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.