Modeling of permanent magnets temperature of traction motors in HEV

The temperature-rise inside the magnets of interior permanent magnet synchronous motors (IPMSM) in hybrid electric vehicles (HEV) caused by losses can lead to potential irreversible demagnetization. Two different analytical models of temperature prediction were developed. Based on the relationship of the temperature and the magnets performance, the temperature of magnets was predicted through solving the function of voltage, current, rotate speed and winding temperature in the first model. The other analytical model was developed as thermal circuits with network of interconnected nodes, thermal resistances and heat sources representing the heat processes within the IPMSM, to describe the temperature of the magnets. In addition, calculation accuracy was improved due to considering eddy current loss in the magnets. The predicted temperature of two models was validated by experiments as the motors operated by three phase sine supply. When the motor is driven by pulse-width-modulated (PWM), the model shows more temperature-rise in the magnets due to the abundant high frequency harmonics of PWM waveform. Furthermore, the finite element analysis (FEA) simulation results give more confidence for the proposed estimators.