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The process of identifying unknown hidden objects by taking advantage of electromagnetic effects becomes more and more important. Clearing of mines or finding electrical conductors in concrete should be mentioned here. Magnetisation and eddy currents are the phenomena which are used in general. In this case, the layout and arrangement of the excitation coils and receiving coils influences the effectiveness and accuracy crucially. This design optimization process can be done by simulating the electromagnetic field with a 3D finite element method. Once a satisfying configuration has been found, the question arises, which quantities of the measured (and hence simulated) signals contain the most reliable information? Since the 3D finite element calculations are very time consuming, the inverse problem (detecting the ferrous object from some measured signals) is performed by approximating the corresponding electromagnetic signal by a neural network. Investigations on a ferrous conductive rod will be described in the paper.

A boundary element method in terms of the field variables is applied to three‐dimensional electromagnetic scattering problems. Especially, the influence of a dipole excited field on low conducting materials situated very close to the antenna will be discussed. We use higher order edge elements of quadilateral shape for the field approximation on curved surfaces. The tangential components of the unknown field variables are interpolated by vector element functions. The Galerkin method is implemented to obtain a set of linear equations. The applicability of the proposed edge element is investigated by the comparison of different BEM‐formulations and FEM‐results.

The purpose of this paper is to extend a (μ/ρ, λ) evolution strategy to perform remarkably more globally and to detect as many solutions as possible close to the Pareto optimal front.

A C‐link cluster algorithm is used to group the parameter configurations of the current population into more or less independent clusters. Following this procedure, recombination (a classical operator of evolutionary strategies) is modified. Recombination within a cluster is performed with a higher probability than recombination of individuals coming from detached clusters.

It is shown that this new method ends up virtually always in the global solution of a multi‐modal test function. When applied to a real‐world application, several solutions very close to the front of Pareto optimal solutions are detected.

Stochastic optimization strategies need a very large number of function calls to exhibit their ability to reach very good local if not the global solution. Therefore, the application of such methods is still limited to problems where the forward solutions can be obtained with a reasonable computational effort.

The main improvement is the usage of approximate number of isolated clusters to dynamically update the size of the population in order to save computation time, to find the global solution with a higher probability and to use more than one objective function to cover a larger part of the Pareto optimal front.

Benchmark problem 5 of the TEAM workshops consists of four aluminium blocks placed in the space between the jaws of an electromagnet. Three dimensional eddy currents are induced by 50 Hz time‐varying flux. Eleven sets of results from nine groups of contributors are compared with experimental measurements. The results from most of the computer codes tend to converge to common limits. These limits are in some places slightly different from some of the measured results. The reason for this discrepancy is thought to be due to the idealised boundary conditions, ignoring any losses in laminated iron, which are assumed in all the computer models.

Benchmark Problem 3 of the International Workshops for Eddy Current Code Comparison is an aluminum plate with two holes, the Bath Plate. Currents are induced by a coil carrying time harmonic currents of 50 or 200 Hz. Results from seven groups, using seven different computer codes, are compared with experimental measurements. Different methods treated the holes in very different ways, but all produced generally acceptable results. The good results of the two methods that treated the conductor as a thin sheet suggest that the problem is basically two‐dimensional.

Problem 5 of the International Workshops for Eddy Current Code Comparison consists of four aluminium blocks symmetrically located in an alternating magnetic field (the Bath Cube). Five solutions employing five computer codes are described and compared with experimental results. In this, the most three‐dimensional of the six problems, with no 2‐D approximation to give insight, the results diverge about precisely those features of the field that computer simulations are expected to reveal.

This paper aims to present an accurate magnetic equivalent circuit for modeling the cylindrical electromagnet so that by analyzing it, the magnetic flux density in different parts of the electromagnet, as well as its lifting force, can be calculated.

The structure of the electromagnet is divided into parts that can be modeled by lumped element parameters. Mathematical equations for calculating these elements are presented and proved. The axial symmetry of the cylindrical electromagnet made it possible to use planar circuits for its modeling. To increase the accuracy of the proposed equivalent circuit, attention has been paid to the leakage flux as well as the nonlinear behavior of the ferromagnetic core. Also, the curvature of the magnetic flux path is considered in the calculation of the corner permeances of the core.

The magnetic flux density in different parts of the electromagnet was calculated using nodal analysis of the circuit and compared to the results of the finite element method. Also, a test bed was established to measure the lifting force of the electromagnet. Comparing the results shows a difference of less than 3% which indicate the good accuracy of the proposed circuit. In addition, due to the curvature of the flux path, there is a no-flux region in the center of the disk, the extent of which depends on the thickness of the disk and the diameter of the middle leg.

Magnetic equivalent circuit is a new contribution to analyze the cylindrical electromagnet and calculate its lifting force with good accuracy. The circuit lumped elements can be quickly calculated using mathematical equations and software such as MATLAB according to the actual path of the magnetic flux. Compared to other methods, the proposed circuit analyzes the electromagnet in a shorter period of time. This is the most important advantage of the proposed circuit model.

Problem 11 of the TEAM workshops for eddy current code comparison is a hollow conducting sphere in a uniform magnetic field. The applied field varies with time as a step function, requiring a fully transient solution. A total of 13 sets of results are presented in this paper from various groups employing 12 different computer codes. The numerical results are compared with an analytic solution to the problem.

Problem 8 of the TEAM workshop comes from non‐destructive testing. A differential probe moves above a block with a crack. Three experimental and four numerical results are presented and analysed. Some specific difficulties arising in this problem are discussed.

Problem 6 of the International Workshop for Eddy Current Code Comparison is a hollow sphere in a uniform sinusoidal field. A total of 21 solutions, employing 17 different computer codes, are described and compared with analytic results. Several kinds of codes including 2‐D finite element, 3‐D finite element, and boundary element were found to give satisfactory solutions.