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

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 21% reduction of rare earth PM materials and a 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 9%, the torque per magnet weight is improved by 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.