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Purpose – Eddy current testing (ECT) is a nondestructive testing method for the detection of flaws that uses electromagnetic induction to find defects in conductive materials. In this method, eddy currents are generated in a conductive material by a changing magnetic field. A defect is detected when there is a disruption in the flow of the eddy current. The purpose of this paper is to develop a new noniterative inversion methodology for detecting degradation (defect characterization) such as cracking, corrosion and erosion from the measurement of the impedance variations. Design/methodology/approach – The methodology is based on multi-output support vector machines (SVM) combined with the adaptive database schema design method (SDM). The forward problem was solved numerically using finite element method (FEM), with its accuracy experimentally verified. The multi-output SVM is a statistical learning method that has good generalization capability and learning performance. FEM is used to create the adaptive database required to train the multi-output SVM and the genetic algorithm is used to tune the parameters of multi-output SVM model. Findings – The results show the applicability of multi-output SVM to solve eddy current inverse problems instead of using traditional iterative inversion methods which can be very time-consuming. With the experimental results the authors demonstrate the accuracy which can be provided by the multi-output SVM technique. Practical implications – The work allows extending the capability of the experimentation ECT defect characterization system developed at LGEP. Originality/value – A new inversion method is developed and applied to ECT defect characterization. This new concept introduces multi-output SVM in the context of ECT. The real data together with estimated one obtained by multi-output SVM model are compared in order to evaluate the effectiveness of the developed technique.

The aim of this study is to analyze and investigate some techniques to reduce eddy current losses in permanent magnets. First, a model using Maxwell's equations to analyze eddy current in permanent magnets is presented. Second, the effect of magnet circumferential segmentation on the eddy current losses in case of a surface mounted permanent magnets synchronous machine is investigated. A simple analysis of magnet demagnetization due to its eddy current losses is also studied. In a third step, second technique for reducing eddy current losses is presented. It relates to the stator slots skew, where the best skewing angle is obtained by means of an optimization process using genetic algorithm. A 2D nonlinear finite elements code is developed to achieve the purposes of the presented work.

In this paper we establish a comparison between the dynamic characteristics of two linear tubular stepper machines (LTSM) with the consideration of saturation. The first machine has a classical structure. However, in the second one, permanent magnets are inserted in the stator (inductor). A numerical analysis is performed to highlight the effect of inserting permanent magnets in the stator cores on the steps starting forces and global performances of the hybrid machine under a unidirectional switching ideal square-wave current. Both configurations are modeled and simulated via software based on Finite Elements method FLUX2D.

PurposeThe modelling of the electromagnetic devices with moving objects such as launchers, electrical machines and actuators, necessitates considering the motion. This paper aims to examine this subject.Design/methodology/approachThis task can be performed by introducing the velocity term in the electromagnetic equation. However, the application of this method leads to a non‐symmetrical finite element matrix. This numerical problem can be avoided either by the finite element meshing domain every displacement step or by using special techniques coupled to the finite element method like the moving bound, sliding surface and macro element (ME). The ME solution, based on an analytical model in the air‐gap of the devices, is more solicited for its low cost and accuracy by comparison with the other one. This technique keeps unchanged the finite element topology during the simulation, where the motion is taken into account by modification of the ME formula's every displacement.FindingsThis paper sought to present a new formula of the ME which is called dynamic ME. This new formula keeps unchanged the finite element topology and the terms of the analytical stiffness matrix too during the movement simulation.Research limitations/implicationsThe developed model is limited to analyzing the 2D devices with moving objects in linear or non‐linear case with saturation of the magnetic circuits. Extending the model to consider the 3D effects is the perspective of this work.Originality/valueThe developed formula is more economical than the classical one.

Print ISBN: 978-1-4799-3786-8; International audience; This paper provides a new methodology for the characterization of defect size in a conductive nonmagnetic plate from the measurement of the impedance variations. The methodology is based on Finite Element Method (FEM) combined with the Multi Output Support Vector Machines (MO-SVM). The MO-SVM is a statistical learning method that has good generalization capability and learning performance. FEM is used to create the adaptive database required to train the MO-SVM and the Cross Validation (CV) is used to find the parameters of MO-SVM model. The results show the applicability of MO-SVM to solve eddy current inverse problems instead of using traditional iterative inversion methods which can be very time-consuming. With the experimental results we demonstrate the accuracy which can be provided by the MO-SVM technique.

This paper deals with the eddy current loss reduction in a surface mounted permanent magnet synchronous machine. Numerical solution based on 2D finite elements method is used to compute eddy current losses in the permanent magnets. This calculation is integrated in an optimization process by genetic algorithm which aims to minimize eddy current loss in magnets according to stator slot shape. The proposed strategy is applied to the considered machine at no and full load conditions. In the second case, both distributed and concentrated windings are studied.

The response of grounding systems is calculated under fault conditions or when they are hit by lightning directly in time domain. The current distribution and potential along the structure are determined using transmission line theory. The electromagnetic fields in the surrounding soil are determined from the previously calculated current distribution using dipoles theory with analytical formulas in infinite conductive medium. Modified images theory is used for taking in account the interface in the half space instead Summerfield integrals. The model can be used to predict the E.M environment of grounding systems because; it can calculate electromagnetic fields in any points of interest.