Five-level SPWM Inverter for an Induction Motor with Open-end Windings

This paper presents a five-level inverter for an open-end winding induction motor. Five-level inversion is achieved by feeding an open-end winding induction motor with a 3-level inverter from one end and a 2-level inverter from the other end of the motor. The 3-level inverter used in the proposed drive is realized by cascading two 2-level inverters. The combined inverter system with open-end winding induction motor produces voltage space phasor levels identical to a conventional 5-level inverter. In the multilevel carrier based sinusoidal pulse width modulation (SPWM), used for the proposed drive, a progressive discrete DC bias depending upon the speed range is given to the reference wave so that the drive can operate in the k-level modes (k=2, 3, ... 5) depending on the speed range. The inverter with the higher DC-link voltage is switching less frequently, compared to the inverter with the lower DC-link voltage.