Comparison of Methods Using Different Sources for Computing PWM Effects on Permanent Magnet Machines Considering Eddy Current Reaction

Abstract

This article compares two methods for computing high-frequency harmonic currents (HFHCs) and losses in permanent magnet synchronous machines (PMSMs) driven by pulsewidth modulation (PWM) voltage-source inverters (VSIs). The first method uses the currents containing HFHCs, which are obtained from the SIMULINK-based inverter-motor simulation system, as input for time-stepping finite-element analysis (TSFEA) to compute the PWM effects, while the second method directly uses PWM voltage sources as input for conducting the coupled field-circuit TSFEA. It is pointed out that the HFHCs are underestimated with the first method due to neglecting the eddy current reaction effect. Hence, both the iron and permanent magnet losses will be underestimated with the first method. On the contrary, the second method is better for computing the PWM effects because high-frequency harmonic voltages are independent on the eddy current reaction effect under PWM VSI supply and are directly related to high-frequency flux density variations, which determine high-frequency losses. Experiment on an interior PMSM was conducted to validate the simulation in this article.