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Chapter: Electrical machines - DC Generators

Methods of excitation of the field windings

i. Separately-excited generators ii. Self-excited generators: series generators, shunt generators, compound generators

Methods Of Excitation

 

Various methods of excitation of the field windings are

 

 

Separately-excited generators

 

Self-excited generators

series generators, shunt generators, compound generators

 

With self-excited generators, residual magnetism must be present in the machine iron to get the self-excitation process started.

 

The relation between the steady-state generated emfEa and the armature terminal voltageVa isVa=EaIaRa

 



Typical steady-state dc-motor speed-torque characteristics are shown in Figure.1.4, in which it is assumed that the motor terminals are supplied from a constant-voltage source.

 

In a motor the relation between the emf Ea generated in the armature and the armature terminal voltage Va is Va=Ea+IaRa. The application of dc machines lie in the variety of performance characteristics offered by the possibilities of shunt, series, and compound excitation.

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