Using the integral equations method to model a 2G racetrack coil with anisotropic critical current dependence. (4th October 2017)

• Record Type: Journal Article
• Authors: Martins, F G R; Sass, F; Barusco, P; Ferreira, A C; de Andrade, R
• Is Part Of: Superconductor science & technology. Volume 30:Number 11(2017:Nov.)
• Publication Date: 2017-10-04
• Subjects: HTS coils -- simulation -- critical current -- 2G tapes; Superconductivity -- Periodicals; Superconductors -- Periodicals; 537.623
• DOI: 10.1088/1361-6668/aa892b
• Languages: English
• ISSNs: 0953-2048

Abstract

Abstract: Second-generation (2G) superconducting wires have already proved their potential in several applications. These materials have a highly nonlinear behavior that turns an optimized engineering project into a challenge. Between several numerical techniques that can be used to perform this task, the integral equations (IE) method stands out for avoiding mesh problems by representing the 2G wire cross-sectional area by a line. While most applications need to be represented in a 3D geometry, the IE is limited to longitudinal or axisymmetric models. This work demonstrates that a complex 3D geometry can be modeled by several coupled simulations using the IE method. In order to prove this statement, the proposed technique was used to simulate a 2G racetrack coil considering the self-field magnitude (B) and incidence angle ( θ ) on the tape. The J c characteristic was modeled in terms of parallel and normal to the tape plane magnetic field components ( J c ( B ∥, B ⊥ )) obtained from a V – I ( B, θ ) characterization of a tape segment. This result was implemented using commercial software with both A – V (vector magnetic potential and scalar voltage potential) and IE coupled simulations solved by finite elements. This solution bypasses the meshing problem due to the tapes slim geometry, considering each turn a single 1D model, all magnetically interacting in two 2D models. The simulations results are in good agreement to what was both expected and observed in the literature. The simulation is compared to the measured V – I characteristic for a single pancake racetrack coil built with same geometry as its simulation models, and a theoretical study demonstrates the possibilities of the proposed tool for analyzing a racetrack coil current density and electric field behavior in each of its turns.