A Novel Structure of Electromagnetic Lead Screw for Wave Energy Converter

A magnetic lead screw (MLS) is a device that can help a wave energy converter (WEC) to transform the low-speed linear wave motion into high-speed rotary motion with no frictional contact. However, the dynamic performance of the MLS is insufficient because only the permanent magnet (PM) is used to couple the magnetic field between the rotor and mover. To improve the dynamic performance of the MLS, a novel structure of an electromagnetic lead screw (EMLS) for the application of a WEC is proposed in this paper. In the proposed EMLS, a helical-shaped PM is mounted on the inner side of the rotor, which is as same as the traditional MLS. However, helical-shaped slots are grooved on the surface of the mover, and two-phase helical-shaped AC winding is placed in these slots to generate the controlled helical-shaped magnetic field. In this paper, the topology and the operating theory are introduced firstly. Then, the three- and its corresponding two-dimensional axis-symmetric finite element analysis model is developed to analyze the performance of the proposed EMLS. Moreover, the design aspects are presented for the realization of the proposed EMLS. Then, the performance of the proposed EMLS is compared with that of the traditional EMLS. From the results, the proposed EMLS shows larger maximum thrust force than the traditional one. Finally, the potential use value and applications in WECs of the proposed EMLS are mentioned.