Cogging Torque Suppression of Inner Rotor in Coaxial Magnetic Gear with Modulator Slots

In this paper, a coaxial magnetic gear (CMG) structure with modulator slots is proposed for the suppression of the cogging torque of inner rotor. The added modulator slots in CMG can effectively reduce the magnitude of the cogging torque by extending the effective length of the internal air gap, thereby achieving the objectives of low vibration noise and high-efficiency of power transmission. The shape, number, position and size of the modulator slots are optimized by the finite element analysis (FEA), which shows that the proposed scheme only sacrifice 1.3% of the maximum output torque and can effectively suppress the torque ripple of inner rotor under different working conditions. In addition, the efficiency of proposed CMG can be higher than 93% in the whole range of operation.