A Novel Permanent Magnet Vernier Machine with Coding-Shaped Tooth

It is known that permanent magnet vernier machine has multiple flux field harmonics which can produce stable torque. However, some flux field harmonics would create torque that undermines the torque output. Such as the 6slots26poles split-tooth PMVM here, of which modulated flux field outputs torque while fundamental flux field undermines torque output. In this paper, a 26poles PMVM with coding-shaped tooth is proposed. The coding-shaped tooth can introduce permeance harmonics with specific phase and amplitude, thus modulating flux fields that all output torque. Air-gap permeance harmonics of the proposed and the regular split-tooth PMVM are obtained via FEA. Based on MMF-permeance model, flux fields of two machines and their contributions to average torque are investigated, proving that the proposed machine has multiple flux fields that all output torque. By optimizing geometry of coding-shaped tooth, the proposed machine obtains largest average torque and smallest torque ripple simultaneously. Electromagnetic performances of the optimized machines are studied in semi-analytical way and FEA. It is proved that with same overall size, PM usage and copper loss, the proposed machine achieves 30% larger torque density, 86% smaller cogging torque and 62% lower torque ripple than its counterpart. Finally, a 16Nm (rated)prototype is built and tested.