A novel dual-stator vernier permanent magnet machine

In many direct-drive applications such as servo system, wind power generation, etc., it is desirable to use motors having a high torque density at a low rotation speed without reduction gears for the improvement of noises, reliability and maintenance. Albeit that some step motors can satisfy this requirement, the torque ripple of step motors are usually large, which will lead to vibrations and reduce the control accuracy. Vernier permanent magnet (VPM) machines exhibit high torque density and small pulsating torque at low speed due to the “magnetic gearing effect” [1]-[3]. So VPM machines are promising candidates in direct-drive systems. In order to further improve the torque performances of conventional VPM machines, a novel dual-stator VPM machine will be presented and analyzed in this paper.