Digital Simulation of PWM Induction Motor Drives for Transient and Steady-State Performance

In this paper, the influence of nonsinusoidal voltage excitation applied to a squirrel cage induction motor is investigated using direct three-phase machine simulation method. Computer packages are developed to generate various types of inverter modulation techniques, namely the sine, step, and current impressed schemes. These packages together with a three-dimensional plotting subroutine are used to investigate the characteristics of an inverter-fed induction motor system. The effects of switching frequency ratio, overmodulation, and start-on machine waveform characteristics are investigated. Harmonic distortion comparisons between sine and step modulation schemes are presented. A vector controller-driven current-impressed scheme are simulated. The effect of varying hysteresis band in a current-impressed scheme is discussed.