Experimental and numerical investigation of superconducting magnetic bearings with thinned HTS tape stacks

Abstract Superconducting Magnetic Bearings (SMBs) have the potential to revolutionize maglev technology by enabling frictionless levitation, higher efficiency, and intrinsic stability. High-temperature superconductor (HTS) tape stacks offer better mechanical properties, improved thermal conductivity, and greater design flexibility compared to bulk superconductors. In SMBs, the levitation force is a key parameter for improving the efficiency and practical feasibility of the system. For SMBs based on HTS tape stacks, one approach to enhance the levitation force is to increase the critical current density. However, higher critical density typically requires more advanced tapes, which are expensive and have limited availability. In this study, the influence of HTS tape thinning on the levitation force of an SMB was investigated by reducing the thickness of the non-superconducting metallic substrates through electropolishing. The levitation force between a Halbach array and a stack fabricated from electropolished tapes was measured at various temperatures under zero-field cooling conditions. We compared the experimental results with two previously validated 3D models and two 2D models. The measurements indicated an increase in the maximum levitation force after tape thinning at intermediate and high temperatures, while at the lowest investigated temperature this enhancement was not observed. Parametric simulations showed that reducing the tape thickness can enhance the levitation force through an increase in the engineering critical current density. The 2D models overestimated the maximum levitation force at 54.7 K by approximately 50%, whereas both 3D models reproduced the measured levitation force at this temperature with a maximum error of approximately 2%. We showed that this discrepancy originates from the assumption of infinitely long permanent magnets in the 2D models, which overestimates the magnetic field magnitude within the tape stack compared to the finite-depth 3D case. These results clarify the influence of tape thickness on SMB performance and highlight the importance of 3D modeling for the accurate design and optimization of superconducting magnetic levitation systems.