Power dissipation in composite Ag/Bi-2223 tapes with twisted and untwisted filaments

Power dissipation in a set of multifilamentary Bi2223 silver sheathed composite tapes (with 61 filaments) was measured using AC magnetization and transport loss measurement techniques. In order to decrease the interfilamentary bridging and thus electromagnetic coupling, the space between filaments was considerably increased. The tape samples used in this study were with twisted (twist pitch 15 mm) and untwisted filaments. Critical currents were of the order of 55 Amps, as measured by a standard four-point technique, and corresponds to a critical current density of approximately 9 kA cm^-2. The AC transport current losses were measured by a standard four-point lock-in method; in the range of-the transport current frequency of 40-160 Hz. The magnetization loss measurements were performed in a sinusoidally varying external magnetic field, at the frequency range of 11 to 155 Hz. The external magnetic field was oriented parallel to the plane of a tape. The obtained results are compared with theoretical predictions of the critical state model