Analysis, design and experimental verification of a coaxial magnetic gear using stationary permanent‐magnet ring

This study presents the analysis and experimental verification of a coaxial magnetic gear (CMG) for speed‐change transmission. The key design of this CMG is to adopt a stationary permanent‐magnet (PM) ring between the inner and outer rotors, aiming at removing the PMs and only retaining the salient‐pole‐iron on the outer rotor to improve its mechanical reliability. Meanwhile, due to a large equivalent magnetic clearance promoting low torque ripples, the proposed CMG can offer the advantages of achieving a consistent speed ratio and stable transmission within the entire pull‐out torque range. By using the two‐dimensional finite element method, the detailed parametric analysis and static characteristics of the proposed CMG are performed to set up its design criteria. Moreover, a quantitative comparison with a conventional CMG is conducted, and a prototype is also fabricated for experimentation to verify the validity of the proposed CMG.