Modeling of eddy current loss in the magnets of permanent magnet machines for hybrid and electric vehicle traction applications

The eddy current loss in the magnets of permanent magnet (PM) motors in a hybrid electric vehicle (HEV) and plugin HEV is usually not taken into consideration in traditional motor design and analysis. However, due to the high conductivity of the rare-earth magnet, neodymium-iron-boron (NdFeB), and slot/tooth harmonics, there is eddy current loss generated inside the magnets. This loss may not attribute very much to the efficiency of the motor, but the temperature-rise inside the magnets caused by this loss can lead to the unpredictable deterioration of the magnets. In addition, the output voltage of pulse-width-modulated (PWM) inverter contains abundant high frequency harmonics, which induce additional loss in the magnets. This paper presents the modeling and analysis of eddy current loss in surface-mounted-magnets of PM motors operated by PWM inverters for HEV/PHEV and electric vehicle traction applications. In order to evaluate the loss from pure sinusoidal and PWM inverter supply, an analytical method is implemented, in conjunction with time-stepped finite-element analysis (FEA). The simulation results validated the proposed model.