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

• Published in: IEEE transactions on industry applications 2017-07, Vol.53 (4), p.3485-3495
• Main Authors: Du, Zhentao S., Lipo, Thomas A.
• Format: Article
• Language: English
• Subjects: 3-D machine design; Cavity resonators; Cogging torque; Design optimization; differential evolution; efficiency; Finite element method; finite-element (FE) modelings; interior permanent-magnet machines (IPMMs); Iron; Motors; Optimization; Permanent magnets; Rare earth elements; ripple torque; Rotors; Segments; Stator windings; Torque; Weight reduction
• ISSN: 0093-9994; 1939-9367
• DOI: 10.1109/TIA.2017.2687879

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.