EFFECTS OF VARIABLE VOLTAGE AND FREQUENCY ON THE PERFORMANCE OF POLYPHASE INDUCTION MOTOR.

The steady state performance of a three Phase wound rotor Induction Motor with different supply voltages and frequencies is described: A considerable improvement in the efficiency of the Induction Motor is obtained with a higher supply voltage than normal but the power factor is decreased. With a lower voltage than normal, the efficiency as well as the power factor of the induction motor are decreased. The speed regulation with lower applied voltage is quite large compared to normal supply voltage, on the other hand with a higher supply voltage the speed regulation shows improvement. With a rated supply voltage and lower supply frequency, the efficiency as well as the power factor of the induction motor are improved but the speed has correspondingly decreased. When the induction motor is supplied from a source with a higher frequency, the efficiency as well as the power factor are decreased but the speed is increased.