Improved performance of independent two induction motor drives fed by a four-leg inverter

This paper presents the experimental results of the independent drive characteristics of two three-phase induction motors (IMs) fed by a four-leg inverter (FLI). The FLI is a single inverter that can drive two three-phase AC motors independently. The inverter consists of four legs and two capacitors connected in a series. The PWM techniques in three-phase voltage source inverter are not directly applicable for the FLI. Also, the drift phenomenon of the neutral point potential of two-sprit capacitors is observed in the starting time of motors and speed change. The drift causes the reduction of inverter DC-bus voltage utility factor. Therefore, the drift must be restrained. This paper shows the modulation technique to restrain the drift in the FLI. In addition, neutral point potential performance in changing the capacitance of two-sprit capacitors is compared. Then, experimental results are verified that two IMs independent drive can be realized by the modulation strategy.