Efficient Utilization of Rare Earth Permanent-Magnet Materials and Torque Ripple Reduction in Interior Permanent-Magnet Machines

Abstract

This paper proposes a new interior permanent-magnet machine (IPMM) design in which the rotor consists of several rotor segments arranged in the axial direction, aiming to improve the utilization of rare earth permanent-magnet (PM) materials and reduce the torque ripple. The proposed design is optimized to feature a ${\text{21}}\%$ reduction of rare earth PM materials and a ${\text{50}}\%$ reduction of ripple torque ratio compared with the Camry 2007 design, which uses the conventional pole-shaping technique to suppress its torque ripple. Although the torque is reduced by ${\text{9}}\%$ , the torque per magnet weight is improved by ${\text{15}}\%$ , indicating the PMs are more efficiently used in the proposed design. The designs are verified by 3-D finite element. Despite the small torque reduction, the efficiency of the proposed design is still about the same as the Camry design.