AC loss in a high-temperature superconducting coil

in a typical superconducting coil made of BSCCO/Ag tape, both amplitude and direction of the magnetic field determine the critical current, resistive voltage and AC loss. The distribution of the magnetic field along and acros s the superconducting tape in a coil is rather complex. This gives rise to the question: how accurate can one predict the critical current, V-I charac teristic and AC loss of the AC coil from results of short sample measuremen ts? To answer this question, we have measured and compared the characterist ics of a short sample and a small coil employing similar to 14 m of the sam e tape at 77 K. The comparison is performed as follows. First, a short samp le is characterised with regard to the field dependence of the critical cur rent. V-I characteristic and the AC loss. Second, the distribution of the m agnetic field along the tape in a coil is accurately calculated. From the d ata, the voltage along the tape and the loss of the tape in the coil are fo und. Finally, the resistive voltage and the AC loss of the complete coil ar e calculated and compared to measured AC losses in the frequency range of 0 to 160 Hz, typical for power applications. (C) 1998 Elsevier Science B.V. All rights reserved.