Silicon Iron Sheets Research Articles

3-D MACC Modeling of Instantaneous Magnetic Flux Distributions in Epstein Tester

Magnetic energy losses of silicon iron (SiFe) sheets are determined by the standardized methods of single sheet tester (SST) or Epstein tester (ET). The ET is much more compact and can be applied in a large range of frequency. However, it suffers from several sources of systematic errors. The most severe one is given by the magnetic cores flux distribution that shows a strong degree of inhomogeneity. This fact is highly evident. However, it never has been investigated in detail so far. Herein, we report results of a 3-D modeling, performed by magnetic anisotropic circuit calculation (MACC), considering non-linearity in connection with anisotropy, for both non-oriented (NO) steel and grain-oriented (GO) steel. The results reveal substantial differences of the corresponding flux distributions. NO steel proves to be characterized by high homogeneity of induction in rolling direction in the middle sections of the four limbs. However, the four corners show strong inhomogeneity in instants of low global induction, while a transition to more balanced flux arises at peak magnetization. On the other hand, this transition is much less pronounced for GO steel. As a conclusion for the evaluation of losses, a distinction is needed for the two different types of material.

Degradation of magnetic properties of non-oriented silicon iron sheets due to different cutting technologies

The magnetic properties of non-oriented silicon iron alloys are strongly influenced by the cutting technology. Medium quality electrical steel M800-65A samples were cut through mechanical punching, laser, water jet and electro erosion technologies and were characterized with an industrial Single Strip Tester at the peak magnetic polarizations Jp of 0.5, 1 and 1.5 T, in the frequency range starting from 10 Hz to 200 Hz. The influence of the cutting technology on the energy losses and magnetic permeability was investigated.

Performance Factor Comparison of Nanocrystalline, Amorphous, and Crystalline Soft Magnetic Materials for Medium-Frequency Applications

The efficiency of electromagnetic devices is influenced by the losses of the applied soft magnetic material. Different structured materials are available. Choosing the most appropriate material for a medium-frequency application is not intuitive. Electromagnetic circuits of power transformers or electric motors are usually made of conventional silicon–iron sheets. Higher power densities can be achieved by an increased operational frequency, but the loss density increases with higher frequencies as well. Amorphous and nanocrystalline materials benefit from reduced eddy current losses at higher frequencies. In this paper, a performance factor is evaluated to determine the suitability of each material in a frequency range up to 10 kHz. The geometric parameters of electromagnetic designs depend on the applied material. A performance factor may help to identify the most appropriate material at a specific frequency. The final application is a medium-frequency transformer. The losses of the magnetic materials are measured by using standardized measurement equipment such as single sheet tester or Epstein frame. A semi-physical iron-loss model is used to describe the measured losses. These results are used to determine the performance factor.

Improvement of the Magnetic Properties of Silicon Iron Alloys through Laser Irradiation and Thermal Treatments

We report an investigation on the improvement of magnetic properties in crystalline silicon iron alloys. It was studied the influence of three thermal treatments on the energy losses of non-oriented silicon iron (NO FeSi) sheets, M800-65A industrial grade, at two peak magnetic polarizations 0.5 T and 1 T. First treatment was done at 200 °C for 60 minutes, the second treatment at 550 °C for 30 minutes and the third treatment at 700 °C for 10 minutes. In the case of grain-oriented silicon iron (GO FeSi) sheets, 30Z140 industrial grade, was analyzed the influence of laser scratching on the magnetic properties at peak magnetic polarization 0.25 T. In the case of both steel grades is presented the reduction of the hysteresis, classical and excess losses, that occur after the applied treatments, using the concept of energy loss separation.

Optimized model for magnetic hysteresis in silicon-iron sheets by using the simulated annealing algorithm

To characterize magnetic materials it is very important to take into account the initial magnetization curve and the magnetic hysteresis loop. Several approaches have been used to model these characteristics. However, some problems related to the accuracy of the results, especially at the knee of the curves have been encountered. This paper presents a contribution to solve this problem using both a simulated annealing algorithm to optimize the parameters of the Jiles-Atherton magnetic hysteresis model and the Brillouin theory to express the anhysteritic magnetization. The obtained results are in good agreement with measurements performed on silicon- iron sheets.

Influence of cold-rolling texture and heating rate on {1 1 0}〈0 0 1〉 development in inhibitor-free 3%Si–Fe sheets

This paper presents cold-rolling and annealing methods to obtain a high-magnetic induction in inhibitor-free 0.1-mm-thick 3% silicon–iron sheets containing 18 or 150 ppm sulfur. In case of the two-step cold-rolling, the sheets containing 150 ppm sulfur showed a strong {1 0 0} final texture at 400 °C/h, and some fraction of {1 1 0} component was observed at 25 °C/h. However, three-step cold-rolling resulted in a sharp {1 1 0}〈0 0 1〉 final texture at 25 °C/h. This is due to the difference in intensity ratio of {1 0 0}〈0 1 1〉 to {1 1 1}〈1 1 2〉 in the cold-rolling texture which influences the nucleation of {1 1 0}〈0 0 1〉 component and the selective growth kinetics of various grains. In case of 18 ppm sulfur, the final texture was mainly composed of a sharp {1 1 0}〈0 0 1〉 component even at 400 °C/h, due to the relatively low segregation concentration.

Powder reaction mechanism in fabrication of high silicon iron alloy

In the present paper, the reaction mechanism of silicon and iron powders under different sintering conditions during the fabrication of high silicon iron sheet (∼6·5 mass-%Si) is clarified. It is indicated that the phases, Fe3Si (Si) and FeSi, play an important role in the reaction between iron and silicon powders. Two temperature regions of the powder reaction are very important for producing commercial high silicon iron sheets: the temperature region of ∼1000°C in which the ductile composite structure can be produced, and the temperature region of ∼1200°C in which the density and homogeneity can be improved.

Sintering Behavior of Fe-Si Composite Powder by DPR Technique

The reaction mechanism of silicon and iron composite powders was clarified during the fabrication of high silicon iron sheet with the Si-content of 6.5wt% by Direct Powder Rolling (DPR) technique. The changes of phase composition and structure evolvement were mainly studied. It is found that a local graded structure, Fe-Fe(Si)-Fe3Si(Si)-Si, forms when sintering at 950-1000oC, which plays an important role in the DPR process. Fe3Si(Si) phase keeps higher content of Si, and Fe(Si) phase remains the state with much lower Si-content, thus provides good mechanical proprieties of rolling and cutting. Then, the subsequent sintering at about 1200oC improves the density and makes the distribution of Si homogeneous in the final high silicon iron sheets.

A novel model for magnetic hysteresis of silicon-iron sheets

A new approach to calculate the magnetic hysteresis, based on the Brillouin theory associated with the Jiles-Atherton approach, is presented. This study represents a general model compared with the classical Jiles-Atherton one. A Brillouin function, using the kinetic atomic moment , allows to determine accurately the value of the anhysteretic magnetization. The obtained results are compared with experimental ones of the silicon-iron sheets.

The use of soft magnetic composite materials in synchronous electric motor

This paper presents some aspects of soft magnetic composite (SMC) material application in synchronous electric motors (SEM). The presented stator core of the SEM was made of two types of soft magnetic materials: the classical laminated silicon iron sheets and the SMC material. First, the stator core made of SMC, which was of the same shape as the laminated core, was analysed. The next step was to search for the optimal shape of the core. The comparison of both cores includes the calculated torque, magnetic conditions and simplicity of fabrication. The 3D FEM was used to analyse the magnetic conditions and the calculated torque. The design and the analysis were validated by experimental results obtained on the prototype.

Local Graded Structure in 6.5wt%Si-Fe Alloy and the Effect on Ductility

The changes of phase composition and structure evolvement of Fe and Si powders with the ratio of 6.5wt%Si to 93.5wt%Fe were mainly studied. It is found that, the local graded structure, Fe-Fe(Si)-Fe3Si-(FeSi)-Si, forms due to the obvious diffusion and the alloying reaction between Fe and Si powders when sintering at 900-975oC. The graded structure, in which the high silicon phase based on Fe-Si alloys is packed by the low silicon solution based on Fe, exhibits a graded concentration of Si distribution. And most of the Fe-containing phase remains a state of lower Si content, less than that of 3wt%Si-Fe alloy, thus provides the good deformation behavior of rolling and cutting for the compacts. Therefore, it is feasible for the high silicon iron sheets to be produced by the powder metallurgy method.

Magnetic properties of high silicon iron sheet fabricated by direct powder rolling

In this research, the high silicon–iron strips (near to 6.5%Si) were produced by the direct powder rolling (DPR) technique. The continuous strips could be compacted by rolling from silicon and iron powders and sintered by the following heat treatments. The chemical formula, Fe+Si→Fe (Si)+Fe3Si (Si), controls the reaction of silicon and iron powders. Optimized mechanical properties of the strip due to the composite phase between Fe3Si (Si) and Fe (Si) make the further rolling possible. The soft magnetic properties of final samples were measured in the frequency from 50Hz to 20kHz and the results show that the core loss is relatively lower above 1kHz.

Stress effects on the multidirectional magnetic behaviour of grain-oriented silicon iron sheets

The paper discusses effects of tensile and compressive stress on highly grain oriented SiFe sheets subject to rotational magnetisation which was simulated according to elliptical B -patterns of model transformer cores. Experimental results are given for all three H -patterns, losses and multidirectional magnetostriction. Interpretations are based on domain theory, and conclusions are presented with respect to transformer cores.

Anisotropic vector Preisach particle

The static 2D vector magnetic behaviour of an anisotropic silicon iron sheet is modelled by a particle which depicts its space-averaged behaviour. The magnitude of magnetization is governed by a classical Preisach operator with the projection of field strength on the magnetization direction as input. Its orientation is determined by the equilibrium between the field strength orientation and the anisotropy of the sheet.

Use of a conductor screen to magnetize NdFeB magnets

The magnetizer presented in this paper consists of a magnetic core made with silicon iron sheets with a large airgap in which the permanent magnets to be magnetized are located, This magnetic structure is energized by two symmetrical coils placed on the central leg above and below the airgap. The cross section of the airgap is four times the area of the permanent magnet, so with a copper plate that surrounds the magnet (not completely), effective concentration of the flux density lines is obtained. The copper plate was called electromagnetic conductor screen. The capacitor-discharge-bank was rated 1080 /spl mu/F, 2000 V and 3.5 tesla were obtained in the central airgap. The paper presents the experimental results and theoretical analysis used to evaluate the conductor screen time-constant of the proposed magnetizing system.

Measurements and modeling of magnetostrictive strain of a transversely excited silicon iron sheet

Measurements and modelling of magnetostrictive strain of a transversely excited silicon iron sheet

A rate-dependent magnetostrictive simulation method for silicon-iron sheets under harmonic excitation

We present a representation of non-single valued anisotropic magnetostrictive strain vs flux density based on a rate-dependency law. This model is used in a continuum magnetomechanical simulation method for the vibration of a thin silicon-iron sheet excited magnetically by a sinusoidally alternating flux.

Characterisation of nonoriented electric alloys under nonconventional conditions

The variations of magnetic and loss characteristics of nonoriented cobalt-iron and silicon-iron sheets have been investigated using an Epstein frame. Cobalt-iron alloys have been tested under sinusoidal magnetic flux density with respect to frequency and temperature. Both kinds of alloys have also been investigated with respect to frequency, time constant wavefront and temperature under trapezoidal flux density. The qualitative behaviour is identical under both flux density conditions for all these alloys. These investigations have made it possible to model the variations of iron losses with experimental parameters, except the temperature. These quantitative evolutions differ with alloy and flux-density conditions and do not confirm several propositions of different authors.

Localized Deformation on Silicon Iron Sheet. Numerical Simulation of bcc Crystal Based on Crystal Plasticity Theory.

FEM simulation of the strain localization in sheet metals is performed using crystal plasticity theory. The constitutive relations formulated by Asaro et al. are used, in which the rate-dependent property is included so as to determine active slip systems uniquely for a strain increment. The strain localization which appears in a silicon iron sheet under uniaxial tension is calculated. All 48 slip systems of the bcc crystal are considered, and isotropic hardening for the relationship between resolved shear stress and strain is assumed. Strain localization is affected by the combination of the activated slip systems. The analytical results are compared with those of experiments. The dependence of localized deformation mode on initial lattice orientation is predicted well by numerical results.

Prediction of power losses in silicon iron sheets under PWM voltage supply

The behavior of iron losses in silicon iron steels submitted to a PWM voltage is studied. The influence of modulation parameters (the depth of modulation and the number of eliminated harmonics) is clarified. In particular, the idea of an equivalent alternating pulse voltage that gives the same iron losses as the PWM voltage is established. An estimation formula for iron losses under the PWM voltage is developed based on the loss separation model and the voltage form factor.