Reduction of sub-harmonic effect on the fractional slot concentrated winding interior PM machines by using spoke-type magnets

In this paper, a spoke-type IPM motor (buried with circumferentially magnetized magnets) with fractional-slot concentrated windings is designed to block the two-pole sub-harmonic and, thus, reduce the iron core losses and torque ripple. This is demonstrated by the comparison of a conventional V-type IPM configuration and a designed spoke-type machine. Both of them have 12-slot/10-pole configurations with the same stator structure. The simulation results indicate that under the same design specifications, the spoke-type motor has less magnet consumption and exhibits much smaller iron core losses and torque ripple than that of its V-type counterpart, especially when operated at high speed. Finally, the mechanical stress of the designed spoke-type machine rotor is analyzed by finite element analysis.