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Grain-oriented electrical steels (GOES) are widely used in the manufacturing of high efficiency energy conversion systems thanks to their excellent magnetic properties along the rolling direction. Nevertheless, on the one hand, GOES exhibit strong magnetic anisotropy, resulting in distinct magnetic properties regarding the direction of the applied magnetic field to the rolling direction. On the other hand, GOES undergoes changes in their magnetic properties due to the industrial manufacturing process and mechanical constraints during operation. In general, stress, and particularly compressive stress, deteriorates magnetic properties. This paper deals with the modeling of the magnetic behavior of GOES under compressive stress. The orientation distribution function (ODF) based approach recently applied to describe the B-H first magnetization curves of a conventional GOES without stress as well as under applied uniaxial mechanical tensile stress is extended to account for the effect of compressive stress, with different considerations of modeling. The magnetic properties and the sensitivity of the ODF-based model to the magnetization direction as well as to the applied compressive stress are analyzed. Oscillation issues inherent to the ODF-based model are also discussed.

Grain-oriented electrical steels (GOES) are extensively utilized in power transformers to enhance energy efficiency and reduce their size and weight. GOES are characterized by their strong magnetic anisotropy, leading to distinct magnetic characteristics (behavior law and iron losses) according to the direction and the intensity of the applied field with respect to the rolling direction (RD). The Orientation Distribution Function (ODF) based approach is a convenient method for describing the anisotropy of the GOES behavior law owing to its ease of identification and implementation. However, it exhibits a significant oscillation issue at low magnetic fields. To address this issue, a high-order ODF-based method has been proposed in the literature. In this article, the ODF-based model, initially stress-free, is extended to include the effects of mechanical tensile stress on the first magnetization curves of a conventional GOES. An ODF-based model considering both magnetic anisotropy and mechanical tensile stress is then proposed. The results are discussed and compared with experimental data.

The interest of non-destructive testing (NDT) in steel material characterization is growing especially for quality and life cycle control. The Magnetic Barkhausen Noise (MBN) analysis shows an extreme sensitivity to different parameters: steel grade, grain size, microstructure, magnetic domains wall structure, residual stress, surface condition, etc. It is very difficult to distinguish the individual effect of each parameter on the steel MBN signature. This paper attempts to address this problematic by fixing most of these parameters and varying only one parameter of interest (either austenitizing or tempering temperature) to assess the ability of the MBN technique to dissociate the mechanical properties of different martensitic steel grades. The MBN technique presented herein has proven to be able to distinguish high-performance martensitic steel grades when applied according to the proposed experimental protocol.

Grain-Oriented Electrical Steels (GOES) are widely used in transformers to increase energy efficiency while reducing the volume and weight of such transformers. These GOES are characterized by their strong anisotropy, which leads to different magnetic properties (behavior law and iron losses) depending on the strength and the direction of the applied magnetic field to the rolling direction (RD). To describe the anisotropy of the GOES behavior law, the Orientation Distribution Function (ODF) based approach shows interesting features regarding ease of identification and implementation. However, a significant oscillation issue in this model at low magnetic field exits. It is recently reported that a high-order ODF based method can improve the accuracy of the original model. But the high-order ODF based model implies an important number of experimental data according to different directions of the applied field to RD (different magnetization angles) to build a model with sufficient accuracy. In addition, the accuracy also depends on how the input magnetization angles are selected between the RD and the transverse direction (TD). In this article, an optimal algorithm for input magnetization angle selection is proposed for the high-order ODF based method. To validate the proposed algorithm, 13 magnetization angles have been measured. A comparative study has been conducted based on the original and the high-order ODF based models built with the proposed selected magnetization angles. It is shown that the proposed algorithm can reduce the number of experimental data needed for the ODF based model while providing an acceptable global error.

The need for electrical machines is growing in a wide range of applications nowadays, such as for energy production, automotive, marine, and medical equipment, etc. The reliability, efficiency, performance and operational safety are always critical issues, which implies that the monitoring and analysis during the operation of the equipment need to be strengthened. In general, more sensors can give higher accuracy of the estimated physical quantity, but bring a more expensive cost. To address this issue, an algorithm principally based on the parameterized background data-weak (PBDW) method is proposed and adopted in this work to optimize both the number and the location of sensors. Besides, to further investigate the performance of the proposed algorithm, a prototype concerning an anisotropic magnetostatic problem is studied as an example for the placement of magnetic sensors. The numerical experiments shows that the proposed method can achieve very satisfactory results in different aspects.

The magnetic behavior of a lamination stack made of grain-oriented electrical steel (GOES) is investigated under non-conventional 3D magnetic flux excitations. An experimental demonstrator has been designed to study a normal orientation of the magnetic flux path, with regard to the lamination plane, combined with different in-plane orientations of the easy magnetization axis of the lamination stack. The results in terms of the magnetic flux distribution and the iron losses are presented and discussed.

Nondestructive testing (NDT) of industrial steel products is commonly used to detect defects such as cracks using among other methods, electromagnetic techniques. When properly calibrated, these NDT can be adapted to evaluate the mechanical properties of steels. It is especially of prime importance when rigorous quality control must be achieved for high performance steels. In this context, the proposed article deals with the investigation of the Magnetic Barkhausen Noise (MBN) to characterize the tensile properties of high mechanical performance martensitic steels.

The magnetic behavior of a lamination stack made of grain-oriented electrical steel (GOES) is investigated under non-conventional 3D magnetic flux excitations. An experimental demonstrator has been designed to study a normal orientation of the magnetic flux path, with regard to the lamination plane, combined with different in-plane orientations of the easy magnetization axis of the lamination stack. The results in terms of the magnetic flux distribution and the iron losses are presented and discussed.

This paper deals with the temperature-dependent modelling of iron losses in the context of magnetic ageing of electricals steel used in high power electrical machines. First, two electrical steel sheet grades were heat treated at three temperatures in order to study the ageing effect evolution as a function of temperature. Results show a significant increase in iron losses for both steel grades. Then, considering the link between the macroscopic magnetic properties evolution (effect) and the microscopic precipitation (cause), the Johnson – Mehl – Avrami – Kolmogorov (JMAK) law describing the kinetics of precipitation was applied to model the time evolution of magnetic ageing. By coupling this model with the Arrhenius’ law, a model is developed to be able to predict the ageing for several temperature levels.

This paper deals with the analysis of the magnetic properties degradation following an industrial impregnation process of electrical steels employed in stators of large generators. First, the impregnation process is studied directly on industrial stators to emphasize the significance of the process effect. Then, to have a controlled approach of the impregnation conditions, laminated ring cores were subjected to the same process but for different configurations. The ring cores were magnetically characterized to highlight the influence of the resin on the magnetic properties. Also, in order to distinguish the effect of the resin from potential other phenomena during the curing phase (i.e. the ageing effect), an experimental protocol is proposed: the results allow to emphasize the impact of such process on the magnetic properties.

The performance and energy efficiency of electro-mechanical converters are strongly bound to the properties of their magnetic cores. The latter are mostly made from stacked laminations of soft magnetic materials, such as Fe3%Si, which limits the core geometry design. However, when complex geometries are required, usually forging processes may be employed but with very low silicon steels (<0.5%) to be able to forge the steel. In that case, the low silicon content yields to higher electrical conductivity and then to higher eddy current loss. In this work, an additive manufacturing technique allowing to build complex geometries is studied with Fe3%Si magnetic materials. The fabrication process allows to obtain green parts which are then densified through debinding and sintering steps. The magnetic characterization is performed on toroidal cores and allows to observe a high level of magnetic induction and relative permeability. Finally, the impact of the printing strategy on the magnetic performances is investigated.

The manufacturing processes of electrical machines may lead to significant degradation of the magnetic properties of their magnetic core (stator, rotor) performances and, as a consequence, to a decrease of their energy efficiency. While the effects of some processes (cutting, welding …) are widely discussed in the literature, this is not the case with the compaction process although it is systematically used to maintain the assembly of electrical steel sheets that compose the magnetic circuits. In addition to the conventional one, a specific compaction process exists for high-power electrical machines. After an introduction, the paper firstly deals with the two studied processes (conventional, specific). Then, an experimental mock-up to study the impact of the two configurations on the magnetic properties (iron losses, normal magnetization curve) is presented. This mock-up is the first, in the literature, that allows to study the effect of a controlled compaction mechanical stress on magnetic properties. Obtained results in both configurations highlight a magneto-mechanical effect that is not reported in the literature where these effects are commonly considered following in-plane mechanical stresses. This paper presents a magneto-mechanical model, taking into account the compaction stress effect, as well as a modelling protocol to model the effect of 3D mechanical stress on magnetic properties, which has never been done in the literature.

Nowadays, additive manufacturing of metallic materials is most often carried out using expensive and complex tools that leave the user with limited control and no possibility of modification. In order to make the printing of metal parts more accessible to small structures but also better suited for academic research, the use of a mixture of thermoplastic polymer and metal powder is a good solution as many granular feedstocks already exist for Metal Injection Molding applications. To perform the shaping process, the Fused Granular Fabrication 3D printing technology is set up by diverting the use of a feedstock in the form of pellets that are directly inserted into the print head. This solution, which is less costly, is implemented here by modifying a mid-range printer, the Tool Changer from E3D, and by making the hardware and software adaptations to mount a compact granulates extruder on it, which is also available on the market. The polymer portion present in the green part can then be removed in order to perform the heat treatments that will densify the powder by sintering and give a fully metallic dense object.

This paper describes the relations between microstructure, mechanical properties, and electromagnetic behavior of carbon steel wires submitted to different thermomechanical treatments. The electrical resistivity and bulk magnetic properties are determined through resistivity measurements down to 2 K and magnetic hysteresis loop measurements. In addition, magnetic domains are imaged by magnetic force microscopy despite the complex microstructures. The electromagnetic properties are mainly related to changes in the volume fraction, morphology, and distribution of the cementite phase within the α-ferrite matrix. Electrical conductivity and magnetic permeability increase in the order of martensite, tempered martensite, pearlite, proeutectoid ferrite-pearlite, spheroidite, and ferrite microstructures. The increase in carbon concentration enhances the electrons localization at atomic sites, assisting the covalent character of Fe–C interatomic bonds and thereby reducing conductivity. Moreover, the α-Fe3C interfaces that act as a physical barrier for dislocation slip in ferrite, affecting also the main free-paths for conductive electrons and magnetic domain walls displacements within the materials. As the electromagnetic behavior of steels results from individual contributions of microstructural elements that are often intrinsically related to one another, a careful interpretation of both electrical and magnetic responses is critical for a proper application of quality and process monitoring methods of carbon steel wires.

This article deals with the modelling of iron losses due to the magnetic ageing of electrical steels used in energy conversion devices. This phenomenon is the consequence of irreversible mechanisms in the material which can be triggered by the operating temperature of electrical devices. At first, an experimental study is carried out at 180◦ C in order to assess the effect of isothermal ageing on electromagnetic properties of a magnetic steel sample. The results show that, during the thermal ageing, the hysteresis losses and the coercive field increase. These experimental observations, mainly caused by the formation of precipitates at the material microstructural scale, are then discussed. Considering the link between the effect of magnetic ageing on macroscopic magnetic properties (effect) and the microscopic precipitation (cause), the Johnson – Mehl – Avrami – Kolmogorov (JMAK) law describing the kinetics of precipitation was applied to model the time evolution of magnetic ageing. Once this approach was validated, it is proposed to integrate the JMAK law in the Steinmetz iron loss model.

Robustness and reliability of modern synchronous motors require an accurate design of the permanent magnets (PM) while accounting for the motor operating conditions (demagnetizing field, temperature). In this paper, the important attribute of a PM non-linear demagnetization model within a finite element method (FEM) simulation environment is clearly emphasized. To do so, starting from experimental measurement achieved on a NdFeB PM, a toolbox baptized “PM-Demag” has been developed. This toolbox manages the PM history and updates the PM B(H) characteristics depending on the temperature and the PM working point. Finally, a relatively straightforward coupling is implemented with a FEM software and applied to a simple study case. Results show local magnetization loss in the PM due to the combination of both the temperature and the demagnetizing field.

Regularly used in power transformers, grain-oriented (GO) steels are also usually chosen for the manufacturing of the stator cores of hydro and turbo-generators. These steels are renowned for their high magnetic performances in the rolling direction (high permeability and low magnetic losses). Nevertheless, in a turbo-generator where GO steels are employed to reduce the size of the stator core, the magnetic flux flows through several successive directions within the plane of the steel. So, the anisotropic behavior of the GO steel has to be considered in the design step of the related devices in order to improve their energy efficiency as well as their diagnosis based on modeling. In this paper, an anisotropic phenomenological iron loss model, quite recently developed, has been studied and successfully implemented in a finite element method (FEM) simulation environment. The implementation has been validated against experimental data achieved on an industrial conventional GO grade typically used in turbogenerators. The results show a good agreement of the computational results with the experiments for both quasi-static and dynamic regimes.

The purpose of this study is to investigate, through finite element (FE) simulations, the effect of the demagnetizing field in Epstein characterization of grain-oriented electrical steels. A 3D finite element simulation has been realized to represent the parallel and X-stacking configurations in the Epstein frame. The numerical results have been compared with experimental measures. In a parallel configuration, the measured induction is actually the one in the material, whereas the resulting magnetic field differs from the applied one (in magnitude and angle) due to the shape anisotropy (demagnetizing field). In X-stacking configuration, the resulting magnetic field is close to the applied magnetic field (and then the supposed excitation field in the Epstein frame), whereas the magnetic induction has deviated from the axis of the strips.

During electrical machine manufacturing, the process may induce plastic mechanical strains, especially in the magnetic core. However, magnetic properties are highly sensitive to the material mechanical state. Thus, the performances of electrical machines, which also rely on the magnetic material properties, are often deteriorated. This paper proposes an approach to reduce the impact of the forming process on the magnetic core performances by creating high localized heterogeneous deformations instead of having a low homogeneous deformation distributed on the whole structure. A NO (non-oriented) FeSi (1.3%) electrical steel (M330-35A) is characterized after uniaxial tensile test. Samples are deformed either in heterogeneous or in homogeneous ways while keeping the same global deformation. Experimental measurements show that, for the same displacement value, the heterogeneous configuration, with localized strain, deteriorates less the global magnetic properties than the homogeneous configuration. These results are supported by a magneto-mechanical modeling approach that predicts accurately the physical behavior of test samples.

This paper deals with the experimental investigation of the effect of impregnation process on the normal magnetization curve and iron losses of electrical steels. To address this issue, several laminated toroidal magnetic circuits have been designed to characterize the magnetic properties with the flux metric method. The first configuration considers magnetic circuits wrapped with adhesive tape so that the dielectric resin will be deposited only on the outer surface of the magnetic circuit. In the second configuration, the magnetic circuits are unwrapped, which will allow the resin to diffuse within the inter-laminar spaces of the magnetic circuit. The obtained experimental results show significant effects on the magnetic properties in both cases. However, depending on the considered configuration, the resin diffusion also has an influence on the changes in magnetic properties.

This paper presents a novel method for demagnetization fault detection in permanent magnet synchronous machine (PMSM). Demagnetization fault is a common problem existing in PMSM which deteriorates the machine performance and can lead to serious subsequential machine damages. Unlike the most popular method based on the analysis of the machine currents for detecting this type of fault, the approach proposed in this paper analyzes the voltage signal of a non-invasive search coil by means of Hilbert Huang transform. Simulations are carried out with a two dimensional finite element analysis (FEA) for different demagnetization levels to test the capability of the proposed method to detect PM demagnetization faults.

In this paper, the vector extension of the Jiles-Atherton hysteresis model is modified to predict both alternating and rotational field strength variations observed in a nonoriented silicon steel sheet. The model parameters are changed to be functions of the magnitude and direction of flux density, and the anhysteretic magnetic characteristics are identified from several unidirectional alternating measurements. We demonstrate that the modified vector Jiles-Atherton model can predict both alternating and rotational field strength variations with better accuracy than the “basic” approach.

In this paper, the magnetic ageing of a bulk forged non-annealed magnetic core, used in claw pole synchronous machine, is investigated. The study is carried out by characterizing the material properties of two groups of samples subjected to a thermal ageing at 180 °C that corresponds to the maximum operating temperature of the claw pole rotor. The investigated characteristics are the electrical conductivity, the magnetic properties, the material microstructure and the Vickers hardness. They were characterized along with the ageing time. The results show that, during the thermal ageing, the hysteresis losses and the Vickers hardness have been affected by the magnetic ageing, whereas the electric conductivity and the normal B-H curve have not been modified. The microstructure analyses showed that carbides precipitates were the main cause behind the magnetic ageing. Moreover, the comparison between the results of two groups of samples revealed the possibility that the magnetic ageing of the material could have started during the manufacturing process of the magnetic core.

The quality of a local physical quantity obtained by the numerical method such as the finite element method (FEM) attracts more and more attention in computational electromagnetism. Inspired by the idea of goal-oriented error estimate given for the Laplace problem, this work is devoted to a guaranteed a posteriori error estimate adapted for the quantity of interest (QOI) linked to magnetostatic problems, in particular, to the value of the magnetic flux density. The development is principally based on an equilibrated flux construction, which ensures fully computable estimators without any unknown constant. The main steps of the mathematical development are given in detail with the physical interpretation. An academic example using an analytical solution is considered to illustrate the performance of the approach, and a discussion about different aspects related to the practical point of view is proposed.

16MnCr5 steel parts were additively manufactured by laser powder bed fusion in order to investigate the effect of microstructure on electromagnetic properties. As process parameters have a direct impact on the obtained microstructure, different conditions were used to manufacture samples on which magnetic and electrical tests were conducted. The obtained results were presented and discussed in terms of density, microstructure and electromagnetic properties. Finally, correlations have been demonstrated between the microstructure and the electromagnetic performances. Lower magnetic and electric properties were obtained with the higher porosity rates at low volume energy density. The microstructural effects were evidenced, through a decrease in magnetic properties with grain orientation, and an improvement with stress relief annealing.

In this article, an experimental procedure is presented to handle magnetic measurements under uniaxial tensile stress reaching the plastic domain. The main advantage of the proposed procedure is that it does not require an additional magnetic core to close the magnetic flux path through the studied sample. The flux flows only in the sample, and no parasitic air gaps are introduced, thus avoiding the use of the H-coil to evaluate the magnetic field, which is often very sensitive and not easy to calibrate. A specimen of nonoriented FeSi (1.3%) sheet (M330-35A) is characterized under uniaxial tensile stress. To validate the proposed procedure, a comparison with the single sheet tester procedure is carried out. The results obtained by the two procedures are in good agreement. Moreover, to illustrate the possibilities offered by the proposed procedure, we confirm some results obtained in the literature. We show that the positive plastic strain leads to a significant degradation of magnetic behavior. An applied tensile stress on a virgin (unstrained) sample leads to a degradation of the magnetic behavior. However, on a pre-strained sample, an applied tensile stress results in reducing the deterioration caused by the plastic strain until a stress value called optimum is attained. Above this threshold, the magnetic behavior re-deteriorates progressively.

In this work, we investigate in Fe-Si laminations the core-loss coefficients variation with the flux density within the loss statistical approach framework. We find that the dynamical core-loss coefficients can be linked with the differential permeability defined from the low frequency normal curve. We interpret these variations as the fingerprint of the domain-wall activity (i.e. all the processes involving domain-wall movements, nucleation and anihilation) during the magnetization process. We show that the classical loss variation can be qualitatively described by the macroscopic formulation of the skin-depth, but not quantitatively.

During the operation of Claw Pole (CP) machines, and for some operating loads, the magnetic core temperature can reach 180°C in some hot spots. As a consequence, the core electromagnetic properties may considerably change, impacting the machine performances. In such a case, a deep knowledge of the electromagnetic behavior as a function of the temperature is required. In this paper, we present a dedicated study of the CP rotor made from a forged magnetic steel. In fact, the CP magnetic properties heterogeneity and the claw shape made it necessary to extract specific samples that are characterized with a miniaturized Single Sheet Tester (SST). To that end, this work proposes a specific methodology to characterize the electromagnetic properties of the CP rotor material as a function of the temperature in order to better predict the machine electrical performances, especially regarding the iron losses.

The manufacturing processes of electrical machines may lead to significant degradation of magnetic core properties and therefore of the machine performance. Laminations are usually stacked and pressed which affects the magnetic properties and the iron losses. However, the influence of this step must be still investigated when large generators are considered. Indeed, in that case, the stator and rotor stacking process consists in assembling several stacks of electrical steel sheets separated by airvents. The surface of the airvent spacers represents about ten percent of the lamination surface of the magnetic circuit, implying, during the compaction process, an inhomogeneous stress distribution with significant local stresses. The present work deals with the experimental characterization of a lamination stack, including airvents, under compressive stress in the thickness direction. A mock-up has been designed and built-up to study magnetic properties of lamination stacks under pressing conditions corresponding to the industrial process.

In this paper, we propose a method to identify the magnetostrictive behavior of electrical steel sheet submitted to a mechanical loading. The technique relies on the use of a magneto-mechanical model including the magnetostrictive phenomenon, namely the anhysteretic Jiles-Atherton-Sablik (JAS) model, and experimental macroscopic stress dependent magnetization curves. The method is illustrated with measured magnetization curves of a non-oriented (NO) electrical steel sheet under different stresses. Furthermore, the influence of a bi-axial mechanical loading on the magnetostrictive behavior is analyzed with the help of an equivalent stress.

In this article, the anhysteretic Sablik model is identified from measurements and implemented in a finite-element (FE) code. The model takes into account the effect of the plastic deformation through the dislocation density, and thus, enables to account for the degradation of the magnetic properties. A new model for magnetostriction is proposed and implemented in the Sablik model. Experimental data are used to identify the parameters of both Sablik model and proposed magnetostriction. Furthermore, the mechanical punching process of an electrical steel sheet is simulated in view of evaluating the plastic strain distribution near the punched edge. Based on the Sablik model and the simulated plastic strain, FE simulations are carried out on a steel sheet and a cage induction machine. The effect of the punching process on the distribution of magnetic-flux density and the magnetization current is analyzed.

We investigate the effect of magneto-mechanical and magnetocrystalline anisotropies in a test application by coupling a multiscale magneto-mechanical model with a finite element method. This first application is composed of a cylindrical conductor surrounded by a ring composed of a non-oriented FeSi 3 % steel sheet which contains 396 representative grain orientations. Such an application can reveal the anisotropy due to the texture of the material by inducing a rotational flux density within the ring. Moreover, the effect of the texture and the magneto-mechanical characteristic of the steel sheets is analyzed in an axially laminated synchronous reluctance machine. The effect of stress strongly emphasizes the anisotropic behavior of NO steel sheets.

An experimental approach is proposed to study the influence of the punching on the magnetic behavior of a stator core strips. Specimens of a non-oriented M330-A35 punched lamination sheet are picked up from a real manufacturing process. The proposed approach is based on the use of two types of specimens; one is a closed magnetic circuit while the second one is split into two parts. Magnetic measurements are performed on both types and compared with those made on specimens cut by WEDM which has a lower impact on the magnetic behavior. The specific purpose of this paper is to investigate the impact of punching in presence of an air gap that exists in electrical machines between rotor and stator. Therefore a dedicated device, optimized by FEM simulations, is developed in order to account accurately the air gap.

Claw pole machine performances are strongly related to the electromagnetic properties of ferromagnetic materials. These properties are impacted by the manufacturing processes, in a heterogeneous way, as well as by the thermal behavior of the machine and the mechanical stress distribution. Due to the complexity of CP geometry, extracted samples cannot respect the dimensions prescribed in international standards of electric and magnetic measurements. This paper proposes a specific methodology to characterize the electrical conductivity and the magnetic behavior of massive parallelepiped specimens extracted from different locations of a CP rotor.

High operating temperatures modify the magnetic behavior of ferromagnetic cores which may affect the performance of electrical machines. Therefore, a temperature-dependent material model is necessary to model the electrical machine behavior more accurately during the design process. Physics-inspired hysteresis models, such as the Jiles-Atherton (JA) model, seem to be promising candidates to incorporate temperature effects and can be embedded in finite element simulations. In this paper, we have identified the JA model parameters from measurements for a temperature range experienced by non-oriented electrical steels in electrical machines during their operation. Based on the analysis, a parameter reduction has been performed. The proposed approach simplifies the identification procedures by reducing the number of model parameters and does not require any additional material information, such as the Curie temperature. The resulting temperature-dependent JA model is validated against measurements, and the results are in good agreement.

Magnetic parts are usually composed of a stack of electrical steel laminations to reduce the eddy current losses. However, for cost reasons or for specific applications the magnetic core can be made from massive steel and thus manufactured with adapted processes such as forging. Such process may lead to inhomogeneous and degraded magnetic properties. Therefore, this study proposes a specific device for characterizing magnetic properties of samples which are to be representative of a massive part. The measure is based on the Faraday’s equation to determine the magnetic flux density and the Hall effect to estimate the magnetic field inside the sample. Practically this is realized with classical components such as Hall probes, a secondary winding and an electromagnet device. However their combination is unique to perform magnetic characterization on massive samples, which are less affected by the sampling technique and may have anisotropic properties. The device is dimensioned thanks to FE-Simulation and validated according repeatability, sensitivity and trueness analysis. Eventually the characterization is performed on samples with different material parameters showing the effect of the grain size on the specific losses. The expected effect of the grain flow on magnetic properties is however not proven yet.

This paper reports on performances of high permeability grain oriented electrical steel when used in association with power electronic switching devices. Loss measurement results obtained from the Epstein test, using sinusoidal or various PWM voltages in medium frequency range, show that for both studied thicknesses (HGO 0.23mm and HGO 0.18mm), comparing performances at a fixed induction level between the various situations may not be the most convenient method. The effect of magnetic domain refinement has been investigated. After having shown the interest of lowering the thickness, an alternative way of looking at losses is proposed that may help to design the magnetic core when it comes to the matter of reducing size in considering frequency and magnetization levels.

This paper deals with the calculation of iron losses in a turgenerator using a magnetodynamic Finite Element (F.E.) Analysis accounting for the eddy currents in the damper bars. Two iron loss models, based on the Berttoti’s decomposition approach, are compared in the post-processing step of a F.E. calculation. The numerical model of the studied system is validated by comparing the calculation and the experiment for no-load conditions.

This paper presents an efficient method to calculate the magnetic forces on bodies in contact. The forces are computed through the local application of the virtual work principle on degenerated air-gap elements. The results from this method are compared with those from other software and validated with measurements on a permanent magnet setup. Not only is this technique very accurate, but it also reduces the computational burden related to the problematic meshing of thin layers. The implementation of this method in an open source finite element software having facilities for higher order elements and parallel computation unlocks a cost effective and effectual platform for an electromechanical computation of electromechanical devices and magnetic materials.

The stray load losses in electrical machines represent a non-negligible contribution of the total losses and are a key point for an accurate evaluation of the energy efficiency of the considered device. In this paper, a methodology using the 3-D finite-element (FE) modeling approach and a posteriori loss calculation is presented for the estimation of the stray load losses. The case of a cage induction motor is investigated, and results are compared with the experiment. The simulation is performed at different load conditions using a 3-D FE model with external circuit coupling.

The performances of electrical machines depend highly on the behavior of ferromagnetic materials. In some applications, these materials operate under DC polarization, i.e. when the magnetic field oscillates around a DC bias. In that condition, it is required to know the incremental permeability which characterizes the magnetic behavior of the material around the operating point. In this paper, a non-destructive approach, involving a combination of experiment and Finite Element (FE) technique, is presented in order to determine the incremental permeability. The proposed sensor is based on the four-needles method. With this sensor, Bowler et al. have proposed a method to determine the initial permeability of homogeneous metal plates based on an analytical model. Here we propose to use the same kind of sensor to determine the incremental permeability. The measurement process is analyzed using a FE model. It is shown that the analytical approach reaches its limits if the permeability of the plate and its thickness become too high. A combination between the measurements and a FE model is introduced to overcome this difficulty to determine the incremental permeability. The study of two magnetic steel samples illustrates the interest of this method.

An improved dynamic hysteresis model is proposed for the prediction of hysteresis loop of electrical steel up to mean frequencies, taking into account the skin effect. In previous works, the analytical solution of the diffusion equation for low frequency (DELF) was coupled with the inverse static Jiles-Atherton (JA) model in order to represent the hysteresis behavior for a lamination. In the present paper, this approach is improved to ensure the reproducibility of measured hysteresis loops at mean frequency. The results of simulation are compared with the experimental ones. The selected results for frequencies 50 Hz, 100 Hz, 200 Hz and 400 Hz are presented and discussed.

The switching of the power semiconductors in static converters is the main source of electromagnetic interferences (EMI). To meet with Electromagnetic Compatibility (EMC) standards, it is necessary to reduce the level of the conducted emissions. This reduction can be achieved by different techniques including the EMI filters whose design is mainly based on the use of ring core inductors. This element is a key point for designing efficient EMI filters, requiring then accurate inductor high frequency (HF) models. Therefore, the present paper deals with the development of a HF behavioral model of inductors, based on electrical equivalent circuit, for an implementation in circuit simulation software. The aim is to provide a robust and adjustable model under small-signal operating conditions for frequencies up to 100MHz. The proposed model considers the frequency dependent properties of the magnetic core material and also includes the parameterization of the electrical equivalent circuit elements with the number of winding turns and dimension of the magnetic core. Simulations results using the obtained inductor model are validated by impedance measurements with two types of magnetic materials: Ferrite and Nanocrystalline

A framework for the finite element implementation of the formulas of local and global electromagnetic forces is presented. The theoretical framework, based on the Lie derivative, is applicable to 2-D and 3-D problems in the presence of arbitrary materials. The numerical properties of the proposed implementation, in terms of accuracy and convergence, are analyzed. An experimental setup is also presented for which accurate measurements have been carried out, and that can serve as a benchmark for the implementation.

The stray load losses (SLLs) in electrical machines represent a non-negligible contribution of the total losses and a key point for an accurate evaluation of the energy efficiency of considered device. In this paper, one aspect of these SLLs, the end-region leakage fluxes and losses, is investigated and considered for the case of a high-power cage induction motor. The study is performed at locked rotor, no-load, and rated load conditions using a 3-D finite-element modeling approach. The influence of the leakage flux on the end-region conductive parts of the motor is analyzed together with the eddy current loss calculation. Finally, the SLLs are calculated and compared with the experimental measurements based on the IEEE standard 112-method B test.

Two current probes are designed with the appropriate magnetic material in order to make impedance measurements in High Frequency (HF) using the Current Injection Method (CIM). These probes are then used to measure the common-mode impedance of power converters in real-operating conditions. The characterization of this impedance is required for a correct EMI filter design. In this paper, a simple formulation of the probe transfer impedance, based on S-parameters, is proposed. These probes allow improving the accuracy of impedance measurements in a wide frequency range, up to 100 MHz. The measured impedances of the power converter are then applied in the design of the common mode EMI filter under real operation conditions. The obtained insertion losses of the filter are finally compared with those measured under 50Ω-50Ω

The magnetic material when designing EMI filter determines the inductance value and the parasitic elements that influence the insertion loss effectiveness of the filter. Moreover, the EMI filter characterization is usually realized at low power levels (low current and low voltage). When the EMI filter is subjected to higher currents through its coils, the principal characteristics of the filter (inductance variation with current and frequency) are modified. To account for these variations in the design step, it is useful to take into account the hysteresis model that represents the inductive and dissipative effects. Therefore, in this paper, an approach combining a magnetic hysteresis model together with a concept of material capacitance is proposed. The model is identified from a single turn of flat copper ribbon (STFC) experimental setup. Then, the experimental data are modeled with the proposed hysteretic and capacitive material behavior model (HCM) that is implemented in an equivalent circuit modeling approach, accounting for both the magnetic behavior law together with the "material capacitance". The robustness of the proposed approach is evaluated by comparison and validation with the experiment results, showing good representation of the inductive and partially the dissipative effects

NdFeB permanent magnets (PMs) are widely used in high performance electrical machines, but their relatively high conductivity subjects them to eddy current losses that can lead to magnetization loss. The Finite Element (FE) method is generally used to quantify the eddy current loss of PMs, but it remains quite difficult to validate the accuracy of the results with complex devices. In this paper, an experimental test device is used in order to extract the eddy current losses that are then compared with those of a 3D FE model.

Classically the magnetic material models are considered with a deterministic approach. Nevertheless, when submitted to the fabrication process, the magnetic core properties are negatively impacted and may be subject to variability during the process. This variability can be of such importance that the performances of the final device (electrical machine) will also present a noticeable variability. The aim of this research is to develop a stochastic model of the magnetic behaviour law of slinky stators used in claw pole generators. The proposed methodology is general and can be applied to other physical properties of electrical devices.

When modeling a system subject to uncertainties, a fundamental aspect is the stochastic modeling of the input parameters of the model. Several calculation and analysis steps have to be considered, and can be found in the literature. In this paper, after presenting such steps, these are applied for the modeling of the variability of the magnetic behavior law related to a set of slinky stator samples, issued from the same production chain. The probabilistic model of the parameters is therefore validated using a statistical test and a classical Monte Carlo simulation. The importance of taking account of the dependency structure between the parameters is then emphasized, as it may modify significantly the results related to the validation of the model.

Permanent magnets are commonly used in electromechanical energy conversion devices, especially in permanent magnet synchronous machines (PMSM). When designing such devices, it is necessary to take account for the operating conditions of the permanent magnets. Ideally, the operating point of the magnet lies on a linear reversible demagnetization characteristic. Nevertheless, the operating conditions (temperature, demagnetization field, etc.) may have great influence on the magnetic characteristic that becomes strongly nonlinear and may lead to magnetization loss in the magnet. Consequently, the impact is also observed on the electrical machine performances. This paper presents a nonlinear model accounting for magnetization loss of permanent magnets which magnetic characteristic presents knee points in the demagnetization curve. The presented model is applied to analyze the local magnetization loss in magnets of a PMSM.

To take account of the uncertainties introduced on the soft magnetic materials properties (magnetic behavior law, iron losses) during the manufacturing process, the present work deals with the stochastic modeling of the magnetic behavior law B-H and iron losses of claw pole stator generator. Twenty eight (28) samples of slinky stator (SS) coming from the same production chain have been investigated. The used approaches are similar to those used in mechanics. The accuracy of existing anhysteretic models has been tested first using cross validation techniques. The well known iron loss separation model has been implemented to take into account the variability of the losses. Then, the Multivariate Gaussian distribution is chosen to model the variability and dependencies between identified parameters, for both behavior law and iron loss models. The developed stochastic models allow predicting a 98% confidence interval for the considered samples.

Short circuits in turbo-generator stators can lead to a modification of the magnetic flux distribution that impacts the performances and, in some extreme cases, can lead to local damage of the iron core. This work presents the modeling of short circuited laminations in a stator yoke of a turbo-generator. A 3D finite element (FE) model, associated to a homogenization technique, is used to calculate the short circuit current. The results are compared with the experiment, especially for the electrical signature of the diagnosis test known as Electromagnetic Core imperfection detector (El Cid).

Manufacturing processesmay introduce a significant variability on the magnetic properties of claw pole generator stators. The present work deals with the analysis of two groups of stator samples. The first group is composed of 28 slinky stators (SS) and the second group is composed of 5 stators, manufactured using laser cut stacked laminations (SL). Both groups are made from the same lamination grade and with the same geometrical dimensions. Characterization was carried out for several levels of excitation field at 50 Hz. A noticeable variability has been observed on the iron losses for SS samples, whereas it appears to be not significant for SL samples. The loss separation technique has then been investigated for the SS samples. Results show that the variability of static losses is more important than the one of dynamic losses.

The Non-Intrusive Spectral Projection (NISP) method is widely used for uncertainty quantification in stochastic models. The determination of the expansion of the solution on the polynomial chaos requires the computation of multidimensional integrals. An automatic adaptive algorithm based on nested sparse grids has been developed to evaluate those integrals. The adapted algorithm takes into account the weight of each random variable with respect to the output of the model. To achieve that it constructs anisotropic sparse grid of the mean, leading to a reduction of the number of numerical simulations. Furthermore, the spectral form of the solution is explicitly identified from the constructed quadrature scheme. Numerical results obtained on an industrial application in NDT demonstrate the efficiency of the proposed method.

This paper deals with a stochastic approach to model the pull-in voltage in a microelectromechanical system (MEMS) beam structure. Two nonintrusive stochastic techniques are used: a sampling method, based on Monte-Carlo simulations and a polynomial chaos expansion (PCE) approach. The deterministic model solves an electro-mechanical problem using a coupled 2-D finite element (FE) electrostatic and Euler–Bernoulli beam equation mechanical model. The influence on the pull-in voltage of three parameters subjected to uncertainty (material properties and shape) was investigated. Also, the advantage of the PCE method, compared to Monte-Carlo sampling method, was emphasized.

The perturbation method is a simple way to study local details while avoiding a fine mesh of the whole system. In this paper, we present the influence of the extracted region size, i.e. the region including the perturbation, when performing iterative calculations with the perturbation technique. This influence is illustrated using a simple example.

The torque developed by a magnetorheological brake can exhibit a hysteretic behaviour when experiencing a time varying magnetic field. In this work, we focus on the numerical study of such phenomenon using 2D Finite Element (FE) analysis. The torque evolution is investigated when considering successively nonlinear and hysteretic behaviour laws in the ferromagnetic parts.

The presented work is about the implementation of a vector hysteresis model in a Finite Integration Technique (FIT) calculation code. This is achieved in the magnetostatic case using the vector potential formulation and with the external electric circuit coupling. The used behavior law model is the vectorized Jiles-Atherton model with the magnetic flux density as input variable. The proposed approach is illustrated by modeling a coil made of Soft Magnetic Composite (SMC) magnetic core. Comparison with measured global quantities is also performed.

Inrush currents have undesired effects on transformers when these ones are, for example, switched into service. Theses effects have to be taken into account when designing a transformer, that leads to a constraint on its magnetic core and size definition. This paper investigates the modeling of inrush currents in a three phase transformer under sinusoidal voltage operation conditions. The transformer core is modeled taking into account the magnetic hysteresis including the anisotropy. Therefore, a Jiles-Atherton vectorized model is used for the nonlinear core modeling. The key advantage of this vector model is its reluctivity tensor which is appropriated for the Finite Element calculations in vector potential formulation. A time-domain simulation was carried out and the results were compared with experimental data for the procedure validation.

This paper presents a 2-D finite-element model to analyze the iron losses in a three-phase transformer. In this model, the effects of nonlinear core behavior are taken into account by means of a vector hysteresis model incorporated in the finite-element formulation by using a magnetic differential reluctivity tensor. The reluctivity tensor emerges naturally from the vectorized Jiles–Atherton model. The complete model includes eddy current losses and the anomalous losses. The magnetization currents are calculated and compared with the measured ones. Calculations of hysteresis loops at spotted points of the transformer are also performed. The comparisons between the iron losses measured and calculated with vectorial hysteresis, including the eddy current and the anomalous losses, are presented.

Closed form expressions for the computation of the pull-in voltage, can provide fast results within reliable accuracy, except when treating cases of extreme fringing fields. Finite Element based models come handy when high accuracy is needed. In the first model presented in this paper the FEM is used to solve the electrostatic problem, while the mechanical problem is solved using a simplified Euler-Bernoulli beam equation. The second model is a pure FEM model coupling the electrostatic and mechanical problems iteratively through the electrical force. Results for both scalar potential and vector potential formulations for the FEM models are presented.

This work proposes a modification in the Jiles-Atherton hysteresis model in order to improve the minor loops representation. The irreversible magnetization component is slightly modified keeping unchanged the other model equations and the model simplicity. Differently to other proposed methodologies found in the literature, the previously knowledge of the magnetic field waveform is not needed to assure closed minor loops. Measured and calculated hysteresis curves are used in order to validate the methodology.

In this work an approach for modeling a transformer core taking into account magnetic hysteresis is presented. For this purpose, the inverse vector Jiles-Atherton hysteresis model is incorporated in a 2D finite element code. This model allows writing naturally the differential reluctivity tensor which can be directly used in the magnetic field equations. A three-phase transformer is modeled. The excitation characteristics of the transformer, as well as hysteresis loops at specific points, are presented. The proposed model was verified with obtained experimental data.

Coreplates in large generators may suffer from local short circuits. An accurate analysis is required to avoid these failures and detect them when occurring. The purpose of this paper is to develop a lamination stack model compliant with interlamination default analysis.

Although the original Jiles-Atherton (J-A) hysteresis model is able to represent a wide range of major hysteresis loops, in particular those of soft magnetic materials, it can produces non-physical minor loops with its classical equations. The purpose of this paper is to show a modification in the J-A hysteresis model in order to improve the minor and inner loops representation. The proposed technique allows the J-A model representing non-centred minor loops with accuracy as well as improving the symmetric inner loops representation.

Abstract: When modelling electrical devices, one has to estimate quite accurately the iron losses for the sake of efficiency. The use of non-sinusoidal electrical sources increases the harmonic content in electrical systems and, consequently, increases significantly the magnetic losses in devices feed by these sources. The harmonic content adds non centred minor hysteresis loops over the classical major one. The numerical tool used for the material modelling must be able to represent the magnetic behaviour in such conditions. Then, the use of a hysteresis model is the more suited solution, but the chosen model has to take into account correctly the minor loops. The Jiles-Atherton hysteresis model is one of the most employed, due its well known properties, but it is not able to represent closed minor loops. In this work, we propose a simple approach based on experimental observations and empirical considerations, to improve the representation of minor loops in this model by keeping its simplicity of use and implementation in a FE calculation code. Differently to other approaches found in the literature, the previously knowledge of the magnetic field evolution is not needed. A comparison between measured and calculated curves, as well with the Preisach model, is performed to validate the model.

This work deals with the implementation of a vector hysteresis model in a 2D finite element code with vector potential formulation. The inverse Jiles-Atherton hysteresis model leads to obtain a differential reluctivity tensor which can be directly applied to the field calculation equations.

Rare earth permanent magnets are very sensitive to temperature as an overheating can leads to a partial or a total demagnetisation. It is then necessary to determine the losses in the permanent magnets to design with accuracy an electromagnetic system. In fact, if the permanent magnet experiences a high frequency magnetic field, significant losses appear. In the literature, these losses are calculated assuming the permanent magnet to be a bulk conductive material. In this work, we aim at verifying this assumption and we give a method to determine the equivalent conductivity. Then, we present a comparison between calculated and measured characteristics of two permanent magnets samples.

The accuracy of the magnetic field strength estimation in rotational single sheet tester is investigated with the finite element method and measurements. The incorporation of a vector hysteresis model, derived from the original scalar Jiles-Atherton model, in a finite element magnetic field code is performed. The application of this method leads to use the differential reluctivity tensor that arises naturally from the vector model. The effect of the shielding on a Rotational Single Sheet Tester is analyzed in order to improve the field homogeneity in the sample area.

Résumé - Mechanical stress can heavily affect the magnetic behaviour law in ferromagnetic materials. This paper, aims to take into account the effect of mechanical stress into a hystreresis model. This model is implemented in a finite element analysis code and tested in the case of a simple system.
A simple extension of the classical Preisach model is proposed, in which a function linked to the Preisach density is parameterized using the mechanical stress as a supplementary parameter. The methodology is based on experimental measurements for identifying the required function. As a first approach, a linear interpolation is used between the measurements in order to have a continuous evolution of the magneto-mechanical behaviour. This model has been tested in the case of a steel sheet in which width is not constant in order to obtain a non-uniform distribution of stress and magnetic flux density.

Résumé - In this paper, we present a model of a hysteresis motor based on Maxwell’s equations coupled with the Jiles-Atherton (J-A) hysteresis model solved by the finite element method. The aim of this work is to validate such a model by comparison with the experimental results (electromagnetic torque, voltage, current). We also present an analysis of this motor when imposing current or voltage in the 2D vector potential formulation.

Résumé - In this communication, the Preisach and Jiles-Atherton models are studied to take hysteresis phenomenon into account in finite element analysis. First, the models and their identification procedure are briefly developed. Then, their implementation in the finite element code is presented. Finally, their performances are compared with an electromagnetic system made of soft magnetic composite. Current and iron losses are calculated and compared with the experimental results.

Résumé - In this communication, we propose a dynamical model of hysteresis giving the magnetization M in function of the flux density B. The mathematical development is based on the Jiles approach for frequency dependent hysteresis. The obtained model is simple to carry out and fast. The model is tested through a comparison with experimental results on FeSi steel sheets. Then, the accuracy and the range of application of the model are discussed.

Résumé - In electrical engineering, study and design of electromagnetic systems require more and more accurate models. To improve the accuracy of field calculation code, hysteresis phenomenon has to be taken into account to model ferromagnetic material. This material model has to be accurate and fast. In that context, two macroscopic models are often used: the Preisach and the Jiles–Atherton (J–A) models.
In this paper, both models are presented. Field calculation requires a model giving the magnetization M versus either the magnetic field H or the magnetic flux density B. Consequently, from the classical Preisach and J–A, two sub-models M(H) and M(B) are deduced. Then, we aim at comparing these models in terms of identification procedure facilities, accuracy, numerical implementation and computational effort. This study is carried out for three kinds of materials, which have different magnetic features: ferrites, FeSi sheets and a soft magnetic composite material. Then, the implementation of these models in a finite element code is presented. As example of application, a high-frequency transformer supplied by a rectangular voltage is studied.

For some specific industrial applications, such as large generators, once the magnetic circuits are built and wound, they are usually impregnated with a dielectric resin, which is polymerized under heat treatment, to ensure insulation, thermal and mechanical properties. This talk is about the experimental study of the effect of such impregnation process on the magnetic properties of electrical steels used for the manufacture large generator stators.

In this research, we propose an ad hoc method for identifying adequate full permeability tensors for finite element method (FEM) simulation of grain oriented electrical steels (GOES). The tensors are obtained from dedicated measurements requiring only unidirectional excitation field. This method relies on the one hand, on the Enokizono approach which was originally established based on measurements under rotating field and on the other hand on the Fiorillo model of magnetization processes in GOES.

In this research, the magnetic behavior of a lamination stack made of grain-oriented electrical steel (GOES) is investigated under non-conventional 3D magnetic flux excitations. An experimental prototype has been designed to study different orientations of the magnetic flux path, with regard to the lamination plane, combined with different in-plane orientations of the GOES easy magnetization axis.

In this work, we propose to characterize and analyze the phenomena involved by an industrial impregnation process that degrades the magnetic properties (B-H curve, iron losses) of electrical steels. Two main aspects are considered: the thermal effect as well as the dielectric resin deposition and diffusion within the magnetic circuit.

This paper presents a combined experimental/numerical approach to identify the degradation profile of the magnetic characteristics regarding the distance from the cut edge of punched electrical steels. Using a dedicated magnetic measurement device and mechanical hardness measurements, the impacted cutting-edge (I.C-E) distance has been experimentally identified. In association with a magneto-plastic model, the numerical model allows to determine the I.C-E distance and its associated degradation profile by an inverse optimization method.

During the operation of electrical machines, the increase in temperature up to about 200 °C promotes, in some electrical steels, basically Fe-Si alloys, the formation of precipitates (carbides, nitrides…). This precipitation causes a deterioration of the magnetic properties, in particular an increase in iron losses, a phenomenon known as magnetic ageing [1]. The aim of this study is to develop a preliminary multi-physical and multi-scale modelling approach coupling precipitation kinetics and the evolution of magnetic losses due to magnetic ageing.

Electromagnetic non-destructive testing (NDT) of industrial steels is mostly employed to detect defects such as cracks or mechanical properties inhomogeneities. However, NDT can also be employed, when properly calibrated, to evaluate quantitatively these mechanical properties. It is especially of interest when rigorous quality testing must be achieved on finished steel-based products of which mechanical characteristics must be guaranteed. In that context, the proposed work deals with the evaluation of electromagnetic NDT to characterize the tensile properties of high mechanical performance steels.

Fabrication of soft magnetic ceramic materials relies on time consuming conventional methods, such as molding and sintering, which restricts the possibilities of shapes the components can be given. Additive manufacturing of such materials can help reduce production lead time and unlock topological design limitations. In this work, the implementation of an indirect additive manufacturing methods for soft magnetic Mn-Zn ferrite, intended for high frequency applications, is presented. A blend of light sensitive polymer binder and fine powder is used for the shaping stage using Digital Light Processing (DLP) followed by a heat treatment that allows to remove the polymer part and to obtain a final dense part. Simple shapes were produced in order to characterize their magnetic performances and to validate this method for further fabrication of more complex magnetic core.

The performance and energy efficiency of electro-mechanical converters are strongly bound to the properties of their magnetic cores. The latter are mostly made from stacked laminations of soft magnetic materials such as Fe3%Si which limits the core geometry design. However, when complex geometries are required, usually forging processes may be employed but with very low silicon steels (<0.5%) to be able to forge the steel. In that case, the low silicon content yields to higher electrical conductivity and then to higher eddy current losses. In this work, an additive manufacturing technique allowing to build complex geometries is studied with Fe3%Si magnetic materials. The fabrication process allows to obtain green parts which are then densified through a final sintering step. The electromagnetic characterization of samples is performed. Finally, the results and possible improvement will be discussed in comparison with conventional Fe3%Si electrical steels and a forged magnetic steel that is commonly found in electromechanical applications.

Magneto-optical (MO) analysis is a powerful tool to reveal the magnetization processes in magnetic materials at all relevant scales. Because the magnetization processes involve the restructuration of the magnetic domain structure (domain-wall nucleation, annihilation, and propagation, etc.), MO studies are of prime importance to link the material microstructure to its basic macroscopic properties (e.g., magnetic losses) and then improve the knowledge of these properties and their modelling. In this work, we propose a MO investigation of the magnetic domain structure evolution under rotating magnetic field.

In this work, we propose an FDM additive manufacturing process that uses a feedstock in the form of small pellets composed of a similar mix of 316L Stainless Steel powder bound by a thermoplastic polymer. The printing stage is performed using an affordable Archimedes screw system that is mounted on a classical 3-axis cinematic frame. The feedstock, provided by PolyMIM, is diverted from its original use, which is Metal Injection Moulding (MIM), and is intended to be debinded and sintered. This allows to consider a wide range of materials already available. The impact of the deposition strategy on the tensile properties will be investigated in relation with the microstructure.

In this paper, a toolbox baptized “PM-Demag” taking into account the permanent magnet (PM) demagnetization phenomenon has been developed. It is based on a nonlinear demagnetization model which considers the thermal state of the PM and reproduces the knee rounded shape of the B(H) curve. Validations against experimental measurements performed on commercial NdFeB PM are presented.

Grain-oriented (GO) materials are widely known for their strong anisotropic behavior. Their magnetic characteristics depend on the angle between the applied magnetic field and rolling direction (RD). However, these characteristics can be further modified according to their stacking configuration and to the influence of the demagnetizing field. In this paper, a 3-D finite element analysis is performed in order to study the effect of the parallel and x-stacking configuration on the magnetic properties of the lamination stack. The results are interpreted in terms of the demagnetizing field which vectorially combined with the applied field affects the magnetization.

This study presents a device to handle magnetic measurements under uniaxial tensile stress reaching the plastic domain. The proposed device does not require external magnetic core to close the magnetic flux loop through the studied sample. The flux flows only in the sample and no parasitic gaps are introduced which avoids the use of H-coils to evaluate the magnetic field, often very sensitive and not easy to calibrate. Two geometries of a non-oriented (NO) FeSi (1.3%) sheet (M330-35A) are characterized under uniaxial tensile stress. The magnetic hysteresis loop was measured at 50Hz. Results show that positive plastic strain results in significant degradation of the magnetic behavior. An applied tensile stress on a virgin (un-strained) sample leads to magnetic behavior degradation. Whereas, on a pre-strained sample, an applied tensile stress, leads to reduce the deterioration performed by the plastic strain until a stress value called optimum. Above this optimum value, the magnetic behavior re-deteriorates progressively.

We investigate the effect of magneto-mechanical and magneto-crystalline anisotropy in a test application by coupling a multiscale magneto-mechanical model with a finite element method. This test application is composed of a cylindrical conductor surrounded by a ring composed of a non oriented FeSi3% steel sheet which contains 396 representative grain orientations. In the final paper, the analysis of magneto-mechanical anisotropy due to the texture of the steel sheet will be carried out for an electrical machine.

In this work a simulation of the effect of punching process on the magnetic properties of electromagnetic device is presented. The anhysteretic Sablik model is identified from measurements and implemented in a finite element code. A new model for magnetostriction is proposed. A mechanical punching process is simulated using the software ABAQUS, the plastic strain distribution near the punching edge is evaluated. The effect of punching process on the distribution of magnetic flux density and the magnetization current in an induction machine is analyzed.

This paper focuses on the torque optimization of a high speed Spoke-type interior permanent magnet (IPM) machine for automotive powertrain application. The optimization target is to balance the torque performance at low speed and durability of rotor strength at maximum speed. Firstly, torque and mechanical centrifugal force analysis using 2-D finite element method (FEM) are established to obtain the objectives and constraints. Secondly, metamodeling techniques including different kind of design of experiment (DOE) and meta-models are used to construct the design space, objective functions and constraint functions. Comparison of metamodeling techniques is carried out and engineering guidelines on selection for electric machine design optimization are given. Finally, some different optimization methods are applied on the meta-models to determine the optimal design.

This paper presents a novel method for demagnetization fault detection of per-manent magnet synchronous machine (PMSM). Demagnetization fault is a common problem existing in PMSM which deteriorates the machine performance and can lead to serious secondary machine damages. Unlike the most popular method for detecting this fault which is based on the analysis of the machine current, the approach proposed in this paper analyses the voltage signal of a non-invasive search coil by means of Hilbert Huang transform. Simulations are carried out with a two dimensional finite element anal-ysis (FEA) for different demagnetization levels to verify the proposed method.

The manufacturing of a slinky stator core is the result of a sequence of difference processes: straightening, punching, rolling It has been shown in the literature that manufacturing processes lead to a degradation of the magnetic properties. However, it is really difficult from the state of art to classify them a priori from the most influent to the less. In order to determine the most influent processes, it is necessary the evaluate quantitatively the impact of impact of each process. In this paper, a campaign of magnetic characterization is carried out on FeSi 1.3% specimens extracted after each process on the manufacturing line of a slinky stator. Samples have different shapes, so different characterization methods were used to determine the normal curves and total losses. Results show that the dispersion in raw material is quite important and depends on the level of induction. Straightening and training processes deteriorate the magnetic material properties and dispersion after both processes is higher than the raw material one. The effect of rolling and cutting are the most harmful compared to the other manufacturing processes, while the compacting process shows a benefic effect.

This paper presents an efficient method to calculate the magnetic forces on bodies in contact. The forces are computed through local application of the Virtual Work principle on degenerated airgap elements. The results from this method are compared with those from another software and validated with measurements on a permanent magnet setup. Not only is this technique very accurate, but also reduces the computational burden related to the problematic meshing of thin layers. The implementation of this method in an open source finite element software having facilities for higher order elements and parallel computation unlocks a cost effective and effectual platform for electromechanical computation of electromechanical devices and magnetic materials.

The stray load losses in electrical machines represent a non-negligible contribution of the total losses and are a key point for an accurate evaluation of the energy efficiency of the considered device. In this paper, a methodology using the 3-D finite element (FE) modeling approach and a posteriori loss calculation is presented for the estimation of the stray load losses. The case of a cage induction motor is investigated and results are compared with the experiment. The simulation is performed at different load conditions using a 3-D FE model with external circuit coupling.

Common characterization methods may not be adapted for specific applications, such as the study of massive magnetic parts. In this paper a specific procedure taking into account possible stress relieving when sampling as well as material anisotropies is presented, the design being supported by numerical simulation.

The magnetic properties of ferromagnetic cores and the resistance of conductors are severely affected by the high operating temperatures in modern electrical machines. These temperature effects must be taken into account in the electrical machine design process to optimize their performance. In this work, we have proposed a simple material model to predict the change in the single-valued B-H relationship of non-oriented electrical steel with respect to the temperature. The temperature dependent power loss curves have also been measured and are fitted to a two term iron loss formula to compute the magnetic losses. The temperature dependent magnetic properties (B-H relationship and power loss formula) and the resistivity values of the conductors have then been incorporated into the Finite Element (FE) based computer simulations of a transformer core and an induction machine. The effects of temperature on different performance parameters, such as magnetic and copper losses and supply current have been studied.

High operating temperatures modify the magnetic behavior of ferromagnetic cores which may affect the performance of electrical machines. Conventionally, in CAD simulations, iron losses are computed using models in which the temperature dependency is completely neglected. Therefore, a temperature dependent material model is necessary to model more accurately the electrical machine behavior during the design process. In this communciation, an approach to include the temperature effect in the Jiles-Atherton hysteresis model is proposed.

For electromagnetic applications the microstructure and the final mechanical state are key parameters. These can be obtained by a judicious choice of the material, a particular design like laminated steels but also through the determination and the mastering of the fabrication process. This present paper contains a brief introduction to electromagnetics and the qualification of a “good” electromagnetic quality. Then the article highlights, based on literature, first the influence of the process parameters on microstructure, mechanical state and secondly the impact these properties themselves on magnetic properties. Eventually, a methodology is proposed in order to predict the functional behavior of a part in its final system, taking into account its manufacturing process. The academic study case presented here can illustrate such a methodology. This kind of methodology includes in particular experimental tests, physical analysis and numerical modeling.

Electromagnetic losses in permanent magnet synchronous motors (PMSM) occur in the laminated core as well as in the permanent magnets (PM). These losses can lead to an overheating of the PMs that are subject to magnetization loss. Due to the difficulty of distinguishing experimentally the iron losses in the laminations from the eddy current losses in the PM, it is necessary to resort to the simulation. In this work, the losses of a PMSM, fed by a PWM inverter, are investigated using the 3-D FEM. The PWM measured signal is imposed, using a linear interpolation and respecting the harmonic content, as an input of the simulation.

Ring core inductors (RCI) are widely used as filter components for electromagnetic interferences (EMI) mitigation. In order to design these filters with accuracy, a behavioral model of the RCI, based on an equivalent electrical circuit, is proposed. This model takes into account the frequency-dependent impedance of ferrite and nanocrystalline RCI. The main contribution in this model is the inclusion of the capacitive behavior (dielectric behavior) of the ferrite material, the skin effect in the nanocrystalline material and the parameterization of the electrical equivalent model by the number of turns of the coil. The proposed Behavioral Ring Core Inductor (BRCI) model is simulated and verified with experimental measurements

The stray load losses represent a non-negligible contribution to the total losses in electrical machines. This paper investigates a contribution to these losses in the case of a non-skewed squirrel cage induction motor, namely the zig-zag flux. The study is performed at no-load, locked-rotor and load conditions for an induction machine with different rotor slot openings, using a time stepping 3-D finite element modeling approach. The discrete Fourier transform is used to analyze the magnetic flux density waveforms in the air gap and deduce the main harmonics related to the zig-zag flux. The influence of the rotor slot opening on the zig-zag flux and core losses, in both rotor and stator, are discussed.

The stray load losses in electrical machines represent a non-negligible contribution of the total losses and are a key point for an accurate evaluation of the energy efficiency of the considered device. In this paper, one aspect of these stray load losses, the end-region leakage fluxes and losses, is investigated for the case of a high power cage induction motor. The study is performed at locked rotor condition using a 3-D finite element (FE) modeling approach. The influence of the leakage flux on the end-region conductive parts of the motor is analyzed together with the eddy current loss calculation.

NdFeB permanent magnets (PM) are widely used in high performance electrical machines but their relatively high conductivity subjects them to eddy current losses that can lead to magnetization loss. Finite Element (FE) method is generally used to quantify the eddy current loss of PM but it remains quite difficult to validate the accuracy of the results with complex devices. In this paper, an experimental test device is used in order to extract the eddy current losses that are compared with those of a 3D FE model.

Two current probes, based on the current injection method, are designed with appropriated high frequency magnetic material. These probes are used to measure the common-mode impedance of power converters in real-operating conditions. The characterization of this impedance is of importance for the EMI filter design. In this paper, a simple formulation of the probe’s transfer impedance using S-parameters is proposed. The proposed probe allows improving the accuracy of the impedance measurement in a wide frequency band up to 100 MHz. Different measurements of common-mode configurations are detailed and discussed.

This paper presents a study on iron loss estimation for a solid rotor induction motor fed by Pulse Width Modulated (PWM) supply. The iron losses are often determined using an a posteriori method that can lead to more or less important deviations, compared with measurements, depending on the used models and implementation techniques. The methodology proposed here consists in computing the iron loss with an analytical method implemented in a post-processing of a 2D finite-element analysis. Different implementation techniques are used in order to investigate the impact of the model on the total iron loss.

NdFeB permanent magnets are widely used in electromechanical energy conversion devices, especially in high performance electrical machines. When designing such devices, it is necessary to take account of the operating conditions of the permanent magnets. Ideally, the operating point of the magnet lies on a linear reversible demagnetization characteristic. Nevertheless, the operating conditions (temperature, demagnetization field …) may have great influence on the magnetic characteristic that becomes strongly non-linear and lead to irreversible magnetization loss. To study such effect, the Finite Element (FE) method can be used in order to describe with accuracy the local demagnetization loss of a permanent magnet (PM). Therefore, the present work deals with the nonlinear modeling of a PM implemented in a 3D FE model that takes into account the partial demagnetization effects with temperature dependencies.

This communication addresses the modelling of the parameter known as the pull-in voltage in electrostatic MEMS (Micro Electro Mechanical System). As this parameter is sensitive to the physical parameters of the MEMS device, a stochastic modelling approach may be required. Two non-intrusive stochastic techniques are used: a sampling method based on Monte-Carlo simulations and a Polynomial Chaos Expansion (PCE) approach. The electro-mechanical problem is solved using the coupling between a 2D Finite Element (2D-FE) electrostatic model and the Euler-Bernoulli beam equation for the mechanical model. The influence on the pull-in voltage of three parameters subjected to uncertainty (material property and geometry) is investigated.

When modeling a system subject to uncertainties, a fundamental aspect is the stochastic modeling of the input parameters of the model. In this work, this aspect is emphasized by modeling the variability of the magnetic behavior law related to a set of stator samples. The identified probabilistic model of the parameters is tested using a Monte Carlo simulation. The importance of taking account of the dependency structure between the parameters is also emphasized

Industrial processing (cutting, assembly…) of steel laminations can lead to significant modifications in the magnetic properties. Moreover, the repeatability of these modifications is not always verified because of the tool wear or, more intrinsically, to the manufacturing process itself. When investigating the iron losses, it is generally shown that the hysteresis loss contribution is more likely to be affected. In the present work, twenty eight (28) samples of slinky stator (SS) are investigated, at a frequency of 5Hz. A stochastic model is then developed, using the Jiles-Atherton model together with a statistical approach to account for the variability of the hysteresis loops

This paper investigates the stochastic post-processing calculation of iron losses. Twenty eight slinky stator samples are investigated in term of iron losses variability, and stochastic model is then developed to take account of this variability. The Multivariate Gaussian distribution (MG) of the iron losses parameters is thereafter used for stochastic post-processing calculation of the density of iron losses of a PMSM, with Monte Carlo simulation method. This approach allows one to take in consideration the magnetic core variability from the iron loss point of view, for the design of electrical machine.

Pulse width modulated (PWM) inverters are widely used to feed induction motors for variable speed applications. The use of PWM power supplies induces additional magnetic losses in the magnetic circuit of the electrical machine. In this paper a novel analytical approach is presented to account for these losses. The methodology proposed here consists in identifying the analytical method with a static Preisach hysteresis model. The Preisach model was validated by comparing it with measurements obtained from an Epstein frame. Then, the results obtained with this approach were compared with a basic analytical method that is widely used.

Permanent magnets (PM) are widely used in various types of electrical machines and devices. However, they can be subjected to magnetization loss depending on the operating conditions. Therefore, when modeling devices involving PM, it can be useful to use an accurate description of the magnetic behavior law of the PM in order to predict any demagnetization that will impact their performances. Usually, the Finite Elements (FE) approach is used in order to describe with accuracy the magnetic operational conditions of the PM devices. These conditions depend of the magnet temperature and also of the spatial and temporal harmonics of the magnetic field developed in the PM [1]. The magnetic behavior law of PM is generally assumed to be linear. The real demagnetization curve can also be taken into account by implementing a non-linear behavior law. Nevertheless, the magnetization loss is not always taken into account, especially when the operating point of the PM reaches the knee point. Therefore, in this communication, a model describing the modification of the behavior law of a PM is described in this condition. The model is implemented in a FE calculation code with an example of application.

The passive magnetic ferrite components used in EMI filters have a complex magnetic permeability (CMP) which varies with frequency. The CMP in frequency range from 150 kHz to 30MHz is not given by manufactures. Moreover, measurement techniques require some specific size and shape of sample to measure CMP of ferrites. Common application of these passives components are EMI filters, where toroid ferrite cores need to be characterized to determine the insertion loss function. In this paper a CMP measure procedure is proposed. The leakage inductance and parasitic capacitance of an inductor are determined. Then, a rational function approximation (RTA) is applied to represent the HF equivalent impedance of CMP.

Iron losses during electromechanical energy conversion devices are crucial in electrical machine design. They are often determined using an a posteriori method that can lead to more or less important deviations with regard to the experiment. These deviations can be explained both by the lack of accuracy of the iron loss model but also by the numerical modeling procedure and hypothesis. This paper investigates the impact of the numerical error on the evaluation of iron losses in an electrical machine stator.

Short-circuits in turbo-generator stators can lead to a modification of the magnetic flux distribution that impact the performances and, in some extreme cases, to local damage of the iron core. This work presents the modeling of short-circuited laminations in a stator yoke of a turbo-generator. A 3D finite element (FE) model, associated to a homogenization technique, is used to calculate the short-circuit current. The results are compared with the experiment, especially for the electrical signature of the diagnosis test known as Electromagnetic Core imperfection detector (El Cid).

When ferromagnetic materials are subject to a time varying magnetic flux, energy dissipation, known as iron loss, occurs within the material. These losses are often determined using an a posteriori method that can lead to more or less important deviations depending on the used method. In electrical machines, one has to take into account the vectorial behavior of the magnetic field that can lead to additional losses. In this work, two iron loss calculation approaches, implemented in a post processing of a 3D finite-element analysis, are used in order to investigate the impact of rotational losses in a three-phase transformer.

This paper deals with the modelling of a lamination stack, crossed by a conducting building bar, in the presence of an inter-lamination short-circuit. Under a timevarying magnetic flux, an induced current loop flows through both the building bar and the fault. To reduce computational times, a homogenization technique is used to model the lamination stack. Eddy current losses and total magnetic energy values are compared for cases with and without homogenization for 50 Hz and 100 Hz.

This paper presents a simple model to simulate the currents in a transformer, especially during the transient state. The model is based on a reluctance circuit using a finite element (FE) tool for identifying the global behaviour laws of the transformer iron core. A three-phase three-limb transformer is modelled to test the proposed approach.

The aim of this work is to study, using a statistical approach, the macroscopic behavior of a given number of anisotropic laminations, stacked randomly.

In this paper we compare different approaches for the lamination stack homogenization with a short-circuit due to an electrical fault between several sheets. The presented techniques are based on the determination of a complex equivalent magnetic permeability for the homogenized domain. The eddy current losses are calculated in the homogenized lamination stack and in the fault. These losses are compared with those obtained from a reference system where the lamination is modeled with its real geometry.

The perturbation method is a simple way to study local details while avoiding a fine mesh of the whole system. In this paper, we present the influence of the extracted region size, i.e. the region including the perturbation, when performing iterative calculations with the perturbation technique. This influence is illustrated using a simple example.

This paper presents a modification of the Jiles-Atherton hysteresis model in order to improve the minor loops representation. Only the irreversible magnetization component is slight modified keeping unchanged the other model equations and the model simplicity. Comparison between measured and calculated curves is performed to validate the methodology.

In this paper we present an experimental and numerical study rotational single sheet tester. We focus on the effect of the shielding sheet distance which influences the measured magnetic field by H-coil.

La réduction des pertes fer dues au vieillissement magnétique des aciers doux est une voie d’optimisation de l’efficacité énergétique des machines électriques telle que recommandée par l’union européenne. Le vieillissement magnétique se traduit par une détérioration des propriétés magnétiques lors du fonctionnement de la machine électrique, ce vieillissement est lié à la formation de précipités de carbures ou nitrures à la température de fonctionnement (inférieure à 180°C). Cette étude propose un travail préliminaire dans le développement d’un modèle multi-physique et multi-échelles afin d’évaluer l’évolution des pertes fer pendant les cycles d’utilisation des machines électriques.

In this paper, a surrogate model base on deep learning (DL) is proposed to predict the hysteresis loops of ferro-magnetic materials. The databases of hysteresis loops were measured on the MPG200D Brockhaus equipment with an Epsteinframe. In order to reduce the experimental cost and accelerate measurements, a surrogate model based on the convolutional neural network (CNN) is proposed. First, presenting the measurement results in the form of 256× 256 × 1 images and extract the 6 most characteristic parameters, namely peak magnetic flux density, frequency, maximum magnetic field strength, remanence, coercivity, and the area of the hysteresis loop. All these physical parameters are taken as the label in the supervised DL process. These labe linformation are normalized to form a Gaussian distribution image of 256× 256 × 3 as the input, and the corresponding B-H curve is the output. Using image-to-image CNN U-net, once the network is effectively trained, the hysteresis loops under other excitation parameters can be predicted without further measurement. Our numerical examples show that the prediction results agree well with the measurement results. The sensitivity of CNN for hysteresis loops prediction with respect to the hyperparameters are investagted. A set of empirical hyperparameter configurations isput forward to guarantee an efficient convergence. This research shows that the proposed approach can be an efficient tool to predict the hysteresis loop of ferromagnetic materials under different circumstances, which can potentially contribute to nonlinear hysteresis FEM computation.

La roue polaire des alternateurs à griffes est une pièce magnétique massive issue d’un processus de fabrication impactant pour les propriétés magnétiques du matériau. L’une des pistes d’amélioration des performances des alternateurs est la maîtrise des paramètres du processus de fabrication pour en réduire l’impact. Ceci passe nécessairement par l’identification du lien entre les procédés et les propriétés microstructurales et mécaniques du matériau. Ensuite, ces propriétés sont à leur tour mises en lien, par le biais de caractérisations, avec les propriétés magnétiques du matériau.

Une méthode de mesure combinant une démarche opératoire et la simulation par éléments finis est développée afin de caractériser la conductivité électrique locale de pièces massives. A l’aide d’un diagramme 5M (ou diagramme d’Ishikawa), une démarche d’optimisation de la méthode a été entreprise.

B. AHMADA, F. ALVES, B. BEN ABDALLAH, Abdelkader BENABOU, Y. BERNARD, F. BOUILLAULT, J.P. CHABRERIE, S. CLENET, M. FELIACHI, A. LEBOUC, J.P. MASSON, E. MENDES, G. MEUNIER, A. NOURDINE, Y. OULED AMOR, F. PIRIOU, Y. SEGUI.

L'invention concerne un procédé de détermination des propriétés électromagnétiques d'un matériau magnétique, au moyen d'un dispositif comportant deux pointes de mesure et deux pointes excitatrices, et un capteur de champ placé à proximité dudit matériau, caractérisé en ce qu'il comporte les étapes suivantes : - l'application d'une polarisation magnétique H1 au matériau par un moyen de polarisation, - une imposition d'un signal d'excitation de courant i sur le matériau par l'intermédiaire des deux pointes excitatrices, - une mesure du champ H par le capteur de champ, - une mesure de la différence de potentiel U par les deux pointes de mesure, - une détermination de la perméabilité µ pour une zone de polarisation centrée autour de ladite polarisation magnétique H1 et - une modification de la polarisation H1 appliquée et une répétition des étapes 2 à 5.

Cet article brosse un panorama de la CAO en génie électrique. Une vision globale de la conception est d’abord introduite avant de présenter le processus itératif du prototypage virtuel avec quelques-unes des approches de modélisation classiquement utilisées pour évaluer les performances des convertisseurs électriques. L’accent est mis sur la nécessité de tenir compte de l’environnement d’utilisation du dispositif à concevoir et des différentes physiques mises en jeu ainsi que sur les stratégies d’optimisation types dans le processus de conception. Un éclairage est apporté sur les effets des procédés de fabrication, notamment pour distinguer le prototype virtuel du prototype réel. Enfin, la présentation de quelques axes de développements futurs dans le domaine de la CAO clôture l’article.