Speaker
Description
The increasing use of Rare-earth barium copper oxide (REBCO) bulks in electromechanical applications, particularly for acting as “pseudo” permanent magnets, is driving the development of more sophisticated numerical models. The focus has been on modeling electromagnetic phenomena with greater accuracy and efficiency, taking into account the non-linear and heterogeneous characteristics of high temperature superconductor (HTS) bulks. The issue of dealing with HTS bulks is their non-isotropic nature and the inhomogeneity inherent to the fabrication process, which leads to the formation of pores, grain boundaries and defects such as cracks that can affect their magnetization. In the present work, two incremental modified mixed formulations, $\varphi$-$\textbf{H}$-$\phi$ and $\varphi$-$\textbf{J}$-$\textbf{A}$-$\phi$, are proposed in conjunction with the finite element method (FEM) to reduce the computational burden in 3D thermo-electromagnetic transient simulations of pulsed field magnetization of porous HTS bulks. The idea is to find the formulation of the Maxwell equations that leads to the fastest computational time in order to generate enough numerical results for statistical analysis in the future. In the proposed scheme, the heat balance equation is coupled to the electromagnetic physics in the COMSOL Multiphysics® software. The trapped field results for both the $\varphi$-$\textbf{H}$-$\phi$ and $\varphi$-$\textbf{J}$-$\textbf{A}$-$\phi$ 3D FEM models are cross-checked with the respective results obtained with using the more classical $\textbf{H}$, $\textbf{H}$-$\phi$ and $\textbf{J}$-$\textbf{A}$ FEMs. A validation is provided using experimental data from the literature. The $\varphi$-$\textbf{H}$-$\phi$ formulation showed the fastest computation times with reasonable accuracy, making it more favorable for understanding the impact of defects in REBCO bulk on their performance.
