July 6, 2012

Compare the induction motor with a transformer.

Comparison of induction motor with a transformer:
Figure: Sketch showing similarity between transformer and induction motor

The transfer of energy from stator to the rotor of an induction motor takes place entirely inductively with the help of flux mutually linking the two. Hence an induction motor is essentially a transformer with stator forming the primary and rotor forming the rotating secondary.

Induction Motor
(1) Secondary is stationary 
(1) Secondary winding is rotating
(2) Secondary is not short circuited
(2) Secondary is always short circuited
(3) No-load current is about 1% of full load 
(3) No-load current is approximately 30 to 50% current (due to low reluctance path   of full current (due to high reluctance of steel core)  of air gap)
(4) emf induced in secondary depends on   K (turns ratio)
(4) Depends on K and slip also
(5) Frequency of primary and secondary currents  are same
(5) Frequency of stator current (f) and rotor current (sf) are not the same.


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