AC loss in superconducting tapes and cables

The present study discusses the AC loss in high-temperature superconductors. Superconducting materials with a relatively high critical temperature were discovered in 1986. They are presently developed for use in large-scale power-engineering devices such as power-transmission cables, transformers and electric motors. The alternating magnetic field in these devices causes energy dissipation (AC loss) despite the zero resistance of the superconductor in stationary circumstances. The dissipated heat must be removed from the low-temperature environment by a refrigerator, whose power consumption is 10-20 times the AC loss. The study is intended to ascertain whether high-temperature superconductors can be produced with an AC loss low enough to compete with copper. The study focuses on the material Bi-2223, which is presently produced in the form of long flexible tapes, comprising thin superconducting filaments embedded in a silver matrix. The AC loss is measured by magnetic, electric and calorimetric methods, which are adapted for the investigation of hightemperature superconducting tapes.