AC losses in multifilamentary Bi-2223/Ag tapes subjected to bending strains

Abstract

Electrical power devices, e.g. motors, power transmission cables, transformers, etc. are the most promising, and nowadays the most technologically advanced, applications of high temperature superconductors (HTS). Multifilamentary HTS tapes (usually Bi-2223/Ag composites) are used in forms of various in shape coils, therefore are subjected to different kinds of mechanical stresses. This leads to some changes in physical parameters of superconducting material, mainly in the critical current density, and thus in the dissipated electromagnetic energy. In general, when a superconductor is carrying an AC transport current and simultaneously subjected to an external AC magnetic field, the total dissipated energy can be considered as a sum of components, the transport loss and the magnetization loss. In this work we report some experimental results related to the total AC loss characteristics of Bi-2223 tapes and their dependencies on bending strains. An external magnetic field, in phase with an AC transport current, was directed parallel to the wider surfaces of the samples. The total AC losses in the Bi-2223/Ag tapes were measured by means of a calorimetric method. Obtained experimental data are compared with the critical state model predictions for total losses behavior in presented here experimental conditions.