In this study, effect of voltage source inverter (VSI) operation on magnet eddy current (MEC) loss of a permanent magnet synchronous motor (PMSM) is evaluated, and a voltage pulse pattern for MEC loss reduction is proposed. Firstly, it is clarified that MEC loss is mainly caused by the high-frequency (HF) voltage components induced by the VSI, and it is strongly correlated with d-axis flux linkage fluctuation. Secondly, a voltage pulse pattern that comprises a combination of a square wave and rectangular waves is proposed. By inducing interference between the HF voltage components of the waves to mitigate d-axis flux linkage fluctuation, MEC loss is reduced. The effect is experimentally evaluated. Compared with that in pulse width modulation (PWM) operation, the magnet temperature rise is mitigated by 26% and 41% under no-load and load conditions, respectively.
Sasaki et al. (Thu,) studied this question.