Winding Configuration and Performance Investigations of a Tubular Superconducting Flux-Switching Linear Generator

Primary permanent-magnet linear generators have an advantage of a simple secondary structure, which is suitable for the application of wave energy conversion. Based on vernier hybrid machines (VHMs), which are widely used for direct-drive wave energy converters, this paper proposes a tubular superconducting flux-switching linear generator (TSFSLG), which can effectively improve the performance of this kind of generators. Magnesium-diboride (MgB₂)-type direct current superconducting windings are used in the generator to increase the magnetic energy and overcome the disadvantages of easily irreversible demagnetization of the VHMs and high-voltage regulation of a permanent-magnet flux-switching linear generator (PMFSLG). The alternating current superconducting windings are implemented to improve the efficiency. Based on the MgB₂ superconducting wire produced and measured in the laboratory, the superconducting windings structure used for the generator is designed. The coil-EMF vector is optimized, and the losses of superconducting windings are analyzed. In addition, by using the finite-element method, the no-load performances of the generator are analyzed and compared with the ones of a VHM and a PMFSLG. Finally, the on-load performance of the TSFSLG is obtained by finite-element analysis and compared with the VHM and the PMFSLG. The results validate that the proposed generator is more suitable for wave energy conversion than its counterparts.