Design and Investigation of Low-cost PM Flux Switching Machine for Geared Medium-speed Wind Energy Applications

Abstract

There has been increasing innovation in research to harness nonconventional electrical machines e.g., stator-mounted electrical machines like the flux switching machines (FSMs), in various applications such as wind power generation and electric traction. Hence, the need to further minimize the cost of electrical machines by avoiding designs using scarce rare-earth permanent magnets (PMs), especially if such machines were to be designed using PM materials. The approach in this article is to investigate the cost savings if a hitherto optimally designed 10 kW FSM which uses rare-earth PM is rather designed on less expensive ferrite PM for a medium-speed geared wind generator drive. Using 2D finite-element analyses and comparing the performance of two optimal benchmarks, it is shown that the ferrite design is heavier, leading to 61.2% reduction in the torque density compared to the rare-earth design. However, due to the high cost of rare-earth PMs, the active material cost of the ferrite design is found to be 35% cheaper. It is also found that due to deep saturation effects, the rare-earth design is more susceptible to demagnetization risks even within nominal load conditions, whereas the ferrite demagnetizes rapidly only beyond the nominal load.