TRANSIENTS IN POLYPHASE INDUCTION MOTORS

Abstract

A comprehensive review of transient currents and transient torques during switching operations in the case of single cage and double cage induction motors has been done. The transient currents actually obtained in a 5 H.P. squirrel cage motor during starting, reclosing and plugging, at various values of the applied voltages are compared with computed values using Lyon r s analysis with unsaturated values of motor parameters. Further, it is shown that in all cases, saturation corresponding to rated applied voltage of machine may cause a reduction of about 15.2° in the peak stator current oxpo Qted with the same applied voltage in the absence of saturation. A circuit for closing the circuit breaker at the instant of the voltage cycle when the voltage applied to one of the phases is zero and increasing in the positive direction is also given. The transient torques during various switching operations have also been computed from the motor parameters. The results of the different analysis of the transient torques during starting operations have been compared.