Superconducting devices have been widely studied over these years. Their application can be found in cables for electric power transmission, energy storage systems, magnetic levitation, electric machines, and fault current limiters. The literature presents some formulations to model the superconductors’ behavior using the finite element method (FEM), such as the H, the AV, and the T formulations, among others. Many superconducting devices have been simulated and designed using some of these formulations. However, none method available offers a coupling between an electric power system, simulated using electrical lumped parameters, to the superconducting FEM model. In this context, this work introduces a methodology for coupling superconducting devices in FEM to lumped parameters composing the power system. Here, a case study with a Saturated Iron Core Superconducting Fault Current Limiter was presented to apply the proposed methodology. This research analyzes the influence of the self and external fields in the superconducting coil on its critical current density. Moreover, it investigates the DC-biased coil voltage drop and the superconducting resistance. Besides, the paper presents the simulations of short circuits for various DC currents applied to the superconducting coil. Short-circuit tests were performed for validating the simulation results, and it showed a maximum error of 15% for the compared points.

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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 P , 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.

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This work presents simulation studies on superconducting jointless loops known as double crossed loop coils, made from partially slit and stacked REBCO tape segments. The objective is to investigate design parameters for a novel magnetic bearing application, trying to increase the (levitation force)/(tape length) ratio. The adopted simulation strategy is to model the tapes as one-dimensional current sheets with the current density written as integral equations solved by finite elements. For this recently developed type of coil, each current path must be modeled, thus every tape should be represented in the simulation, as shall be discussed. The results demonstrate how the coils’ performance varies non-linearly to the geometric parameters and that stacking the maximum number of tapes is not the only way to increase the levitation force. Their force curves also do not show the same behavior as expected for bulk ones, and an analysis is performed to relate it to the critical current sensitivity to the magnetic field. A more detailed investigation explains this behavior from the induced currents’ point of view in every loop of the stack. Comparisons between the simulation data and prototype tests prove that the chosen model can satisfactorily reproduce the measurements.