Generators are machines converts mechanical energy into electrical energy.

Sources of mechanical energy could be steam turbines, gas turbines, water turbines, internal combustion engines, wind turbines etc. The output of the generator could be Direct Current or Alternating current

When generators converts mechanical energy to AC electrical energy only is called an Alternator.

Generator Construction:

The basic structure of generator consist of the following parts-

1. Stator- the non moving parts
2. Rotor- the moving parts

Stator

1. Yoke: It is the most external part of generator. The functions of yoke are to-
   • protects from external conditions
   • low reactance path
2. Pole Cores and Pole Shoes: The field magnets consist of pole cores and pole shoes. pole cores are usually made of laminated sheets to prevent eddy current losses. The functions of yoke are to-
   • Create electromagnetic fluxes
   • spread out the flux in the air gap
   • reduce the reluctance of the magnetic path
   • support the field coils.
3. Pole Coils: These are wounded over the poles, if current is passed through the coils, the electromagnetise the poles which produce the necessary flux which are cut by the rotating armature.

Rotor

1. Armature: It is the rotating part of the generator. Armature slots contains armature windings.
2. Armature winding: When the armature rotates, it cuts the flux, thus current is produced in the armature winding. The armature winding is created in loops whose end is connected to the commutator.
3. Commutator: The function of the commutator is to collect current from the armature conductors and convert ac into dc current. commutators contain split ring/slip ring depending on the type of the output DC/AC. Split rings are connected to the commutator that converts the AC induced within the armature(we’ll explain later as to how AC is induced in the armature) to DC as the final output.
4. Prime mover or Shaft: Prime mover rotates the generator shaft constantly to generate electrical energy converting the mechanical rotating force: A prime mover provide mechanical input to a machine. The spinning parts are keyed into the prime mover like the armature center, a commutator etc. which rotates along with the rotating shaft.

Be it AC or DC generators, all generators consist of some common parts. The thing that causes difference in the generation of output in generators are the object commutator is connected to at the output. To produce DC output split rings are used in DC generators, while slip rings are used in AC generators to produce alternating current in the circuit.

Working Principle

The stator of the generator is the main source of magnetic field, the stator houses the magnets and supply magnetic fields produced from the poles. The armature is moved with the help of the shaft. The mechanical energy required to move the shaft can be provided by engines operating on fuels such as diesel, petrol, natural gas, etc. or via turbines like- wind turbine, water turbine, solar-powered turbine, etc. As the armature moves through the static magnetic field, according to Faraday’s law of electromagnetic induction for a static field and a moving coil, electromotive force is induced in the armature coils as the coils cut the magnetic flux lines. The current generated within the armature is an alternating current. The commutator collects the AC and acts as a rectifier to convert AC to DC. There are carbon brushes which make contact between the commutator and the external load circuit. Through the brushes DC reach to the load via the load circuit.

This is how a DC generator works.