I. Introduction
The Total ac losses at power frequencies of superconductors in the presence of an ac magnetic field, an ac transport current, a dc background field, and various combinations of these have been measured [1]–[5]. For the most part, however, these losses have been determined on short pieces of tape, and assumptions have been made about how these measurements can predict the ac losses in working devices. Variations in high-temperature superconductor (HTS) tape quality, and parameters such as the critical current, the exponent value, the overall tape dimensions, the core dimensions, and the filament dimensions and arrangement can affect the way each tape behaves. Damage during coil winding procedures can also affect the ac loss.
Overall schematic of the MBC.
Hence, the net ac loss of a significant length of tape will be substantially different from that predicted by measurements on a few centimeters of tape. The degree of difference may be used as a benchmark as to the quality of the manufacturing route and the consistency of the physical and electrical properties across a length of tape. In addition, the complexity of interpreting the electrical signals from ac loss measurements for a device has led researchers to pursue other methods of characterizing the ac losses of coils and devices [4], [5].