Shaft Voltage Reduction Technique by Layered-Shield of Wound Field Synchronous Motor

In modern society, the demand for traction motors is increasing as the era of electrification progresses. Recently, due to the high cost and supply instability of permanent magnets, there has been a surge in research focused on wound field synchronous motors (WFSM) over interior permanent magnet synchronous motors (IPMSM). The use of PWM inverters generates common mode voltage (CMV) in WFSMs, leading to the production of reactive power. This results in the generation of shaft voltage through the windings and internal parasitic capacitances of the motor. Consequently, this induced voltage in the bearings can lead to their damage. Bearing faults can cause not only motor breakdowns but also vehicle malfunctions. Therefore, this paper proposes a study on reducing shaft voltage in WFSMs. This research explores various techniques and methods to minimize the adverse effects of CMV on WFSMs, ensuring their robust performance in the ever-growing electric vehicle market.