| Summary: In this study, AC losses were investigated in silver clad Bi:2223/Ag tape which produced by two different methods named PIT and CTFF, as functions of temperature, frequency, AC field, DC field and according to perpendicular or paralel orientation of the magnetic field with respect to tape surface. Modelling equations were derivated for the calculation of AC losses and these losses were calculated by made of a computer program. Hysteresis loss, eddy current loss, interflamantary coupling loss, flux flow loss and their contributions to AC losses were determined thanks to results of experimetal data and theoretical calculations. And then it was investigated how to minimise the AC losses.
AC losses in the sample of CTFF for both orientations were observed to be depend on the field amplitude, temperature and strongly frequency. We have measured in perpendicular and parallel orientations of the magnetic field with respect to the CTFF tape sample surface at different temperatures and wide frequency range because of the sample dependent on excessively frequency. We note that peak temperatures of the imaginary part shift to the lower field region with increasing AC field amplitude. The loss because of flux creep was determined to be very small by magnetic relaxation experiments. We have observed that the hight of coupling loss peak increases with increasing temperature in contrast to parallel orientation. We have observed that the irreversibility line determined from AC susceptibility method locates at higher temperature than that was obtained from DC magnetization method. It was observed that AC loss was increased with the presence and increase of DC field at a constant temperature and in all frequency ranges in the presence and absence of DC field. Also we observed a reduction in the loss maxima with increasing AC magnetic field amplitude in the presence of DC field. When two different constant temperatures (20 and 30 K) and wide frequency ranges were investigated, at AC losses for the sample of PIT tape a maximum was not observed in this frequency range (up to 10 kHz) unlike the observations in CTFF sample.
Key Words: AC loss, Bi:2223/Ag superconducting tape, critical state models, critical current densities, eddy current loss, irreversibility line, flux creep. |
