Impact of Magnet Temperature Distribution on Output Capability of PMSM and its Estimation Methodology

Abstract

This paper discusses impact of magnet temperature distribution on shaft direction on PMSM output capability and a concept to estimate magnet temperature distribution regarding a radial airgap type PMSM to maximize magnet utilization while avoiding thermal demagnetization. A 100kW class traction application PMSM is designed and its output capability degradation depending on acceptable maximum magnet temperature is calculated. A concept to obtain maximum magnet temperature on shaft direction is introduced as well. This concept utilizes a step-skewed rotor structure, and estimates average temperature of each skewed rotor core by using magnet temperature dependence of total flux linkage. By assuming magnet temperature linearly varies on shaft direction, its distribution is calculated by linear extrapolation. Total flux linkages under several skewed rotor core temperature combinations are calculated by 3D finite element analysis (FEA). The result shows total flux linkage under specific core temperature combination has unique value. So, it is confirmed the temperature of each core can be estimated independently.