Influence of various magnetic pole on electromagnetic performance of consequent-pole permanent magnet machine

Abstract

Permanent magnet (PM) machine with consequent pole (CP) rotor can improve the PM utilization ratio. However, one group PMs with the same polarity is replaced by iron core which deteriorating the electromagnetic performance of the machine, including even-order back-EMF harmonics, torque ripple, as well as unipolar leakage flux. Therefore, CP PM machine with various magnetic pole, i.e., equal pole-arc magnetic pole (EMP) and asymmetric magnetic pole (AMP) structure is proposed, with smaller torque ripple can be achieved, without deteriorating the torque ability compared with the conventional CP PM machine. Further, the influence of various CP PM magnetic pole on the end leakage flux is analyzed by three-dimensional (3-D) finite element (FE), which includes leakage flux distributions as well as magnetization of shaft. The electromagnetic characteristics of the machine with EMP and AMP rotor are compared with traditional surface-mounted and CP PM machines by FE analysis. It is demonstrated that EMP and AMP rotor structure can reduce even-order harmonics, torque ripple and end leakage flux for the machines. Finally, one prototype with CP AMP rotor is tested to confirm the theoretical and FE analysis, which includes suppression effect of even back-EMF harmonics, torque characteristics as well as leakage flux at the end shaft.