What are the losses in an induction motor?

There are two types of losses occur in three phase induction motor

Constant or fixed losses
Variable losses

Constant or fixed losses

Fixed losses are considered to remain constant over normal working range of a induction motor. Fixed losses can be determined by no load test of induction motor.

These losses are further classified as -

Iron or core losses

Mechanical losses
Brush friction losses

Variable losses -

These losses are also called copper losses. These losses occur due to current flowing in stator and rotor windings. As the load changes, the current flowing in rotor and stator windings also change and hence these losses changes. Therefore these losses are called Variable losses.Copper losses are determined by block rotor test of induction motor

FORMULA:-
NO LOAD COPPER LOSS= 3 *I²R
IRON LOSS=NO LOAD WATTS - NO LOAD COPPER LOSS
FULL LOAD COPPER LOSS=3*I(full load)²R
TOTAL LOSSES OF STATOR=IRON LOSS-FULL LOAD COPPER LOSS

Ex. 5 hp induction motor power losses at 95 °C winding temperature

Related link

what-is-no-load-current-of-induction-motor-?

Milan Tomic

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