Shaft-to-Frame Voltage Mitigation Method by Changing Winding-to-Rotor Parasitic Capacitance of IPMSM

Common-mode voltage by switching pattern of space vector pulsewidth modulation excites parasitic capacitance coupling in interior permanent magnet synchronous motors, and it finally causes a shaft-to-frame voltage. Among all parasitic capacitances, winding-to-rotor parasitic capacitance has the greatest effect on the shaft-to-frame voltage, which means the winding-to-rotor parasitic capacitance must be suppressed for noticeable mitigation of the shaft-to-frame voltage. This paper proposes two suppression methods by changing the stator winding-to-rotor and end winding-to-rotor capacitances. First, the modified winding shape is utilized for the suppression of stator winding-to-rotor capacitance. Second, a copper shield is applied to suppress the end winding-to-rotor parasitic capacitance. Finally, both the methods are applied together to mitigate the effect of the stator winding-to-rotor and end winding-to-rotor capacitances on the shaft-to-frame voltage.