H-formulation for simulating levitation forces acting on HTS bulks and stacks of 2G coated conductors

TLDR

Several techniques model HTSs; superconductors promise energy efficiency in transport and magnetic bearings, but the H‑formulation has not yet been used for levitation simulations. The study aims to develop solutions enabling the H‑formulation to predict levitation behavior of YBCO bulks or 2G wire stacks. The authors simulated levitation by restricting the domain to the HTS, applying boundary conditions and analytical source‑field expressions, and implemented the model in commercial finite‑element software. The H‑formulation accurately reproduces experimental levitation data, demonstrates that HTS stacks can replace bulks, and proves suitable for moving‑object problems, offering a viable alternative to other simulation approaches.

Abstract

Several techniques to model high temperature superconductors (HTSs) are used throughout the world. At the same time, the use of superconductors in transportation and magnetic bearings promises an increase in energy efficiency. However, the most widespread simulation technique in the literature, the H-formulation, has not yet been used to simulate superconducting levitation. The goal of this work is to present solutions for the challenges concerning the use of the H-formulation to predict the behavior of superconducting levitators built either with YBCO bulks or stacks of 2G wires. It is worth mentioning the originality of replacing bulks with HTS stacks in this application. In our simulation methodology, the movement between the HTS and the permanent magnet was avoided by restricting the simulation domain to the HTS itself, which can be done by applying appropriate boundary conditions and analytical expressions for the source field. Commercial finite element software was used for the sake of ease of implementation. Simulation results were compared with experimental data, showing good agreement. We conclude that the H-formulation is suitable for problems involving moving objects and is a good alternative to other approaches for simulating superconducting magnetic bearings.