A Comprehensive Modeling Method of Capacitive and Inductive Bearing Currents in Electric Vehicle Motors
Hao Yali1, Liu Ruifang1, Chen Like2, Li Zhihao1, Zhong Hui3
1. School of Electrical Engineering Beijing Jiaotong University Beijing 100044 China; 2. Donggu an Power Supply Bureau of Guangdong Power Grid Co. Ltd Dongguan 523000 China; 3. Suzhou Inovance Automotive Co. Ltd Suzhou 215104 China
Abstract：Bearing electric corrosion induced by variable-frequency drive motors has long been a problem. In recent years, with the widespread adoption of 800 V platforms in electric vehicles (EVs) and high-power power-electronic devices, this problem has become a current research hotspot in the electric vehicle field. Precise bearing current modeling is essential, directly impacting the vehicle's lifespan and reliability enhancement. However, existing comprehensive bearing current models often employ a simplifying assumption of a lumped-parameter capacitive circuit. Similarly, the approach to modeling the inductive circuit may not fully capture its high-frequency behavior. Therefore, this paper proposes a high-precision comprehensive model for both capacitive and inductive bearing currents. Unlike existing literature that models the actual equivalent common-mode total impedance as the excitation impedance, a comprehensive bearing current model is introduced by analytically coupling the capacitive and inductive loops. Subsequently, impedance testing was conducted on a 220 kW EV asynchronous motor. The study elaborates on parameter-extraction methods for capacitive and inductive circuits within the comprehensive bearing-current model. An experimental platform for the asynchronous motor was established, and a corresponding Matlab/Simulink simulation model was constructed. By comparing measured and simulated results for common-mode current, bearing voltage, and bearing current under identical operating conditions, the accuracy of the proposed model was validated. Simulation results show that, compared with the capacitive circuit in existing bearing-current comprehensive models, the improved capacitive circuit accurately simulates the motor's port-impedance characteristics across all frequency bands. Compared with the inductive circuits used in existing comprehensive bearing current models, the ladder equivalent circuits employed for both stator and rotor impedances more closely reflect practical conditions. This approach accurately reproduces the frequency-dependent skin effect characteristics of actual stator and rotor cores. When a 220 kW electric vehicle asynchronous motor is excited by both common-mode voltage and circulating bearing voltage, the error between simulated and measured bearing current values is less than 4%. In summary, this paper proposes a high-precision comprehensive modeling method for capacitive and inductive bearing currents in electric vehicle motors. The following conclusions are drawn. (1) This model accurately reproduces impedance characteristics across all frequency bands. (2) This model effectively predicts capacitive and inductive bearing currents during actual operation. (3) The model can be applied to all operating conditions where either capacitive bearing current alone or both capacitive and inductive bearing currents coexist, providing theoretical foundations and engineering guidance for analyzing and mitigating motor bearing electric corrosion issues.
郝雅丽, 刘瑞芳, 陈立珂, 李知浩, 钟辉. 一种电动汽车电机容性和感性轴电流的综合建模方法[J]. 电工技术学报, 2026, 41(12): 3998-4010.
Hao Yali, Liu Ruifang, Chen Like, Li Zhihao, Zhong Hui. A Comprehensive Modeling Method of Capacitive and Inductive Bearing Currents in Electric Vehicle Motors. Transactions of China Electrotechnical Society, 2026, 41(12): 3998-4010.
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2026, Vol. 41 
