Bi-2223 silver sheathed tapes are currently used in prototypes of HTS power devices, where they generally carry an electrical ac current and are exposed to an alternating magnetic field that may have different orientation with respect to the tape. In this work we describe the experimental set-up for measuring ac losses of HTS tapes due to the simultaneous presence of ac current and ac magnetic field. The experimental results have been compared and contrasted with a numerical model purposely developed for the evaluation of current distribution and ac loss in HTS tapes.

Improved measuring procedures and interpretation efforts have shown that the critical state model is fully applicable for describing the behaviour of HTS tapes for power applications. By this means, we could consistently analyse magnetic and transport measurements and study possible inhomogeneities and geometrical peculiarities in BSCCO-2223 tapes. Examples of such an analysis are given in this contribution. Losses in multistrand conductors require a more complex modellization and further development of the experimental procedures; the results of a.c. transport measurements on a 13 m long, multilayer, prototype conductor sample are also discussed here.

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Experimental investigations on Ag-sheathedBSCCO tapes show that losses in the ac-current transport regime are not of purely hysteretic nature. A contribution due to the eddy currents in the silver matrix is present and detectable in the low current limit. I n the present paper we extend an existing model in order to account for this contribution. The tapesuperconducting core is regarded as a strip or as an ellipse. The expressions we obtain are analyzed and compared to experimental data.Iiirkx Terms-AC losses, BSCCO tape, eddy currents, silver matrix.