Grain-oriented Electrical Steel Sheets Research Articles

Effect of CaO in magnesia coating on Mg2SiO4 layer formation on the surface of grain-oriented electrical steel

Mg2SiO4 layer formed by the reaction between magnesia separator coating and the oxide layer on the surface of grain-oriented electrical steel sheets plays important roles for magnetic performances of grain-oriented electrical steel. High-quality Mg2SiO4 layer is the key factor for the high-quality grain-oriented electrical steel production. This article makes investigations on Mg2SiO4 layers formed with different CaO content in magnesia coating after the final box annealing treatment. And the suitable CaO content which promote the formation of excellent Mg2SiO4 layer were summarized. All these studies provide theoretical and data support for the high-quality grain-oriented electrical steel production on site.

The Two-Domain Model Utilizing the Effective Pinning Energy for Modeling the Strain-Dependent Magnetic Permeability in Anisotropic Grain-Oriented Electrical Steels.

This paper presents a newly proposed domain wall energy-based model of the 2D strain dependence of relative magnetic permeability in highly grain-oriented anisotropic electrical steels. The model was verified utilizing grain-oriented M120-27s electrical steel sheet samples with magnetic characteristics measured by an automated experimental setup with a magnetic yoke. The model's parameters, identified in the differential evolution-based optimization process, enable a better understanding of the interaction between stress-induced anisotropy and magnetocrystalline anisotropy in electrical steels. Moreover, the consequences of the simplified description of grain-oriented magnetocrystalline anisotropy are clearly visible, which opens up the possibility for further research to improve this description.

Observation of Buried Magnetic Domains in Grain-Oriented Electrical Steel

Bulk-sensitive microscopic measurements of buried magnetic domains are reported. Utilizing a new magneto-optical effect in the hard X-ray regime, referred to as X-ray magnetic circularly polarized emission (XMCPE), the internal transverse domains in a grain-oriented (GO) electrical steel sheet are unambiguously observed. This allows the lateral shapes of the transverse domains to be successfully visualized. In addition, we discuss the magnetic domain structure of the supplementary domains below the surface from measurements performed at several pairs of incident and exit angles.

Reduction of Iron Loss on Grain-oriented Electrical Steel Sheet Using Vector Magnetic Characteristic Control Technology

Reduction of Iron Loss on Grain-oriented Electrical Steel Sheet Using Vector Magnetic Characteristic Control Technology

Establishment of the standard method of magnetostriction measurement of grain-oriented electrical steel strip and sheet

Standard method of magnetostriction measurement of grain-oriented electrical steel strip and sheet by means of a single sheet tester and an optical sensor was established as IEC 60404-17 Ed.1 [1] by the IEC/TC68 after intense considerations among magnetostriction experts. A new idea called “bridge” was introduced in order to minimize effects due to mechanical factors and other improvements were made. The 4th international round robin test (RRT) was carried out in 2020 and it was confirmed that the measurement reproducibility of the peak-to-peak value of magnetostriction improved from 5% or less in the 3rd RRT to 2% or less.

Classification of Grain-Oriented Electrical Steel Sheets by Magnetic Barkhausen Noise Using Time-Frequency Analysis and Selected Machine Learning Algorithms

In this paper, a combination of Magnetic Barkhausen Noise (MBN) and several classical machine learning (ML) methods were used to evaluate both the grade and the magnetic directions of conventional and high grain oriented electrical sheets subjected to selected surface engineering methods. The presented analysis was conducted to compare the performance of two machine learning approaches, classical ML and deep learning (DL), in reference to the same MBN examination problem and based on the same database. Thus, during the experiment, 26 classical ML algorithms were used including decision trees, discriminant analysis, support vector machines, naïve Bayes, nearest neighbor, artificial neural networks and ensemble classifiers. The experiments were carried out considering a different number of recognized magnetic directions and hence the number of determined classes as well. The results of classification accuracy of the applied ML methods were compared with those obtained for the DL model presented in a previous paper. The highest accuracy was obtained for ML models based on artificial neural networks and ensemble bagged trees. However, the accuracy did not reach 89% in the best case—for the smallest number of determined classes. Nevertheless, the achieved results generally indicated an approx. 10 percent advantage of the deep learning model over the classical ones in terms of accuracy in each of the considered cases.

Using grain oriented electrical steel sheets for electric motor in automotive application: Tooth segmentation

Grain Oriented Electrical Steel (GOES) have better performance in terms of permeability and iron losses compared to conventional Fe-Si 3% Non-Oriented Grains Electrical Steel (NOES), particularly when it is magnetized in the rolling direction. This paper presents a concentrated winding radial flux permanent magnets synchronous machine (PMSM) equipped with teeth made of GOES sheet. The goal is to assess the suitability of the use of GOES sheets to improve the efficiency of electric motors. This work is based on the comparison of the performances (Joule losses, iron losses, losses in the permanent magnets and efficiency) of two iso-geometric motors: a reference motor made of NOES sheets and a motor with GOES sheet teeth, at iso-torque and over the operating range (at constant torque and flux weakening). The comparison is made using a finite element software application considering the magnetic anisotropy of the GOES sheets.

A Preisach-Based Magnetostriction Model for Highly Grain-Oriented Electrical Steel Under Rotating Magnetic Field

An accurate estimation for the magnetostrictive effect in highly grain-oriented electrical steel sheet (HGO-ESS) is helpful for determining the deformation and vibration originating from magnetostriction during the design stages of electrical equipment such as the motor and power transformer. In this paper, a Preisach-based magnetostriction model for HGO-ESS is proposed to simulate the normal and shear magnetostriction properties under alternating and rotating magnetic fields. In the model, the Everett function databases are constructed and identified by using a set of measured symmetric magnetostriction butterfly loops under different rotating magnetic field conditions. The measurement butterfly loops are measured by a round-type two-dimensional single strain tester (R-2-D-SST). Finally, the simulation data and measurement data under different rotational magnetization conditions are compared to verify the effectiveness of the proposed model.

Neural Network Modeling of Arbitrary Hysteresis Processes: Application to GO Ferromagnetic Steel

A computationally efficient hysteresis model, based on a standalone deep neural network, with the capability of reproducing the evolution of the magnetization under arbitrary excitations, is here presented and applied in the simulation of a commercial grain-oriented electrical steel sheet. The main novelty of the proposed approach is to embed the past history dependence, typical of hysteretic materials, in the neural net, and to illustrate an optimized training procedure. Firstly, an experimental investigation was carried out on a sample of commercial GO steel by means of an Epstein equipment, in agreement with the international standard. Then, the traditional Preisach model, identified only using three measured symmetric hysteresis loops, was exploited to generate the training set. Once the network was trained, it was validated with the reproduction of the other measured hysteresis loops and further hysteresis processes obtained by the Preisach simulations. The model implementation at a low level of abstraction shows a very high computational speed and minimal memory allocation, allowing a possible coupling with finite-element analysis (FEA).

Characteristics and Design of an SRM using Grain-Oriented Electrical Steel Sheets

Characteristics and Design of an SRM using Grain-Oriented Electrical Steel Sheets

Measurement of Stress and Temperature Dependent Vector Magnetic Properties of Electrical Steel Sheet

In addition to the excitation condition, the magnetic properties of electrical steel sheet (ESS) also depend on stress and temperature. This article proposes one systematic measurement method of measuring the vector magnetic properties (VMPs) of ESS. In the proposed method, the coupling effect of temperature and stress are considered. The uniform magnetic field distribution is generated in the measurement area of the specimen using a vertical-type orthogonal double-U shaped yoke. Since the specimen is cross shaped, the mechanical stress can be applied conveniently. The B-probe method and the double compound H-coil method are adopted to measure vector magnetic flux density ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</i> ) and magnetic field intensity ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> ). Moreover, the vector B-H sensor is assembled into a ceramic frame from within, which can withstand high temperature. A linear actuator can apply tensile or compressive stress along the rolling direction and transverse direction of the specimen. The variable temperature measurement conditions are achieved by a temperature controller and ceramic heating sheets. The stress and temperature dependent VMPs of nongrain oriented ESS and grain-oriented ESS are measured to verify the effectiveness of the proposed measurement method. The change regulation of VMPs with temperature and stress is summarized.

A measurement method of minor hysteresis loss of electrical steel sheet by means of a single sheet tester

This paper investigates measurement methods of iron losses of asymmetric minor hysteresis loops of electrical steel sheets by means of a single sheet tester. As inverter-driven electric machines have been increased, consideration of harmonic iron losses is indispensable to design highly-efficient electric machines. In general, measurement of iron losses of asymmetric minor hysteresis loops has been carried out by using a fluxmeter to detect a dc component in addition to ac components measured by means of a B-coil because the asymmetric minor loops are dc-biased. However, the fluxmeter has a drift problem which results in inaccurate evaluation of harmonic iron losses. Therefore, the distorted waveform method which adopts only ac measurement is conceived. Furthermore, the dc-biased method is improved by estimating the dc components from a normal magnetization curve, which is obtained by connecting tips of symmetric hysteresis loops. In order to demonstrate their effectiveness, the iron losses of asymmetric minor hysteresis loops of non- and high permeability grain-oriented electrical steel sheets are measured up to the high flux density region.

Standardization of the method of magnetostriction measurement of grain-oriented electrical steel strip and sheet

Standardization of the method of measurement of AC magnetostriction characteristics of grain-oriented electrical steel strip and sheet by means of a single sheet tester and an optical sensor, i.e. IEC 60404-17 Ed.1 [1], has been promoted in the IEC/TC68/WG2 to meet the demand of transformer industry. The relationship between the magnetostriction characteristics of grain-oriented electrical steel and transformer noise is complicated and yet not fully understood. One of basic problems has been the lack of a standard for the magnetostriction measurements. The measurement requires detection of slight vibration of the test specimen at a resolution of 0.01 μm/m or better. In order to ensure this resolution, not only magnetic aspects but also mechanical aspects of the test apparatus, e.g. the influence of friction and external vibrations, have to be specified. The size of test specimen is restricted to 100 mm × 500 mm. The flux closer is a vertical single yoke or a horizontal double yoke. In order to avoid the influence of friction and vibration, no weight is put on the test specimen except an optical target and a clamp to fix the test specimen to the test apparatus. Also, no weight is connected to the end of test specimen to prevent additional vibration modes. The optical target is low mass and made of non-magnetic and non-conductive materials. The optical target and the clamp are placed between opposite pole faces of the yoke. In order to realize a low and constant friction coefficient, an insertion sheet with a thin fluorine resin-impregnated glass cloth adhesive film on its upper surface is placed under the test specimen. A round robin comparison using different test setups in accordance with the draft of standard was carried out.

Simple Numerical Calculation Method of Rotational Iron Loss in Silicon Steel Sheets

To evaluate the iron losses of motors and three-phase transformers, the rotational iron loss should be considered. A simple numerical calculation method of the rotational iron losses under rotational flux with high flux density and different axis ratios is proposed in this paper. First, it is shown that the method of decomposing the rotational flux into the directions of the major and minor axes of the rotational flux is effective in calculating the rotational iron losses of the non-oriented and grain-oriented electrical steel sheets in low magnetization region. Then, the simple iron loss calculation method is improved to consider the decrease of rotational hysteresis and anomalous eddy current losses in high magnetization region under circular rotational flux and verified by comparing with measurement results. Furthermore, it is improved to be applicable to rotational iron loss calculation under rotational flux with different axis ratios and verified by comparing with measurement results.

Modeling of Magnetostrictive Property of Electrical Steel Sheet Under Vectorial Excitation

An accurate estimation for the magnetostrictive effect in an electrical steel sheet is helpful for determining the deformation and noise originating from magnetostriction during the design stages of electric devices. Because of limited measurement conditions, the rotational magnetostrictive modeling has been left aside during the calculations of core deformations. In this paper, the dynamic hysteresis properties of magnetostriction under different elliptic magnetization loci in a grain-oriented electrical steel sheet are investigated based on a rotational magnetic properties tester. A dynamic magnetostrictive model is proposed, in which the principal strains of magnetostrictions are time-dependent on variations of magnetic flux density, and the influences of past magnetization histories of material on the magnetostrictive strains are taken into account. Finally, magnetostrictive characteristics of a single-phase transformer core model built with uncut cores are analyzed and verified by experimental results. The results show that the rotational magnetostriction in the corner area is found to have a major contribution to core vibration and the proposed model can be employed to estimate the rotational magnetostrictions effectively.

Improvement of Texture and Magnetic Properties in 4.5 wt.% Si Grain-Oriented Electrical Steels

4.5 wt.% Si grain-oriented electrical steel sheets were successfully produced by hot rolling, normalizing, warm rolling and annealing, and texture evolution was investigated using macro- and micro-texture analysis. It is found that the recrystallization texture of sheets is very sensitive to the warm rolling reduction, and 83-87% warm rolling reductions are more favorable to η texture ( //RD, rolling direction) evolution during secondary recrystallization, and consequently the magnetic induction B8 is significantly improved to 1.69-1.70 T in this rolling reduction range. The decreased B8 in the 89% warm rolled sheet is ascribed to the obviously decreased primary recrystallization η fiber, which leads to the insufficient quantity of η grains in the early stage of abnormal grain growth. The results obtained in the current work can provide an efficient way to improve the recrystallization texture of 4.5 wt.% Si grain-oriented electrical steel sheets.

Effect of Magnetic Annealing on Magnetic Characteristic of Amorphous Wound Core

In this paper, in order to make a clear principal cause in increasing iron loss of amorphous wound cores in processing, effects of bending stress on magnetic characteristics of a Fe-based amorphous wound core are clarified. The amorphous magnetic materials have been widely used as a core material of power transformers to reduce iron loss due to their excellent soft magnetic characteristics. However, the amorphous magnetic material has an issue that the building factor (B.F.) is very large in comparison with that of grain-oriented electrical steel sheets. The amorphous transformers usually use a wound core formed by stacking plural amorphous sheets in different lengths. Bending stress is, therefore, generated at each corner of the wound core in processing. Due to this bending stress, the magnetic characteristics of the wound core deteriorate. The deterioration of magnetic characteristics of the wound amorphous core is so large because of the large magnetostriction constant. As a result, the B.F. of this material becomes larger. In order to remove the residual stress, which is generated in the wound core including the bending stress, the amorphous wound core is usually annealed in a magnetic field, which is called “a magnetic annealing.” In this paper, the effect of the magnetic annealing on the magnetic properties is studied experimentally by evaluating some wound amorphous model cores. As a result, a suitable magnetic annealing condition is clarified and the iron loss of the wound amorphous model core is reduced by 65.7%.

Barkhausen Noise Measurement System Using a Three-Pole Probe

In the present study, a three-pole probe is proposed for measurement of Barkhausen noise (BN). A system was constructed for forming a magnetic field using the three-pole probe and succeeded in forming rotating magnetic fields of the same amplitude in all directions and arbitrary orientated stationary alternating magnetic fields. Furthermore, a BN measurement system was constructed and used to measure the BN of a grain-oriented electrical steel sheet. The results show that the BN exhibits a large output in the direction of the easy magnetization axis of the specimen, and it is demonstrated that the BN measurement result using the rotating magnetic field formed by the three-pole probe is reliable.

Magnetostriction of Electrical Steel and Its Relation to the No-Load Noise of Power Transformers

This paper analyzes the relationship between the experimentally determined magnetostriction of grain-oriented electrical steel (GOES) coils and the no-load noise of power transformers (PT). The main source of a PT's no-load noise is the magnetostrictive vibration of the magnetic core built with stacked GOES sheets. With an in-house measurement system, in which steel coils with a mass of up to 6000 kg is measured, differences in the GOES materials’ magnetostriction were identified. In this paper, we analyze the flux dependent behavior and harmonic composition of the magnetostrictive properties of different steel coils. Based on the identified differences in the steel coils’ magnetostriction, two experimental studies with PTs are provided showing exemplary results. The first study shows initial findings of the relationship between the magnetostriction of the deployed steel coils and the emitted no-load noise of model transformers. In a second study, the aforementioned investigations were extended with measurements of large power transformers. Both studies cover a correlation and performance analysis including comparisons of the noise-related GOES certificate value B8 (also known as B800 value).

Investigating the fatigue behavior of grain-oriented Fe-3%Si steel sheets using magnet-optical Kerr microscopy and micromagnetic multiparameter, microstructure and stress analysis

Fatigue is considered as a reason for a significant number of mechanical failures of engineering materials. Conventionally, microstructural investigations along with stress-strain hysteresis measurements are performed to understand and characterize the fatigue behavior of metallic materials. Moreover, further physical data like temperature, electrical resistance and, in the case of ferromagnetic materials, magnetic properties can be used for a comprehensive characterization of fatigue process. The present work has employed Magneto-Optical Kerr Effect (MOKE) microscope and Micromagnetic Multiparameter, Microstructure and stress Analysis (3MA) system to illustrate magnetic domain structure and various intrinsic magnetic properties including magnetic Barkhausen noise (MBN) of the investigated material. In order to investigate the influence of the mechanical deformation processes on the magnetic parameters, samples were produced out of the grain-oriented electrical steel sheets and were subjected to a tensile test as well as a cyclic strain increase load test with R = 0 at ambient temperature.