Publications de Bertrand Dutoit

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The ac loss of superconducting composite depends strongly on coupling between superconducting filaments via the resistive matrix. The established technique for loss reduction using twisted filaments relies on the decoupling of the filaments below a critical coupling field Bc, which increases with the reduction of the twist pitch and the matrix conductivity. Although the concept of Bc may be clearly demonstrated using two infinite slabs of finite length, further details on its correlation with the filament/c

Hadron and proton therapy are cutting edge techniques for cancer treatment and a great development of specialized medical centers and research facilities is foreseen in the next decades. One of the main obstacles to the penetration of the use of charged pa ...

High-temperature superconductors (HTS) exhibit hysteresis, which is the main cause for losses in the subcritical domain. This behavior is well predicted by Bean's critical-state model, which is a subset of the classical Preisach model. We present a paramet ...

The semi-analytical method (SAM) is a fast integral technique for solving small 2-D, time-transient electromagnetic problems in high temperature superconductors (HTS) with transport current and/or applied field. The method in itself is a generalization of ...

This paper compares the speed and accuracy of two commercial packages based on the finite element method (FEM) for calculating the AC losses in high temperature superconductors (HTS). The softwares investigated in this paper were COMSOL Multiphysics and FL ...

In certain power applications, Bi-2223 conductors carrying AC current will be subjected to external magnetic fields, whose orientation and conductor’s geometry are of major significance for the AC loss magnitude. This paper investigates the influence of the geometry and aspect ratio of non-twisted Bi-2223 conductors in reducing the AC loss for such applications. A numerical model of high-Tc materials has been used in FEM simulations. The model incorporates power-law E-J characteristics with Jc defined by bo

In typical power applications, Bi-2223 conductors carrying ac current will be subjected to external magnetic fields, whose orientation and conductor’s geometry are of major significance for the ac loss magnitude. This paper investigates the influence of the geometry and aspect ratio of non-twisted Bi-2223 conductors in reducing the ac loss for such applications. A numerical model of high-Tc materials has been used in finite-element-method simulations. The model incorporates power-law E-J characteristics wit

High-temperature superconductors (HTS) can be superconducting in liquid nitrogen (77 K) at atmospheric pressure, which holds immense promises for our future such as nuclear fusion, compact medical devices and efficient power applications. In a power system ...

The resolution of the magneto-optical technique to observe directly the structure of the intermediate state in superconductors has been considerably improved by the replacement of EuS–EuF2 mixture by EuSe thin films with higher specific Faraday rotation. T ...

A Mach-Zehnder Interferometer (MZI) based optical fibre sensing technique, developed and patented by EPFL, is an efficient and economical way to detect hotspots in High Temperature Superconductor (HTS) applications. Due to the MZI sensitivity being a compo ...

For describing the E-J relation of high-Tc superconductors (HTS) in power applications, where the applied current I is generally limited by Ic, the critical state model, a piecewise linear generalization, or a simple power-law of the type E=Ec(J/Jc)^n are most often used. The power-law cannot be used for modelling the E-J relation with I>>I_c due to the unbound exponential increase of the electric field for currents above Ic, while in reality the non-linear HTS resistivity is limited by its normal state val

The major drawback for the commercialization of fault current limiter (FCL) made of YBCO on sapphire is their expensive price. In the recent years, coated conductors (CC) have been extensively developed and, due to their lower prices, have been recently te ...

Due to the energy demand growth and distributed generation (DG) units penetration, a substantial increase of the rated short-circuit current of the electrical lines is expected. As a consequence, the electrical grid infrastructure needs to be extended or d ...

A 3D numerical modelling technique for solving problems involving superconducting materials is presented. The model is implemented in finite element method software and is based on a recently developed 3D formulation for general electro-magnetic problems with solid conductors. It has been adapted for modelling of superconductors with non-linear resistivity in 3D, characterized by a power-law E-J relation. It has firstly been compared with an existing and verified 2D model: compared are the current density d

The health monitoring of superconducting fault current limiters (SFCL) is important for their large-scale exploitation in HVDC grids protection. The intrinsic non-homogeneity of critical current along the superconductor length can cause localized points of ...

In this paper the effects of the magnetic self-field on the transport properties of a multi-layer high-Tc superconducting (HTS) cable are investigated by means of 2D finite element method (FEM) simulations. Analyzed is a 3-layer HTS cable, but the developed methods can be used for a different number of layers. The superconductor is described by the non-linear power-law relation E=Ec(J/Jc)^n, where the parameters Jc and n depend on the magnetic field experienced by the material. This dependence decreases the

The nonlinear behavior of High Temperature Superconductors (HTS) is often modeled by an E-J power law in order to describe their electromagnetic properties. This paper presents AC loss calculations in HTS tapes, performed by means of FEM commercial software using the A-V method. The implemented nonlinear model of the HTS tapes takes into account the B-dependence of the critical current density Jc and the power index n. The expressions for Jc(B) and n(B) are obtained from electrical measurements of a Bi-2223

Thin films are very promising for the design of novel and efficient Fault Current Limiter (FCL) made of high-temperature superconductors (HTS). However, their thermal and highly non-linear electromagnetic behavior in the presence of over-critical currents is crucial to their use in future electrical grid. In this paper, we propose a numerical approach to solve magneto-thermal models for geometries of high aspect ratio. The used electromagnetic formulation, inspired in good part from the work of Brambilla et

The AC loss performance of two BSCCO and two YBCO conductors of different geometry, characterized by the same self-field critical current of 150 A, is analysed and compared quantitatively. The comparison is made using the finite-element method with a non-l ...

The finite element method has been employed in order to simulate the behaviour of a HTS cable for transport current applications. The E-J model includes an anisotropic dependence of the critical current density Jc and power index n on the local magnetic field, whose magnitude is non-negligible and determines the effective critical current of the cable. The cable consists of four electrically insulated layers, each of them composed by 20 superconducting tapes, providing a total critical current of about 4 kA

Bertrand Dutoit

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3D Modeling of Coupling Between Superconducting Filaments via Resistive Matrix in AC Magnetic Field

Magnetic Design of a Superconducting Toroidal Gantry for Hadron Therapy

Parameterized hysteresis model for high-temperature superconductors

Assessment of the Computational Performances of the Semi-Analytical Method (SAM) for Computing 2-D Current distributions in Superconductors

Evaluation of two commercial finite element packages for calculating AC losses in 2-D high temperature superconducting strips

Geometry considerations for transport current applications of Bi-2223 conductors with anisotropic Jc(B) in external magnetic field

Geometry considerations for use of Bi-2223/Ag tapes and wires with different models of Jc(B)

Superconductors for power applications: an executable and web application to learn about resistive fault current limiters

Use of europium selenide films for magneto-optical studies at low temperatures

Optical fibre based quench detection in HTS applications using machine learning classifiers

Modelling the E-J relation of high-Tc superconductors in an arbitrary current range

Comparison Between the Behavior of HTS Thin Film Grown on Sapphire and Coated Conductors for Fault Current Limiter Applications

MV Power Grids Integration of a Resistive Fault Current Limiter Based on HTS-CCs

Finite Element Method Modelling of Superconductors: from 2D to 3D

Optical fibre sensing for fast hotspot detection in SFCLs

Numerical Analysis of the Effects of the Magnetic Self-Field on the Transport Properties of a Multilayer HTS Cable

Finite element method simulation of ac loss in HTS tapes with B-dependent E-J power law

2D Magneto-Thermal Modeling of Coated High-Temperature Superconductors

Finite-element analysis and comparison of the AC loss performance of BSCCO and YBCO conductors

Numerical Modelling of a HTS Cable