Iron loss under practical working conditions of a PWM powered induction motor

A study of additional loss in an induction motor supplied by a PWM inverter is presented in this paper. The magnetic material used in the motor is characterized, thanks to a suitable Epstein measurement equipment, under several excitation conditions: sine and ideal PWM waveforms similar to the voltage delivered by the inverter and practical working conditions of the material, measured in the different parts of the machine stator. Compared to sine, PWM signals induce much higher loss. Moreover, the distortion of the flux increases the additional loss. Those results are used to estimate the loss in the stator of the machine. By considering the real working conditions of the magnetic material, the discrepancy between the estimated value and experiment is less than 25% for the motor studied, whereas it can reach 120% in the case of a conventional prediction with a sinusoidal waveform.