Design Optimization and Performance Comparison of Two Linear Motor Topologies With PM-Less Tracks

Abstract

Linear Permanent Magnet Synchronous Motor (LPMSM) topology is the preferable choice for a linear motor in terms of high force density and good overall performance. However, its main drawback is the relatively high price caused by the extensive usage of rare-earth materials in the track. This factor is critically important, especially when this type of motor has to be used in a long-stroke application, such as storage or airport transportation lines where the main prerequisite is a low-cost, passive and robust track. Therefore, Linear Induction Motor (LIM) and Linear FluxSwitching Permanent Magnet Motor (LFSPMM) are two possible alternatives suitable for long-stroke applications. Considering only the price of the track, LIM topology, with its flat aluminum secondary is most attractive. Nevertheless, the absence of rare-earth materials limits the propulsion force generated by the LIM. Another attractive alternative is the LFSPMM topology, which also has a passive secondary, but it incorporates a limited amount of rare-earth materials in its mover, improving its force generation capabilities. As a relatively new topology, the research on LFSPMM is still limited [1], [2]. The existing design solutions for LIM having relatively small volume, have lower force density [3], compared to the designs having much larger overall dimensions [4]. Therefore, a direct comparison between LIM and LFSPMM is very difficult. Based on the volume of a benchmark LPMSM topology, in this paper, a comparison between LIM and LFSPMM is performed. To obtain optimal designs within this volume, a fast converging, semi-analytical methods are used for modelling both topologies and the results are used to compare LIM and LFSPMM topologies.