Non-oriented Steel Sheets Research Articles

Magnetostrictive strain monitoring in Non-Oriented Si-Fe steels using a SAW resonator sensor

The aim of this study is to introduce a new technique for characterizing the magnetostrictive behavior of non-oriented ferromagnetic steel sheets using miniaturized wireless surface acoustic wave sensors (SAW). Unlike conventional optical and electromechanical techniques, this type of sensor offers advantages such as on-board capability, high-temperature resistance (up to 400 °C), and the ability to be connected remotely. The final objective is to monitor magnetic stresses in electrical machines, aligning with the requirements of Industry 4.0 and predictive maintenance. The focus of the present study is the measurement of magnetostriction in ferromagnetic steel sheets, employing a wireless surface acoustic wave resonator operating within the 433 MHz ISM band, under various mechanical fixation configurations. To ensure the accuracy and reliability of SAW measurements, a commercial strain gauge is employed as a reference sensor. Measurements are conducted at different excitation frequencies to explore the phenomenon comprehensively.

Measurement of alternating and rotational magnetostrictions of Non-oriented silicon steel sheets

Extensive numerical analyses and experimental tests have shown that while major regions of magnetic cores in electromagnetic devices, such as transformers and rotating electric machines, are dominated by the alternating magnetic fields, the rotating magnetic fields exist in the corner joints of multi-phase transformers and the yoke area behind the teeth of rotating electric machines. These magnetic fields cause core losses due to hysteresis and eddy currents, mechanical vibration and acoustic noises due to magnetostriction. Many studies have been reported in the literature on alternating and rotational core losses and alternating magnetostriction, but not so much on rotational magnetostriction, especially in non-oriented (NO) silicon steel sheets. The vibration and noise caused by rotational magnetostriction are much higher than those caused by alternating magnetostriction. This paper reports the development of a magnetostriction measurement system consisting of a 2D symmetrical single sheet tester (SST) and resistance strain gauges. The selection considerations of resistance strain gauges are summarized. The alternating and rotational magnetostriction characteristics of a NO silicon steel, B35A300 (0.35 mm), are measured. Because the rotating magnetic field in the stator is not always ideally circular but more often elliptical, the magnetostriction under elliptical magnetizations with different axis ratios is also measured. The magnetostriction anisotropy of the NO steel sheet is observed and analyzed. The elongation and contraction under alternating, circular and elliptical rotating magnetizations with different axis ratios are discussed. The results can provide data support for calculating and designing multi-phase transformers and rotating electric machines under different types of magnetizations. The research can provide theoretical and practical guidance for mitigating mechanical vibration and acoustic noise caused by magnetostriction.

Magnetic properties deterioration of non-oriented steel due to laser cutting

In the manufacturing process of electrical machines, laser cutting is widely used to produce the laminations of cores. The internal stresses introduced by the high-energy laser beam will lead to deterioration in the magnetic properties of the non-oriented silicon steels. To accurately predict the core losses of the electrical machines, it is important to analyze the deterioration degree and the deterioration mechanism of the non-oriented steel sheets caused by laser cutting. In this paper, first, the local magnetic properties of the non-oriented steel 35WW250 at different positions are measured under the alternating sinusoidal excitation, in which the degradation degree is evaluated based on the core loss from the macroscopic perspective. Second, from the microscopic perspective, the observed magnetic domain patterns at the edge and those evolutions under the excitation of the magnetic field are investigated. The experimental results demonstrate that laser cutting can lead to the magnetic degradation of the non-oriented steels with a transverse depth of 18 mm from the edge. Moreover, the laser cutting process leads to significant variations in the patterns of the magnetic domains at different positions. The magneto-optical observation and local magnetic measurement verified the effectiveness of the analytical method, which is of great significance for the evaluation and improvement of the processing technique of the silicon steels.

Variations of Magnetic Domain Structures and Microstructures in Non-oriented Electromagnetic Steel Sheets during Tensile Deformation

Variations of Magnetic Domain Structures and Microstructures in Non-oriented Electromagnetic Steel Sheets during Tensile Deformation

Experimental and finite element analysis of the shear cutting process of electrical steel sheets under various process conditions

Almost every electrical machine consists of the stator and rotor cores, which are made of stacked non-oriented electric steel sheets. Punching and blanking are the two commonly used shear cutting operations for manufacturing electrical machine components. The presented research was aimed to evaluate the shear cutting process of two grades of electrical steel sheets. The shear cutting process causes the formation of residual stresses in the cut segments from the non-oriented electric sheet metal, resulting in increased iron losses. Numerical modeling and experimental research were used to investigate the influence of cutting clearance as well as blunt cutting edge of the shear cutting tool on the residual stresses induced by shear cutting under different shear cutting parameters. The data derived from experiments were applied in finite element analysis of the shear cutting part in the shape of a toroid. Comparison between the results of the experiments and the FE simulations showed that the shear cutting process can be accurately predicted.

FEM Modeling of Shear Cutting of Electrical Steel Sheets under Various Technological Conditions

Almost all electrical machine consists of the stator and rotor cores, which are made of stacked non-oriented electric steel sheets. Punching and blanking are the two commonly used shear cutting technologies. The efficiency and performance of an electrical machine depend on the magnetic properties of its magnetic core. The shear cutting process causes the formation of residual stresses in cut segments next to the cutting line from the non-oriented electrical sheet metal, resulting in increased iron losses. The extent of deterioration in the magnetic material properties depends on the amount of induced stresses, which is affected by the used process parameters during shear cutting and the mechanical properties of the electrical steel sheets. This paper focuses on the residual stresses induced by punching with different shear cutting conditions using finite element analysis. Influence of cutting clearance of the shear cutting tool on were observed.

Core Loss Properties of a Motor With Nanocrystalline Rotor and Stator Cores Under Inverter Excitation

In this paper, we develop and examine permanent magnet synchronous motors (PMSMs) by use of both stator and rotor cores made of nanocrystalline magnetic materials (NMMs). We report core loss properties of the PMSM with the NMM under inverter excitation. In addition, we compare core losses of the PMSM with conventional non-oriented (NO) steel sheets under inverter excitation to discuss the core loss characteristics of the NMM motor. In average, under inverter excitation, the reduction ratio in core loss of the PMSM made of NMM is about 60% as compared with the core loss of the PMSM with NO sheets. In particular, the average decrease obtained by using NMM rotor core instead of NO rotor core is about 30%.

Degradation of Static and Dynamic Magnetic Properties of Non-Oriented Steel Sheets by Cutting

The performances of non-oriented iron-silicon (NO Fe-Si) alloys, which are among the most commonly used materials for soft magnet applications, suffer because of mechanical stresses, whose intensity depends on the cutting technology applied, when these materials are used in the shape of strips in the magnetic core manufacture. This paper presents a detailed analysis of the influence that the stresses, arising from mechanical punching technology, have on the energy losses and normal magnetization curves, measured on NO Fe-Si samples. High-quality Cogent NO20 Hi-Lite and M300-35A samples, having a thickness of 0.2 and 0.35 mm, respectively, with a length of 300 mm, were cut by guillotine shear method to obtain strips with widths varying from 5 to 60 mm. The attained strips having different widths were characterized using a hysteresisgraph-wattmeter to measure ac energy losses and hysteresis cycles in the frequency range from 3 to 1500 Hz for NO20 and up to 400 Hz in the case of M300-35A. The dynamic loss behavior is presented in accordance with the statistical theory of losses, while a low to moderate increase is observed with the sample width decrease. The measured total energy losses were then decomposed into the hysteresis and dynamic components, including the classical and excess energy losses. The energy losses’ behavior as a function of the strip width was, eventually, analyzed and modeled, considering that cutting process induces local hardening on the borders of the samples. The experimental results put also in evidence a hyperbolic variation of the hysteresis losses versus strip width in both cases. As a remarkable result of these considerations, we observe that the evolution of the hysteresis energy losses can be predicted from the very wide, almost undamaged, to narrowest, fully degraded width strips.

Calculation of energy loss due to macroscopic eddy currents in ferromagnetic materials considering hysteresis loop

The paper presents an algorithm for calculating the energy loss due to macroscopic eddy currents considering the non-linearity of magnetization characteristics and magnetic hysteresis. It was found that for non-oriented steel sheet with a silicon content of 6.5% and thickness 0.1 mm the consideration of non-linearity and magnetization characteristics has a little effect on the energy loss, at least up to 400 Hz. In the application of the algorithm, there are some limitations resulting from the assumption of the average value of the induction flux in the sample cross-section, numerical problems and hysteresis loop shapes.

Magnetic Loss Versus Frequency in Non-Oriented Steel Sheets and Its Prediction: Minor Loops, PWM, and the Limits of the Analytical Approach

The pulsewidth modulation (PWM) technique is commonly used to supply modern high-speed electrical machines. The fundamental frequency is typically in the kilohertz range, with switching frequencies of several tens of kilohertz, as determined by the new SiC- or GaAs-based power transistors modules. Switching introduces minor loops in the major hysteresis cycle, with durations of the order of $100~\mu \text{s}$ or lower, with the resulting magnetization dynamics influenced by strong skin effect. However, since these minor loops have relatively small amplitude, their constitutive equation may be described by an equivalent permeability (real or complex), depending on the mean slope of the minor loop and its static energy loss. By retrieving this permeability, the classical loss is straightforwardly calculated by analytical solution of Maxwell's equations. In this paper, we measure and calculate, according to the quasi-linear approximation for the minor loops, the magnetic energy losses of 0.194 mm thick non-oriented Fe–Si 3.2% sheets subjected to PWM induction waveform. Minor loop peak amplitudes ranging between 50 mT and 0.2 T and frequencies up to 10 kHz are investigated. The results are consistent with the proposed model, to within 5%.

Effect of punching and water-jet cutting methods on magnetization curve and energy losses of non-oriented magnetic steel sheets

Effect of punching and water-jet cutting methods on magnetization curve and energy losses of non-oriented magnetic steel sheets

Alternating and Rotational Losses Up to Magnetic Saturation in Non-Oriented Steel Sheets

A three-phase magnetizer has been developed, by which non-oriented Fe-Si steel sheets can be characterized under alternating and rotational flux up to a polarization value $J_{p}\approx 0.98~J_{s}$ , where $J_{s}$ is the saturation magnetization. The loss measurements, performed in the frequency range 2 Hz–1 kHz, require the combination of field-metric and thermometric methods, besides fine control of the induction wave-shape/loci under the required demanding exciting conditions. By exploiting the loss separation concept, it is observed that under rotational flux, both the hysteresis and excess loss components monotonically decrease with $J_{p}$ , to disappear at saturation. The measured losses then become equal to the calculated classical losses. This could actually be predicted, because of the expected disappearance of the domain walls under saturating rotational field, but it has never been previously verified by the experiments.

A Simple Compensation Method for the Accurate Measurement of Magnetic Losses With a Single Strip Tester

We present a new method for the accurate characterization of soft magnetic sheets using a permeameter based on the precise compensation of the magnetomotive force (MMF) drop in the flux-closing yoke. It has been developed in order to overcome the systematic uncertainty affecting the value of the magnetic field strength in single sheet testers when obtained, according to the standards, through the measurement of the magnetizing current. This phenomenon is more critical to high-permeability materials, because of the reduced MMF drop across the sample. While additional sensors and auxiliary windings have been proposed in the literature, a novel approach is demonstrated here, based on the use of the permeameter upper half yoke as the MMF drop sensor and of an auxiliary winding on the lower half yoke, implementing compensation. This solution, dispensing one from dealing with the usually small signal levels of the conventional MMF drop sensors (e.g., Chattock coils), provides the best results with the introduction of wedge-shaped magnetic poles, in order to accurately define the magnetic path length. The method is validated by the measurements of power loss, apparent power, and hysteresis cycles on non-oriented and grain-oriented Fe-Si steel sheets, which are compared with local measurements performed on the same samples using H-coil and B-coil across a uniformly magnetized region.

Model of Magnetic Anisotropy of Non-Oriented Steel Sheets for Finite-Element Method

Even non-oriented steel sheets present a magnetic anisotropic behavior. From rotational flux density measurements at 5 Hz, the model of magnetic anisotropy is derived from two surface basis-cubic splines with the boundary conditions matching with ferromagnetic theory. Furthermore, the investigation of the magnetic anisotropy shows that the $H(B)$ characteristic is not strictly monotonous due to the angle difference between the field and the flux density. Hence, the standard non-linear solvers would either diverge or converge toward the closest local minimum. Thus, we propose two different specific solvers: 1) a combined particle swarm optimization with a relaxed Newton-Raphson and 2) a modified Newton method.

Loss Decomposition in Non-Oriented Steel Sheets: The Role of the Classical Losses

—The concept of loss separation based on the Statistical Theory of Losses (STL) provides complete and accurate description of the frequency dependence of the energy losses in non-oriented soft magnetic sheets under the assumption of uniform magnetization reversal through the sheet cross-section. This assumption, implying a simple standard formulation for the classical loss component, has been recently challenged in the literature, in favor of a non-uniform reversal mechanism, expected to prevail in highly non-linear materials, where saturation magnetization wavefronts are deemed to symmetrically propagate across the sheet thickness (Saturation Wave Model, SWM). Different conclusions regarding the dynamic loss analysis and its decomposition into the classical and excess loss components correspondingly emerge. In this paper we discuss detailed investigations on the broadband energy loss versus frequency behavior in different non-oriented Fe-Si and low-carbon steel sheets. The experiments can be fully and consistently described by the STL. This occurs, in particular, for high-induction values and near-squared hysteresis loops, a predictable condition for adopting the SWM, which fails instead to account for the experiments.

Analytical model for magnetic anisotropy of non-oriented steel sheets

Purpose – Recent investigations on magnetic properties of non-oriented (NO) steel sheets enhance the comprehension of the magnetic anisotropy behaviour of widely employed electrical sheets. The concept of energy/coenergy density can be employed to model these magnetic properties. However, it usually presents an implicit form which requires an iterative process. The purpose of this paper is to develop an analytical model to consider these magnetic properties with an explicit formulation in order to ease the computations. Design/methodology/approach – From rotational measurements, the anhysteretic curves are interpolated in order to extract the magnetic energy density for different directions and amplitudes of the magnetic flux density. Furthermore, the analytical representation of this energy is suggested based on statistical distribution which aims to minimize the intrinsic energy of the material. The model is finally validated by comparing measured and computed values of the magnetic field strength. Find...

Performance Comparison on 0.35 mm and 0.50 mm Thicknesses of Non-Oriented Steel Sheets Using FEM

– Decrease the iron loss, total loss and thicknesses of steel sheets will produce high efficiency of the induction motor This paper studies, a rotor construction with different thickness was investigated thoroughly and analyzed in the case of efficiency, torque, all losses and distribution field. All result simulation was done by MotorSolve (IM) which allows the user to produce more design of induction motor with a decision within a short time. According to simulation result, the 0.35 mm showed that a best performance and efficient compared to 0.50 mm thickness of rotor frame.

Dynamic Magnetization Model of Nonoriented Steel Sheets

A simplified model of conducting ferromagnetic sheet, which describes magnetization of isotropic electrical steels is proposed. The model improvement is achieved by determining eddy current component of the magnetic field at the sheet surface in the framework of the method by Wolman and Kaden, which describes the dynamic magnetization of the material with rectangular hysteresis loop. An algorithm of model fitting is proposed and a comparison of calculated and experimental results has been carried out.

Possible influence of sulfur content on magnetic aging behaviors of non-oriented electrical steels

Six non-oriented steel sheets of similar grade produced by different steel companies were used to analyze the magnetic aging behaviors after aging at 200°C for 48 h. It was observed that tiny S atoms, besides C and N, could also induce certain increase of core loss during aging. Thermodynamic calculation indicated that the nucleation driving force of FeS is much higher than those of Fe3C and Fe4N at low temperature, while S atoms, which tend to segregated around dislocations and boundaries, would diffuse rapidly along the crystalline defects while FeS particles would form. Therefore, higher content of tiny S atoms could increase core loss during service time of non-oriented steel sheets.

Influence of electrical steel sheet textures on their magnetization curves

Abstract The Goss texture is a characteristic feature of grain-oriented transformer steel sheets. Generator sheets, which are produced as non-oriented steel sheets, should have isotropic features. However, measurement results of generator sheets, confirmed by crystallographic studies, indicate that these sheets are characterized by certain, quite significant anisotropy. The first purpose of this paper is to present the influence of textures of generator and transformer steel sheets on their magnetization characteristics. The second aim is to propose a method which takes into account the sheet textures in the calculations of magnetization curves. In calculations of magnetization processes in electrical steel sheets, models in which the plane of a sheet sample is divided into an assumed number of specified directions are used. To each direction a certain hysteresis loop, the so-called direction hysteresis, is assigned. The parameters of these direction hystereses depend, among other things, on the texture type in these steel sheets. This paper discusses the method which calculates the parameters of these direction hystereses taking into account the given sheet texture. The proposed method gives a possibility of determining the magnetization characteristics for any direction of the field intensity changes.