Interleaved switching of symmetrical six-phase drives

An interleaved switching approach for a symmetrical six-phase drive is examined in this paper. The system consists of a six-phase machine and a pair of common three-phase voltage source inverters. The outputs of both inverters are controlled by a "Naturally Sampled Pulsewidth Modulation"-technique. It is shown that time-shifting the switching pulses of both inverters can result in a significant reduction of current distortion on the machine side and hence, efficiency improvement. Depending on the machine parameters, there exists an optimal shifting-ratio, which is derived analytically in a general form. Simulations and experiments validate this approach. The results emphasize the benefits of symmetrical six-phase drives in high-power ranges, such as wind energy systems, where full redundancy and energy efficiency is required.