Torque ripple reduction of radial magnetic gearbox using axial pole pairing

Magnetic gearbox (MGB) is a contactless magnet-based transmission system that transmits mechanical power between two shafts. MGBs offer significant advantages over mechanical gears such as contactless power transfer, high gear ratios, inherent overload protection, high torque density, potential for high efficiency, and maintenance free. Cogging torque minimization is a challenging design aspect and stands as one of the parasitic demerits of MGBs. The proper selection of the combination of the number of pole-pairs of both high and low speed rotors can effectively minimize cogging torque magnitude. However, only some fixed gear ratios can be achieved. For any general desired gear ratio, the torque ripple magnitude may be unacceptable. This paper introduces a new technique for torque ripple reduction in MGB using the axial pole pairing technique, which is usually applied for torque ripple mitigation in conventional PM machines. A conventional 14/4 MGB, which normally results in a significant cogging torque magnitude, is designed and simulated using 3D finite-element analysis (FEA) for different pairing angles for both high and low speed rotors. Based on 3D FEA results, the required optimum pairing angle that optimizes torque transmission while minimizes the corresponding cogging torque is determined.