Analysis of Influencing Factors for EDM Bearing Currents in Motors

As a critical supporting component in the electric vehicle powertrain, the lifespan of bearings directly impacts the safety and operational efficiency of the vehicle. Bearings electrical corrosion is one of the primary causes of bearing failure [1]. Among various types of bearing currents, the EDM (Electrical Discharge Machining) type bearing current has a particularly significant impact on damage [2]. Therefore, this paper investigates the influencing factors of EDM currents in motor bearings based on actual automotive operating conditions. Firstly, the generation mechanisms of bearing voltage and current are clarified, and the coupling paths of bearing currents are analyzed. Subsequently, based on elasto-hydrodynamic lubrication (EHL) theory, the bearing capacitance and its influencing factors are examined. Furthermore, a test platform for bearing current measurement based on a single-motor system was established. Using oil-lubricated bearings as the subject, experiments were conducted to analyze the factors influencing EDM bearing currents in motors, exploring the response characteristics of EDM-type bearing currents to operational parameters such as rotational speed, oil flow rate, oil temperature, and torque. Comparative results indicate that the generation and discharge energy of EDM currents are highly dependent on rotational speed, oil flow rate, and oil temperature, while the influence of torque is relatively weak. The findings can provide a reference for experimental research on bearing electrical corrosion damage and the development of suppression methods.