A Low Thrust Ripple Flux-Reversal Transverse Flux Permanent Magnet Linear Generator Used in Direct Drive Wave Energy Converter

Direct-drive wave energy converter (DDWEC) is more widely used due to its simple structure and high conversion efficiency. Different kinds of linear machines are used in DDWEC to improve the power density. Among them, transverse flux linear machine uses perpendicular magnetic flux path and axial stacked silicon steel sheets to reduce iron loss and enhance power density. In this paper, a flux-reversal transverse flux permanent magnet linear generator is proposed. The winding connection type of this configuration is elaborated. Circumferential three-phase type, axial three-phase type and the proposed one are compared to obtain higher power density and lower thrust ripple. The proposed three-phase winding configuration has the lowest thrust ripple (0.76%) and decent average thrust (247.01N). A prototype was manufactured and an experimental testing platform was built. The measured back EMF values in the experiment showed a consistent trend with the FEA values. Owing to the convenience in changing the armature winding connection and excitation winding connection, the proposed machine has high design flexibility. The proposed machine is suitable to be used in high power density and low thrust ripple applications. When the proposed machine uses dual three-phase winding or six-phase winding, it also has high fault tolerance ability.