Performance Comparison Between Rare-Earth and Ferrite-based PM Transverse Flux Generators for Small-Scale Direct-Drive Wind Turbine

The direct-drive (gearless) permanent magnet generator system has a high potential for wind turbines because of its performance efficiency, robustness, low maintenance, and reliability compared to other generator systems. Transverse flux permanent magnet generators (TFPMGs) have high-power density and modular structures, making them a proper candidate for direct-drive wind turbine applications. The main disadvantage TFPMGs is the high cost of PMs and increment of PM demagnetization risk with rising temperature. This paper is dedicated to a comprehensive comparison of the three-phase constructed rare-earth and Ferrite TFPMGs considered in small-scale direct-drive wind generator applications (320 rpm, 3000 W). The comparison includes operation principles, design procedure, performance (in terms of analyzing methods, electric and magnetic characteristics), cost, materials, and structures. It will be shown that the Ferrite TFPMGs can have acceptable performance for low-cost wind turbines applications.