Single Sheet Tester Research Articles

A Novel Approach for Evaluating the Influence of Texture Intensities on the First Magnetization Curve and Hysteresis Loss in Fe-Si Alloys.

This paper examines the relationship between the magnetization behavior and crystal lattice orientations of Fe-Si alloys intended for magnetic applications. A novel approach is introduced to assess anisotropy of the magnetic losses and first magnetization curves. This method links the magnetocrystalline anisotropy energy of single crystal structures to the textures of polycrystalline materials through a vectorial space description of the crystal unit cell, incorporating vectors for external applied field and saturation magnetization. This study provides a preliminary understanding of how texture influences magnetic loss rates and the first magnetization curves. Experimental results from Electron Back-Scattered Diffraction (EBSD) and Single-Sheet Tests (SSTs), combined with energy considerations and mathematical modeling, reveal the following key findings: (i) a higher density of cubic texture components, whether aligned or rotated relative to the rolling direction, decreases magnetic anisotropy, suggesting that optimizing cubic texture can enhance material performance; (ii) at high magnetic fields, there is no straightforward correlation between energy losses and polarization; and (iii) magnetization rates significantly impact magnetization loss rates, highlighting the importance of considering these rates in optimizing Fe-Si sheet manufacturing processes. These findings offer valuable insights for improving the manufacturing and performance of Fe-Si sheets, emphasizing the need for further exploration of texture effects on magnetic behavior.

Standardisation concept for rapid testing of effects of cutting on losses of electric steel and amorphous ribbon

AbstractSoft magnetic lamination is produced with high width that usually is reduced by cutting. It yields permeability decreases Ɵ and loss increases r. So far, existing corresponding data is not consistent, since derived from strongly different lamination widths W. A consistent, ultra‐rapid test method is suggested, for international standardisation. It is based on a multi‐frequency single sheet tester. A 50 cm long, precisely prepared material sample of W = 17 cm is inserted into it, for an initial measurement in non‐cut state. Then, it is cut into two 8.5 cm wide strips, for a test in cut state. Changes Ɵ and r are evaluated for induction values B up to 1.8 T. They are rapidly measured for frequencies of 50, 400 and 1000 Hz. Results from steel are described for guillotine cutting, from amorphous ribbon also for scissors. As a general tendency, Ɵ exceeds r by an order of about 3, however, with low reproducibility. Thus, standardisation is suggested for loss‐rise functions r(B) only. Examples of r‐functions reveal strong individual differences, as foot‐prints of different products. With increasing f, r‐values tend to sink. With increasing B, they rise, except for high B of NO steel. Amorphous ribbon shows non‐clarified deviating tendencies. Standardisation of r‐tests promises comparable information on cutting effects, for a given material, through a given cutting tool—but also on the tool's state of wear.

The SF and remanence evaluation of magnetic shields based on SST for low-frequency and degaussing situation

As the dominant shielding functional material, the permalloy sheet primarily determines the static and low-frequency shielding performances of magnetically shielded room (MSR). However, the lack of measurement of shielding sheets for practical use would lead to a non-negligible evaluation error in MSR performance. Therefore, an estimation technique of shielding factor (SF) and the remanence of MSR is proposed in this paper while considering the nonlinear magnetic characteristics of the permalloy sheet tested by a single sheet tester for low-frequency field and degaussing situation (L-D-SST). First, a high-accuracy measurement system, comprising L-D-SST (for exciting magnetic field and sensing the corresponding B and H) and the control system (for applying excitation to L-D-SST and amplifying, filtering, and collecting B and H signals), is established. Weak magnetic fields at low frequencies and decaying alternating demagnetizing field excitations are separately applied to the L-D-SST for basic magnetization curves (BM curves) and an anhysteretic magnetization curve (AM curve) tests. Furthermore, the BM and AM curves are respectively integrated with the FEM algorithm for accurate and reliable estimations of the SF and remanence of MSR in an operational state. In addition, the tested magnetic properties are applied for the optimization of MSR shielding quality.

Basic properties of ferromagnetic vector hysteresis play models and their validation by finite element method

PurposeMagnetic hysteresis holds significant technical and physical importance in the design of electromagnetic components. Despite extensive research in this area, modeling magnetic hysteresis remains a challenging task that is yet to be fully resolved. The purpose of this paper is to study vector hysteresis play models for anisotropic ferromagnetic materials in a physical, thermodynamical approach.Design/methodology/approachIn this work, hysteresis play models are implemented to interpret magnetic properties, drawing upon classical rate-independent plasticity principles derived from continuum mechanics theory. By conducting qualitative and quantitative verification and validation, various aspects of ferromagnetic vector hysteresis were thoroughly examined. By directly incorporating the hysteresis play models into the primal formulations using fixed point method, the proposed model is validated with measurements in a finite element (FE) environments.FindingsThe proposed vector hysteresis play model is verified with fundamental properties of hysteresis effects. Numerical analysis is performed in an FE environment. Measured data from a rotational single sheet tester (RSST) are validated to the simulated results.Originality/valueThe results of this work demonstrates that the essential properties of the hysteresis effects by electrical steel sheets can be represented by the proposed vector hysteresis play models. By incorporation of hysteresis play models into the weak formulations of the magnetostatic problem in the h-based magnetic scalar potential form, magnetic properties of electrical steel sheets can be locally analyzed and represented.

Repeatability and reproducibility of physically consistent single sheet testing with H-coil

Measurements of magnetic losses of electric steel are usually performed by International Electrotechnical Commission standardized Epstein testers or Single Sheet Testers (SSTs). According to round robin tests, the corresponding levels of repeatability are of the order of 0.1%, and those of reproducibility are of the order of 1%. However, orders of absolute accuracy are unknown due to the applied “current method.” Here, we report corresponding tests for the so-called “physically consistent SST.” Consistency is achieved by a “giant” tangential field coil on a 50 cm long and 17 cm wide soft magnetic sample, using a thin amorphous yoke for magnetization. Tests were made in two labs with very different working conditions (sea levels of 200 and 1100 m, respectively), with very similarly built-up testers. Measurements were made for peak inductions between 1 and 1.9 T. For two distributed samples, the repeatability errors were lower than 0.3%, and the reproducibility errors were lower than 1%. This indicates that SSTs with an H-coil are not less reliable than current based ones. However, the absolute accuracy can be estimated to be much better, being close to 2%.

A new approach in the implementation of insulating layers in soft magnetic composite materials

Soft Magnetic Composite (SMC) materials show a high potential for growth in the electrification of several industrial sectors for two main reasons: the reduced eddy current losses and the 3D magnetic path which allows to redesign magnetic circuits without geometrical constraints. On the other hand, some material limitations and process restrictions limit the use of SMC on a large scale; this contribution aims to overcome such constraints through a novel surface approach using a Layer-by-Layer (LbL) technique that allows to coat each particle with a nanostructured layer, providing electrical insulation enhanced mechanical strength and withstanding higher treatment temperatures. Four SMCs encompassing the developed innovative multi-functional layers have been prepared and deeply analyzed with a characterization campaign through the study of the surface morphology with a Scanning Electron Microscope (SEM), the magnetic properties with a Single Sheet Tester (SST) and the mechanical strength through the “Transverse Rupture Strength” (or TRS) test. The discussion on the results has to be considered a starting point for future investigations, as each of the four different systems represents a partial solution to a specific SMC problem. Also, some considerations on the possible application are proposed.

Magnetic Flux Paths in Single Sheet Tester as Modeled Numerically

Magnetic Flux Paths in Single Sheet Tester as Modeled Numerically

Energy loss analyses of amorphous magnetic ribbons by multi-frequency single sheet tester

Due to low values of both thickness and conductivity, Fe-based amorphous soft magnetic ribbon (AR) is an attractive alternative to crystalline silicon steel (CS) for elevated frequencies f up to several kHz. On the other hand, for corresponding tests of losses P, the only standardized method is restricted to just 400 Hz. Recently, we reported “Physically Consistent Loss Testing” (CLT) for loss tests of CS for f up to 10 kHz. Here, we describe an adaptation of a corresponding multi-frequency single sheet tester for AR-applications. The CS single sheet is replaced by six 50 cm long and 17 cm wide ARs, loosely inserted into a paper envelope. This “envelope technique” provides (i) simple sample arrangement in an absolutely flat state, (ii) high repeatability, (iii) robust sensor signals, (iv) avoidance of loss increases due to magneto-mechanical effects, and (v) averaging over thickness variations of ARs through as much as 100 g of sample mass. Here, we report the results of frequency analyses for sinusoidal magnetization in the longitudinal direction for induction up to 1.5 T for f < 1 kHz and 0.4 T for 10 kHz, with P up to 50 W/kg. Anisotropy tests confirm a very weak dominance of the transverse direction. In conclusion, CLT proves to be an effective tool for loss tests on both CS and AR as a physically consistent principle. Therefore, for the ongoing standardization of SST with H-coil, we recommend considering the integration of the “envelope technique” in order to establish rapid and universal multi-frequency loss testing.

Single sheet tester for measuring core losses with novel adaptive algorithm of waveform

Single sheet tester for measuring core losses with novel adaptive algorithm of waveform

Measurement and simulation of a rotational single sheet tester

Measurement and simulation of a rotational single sheet tester

Development of an PCB-based Field Metric Measurement System for the Rotational Single Sheet Tester

Development of an PCB-based Field Metric Measurement System for the Rotational Single Sheet Tester

Effects of simultaneous loading of temperature and biaxial stress on the 1&2D magnetic properties of non-oriented electrical steel sheets

As the effect of factors like temperature and stress on the magnetic properties of electrical steel materials are gradually being emphasized, many research teams are carrying out related tests. Currently, most studies focus only on the effect of a single factor on the magnetic properties, while in reality, multiple factors exist simultaneously in electrical equipment. Therefore, accurate data of alternating (1D) and rotational (2D) magnetic properties under simultaneous loading of temperature and stress are very important. In this paper, a system based on a vertical rotational single sheet tester (VRSST) with temperature and stress loading parts is designed and constructed. Then, the 1D and 2D magnetic properties under many combinations of different temperatures, uniaxial and biaxial stress are measured and analyzed.

Ultra-Fast Heating Treatment Effect on Microstructure, Mechanical Properties and Magnetic Characteristics of Non-Oriented Grain Electrical Steels

This paper focuses on the effect of rapid annealing on Non-Grain Oriented Electrical Steel (NGO) in terms of microstructure, mechanical properties, and magnetic properties. The Ultra-Fast Heating (UFH) tests were performed by a transversal induction heater on NGO electrical steel samples (cold rolled down to 0.5 mm), varying the heating power (80 kW and 90 kW) and the speed of the strip through the induction heater. This allowed us to exploit heating rates (HR) in the range of 200–300 °C/s and targeting peak temperature (Tpeak) up to a maximum of 1250 °C. The comparison between the microstructure as obtained by conventional annealing and the ultra-fast heating process highlights a clear effect in terms of grain size refinement provided by the UFH. In particular, the average grain size as obtained by UFH ranges two/three times lower than by a conventional process. The results show the possibility of applying UFH to NGO steels, targeting mechanical properties such as those obtained by the standard process, combined with the benefits from this innovative heat treatment in terms of green energy and the minimization of CO2 emissions. Magnetic characterization performed by a single sheet tester (30 × 90 mm) showed that the values of core losses are comparable with conventional NGO grades.

A new approach to measure fundamental microstructural influences on the magnetic properties of electrical steel using a miniaturized single sheet tester

Magnetic properties of electrical steel are usually measured on Single Sheet Testers, Epstein frames or ring cores. Due to the geometric dimensions and measurement principles of these standardized setups, the fundamental microstructural influences on the magnetic behavior, e.g., deformation structures, crystal orientation or grain boundaries, are difficult to separate and quantify. In this paper, a miniaturized Single Sheet Tester is presented that allows the characterization of industrial steel sheets as well as from in size limited single, bi- and oligocrystals starting from samples with dimensions of 10 × 22 mm. Thereby, the measurement of global magnetic properties is coupled with microstructural analysis methods to allow the investigation of micro scale magnetic effects. An effect of grain orientation, grain boundaries and deformation structures has already been identified with the presented experimental setup. In addition, a correction function is introduced to allow quantitative comparisons between differently sized Single Sheet Testers. This approach is not limited to the presented Single Sheet Tester geometry, but can also be used to compare the results of Single Sheet Testers of various sizes. The results of the miniaturized Single Sheet Tester were validated on five industrial electrical steel grades. Furthermore, first results of differently oriented single crystals as well as measurements on grain-oriented electrical steel are shown to prove the additional value of the miniaturized Single Sheet Tester geometry.

Relative control of domains’ structure in Grain-Oriented electrical steels by Ultra-Short Pulsed laser ablation process

This paper investigates the impact of surface Ultra-Short-Pulsed-Laser ablation process (USPL), mainly the groove depth, shockwave pressure and pattern, on magnetic characteristics of Grain-Oriented Electrical Steels (GOES) by using the Tensor Magnetic Phase Theory (TMPT). A sensitivity analysis to key laser parameters helps specifying the process thanks to a relative control of the surface magnetic structure (Magneto-Optical Indicator Film (MOIF)), dynamics and the behaviors (Single Sheet Tester (SST)) that follow.

Influence of the geometric parameters of a vertical rotational single-sheet tester on sample field homogeneity

PurposeThe horizontal rotational single-sheet tester (RSST) suffers from weaknesses such as the reduced size of test samples, measurement disturbances due to magnetic flux leakage and nonhomogeneity of field in the measurement area. Although the vertical RSST allows to overcome the first two aforementioned drawbacks, the heterogeneity of the field in the test sample remains an issue. In addition, there is still a lack of device standardization to ensure test repeatability, as already is well established with the Epstein frame. This paper aims to investigate the influence of several parameters on the field homogeneity in the test sample.Design/methodology/approachA fully 3D finite element model of a vertical RSST is developed and used to perform a sensibility study on several geometrical parameters.FindingsThe influence of several parameters on the field homogeneity in the test sample, such as the geometrical dimensions of the yokes, the presence or not of holes drilled inside the test sample for B-coil placement as well as the size of the H-coils and B-coils, is addressed.Originality/valueIt is expected that this study will contribute to the optimization and standardization vertical RSSTs.

Physically consistent testing of large-frequency-band magnetic losses of non-oriented electric steel considering dynamic anisotropy

Non-oriented (NO) magnetic steels show gradually increasing relevance over an extended range of frequencies, in particular for electric drives. However, until now, data for corresponding characteristics like losses P are available in very restricted ways. A reason is that loss testers are standardized for technical low frequency (LF) until now. Here we report detailed loss data for three steel types, tested by broad-band single sheet testers that offer tests up to high frequency (HF), for values of f = 10 kHz, for steel samples of 500 × 170 mm2 (or 500 mm). In solving a specific problem of NO steel, very high values of H of magnetic field strength are considered by “True Field Air Flux Compensation.” For rising f, the three steels show strong, non-linear increases in losses P, up to about 100 W/kg. With respect to anisotropy, corresponding factors were defined for rolling direction and transverse direction (TD). The effective “field anisotropy” AH tends to show high values for LF but sinks dramatically for HF due to strong eddy currents. The analogously defined “loss anisotropy” AP is lower a priori. In addition, decreases in HF are less pronounced. The International Electrotechnical Commission-standardized “loss anisotropy factor” is generally lower by more than a factor of two, with values up to 30% for LF that may sink to zero for HF due to eddy current mechanisms that are rather independent from crystalline texture. In conclusion, for high dynamics, the effective anisotropy deviates completely from LF-based texture characteristics. Additional analyses of power functions prove that during a period of magnetization, strong anisotropy exists with respect to alignments of atomic moments, in particular for the TD.

A Non-Invasive Methodology for Magnetic Characterization of Transformers and Reactors

The lack of data is a hindrance to the experimental determination of magnetic cores characteristics. This work presents a non-invasive and field-applicable methodology for electromagnetic devices characterization. Based on fundamental equations of electromagnetism and routine tests, the methodology was applied to obtain, at low frequency: the core loss separation, the hysteresis loop and its BH curve of a three-phase dry core-type transformer. The required equipment and the procedures to do the characterization are presented and discussed. The results were compared with experimental data obtained from tests that were carried out on the same material using a Single Sheet Tester device. The results show a difference in losses of 4.9% for hysteresis, 1.5% for dynamic, and 3.3% for total losses. In the no-load test comparison there was a difference of 4% for dynamics and 1.8% in total losses. The proposed methodology can be applied to different magnetic core types as well as to single-phase transformers and reactors.

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.

Discriminating the physical impacts of various laser pulses on the magnetic structure of oriented electrical steels

Pulsed laser technologies with Long (LPL Irradiation), Short (SPL Scribing) and Ultra-Short (USPL Ablation) pulse duration can be used on SiFe Grain Oriented Electrical Steels (GOES) to refine the domains and reduce the power loss. The corresponding physics related to the magnetic structure is still a subject of research. This paper identifies separate characteristics responsible for the domains structure and the magnetization properties in a GOES sheet processed with the three laser pulses. Magnetic domains based properties are identified thanks to an average dynamic μ-νc-Λ model, the Tensor Magnetic Phase Theory (TMPT), magnetic measurements/observations with the Single Sheet Tester (SST) and the Magneto-Optical Indicator Film (MOIF) technique.