A preliminary study on superconducting linear motors in high-dynamic applications

This paper presents a preliminary study on the feasibility of second-generation high-temperature superconductors (HTS) to replace permanent magnets in linear motors (PMLM) for high-dynamic applications to improve force density. Such an application, demanding a fourth-order motion profile, is solved with an HTS linear motor (HLM) containing DC-operated HTS coils in the stator and three-phase AC commutated coils in the mover. For a comparative study, the HLM and PMLM are investigated for several design parameters through Finite-Element-Method (FEM) - operating in no-load condition - in a two-dimensional (2D) study. With DC loss of the HTS coils estimated from FEM and knowing a-priori the maximum allowed heat-load, operating limits of these coils are determined, and such thermally feasible coils deliver the required force in a further detailed design. This study shows that when using the HTS coils at 77 K, RMS flux density in the airgap and force density of the HLMs are pretty comparable to PMLMs. However, when the HTS coils are operated between 25-60 K and 20-45 % of the critical current, several coil designs deliver above 1 T RMS flux density in the airgap, and after optimization, these HLMs can potentially reduce the active volume by at least an order of magnitude and improve force density by a factor of 2 when compared to PMLMs.