Theoretical and experimental loss and efficiency studies of a magnetic lead screw

This paper investigates mechanical and magnetic losses in a magnetic lead screw (MLS). The MLS converts a low speed high force linear motion of a translator into a high speed low torque rotational motion of a rotor through helically shaped magnets. Initial tests performed with a novel 17 kN demonstrator and a simplified motor model showed an efficiency of only 80 % at low load, however it was expected that the efficiency should be above 95 %. For understanding and future optimization a detailed study of the loss in the MLS is presented with the aim of identifying and segregate various loss components which was not accounted for in previously results. This is done through theoretical loss calculations and various experiments. It is concluded that the linear guide is the dominating loss component in the MLS demonstrator, while the losses in the axial thrust bearing is not as dominant as expected, further an efficiency above 94 % was measured.