Performance of an asymmetrical six-phase induction machine in single-and two-neutral point configurations

An asymmetrical six-phase induction motor drive can be realised with either one or with two isolated neutral points. Each of the two possibilities has its own merits and shortcomings, which are reviewed in the paper. Further, the performance of these configurations is compared, using waveforms and spectra of the phase voltage and current, obtained by simulations and experimentally. Total harmonic distortion (THD) of the phase voltage and current is also calculated as a function of the modulation index and is used as a figure of merit. It is concluded that the drive with two isolated neutral points offers better phase voltage and current THDs, but is inferior from the point of view of post-fault control.