The AC loss of transport current in (Bi,Pb)-2223 superconducting tapes

The self-field AC loss of the untwisted (Bi,Pb)-2223 tapes made with differ ed matrices, number of filaments, critical currents and process techniques was measured in the frequency range from 20.8 to 363 Hz at 77 K. The losses of different matrix (Bi,Pb)-2223 tapes under different tensile strain were investigated at 50 Hz, 77 K. We find that: (1) in the case of I-m/I-c < 0. 4, the loss is hysteretic, while in I-m/I-c > 0.4, the eddy current loss mu st be taken into consideration; (2) above the critical current, the loss, w hich is shown resistive, is independent of current frequency, and differenc es in processing have a major impact; (3) below the critical current, the l osses, P, increase in proportion with I-m/I-c with slopes less than 3, whic h is not in accordance with the Bean model; (4) during the elastic stage th e self-field AC losses of AgMn and Ag matrix (Bi,Pb)-2223 tapes do not chan ge, while in yielding stage the unstable relations of AC loss vs, axial ten sile strain maybe caused by the serrated curve of stress vs. tensile strain relation, and the losses of both AgMn and Ag matrix tapes increase more in the plastic stage. (C) 2000 Published by Elsevier Science B.V.