AC Generator: Explain it's Working Principle, Types, Advantages, and Applications

Introduction to AC generator

AC generator is a device which can convert electrical energy into mechanical energy by using the principle called electromagnetic induction. It is the process by which induced current will be created in a coil by the change in the magnetic field which is linked with it, current will be induced in the coil if there is any relative motion between the coil and the magnetic field


AC current can be created by rotating the coil of the wire between the poles of the permanent magnet, the coil is known as the armature and the slip rings are connected to the ends of the armature and they are insulated from the armature and from each other

Brushes which is present will be pressed against the slip rings and it would make it possible to connect an external circuit to the rotating armature

Components of AC generator

  • Field
  • Armature
  • Prime mover
  • Rotor
  • Stator
  • Slip rings



The field consists of conductors within the generator which will receive a voltage from the source and it will produce a magnetic flux

Voltage is produced if the magnetic flux cuts through the armature and it is the output voltage of DC generator


It is the part in which voltage is produced in the AC generator, it has many coils of wire which is capable to carry full load current of the generator

Prime mover

It is the component which can be used to drive the AC generator, it can be any type of rotating machine, such as a steel turbine or a diesel engine


It is the rotating component of the generator, it may be driven by the generator’s prime mover which will be a steam turbine or diesel engine the rotor could be the armature if the output voltage is generated there and it could be the field if the field excitation is applied in there


It is the stationary part of the AC generator, the stator could be the armature if the output voltage is generated there and it could be the field if the field excitation is applied there

Slip rings

These are the electrical connections which can be used to transfer power to and from the rotor of an AC generator. It has a circular conducting material which is connected to the rotor windings and insulated from the shaft

Brushes are used to do the electrical connection to the rotor and as the rotor rotates the brushes will ride on the slip rings

Types of AC generator

  • Stationary field rotating armature
  • Rotating field stationary armature

Stationary field rotating armature

Usually, small AC generators have stationary field rotating armature and it has one major disadvantage that is the slip rings and the brush assembly is in series with the load circuits

Rotating field stationary armature

Alternating current will be induced into a stationary coil if a Dc field excitation is connected to the rotor and this arrangement is called the rotating field stationary armature. It is mostly used when high power generation is involved DC source applied to the field coils will produce a magnetic field around the rotating element

When the prime mover turns the rotor then the field will cut the conductors of the stationary armature and an EMF will be created in the armature windings

Advantages of AC Generator

  1. AC generators transfer mechanical energy into electrical energy more efficiently than DC generators.
  2. Transformers transmit AC across great distances with minimal losses.
  3. AC is easily stepped up to high voltages & then stepped down to lower voltages at use.
  4. AC generators are cheaper than DC generators of the identical capacity.
  5. Design and construction are simpler for AC generators than DC ones. They don’t need a complicated, moving commutator.
  6. AC generators are more durable than DC generators due to fewer moving parts.

Disadvantages of AC Generator

  1. Electric shocks and fires can result from sparks and heating concerns in AC generators. Thus, AC generator safety must be improved.
  2. AC generators provide fluctuating voltage. This can harm some electronics.
  3. Transformers are needed to step up (or) step down AC generator voltage for safety and efficiency. This can make AC generators more expensive and complicated.

Difference Between AC and DC Generator

Difference Between AC and DC Generator
AC Generator DC Generator
An AC generator is a device that converts mechanical energy into alternating electrical energy, such as alternating currents and alternating electromagnetic fields. A DC generator is a device that converts mechanical energy into direct electrical energy, such as direct currents and direct electromagnetic fields.
Slip rings have a smooth and unbroken surface, consequently they do not wear quickly & are extremely efficient. A DC generator’s brushes and commutators wear out quickly, leading to reduced efficiency.
The brushes have tremendous efficiency, thus a short circuit is highly improbable. The brushes & commutators wear down quickly, increasing the potential of sparking and short circuits.
AC generators are simple to maintain and highly reliable. DC generators require frequent maintenance & are less dependable.