Reducing cogging torque and suppressing torque ripple in PMASynRM for EV/HEV applications

For permanent magnet assisted synchronous reluctance motor (PMASynRM), cogging torque and torque ripple are also not ignored. A novel method is proposed in this paper to reduce cogging torque and suppress torque ripple, that is, stator teeth notching skewing. The discrete expression of cogging torque is derived with the energy method and the Fourier series analysis. The rough skewing angle is set to be a slot pitch. The numerical calculations show that cogging torque is greatly reduced and torque ripple is effectively suppressed. Segmentation of stator is proposed to make this method used in any length stack. Further, teeth notching width and depth are optimized; the effect of teeth notching number are researched; compromise of skewing angle and segmentation number, and combination of notching skewing direction are also researched in detail. Relevant conclusions are drawn by FE calculation.