Modeling the influence of commutation in voltage source inverters on rotor losses of permanent magnet machines

Rotor losses in inverter-fed permanent magnet (PM) machines depend on stator current waveform and consequently on inverter output voltage. These losses can be very harmful due to the vulnerability of magnets to heat. In this study, the rotor losses in high-speed PM machines supplied by voltage-source PWM inverters were analytically correlated with the inverter switching parameters. An analytical model which shows the dependency of the rotor losses on a frequency modulation ratio was derived. The derived model was verified by a 2D transient finite element model.