PWM INVERTER-FED INDUCTION-MOTORS LOSSES EVALUATION

In this paper the authors deal with the problems concerning the steady state losses evaluation in medium power industrial induction motors s upplied by PWM inverter. They present a method based on the no-load an d short circuit tests. This technique seems to be very useful for the good obtained results and because it is quite similar to the standard no-load and short circuit tests used with sinusoidal voltage supply. T he method is based on some simple hypothesis that have been verified d uring the experimental tests by means of mathematical models. As a con sequence, it is possible to compare the no-load and the short circuit tests under sinusoidal and PWM inverter supply considering the same rm s fundamental voltage. The method has been applied to a 7.5 kW inducti on motor supplied by a prototype PWM Voltage Source Inverter (VSI) mod ulated with a ramp comparison technique at a 1 kHz switching frequency . The obtained results could be utilized in order to define some desig n criteria and the derating for standard induction motors supplied by PWM inverters.