With the expansion of high-voltage systems and the increasing demand for electric motors, bearing electrical erosion faults caused by shaft voltage have been continuously raised as an issue in electric vehicle (EV), urban air mobility (UAM), railway, and generator. Due to bearing electrical erosion fault, the rotor’s central axis becomes exposed to the risk of eccentricity fault caused by misalignment. Therefore, since bearing electrical erosion faults are closely related to other mechanical faults, research on shaft voltage that causes bearing electrical erosion faults is essential. In addition, due to technical, economic, and environmental reasons, the demand for and research on wound field synchronous motor (WFSM) continue to increase. In this study, to respond to bearing electrical erosion faults that may occur due to shaft voltage in WFSM and to ensure reliability, an analysis of the shaft voltage mechanism in WFSM was conducted. Furthermore, to validate the research, an experimental environment was established and empirical verification was performed.