Magnetic Field Shielding Effectiveness Research Articles

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.

Study on Magnetic Field Shielding Effectiveness of Slotted Conductor Plate

In this paper, the magnetic field shielding effectiveness of slotted conductor plate is tested. According to the dominant effect of magnetic shielding at different measuring points, the slotted conductor plate is divided into edge effect area, platform area and aperture leakage area, and the change law of magnetic field shielding effectiveness in different regions is analyzed. The magnetic field shielding effectiveness of slotted conductor plates at different frequencies is tested. The results show that the shielding effectiveness increases with the increase of frequency.

Low-frequency magnetic field shielding effect of artificial joint-free REBCO coils

The screening current induced in superconductors can passively shield external magnetic fields and hence provide a noise free environment for precision sensors and instruments. This paper presents a novel design employing artificial joint-free REBCO (REBa2Cu3O7-x, RE: rare earths) coils which can economically extend the field shielding space for larger instruments, e.g. clinical equipment. We compared the shielding factors of single, double and multi-coils, and confirmed a coil with Helmholtz construction as the optimal architecture. Due to the zero resistance of the joint-free REBCO coils, the shielding effectiveness reaches 80 dB at the center of coils, shielding 99.99% of the external magnetic field of 10 μT at 1 × 10−5 Hz, and 40 dB (99%) in a greater spherical space of 40 mm in diameter. Additionally, the shielding effectiveness does not decrease in the external magnetic field of 1 nT. Such a low frequency magnetic shielding effect implies promising applications for the present work, such as preventing interference magnetic fields from precision instruments, which generally require field sensitivity as low as the fT · Hz−1/2 range.

Effect of Vertical Metal Plate on Transfer Efficiency of the Wireless Power Transfer System

Power transfer efficiency is an important issue in wireless power transfer (WPT). In actual applications, the WPT system may be exposed to a complex electromagnetic environment. The metal which is inevitably or accidentally close to the system will impact the power transfer efficiency. Most previous research has aimed at the effect of the metallic sheet paralleled to the resonant coil. This paper focuses on the effect of the metallic plate perpendicular to the resonant coils. Firstly, based on the theoretical analysis, a simulation model is setup using COMSOL Multiphysics. The efficiencies of the double-coils magnetic resonant WPT system with the presence of the parallel and vertical aluminum plate are studied comparatively. Efficiency improvement is observed with the vertical plate while the reduction appeared with the presence of the parallel plate. The vertical metallic plate has shown a magnetic field shielding effect according to the magnetic field distribution. It can reduce the radial magnetic field and enhance the axial magnetic field. Then, the effects of the position and size of the vertical plate are studied. It is found that the transfer efficiency has a preferable improvement when the vertical aluminum plate with a larger size is placed between the resonant coils and near outer edge of the windings. Finally, the experiment is carried out to verify the effect of the vertical aluminum plate on the WPT system.

Magnetic field shielding effect for CFETR TF coil-case

The operation of superconducting magnet for fusion device is under the complex magnetic field condition, which affect the stabilization of superconductor. The coil-case of TF coil can shield the magnetic field to some extent. The shielding effect is related to the eddy current of coil-case. The shielding effect with different eddy current is studied by decomposing the exciting magnetic field as two orthogonal components, respectively. The results indicate that the shielding effect of CFETR TF coil-case has obvious different with the different directional magnetic field, and it’s larger for tangential magnetic compared with that for normal field.

Design and Analysis of Halbach Permanent Magnet Synchronous Motors Based on FEM Models

This paper studies the application of Halbach array in optimal design of Permanent Magnet Synchronous Motors (PMSM). First, the paper demonstrates the intrinsic sinusoidal magnetic field and one-side magnetic shielding effect produced by Halbach array in FEM. Afterward, a serious of Halbach motor models based on different segment numbers per pole are established combined with Ansoft. Next, the waveform and harmonic contents of air-gap flux density are analysed. Then, the relationship between the segment numbers per pole and cogging torque are explored. Finally, the power-angle curves for coreless/core rotors are contrasted. The above results explain why and how Halbach array can be applied in PMSM design to reduce harmonic components for air-gap flux density, increase power density and decrease moment of inertia.

Investigation of Models of Grid-Like Shields Subjected to Lightning Electromagnetic Field: Experiments in the Frequency Domain

In this paper, frequency-domain measurements of magnetic and electric field shielding effectiveness of grid-like spatial shield models exposed to lightning action are presented. Scaled experimental models of nearby and direct lightning strikes are proposed. Models of single-layer and double-layer wire shields of two different mesh widths are examined. Differences between the shielding effectiveness of magnetic and electric fields are discussed. The measurement results are compared to the results of numerical simulations.

Magnetic Shielding Effectiveness of Iron-Based Amorphous Alloys and Nanocrystalline Composites

This paper refers to magnetic field shielding effectiveness <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$S_{\rm H}$</tex></formula> of the selected iron-based amorphous alloys and some magnetic composites. The measurement conditions were chosen regarding the potential sources such as energetic lines or electric devices. As it was shown, the shields made of amorphous and optimized (in amorphous phase) melt spun ribbons can be applied as highly efficient and flexible shields. In the group of the tested alloys, the highest <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$S_{\rm H}$</tex></formula> reveal (at <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$H=110$</tex></formula> A/m and <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$f=55$</tex></formula> Hz): Fe <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{84}$</tex></formula> Cr <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{2}$</tex></formula> <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">${\rm B}_{14}$</tex></formula> (95%) and optimized Fe <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{72}$</tex></formula> Co <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{10}$</tex></formula> Nb <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{6}$</tex></formula> B <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{14}$</tex></formula> (97%) and Fe <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{80}$</tex></formula> Nb <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{6}$</tex></formula> B <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{14}$</tex></formula> (92%). In the case of the tested composites, a significant decrease of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$S_{\rm H}$</tex></formula> was observed. The shielding effectiveness decreases with decreasing size of magnetic addition due to breaking magnetic flux circuit and dipolar interactions between particles. For the composite with magnetic flakes of 4 mm in diameter <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$S_{\rm H}$</tex></formula> is about 60%; therefore, it can be applied as coatings in order to fulfill human protective standards. For the composites with micro and nano-sized magnetic powder <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$S_{\rm H}$</tex></formula> does not depend of the composition which suggests that a response to a magnetic field is fully influenced by the demagnetization effect.

Morphology-dependent field emission characteristics of SiC nanowires

Felted, curly, and straight β-SiC nanowires (SiCNWs) had been synthesized by chemical vapor reaction, and morphology-dependent field emission (FE) characteristics were chiefly investigated. The turn-on and threshold fields were 2.0 and 5.3 V/μm for felted nanowires, 1.5 and 3.25 V/μm for curly nanowires, and 1.0 and 2.05 V/μm for straight nanowires, respectively, suggesting that morphology played an important role in FE properties of the SiCNWs. Magnetic field shielding effect is proposed to explain the morphology-dependent FE characteristics, and it may stand as a nice referential work for researching FE properties of other wirelike materials.

3-D modeling of thin conductive sheets for magnetic field shielding: calculations and measurements

Summary form only as given. This paper presents a new technique for calculating the magnetic field shielding effectiveness of thin conductive sheets of materials. The sheets are modeled as meshes of passive shielding wire filaments. Using this technique, complex three dimensional sources and shield configurations can be easily modeled. A computer program was developed to perform the calculations, and a comprehensive set of experiments was performed to verify the technique. Calculations and measurements are compared in the paper. The calculation method provides a numerical and experimentally verified technique for evaluating the shielding effectiveness of thin conductive sheets for power system magnetic field shielding applications. A predictive method such as this is becoming increasingly important as conductive materials are increasingly becoming accepted as effective shielding materials.

High- Tc superconductor-polymer composites: YB 2Cu 3O 7− x-polyester polymer and YBa 2Cu 3O 7− x-Teflon

The YBa 2Cu 3O 7− x (YBCO) superconductor powder-polyester polymer (Polimal 109) and YBCO-Teflon composites were investigated. The volume fraction of YBCO powder ranged from 0.05 to 0.8. D.c. electrical conductivity of the composites increased exponentially with increase of YBCO volume content. The I–V characteristics showed transition from ohmic to highly nonohmic behaviour at electric field intensities of about 100 V/cm. Although these composites do not show zero resistance below the superconducting transition temperature T c of YBCO, the intrinsic diamagnetic properties of superconductor are observed. The magnetic field shielding effect indicates the superconducting transition at 90 K. The investigated composites have, at liquid nitrogen temperature, levitation properties similar to those of ceramic superconductors. The levitation force is proportional to the YBCO volume content.

Shielding effectiveness of a metal sheet parallel to the axis of a circular loop

The equation of the magnetic shielding effectiveness for a configuration made of a circular (transmitting) coil in a semi-half space on one side of a metal sheet and a magnetic sensor in the space on the other side of the sheet has been derived by Moser for the case where the axis of the coil is perpendicular to the sheet. One of the objectives of the present paper is to derive an equation for the magnetic shielding effectiveness in the case where the coil axis is parallel to the sheet. This paper shows that this effectiveness is smaller by a certain amount than the case where a magnetic dipole is placed at the center of the transmitting coil instead of the coil. The amount of reduction is a function of the ratio of the coil radius to the distance from the center of the coil to the observation point. Another objective of this paper is to determine what kind of quantities can be obtained by the measurement method by the MIL-STD-285 which is used for the measurement of the shielding effectiveness of the wall of the shielded room. In this measurement, the magnetic field shielding effectiveness is derived by measurement of the induced voltage of the receiving coil when the transmitting and receiving coils with a diameter of 12 inches are placed on both sides of the sheet at a distance of 12 inches, respectively, from the sheet in a plane perpendicular to the sheet. It is shown that the result of such a measurement gives rise to a value almost equal to (or smaller by about 0.4 dB than) the magnetic shielding effectiveness in a hypothetical case where a magnetic dipole is placed at the center of the transmitting coil and a magnetic sensor is placed at the center of the receiving coil.

Some Electromagnetic Compatibility Grounding and Shielding Considerations in Titanium Aircraft Structures

High resistivity of titanium alloys (in the vicinity of 200 microohm-cm) requires special consideration of the role of airplane structure as a current return and as an electromagnetic shield. Experimental data and supporting analysis are presented. Voltage drops due to structure currents are larger in titanium than in aluminum airplanes. Return currents in structure are distributed widely instead of being relatively concentrated. For representative skin thicknesses, magnetic field shielding effectiveness is rather insignificant even at frequencies in the ADF range. Achieving electromagnetic compatibility in titanium airplanes will require greater than previous use of wire rather than of structure returns for susceptible circuits. To obtain a given magnetic field, isolation between a source and a receptor will require greater reliance on physical separation than on intrinsic magnetic field shielding of the structural material.