Design and Analysis of New Dual-Stator Flux Modulated Machines With Dual-PM Excitation

This article proposes new dual-stator flux modulated machines with dual-permanent magnet (PM) excitation (DS-FMDPMMs) for direct-drive applications. The proposed DS-FMDPMMs are characterized by employing consequent-pole (CP) PMs on both the stator and rotor sides. By using dual-layer CP PMs, the DS-FMDPMMs can perform the bidirectional flux modulation effect to enhance the torque capability. In addition, the merits of dual-stator structure, such as high space utilization, high torque density, and power factor are inherited in the proposed machines. The design principle of DS-FMDPMM is provided at first, and the formed three representative DS-FMDPMMs with different stator-PM arrangements are proposed. Then, the design considerations of three DS-FMDPMMs are described in detail, which includes the armature winding design, the selection of stator-slot/rotor-pole combination, and the influence of critical structural parameters on torque. In order to find an optimal direct-drive candidate among the three DS-FMDPMMs, a quantitative electromagnetic performance comparison is developed through finite element analysis (FEA). The results show that among the three machines, DS-FMDPMM-I accommodates the highest torque density, lowest torque ripple, best over-load torque capability, and highest efficiency. Moreover, to further verify its performance advantages, the electromagnetic performances of DS-FMDPMM-I and two typical dual-stator flux modulated PM machines are compared through FEA. Finally, a prototype of the optimal DS-FMDPMM is manufactured and tested to validate the effectiveness of FEA-predicted results.