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Correction of homogenized lamination stacks via a subproblem finite element method Dular, Patrick ; ; et al in COMPEL (2015), 34(5), 1553-1563 Purpose – The purpose of this paper is to develop a subproblem finite element method for progressive modeling of lamination stacks in magnetic cores, from homogenized solutions up to accurate eddy current ... [more ▼] Purpose – The purpose of this paper is to develop a subproblem finite element method for progressive modeling of lamination stacks in magnetic cores, from homogenized solutions up to accurate eddy current distributions and losses. Design/methodology/approach – The homogenization of lamination stacks, subject to both longitudinal and transversal magnetic fluxes, is first performed and is followed by local correction subproblems in certain laminations separately, surrounded by their insulating layers and the remaining laminations kept homogenized. The sources for the local corrections are originally defined via interface conditions to allow the coupling between homogenized and non-homogenized portions. Findings – The errors proper to the homogenization model, which neglects fringing effects, can be locally corrected in some selected portions via local eddy current subproblems considering the actual geometries and properties of the related laminations. The fineness of the mesh can thus be concentrated in these portions, while keeping a coupling with the rest of the laminations kept homogenized. Research limitations/implications – The method has been tested on a 2D case having linear material properties. It is however directly applicable in 3D. Its extension to the time domain with non-linear properties will be done. Originality/value – The resulting subproblem method allows accurate and efficient calculations of eddy current losses in lamination stacks, which is generally unfeasible for real applications with a single problem approach. The accuracy and efficiency are obtained thanks to a proper refined mesh for each subproblem and the reuse of previous solutions to be locally corrected only acting in interface conditions. Corrections are progressively obtained up to accurate eddy current distributions in the laminations, allowing to improve the resulting global quantities: the Joule losses in the laminations, and the resistances and inductances of the surrounding windings. [less ▲] Detailed reference viewed: 19 (1 ULg)Progressive inductor modeling via a finite element subproblem method Dular, Patrick ; ; et al in COMPEL (2015), 34(3), 851-863 Purpose – The purpose of this paper is to develop a subproblem method (SPM) for progressive modeling of inductors, with model refinements of both source conductors and magnetic cores. Design/methodology ... [more ▼] Purpose – The purpose of this paper is to develop a subproblem method (SPM) for progressive modeling of inductors, with model refinements of both source conductors and magnetic cores. Design/methodology/approach – The modeling of inductors is split into a sequence of progressive finite element (FE) SPs. The source fields (SFs) generated by the source conductors alone are calculated at first via either the Biot-Savart (BS) law or FEs. With a novel general way to define the SFs via interface conditions (ICs), to lighten their evaluation process, the associated reaction fields for each added or modified region, mainly the magnetic cores, and in return for the source conductor regions themselves when massive, are then calculated with FE models. Changes of magnetic regions go from perfect magnetic properties up to volume linear and nonlinear properties, and from statics to dynamics. Findings – For any added or modified region, the novel proposed ICs to define the SFs appear of general usefulness, which opens the method to a wide range of model improvements. Originality/value – The resulting SPM allows efficient solving of parameterized analyses thanks to a proper mesh for each SP and the reuse of previous solutions to be locally corrected, in association with novel SF ICs that strongly lighten the quantity of BS evaluations. Significant corrections are progressively obtained for the fields, up to nonlinear magnetic core properties and skin and proximity effects in conductors, and for the related inductances and resistances. [less ▲] Detailed reference viewed: 21 (2 ULg)A non-destructive testing application solved with A-X geometric eddy-current formulation ; Dular, Patrick ; et al in COMPEL (2010), 29(6), 1606-1615 Purpose – The purpose of this paper is to introduce a perturbation method for the A-X geometric formulation to solve eddy-current problems and apply it to the feasibility design of a non-destructive ... [more ▼] Purpose – The purpose of this paper is to introduce a perturbation method for the A-X geometric formulation to solve eddy-current problems and apply it to the feasibility design of a non-destructive evaluation device suitable to detect long-longitudinal volumetric flaws in hot steel bars. Design/methodology/approach – The effect of the flaw is accurately and efficiently computed by solving an eddy-current problem over an hexahedral grid which gives directly the perturbation due to the flaw with respect to the unperturbed configuration. Findings – The perturbation method, reducing the cancelation error, produces accurate results also for small variations between the solutions obtained in the perturbed and unperturbed configurations. This is especially required when the tool is used as a forward solver for an inverse problem. The method yields also to a considerable speedup: the mesh used in the perturbed problem can in fact be reduced at a small fraction of the initial mesh, considering only a limited region surrounding the flaw in which the mesh can be refined. Moreover, the full three-dimensional unperturbed problem does not need to be solved, since the source term for computing the perturbation is evaluated by solving a two-dimensional flawless configuration having revolution symmetry. Originality/value – A perturbation method for the A-X geometric formulation to solve eddy-current problems has been introduced. The advantages of the perturbation method for non-destructive testing applications have been described. [less ▲] Detailed reference viewed: 15 (1 ULg)Finite-Element Analysis of a Shielded Pulsed-Current Induction Heater -- Experimental Validation of a Time-Domain Thin-Shell Approach V Sabariego, Ruth ; ; et al in COMPEL (2010), 29(6), 1585-1595 Purpose – The aim of this paper is the experimental validation of an original time-domain thin-shell formulation. The numerical results of a three-dimensional thin-shell model are compared with the ... [more ▼] Purpose – The aim of this paper is the experimental validation of an original time-domain thin-shell formulation. The numerical results of a three-dimensional thin-shell model are compared with the measurements performed on a heating device at different working frequencies. Design/methodology/approach – A time-domain extension of the classical frequency-domain thin-shell approach is used for the finite-element analysis of a shielded pulse-current induction heater. The time-domain interface conditions at the shell surface are expressed in terms of the average flux density vector in the shell, as well as in terms of a limited number of higher-order components. Findings – A very good agreement between measurements and simulations is observed. A clear advantage of the proposed thin-shell approach is that the mesh of the computation domain does not depend on the working frequency anymore. It provides a good compromise between computational cost and accuracy. Indeed, adding a sufficient number of induction components, a very high accuracy can be achieved. Originality/value – The method is based on the coupling of a time-domain 1D thin-shell model with a magnetic vector potential formulation via the surface integral term. A limited number of additional unknowns for the magnetic flux density are incorporated on the shell boundary. [less ▲] Detailed reference viewed: 43 (2 ULg)Magnetic model refinement via a perturbation finite element method – from 1D to 3D Dular, Patrick ; V Sabariego, Ruth ; in COMPEL (2009), 28(4), 974-988 Purpose – The purpose of this paper is to develop a sub-domain perturbation technique for refining magnetic circuit models with finite element (FE) models of different dimensions. Design/methodology ... [more ▼] Purpose – The purpose of this paper is to develop a sub-domain perturbation technique for refining magnetic circuit models with finite element (FE) models of different dimensions. Design/methodology/approach – A simplified problem considering ideal flux tubes is first solved, as either a 1D magnetic circuit or a simplified FE problem. Its solution is then corrected via FE perturbation problems considering the actual flux tube geometry and the exterior regions, that allow first 2D and then 3D leakage fluxes. Each of these sub-problems requires an appropriate proper volume mesh, with no need of interconnection. The solutions are transferred from one problem to the other through projections of source fields between meshes. Findings – The developed perturbation FE method allows to split magnetic circuit analyses into subproblems of lower complexity with regard to meshing operations and computational aspects. A natural progression from simple to more elaborate models, from 1D to 3D geometries, is thus possible, while quantifying the gain given by each model refinement and justifying its utility. Originality/value – Approximate problems with ideal flux tubes are accurately corrected when accounting for leakage fluxes via surface sources of perturbations. The constraints involved in the subproblems are carefully defined in the resulting FE formulations, respecting their inherent strong and weak nature. As a result, an efficient and accurate computation of local fields and global quantities, i.e. flux, MMF, reluctance, is obtained. The method is naturally adapted to parameterized analyses on geometrical and material data. [less ▲] Detailed reference viewed: 32 (3 ULg)h- and b-conform finite element perturbation techniques for nondestructive eddy current testing V Sabariego, Ruth ; Dular, Patrick in COMPEL (2008), 27(1), 319-327 Purpose - The aim of the present paper is to compare the performances of a finite-element perturbation technique applied either to the h- conform magnetodynamic formulation or to its b-conform counterpart ... [more ▼] Purpose - The aim of the present paper is to compare the performances of a finite-element perturbation technique applied either to the h- conform magnetodynamic formulation or to its b-conform counterpart in the frame of nondestructive eddy-current testing problems. Design/methodology/approach - In both complementary perturbation techniques, the computation is split into a computation without defect (unperturbed problem) and a computation of the field distorsion due to its presence (perturbation problem). The unperturbed problem is conventionally solved in the complete domain. The source of the perturbation problem is then determined by the projection of the unperturbed solution in a relatively small region surrounding the defect. The discretisation of this reduced domain is chosen independently of the dimensions of the excitation probe and the specimen under study and is thus well adapted to the size of the defect. Findings - The accuracy of the perturbation model is evidenced by comparing the results of the two counterpart formulations to those achieved in the conventional way for different dimensions of the reduced domain. The size of the reduced domain increases with the size of the defect at hand. This proposed sub-domain approach eases considerably the meshing process and speeds-up the computation for different probe positions. Originality/value - At a discrete level, the impedance change due to the defect is efficiently and accurately computed by integrating only over the defect itself and a layer of elements in the reduced domain that touches its boundary. Therefore, no integration of any flux variation in the coils is required. [less ▲] Detailed reference viewed: 41 (7 ULg)Subdomain Perturbation Finite Element Method for Skin and Proximity Effects in Inductors Dular, Patrick ; V Sabariego, Ruth ; in COMPEL (2008), 27(4), 72-84 Purpose – This paper seeks to develop a sub-domain perturbation technique to efficiently calculate strong skin and proximity effects in conductors within frequency and time domain finite element (FE ... [more ▼] Purpose – This paper seeks to develop a sub-domain perturbation technique to efficiently calculate strong skin and proximity effects in conductors within frequency and time domain finite element (FE) analyses. Design/methodology/approach – A reference eddy current FE problem is first solved by considering perfect conductors. This is done via appropriate boundary conditions (BCs) on the conductors. Next the solution of the reference problem gives the source for eddy current FE perturbation sub-problems in each conductor then considered with a finite conductivity. Each of these problems requires an appropriate volume mesh of the associated conductor and its surrounding region. Findings – The skin and proximity effects in both active and passive conductors can be accurately determined in a wide frequency range, allowing for precise losses calculations in inductors as well as in external conducting pieces. Originality/value – The developed method allows one to accurately determine the current density distributions and ensuing losses in conductors of any shape, not only in the frequency domain but also in the time domain. Therefore, it extends the domain of validity and applicability of impedance-type BC techniques. It also offers an original way to uncouple FE regions that allows the solution process to be lightened, as well as efficient parameterized analyses on the signal form and the conductor characteristics. [less ▲] Detailed reference viewed: 23 (0 ULg)A finite element analysis of spatial solitons in optical fibres ; ; et al in COMPEL (2007), 26(4), 1105--1113 Detailed reference viewed: 14 (2 ULg)A perturbation finite element method for modeling moving conductive and magnetic regions without remeshing Dular, Patrick ; V Sabariego, Ruth in COMPEL (2007), 26(3), 700-711 Purpose - To develop a sub-domain perturbation technique for efficiently modeling moving systems in magnetodynamics with a magnetic field h-conform finite element (FE) formulation. Design/methodology ... [more ▼] Purpose - To develop a sub-domain perturbation technique for efficiently modeling moving systems in magnetodynamics with a magnetic field h-conform finite element (FE) formulation. Design/methodology/approach - A reference problem is first solved in a global mesh excluding some moving regions and thus avoiding the inclusion of their meshes. Its solution gives the sources for a sequence of perturbation problems with the supplementary moving magnetic and conductive regions. Each of these sub-problems requires an appropriate proper volume mesh of the associated moving region and its surrounding region, with no need of interconnection. The solutions are transferred from one problem to the other through projections of source fields between meshes. Findings - The consideration of sub-problems and associated sources, in a sequence of perturbation problems, leads to a significant speed-up of the repetitive solutions in analyses of moving systems. A free movement in any direction can be considered with no need of remeshing. Originality/value - When working with the perturbation fields, the volume sources can be limited to the moving regions, what allows for homogeneous perturbation boundary conditions and reduces the computational efforts for projecting and evaluating the sources. The curl-conformity of the unknown magnetic field is preserved during the whole process thanks to the use of edge FEs for both the magnetic field and the intermediate source quantities. The sub-problem approach also gives an easy way to directly express the time derivatives in moving frames. [less ▲] Detailed reference viewed: 30 (3 ULg)Sub-domain finite element method for efficiently considering strong skin and proximity effects Dular, Patrick ; V Sabariego, Ruth ; et al in COMPEL (2007), 26(4), 974-985 Purpose - This paper seeks to develop a sub-domain perturbation technique to efficiently calculate strong skin and proximity effects in conductors within frequency and time domain finite element (FE ... [more ▼] Purpose - This paper seeks to develop a sub-domain perturbation technique to efficiently calculate strong skin and proximity effects in conductors within frequency and time domain finite element (FE) analyses. Design/methodology/approach - A reference eddy current FE problem is first solved by considering perfect conductors. This is done via appropriate boundary conditions (BCs) on the conductors. Next the solution of the reference problem gives the source for eddy current FE perturbation sub-problems in each conductor then considered with a finite conductivity. Each of these problems requires an appropriate volume mesh of the associated conductor and its surrounding region. Findings - The skin and proximity effects in both active and passive conductors can be accurately determined in a wide frequency range, allowing for precise losses calculations in inductors as well as in external conducting pieces. Originality/value - The developed method allows one to accurately determine the current density distributions and ensuing losses in conductors of any shape, not only in the frequency domain but also in the time domain. Therefore, it extends the domain of validity and applicability of impedance-type BC techniques. It also offers an original way to uncouple FE regions that allows the solution process to be lightened, as well as efficient parameterized analyses on the signal form and the conductor characteristics. [less ▲] Detailed reference viewed: 42 (9 ULg)Accuracy analysis of the thrust force in 2D-3D finite element models Deliège, Geoffrey ; ; in COMPEL (2006), 25(2), 320-333 Detailed reference viewed: 12 (1 ULg)Three-dimensional finite element modeling of inductive and capacitive effects in micro-coils Dular, Patrick ; V Sabariego, Ruth ; in COMPEL (2006), 25(3), 642-651 Purpose - The paper seeks to develop dual 3D finite element (FE) formulations for modeling both inductive and capacitive effects in massive inductors, in particular micro-coils. The paper aims to build ... [more ▼] Purpose - The paper seeks to develop dual 3D finite element (FE) formulations for modeling both inductive and capacitive effects in massive inductors, in particular micro-coils. The paper aims to build circuit relations relating the voltages and the currents in such inductors to be used in circuit coupling. Design/methodology/approach - A circuit relation involving a unique voltage and complementary inductive and capacitive currents is defined for each inductor. the inductive circuit relation is first classically obtained by a FE magnetodynamic model. Then, the capacitive relation is obtained through a FE electric model, using sources evaluated from the first model. The conformity is defined on one hand for the magnetic flux density and the electric field, and on the other hand for the magnetic field and the electric flux density. Mixed FE, i.e. nodal, edge and face elements, are used to satisfy each chosen conformity level for the unknown fields and to naturally define the involved global quantities, i.e. the voltages, currents and charges. Findings - This contribution points out the interest of satisfying conformity properties for the coupled magnetic and electric problems. An accurate computation of these effects is obtained in the critical frequency range of their strong interaction. In addition, the complementarity of dual solutions gives the possibility to estimate the discretisation error. Originality/value - The mathematical and discretisation tools for any wished conformity level are unified for naturally coupling magnetic and electric problems. The global quantities basis functions involved in the FE circuit relations benefit from a significant support reduction, which facilitates their evaluation and gives them direct physical interpretations. [less ▲] Detailed reference viewed: 45 (9 ULg)2D Harmonic Balance FE Modelling of Electromagnetic Devices coupled to Nonlinear Circuits ; Dular, Patrick ; Geuzaine, Christophe et al in COMPEL (2004), 23(3), 800--812 Detailed reference viewed: 41 (10 ULg)Application of data mining to optimize settings for generator tripping and load shedding system in emergency control at Hydro-Quebec ; ; et al in COMPEL (2004), 23(1 Sp. Iss. SI), 21-34 This paper describes the on-going work done by Hydro-Quebec to optimize the settings of automatic devices installed in its main power plants to maintain secure operation under extreme contingencies. The ... [more ▼] This paper describes the on-going work done by Hydro-Quebec to optimize the settings of automatic devices installed in its main power plants to maintain secure operation under extreme contingencies. The automatic generator tripping and load shedding system (RPTC) described in this paper is installed at the Churchill Falls hydroelectric power plant (5,500 MW) in Labrador. Data mining techniques such as decision trees and regression trees have been used. Real time snapshots of the Hydro-Quebec power system collected over a 5 year period have been used to generate large amounts of results by transient stability simulations. The processing of these data has been done using software developed by the University of Liege. This approach gives the most relevant parameters and finds optimal settings for the RPTC system, minimizing the number of tripped generator units while maintaining the same performance in terms of security coverage. New operation rules can thus be established. [less ▲] Detailed reference viewed: 38 (0 ULg)Comparisons of finite element and Rayleigh methods for the study of conical Bloch waves in arrays of metallic cylinders ; ; Geuzaine, Christophe et al in COMPEL (2004), 23(4), 932--949 Detailed reference viewed: 14 (2 ULg)The eggshell approach for the computation of electromagnetic forces in 2D and 3D ; Deliège, Geoffrey ; in COMPEL (2004), 23(4), 996-1005 Detailed reference viewed: 21 (2 ULg)Coupled mechanical-electrostatic FE-BE analysis with FMM acceleration V Sabariego, Ruth ; ; Dular, Patrick et al in COMPEL (2004), 23(4), 876-884 This paper deals with the coupled mechanical-electrostatic analysis of a shunt capacitive MEMS switch. The mechanical and electrostatic parts of the problem are modelled by the FE and BE methods ... [more ▼] This paper deals with the coupled mechanical-electrostatic analysis of a shunt capacitive MEMS switch. The mechanical and electrostatic parts of the problem are modelled by the FE and BE methods, respectively. The fast multipole method is applied to reduce the storage requirements and the computational cost of the BE electrostatic model An adaptive truncation expansion of the 3D Laplace Green function is employed The strong interaction between the mechanical and electrostatic systems is considered iteratively. [less ▲] Detailed reference viewed: 57 (13 ULg)3D h-phi finite element formulation for the computation of a linear transverse flux actuator Deliège, Geoffrey ; ; et al in COMPEL (2003), 22(4), 1077-1088 Detailed reference viewed: 10 (0 ULg)Application of the fast multipole method to the 2D finite element-boundary element analysis of electromechanical devices V Sabariego, Ruth ; ; Geuzaine, Christophe et al in COMPEL (2003), 22(3), 659-673 The present paper deals with the fast multipole acceleration of the 2D finite element-boundary element modelling of electromechanical devices. It is shown that the fast multipole method, usually applied ... [more ▼] The present paper deals with the fast multipole acceleration of the 2D finite element-boundary element modelling of electromechanical devices. It is shown that the fast multipole method, usually applied to large 3D problems, can also lead to a reduction in computational time when dealing with relatively small 2D problems, provided that an adaptive truncation scheme for the expansion of the 2D Laplace Green function is used. As an application example, the 2D hybrid modelling of a linear actuator is studied, taking into account saturation, the voltage supply and the mechanical equation. The computational cost without and with fast multipole acceleration is discussed for both the Linear and nonlinear case. [less ▲] Detailed reference viewed: 143 (20 ULg)Connection boundary conditions with different types of finite elements applied to periodicity conditions and to the moving band Dular, Patrick ; Geuzaine, Christophe ; et al in COMPEL (2001), 20(1), 109--119 Detailed reference viewed: 29 (5 ULg) |
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