Interactive Ripple Harmonic Minimization of Fractional Slot Permanent Magnet Machines Using Space-Shifted Wye-Delta Winding

This paper presents a ripple minimization strategy through interactive space harmonic minimization of fractional slot permanent magnet (PM) machines for high-performance applications. This method uses a space-shifted wye-delta configuration of its stator winding and avoids the need for magnet shaping or skewing of the rotor. The proposed strategy reduces the on-load cogging torque and utilizes the space harmonics interaction of stator and rotor. The effectiveness of the proposed method is shown by analyzing the performances of two fractional slot; 12-slot/10-pole (q=2/5) and 12-slot/8-pole( q=1/2) PM machines. Application to a 12-slot/10-pole PM machine shows a torque-density improvement along with very low ripple performance compared to the existing techniques. Moreover, in comparison with the existing ripple minimization techniques, this strategy can achieve either the same or better ripple performance with either the same or higher average torque depending on the slot/pole combination. The effect on loaded and open-circuit cogging torque is also presented and compared with existing techniques.