Electrical Engineering ⇒ Topic : Losses in DC Generator
The various losses occurring in a generator are given below:
(i) Copper loss
(a). Armature copper loss = I2aRa where Ra is resistance of the armature and Ia is the armature current.
(b). For shunt generator, field copper loss is equal to I2sh Rsh where Rsh is the resistance of the shunt field winding and Ish is the current through shunt field winding. The loss for shunt generator is practically constant. For series generator, it is equal to I2seRse where Rse is the resistance of the series field winding and Ise is the current through it. This loss is about 20% to 30% of full losses.
(c). The loss due to brush contact is generally included in armature copper loss.
(ii) Magnetic losses or iron losses or core losses
(a). Hysteresis loss ∝ Bnmax f (n is generally 1.6)
(b). Eddy current loss ∝ Bmaxf2
Iron losses are constant for shunt and compound generators as their field currents are approximately constant. This loss is about 20% to 30% of full-load loss.
(iii) Mechanical losses
(a). Air friction or windage loss of rotating armature.
(b). Friction loss at bearings and commutator.
These are about 10% to 20% of full-load losses. Mechanical losses together are known as stray
LOSSES IN A D.C. GENERATOR
Losses in D.C. generators are below :-
(a) Hysteresis loss
(b) Eddy current loss
Mechanical losses :-
(a) Friction loss
(b) Air friction loss
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