An Improved Performance of Five-Leg Inverter in Two Induction Motor Drives

This paper presents an improved method of voltage utility factor from 50% to 86.6% for a five-leg inverter when two induction motors are driven in vector control and in a condition that a frequency of two motors isn't extremely different, and the improved method of voltage utility factor is theoretically shown. The five-leg inverter is a single inverter that can drive two motors independently and consists of five legs. U and v phases of both motors are connected in each leg respectively whereas w phase of both motors is connected in a common leg. In the five-leg inverter, because w phase of the motors are connected in the common leg, it causes difference from a switching pattern of w phase in two motors. For this reason, the modulation methods for a three leg inverter can't use for the five-leg inverter. Many modulation methods for the five-leg inverter have been proposed, but voltage utility factor is 50% in these methods. From the reason a maximum voltage utility factor of the three leg inverter is 100%, the voltage utility factor of the five-leg inverter is lower than one of the three leg inverter