Measurement Of Magnetic Characteristics Research Articles

МІНЕРАЛЬНІ ТА ФІЗИКО-ХІМІЧНІ ЗМІНИ МАГНЕТИТОВИХ КВАРЦИТІВ ВАЛЯВКИНСЬКОГО ТА НОВОКРИВОРІЗЬКОГО РОДОВИЩ КРИВБАСУ В ПРОЦЕСАХ ЇХ ПЕРЕРОБКИ

Background. In order to study the mineral physical and chemical changes that occur with iron ore (magnetite quartzites) of the Valyavkinsky and Novokrivorizky deposits of the Kryvorizka iron ore basin during the mining and processing of ore at the mining and processing plant "ArcelorMittal Kryvyi Rih", the entire technological chain of mining and mineral processing was analyzed: magnetite quartzite (ore) in naturaldeposits → ore after explosion → ore after crushing at crushing plants → intermediate magnetic products and tailings of all stages of beneficiation → final magnetite concentrate. Methods. Laboratory and analytical studies, which include mineragraphic, petrographic, electron microscopic studies of iron ore, X-ray fluorescence method and atomic emission spectral analysis (determination of the content of macro- and microelements in the original ore, magnetic concentrate and tailings), X-ray diffraction analysis, microprobe analysis of magnetic concentrate and tailings, thermogravimetric analysis, chromatographic method (determination of the specific surface of a substance), sedimentation analysis, measurement of magnetic characteristics, etc. were used. Results. It was established that at the first stage of mining production (drilling and blasting, ore crushing in the quarry and at the crushing plant) there are no significant changes in minerals. At the next stage of deep processing and concentration of minerals at the ore beneficiation plant, during which the ore undergoes 3 stages of crushing, classification, desliming, and wet magnetic separation, two completely new products are formed – magnetite concentrate and tailings, which are fundamentally different from the original ore – both at the rock level and at the mineral one. Сonclusions. It was substantiated that in the process of enrichment of magnetite quartzites, the structural and textural characteristics, mineral and chemical composition, state of aggregation of the iron ore, structural and crystallochemical properties of the main ore mineral magnetite change significantly.

Dynamic measurement of magnetic characteristics of switched reluctance motor

Introduction. Switched reluctance motor (SRM) is a type of electric motor featuring nonlinear magnetic characteristics. The flux linkage or inductance profile of SRM is usually required for the purpose of high control performance, and can be normally obtained through conventional static test by using DC or AC method when the rotor is locked. Problem. However, it is not practical to use the conventional method of measurement when the specific apparatus for locking the rotor is unavailable. Besides, due to the magnetic nonlinearity of SRM, the saturation effect makes it difficult to obtain the saturated magnetic characteristics, and the conventional static AC test fails to address this problem. Novelty. In this paper, a dynamic measurement method of the magnetization curves of SRM is proposed which allows the measurement take place while the motor is running with load. Methodology. Based on the conventional static AC test, the proposed measurement handles the saturation problem successfully by introducing a DC offset in the high frequency AC voltage. Phase inductance with different rotor positions and currents can be obtained by analyzing simple equivalent circuit. Practical value. Simulation is conducted in MATLAB/Simulink environment and the results have verified that the proposed dynamic measurement can effectively obtain the magnetic characteristics of SRM.

Definition of limit state of flexible pipe material in coiled tubing technology

Currently, the use of coiled tubing technologies has become widespread in drilling and oil production. The flexible pipes (FP) used in this technology undergo a complex of several impacts that accelerate the process of damage accumulation and thereby cause an accelerated process of seats of destruction formation, which often leads to accidents. Statistics show that the main reason for the destruction of the FP is the fatigue of the material loading and basically it is a cyclic bending according to the repeating stress cycle scheme. This loading scheme has a feature that is associated with the fact that tensile loads occur mainly in the convex zone of the pipe and compressive loads in the concave zone. Since the physical and mechanical properties of steels under stretch and compression are different, the process of damage and destruction accumulation during cyclic stretch and cyclic compression will have a different character. Information about the patterns of changes in the properties of the FP material allows to estimate the period of reaching the limit state and, thereby, prevent accidental destruction. In this regard, fatigue tests were carried out with a step-by-step measurement of magnetic characteristics that are structurally sensitive to the accumulation of fatigue damage. The determination of the stress amplitude for the FP fragment was determined by preliminary calculation in the ABAQUS PC. The test results showed that during cyclic stretch of the samples, the magnetic characteristics for assessing the limit state in the FP material were not informative. Notably in samples loaded with cyclic compression, the results of magnetic characteristics measuring (the resulting intensity and the gradient of the intensity of the constant magnetic field) showed sensitivity to the onset of the limit state. Based on the conducted studies, it is proposed to control the limit state of FP in the concave zone, where compressive loads mainly occur. These measurements allow us to estimate the value of the residual life of the FP material and to put this object out of operation in a timely manner, preventing accidental destruction.

Measurements of magnetic characteristics of laminated Fe-Si steel filter inductors in grid interface converters

The knowledge of the magnetic characteristic of an inductor is a key factor for the design of filters of power converter systems for electric grid interfaces. The accurate and reliable definition and measurement of the parameters such as the differential inductance, the saturation level and the linearity range is a difficult task, in particular for high current inductors. In this paper a comparison between different methods of measure of the magnetic characteristic of a gapped filtering inductor versus current, in the range from zero magnetization to the saturation, is presented and discussed. It is shown that the different measurement methods provide appreciable differences in the evaluation of the magnetic characteristic of a benchmark inductor. The differences found are also analyzed by suitable numerical simulations.

Magneto-structural correlations in Fe-25 at%Al influenced by substitution of Fe by Co and by thermal treatment

The scanning electron microscopy, X-ray diffraction, positron annihilation spectroscopy, Mössbauer spectrometry, and measurements of magnetic characteristics by vibrating sample magnetometer complemented by theoretical simulations are applied in the present investigations of the Fe-Al-Co alloys with 25 at% Al and Co substituting Fe in amount of 15 at% or 25 at%. The alloys prepared by slightly different technologies resulting in different structural morphologies are subjected to thermal treatment followed by slow cooling and water cooling. It is shown that the alloy with lower Co content and the initial A2 structure is more sensitive to the thermal treatments from the viewpoints of changes in morphology, defects concentration and magnetic properties in comparison to the other one with the initial B2 structure. This is reflected almost in all experimentally obtained results.

Magnetic measurement of nanocrystalline alloy based on a single sheet tester

Generally, for the measurement of magnetic characteristics of nanocrystalline alloy, the magnetic circuit length (lm) is assumed as a constant, and magnetic measurement under square waveform is rarely focused. This paper examines that magnetic characteristics of nanocrystalline alloy are measured under sinusoidal waveforms and square waveforms based on a single sheet tester. The factors related to lm are analysed from the tested data under sinusoidal excitations, and a novel method to determine lm is presented, which is then extended to the case under square waveforms. By combining with a power electronic inverter, the influence of power electronic topology on measurements is analysed, and the oscillation mechanism of excitation current of single sheet tester is revealed. As a result, the limitation of the H-coil method for acquiring the magnetic field intensity H under square waveforms is pointed out, and improved magnetic circuit method is introduced. It is shown from experimental results that the proposed measurement system is useful for acquiring magnetisation characteristics of the nanocrystalline alloy.

Concept for soft sensor structure for turning processes of AISI4140

AbstractDuring turning of quenched and tempered AISI4140 surface layer states can be generated, which degrade the lifetime of manufactured parts. Such states may be brittle rehardened layers or tensile residual stresses. A soft sensor concept is presented in this work, in order to identify relevant surface modifications during machining. A crucial part of this concept is the measurement of magnetic characteristics by means of the 3MA-testing (Micromagnetic Multiparameter Microstructure and Stress Analysis). Those measurements correlate with the microstructure of the material, only take a few seconds and can be processed on the machine. This enables a continuous workpiece quality control during machining. However specific problems come with the distant measurement of thin surface layers, which are analyzed here. Furthermore the scope of this work is the in-process-measurement of the tool wear, which is an important input parameter of the thermomechanical surface load. The availability of the current tool wear is to be used for the adaption of the process parameters in order to avoid detrimental surface states. This enables new approaches for a workpiece focused process control, which is of high importance considering the goals of Industry 4.0.

Blocking Temperature of Magnetite Nanoparticles Fe<sub>3</sub>O<sub>4</sub> Encapsulated Silicon Dioxide SiO<sub>2</sub>

One of the important characteristics of magnetic materials is the measurement of magnetic characteristics through Superconducting Quantum Interference Device (SQUID) especially magnetization temperature dependence M(T)ZFC and MTFC measurement. In this work, we reported magnetization temperature dependence measurements of magnetite nanoparticles without SiO2 encapsulation (Fe3O4) and magnetite nanoparticles with SiO2 encapsulation (Fe3O4.SiO2) at the application of magnetic fields of 100 Oe. The nanoparticles magnetite was synthesized by co-precipitation method. It was calculated that the blocking temperature of magnetite nanoparticles Fe3O4 without and with SiO2 encapsulation is 118.38 K and 209.03 K, respectively. The blocking temperatures of magnetic nanoparticles increase by SiO2 encapsulation.

Measurement of high frequency magnetic properties of electrical steel sheet using prototype Rogowski coil

In order to develop a high-efficiency, low-loss, small, high-power, high-speed rotating motor, it is necessary to accurately measure the magnetic properties of electrical steel sheets under PWM excitation. A shunt resistor is generally used for measuring magnetic characteristics, but non-contact current measurement is required. However, iron cores are used in commercially available current measurement sensors, and it is necessary to consider the effects of core characteristics on high-frequency currents. The authors are focusing on Rogowski coils and developing small current / magnetic field sensors specialized for motor and electrical steel sheet evaluation. In this paper, we make a prototype of Rogowski coil, and report on the evaluation of basic electrical characteristics and the results of application to the measurement of magnetic characteristics of electrical steel sheets under sinusoidal excitation and PWM excitation.

Magnetic measurement of permanent magnet by 40 T long pulse magnet

Abstract Permanent magnets, especially Nd-Fe-B magnets are very important engineering elements that are widely used in many applications. Detailed design of electrical and electronic equipment using permanent magnets requires precise measurement of magnetic characteristics. We developed a measurement system which can measure the magnetic characteristics of permanent magnets precisely. This paper presents the measured results of magnetic characteristics of various types of permanent magnets and comparison of these characteristics.

Magnetization and Static Magnetic Susceptibility of Fine-Crystalline High-Temperature YBa2Cu3Oy Superconductors Synthesized by the Sol–Gel Method

A comparative study of the magnetization and static magnetic susceptibility of high-temperature superconductors (HTSC) YBa2Cu3Oy synthesized by two variants of the sol–gel method with different average sizes of crystallites 〈 D〉 ranging 0.4–2 μm has been performed in constant magnetic fields (Н ≤ 6 kOe). It has been shown that the different annealing temperatures and times, at which their crystal structure is formed, change both the average sizes of crystallites 〈D〉 and the sizes of the structural homogeneity regions 〈l〉 and, at the same time, the magnetic field penetration depth (λ) and the coherence length (ξ). As a result, such parameters as 〈D〉 ~ λ and 〈l〉 ~ ξ become comparable, leading to a change in the physical characteristics of HTSCs. It has also been shown that the superconducting transition temperature Tc determined from the measurements of magnetic characteristics in constant magnetic fields remains within values optimal for superconductivity (Tc ≈ 92 K) in the case of an optimal number (y) of oxygen atoms, which determine the levels of charge doping for a given compound.

A study of the magnetic properties of LaNi5-xSix alloys and their hydrides

In this work, we study the influence of the substitution Si for Ni for the magnetic properties of LaNi5-xSix (x = 0-0.5) alloys. The structure of the alloy was tested by X-ray diffraction (XRD) measurements. The magnetic properties of the samples were carried out using a vibrating sample magnetometer (VSM) system. The results showed that when Ni was substituted for Si in alloys and after hydrogen absorption, LaNi5-xSix alloys retained their CaCu5 structure. The susceptibility (χ) of the alloys decreased when substituting Ni by Si increased. The original bulk samples showed a Pauli paramagnetism state after hydrogen absorption transformed into a superparamagnetic state. The results obtained showed that although measurements of magnetic characteristics are relatively simple, quantitative information about the microscopic processes occurring in the material was used as the negative electrode in Ni-MH rechargeable battery.

A procedure for measurement of magnetic characteristics in quasistatic regime

In this paper a procedure for magnetic hysteresis measurement in quasi-static regime with a controlled rate of change of the magnetic polarization is proposed. The waveform of the polarization is modulated by means of iterative augmentation using an inverse approach. The setup, the measurement principle and the logical diagram of the procedure algorithm are presented. Experimental results obtained with the new procedure, applied on soft magnetic materials are presented. The measurements made at 0.1 Hz and 1 Hz show a difference of the characteristic values in the range of 5 % to 8 %. The paper demonstrates that, with this new procedure, quicker and more reliable measurements could be obtained.

New Method of Measurements of Magnetic Characteristics in Two Perpendicular Axis of Amorphous Ribbon

The paper presents new method, which enables measurement of magnetic characteristics of amorphous alloy ribbons in two directions. In presented method a frame shaped core is placed in middle layer of PCB (Printed Circuit Board). Magnetizing and measuring coils on every side of core enable measurements of both axis of tape. The results show, that differences in magnetic properties in two directions of tape caused by anisotropy are limited. Research opens possibility to develop two axis fluxgate sensors and miniature cores for power conversion devices.

Precise measurement of magnetization characteristics in high pulsed field

Permanent magnets, especially Nd-Fe-B magnets, are very important engineering elements that are widely used in many applications. The detailed design of electrical and electronic equipment using permanent magnets requires the precise measurement of magnetization characteristics. High pulsed magnetic fields can be used to measure the magnetization characteristics of permanent magnets in the easy and hard magnetization directions. Errors influencing the measurements stem from the relationship between the tested material, pick-up sensor configuration, and excitation coil. We present an analysis of the effect of the sensor construction on the accuracy of the measurements of the material’s magnetic properties. We investigated the coaxial and series types sensor configurations.

Design and Fabrication of Perpendicular Patterned Magnetic Media Using Nanoimprinted Nano Pillar Patterns

Perpendicular patterned magnetic media have been regarded as a one of candidate to achieve an ultrahigh density magnetic data storage media of over 1 Tb/in2 . One approach to producing patterned magnetic media is deposition of thin magnetic films on pre-etched nano pillar array prepared with nanoimprinting technology. In this paper, we have investigated the feasibility of the polymeric nano pillar patterns on glass substrate, which were replicated by UV nanoimprinting process with the polymeric nanostamp, and magnetic layer deposition technology without additional etching process to fabrication for perpendicular patterned magnetic media. The polymeric nano pillar patterns were replicated by 2-step UV nanoimprinting process by using a silicon nanomaster with nano pillar patterns. We deposited magnetic layers on the nanoimprinted nano pillar patterns to make the perpendicular patterned magnetic media. Finally, we show that the fabricated magnetic media could be used for perpendicular patterned magnetic media by measurement of magnetic characteristics.

DSP-Based Automated Error-Reducing Flux-Linkage-Measurement Method for Switched Reluctance Motors

The switched reluctance motor (SRM) has received considerable attention from researchers for its many inherent advantages, and thus, it has become a popular research topic in the field of variable-speed drives as well as servo drives. Research on SRMs mainly includes their design, modeling and performance analysis, control, as well as applications. However, for verification of design, performance prediction, as well as development of a high-performance sensorless control algorithm, accurate measurement of the magnetic characteristics of the SRM is most critical. Hence, one of the most important problems in the field of SRMs is a practical and accurate instrumentation system for the measurement of the SRM magnetic characteristics. This paper first describes an accurate and fully automated digital method for the measurement of the magnetic characteristic of SRMs, which includes online offset-error removal and winding resistance estimation. In this method, a digital-signal-processor-based virtual instrumentation for measurement of flux linkage is developed. Then, the results of the measurement conducted on a four-phase SRM are presented. The accuracy of the measurement system is verified by comparing with that found via a magnetic analyzer. Finally, the various sources of errors and their contributions to the errors are discussed. The scheme can also be used, in general, for transformers or inductors.

Evaluation by numerical analysis of magnetic shielding characteristics of bulk high‐Tc superconductor containing weak links

AbstractHigh‐Tc superconductors (HTS), which have the characteristics of critical current density over 3 × 104 A/cm2 at liquid nitrogen temperature (77 K) and 1 T, can be produced. Thus, they are promising for many practical applications such as a magnetic bearing, magnetic levitation, flywheel, and magnetic shielding. Since the HTS characteristics are not homogeneous in some specimens due to grain boundaries and cracks, the distribution of magnetic characteristics should be assessed. Thus, we have measured the distribution of the magnetic flux density on the surface of the HTS using a Hall element, and have evaluated its magnetic characteristics. The measurement of magnetic characteristics using a Hall element is difficult regarding the distribution of the magnetic flux density on the actual surface and inside of the HTS sample. In this research, we conducted a quantitative evaluation of the magnetic shielding characteristics of the HTS including weak links under a static magnetic field with the three‐dimensional finite element method analysis. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 146(1): 9–17, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10209

Flux linkage measurement method for switched reluctance motors and inductor/transformers using a real-time DSP system

The switched reluctance motor (SRM) has received considerable attention from researchers for its many inherent advantages, and thus has become a popular research topic in the field of variable-speed drives as well as servo drives. The research on SRMs mainly includes its design, modelling and performance analysis, control, as well as applications. However, for verification of design, performance prediction and development of a high-performance sensorless control algorithm, accurate measurement of the magnetic characteristics of the SRM is most critical. Hence, one of the most important problems in the field of SRMs is a practical and accurate instrumentation system for the measurement of the SRM magnetic characteristics. This paper first describes an accurate, fully automated digital method for the measurement of the magnetic characteristics of SRMs, including on-line offset error removal and winding resistance estimation. In this method, a digital signal processor-based virtual instrumentation for measurement of flux linkage is developed. Then the results of measurement conducted on a four-phase SRM are presented. The accuracy of the measurement system is verified by comparing it with that found via a magnetics analyzer. Finally, the various sources of errors are discussed and their contributions to the errors are quantified. The scheme can also be used in general for transformers or inductors

数値解析によるウィークリンクを含むバルク高温超電導体の磁気遮蔽特性評価

High-Tc superconductors (HTS), which have a characteristic of the critical current density over 3×104 A/cm2 in liquid nitrogen temperature (77K) and 1T, can be produced. Thus, they are promising for many practical applications such as a magnetic bearing, a magnetic levitation, a flywheel, a magnetic shielding and etc.. Since the HTS characteristics are not homogeneous in some specimens due to grain boundaries and cracks, the distribution of magnetic characteristics should be assessed. Thus, we have measured the distribution of the magnetic flux density on the surface of the HTS using a hall element, and have evaluated its magnetic characteristics. The measurement of magnetic characteristics using a hall element is difficult for measuring the distribution of the magnetic flux density on the actual surface and the inside of the HTS sample. In this research, we examined a quantitative evaluation of the magnetic shielding characteristics of the HTS including weak links under the static magnetic field with the three-dimensional finite element method analysis.