H-Formulation FEM Modeling of the Current Distribution in 2G HTS Tapes and Its Experimental Validation Using Hall Probe Mapping

Abstract

One of the most widespread mathematical formulations applied to simulate the electromagnetic phenomena of coated conductor in the recent literature is the H one. However, the only validation of the model has been indirect by using measurements taken from the applications, as measurements of the energy losses in ac fields, forces developed in levitation systems or any other parameter related to a specific application. Direct validation of the calculation requires the observation of the local out of plane magnetic field over the surface of the sample and this is only accessible under magneto-optical observations and, in a larger scale and better dynamic range, by the Hall scanning microscopy. We propose here the experimental validation of the H-formulation by comparing the simulated results with measurements made by a Hall probe mapping in a second generation (2G) tape sample for several DC transported currents at 77 K. The paper presents a methodology to simulate the 2G tape by using only measured data obtained from a sample and its normalized J(B) experimental curves. Some boundary conditions that allow a faster convergence of the problem are investigated. Simulated results of the 2G tape modelled considering only the 1 μm HTS layer were compared with other that represent the most important layers of the coated conductor structure in the calculations. The simulated and measured results present a good agreement, proving that this model can calculate precisely the magnetic field and, hence, the current distribution in HTS samples.

This work was supported in part by the followings grants: “Science Without Borders” from the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); by the European Agency (EU) through the Factories of the Future Resources, Technology, Infrastructure and Services for Simulation and Modelling (FORTISSIMO) Project under Grant EU FP7-2013-ICT-609029, the European Development of Superconducting Tapes (EUROTAPES) Project under Grant EU-FP7 NMP-LA-2012- 280432, the European Consortium for the Development of Fusion Energy (EUROfusion, PPPT-WPMAG 2014), and EU COST ACTIONS MP1201 and MP1014; by the Spanish Ministry of Economy and Competitiveness through the “Severo Ochoa” Programme for Centres of Excellence in R&D under Grant SEV-2015-0496, CONSOLIDER Excellence Network under Grant MAT2015- 68994-REDC, COACHSUPENERGY project under Grant MAT2014-56063- C2-1-R, co-financed by the European Regional Development Fund; by the Catalan Government under Grant 2014-SGR-753 and Xarmae.