Loss Minimisation in 3-phase Induction Motors with p.w.m. Inverter Supplies

The paper describes the constraints on the selection of the pulse-width-modulated sinewaves produced by a 3-phase inverter. An example of a 7.5 kW induction-motor drive is used to demonstrate how waveforms can be selected to ensure an almost constant flux density throughout the required frequency range, together with a minimum motor loss. A comparison is made between experimental and theoretical results for the performance of the motor, and also between the performances when fed with sinusoidal and with pulse-width-modulated waveforms.