Improved use of rare Earth permanent magnet materials and reduction of torque pulsation in interior permanent magnet machines

Abstract

This paper proposes an alternative interior permanent magnet machine (IPMM) design in which the rotor consists of stacks varied in the axial direction. The proposed design aims to reduce the amount of permanent magnet (PM) materials in conventional IPMMs. The PM width and the PM pole arc on the rotor surface for each rotor stack are both optimized to provide a resultant PM flux distribution in the air gap that contains fewer harmonics. Not only is the pulsating torque reduced significantly, the PM materials are also minimized since the PM portion making up the spatial PM flux harmonics is effectively removed. The results of the proposed design concept indicate a significant torque pulsation reduction in comparison with the base-line model 2007 Camry motor. Moreover, a trade-off is discovered between the average torque production and the PM utilization in an IPMM. The improvement made in the proposed designs proves that the PM materials can be used efficiently and the torque pulsation can be further minimized in IPMM designs.