodes. This direct current (DC) is further utilized to charge batteries and power the electrical systems of the vehicle.

Generators generally have less efficiency and reliability than alternators. The alternators are most commonly used in multiple applications, from cars and trucks to power plants and wind turbines.

What is an Electric Generator?

An electric generator is a device that transforms the mechanical energy obtained by an external source into electrical energy as the output.

Electric Generator

The generator works on the electromagnetic induction principle. In the generator, the electric current is induced due to a changing magnetic field in a conductor.

An electrical generator contains an armature (a wire of coil) that alternates in a magnetic field. This magnetic field is usually produced by a set of electromagnets or a stationary magnet.

When the generator coil rotates, the magnetic field passing through it varies, which induces an electric current in the wire. The induced current is collected through slip rings and brushes, which are then used to run electrical devices.

Alternator Vs. Generator

The main difference between the alternator and generator is given below:

A generator is a machine that converts the mechanical energy of the main engine into a direct current or alternating current.An alternator is a machine that converts the mechanical electricity of a main engine into an alternating current.
The output power of the generator is not much stronger than the alternator’s output power.The output power is more than the generator’s output power.
It has the ability to produce either direct current or alternating current.It can only produce AC.
It contains a rotating magnetic field to produce a low-voltage, constant, and high-voltage magnetic field.It contains a spinning magnetic field.
The generator has the ability to charge a fully dead battery.It can’t charge a fully dead battery.
The generator output voltage remains constant.The output voltage of the alternators is variable.
It is less efficient.It is more efficient than the generator.
Generators must be polarized after installation.It doesn’t need polarization.
It has less reliability.It has higher reliability.
It conserves less energy.Alternators conserve more energy because they only use the required amount of energy.
They require polarization after installation.They don’t need to be polarized.
The magnetic field is fixed where the armature winding spins.The magnetic field rotates in the stator of the alternators.
It has a rotating armature.It contains a fixed armature.
It gets the input supply from the rotor.It gets input supply from the stator.
It has a low range of RPM.It has a wide range of RPM.
The generator has large size.The alternator has a small size.
They require a large installation area.They require small installation space.

FAQ Section

Where is the alternator located?

The alternator is located in front of the engine and is driven by the driven belt of the engine. It connects to the engine crankshaft. When the crankshaft rotates, it transfers rotation to the alternator. When the alternator receives power from the crankshaft, it moves magnets on a special surface cable and is wired, known as the conductor.

How do you tell if it's the battery or alternator is bad?

If the car battery is not charging, it means that there is a problem with the battery or the alternator. If your vehicle battery dies immediately after starting the vehicle, it means you have a bad alternator. If the battery is charged, but you can’t start the car, there is a problem with your battery.

How to reduce the eddy current losses??

You can decrease the eddy current losses by laminating the core and insulating it from each other with the help of varnish or paper.

What does an alternator do?

An alternator takes mechanical power from the vehicle engine and converts it into electrical power in the form of AC (alternating current). The alternator uses a rectifier to transform the output alternating current into a direct current. The resulting DC is used to charge the battery of the vehicle.

What are the signs of a bad alternator?

The following are the common signs of a bad alternator:

  1. Burning rubber or Wires smell
  2. Overly or Dim bright Light
  3. Whining or Growling Noises
  4. Dead Battery
  5. Frequent Stalling or Trouble Starting
  6. Malfunctioning or Slow Accessories

What are the losses in a generator?

  • Stator iron loss
  • Windage loss
  • Friction loss
  • Stator copper loss
  • Rotor copper loss
Read More

Leave a Comment