AC losses in HTSC bulk and tapes: A review

After the advent of high temperature superconductors (HTSC), much research and development have been carried out and currently these materials are on the verge of being used in the power engineering applications at a commercial scale. In such applications, the ac losses of superconductors are regarded as one of the most important design parameters that guide the fabrication of the devices. There are different methods for the determination of such losses. This article describes some of the widely used methods and discusses the results on the ac losses of bulk HTSC compounds and single and multifilamentary tapes. The nature and origin of the losses in these materials and their dependence on various physical entities like applied field, frequency, and temperature have also been dealt with in detail. Gap areas have also been identified in which further research is needed in order to facilitate the design and fabrication of commercially usable devices with superior performance.