Approaches to Suppressing Shaft Voltage in Brushless DC Motor Driven by PWM Inverter

Abstract

This paper describes the approaches to suppressing the shaft voltage and bearing current by electrostatic shielding the stator end windings of the brushless DC motor driven by PWM inverter. At first, measured shaft voltage and bearing current are compared with those calculated waveforms to verify the common mode equivalent circuit of the brushless DC motor. Next, relationship between shaft voltage and stator winding to rotor capacitance is calculated using the common mode equivalent circuit. Finally, the electrostatic shielding of the stator end windings is evaluated to reduce the shaft voltage by experiments and calculations.