Influence of Rotor Eccentricity On Electromagnetic Performance of 2-pole/3-slot PM Motors
Tianran He, Z. Q. Zhu, F. Xu, Yu Wang, Hong Bin, Liming Gong
Abstract
This paper investigates the influence of static and dynamic rotor eccentricities on electromagnetic performance, including air-gap flux density, back electromotive force (EMF), electromagnetic torque, cogging torque, and unbalanced magnetic force (UMF), of a 2-pole/3-slot permanent magnet (PM) motor considering eccentricity ratio, eccentricity angle, and rotor initial angle. Both finite element analyses and experiments show that in a 2-pole/3-slot PM motor, the static rotor eccentricity leads to unbalanced magnitudes and phase angles of fundamental back-EMFs of three phases but does not change the harmonic contents, while the dynamic rotor eccentricity will not cause unbalance in three phase back-EMFs but affects the harmonic contents of back-EMFs and their phase angles, which causes asymmetric positive and negative half-periods and corresponding even harmonics of phase back-EMF waveform. In addition, both static and dynamic rotor eccentricities have negligible influence on the average torque, but result in large torque ripple, cogging torque, and UMF.