A Novel Eight-level Inverter System for an Open-end Winding Induction Motor

A novel eight-level inverter scheme, for an open-end winding induction motor drive, is proposed in this paper. The open-end winding induction motor is fed from four-level inverter from one end and two-level inverter from the other end. The four-level inverter used in this proposed drive is realized by cascading three two-level inverters. The combined inverter system with open-end winding induction motor produces voltage space phasor levels identical to a conventional eight-level inverter. The proposed eight-level inverter configuration requires lesser number of switching devices as compared to the conventional eight-level inverter scheme. Similarly, lesser- isolated power supplies are required when compared to the cascaded H-bridge configuration. This inverter scheme does not experience neutral-point fluctuations. In the multi-level carrier based SPWM used for the proposed drive, a progressive discrete DC bias depending on the speed range is given to the reference wave to reduce the inverter switching.