Numerical Analysis on Critical Current of Multi-stage HTS Twisted Cable Consisting of Narrowed Soldered-Stacked-Square (3S) Wires

The critical current of a multi-stage high-temperature superconducting (HTS) twisted cable using cable-in-conduit conductor (CICC) is vital for its performance, since it determines the maximum current that the superconductor can carry in a superconducting state. This cable has a composite conductor structure with high current-carrying capacity, cooling efficiency, and stability, and can be used in high-field magnets. In this paper, based on a structure of a first-stage cable with HTS stacked-squared wires, a three-dimensional (3D) finite element model is established by the homogenization method to make analytical calculations of the current density distribution and critical current values of the multi-stage twisted cable. The simulation results show that the critical current at 77K of the multi-stage high-temperature superconducting twisted cable is 5.9 kA. Besides, the skin effect causes a higher current density near the outer side in comparison to the inner side. This work could be as a reference for designing a high field magnet using HTS square wires, and substantially reduces the computational complexity of simulating cables with complex structure.