Design of a magnetic lead screw for wave energy conversion

This paper deals with the development of a magnetic lead screw (MLS) for wave energy conversion. Initially, a brief state-of-the-art regarding linear PM generators and magnetic lead screws is given, leading to an introduction of the magnetic lead screw and a presentation of the results from a finite element analysis used to find the magnetic forces. Furthermore, the force per magnet surface area measure is presented as a better alternative to the force density measure, which is often used for linear magnetic devices. Based on this, the overall design of a 500 kN MLS is presented focusing on the bearing supports used to compensate for the magnetic attraction forces and the resulting deflection of the rotor. Also, in order to avoid some of the production related disadvantages of using surface mounted magnets, an embedded magnet topology is proposed. To demonstrate the technology a scaled 17 kN MLS is presented together with experimental results.