Design Considerations of Five-Phase Machine With Double p/3p Polarity

In the context of traction drives with required torque transient capabilities and a classically wide flux weakening speed range, this paper gives design considerations of a particular double-polarity (DP) five-phase machine. Beyond its intrinsic fault tolerance due to its five phases, its specificity is the ability to develop torques of comparable values under three kinds of supply: with only first, third or both first, and third sinusoidal currents. This property, due to first $(E_{1})$ and third $(E_{3})$ harmonic electromotive forces of comparable values, gives more degrees of freedom for the control of the machine. Unlike three-phase sinusoidal machine, flux weakening is no more the unique solution when maximum voltage is reached. Thanks to the extra degrees of freedom in this kind of machines, more possibilities for the control of the torque and current supply can be applied. At first, elements for the choice of slots/poles combination of such DP machines are given. Then, in the case of an interior permanent magnet synchronous machine, possible adaptations of the rotor are proposed in order to bring the double p/3p polarity property. The last design criterion considered is the level of eddy-current losses, important at high frequencies. For the proof of the concept effectiveness, a prototype with a five-phase fractional-slot concentrated winding of 40 slots and 16/48 poles is presented with results from the experimental setup and finite element modeling. A comparison with the equivalent no-fault-tolerant three-phase 24 slots/16 poles machines is also carried out.