Comparative Analysis of Consequent-Pole PM Vernier Machines with Different Rotor Types

Taking advantage of flux modulation effects, consequent-pole PM vernier (CPMV) machines have been widely investigated recently, featuring high torque density and PM utilization ratio. However, the low-order harmonics of modulated flux fields additionally cause high iron saturation, which results in relatively low average torque under overload conditions, especially for the CPMV machines with an interior CPM (ICPM) rotor. Therefore, this paper proposes two hybrid CPM (HCPM) rotors of PMV machines to improve the overload performance by adding SPMs into the conventional ICPM rotor. First, the topologies of the proposed HCPM rotors are presented, named HCPM1 and HCPM2 rotors, respectively. Then the HCPM rotors and a conventional ICPM rotor with the V-shaped PM arrangement are designed and optimized to find out the optimal design parameters. Moreover, the electromagnetic performances including back-EMF, torque performance, efficiency, flux-weakening capability, and end effect are comprehensively investigated and compared. It indicates that the two proposed HCPM rotors both can generate equivalently high average torque, efficiency, and flux-weakening capability, compared to the conventional ICPM rotor. Furthermore, the proposed HCPM2 rotor can produce ≥22.9% higher torque at overload conditions. In addition, due to the bipolar PM arrangement, the unipolar flux leakage of the HCPM2 rotor is significantly reduced and lower than 0.05T. Finally, the prototype of a 12-stator-slot/ 20-rotor-pole CPMV machine with the HCPM2 rotor is manufactured to validate the finite element (FE) results.