Shaft Voltage Analysis According to Parasitic Capacitance Variations in a Wound Field Synchronous Motor

With the expansion of high-voltage systems and the growing demand for electric motors, shaft voltage-induced bearing electrical erosion has emerged as a critical problem in the electric vehicle (EV) industry. Shaft voltage leads to increased dielectric breakdown of bearing lubricants and elevated vibration, which in turn raises the frequency of electrical discharges within bearings and can result in irreversible motor damage. This study analyzes the effects of changes in stator end winding length and rotor winding arrangement in a wound field synchronous motor (WFSM) on parasitic capacitance and shaft voltage characteristics. Variations in these winding configurations during the manufacturing process alter the parasitic capacitance inside the motor, thereby influencing the magnitude of shaft voltage. The effects of winding design on parasitic capacitance and shaft voltage were analyzed to support reliability improvements in EV motors.