Influence of pulse width modulation (PWM) on the iron losses of electrical steel

This paper deals with the measurement of the magnetic properties of electrical steel under the influence of pulse width modulation (PWM) in comparison to an ideal sinusoidal waveform. At first the theory and practice of measuring the magnetic properties with the ring core method are described. Next the measurement setup and results are depicted. The results show the well-known fact that a sinusoidal voltage has lower losses than pulse width modulated voltage. The relative additional losses of PWM increase with the fundamental frequency. Furthermore a high PWM frequency shows fewer losses than a low PWM frequency. Finally a voltage created with maximal modulation index and minimal DC voltage leads to a decrease of the losses in comparison to the same effective voltage created by a lower modulation index and higher DC voltage.