Investigation on the Performance of N-S Consequent Pole Permanent Magnet Synchronous Machines with Different Slot/Pole Combinations

The consequent pole permanent magnet synchronous machine with N-S-iron–S-N arrangement (NSCP-PMSM) adopted 1/3 of the iron core instead of permanent magnet (PM) to ensure high torque density and improve the utilization rate of PMs. The different unit machines with 3-slot/2-pole, 9-slot/2-pole, 15-slot/4-pole, 21-slot/4-pole as slot/pole combinations are established for comparative analysis, including back electromotive force (EMF), airgap density, output torque, cogging torque and unbalanced magnetic pull. The reason for absence of even harmonic back EMF and airgap density in NSCP-PMSM is analyzed, the output torque with different slot/pole combinations are compared, the cycle number of cogging torque are derived, and the condition for eliminating unbalanced magnetic pull is given. The effect of different slot/pole combinations on the performance of NSCP-PMSM was obtained with finite element analysis. Finally, a prototype of NSCP-PMSM with 54-slot/12-pole was manufactured to verify the correctness of the above analysis.