Overmodulation and loss considerations in high-frequency modulated transistorized induction motor drives

摘要

A model for calculating additional induction-motor losses due to harmonics associated with PWM (pulse-width-modulated) voltage-source inverters is presented. A simple and low-cost measurement using small inverter to calculate the coefficients to be used in this loss model is presented for any size of induction motor. Based on measurements of motor losses from 300 Hz to 10 KHz, the proposed model assumes much higher losses at higher voltage harmonics than the conventional models. It is shown that sine-wave modulation at approximately 3.6 kHz modulation frequency results in higher losses than the six-step operation, while there is a loss minimum at overmodulation. It is concluded that the proposed model will be useful for the evaluation of various modulation schemes for high-frequency transistor inverters.