Simplified Thermal Model of PM Motors in Hybrid Vehicle Applications Taking into Account Eddy Current Loss in Magnets

Permanent Magnet (PM) Motors are popular choices for hybrid electric vehicle (HEV) powertrain applications. The effects of the excessive heat in the magnets can degrade the performance of these machines if not dealt properly. It is therefore critical to develop a complete and representative model of the heat processes in the electric motors. In this paper, a simplified analytical model is developed as a thermal circuit with a network of intercon nected nodes and thermal resistances representing the heat processes within the SPMSM. Both losses induced by sinusoidal and PWM waveform voltage supplies are calculated respectively as heat sources in the thermal circuit. Because temperature-rise inside the magnets caused by eddy current loss can lead to the unpredictable deterioration of the magnets, the circuit takes into consideration the eddy current loss developed in the permanent magnets. The thermal circuit is then solved in MATLAB through a system of linear equations. The results of the analytical model are confirmed through 3-D finite element analysis (FEA) simulation in Ansoft ePhysics soft ware.

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