Intriguing Behavioral Characteristics of Rare-Earth-Free Flux Switching Wind Generators at Small- and Large-Scale Power Levels

In this study, the design optimization of rare-earth-free flux switching machines (FSMs), viz., ferrite permanent magnets (PMs) and wound-fields (WFs), 12-stator slots/10-rotor poles (12/10) and 12/14, has been undertaken in finite element analyses for wind generator applications, in both small-scale (10 kW) and industrial-scale (3 MW) power levels. The focus is on the performance feasibility of these machines to replace rare-earth PMs, as well as on the suitability of the proposed machines for industrial-scale wind power generation. Hence, it is found that the high torque ripple effects typified by the flux focusing characteristics of FSMs are not enhanced by simply using rare-earth-free materials in place of rare-earth PMs, as is usually suggested. Among other listed findings, it is also found that at 10 kW power, the ferrite PM-FSM performs better in terms of lowest torque ripple and active mass, for both machine configurations. At 3 MW power, WF-FSMs have better torque densities, while ferrite PM-FSMs have better torque ripple values, which result in drastic reductions in the cost of the WF-FSMs at industrial-scale power levels compared to other sampled wind generator topologies. To this end, a 10 kW WF-FSM prototype of the considered variant was manufactured and tested for the first time, with some novel implementations. Based on the reported measured no-load to full-load tests, the study is proven beyond reasonable doubt.