A spoke-type IPM machine with novel alternate airspace barriers and reduction of unipolar leakage flux by step-staggered rotor

This paper proposes a spoke-type IPM machine with novel alternate airspace barriers, through which higher torque capability and better manufacturability can be obtained, without remarkable deterioration in mechanical strength. Further, the influence of end leakage flux in the novel IPM design is investigated by 3-dimensional (3D) finite element (FE) method, including the leakage flux characteristics and torque capability. Furthermore, a step-staggered rotor is proposed to reduce the unipolar leakage flux and magnetization of the end shaft. As an extension, unipolar leakage flux is further investigated in consequent-pole PM machines, as well as the validity of step-staggered method. Finally, prototypes are fabricated and tested to verify the foregoing analyses, including the magnetic field at the end shaft and the output capability.