Influence of Saturation on the Airgap Induction Waveform of Five-Phase Induction Machines

The third harmonic of the airgap induction plays a more important role in high-phase machines than in conventional three-phase machines, because it can be used to optimize the airgap waveform and produce useful torque. The paper assesses the influence of saturation on the production of an optimized induction waveform in the airgap of five-phase induction machines through the third harmonic induction component. It is shown that teeth and core saturation have opposite effects in what concerns the production of optimized airgap induction. The paper also shows that, different from three-phase machines, a third harmonic airgap field can exist even when the five-phase machine is connected in delta or connected in star with neutral conductor. Analytical expressions to approximate the airgap induction including saturation effects are presented and the joint effect of stator current and saturation is discussed. Experimental results obtained from a prototype machine are presented and compared to theoretical values.