Dual-stator consequent-pole Vernier PM motor with improved power factor

The Vernier permanent-magnet (VPM) machines are recently attracting more attention for utilisation in low-speed, high-torque applications including renewable energy conversion systems, electric vehicles and elevators. Although, the VPM machines present interesting advantages, they suffer from lower power factor (PF) in comparison to the conventional permanent-magnet (PM) drives. In this study, a novel structure of the VPM machine with dual-stator and consequent-pole (CP) rotor topology is proposed with enhanced PF. The objectives in this new structure are achieving higher torque density per PM volume, higher efficiency, simpler and more robust installation of PM pieces, lower cogging torque and simpler rotor core laminations compared to the previously proposed VPM structures with reasonably improved PF. The low PF issue of VPM machines is analysed in details and the novel CP-VPM geometry is designed to diminish this drawback. Then analytical relations are derived based on the magnetic-equivalent-circuit for evaluating the flux density distribution, induced back electromotive force, magnetising reactance and PF. The effectiveness of the novel structure in enhancing the operating features is validated using analytical and 2D-FE simulation results. Finally, it is concluded that the performance of the optimally designed structure can be enhanced reasonably so that to consider it as a good choice for direct-drive applications.