03-12-2012, 05:42 PM
TYPES OF DC GENERATORS
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Types of D.C. Generators
The magnetic field in a d.c. generator is normally produced by electromagnets rather than permanent magnets. Generators are generally classified according to their methods of field excitation. On this basis, d.c. generators are divided into the following two classes:(i) Separately excited d.c. generators(ii) Self-excited d.c. generators
Separately Excited D.C. Generators
A d.c. generator whose field magnet winding is supplied from an independent external d.c. source (e.g., a battery etc.) is called a separately excited generator
SELF EXCITED DC GENERATOR
A d.c. generator whose field magnet winding is supplied current from the output of the generator itself is called a self-excited generator. There are three types of self-excited generators depending upon the manner in which the field winding is connected to the armature, namely;(i) Series generator;(ii) Shunt generator;(iii) Compound generator
COMPOUND GENERATOR
In a compound-wound generator, there are two sets of field windings on each pole—one is in series and the other in parallel with the armature. A compound wound generator may be:(a) Short Shunt in which only shunt field winding is in parallel with the armature winding [See Fig. 1.35 (i)].(b) Long Shunt in which shunt field winding is in parallel with both series field and armature winding [See Fig. 1.35 (ii)].