Magnetic Shielding Effect Research Articles

An improved circuit model for the estimation of the electromagnetic energy coupling throughout aperture into metallic enclosure

The development and exploration of approximate phenomenological models used to calculate the electromagnetic energy coupling throughout apertures into metallic enclosures is presented in this paper. An analytical approach has been established for the calculation of the electric and magnetic shielding effectiveness (SE, SM) a rectangular metallic enclosure with an aperture and conductor in it by means of Robinson's model. With the existence of inductive and capacitive obstacles, the modal technique is to complete the first one to estimate SE and SM exactly taking into consideration the maximum of propagating modes. The results of the SE and SM obtained by the analytical model are validated by the software CST/EMC and the Finite-Difference Time Domain method (FDTD). Very similar results are obtained between these methods.

Impact of Air Gaps Between Microstrip Line and Magnetic Sheet on Near-Field Magnetic Shielding

This study experimentally analyzed the impact of air gaps between a magnetic sheet and a test board with a microstrip line, which is used to measure the near-field magnetic shielding effectiveness (NSE) of magnetic sheets made of metallic powder. To conduct the measurements, a material fixture equipped with a microstrip line to generate the near magnetic field, a rectangular loop probe, and an automatic probe positioning system capable of moving the loop probe along three axes were designed and fabricated. In addition, to systematically vary the thickness of the gaps, three paper spacers with a thickness of 0.11 mm per paper were used, and a 1.0 mm thick acrylic sheet, along with a specially designed material fixture, was used to press down the magnetic sheets during measurement. The magnetic shielding properties were measured and compared under various air gap conditions using a near-field magnetic loop probe. The effect of the gaps on the shielding performance of the magnetic sheets was quantitatively evaluated for three different magnetic sheets. The experimental results showed that as the gap thickness increased, NSE tended to improve up to a frequency around 1 GHz, while in the higher frequency range of a few GHz, NSE tended to decrease. The physical background of this phenomenon was explained using an equivalent magnetic circuit represented by reluctances for the structure, where the magnetic sheet is placed above the microstrip line with an air gap. This model helps to elucidate how the presence of the air gap affects the near-field magnetic shielding performance.

Aromaticity in Isoelectronic Analogues of Benzene, Carborazine and Borazine, from Electronic Structure and Magnetic Property.

Carborazine (B2C2N2H6) and borazine (B3N3H6) are isoelectronic analogues of benzene (C6H6). The aromatic character of borazine have basically reached a consensus after a long period of controversy, but the related properties of carborazine are even rarely reported. In this work, we systematically investigated the geometric structure, charge distribution, frontier molecular orbital characteristics, bonding, electronic delocalization, magnetic shielding effect, and induced ring current of carborazine and borazine, and compared the studied characteristics with those of benzene to determine the aromatic character of the two analogues. The combination of multiple properties shows that although they are isoelectronic, carborazine is evidently aromatic, while borazine only exhibits rather weak aromaticity. The C atom acting as a connecting bridge between B and N atoms in carborazine reduces the electronegativity difference on the molecular backbone and enhances the electronic delocalization over the conjugated path, which is the essence of the distinct disparity of aromaticity between carborazine and borazine.

An innovative approach to 2D localization using the magnetic shielding effect

The effect on an electromagnetic field when a low-cost magnetically permeable object such as copper or aluminum is placed within it can be observed to determine the object’s location. This approach offers a novel technique to achieve reliable localization, particularly in environments where line of sight sensing methods may be non-applicable. Shields up to a size of 30×30 mm and a thickness of 80 µm were investigated; copper shields of these dimensions reduced the signal strength to 91 %, and aluminum shields reduced the signal strength to 94 % of its initial strength. The distortions to the electromagnetic field were closely related to the location of the tag. By fitting an inverted Gaussian curve to each sensor’s data, the position of a shield along a line could be predicted. This method can be used to locate a tag within a 2D plane by creating a 2D array of sensors beneath the sensing plane.

Effective Electromagnetic Properties of Composite Material Computed From Neural Network Approach

ABSTRACTThanks to their lightweight, composite materials have become widely used in the automotive and aerospace industries. The design of components made from these materials is carried out by numerical modeling which can sometimes be tedious because of the need to take into account the internal structure of these materials. Obtaining the effective properties of an equivalent homogeneous material to replace the composite in our numerical models makes modeling easier. Classical homogenization approaches are not always suitable to obtain these effective properties. This article deals with an inverse problem that consists in computing the electromagnetic properties from the knowledge of the magnetic shielding effectiveness values. For different composite samples, an artificial neural network method is used to predict the effective conductivities from the magnetic shielding effectiveness measurements. The magnetic shielding effectiveness values computed from the predicted conductivities are close to those obtained from the measurements.

Development of a low-power Hall thruster with permanent magnets and a dual trigger electrode hollow cathode for the Qilu satellite constellation

A low-power Hall effect thruster (LpHet-100) has been installed on the Qilu-3 satellite and has been launched by the Long March 2D rocket in January 2023. The specific features of LpHet-100 are presented in this article. An innovative dual trigger electrode poison-resistant hollow cathode and an effective magnetic shielding configuration with permanent magnets, additive manufacturing gas distributor are designed and experimentally verified. The prominent characteristics of a shorter starting time, lower ignition shock, and self-healing have been shown in tests of the dual trigger electrode hollow cathode. Thrust performance tests proved that LpHet-100 can work stably in the power range of 50–230 W and generate a thrust of 2.9–10.8 mN, with the maximum specific impulse of 1594 s and maximum thrust efficiency of 38 %. Rigorous environmental tests were conducted to verify the thruster design scheme. In addition, Torque measurement of Hall thrusters is incorporated into the ground tests for the first time. A plasma torque of 5.65–9.88 μN·m is obtained when LpHet-100 operated in 132–228 W. It provides a critical guideline for the attitude and orbit control schemes of the Qilu-3 satellite, which is an essential part of space mission planning. Generally, this study proposes new design of the thruster body and hollow cathode, providing an exhaustive reference for the development process and application of low-power Hall thrusters.

Differences Between NSA 94–106 and IEEE Std. 299 Setups for Low-Frequency Magnetic Shielding Effectiveness Characterization: A Study Using Numerical Simulations

Differences Between NSA 94–106 and IEEE Std. 299 Setups for Low-Frequency Magnetic Shielding Effectiveness Characterization: A Study Using Numerical Simulations

Research on Residual-Current Measurement System of Substation Considering Magnetic Shielding Effect.

Residual current is an important monitoring quantity of a power system, and a current sensor plays an important role in detecting current. The substation environment is complex. In addition to the power frequency signal, residual current also has AC and DC components. But it is also affected by the stray magnetic field of the substation. Therefore, the accuracy of the current sensor demands higher requirements. The tunnel magnetoresistive sensor has the advantages of a stable operation, high efficiency, and energy saving, but it is easily affected by the external stray magnetic field during measurements, resulting in a large error. Therefore, this paper proposes a residual-current sensing monitoring system considering the magnetic shielding effect. The root mean square error of the magnetic shielding structure is only 0.572 mA, which can effectively reduce the influence of the external magnetic field and improve the detection accuracy. At the same time, the DC measurement error is less than 1%, the AC measurement error is less than 5%, and the hybrid AC/DC error is less than 8%. It has good response ability and can accurately detect residual current.

Design and Performance Analysis of New Coupling Magnetic Core Structure for Dynamic Wireless Charging System of Electric Vehicle

Aiming at the problems of high cost, low efficiency, low power, and high electromagnetic radiation in the dynamic wireless charging system for electric vehicles (EVs), the cover‐like coupling structure and the return‐like coupling structure are designed, and the unique concave structure has excellent engineering practicability. Using Ansoft software for simulation and analysis, the newly proposed two coupling structures have significantly improved the induced voltage and electromagnetic induction strength at the pickup end compared with other commonly used coupling core structures. According to the advantages of practical applications, the application of its composite core structure for simulation and analysis proves that the cover‐like structure of the magnetic field strength at the pickup end not only enhances the magnetic field strength on the coil but also has a good magnetic field shielding effect. The lateral displacement of the EV is kept within the range of 10 cm, the coupling distance is 0–5 cm, the charging is stable, and the transmission efficiency is high. Finally, a dynamic wireless charging experimental platform for small EVs is constructed, which verifies that the new coupling core structure can significantly improve the transmission power and efficiency of the charging system and significantly reduce the economic cost.

Mathematical Analysis on Spherical Shell of Permeable Material in NID Space

In this paper, we have studied the magnetic shielding effect of a spherical shell analytically in fractional dimensional space (FDS). The Laplacian equation in fractional space predicts the complex phenomena of physics. This is a boundary value problem that has been solved by the separation variable method mathematically by taking low frequency w = 0. Electric potential is obtained in fractional dimensional space for the three regions, namely outside the spherical shell, between the shell and hollow sphere and inside the sphere. Also, the induced dipole moment has been derived. We obtain a general solution that reduces to the classical results by setting fractional parameter α = 3 which takes its value (2 < α ≤ 3).

Effectiveness of a dual solenoid magnetic shield at reducing x-ray-like background in silicon-based x-ray detectors

Effectiveness of a dual solenoid magnetic shield at reducing x-ray-like background in silicon-based x-ray detectors

Hybrid optimal design method for magnetic field coils under magnetic shielding boundary

A novel strategy for designing uniform magnetic field and gradient magnetic field coils considering the boundary effect of magnetic shielding is proposed in this study. This strategy uses intelligent optimization algorithm to skillfully transform the complex coil design problem into the spatial optimization problem of individual population. The mirror method is combined with Green’s function to accurately calculate the magnetic field, and the target field method (TFM) is combined with the whale optimization algorithm to optimize the stream functions using adaptive ridge regression. The minimum fitness function is defined as the real-time magnetic field relative error, and the optimal ridge coefficient is continuously obtained by determining the current density coefficient. The proposed method significantly reduces the magnetic field deviation in the target area compared to the conventional TFM, with reductions ranging from 12.2% to 0.11% (Bx coil), 0.3% to 0.02% (Bz coil), 20% to 10% (dBx/dz coil) and 2.9% to 2.4% (dBz/dz coil). The strategy has been effectively validated by analytical simulations and experimental results, and is expected to be applied to the design of uniform field coils and gradient coils for ultra-high precision atomic sensors.

Sliding mode control of an outer-rotor magnetic-gear-integrated motor with a Halbach array

In this paper, the magnetic-gear-integrated motor with a Halbach array is analyzed. The combination of coaxial magnetic gear and permanent magnet synchronous motor (PMSM) replaces the role of mechanical gear in transmission structure and realizes the transmission characteristics of low-speed and high torque. Halbach permanent magnet array has the effect of good unilateral magnetic shielding, which can make the waveform closer to the sine wave. Aiming at the problem that the position sensor limits the control accuracy during the operation of the motor, founded on the analysis of the mathematical model of the magnetic-gear-integrated motor, an improved sliding mode observer is proposed. Also, the sliding mode controller (SMC) replaces the PI regulation in the speed loop to increase the robustness of the system. Lyapunov is utilized to prove the stability of the system, and the simulation is built in MATLAB/ Simulink. A 3.6 kW prototype is manufactured and tested. The feasibility of the sensorless-driven system is proven by simulation and experiments.

A Dual Integral Equation Approach for Evaluating the Shielding of Thick Circular Disks against a Coaxial Loop

The electromagnetic interaction between a circular disk with finite conductivity and finite thickness and a coaxial circular loop of constant current is addressed here. The finite conductivity and thickness of the material disk lead to the adoption of suitable generalized boundary conditions, and the problem is thereby reduced to the solution of two sets of dual integral equations in the Hankel transform domain. Such equations are then solved by expanding the spectral unknowns in Neumann series of Bessel functions. An alternative formulation that is valid for purely conductive screens with no magnetic properties, which is computationally much faster, is proposed as well. The magnetic shielding effectiveness of the structure is studied in detail, pointing out its dependencies and possible critical situations.

Magnetic shielding up to 0.67 T at 77 K using a stack of high temperature superconducting tape annuli of 26 mm bore

In this work we demonstrate the magnetic shielding ability of a stack of YBa2Cu3O7 tape annuli. The annuli are cut from a 46 mm wide second generation coated conductor deposited on a Ni-5at.%W alloy ferromagnetic (FM) substrate. The inner bore of the stacked tapes is 26 mm and the outer diameter is 45 mm. Three samples with different height (24 mm, 14.9 mm, 9.9 mm) are studied. All the experiments are carried out at both room temperature and liquid nitrogen temperature (77 K). The shielding efficiency is investigated when the magnetic field is applied either parallel to the axis of the stack (axial shielding) or perpendicular to it (transverse shielding). Under an axial field, magnetic shielding is found to be effective (SF ) up to magnetic flux densities of 0.67 T. The presence of the FM substrates is found to have two important consequences. First, the stack of annuli is able to shield transverse flux densities in spite of its layered structure. Second, a finite magnetic shielding effectiveness is demonstrated at room temperature. In order to understand the contribution of the FM substrates to the shielding mechanism, we use the experimental field dependence of the magnetic permeability as determined independently from hysteresis loop measurements on the same substrates. A finite-element homogenized model solved with an H–φ formulation is shown to successfully reproduce the shielding factor of the stack at room temperature and 77 K, both under axial and transverse applied fields. These models are also used to assess the influence of the critical current density and the magnetic permeability on the shielding efficiency. Finally, the results are used to predict the magnetic shielding properties of higher stacks, demonstrating their significant potential to shield axial fields of T (with SF ) at 77 K.

Active radiation measurements over one solar cycle with two DOSTEL instruments in the Columbus laboratory of the International Space Station

Two DOSimetry TELescopes (DOSTELs) have been measuring the radiation environment in the Columbus module of the International Space Station (ISS) since 2009 in the frame of the DOSIS and DOSIS 3D projects. Both instruments have measured the charged particle flux rate and dose rates in a telescope geometry of two planar silicon detectors. The radiation environment in the ISS orbit is mostly composed by galactic cosmic radiation (GCR) and its secondary radiation and protons from the inner radiation belt in the South Atlantic Anomaly (SAA) with sporadic contributions of solar energetic particles at high latitudes. The data presented in this work cover two solar activity minima and corresponding GCR intensity maxima in 2009 and 2020 and the solar activity maximum and corresponding GCR intensity minimum in 2014/2015. Average dose rates measured in the Columbus laboratory in the ISS orbit from GCR and SAA are presented separately. The data is analyzed with respect to the effective magnetic shielding and grouped into different cut-off rigidity intervals. Using only measurements in magnetically unshielded regions at low cut-off rigidity and applying a factor for the geometrical shielding of the Earth, absorbed dose rates and dose equivalent rates in near-Earth interplanetary space are estimated for the years 2009 to 2022.

A Magnetic Compensation System Composed of Biplanar Coils Avoiding Coupling Effect of Magnetic Shielding

Magnetic compensation coils are often used to improve the effectiveness of a magnetically shielded room (MSR), but a distortion of the field is caused by the shielding layer consisting of high-permeability material, which leads to a reduction in compensation capacity. To solve this problem, a new method is presented in this article based on a target-field method, an image method, and particle swarm optimization. By this way, a magnetic compensation system composed of biplanar coils is designed and fabricated to compensate the background field for a wearable magnetoencephalography device inside the MSR, and the coupling effect between the magnetic shielding material and the compensation field is effectively avoided. Experimental data show that these compensation coils produce uniform fields and field gradients with the inhomogeneity of less than 3.8%, consistent with the simulation results. In addition, this system realizes a real-time compensation to the residual field and field gradient in the MSR.

Effect of Magnetic Shielding on the Detection Sensitivity of Position Detection Sensors for Railway Vehicles

Effect of Magnetic Shielding on the Detection Sensitivity of Position Detection Sensors for Railway Vehicles

Behavior of Mold Electromagnetic Stirring for Round Bloom Castings and Its Eccentric Stirring Problem.

In this paper, a mold electromagnetic stirring (M-EMS) model was established to investigate the behavior of M-EMS for round bloom castings under different conditions, and an electromagnetic-flow-heat transfer-solidification coupling model was established to explore the problem of eccentric stirring for various formats of round blooms. The results show that the magnetic flux density decreased with the increase in the current frequency, but the electromagnetic torque increases first and then decreases with it, and the same structure of M-EMS for round blooms has the same optimal current frequency at any current intensity. The electromagnetic torque and electromagnetic force both increase as a quadratic function of the current intensity, and the electromagnetic torque, which drives the steel flow, can directly characterize the real M-EMS performance. The mold copper tube has a significant magnetic shielding effect on M-EMS, the stirring intensity decreases rapidly as the tube thickness increases, and the optimal stirring frequency decreases as well. In fact, the deviation between the stirrer center and the geometric center of the strand can result in the eccentric stirring phenomenon. When blooms with a section size of Φ350 mm are produced by Φ650 mm SMS-Concast casting machine, the upper region of the inner arc side and the lower region of the outer arc side are subject to a stronger washing effect, which makes the temperature of the inner and outer arcs show alternating differences. The jet flow from the five-port nozzle can suppress the difference in initial solidification symmetry between the inner and outer arcs of round blooms caused by eccentric stirring. This paper reveals the magnetic shielding effect of the mold copper tube and the magnetic field loss of the air between the stirrer and the inner and outer arcs of the copper, which lead to the stirring intensity and the eccentric stirring phenomenon.

Effect of Magnetic Shielding on Levitation Characteristics of Superconducting Gravimeter

The superconducting gravimeter is currently the most accurate instrument in relative gravity measurement, so the high-precision calculation and analysis of superconducting magnetic levitation system is crucial to the development work of superconducting gravimeter. Shielding material can weaken the influence of external magnetic field source fluctuation on the internal levitation magnetic field and provide a stable electromagnetic environment for the magnetic levitation system. But at the same time, shielding material will also have an impact on the internal suspended magnetic field itself, which will lead to large deviations in the study of electromagnetic characteristics of the magnetic levitation system. This article establishes and optimizes the simulation calculation model of a superconducting gravimeter magnetic levitation system based on <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> method, and studies the effect of magnetic shielding on the magnetic field, levitation force, and magnetic force gradient of the internal levitation system. After that, the simulation calculation results are compared with the experimental results, and the simulation calculation error of superconducting levitation force and magnetic gradient is less than 1%, which verifies the correctness of the optimized simulation model. This study is an important guide for the accurate calculation of the electromagnetic properties of all superconducting systems containing magnetic shielding materials, such as superconducting gravimeter, superconducting gravity gradiometer, etc.