14 Difference between Alternator and Generator

What is Alternator?

An alternator is referred to as the primary source of all electrical energy. An alternator is an electrical generator that is designed to convert mechanical into electrical energy in the form of an alternating current.

An alternator is called a synchronous machine because the alternator always operates at synchronous speed (speed of rotor always matches the supply frequency) in order to get an induced emf of the required frequency.

Image of an alternator

Parts of an alternator

  • Stator frame
  • Stator core
  • Cage windings
  • Cage bars
  • Stator terminals
  • Rings
  • Brushes
  • Rotor

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What is Generator?

The generator is a mechanical device that is designed to produce either AC or DC current by converting mechanical energy. There is a rotor present inside the generator, the rotation of this rotor produces electricity.

The generator features a rectangular rotating coil that rotates around its axis in the magnetic field. Either a permanent magnet or an electromagnet generates the magnetic field. Two slip rings connect the coil’s two ends. The current produced in the coil is collected by the slip ring and transferred to the external load resistance R. The armature, which is constructed of copper, is the rotating coil.

Parts of a generator

  • Fuel system
  • Shaft
  • Armature coil
  • Bearings
  • Commutator
  • Cooling and exhaust system,
  • Battery charger


Alternator Vs Generator

S.No Alternator Generator
1 It is designed to converts mechanical energy into electrical energy It is used to produce mechanical energy into electrical energy
2 Alternator always induces an AC( alternating current) Generator can produce either alternating or direct current
3 Polarization does not need Polarization is required after installation
4 An alternator’s stator contains a revolving magnetic field. The magnetic field is stationary or fixed where the armature winding spins in the case of a generator.
5 In alternator, armature is stationary In generator, armature is rotating
6 Alternators use only the amount of energy required and hence save more energy. Generators utilise all of the energy produced, resulting in less energy conservation.
7 Higher output than generator Lesser output than alternator
8 The brushes in the alternator have long life span The brushes in the generator has very less life span
9 Smaller in size Larger in size
10 Alternator produces voltage only if required Generator always produce voltage
11 It takes input supply from the stator Takes input supply from the rotor
12 It has a wide range of RPM Low range of RPM
13 It can’t charge dead battery Can charge dead battery
14 Very efficient Less efficient

Application of Alternator

  • Helps to keep the electrical components of the vehicle charged
  • Marine applications
  • To transmit radiofrequency signals
  • Electrical power generating plants

Application of Generator

  • Can charge the battery
  • Used for powering machinery or tools on a construction site
  • It can be used as a primary source of electricity that can’t take electricity from transmission lines directly

Some Useful Questions

1. What are losses in a generator?

  • Magnetic loss (iron or core loss)
  • Mechanical loss
  • Copper loss

2. How to reduce eddy current losses?

The methods to reduce eddy current loss are mentioned below:

  • The core’s resistance should be boosted.
  • Eddy currents are confined to the thin sheets due to high resistance between the sheets.