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 different 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 must be taken into consideration; (2) above the critical current, the loss, which is shown resistive, is independent of current frequency, and differences in processing have a major impact; (3) below the critical current, the losses, P, increase in proportion with I_m/I_c with slopes less than 3, which is not in accordance with the Bean model; (4) during the elastic stage the self-field AC losses of AgMn and Ag matrix (Bi,Pb)-2223 tapes do not change, while in yielding stage the unstable relations of AC loss vs. axial tensile 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.