ANALYSIS OF AN INDUCTION MOTOR WITH CONVERTER CASCADE IN THE ROTOR CIRCUIT.

A mathematical model of an induction motor in the rotor frame of two of the three phases is used to simulate the behaviour of the motor having a converter cascade in the rotor circuit. Following an analysis of the commutation process of the machine side converter an expression is developed for the variation of current during commutation. A digital computer simulation is developed for the solution of these equations to obtain the performance of the motor. The rotor current waveform has been found to depend on slip frequency. The stator current is essentially sinusoidal superimposed by slip dependent harmonics. The torque developed has pulsations predominantly of six times rotor frequency.