On the Effect of the Rotor Polarity on the Performance of Fractional Slot SPM Machines

Concentrated winding fractional slot permanent magnet (PM) machines are currently considered as viable candidates for various applications. These machines offer many advantages over distributed winding PM machines, especially: reduced copper losses thanks to short end-windings, wide flux-weakening range, improved fault-tolerance capability, low cogging torque. These performance could not be accessed without a convenient selection of the slot-pole combinaisons. Within this background, the paper deals with a FEA-based investigation of the torque production capability exhibited by two topologies of fractional slot surface-mounted PM machines sharing the same number of slots in the stator while they differ by the number of poles in the rotor. The FEA results are validated by experiments carried out on prototypes of the machines under comparison.