AC losses in a type II superconductor strip with inhomogeneous critical current distribution

Abstract

Analytical formulae derived by Brandt and Indenbom (1993 Phys. Rev. B 48 12893–906) and Norris (1970 J. Phys. D: Appl. Phys. 3 489–507) are often used to calculate the magnetization and AC transport current losses in HTS strip conductors, respectively. In these formulae, homogeneous distribution of critical sheet current density σc in the strip is assumed. However, it is considered that σc distributions are inhomogeneous in actual HTS strips and that the inhomogeneous σc distributions cause deviations of the measured AC loss data of actual HTS strips from those formulae. A semi-analytical method to calculate AC transport current and magnetization losses is derived for a type II superconductor strip with inhomogeneous distribution of σc in the direction of the strip width. The method is derived modifying the analysis of Brandt et al. The validity of the semi-analytical method is shown by comparing the results calculated by this method with those calculated by the Norris and Brandt formulae and by a different method of our previous work and also with experimental data. Moreover, it is shown that the deviation of the measured data from the Norris and Brandt models can be estimated by assuming proper σc distributions.