Performance analysis of an asymmetrical phase-converter-fed induction motor

Of the various types of single-phase-to-three-phase static power converters used to interface a three-phase motor to single-phase supply, one simple type uses an open delta connection of a sinusoidal supply and a pulsewidth modulated (PWM) waveform to feed the motor. This paper presents an analysis of the performance of the three-phase motor when fed from such an asymmetrical supply. The analysis is based on the steady-state approximate-equivalent circuit of the motor, using the method of symmetrical components. The analysis is directed toward prediction of motor phase and line currents, along with the nature of generated torque. The computer-simulated waveforms are presented and compared with results from tests on a laboratory setup.