Losses in VSI-PWM fed axial flux machines

The goal of this paper is to study the additional loss caused by Pulse Width Modulation (PWM), on the one hand in an axial flux permanent magnet synchronous machine (PMSM), and on the other hand in the voltage source inverter (VSI) that supplies the machine. Via a computationally efficient technique, the losses are computed in the stator iron and in the magnets of the axial flux PMSM with PWM supply. In addition, the switching losses of the converter are estimated as a function of the PWM frequency. The losses are evaluated in both the machine and the power electronic converter for several PWM frequencies, for several stator currents and for different magnet segmentations. It is observed that with unsegmented magnets, a high PWM frequency results in much lower total losses of the drive than a low PWM frequency. With segmented magnets, the influence of the PWM frequency on the losses of the drive is much smaller. Only in overload conditions, at twice the rated stator current, the lowest considered PWM frequency results in the lowest losses.