PWM switching strategy for the elimination of common mode voltage of a two-level inverter drive with an open-end winding induction motor configuration

Abstract

Adjustable speed drives are known to generate common mode voltages which cause motor shaft voltages and bearing currents. It was demonstrated that two two-level inverters connected to either sides of an open-end winding induction motor is capable of achieving the functionally of a three-level inverter. The common mode voltage generated by a three-level inverter can be eliminated by switching only the voltage space vector combinations which do not produce the common mode voltage. A PWM switching strategy to eliminate the common mode voltages using an open-end winding induction motor drive is presented in this paper, which tends to avoid the electrostatic coupling of the stator and rotor reducing the bearing currents and leakage currents. The present scheme uses single DC-link with about 58% of the DC-voltage compared to conventional two-level VSI.