Design of a Novel Dual-PM Vernier Machine for High-Torque Direct-Drive Application

This article presents a novel dual-permanent magnet vernier machine (DPM-VM) with yoke permanent magnets (PMs) and slot PMs for torque enhancement, which is well suited for high-torque direct-drive applications. The key is that the proposed machine is the combination of a flux switching machine (FSM) with alternative flux bridges fully filled with armature windings and stator slot-PM VM (SSPM-VM) with a consequent-pole structure. First, slot PMs and yoke PMs generate a parallel magnetic field, which can be superimposed in the air gap and produce abundant field harmonics. Second, alternative flux bridges offer a valid flux path for low-order field harmonics, which is beneficial for torque improvement. Third, the armature windings make full use of the area of alternative flux barriers, further enhancing the torque performance. In this article, the machine structures and working principles are illustrated first. Also, the torque contributions of main working harmonics are identified and quantified by the Maxwell stress tensor (MST) method to offer a comprehensive understanding of the torque production mechanism. Furthermore, the average torque of the proposed machine is 14.39% higher than that of the existing PM FSM. Finally, the prototype of DPM-VM is fabricated and tested, and the performances of the proposed design are coincided with theoretical analysis and finite element analysis (FEA) results.