Experimental and Numerical Analysis on Non-Uniform Current Distribution in Two-Tape Co-Wound HTS Coil

In coils composed of stacked no-insulation (NI) high temperature superconductor (HTS) tapes, the current flow patterns can significantly differ from transposed counterparts due to larger self/mutual inductances and contact resistances. In this study, three two-tape co-wound HTS coils are wound with different insulation methods, fully insulated, NI, and partially insulated. The charging test is performed and the experimental results are analyzed by observing the voltage ratio of two tapes. The voltage ratios show deviations from the theoretical inductive voltage ratios implying uneven current distribution between the tapes. A numerical analysis is carried out with a simulation model that couples the distributed circuit model with the finite element method model to understand these phenomena. Using the model, sensitivity analysis is adopted to explain quantitatively the contributions of each circuit parameter to non-uniform current distribution. Pinpointing the precise current distribution between tapes is challenging, yet experimental and numerical analysis results show certain tendencies influenced by inductive and resistive properties.