Cogging torque reduction of axial magnetic gearbox using pole pairing technique

Abstract

Magnetic gearbox (MGB) becomes an attractive research topic in mechanical transmission as it offers significant advantages over mechanical gears such as contactless power transfer, high gear ratios, inherent overload protection, high torque density, and maintenance free. However, the main design problem of magnetic systems is the cogging torque originated from high strength permanent magnets (PM), which causes additional vibrations and acoustic noise. Therefore, cogging torque mitigation is a crucial problem in MGB design. This paper introduces a new technique for torque ripple reduction in axial MGB using the pole pairing technique, which is usually applied for torque ripple mitigation in conventional PM machines. A conventional 16/4 axial MGB, which normally results in a significant cogging torque magnitude, is designed and the pole pairing technique is applied to both high and low speed rotors in opposite manner. The 3D finite-element analysis (FEA) confirms the effectiveness of this method and the optimum pairing angles are determined for optimum torque profiles for both high and low speed rotors.