Electromagnetic Modeling and Verification of Permanent Magnet Toroidal Motor With Planet Eccentricity

Permanent magnet toroidal motor (PMTM) has the advantages of compact structure, large reduction ratio and high torque density. However, PMTM with more rotating parts is prone to eccentricity issues. Initially, the eccentric form in planets is found during the prototype operation experiment. Combining with the working principle of toroidal motor, the mechanism of planet eccentricity is investigated. Secondly, based on the spatial structure of PMTM, the transformation relationship between spatial magnetic field and component magnetic fields is obtained. Adopting boundary subdomain method, the analytical model of radial magnetic field component is established. The variation function of air gap is introduced to the analytical model to obtain eccentric magnetic field. According to the spiral characteristics of spatial windings, the analytical model of No-load back electromotive force (EMF) of PMTM with planet eccentricity is developed. And the influence of planet eccentricity on the No-load back EMF is discussed. Finally, an experimental platform is built to verify the validity of the proposed eccentricity modeling. The experimental results are in good agreement with the analytical results. The research provides important support for further eccentric electromagnetic characteristics of PMTM.