Identification and Discussion of the Origin of a Shaft End-to-End Voltage in an Inverter-Driven Motor

This paper addresses shaft end-to-end and shaft-to-frame voltages that appear in the 400-V 15-kW induction motor driven by a voltage-source pulsewidth modulation inverter. It has been known that an inverter-fed common-mode voltage causes both shaft voltages. Extensive experiments are performed with an ungrounded motor subjected to a differential-mode voltage. Experimental results show that the differential-mode voltage applied across three-phase, two-phase, or single-phase stator windings also causes a shaft end-to-end voltage. It is concluded that the combination of a steep change in differential-mode voltage and high-frequency motor asymmetry causes a shaft end-to-end voltage. A motor model is presented to explain the generation of shaft end-to-end voltage.