Gives introductory remarks about chapter 1 of this group of 31 papers, from ISEF 1999 Proceedings, in the methodologies for field analysis, in the electromagnetic community…
Abstract
Gives introductory remarks about chapter 1 of this group of 31 papers, from ISEF 1999 Proceedings, in the methodologies for field analysis, in the electromagnetic community. Observes that computer package implementation theory contributes to clarification. Discusses the areas covered by some of the papers ‐ such as artificial intelligence using fuzzy logic. Includes applications such as permanent magnets and looks at eddy current problems. States the finite element method is currently the most popular method used for field computation. Closes by pointing out the amalgam of topics.
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P. Dular, C. Geuzaine, M.V. Ferreira da Luz, N. Sadowski and J.P.A. Bastos
Connection boundary conditions are studied with the finite element method using different types of mixed finite elements, i.e. nodal, edge and facet elements of different shapes…
Abstract
Connection boundary conditions are studied with the finite element method using different types of mixed finite elements, i.e. nodal, edge and facet elements of different shapes and degrees, used in both b‐ and h‐conform formulations. The developed associated tools are first applied to periodicity boundary conditions before being applied to the treatment of the moving band in 2D and 3D. This step by step approach enables their validation before pointing out the effect of the considered elements on the accuracy of the moving band method. A special attention is given to the consistency of these boundary conditions with gauge conditions and source magnetic fields.
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Discusses some general algorithmic problems encountered when solving linear systems in electromagnetism, such as, e.g. the well‐known difficulties linked with the curl‐curl…
Abstract
Discusses some general algorithmic problems encountered when solving linear systems in electromagnetism, such as, e.g. the well‐known difficulties linked with the curl‐curl operator in discrete form. The problem is examined as part of a larger one: solving “mixed” (or as we prefer to say, “constrained”) linear systems, with Lagrange multipliers, for which available strategies are reviewed. It is shown that dealing with the mixed system directly, without first getting rid of multipliers, can be a viable proposition.
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In the applications of FEM. a compromise between the accuracy and the computation cost is often required, especially when 3D cases are concerned Adaptive mesh refinement is a good…
Abstract
In the applications of FEM. a compromise between the accuracy and the computation cost is often required, especially when 3D cases are concerned Adaptive mesh refinement is a good answer to this demand.
Daniel Klis, Stefan Burgard, Ortwin Farle and Romanus Dyczij-Edlinger
– The purpose of this paper is to determine the broadband frequency response of the impedance matrix of wireless power transfer (WPT) systems comprising litz wire coils.
Abstract
Purpose
The purpose of this paper is to determine the broadband frequency response of the impedance matrix of wireless power transfer (WPT) systems comprising litz wire coils.
Design/methodology/approach
A finite-element (FE)-based method is proposed which treats the microstructure of litz wires by an auxiliary cell problem. In the macroscopic model, litz wires are represented by a block with a homogeneous, artificial material whose properties are derived from the cell problem. As the frequency characteristics of the material closely resemble a Debye relaxation, it is possible to convert the macroscopic model to polynomial form, which enables the application of model reduction techniques of moment-matching type.
Findings
FE-based model-order reduction using litz wire homogenization provides an efficient approach to the broadband analysis of WPT systems. The error of the reduced-order model (ROM) is comparable to that of the underlying original model and can be controlled by varying the ROM dimension.
Research limitations/implications
Since the present model does not account for displacement currents, the operating frequency of the system must lie well below its first self-resonance frequency.
Practical implications
The proposed method is well-suited for the computer-aided design of WPT systems. It outperforms traditional FE analysis in computational efficiency.
Originality/value
The presented homogenization method employs a new formulation for the cell problem which combines the benefits of several existing approaches. Its incorporation into an order-reduction method enables the fast computation of broadband frequency sweeps.
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Olivier Barre and Pascal Brochet
The purpose of this paper is to introduce a simplified method to calculate an estimation of local forces acting on a body submitted to electric or magnetic fields. With…
Abstract
Purpose
The purpose of this paper is to introduce a simplified method to calculate an estimation of local forces acting on a body submitted to electric or magnetic fields. With experimentations, the method is thereafter evaluated.
Design/methodology/approach
When an external strength exists on a body, its deformation is an effect always observed. With materials with low elasticity modulus, such a deformation becomes visible and its measurement can be used to validate numerical simulations. Using similarities between electric and magnetic behaviour laws, magnetic problems can be modelled with an electric field approach and studied with an experiment that also uses an electric field.
Findings
Geometrical singularities and their effects on calculations are not always well taken into account by a finite element resolution. An adaptive mesh refinement is often required. If such mesh refinement is refused, another solution can be explored. The goal is to know the external stress distribution induced by the field. The methods only focus on this stress distribution and assume that the magnetic or electric field distribution is imprecise when it is calculated near geometrical singularities. The stress distributions suggested are verified with experiments.
Originality/value
Using new materials with particular physical properties provides a new concept of experimental validation.
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Gérard Meunier, Christophe Guérin, Vincent Charmoille and Patrice Labie
The purpose of this paper is to propose a general approach for the frequency‐domain homogenization of electromagnetic periodic structures. The method allows calculating…
Abstract
Purpose
The purpose of this paper is to propose a general approach for the frequency‐domain homogenization of electromagnetic periodic structures. The method allows calculating macroscopic equivalent properties including local effects. It is based on the equivalence of active and reactive electromagnetic powers on an elementary cell. This work is applied to the modelling of eddy current losses in windings, by the use of the finite element method in 2D and 3D.
Design/methodology/approach
The approach is based on an homogenization technique, allowing describing local properties (permeability and conductivity) and local effects (eddy currents) of periodical structures, through macroscopic homogenized behaviour laws.
Findings
It was found that the presence of local loops of eddy currents at the local scale implies that the average values of the electric and magnetic field are different from the macroscopic fields. This implies some precautions to implement the homogenization. Furthermore, the question of the coupling of the macroscopic laws has been clarified.
Research limitations/implications
The proposed method is limited to the frequency domain. Some additional work is necessary to extend the researches in the time domain.
Practical implications
The proposed methodology is applied for determining losses in coils with the finite element method. The major interest of the method is that it allows taking into account local effects (losses in particular), with a reduced computational time.
Originality/value
The method proposed in this paper is general and clarifies the principle of homogenization in the case of periodical structure in presence of local eddy currents (local loops of current).
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Rafal M. Wojciechowski, Andrzej Demenko and Jan K. Sykulski
The purpose of this paper is to develop a reluctance‐resistance network (RRN) formulation for determining the induced current distributions in a 3D space of multiply connected…
Abstract
Purpose
The purpose of this paper is to develop a reluctance‐resistance network (RRN) formulation for determining the induced current distributions in a 3D space of multiply connected conducting systems.
Design/methodology/approach
The proposed RRN method has been applied to solve Problem No. 7 of the International TEAM Workshops. The induced currents in the conductive plate with an asymmetrically situated “hole” have been analysed. The RRN equations have been formed by means of the finite element method using the magnetic vector potential A and the electric vector potentials T and T0. The block relaxation method combined with the Cholesky decomposition procedure has been applied to solve the resultant RRN equations.
Findings
Comparison with results published in literature has demonstrated high accuracy of the proposed RRN computational scheme while offering significant savings in computing times.
Originality/value
A novel formulation of the RRN approach has been proposed and demonstrated to be computationally efficient.
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Leysmir Adriana Millan Mirabal, Oualid Messal, Abdelkader Benabou, Yvonnick Le Menach, Loic Chevallier, Jean-Yves Roger and Jean-Pierre Ducreux
The purpose of this study is to explore the effect of the demagnetizing field in the Epstein characterization of grain-oriented electrical steels through a finite element method…
Abstract
Purpose
The purpose of this study is to explore the effect of the demagnetizing field in the Epstein characterization of grain-oriented electrical steels through a finite element method (FEM) simulations.
Design/methodology/approach
A 3D finite element simulation has been realized to represent the parallel and X-stacking configurations in the Epstein frame. The numerical results have been compared with experimental measures.
Findings
In a parallel configuration, the measured induction is actually the one in the material, whereas the resulting magnetic field differs from the applied one (in magnitude and angle) due to the shape anisotropy (demagnetizing field). In X-stacking configuration, the resulting magnetic field is close to the applied magnetic field (and then the supposed excitation field in the Epstein frame), whereas the magnetic induction has deviated from the axis of the strips.
Originality/value
Both stacking configurations (parallel and cross) of the Epstein frame are analyzed by three-dimensional finite element simulation.
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József Pávo´, Imre Sebestyén, Szabolcs Gyimóthy and Oszkár Bíró
Three methods are presented for the approximate prediction of losses in laminated transformer cores. The input data of the calculations are the field distribution obtained by a…
Abstract
Three methods are presented for the approximate prediction of losses in laminated transformer cores. The input data of the calculations are the field distribution obtained by a FEM code assuming the laminated core as a homogeneous medium that conductivity is zero in the direction perpendicular to the lamination. These data are processed by the developed methods to obtain an agreeable approximation of the power losses in the transformer plate. For each approach the same benchmark problem is solved to exploit the properties of the approaches. The goal of the presented study is to select the most suitable method that can be used as a postprocessor of a FEM code.