Optimization of a New Asymmetric-Hybrid-PM Machine With High Torque Density and Low Torque Ripple Considering the Difference of Magnetic Materials

Abstract

In this article, a new asymmetric PM-placed rotor topology is applied to the conventional less-rare-Earth hybrid magnet machine, where such new placement of hybrid magnets can be designed to improve the torque performance effectively. Considering the difference between the two magnetic materials, the optimal placement scheme of NdFeB-PMs and ferrite-PMs in the rotor are determined by theoretical derivation of equivalent magnetic circuit and finite element analysis. Based on the torque component separation analysis using frozen permeability method, the sizes of the two magnets are preliminarily designed to improve the utilization of reluctance torque and to reduce the superposition coupling loss of PM torque. Then, based on the parameter sensitivity analysis, the proposed asymmetric-hybrid-PM machine (AHPM) is further optimized aiming at the multi-objective of torque performance and anti-demagnetization performance. Finally, a prototype motor is fabricated and tested. Both the theoretical analysis and experimental results verify the effectiveness and reasonability of the AHPM and the proposed design method.