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The emergence of stator-mounted wound-field flux modulation machines have created new possibilities for high torque density electric machines without brushes and slip rings. In this study, the comparative analysis of the wound-field flux switching machine (WFFSM) and DC-excited Vernier reluctance machine (DCVRM) is undertaken in terms of the double stator (DS) topology, targeting improved torque density. The finite element analysis (FEA) and parametric study of the 24-slots/10-pole DS WFFSM (DSWFFSM) and 12-slots/10-pole DS DCVRM (DSDCVRM) is undertaken using the same specifications of 1.5 kW at 300 r/min. The no-load and on-load performance is evaluated in terms of flux linkage, back-EMF, cogging torque, rated torque, overload capability and losses. The DSWFFSM demonstrates higher rated torque density (+14.9%), lower cogging torque (–72.6%) and higher efficiency (+1.6%) compared to the DSDCVRM. The parametric analysis also reveals the low torque ripple and high-power factor potentials of both machines over a wide operating range of excitation and armature currents. Due to comparative advantage, the prototype of the DSWFFSM is developed and tested to validate the study, with satisfactory results.

To overcome drastic increase in rare-earth permanent magnet cost, avoid the requirements of brushes, slip rings, and eliminate gear-box mechanism, a novel magnet-less dual electrical and dual mechanical port wound field-excited flux switching generator (DEDMP-WFEFSG) for direct-drive counter rotating wind turbine (D2CRWT) application is proposed in this article. The proposed DEDMP-WFEFSG encompasses a stator with dual non-overlapped armature and toroidal field excitation windings; thus, offers reduced overhang and makes the design compact. To ease the design process, lumped parametric magnetic circuit model (LPMCM) for one magnetic pole is formulated. To evaluate the LPMCM design, finite element analysis (FEA) study is undertaken in co-rotation and counter rotation with focus on power distribution between the inner and outer ports. From detailed analysis, it is evident that in comparison with the inner port, the outer port machine offers better average torque, power factor, and efficiency. Compared with co-rotation, counter rotation shows improved electromagnetic performance. Finally, to validate the LPMCM and FEA based simulation, a prototype is developed and tested with satisfactory results.