Losses and Parasitic Torques in Electric Motors Subjected to PWM Waveforms

Some aspects of the theoretical performance of an electric motor, supplied by an unfiltered pulsewidth modulated (PWM) inverter are studied. The stator copper losses and the winding insulation lifetime are emphasized. An induction motor system is assumed and the creation of low-frequency parasitic torques are described. Their relative importance are estimated. It is shown that PWM supplies may have a negative impact on the motor performance and lifetime and can make a modification of the motor design more desirable than in the case where a ``simpler'' inverter system is used.