Design and Performance Comparison of Nine-Phase Ferrite Spoke Interior Permanent Magnet Machines With Concentrated Windings for Traction Applications

Multiphase machines offer attractive fault tolerant features, compared to conventional three phase machines, which is significant for some safety-critical applications like electric vehicle traction and aerospace propulsion. This paper proposes a new nine-phase spoke interior permanent magnet machine with concentrated windings and ferrite magnets. An asymmetric nine-phase fractional slot concentrated windings (FSCW) with phase displacement are employed. Compared to conventional distributed windings, the concentrated windings are suitable for fault tolerant machines due to their inherent low coupling effect between each phase. Additionally, to address the high cost and price fluctuation of rare earth magnets, the low-cost ferrite magnets are used in the proposed design. The spoke type rotor design is capable of enhancing air-gap flux density because of the flux focusing effect. In this paper, the topology and nine-phase drive system will be introduced firstly. The torque capability and quality between different slot/pole combinations will be investigated. The torque density of the proposed design will be compared to conventional rare earth FSCW interior permanent magnet machine and a synchronous reluctance machine.