New Equivalent Circuit of the IPM-Type BLDC Motor for Calculation of Shaft Voltage by Considering Electric and Magnetic Fields

Fast switching and common-mode voltage of the space vector pulse-width modulation inverter output create several parasitic capacitances according to the geometry of the motor. The windings emit the electric and magnetic flux inside of the motor. They create capacitance links and electromotive force (EMF) in the shaft, respectively. Those capacitance links and EMF generate a current through two bearings of the shaft and directly reduces the bearing lifetime. In this study, we propose a new design of equivalent circuit, taking into account all parasitic capacitor components.