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

Abstract

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.