AC losses to be reduced by twisting filaments in a silver-sheathed Bi-2223multifilamentary tape

An investigation is carried out to manifest types of AC losses in silver-sh eathed Bi-2223 multifilamentary tapes that can be reduced by twisting filam ents. The AC losses, in external magnetic fields parallel to the tape surfa ce, consist mainly of the AC losses due to macroscopic screening currents i n the multiple filaments and the AC losses due to the microscopic screening currents in the grains. The former loss depends greatly on the filament tw ist pitch, while the latter does not. Below the critical changing rate of a magnetic field at which screening currents at the outer filaments begin to saturate, the inter-filament coupling losses are added to the hysteresis l osses for the equivalent filament size. Consequently, an analytical model c an successfully explain experimental results that the macroscopic AC losses are considerably reduced by twisting filaments. (C) 1999 Elsevier Science B.V. All rights reserved.