Energy dissipation in high temperature ceramic superconductors

Losses in high-T-c superconductors are of vital importance in practical applications. The mechanisms are similar to those in low-T-c materials but there are a number of complications. In this paper the loss mechanisms in different regimes are summarized and simple approximate expressions obtained. Losses due to the transport current are analysed with the theory of Norris for elliptical conductors. This predicts different loss voltages according to where the voltage contacts are placed on the conductor which has been confirmed experimentally. This poses difficulties in turning experimental data into reliable loss measurements, but a series of experiments with different contact layouts and phase setting techniques is found to give consistent results, in good agreement with theory.