AC losses in multifilamentary low AC loss Bi(2223) tapes with novel interfilamentary resistive carbonate barriers

For the AC application of multifilamentary BSCCO-Tapes at 50-60 Hz in power cables and transformers, the main components of the AC losses are hysteresis losses in the filaments and coupling current losses in the normal conducting matrix. Coupling losses can be reduced by enhancing the matrix resitivity and by applying a twist to the filaments. We developed a novel multifilamentary BSCCO tape in an Ag matrix with resistive SrCO3 barriers between the filaments to enhance the transverse resistivity. AC loss measurements on two different types of conductor designs are shown in this paper. In the first series of conductors the barrier forms something like a honeycomb structure in the cross-section between the filaments (DCB tapes). From this conductor type a series with Ag and AgAu(8wt%) matrix was prepared. The AgAu was chosen to increase the matrix resistivity compared to Ag, In the second series of tapes the conductor structure is similar to a Rutherford cable (RBB tapes). Six bundles of 7 filaments are stacked round a central SrCO3 core and deformed to a tape. All types of tapes have been twisted with a twist length down to 7.5 mm. In the AC transport current loss measurements we find a loss reduction in the RBB tapes due to the fact that the filaments in these tapes are nearly fully transposed. In external AC fields loss reductions in parallel as well as in perpendicular fields are found in both conductor series due to the decoupling of filaments.