Frame-to-Shaft Voltage and End-to-End Shaft Voltage Analysis According to Eccentricity in IPMSMs

Common-mode voltage (CMV) by switching pattern of space vector pulse width modulation (SVPWM) excites the parasitic capacitance links in the motor and results in frame-to-shaft voltage. In addition, asymmetric magnetic fields by common-mode current (CMI), eccentricity, and demagnetization causes the end-to-end shaft voltage. The winding-to-rotor parasitic capacitance, main parameter affecting the frame-to-shaft voltage, is depending on the distance between the winding and the rotor. For this reason, the eccentricity affects both the frame-to-shaft voltage and the end-to-end shaft voltage because the eccentricity makes the air-gap unbalance. This study proposes the analytical method for effect of the eccentricity on both frame-to-shaft voltage and the end-to-end shaft voltage in order to define how the eccentricity affects both shaft voltages. Further, both shaft voltages under the different eccentricity conditions are analyzed according to the copper shield, which is applied surrounding the shaft, in order to analyze how much copper shield can mitigate both shaft voltages.