No-load operations of induction motors under PWM supply

In the paper the no-load operations of PWM inverter fed induction motors are discussed and analyzed, with particular reference to the core and additional losses in presence of a distorted voltage supply. Starting from a previously developed method to predict the iron losses with PWM supply in magnetic laminations and special induction prototypes, the authors want to introduce the problems concerning the estimation and measurement of the “actual” iron losses in industrial induction motors through the conventional no-load test. Experimental measurements performed on an 11 kW, 230/400V, 50 Hz, 4 poles induction motor and the consequent application of the proposed method are reported in detail, allowing a critical discussion of the no-load test under PWM voltage supply.