Sp. Ashworth, MEASUREMENTS OF AC LOSSES DUE TO TRANSPORT CURRENTS IN BISMUTH SUPERCONDUCTORS, Physica. C, Superconductivity, 229(3-4), 1994, pp. 355-360
Measurements of the losses of BSCCO-2223 and BSCCO-2212 tapes carrying
AC transport currents are reported. Measurements were made at 77 K at
frequencies in the range 20-60 Hz. The voltage waveforms generated by
the AC transport are presented as well as the AC losses. For peak tra
nsport currents below 90% of the DC critical current the losses of BSC
CO-2223 tapes are shown to be well described using an equation due to
Norris [5] which assumes the presence of a critical state in the super
conductor, and the power losses are proportional to the AC frequency (
hysteresis losses). When the AC peak current approaches the DC critica
l current flux-creep effects dominate the losses, and the power losses
cease to depend on frequency. In the BSCCO-2212 sample flux-creep eff
ects dominate at all currents. The examination of the voltage waveform
generated in the BSCCO-2223 sample shows the presence of both hystere
tic and flux-creep generated voltages.