Effect of Stack Geometry on the Dynamic Resistance Threshold Fields for Vertical Stacks of Coated Conductor Tapes

The expanding capabilities of HTS flux pumps and rectifiers to provide kA+ currents necessitates the exploration of high-current switching phenomenon. One such phenomenon, the dynamic resistance, occurs in type-II devices carrying dc transport currents while exposed to ac magnetic fields. In the following, finite element analysis of the threshold field for dynamic resistance in superconducting cables comprised of N tapes connected in parallel and stacked vertically is presented. Cables are modelled using the commercial software COMSOL and the H-formulation. The models employ I
_c
(B, θ) and n(B, θ) data obtained on short samples at 77 K as inputs to more accurately reflect the variation in local properties within the superconductor. The finite element results are then compared with calculations made using analytical models assuming a critical state. The finite element data closely resembles that predicted for a strip for a single tape, rapidly tending towards the slab result as N increases.