Improvement of torque performances in consequent-pole PM machines with optimized six-layer winding and Halbach PMs array

Abstract

This paper presents a torque performance improvement method for three-phase consequent-pole permanent magnet (PM) (CPM) machines. The key of this method is to consider torque ripple and output torque simultaneously in CPM machines. This method is realized by adopting optimized six-layer winding and Halbach PMs array. The optimized six-layer winding is employed to reduce the torque ripple by suppressing the even-order harmonics in phase back electromotive forces (back-EMFs). The principles of both even-order harmonics in phase back-EMFs and torque ripple suppression by the optimized six-layer winding are illustrated. There will be a slight reduction of main harmonic back-EMF due to multilayer winding, then resulting in slightly lower torque production. Hence, the Halbach PMs array are adopted to compensate the output torque. Therefore, the proposed CPM machine has similar output torque with the conventional CPM machine. However, the torque ripple of the proposed CPM is much lower than conventional CPM machine. Meanwhile, the PM utilization ratio can be increased more than 37% compared with the conventional SPM machine. Finally, the theoretical analyses are verified by the finite-element method.