Torque Improvement and Cost Reduction of Permanent Magnet Machines With a Dovetailed Consequent-Pole Rotor

Abstract

This paper presents a consequent-pole permanent-magnet (CPM) machine to reduce the volume of permanent magnets (PM) and the cost of retaining sleeve, and meanwhile the average torque and efficiency can be improved due to the reduced airgap reluctance. The proposed configuration uses dovetail consequent-pole to protect quasi-trapezoidal PMs with lower total rotor loss than a conventional surface-mounted PM (SPM) machine due to the half number of PMs and the removed sleeve loss. In addition, the stress and deformation of the rotor are investigated. The electromagnetic performance including back EMF, average torque, torque ripple, loss, efficiency, unbalanced magnetic force, demagnetization withstand capability of the proposed CPM machine is investigated by finite element analyses. It is demonstrated that the output torque of the CPM machine can be enhanced by 3%, while the PM volume is reduced approximately 20% compared to that of the conventional SPM machine. Simultaneously, the CPM machine can have lower total harmonic distortions of phase back EMF, lower torque ripple, higher efficiency, and stronger demagnetization withstand than the SPM machine. Finally, the 12-slot/10-pole CPM machine is prototyped to validate the analyses.