Sectional Modular Technology for Reducing Detent Force of Linear Unit in Linear-rotary Flux-switching Permanent-magnet Generator for Wind-wave Combined Energy Conversion

A linear-rotary flux-switching permanent magnet (FSPM) generator (LRFSPMG) is a potential candidate for a wind-wave combined energy conversion (WWCEC) system. The linear unit of the LRFSPMG is a tubular FSPM linear generator (TFSPMLG), which like other permanent magnet linear generators, has an inherent detent force problem. To alleviate this problem, a sectional modular technology scheme is investigated to reduce the detent force of the TFSPMLG. Firstly, the structure is briefly introduced and the detent force analyzed. Secondly, the sectional modular TFSPMLGs are presented and their feasibility verified with respect to the stator of the TFSPMLG being split into two and three sections, forming Modulars I and II, respectively. After that, the detent force suppression principle, and the effects that the sectional modular structures exert on the detent force are analyzed. According to the analysis results, two methods are presented to suppress the detent force: one is to suppress the magnetic coupling effect; the other is to reduce the remaining harmonics. Finally, the three TFSPMLGs, including the initial TFSPMLG, Modular I, and Modular II, are comparatively analyzed by finite-element analysis (FEA). The results show that both the detent forces are greatly reduced without sacrificing the back electromotive force (EMF) and average electromagnetic force, thereby proving the effectiveness of the TFSPMLG with a sectional modular structure.