Development of an edge-element model for AC loss computation of high-temperature superconductors

Abstract

This paper presents a new numerical model for computing the current density, field distributions and AC losses in superconductors. The model, based on the direct magnetic field H formulation without the use of vector and scalar potentials (which are used in conventional formulations), relies on first-order edge finite elements. These elements are by construction curl conforming and therefore suitable to satisfy the continuity of the tangential component of magnetic field across adjacent elements, with no need for explicitly imposing the condition . This allows the overcoming of one of the major problems of standard nodal elements with potential formulation: in the case of strong discontinuities or nonlinearities of the physical properties of the materials and/or in presence of sharp corners in the conductors’ geometry, the discontinuities of the potentials’ derivatives are unnatural and without smoothing artifices the convergence of the algorithm is put at risk. In this work we present in detail the model for two-dimensional geometries and we test it by comparing the numerical results with the predictions of analytical solutions for simple geometries. We use it successively for investigating cases of practical interest involving more complex configurations, where the interaction between adjacent tapes is important. In particular we discuss the results of AC losses in superconducting windings.

Magneto-thermal finite element modeling of 2nd generation HTS for FCL design purposes

“…The magneto-thermal model was implemented in COMSOL Multiphysics [8], a FEM open structure software that allows great freedom to deal with partial differential equations (PDE). The electromagnetic formulation, briefly summarized here, is based on a direct use of the magnetic field H as a state variable [9]. From Faraday's law, the coupling of the magnetic and electric fields is described as…”

Electromagnetic behaviors of superconducting Nb3Sn wire under a time-dependent current injection

“…2 In recent years, attempts have been made to study the electromagnetic behaviors of some superconductors by numerical simulation. [3][4][5][6][7][8][9][10][11][12][13][14][15][16] As for finite element modelling (FEM), the extreme complexity of hierarchical geometry and structure of Nb 3 Sn strand and CICC requires a special concern for the modelling of the strand entity. Therefore this will inevitably consume large amounts of CPU time and memory capacity in meshing and calculating process.…”

“…So, 2D simulations mainly focus on high-temperature superconductors (HTS) with homogenous material and standard bulk shape. 3,4,6,[8][9][10][11][13][14][15] As the advance of computer technology, it becomes feasible to use FEM to cope with Nb 3 Sn strand at the cost of long-time computation and large memory. Even so, modelling the strand down to filament level is still troublesome.…”

The BEST PATHS Project on MgB2Superconducting Cables for Very High Power Transmission

“…The latter are a common consequence of the AC/DC rectification process. In order to perform these investigations, a numerical model solving the time-dependent Maxwell's equations using the finite-element method will be employed [16]. The model is able to reproduce the precise geometry of the MgB 2 wire and incorporates highly non-linear characteristics of the materials composing the cable, such as non-linear magnetic permeability for nickel and monel and a power-law electrical resistivity for the superconductor.…”