Superposition Of Magnetic Field Research Articles

Circumferential multi-point corrosion status assessment of steel cables considering self-magnetic flux leakage superposition effect

With the advantages of convenient operation and efficient detection, the self-magnetic flux leakage (SMFL) has become an important technology for non-destructive testing of ferromagnetic materials. However, the multi-point corrosion status of steel cable structures is still difficult to precisely assess. In this study, the SMFL theoretical model for the circumferential distribution of steel cable corrosion was established, and the measurement experiment of circumferential multi-point corrosion status was carried out. The results show that the area of circumferential distribution region S, the accumulated magnetic field intensity A and ellipticity e are all positively and quadratically correlated with the corrosion ratio α and defect angle θ of steel cables. Moreover, the magnetic field superposition effect shows an exponential decay trend with the defect interval angle Δφ. The maximum deviation rate of A was less than 10 % under different multi-point corrosion distributions, verifying the principle of magnetic field superposition. Finally, the assessment method based on the effect was proposed, which could accurately and systematically diagnose the circumferential multi-point corrosion status in steel cables.

Density and surface tension measurements of molten Al–Si based alloys

AbstractThis study is part of a series of studies aimed at measuring the thermophysical properties of molten phase change material-type metallic thermal energy storage materials near 873 K (600°C). The target material is Al–Si based alloys. First, as a feasibility study, density measurements of the molten state of three Al–Si binary alloys (Al–12.2Si, Al–50Si and Al–90Si in atomic%) were performed. A highly accurate non-contact density measurement method based on the static magnetic field superposition electromagnetic levitation (EML) method was employed as the density measurement method. The validity of this experimental method was confirmed, and density of molten Al–Si base alloys (ADC12 and Al–5.9mass%Si–1.6mass%Fe) were measured as a function of temperature with an expanded uncertainty of 1.2%. In addition, the surface tension of the alloys was measured by the droplet oscillation method using the EML technique. The surface tension was successfully obtained as a function of temperature with expanded uncertainty of 2.3%.

Plasma Confinement in the L-2M Stellarator at High Microwave Heating Powers

The results of experiments on high-temperature plasma confinement in a quasi-stationary fusion facility are presented. The results were obtained on the L-2M stellarator in which superposition of magnetic fields with three-dimensional spatial symmetry is created with the help of external windings. The plasma was created and heated using microwave pulses with a record specific power of 2 to 4 MW/m3. Under these conditions, spontaneous transition processes were observed in a plasma stable with respect to large-scale instabilities, leading to an abrupt increase in energy. High thermal loads on the wall of the vacuum chamber are observed in the area of the helical separatrix, which leads to an increase in the penetration of impurities into the plasma. Plasma energy and confinement time correspond to L-2M single-machine scaling at lower powers while at specific powers above 3 MW/m3, confinement time decreases due to the accumulation of impurities. The research results can be used to develop fusion energy facilities or to simulate astrophysical phenomena.

Experimental study of vibration effect on self-magnetic flux leakage measurement of corroded steel strands

The self-magnetic flux leakage (SMFL) method has excellent potential in corrosion measurement research of bridge stay cables and suspenders. However, the vibration effect in the cable’s SMFL measurement is unclear and short of the systematic experimental analysis. Based on the magnetic field superposition principle, this study interpreted the vibration effect on steel cable structure magnetic field. The effect was innovatively summarized by the magnetic field increment resulting from the measuring displacement (ΔBDis) and the defect deformation (ΔBDef). Then, the SMFL measurement experiment of the corroded steel strands during the vibration was carried out. The magnetic field distribution law and the influence of the corrosion loss ratio were also analyzed. The results show that ΔBDis presents a “zero value” distribution law via the statistical histogram. The increment of the magnetic field under vibration mainly depends on ΔBDef, which positively correlates with the structure’s corrosion degree and deformation curvature. An excellent linear correlation between the comprehensive characteristic parameter γsum and the corrosion ratio is obtained. So, the quantitative characterization analysis method under vibration was proposed, and γsum can weaken the vibration effect on the magnetic characteristics of cable structure.

Magnetic-assisted strategy for performance enhancement of flow-by capacitive deionization

Capacitive deionization is an environment friendly electro-sorption desalination technology that has broad application prospects in high-efficiency seawater desalination and brackish water purification. However, the insufficient ion separation performance and desalination capacity restrict the large-scale application of capacitive deionization with flow-by structure. Since the separation of cations and anions is intensified via the synergetic manipulation of the electric field force and Lorentz force, a magnetic-assisted strategy was proposed to enhance the performance of capacitive deionization. The effects of magnetic field strength and layout on the desalination performance of capacitive deionization were experimentally investigated. The results confirmed the feasibility of performance enhancement via the effect of the magnetic field. The performance of capacitive deionization under a vertical magnet layout was increased by 25.2 % at a magnetic field strength of 0.33 T, compared to that without a magnetic field. However, the deionization performance decreased when the magnetic field strength was further increased to 0.45 T, which indicates the existence of a critical magnetic field strength. Benefitting from the superposition of magnetic fields, the horizontal layout of magnets can provide a stronger average magnetic field than the vertical layout. This study provides insights into a new design of flow-by capacitive deionization.

Helmholtz Coils Based WPT Coupling Analysis of Temporal Interference Electrical Stimulation System

Electrical nerve stimulation (ENS) is clinically important in treating neurological diseases. This paper proposes a novel temporally interfering wireless power transfer (WPT) system, based on Helmholtz coils, to address energy depletion and the miniaturization of wireless power transfer systems for implantable devices. Compared to conventional WPT systems, this paper uses Helmholtz coils with a centrosymmetric structure as the transmitting coils. A more uniform and stable magnetic field was obtained through structural improvements. It also improves the problem that changes in the receiving coil’s position affect the transmission power’s stability. Based on the principle of temporal interference (TI), two transmitting coils with a slight frequency difference generate a superposition of magnetic fields on the receiving coil and then induce a low-frequency electrical signal on it. The electrical stimulation system applies stimulation parameters of a specific intensity and frequency directly to the target nerve with electrodes connected to it. This eliminates the need for the conventional high-frequency signal to low-frequency signal processing circuitry and reduces the device’s size. In this paper, numerical calculations and an experimental verification of the proposed system are carried out. The magnetic field distribution and the receiving coil current waveform of the system were tested to verify the effectiveness and stability of the proposed design. The experimental results showed that the proposed wireless power transfer system can generate electrical signals of the desired waveform in the receiving coil. Its frequency of 10 Hz and amplitude of 42.4 mA meet the requirements for the electrical stimulation of the sciatic nerve.

Magnetic Flux Density Superposition in Nonlinear Anisotropic Ferromagnetic Material and Resulting Magnetic Barkhausen Noise

Tetrapole probes, also known as double-core probes, which consist of two pairs of orthogonal electromagnets, apply orthogonal magnetic fields to the surface of a ferrous sample and rotate the field by superposition of these fields. Tetrapole probes have the potential to perform rapid characterization of the magnetic anisotropy of ferromagnetic materials. Conventional understanding dictates that magnetic field superposition is linear. However, superposition in ferromagnetic materials is inherently nonlinear. In this work, an equation for the magnetic flux density generated by superposition of orthogonal fields from a tetrapole probe in a ferromagnetic, anisotropic, single net easy-axis material, is derived, along with an equation for magnetic Barkhausen noise root mean square (rms) and energy, for application to materials with flat surfaces. The model approximates the nonlinear superposition as cubic, inline with analogous optics results, and is accurate for low applied fields. Data, which are accurately fit with the model, are shown. The model facilitates useful analyses of measurements made by tetrapole probes and addresses the inherent nonlinearity of magnetic fields applied to ferromagnetic materials.

Numerical simulation for magnetic field analysis and magnetic adsorption behavior of ellipse magnetic matrices in HGMS: Prediction magnetic adsorption behavior via numerical simulation

Magnetic matrices are the core components of HGMS systems. In this study, the induced magnetic field distribution characteristics of ellipse magnetic matrices are investigated via numerical simulation. Besides, the effects of magnetic matrices structure parameters and magnetic field distribution characteristics on the cumulative adsorption behavior of magnetic particles are also discussed. First, the numerical simulation results indicated that compared with the simulation results of a single magnetic matrix, the multi-matrix composite system simulation results demonstrate that an interaction of the induced magnetic fields generated by the superposition of magnetic fields is enhanced with the increase in the long axis size or the decrease in the gap between the matrices, heightening the magnetic induction but leading to the magnetic field gradient and magnetic field forces to significantly decrease near the surface of the matrix. And the rapid reduction of the magnetic field forces around the single matrix leads to a reduction in the range of action. However, to a certain extent, the interaction of the induced magnetic fields also will make the scope of the magnetic field force expand with the decrease in the gap between the matrices. The magnetic cumulative adsorption tests prove that it is feasible to infer the adsorption behavior of magnetic particles through the numerical simulation and theoretical calculations. The adsorption morphology of magnetic particles on the surface of magnetic matrices show that the repulsive region of magnetic particles is perpendicular to the direction of magnetic field, and the adsorption region of magnetic particles is parallel to the direction of magnetic field and with the increase of the size of magnetic matrices, the effective adsorption area of magnetic particles on the surface of magnetic matrices decreases gradually. Besides, with the increase of the horizontal gap between adjacent magnetic matrices, the adsorption thickness of magnetic particles on the surface of magnetic matrices decreases. Moreover, with the expansion of the horizontal gap between the adjacent magnetic matrices, the adsorption amount of the magnetic particles gradually decreases due to the decrease of the adsorption area and fill rate. The adsorption amount of magnetic particles will decrease as the long axis size increases when the fill rate of the magnetic matrices is similar.

HELIOTRON MAGNETIC SYSTEM OF A FUSION NEUTRON SOURCE

Numerical calculations have been carried out on magnetic field of heliotron magnetic system with a region of stellarator and mirror-type magnetic field superposition. Formation of a region of magnetic field superposition takes place in the gap between two helical coil sections which have reduced pitch length L in comparison with pitch length L0 of the heliotron helical coils, L=L0/3.

Continuous power regulation in wireless power transfer system with a new magnetic field superposition transmitter

The research of transmission power is always an essential and hot topic in the wireless power transmission (WPT). To control transmission power efficiently, a continuous power regulation in WPT for small and medium power appliances is proposed. This paper designs a new transmitter with two coils nested inside each other. The transmission power is adjusted by the phase difference of the current between the two coils. Firstly, analyse the transmission power theoretically. The formulae for transmission power and phase difference is obtained. Secondly, graph the function of the formula. Maxwell is used to simulate the magnetic field strength. Finally, build an experimental platform and verify the power regulation effect. The incandescent light bulb is used to regulate in the range of 0.26 W–12 W continuously. In a word, the simulation and experiment results show that the proposed system can regulate the power transmission continuously under the phase-shifting principle.

Calculations of a Magnetic Gear by the Method of Separation of the Fourier Variables

Magnetic gears can be divided into two groups: uncontrollable reducers constructed on permanent magnets and controlled ones that contain, in addition to magnets, the stator winding with a frequency converter. The first group has a fixed coefficient of magnetic reduction, while, for the second group, it can be changed by means of a frequency converter. The suggested field analytical calculation method can be used to determine the functional properties of both types of these devices with a use of two Cartesian coordinates x and y. In each active region of the magnetic gear (air gaps, magnets, stator and rotor yokes, a rotor with through teeth and grooves (modulator)), the sought variables, i.e., magnetic potentials and magnetic inductions, are represented as a product of two functions, the first of which is affected by coordinate x and the other by coordinate y. These functions are also multiplied by some unknown constants, the values of which taken are from the boundary conditions of the magnetic field on the interface lines of active regions. The magnetic permeability of ferromagnetic regions (yoke, modulator rods) are assumed to be fixed, with their values being adjusted according to the calculations of magnetic circuit of the reducer. This approach makes it possible to implement the principle of superposition of magnetic fields formed by the rotor and stator sources, respectively. In this case, the calculations of the unknown constants are carried out twice for each source, since the latter have fundamentally different numbers of poles and, hence, have a different spectrum of harmonic components of the magnetomotive forces. The proposed method makes it possible to determine the magnetic inductions in working air gaps of the magnetic gear and the electromagnetic moments that act on the rotors and the stator. The results were confirmed by the experimental data. To implement the method, a set of functions available in the Mathcad mathematical program is enough.

Research on the efficiency of multiphase wireless power transfer system with phase-shift control and magnetic field superposition

ABSTRACT The efficiency of a multiphase wireless power transfer (WPT) system varies with the size and position of loads. Based on the traditional WPT system, the efficiency improvement of three-phase WPT system under load variation was studied. A three–phase shift control (PSC) strategy is proposed. Mathematical formula of optimal resistance is deduced and the optimal phase shift angles (PSA) for maximum efficiency are presented in the three-phase WPT system. Through the analysis of the electromagnetic model of the system, the optimal phase angle at which the load maintains optimum efficiency at different locations is deriving. A three-phase WPT phase experimental platform based on PSC is built. Verify the validity and correctness of PSC strategy. Simulation and experimental results show that the efficiency of the receiving coil can be increased by 10−15% after the phase is adjusted at different positions. The proposed three-phase phase shift control strategy has a guiding and reference significance for subsequent related research.

Simulation and experimental investigation of a multi-pole multi-layer magnetorheological brake with superimposed magnetic fields

This paper presents comprehensive investigations on a new multi-pole multi-layer magnetorheological (MR) brake. This unique design features MR working gaps set between two-layer individual coils. Independent current supply was proposed to generate more flexible braking torque and lower power consumption. In this article, an exploded-view drawing of the proposed MR brake was presented, and theoretical analyses of the braking torque and temperature characteristic were conducted. Then, finite element analysis was performed to verify the effect of the magnetic field superposition. A prototype MR brake was fabricated and tested to evaluate the magnetic field superposition, preliminary dynamic behavior, temperature and the performance of individual input current. The results show that the magnetic field superposition has much influence on the braking torque, and individual current supply results in different power consumption and torque ranges. Moreover, the dynamic response performance of this brake is less affected by the slip speed. Furthermore, the maximum steady-state slip power of the proposed brake is about 160 W, and the greater the slip power is, the faster the temperature increases. The results also have verified the correctness of the structure and magnetic circuit design.

ЕКСПЕРИМЕНТАЛЬНІ ДОСЛІДЖЕННЯ ПАРАМЕТРІВ ЕЛЕКТРОМАГНІТНИХ ФІЛЬТРІВ

Наведені результати досліджень з розподілу індукції магнітного поля у циліндричному корпусі, заповненому феромагнітною загрузкою, вздовж висоти корпусу при різних діаметрах корпусів. На основі принципу суперпозиції магнітних полів і графічних залежностей встановлено відстані між осердям суміжних електромагнітів при різних діаметрах корпусів. На основі досліджень запропоновано конструкцію електромагнітного фільтра з використанням тангенціальних електромагнітів, розміщених по відношенню до корпусу з загрузкою у взаємно перпендикулярних площинах. Запропоноване технічне рішення дозволяє створити по висоті корпусу у феромагнітній загрузці однакові умови для ефективного осадження магнітних домішок.

Enhancing the effectiveness of calculation of parameters for short circuit of three­phase transformers using field simulation methods

We conducted theoretical research into electromagnetic processes when testing power transformers under the mode of the test short circuit based on a three-dimensional model of the magnetic field in the frequency statement. Reliability and accuracy of determining the parameters for the test short circuit of the power transformer for frequency-domain statements were substantiated with the use of verification of the data of calculation of frequency-domain and time dependent models of the magnetic field for frequency statements. The main regularities of the magnetic field distribution in the volume of the active part of the transformer were determined. In the magnetic field localization zones, 3D intensity distribution is uniform and is determined by the 2D distribution in the horizontal cross section of the active part in the middle of the phase windings height. The values of the axial component of the magnetic field intensity approach 96–97 % of the intensity vector module. An effective approach to field modeling was implemented based on decomposition of the computational domain into spatial zones. Each calculation zone is put in compliance with an electrical circuit of the substitution scheme. Distribution of electric potentials in the horizontal cross-sections of the conductors between the coils or between the turns of windings was accepted as uniform. The superposition of magnetic fields in spatial zones was implemented by means of dynamic synthesis by the criteria of minimal current error for electric circuits of the substitution scheme. The decomposition of the 3D area of field simulation area into the central and end zones is implemented at a distance of 10–15 % of the height of the phase windings, which ensures high accuracy of the magnetic field calculation with the error not exceeding 1.62 %. Time consumption for field simulation of electromagnetic processes under the mode of the test short circuit decreased by 5 times and requirements for the capacity of computing hardware resources decreased by 4 times. High accuracy of identification of parameters of the test short circuit of three-phase transformers was proved by comparing the calculation data to the results of tests at the private company Eltiz (Zaporizhzhia, Ukraine). Calculation errors do not exceed 1.42 % for active losses and 1.39 % for short circuit voltage. The proposed approach with the use of the methods of decomposition and of dynamic synthesis makes it possible to significantly improve the effectiveness of the preliminary stage of design preparation of production and can be used for solving the problems of design solutions optimization

ВЛИЯНИЕ МАГНИТНЫХ ПОЛЕЙ НА СТРУКТУРУ И ФИЗИКО-МЕХАНИЧЕСКИЕ СВОЙСТВА АЛЮМИНИЯ

With the development of modern technologies, a growing number of plants forming magnetic fields around themselves appear. Since most of the structures and mechanisms operate under the mechanical stresses leading to the de-struction, the study of metals behavior under the external energy conditions is necessary to analyze their operational life. To carry out the study, it was decided to use commercial-purity A85 aluminum as a research material. Since at present aluminum dominates the non-ferrous metals market and is widely used in machine building, electrical industry and tool engineering, industrial and civil construction, etc., the issue of modifying this material is very topical. In this paper, the authors study the influence of weak magnetic fields up to 0.5 T on the structure and deformation char-acteristics of aluminum for the possibility of plasticizing the material and further application of this technology in the pro-duction, as well as for deeper study of theoretical part of this phenomenon and the construction of theory on the influence of magnetic fields on physical and mechanical properties of paramagnetic metals. During the study, it is found out that the effect of the magnetic field influence is not unambiguous: the creep rate both increases reaching the maximum value at 0.1 T, and slows down reaching the minimum value at 0.5 T. We can note that during the experiments, it became possible to plasticize the material under investigation by influencing it with the magnet-ic field. The distributions of the grain structure of samples destroyed under the creep conditions with and without the mag-netic field superposition are unimodal and can be described by a lognormal law.

МАГНИТНЫЙ ДВИГАТЕЛЬ ДЛЯ КОСМОСА (ПОЛНАЯ ВЕРСИЯ)

Subject of interstellar flights remains actual taking into account limitedness of the terrestrial resources, overpopulation of the planet, and demographic, sociopolitical and ecological problems at the planet. A constructive solution is submitted of the construction of a spacecraft moving with acceleration resting upon electromagnetic fields of the Solar system and the Galaxy. Calculation of the current intensity within the circuit and charge value at the object's useful surface necessary for the achievement of acceleration equal to 1g at arbitrary direction in the space is conducted. A method of levitation in magnetic fields of planets (superposition of magnetic fields of a star and a planet) and interplanetary space (superposition of magnetic fields of galaxies) without using the Coulomb force is proposed.

Apparatus for investigating resonance with application to magnetic resonance imaging

Resonance is typically studied in the context of either a pendulum or a mass on a spring. We have developed an apparatus that enables beginning students to investigate resonant behavior of changing magnetic fields, in addition to the properties of the magnetic field due to a wire and the superposition of magnetic fields. In this resonant system, a compass oscillates at a frequency determined by the compass's physical properties and an external magnetic field. While the analysis is mathematically similar to that of the pendulum, this apparatus has an advantage that the magnetic field is easily controlled, while it is difficult to control the strength of gravity. This apparatus has been incorporated into a teaching module on magnetic resonance imaging.

DC-Bias-Superposition Characteristics of Ni0.4Zn0.2Mn0.4Fe2O4 Nanopowders Synthesized by Auto-Combustion.

Ni0.4Zn0.2Mn0.4Fe2O4 nanopowders were prepared by auto-combustion method. The as-synthesized powders were characterized using X-ray diffraction (XRD) and thermo-gravimetric-differential thermal analysis (TG-DTA), and the powders were densified at different temperatures 400 degrees C, 500 degrees C, 600 degrees C and 700 degrees C/4 hrs using conventional sintering method. The sintered samples were characterized by XRD and transmission electron microscope (TEM). The bulk densities of the samples were increased with an increase of sintering temperature. The grain sizes of all the samples vary in between 18 nm to 30 nm. The hysteresis loops show high saturation magnetization and low coercivity, indicates that it is a soft material. The incremental permeability (permeability with magnetic field superposition) was influenced by both ΔM and H(c). A sample with higher initial permeability and favoured the attainment of a higher incremental permeability. The Q-factor was mainly determined by the sintered density and microstructure. To summarize, a uniform and dense microstructure with relatively small average grain size is favourable for obtaining better dc-bias-superposition characteristics, including permeability and Q-factor.

Electromagnetic Field Analysis of Hybrid Excitation Vehicle Generator with Low Voltage and High Current

In order to further improve the power supply system reliability of low voltage high current vehicle generator, hybrid excitation is used and the permanent magnets are added between the main magnetic poles body and pole shoes. Aiming at reply the problem of limited installation space, the asymmetric pole structure, non-uniform commutating pole, single wave windings playing a role of the pressure line and oblique brush etc are investigated for improving commutation. This paper researched on the distribution of the flux line, the waveform of the air gap magnetic field, and analysis inner magnetic field at the loading by hybrid excitation and no loading by permanent magnet excitation alone respectively with the method of finite element. The results reveal that the magnetic field established by several excitation systems is still symmetric and uniform although the asymmetric structure, so it ensures the provision of suitable medium space for mechanical and electrical energy conversion. By comparing the permanent magnets excitation alone and hybrid excitation in a generator magnetic field distribution and air gap magnetic field waveform, the permanent magnet excitation and electricity excitation realized the superposition of magnetic field, and common establish main generator magnetic field. Hybrid excitation also reduces the current density of excitation coils and improves the heat dissipating performance compared with electrically excited alone. Through the performance analysis of the hybrid excitation, the output voltage waveform is very stable. The curve of auxiliary excitation current along with velocity variation provide important basis for excitation control devices and the development of control algorithm. It will help to improve the stability, reliability and security of the generator, the results can provide key technical support to the development of low-voltage high-current hybrid excitation vehicle generator.