Laurent Morel

Temperature Dependent Extension of the Jiles-Atherton Model: Study of the Variation of Microstructural Hysteresis Parameters

Environmental requirements currently placed on magnetic materials that are used in both domestic and professional electromagnetic devices are becoming more stringent. The growing demand for components to operate under extreme environmental conditions prompted this study of the effect of temperature variation on magnetic materials. Thus, the knowledge of their behavior, especially under high temperatures, is of prime importance. In this paper, two methods for determining the evolution of Jiles-Atherton model parameters with temperature are presented. The parameters evolution of the model as a function of temperature is discussed. Both methods are compared.

Magnetic Behavior Representation Taking Into Account the Temperature of a Magnetic Nanocrystalline Material

The aim of this study consists in modeling the magnetic behavior of a nanocrystalline material, taking into account temperature variation. Indeed the development of power electronic embedded systems leads to increase the operating temperature range. Besides nanocrystalline material is used more and more in such systems, so temperature influence is a key point in the magnetic component design.

Limits and rules of use of a dynamic flux tube model

Purpose - The purpose of this paper is to analyze the main assumption of a dynamic flux tube model and to define its rules of use. Design/methodology/approach - The studied dynamic model lumps together all dynamic effects in the circuit by considering a single dynamic parameter. A physical meaning of this parameter as well as rules of use of the model are elaborated from analyses performed on several samples. A systematic comparison between experimental and calculated results allows to argue the conclusions. Findings - The model gives accurate results when a weak heterogeneity of magnetic data exists, nevertheless, the saturation phenomenon enlarges the validity domain. By considering the losses separation assumption, the model allows to obtain separately an estimation of losses due to classical eddy currents and due to the wall motion effects. Research limitations/implications - The estimation of the models parameter value is still empiric, a work is in progress on this subject. Practical implications - The models implementation in a flux tubes network allows to simulate the dynamic behaviour of industrial actuators having massive cores. Originality/value - A physical interpretation of the parameter associated to the dynamic flux tube model is given. Rules of use of the model are also defined.

Computation of Induced Fields Into the Human Body by Dual Finite Element Formulations

In this work we present two dual finite element formulations to compute extremely low frequency (ELF) induced fields into the human body. This allows to estimate the numerical error, as well as rigorously bound the (global) co-energy. This method is herein applied to the classical case of the exposure to a homogeneous magnetic field, and to the field generated by an infinite wire.

Characterization and Modeling of a Current Transformer Working Under Thermal Stress

This paper focuses on the thermal stress on magnetic materials under Curie temperature. The influence of the temperature on static and dynamic major B(H) loops is studied. Then, the Jiles-Atherton (JA) model and “flux tube” model are used, in order to reproduce the static and dynamic hysteresis loops for a NiFe (80/20) alloy. For each temperature, the six model parameters are optimized from measurements. Finally, these parameters are used in order to reproduce the behavior of a current transformer. The simulation results are compared with measurements and discussed.

Simulation of Low-Nickel-Content Alloys for Industrial Ground Fault Circuit-Breaker Relays

The aim of this paper is to simulate the performances of a ground fault circuit-breaker (GFCB) relay with new low-nickel-content alloys. Indeed, in the construction industry, the materials become more expensive as their nickel content increases. Moreover, the demand for nickel is particularly sensitive to the economic conjuncture. Therefore, an original electromagnetic relay model has been developed and validated in different working conditions (current amplitude, frequency, and temperature). A dedicated magnetic characterization of materials is needed, using basically a usual and industrial GFCB relay for reference and design data in modeling. First, the magnetic model of the relay is built and checked against experimental data. The simulation may predict the tripping current threshold of the relay. On the other hand, new low-nickel-content alloys for relay parts are studied in this framework, thanks to the developed model. The effects of temperature on the magnetic properties of the candidate materials and the electrical performances of the virtual relays are presented. The results, analysis, and conclusions are given. Finally, a first attempt to predict the economic gain obtained with a change of material is made.

Numerical dosimetry of currents induced in the human body by ELF magnetic fields

The classical φ − a formulation for numerical dosimetry of currents induced by ELF magnetic fields requires that the source field is provided through a vector potential. We present here a new formulation t − b which directly takes the flux density as source term. This formulation is implemented through Finite Element and validated by comparison with analytical solutions. The results obtained by both formulations are compared in the case of an anatomical computational phantom exposed to a vertical uniform field. As example, the t − b formulation is used for computing the induced fields in the body exposed to the stray field of a 2.5 MW HTA/BT three-phase power transformer.

Homogenised magnetic diffusion. Dependence of static hysteresis

The aim of this study consists in comparing the contributions of two static hysteresis models (chemical model and Jiles-Athertons) in dynamic representation of magnetic behaviour using the magnetic diffusion problem. To improve the performance of both static hysteresis models in the magnetic diffusion equation, it has been homogenized and tests have been performed on a toroidal core of non-oriented FeSi sheets. The material has been excited at a rather low frequency in order to avoid the skin effect. Tests have been made first for excitations leading to major loops then for specific waveforms to obtain minor loops and recoil lines. Results for both models are quantified in terms of accuracy, convergence and computing time. Cet article compare les apports des modeles dhysteresis statiques chimique et de Jiles-Atherton pour la representation dynamique dun materiau par la diffusion magnetique. Afin de mettre en valeur les performances de chacun des deux modeles dhysteresis statiques dans lequation de diffusion magnetique, cette derniere est homogeneisee et des tests sont effectues sur un echantillon torique constitue dun empilement de rondelles de FeSi a GNO de faible epaisseur. Le materiau est excite a une frequence reduite afin de ne pas provoquer lapparition de leffet de peau. Des essais sont operes dans un premier temps pour des excitations conduisant a des cycles majeurs et mineurs centres puis, dans un deuxieme temps, pour des formes dondes particulieres amenant a lobtention de cycles de recul ou de boucles mineures decentrees. Les resultats obtenus pour les deux modeles sont quantifies en termes de precision, de convergence et de temps de calcul.