Investigation of the Discharge Voltage in Electric Vehicle Motor Bearings

As the automotive industry undergoes a significant transition towards electric vehicles (EV), the matter of electric current discharge in motor bearings has emerged as a focal point of concern. This issue has gathered increased attention due to its potential to inflict damage upon bearing surfaces. The extent of damage inflicted by the discharges is intricately tied to the discharge energy, a factor directly influenced by both bearing capacitance and discharge voltage. In pursuit of a deeper understanding of discharge voltage dynamics within EV motor bearings, electric discharge tests were conducted using in-house modified single ball-on-disc contact and full bearing test equipment. Our test results at the single ball-on-disc contact show that discharge voltage adheres to a probabilistic distribution. Moreover, parallel investigations at the bearing level have yielded corroborative findings, reinforcing conclusions drawn from the single contact tests. These collective efforts contribute to a comprehensive understanding of electric discharge phenomena in motor bearings, essential for developing effective mitigation strategies and advancing the reliability of EV propulsion systems.