Some factors determining the effective resistance between strands in flat cables (or superconducting filaments in tapes)

Two effects are considered which can influence the effective resistance bet ween crossing strands on flat cables or filaments in twisted tapes. As anal ogous cases, the one-layer Rutherford-type cable with classical superconduc tors and the tapes with twisted BSCCO filaments in a silver matrix in perpe ndicular magnetic fields are considered as a model. At first, the amount of the central core between the strands and the silver matrix between the fil aments increases the effective conductance compared with the direct current paths, which is supposed to be proportional to the touching area of filame nts. The increase factor is about two and can be easily suppressed by other effects, such as the contact resistance between the superconductor and the matrix. However, due to the strong anisotropy of critical parameters for h igh temperature superconductors, this effect can partially compensate the i nfluence of the usually weaker critical current density perpendicular to th e tape. The second effect is connected with the existence of the induced vo ltage between any points of crossing filaments. This leads to an additional effective conductance, proportional to the square of the total number of t he filaments. This contribution is prevailing for the anisotropic supercond uctors. Therefore, to obtain low ac coupling losses in BSCCO tapes, structu res with smaller filament number are required. This case is analogous to ro und structures, leading to ac losses proportional to the square of the laye r number in the field direction.