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Title: CALCULATION OF THE FREQUENCY CHARACTERISTICS OF MICROSTRIPS DISCONTINUITIES ON NON-DIAGONAL ANISOTROPIC SUBSTRATES USING FDTD
Abstract: This paper describes modifications of the conventional finite-difference time-domain (FDTD) method to the full-wave analysis of frequency dependent characteristics of microstrips discontinuities on non-diagonal anisotropic substrates. The application of the conventional FDTD is limited to materials with diagonal-anisotropic material matrices. In this paper it is shown that this restriction can be removed: First, steps for obtaining the FDTD equations for the analysis of microstrips discontinuities on substrates with fully anisotropic permittivity matrices are derived. Then, using the Fourier transform of the computed results in the time-domain, the scattering parameters as functions of the frequency are calculated for several examples. [Vol. 12, No. 2 (1997), Special Issue on Numerical Field Calculations in Electrical Engineering, pp 11-15]
Author(s): S. M. Chehrehrazi, A. R. Baghai-Wadji
File Type: Journal Paper
Issue:Volume: 12      Number: 2      Year: 1997
Download Link:Click here to download PDF     File Size: 351 KB

Title: ELECTROMAGNETIC WAVES IN A NONLINEAR DISPERSIVE SLAB
Abstract: The electromagnetic scattering of a normal incident plane wave from a strongly nonlinear and dispersive dielectric slab is considered. The dynamics of the polarization density vector are described through a forced nonlinear ordinary differential equation of Duffing type, which takes both dispersive and nonlinear effects into account. The aim of the paper is to study the behaviour of the electromagnetic fields by using the Galerkin method. In particular it is shown that shock waves with infinite slope cannot be developed in real media because of the dispersion . [Vol. 12, No. 2 (1997), Special Issue on Numerical Field Calculations in Electrical Engineering pp 16-19]
Author(s): G. Miano, C. Serpico, L. Verolino, G. Panariello
File Type: Journal Paper
Issue:Volume: 12      Number: 2      Year: 1997
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Title: SENSITIVITY ANALYSIS USING HIGH ORDER DERIVATIVES
Abstract: In this article, we present a method of sensitivity analysis based on high order derivatives and Taylor expansion. The principle is to find a polynomial approximation of the finite element solution in terms of the sensitivity parameters. We present this method on two dimensional linear magnetostatic and linear magnetodynamic problems. The sensitivity parameters can be either physical parameters or geometric ones. Once the high order derivatives are found, the Taylor expansion allows evaluations for a new set of parameters. The time needed to obtain a new solution is negligible compared to a standard finite element re-analysis. This implies a dramatic change in the use of computational tools. Moreover, the availability of fast evaluations allows a wide use of optimization algorithms. [Vol. 12, No. 2 (1997), Special Issue on Numerical Field Calculations in Electrical Engineering, pp 20-25]
Author(s): J. L. Coulomb, P. Petin, L. Saludjian, N. Nguyen Thanh, R. Pacaut
File Type: Journal Paper
Issue:Volume: 12      Number: 2      Year: 1997
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Title: SELF ADAPTIVE FUZZY SETS IN MULTI OBJECTIVE OPTIMIZATION USING GENETIC ALGORITHMS
Abstract: Optimization in electrical engineering has attracted an increasing attention over the last few years. Various strategies to solve electromagnetic optimization problems have been introduced, amongst them stochastic, deterministic and hybrid ones. Most of today's real world applications, however, involve multiple conflicting objectives which should be considered simultaneously. The aim of this paper is to introduce self adaptive fuzzy sets to treat vector optimization problems. [Vol. 12, No. 2 (1997), Special Issue on Numerical Field Calculations in Electrical Engineering, pp 26-31]
Author(s): Ch. Magele, G. Furntratt, B. Brandstatter, K.R. Richter
File Type: Journal Paper
Issue:Volume: 12      Number: 2      Year: 1997
Download Link:Click here to download PDF     File Size: 428 KB

Title: OPTIMISATION OF THE SHAPE OF THE FERROMAGNETIC CORE OF FLUXSET TYPE MAGNETIC FIELD SENSORS
Abstract: A method is presented for the optimisation of the shape of the ferromagnetic core of fluxset type magnetic filed sensors. The objective of the optimisation is to find a core shape that guarantees the most homogeneous magnetisation of the core due to a given external magnetic field. By finding the optimal shape of the core the sensitivity of the sensor is improved. Since the thickness of the ferromagnetic conducting ribbon core used for fluxset sensors is considerably smaller than its other dimensions, the presence of the core is modelled by magnetic and conducting surface currents flowing in a mathematical surface representing the core. The electromagnetic field is calculated by solving an integral equation derived from the assumption of impedance type boundary conditions on the two sides of this surface. The core shape is optimised by minimising the magnetisation differences at different locations of the core. Simulated annealing procedure is used for the optimisation. [Vol. 12, No. 2 (1997), Special Issue on Numerical Field Calculations in Electrical Engineering, pp 32-37]
Author(s): Jozsef Pavo
File Type: Journal Paper
Issue:Volume: 12      Number: 2      Year: 1997
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Title: NUMERICAL TECHNIQUES FOR THE INVERSION OF EDDY CURRENT TESTING DATA
Abstract: In this paper, we discuss two techniques for the reconstruction of conductivity profiles in the low frequency limit. The first one is based on the second order approximation of the scattered field operator. In the second procedure, the problem is linearized at the expense of an increase in the number of unknowns including, in this case, the current density and the electric field. Some simple 2D examples are presented to point out and compare the main features of the two approaches. [Vol. 12, No. 2 (1997), Special Issue on Numerical Field Calculations in Electrical Engineering, pp 38-43]
Author(s): Guglielmo Rubinacci, Antonello Tamburrino
File Type: Journal Paper
Issue:Volume: 12      Number: 2      Year: 1997
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Title: MAGNETIC MATERIAL PROPERTY IDENTIFICATION USING NEURAL NETWORKS
Abstract: In the numerical solution of field problems for many devices, the modeling of the hysteresis properties of a material is extremely important. While considerable work has been published on models for handling this behavior, it is still difficult to obtain the parameters for these models from measured data. This paper proposes the use a neural network for this operation. [Vol. 12, No. 2 (1997), Special Issue on Numerical Field Calculations in Electrical Engineering, pp 44-49]
Author(s): Hamadou H. Saliah, David A. Lowther
File Type: Journal Paper
Issue:Volume: 12      Number: 2      Year: 1997
Download Link:Click here to download PDF     File Size: 561 KB

Title: OPTIMIZATION OF A SMES DEVICE UNDER NONLINEAR CONSTRAINTS
Abstract: In this paper a method to calculate the gradients for the TEAM 22 problem is presented. Furthermore an objective function different from the one proposed in the benchmark is used where the energy requirement was handled as an equality constraint. The so derived gradients of the objective function and the constraints together with a standard optimization routine are used to solve the problem. In the last section some new results concerning the presence of local minima for the problem are given. [Vol. 12, No. 2 (1997), Special Issue on Numerical Field Calculations in Electrical Engineering, pp 50-53]
Author(s): B. R. Brandstatter, Wolfgang Ring
File Type: Journal Paper
Issue:Volume: 12      Number: 2      Year: 1997
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Title: RECONSTRUCTION OF INHOMOGENEOUS LOSSY DIELECTRIC OBJECTS IN ONE DIMENSION
Abstract: The 1D inverse scattering problem of reconstructing the material properties of an inhomogeneous lossy dielectric slab is considered. The material properties are reconstructed using scattering data from time harmonic electromagnetic plane waves. The incident plane waves are either TE or TM polarized. The inverse scattering problem formulated as a nonlinear optimization problem by means of integral equations is numerically solved using an iterative scheme and Tikhonov regularization. Numerical examples with both types of polarization are presented. [Vol. 12, No. 2 (1997), Special Issue on Numerical Field Calculations in Electrical Engineering, pp 54-59]
Author(s): W. Rieger, M. Haas, C. Huber, G. Lehner, W.M. Rucker
File Type: Journal Paper
Issue:Volume: 12      Number: 2      Year: 1997
Download Link:Click here to download PDF     File Size: 506 KB

Title: LAGRANGIAN BEM-FEM SOLUTION OF ELECTROMAGNETIC-MECHANICAL COUPLED PROBLEMS
Abstract: In the framework of the electro-mechanical coupled problems, the coupling between the magnetic diffusion and the elastic deformation equations is treated numerically. A mixed BEM-FEM approach for the electromagnetic part, and a FEM approach for the mechanical part, are proposed. Advantages are taken from a Lagrangian formulation of the problem. [Vol. 12, No. 2 (1997), Special Issue on Numerical Field Calculations in Electrical Engineering, pp 60-65]
Author(s): F. Villone, A. Formisano, R. Martone, F. Villone
File Type: Journal Paper
Issue:Volume: 12      Number: 2      Year: 1997
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Title: MODELLING OF DEGAUSSING COILS EFFECTS ON SHIPS
Abstract: This paper presents our work on magnetic modelling of ships, especially their degaussing coils. We first focus on these coils effects in the FEM computations. The main reason of bad results is a locally inadequate mesh. We propose a method named " reduced potential jump" to avoid the use of a very fine mesh. Then, comparison of results is presented for a simple geometry. [Vol. 12, No. 2 (1997), Special Issue on Numerical Field Calculations in Electrical Engineering, pp 66-70]
Author(s): F. Le Dorze, J. P. Bongiraud, J. L. Coulomb, G. Meunier, X. Brunotte
File Type: Journal Paper
Issue:Volume: 12      Number: 2      Year: 1997
Download Link:Click here to download PDF     File Size: 302 KB

Title: A THREE-DIMENSIONAL ANALYSIS OF MAGNETIC SHIELDING WITH THIN LAYERS
Abstract: This paper describes a numerical method for the analysis of the magnetic shielding with thin layers in three dimensional, time-harmonic magnetic fields. In this method, FEM is employed to solve a couple of differential equations which express the surface impedance of the thin shielding materials. The magnetic fields in air regions are modeled by means of BEM. The above formulations are coupled to evaluate the shielding properties. The resultant matrix equation includes unknowns of two times the number of nodal points. This method can analyze not only a shielding system with closed surfaces but also that with open surfaces without
Author(s): H. Igarashi, T. Honma, A. Kost
File Type: Journal Paper
Issue:Volume: 12      Number: 2      Year: 1997
Download Link:Click here to download PDF     File Size: 288 KB

Title: A C.A.E. TOOL TO UNDERSTAND MAGNETOSTATICS
Abstract: We present in this paper a Computer Aided Education package allowing to visualize the magnetostatic field in and around the magnetic circuit of a double-U shaped contactor. The modeling of this device is performed by solving in real time a non-linear finite element problem. The imple- mentation of this method is optimized greatly in order to allow to animate field patterns in real time in reaction to any user interaction. An evaluation of the improvements brought by this technique to the learning capabilities of students is presented. [Vol. 12, No. 2 (1997), Special Issue on Numerical Field Calculations in Electrical Engineering, pp 81-84]
Author(s): F. Buret, D. Muller, A. Nicolas, L. Nicolas
File Type: Journal Paper
Issue:Volume: 12      Number: 2      Year: 1997
Download Link:Click here to download PDF     File Size: 414 KB

Title: NUMERICAL MODELLING OF AN AXIAL-FIELD SOLID DISK INDUCTION MACHINE
Abstract: In this paper a method for the steady-state analysis of an axial-field induction motor with a solid disk rotor is proposed. The boundary condition for the axial component of the magnetic flux density has been calculated by means of an analytical procedure. Accordingly the simulation region is restricted to the air-gap and the rotor. Then the axial component of the diffusion equation is solved for by using a finite difference scheme. Subsequently the azimuthal component of the magnetic flux density and the current density induced in the rotor come out from the field's laws. The validity of the proposed method has been tested by comparing the numerical results with data measured on a double-stator prototype. Finally the numerical procedure has been used for the analysis of the performance of a motor for light vehicle propulsion and the results of the simulation are shown. [Vol. 12, No. 2 (1997), Special Issue on Numerical Field Calculations in Electrical Engineering, pp 85- 89]
Author(s): Marco Angeli, Nunzio Esposito, Antonino Musolino, Bernardo Tellini
File Type: Journal Paper
Issue:Volume: 12      Number: 2      Year: 1997
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Title: MODELLING DYNAMIC HYSTERESIS IN FERROMAGNETIC SHEETS UNDER TIME-PERIODIC SUPPLY CONDITIONS
Abstract: This paper presents an application of the Dynamic Preisach Model as proposed by Bertotti, to the analysis of electromagnetic phenomena inside a ferromagnetic lamination subject to imposed time-periodic magnetic flux. The field problem, considered as one dimensional, is formulated in terms of magnetic field and the Fixed Point technique is used for the treatment of the hysteretic nonlinearity. The solution is carried out in the harmonic domain by means of the Finite Element method. The original implementation of the Dynamic Preisach Model is detailed and comparisons with measurements are presented in the case of sinusoidal excitations. [Vol. 12, No. 2 (1997), Special Issue on Numerical Field Calculations in Electrical Engineering, pp 90-95]
Author(s): Oriano Bottauscio, Mario Chiampi, Maurizio Repetto
File Type: Journal Paper
Issue:Volume: 12      Number: 2      Year: 1997
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Title: DYNAMIC OPERATION OF COILS WITH FERROMAGNETIC CORES TAKING MAGNETIC HYSTERESIS INTO ACCOUNT
Abstract: The computation of electromagnetic field diffusion in ferromagnetic and conductive media is coupled to circuit analysis problems, involving coils with iron cores. The classical Preisach model provides the relationship between magnetic field intensity and flux density at the local level, inside the core. Combined with a 2D eddy current simulation, carried out by a time stepping method, the dynamic operation of the core is modelled. The circuit equations are solved taking the effects of hysteresis and skin effects caused by eddy currents induced in core sheets into account. [Vol. 12, No. 2 (1997), Special Issue on Numerical Field Calculations in Electrical Engineering, pp 96-101]
Author(s): Janos Fuzi
File Type: Journal Paper
Issue:Volume: 12      Number: 2      Year: 1997
Download Link:Click here to download PDF     File Size: 433 KB

Title: A STRONG COUPLING MODEL FOR THE SIMULATION OF MAGNETOMECHANICAL SYSTEMS USING A PREDICTOR/MULTI-CORRECTOR ALGORITHM
Abstract: A recently developed modeling scheme for the numerical simulation of coupled magnetomechanical systems is presented. The scheme allows the calculation of dynamic rigid motions as well as deformations of magnetic and anti-magnetic materials in a magnetic field. The equations governing the magnetic and mechanical field quantities are solved using a combined Finite Element /Boundary-Element-Method (FEM-BEM). To circumvent the nonlinear system of equations resulting from a direct coupling of the magnetic and mechanical systems, the calculation of the magnetic forces is based on predictor values of the magnetic quantities. Therewith, a decoupling into a magnetic and mechanical matrix equation can be achieved. To ensure the strong coupling between the magnetic and mechanical quantities, a sophisticated Predictor/Multicorrector Algorithm is used resulting in an efficient iteration between the two matrix equations within a single time step. Computer simulations of an electromagnetic forming system and a magnetomechanical transducer immersed in an acoustic fluid (acoustic power source) show good agreement between simulation results and measured data. [Vol. 12, No. 2 (1997), Special Issue on Numerical Field Calculations in Electrical Engineering, pp 102-106]
Author(s): M. Kaltenbacher, H. Landes, R. Lerch
File Type: Journal Paper
Issue:Volume: 12      Number: 2      Year: 1997
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Title: RESULTS OF PARALLELISATION OF EXISTING ELECTROMAGNETIC FINITE ELEMENT CODES ON SOME DIFFERENT PARALLEL ARCHITECTURES
Abstract: In this paper the results obtained from the parallelisation of some 3D industrial electromagnetic Finite Element codes within the ESPRIT Europort 2 project PARTEL are presented. The basic guidelines for the parallelisation procedure, based on the Bulk Synchronous Parallel approach, are presented and the encouraging results obtained in terms of speed-up on some selected test cases of practical design significance are outlined and discussed. [Vol. 12, No. 2 (1997), Special Issue on Numerical Field Calculations in Electrical Engineering, pp 107-112]
Author(s): M. Dracopoulos, K. Palrot, G. Molinari, M. Nervi, J. Simkin
File Type: Journal Paper
Issue:Volume: 12      Number: 2      Year: 1997
Download Link:Click here to download PDF     File Size: 617 KB

Title: THE NEWTON-RAPHSON METHOD FOR COMPLEX EQUATION SYSTEMS
Abstract: A formulation for the complex Newton-Raphson method is proposed. The derivation is obtained on the assumption of a non-analytical system. The method is applied to the finite element calculation of shielding problems with sinusoidal ex-citation and ferromagnetic material. An application example for which measurement data are available is given in order to judge the convergence characteristics and the reliability of the proposed method. [Vol. 12, No. 2 (1997), Special Issue on Numerical Field Calculations in Electrical Engineering, pp 113-116]
Author(s): Dieter Lederer, Hajime Igarashi, Arnulf Kost
File Type: Journal Paper
Issue:Volume: 12      Number: 2      Year: 1997
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Title: SOME ASPECTS OF MAGNETIC FORCE COMPUTATION USING BEM-FEM COUPLING
Abstract: For the calculation of magnetic forces with the Maxwell stress tensor the normal and the tangential derivatives of the vector potential A have to be known. We choose Co-continuous elements, therefore A and its tangential derivatives are continuous. In contrast, the normal derivative A/ n calculated with the finite element method is continuous only in a weak sense. When BEM-FEM coupling is used however, the value of A/ n is uniquely available on the coupling surfaces from the BEM formulation. Two methods of magnetic force computation using A/ n either from FEM or from BEM data will be presented. Their accuracy will be compared by means of several examples. [Vol. 12, No. 2 (1997), pp Special Issue on Numerical Field Calculations in Electrical Engineering, 117-120]
Author(s): Joachim Fetzer, Stefan Kurz, Gunther Lehner, Wolfgang M. Rucker
File Type: Journal Paper
Issue:Volume: 12      Number: 2      Year: 1997
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Title: THE NUMERICAL TREATMENT OF SINGULAR INTEGRALS IN BOUNDARY ELEMENT CALCULATIONS
Abstract: In this paper a general method for the evaluation of singular boundary element integrals over three-dimensional isoparametric boundary elements of higher order is presented. This method permits an efficient integration of strongly singular kernels of order O(1/r2) and of nearly strong singular kernels on curved surfaces. For numerical examples the proposed integration scheme is compared with analytical test examples showing high efficiency and accuracy. This new method has full generality and, therefore, can be applied in any field of electromagnetics. The actual computation can be easily included in any existing computer code, e. g. for the solution of electromagnetic scattering problems. [Vol. 12, No. 2 (1997), Special Issue on Numerical Field Calculations in Electrical Engineering, pp 121-126]
Author(s): C.J. Huber, W. Rieger. M. Haas, W.M. Rucker
File Type: Journal Paper
Issue:Volume: 12      Number: 2      Year: 1997
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Title: VARIOUS APPROACHES TO TORQUE CALCULATIONS BY FEM AND BEM
Abstract: Different algorithms for the torque calculation by Maxwell stress method (MSM) are dealt with in the paper. The aim of designing these algorithms was to reduce the influence of the choice of the integration path and discretization of the air gap between the stator and rotor on the accuracy of the results. In some of these algorithms the connection between the stator and rotor is released For the magnetic field calculation the finite element method (FEM), boundary element method (BEM), and hybrid finite element - boundary element method (HM) were used. The calculation results were tested on a permanent magnet DC motor and a single phase brushless motor. [Vol. 12, No. 2 (1997), Special Issue on Numerical Field Calculations in Electrical Engineering, pp 127-130]
Author(s): Mladen Trlep, Anton Hamler, Bozidar Hribernik
File Type: Journal Paper
Issue:Volume: 12      Number: 2      Year: 1997
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Title: MODELLING EDDY CURRENTS INDUCED BY ROTATING SYSTEMS
Abstract: As part of a Japanese funded project, a transient eddy current code is being extended to allow for rotational systems. By allowing the system to rotate, induced eddy currents must be modelled. The system being developed uses the "lock-step" approach to model the rotation. As other facilities are included (non-linear materials for example), the solution time of the final code becomes sufficiently large that special care must be taken, and investigations into using parallel hardware becomes necessary. [Vol. 12, No. 2 (1997), Special Issue on Numerical Field Calculations in Electrical Engineering, pp 131-134]
Author(s): C. R. I. Emson, C. P. Riley, D. A. Walsh
File Type: Journal Paper
Issue:Volume: 12      Number: 2      Year: 1997
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Title: BEM-FEM COUPLING IN ELECTROMECHANICS: A 2-D WATCH STEPPING MOTOR DRIVEN BY A THIN WIRE COIL
Abstract: This paper deals with the transient numerical analysis of 2-d electromechanical devices driven by thin wire coils. Their dynamical behavior is described by the Maxwell equations, by the constitutive relations, and by the equations of motion. For the solution of the electromagnetic problem the BEM-FEM coupling method is used. A two- dimensional watch stepping motor is presented as an example. [Vol. 12, No. 2 (1997), Special Issue on Numerical Field Calculations in Electrical Engineering, pp 135-139]
Author(s): Stefan Kurz, Joachim Fetzer, Thomas Kube, Gunther Lehner, Wolfgang M. Rucker
File Type: Journal Paper
Issue:Volume: 12      Number: 2      Year: 1997
Download Link:Click here to download PDF     File Size: 389 KB

Title: HYBRID FORMULATIONS FOR 3D MAGNETOSTATIC AND EDDY CURRENT PROBLEMS
Abstract: Hybrid formulations for solving nonlinear 3D magnetostatic and eddy current problems in terms of magnetic field H are presented. In the pro- posed formulations integral operators are utilized as if the boundary conditions for a partial differential equation were solved within the system of equations. A good correspondence between the results of the presented methods and measurements or other methods is obtained for some test problems. [Vol. 12, No. 2 (1997), Special Issue on Numerical Field Calculations in Electrical Engineering, pp 140-144]
Author(s): Kimmo Forsman, Lauri Kettunen
File Type: Journal Paper
Issue:Volume: 12      Number: 2      Year: 1997
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