Quantitative Comparison between SPM Machine and Consequent Pole PM Machines with Different Rotor Topologies

This paper presents a CP spoke type PM structure with optimal pole arc to improve the output torque without deteriorating the torque performance of the machine. Compared with the CP surface-mounted PM (CP SPM) machine, the flux-enhancement capability of CP spoke type PM structure for improving the maximum torque is analytically derived and conformed by finite-element analysis (FEA). Furthermore, the unipolar end leakage flux of machine with CP spoke type PM structure can be eliminated effectively. For the machine with traditional SPM, CP SPM, CP V type interior PM (IPM) and CP spoke type PM, the electromagnetic performance, including air-gap flux density, open-circuit flux density distribution, torque characteristics, unipolar end leakage flux, loss and efficiency are compared. It is demonstrated that the average torque of machine with CP spoke type PMs can be improved by 13.87%, whilst the torque ripple decrease by 5.3% compared with the CP SPM machine. Furthermore, the unipolar end leakage flux due to the saturation in the iron core of rotor can be eliminated effectively. Finally, the machine with CP SPM rotor is prototyped and measured to validate the analyses.