The study of the stability process of MgB 2 superconducting wires and coils is an important issue in the design and feasibility of electric power applications. In this sense, the thermal conductivity plays an important role, which in composite wires and tapes is mainly determined by the amount of stabilizer (usually copper), the configuration of filaments and the metallic matrix; while for coils, the winding, wire electric insulation
Abstract:The thermal stability of superconducting YBCO coated conductors subject to over-currents are analysed. We have studied the effect of DC and AC over-current pulses in Cu-stabilized and non-stabilized coated conductors by measuring the electric field and temperature profiles of these conductors immersed in liquid nitrogen. Current pulses of short duration of about 90 ms and long duration of a few seconds were applied to the samples. Three different cooling regimes of the liquid nitrogen: convection, nucleate boiling and film boiling were observed, and their influence in the recovery time of superconductivity in the coated conductors after the over-current pulses has been analysed. We have studied the recovery behaviour under two different conditions, in which the current was set to zero and to the operating current after the current pulses.These experiments simulated the conditions during an over-current situation in different electric power applications with special attention given to the behaviour of these coated conductors acting as in fault current limiters.2
Abstract-Roebel cable with 2G YBCO strands is one of the promising HTS solutions of fully transposed high current conductors for high field accelerator magnets. Following the considerable research effort on the manufacturing of Roebel cables in recent years, sample conductors are now available in useful lengths with reproducible performances to allow detailed characterizations beyond the standard critical current measurements. The ac loss and strands coupling are of significant interest for the field quality of the accelerator magnets. We report a set of systematic ac loss measurements on two different Roebel cable samples prepared for the EuCARD2 collaboration. The measurements were performed over a wide range of temperature between 5 K and 90 K and the results were analyzed in the context of strands architecture and coupling. The results show that the transposed bundles are partially decoupled and the strands in transposition sections behave as an isolated single tape if the strands are insulated.
The process of quench development in a single conductor, e.g., in a high temperature superconducting tape, is governed by its physical properties. In a superconducting magnet coil the addition of insulating materials and the way in which the coils are thermally anchored also play an important role in the thermal stability and quench behavior of the system. Previous quench modeling works using commercial software are mostly based on anisotropic continuum medium approximation, where the coil is considered as an effective media representing the average physical properties of the individual layers. While such models allow the reduction of model size with symmetry considerations, they become invalid for small insert coils or for conductors with a high proportion of stabilizer. In addition they cannot be integrated with thermal, mechanical and electromagnetic multiphysics where the discrete winding structure is relevant. The present work describes a parametrically-generated, 3-D model with full representation of the winding structure of the superconducting coil. The geometric generation of the model allows easy meshing of the whole coil, including the insulation. The application cases and limitations of this model are discussed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.