Reduction in Flux Loss of an Nd-Fe-B Bonded Ring Magnet for an SPM Motor

Abstract

We have previously proposed a simulation method of an initial flux loss in permanent magnets using finite element method, and confirmed that predicted flux loss of a Nd-Fe-B boned ring magnet showed good agreement with measured flux loss. In this study, we applied our proposed method to a Nd-Fe-B boned ring magnet in a SPM motor. We modeled a rotor composed of a Nd-Fe-B bonded ring magnet and a soft magnetic core made from silicon steels, and carried out the simulations for magnetizing process and prediction process of the flux loss. From the simulation results, we found that the inner side of the ring magnet has large flux loss. In order to reduce in the flux loss, we enhanced the coercivity in the inner side of the ring magnet by partial replacement with another bonded magnet with high coercivity. Consequently, we found that the ring magnet with locally enhanced coercivity is effective to reduce in the flux loss.