ScholarWorks@성균관대학교

초록

This article proposes a hybrid approach that combines magneto-quasi-static finite element analysis (MQS-FEA) with analytical formulas to efficiently estimate ac copper losses in an electric vehicle propulsion motor with hairpin windings. The method accurately accounts for both skin and proximity effect losses, while substantially reducing computation time. Skin effect losses caused by both the sinusoidal current and pulse width modulation (PWM) harmonics are calculated using a reactance-limited loss equation, which effectively captures current redistribution and accelerates loss evaluation. For proximity effect losses, MQS-FEA is first used to compute the slot leakage flux and PM fields under sinusoidal excitation. The frozen permeability method is then applied to estimate PWM-induced slot leakage flux. To improve the accuracy of proximity loss estimation, a probabilistic approach is employed. The representative external fields are defined by selecting harmonic components based on kernel density estimation of the continuous probability density function of element-wise flux densities. The resulting eddy current losses are evaluated using the reactance-limited formulation, incorporating PWM-induced fields. Compared with using only transient FEA, it also facilitated rapid efficiency map construction. Finally, experimental validation using a 150 kW target motor confirmed the accuracy of the proposed method.

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