An Electrical Generator is a machine which converts mechanical power into electrical energy power.
It is based on the principle of production of dynamically induced EMF.
Whenever a conductor cuts magnetic flux, dynamically induced EMF is produced in it according to Faraday's Law's of Electromagnetic Induction. This e.m.f. causes a current to flow if the conductor circuit is closed. This is accomplished in an electric generator by means of an armature carrying conductors which works in conjunction with a magnetic field. Electromotive force is induced by the relative motion of the armature conductors and the magnetic field.
Hence, the basic essential parts of an electric generator are :
- A magnetic field
- A conductor or conductors which can so move as to cut the flux.
Basic DC machine is that of commutator type, ie. it is an AC machine furnished with a commutator such that it converts the AC to DC. In this respect we can say that the commutator segments act as mechanical rectifiers.
So as you can see there lies a simple generator with a field, coil and relative motion between them. So from faraday's laws of EMI we can say that the coil(loop) would house an EMF.
Depending upon field type DC generators are classified. These are mainly 2 types 1) separately excited generators 2) self excited generators
In separately excited generators field is excited from a separate voltage source. Whereas in self excited type field is excited with permanent magnets.
Depending on field connection with armature they are further classified as 3 types i) series generators ii)shunt generators iii)compound generators