Investigation of High-performance Direct-drive Vernier Motors with Various Permanent Magnet Configurations

Permanent magnet (PM) configuration determines the magnetic loading of the vernier motor, which is quite crucial to motor performance metrics, such as torque, power factor, torque ripple, etc. This paper investigates various PM configurations to identify the optimal one for a 12-slot 16-pole vernier motor with fractional-slot concentrated winding. The analytical model of vernier motor based on motor sizing law is presented, and the impact of PM configuration on performance metrics is explained. A comprehensive comparison between five promising PM configurations, regarding all electromagnetic performance, is conducted to achieve the high-performance design. Discussion on PM parameters and current control angle on various PM configurations is implemented for performance improvement. The analyzed results provide design guidelines for high-performance direct-drive vernier motors. The design with optimal PM configuration achieves continuous torque density of 26 Nm/L and power factor of 0.99. The prototype is manufactured and initial experimental result is obtained.