• Title/Summary/Keyword: magnetic shielding

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Performance Evaluation of Low Frequency Magnetic Field Shielding by Eddy-Current (와전류에 의한 저주파 자기장 차폐 성능 평가)

  • Choi, Hak-Yun
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.24 no.9
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    • pp.124-128
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    • 2010
  • In this paper, the shielding effectiveness of aluminum shielded room with using eddy-current is calculated and measured after fabricated. The size and thickness of shielded room are decided as $2.4{\times}2.4{\times}2.4[m^3]$ and 12[mm] after AC shielding characteristics by eddy-current of conductive materials is analyzed. To verify the shielding effectiveness, a rectangular helmholtz coil is fabricated to generate magnetic field of 1.37[${\mu}T$] and measured magnetic field inside shielding room for 0.01~10[Hz]. According to calculations and measurements, AC Shielding effectiveness by eddy-current in aluminum is very small for 0.01~2[Hz] and 5 times to 11 times for 5~10[Hz].

Magnetic Shielding Effectiveness Measurement of Magnetic Steel Sheets in ELF Range

  • Yeon, Kyo-Heum;Son, Derac;Park, Eon-Byeong;Lee, Jae-Young;Do, Kyung-Hwan;Park, Jae-Seg
    • Journal of Magnetics
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    • v.13 no.4
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    • pp.173-176
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    • 2008
  • In this study, a new kind of instrument for measuring the magnetic shielding effectiveness (MSE) was developed using a double yoke; one a magnetizing yoke and the other a sensing yoke. Using the developed instrument, the MSE could be measured for a steel sheet specimen in the ELF range, where the magnetic permeability contributes to the MSE at low frequencies and eddy currents contributes to the MSE high frequencies with < 0.1 dB reproducibility. The developed measuring method can be applied to quality control in a steel sheet company producing EMI/EMC shielding materials.

Magnetic-Shielding Effectiveness Analysis of the Trigger Assembly of Small Arms (소구경 개인화기 격발신호 발생장치의 자기차폐효과 분석)

  • Lee, Kisu;Ahn, Joon Mo;Chae, Je-Wook
    • Journal of the Korea Institute of Military Science and Technology
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    • v.21 no.4
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    • pp.456-463
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    • 2018
  • With the development of weapon systems by mounting various sensors, it makes important to analyze the precise functioning of sensor to external environment. In the case of small arms with magnetic sensor, the malfunction of small arms might be caused by strong external magnetic fields. In this study, the effects of magnetic sensor on external magnetic fields were analyzed, and optimal magnetic shield and shield structure were designed through M&S. In addition, the magnetic-shielding effectiveness of magnetic sensor in small arms was verified with commercial shielding materials. As a result, it was demonstrated that the Fe-Cu-Si-Nd-B with the structure of multi-layer metallic shields was shown the magnetic-shielding effectiveness of 83 % for an external permanent magnet and 19 % for an alternating magnetic field of 180 dBpT at 60 Hz, respectively.

Magnetic Shielding Effect on Halbach Cylinder used in Magnetic Refrigerators

  • Baek, Un Bong;Lee, Jong Suk;Yu, Seong-Cho;Ryu, Kwon-Sang
    • Journal of Magnetics
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    • v.19 no.4
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    • pp.349-352
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    • 2014
  • The system for producing magnetic field constitutes an important component of magnetic refrigerator. Many researchers have directed significant effort to increase the magnetic field intensity, because the magnetocaloric effect at the Curie temperature increases with the power of 2/3 of the magnetic field. In this study, we report the simulation of the magnetic field intensity at polar axis of a Halbach cylinder (HC) by i) changing the length and thickness of the HC, ii) having with or without gap of the HC, and iii) surrounding the HC with a soft magnet shell, acting as a shielding. We simulated the field distribution of a HC with a finite size. Furthermore, the detailed numerical results of the magnetic field distribution and its dependence on shielding are presented in this study.

Analysis for Shielding Effectiveness of Metal Shielding Layer within Near-Field of Noise Source (노이즈 소스 근거리장에 위치한 금속 차폐막의 차폐효과 분석)

  • Lee, Won-Seon;Lee, Won-Hui;Hur, Jung
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.19 no.3
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    • pp.59-65
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    • 2019
  • The EMI shielding effectiveness of the shielding layer thickness was analyzed when the metal shielding layer was placed in the near field of the magnetic probe and the noise source. Microstrip lines were used as noise source, and graphite and ferrite were selected as metal shielding materials. The magnetic probe uses the electromagnetic radiation measurement method using the magnetic probe by applying the IEC 61967-6 method. The transmission coefficient between the microstrip line and the magnetic probe was analyzed. The distance between the two was 1 mm for a single shielding layer and 5 mm for a multiple shielding layer. The thickness of the shielding layer was changed to 5 um, 10 um, 30 um, and 50 um. When the frequency was changed from 150 kHz to 1 GHz, a maximum shielding effectiveness (SE) of 44.9 dB was obtained.

Development of an Active Magnetic Noise Shielding System for a Permanent Magnet Based MRI (영구자석 MRI를 위한 능동형 자기 잡음 차폐시스템 기술 개발)

  • 이수열;전인곤;이항노;이정한
    • Journal of the Institute of Electronics Engineers of Korea SC
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    • v.40 no.3
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    • pp.181-188
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    • 2003
  • In this paper, we introduce a magnetic noise shielding method to reduce the noise effects in permanent magnet based MRI systems. Through FEM electromagnetic analyses, we have shown that the magnetic noise component parallel to the main magnetic field is the major component that makes various artifacts in the images obtained with a permanent magnet based MRI. Based on the FEM analyses, we have developed an active magnetic noise shielding system composed of a magnetic field sensor, compensation coils, and a coil driving system. The shielding system has shown a noise rejection ratio of about 30dB at the frequency below several Hz. We have experimentally verified that the shielding system greatly improves the image quality in a 0.3 Tesla MRI system.

Analysis of Radiation Shielding Effect of Soft Magnetic Material applied to Military Facility (경량 연자성 소재의 군 시설물 적용 시 방사선 차폐효과 분석)

  • Lee, Sangkyu;Lee, Sangmin;Choi, Gyoungjun;Lee, Byounghwak
    • Journal of the Korean Society of Radiology
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    • v.15 no.2
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    • pp.191-199
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    • 2021
  • The purpose of this research is to analyze the radiation shielding effect of soft magnetic material to confirm the applicability to the military facilities. The soft magnetic material is known to be effective in shielding EMP. If this material is also effective in radiation shielding, it is expected that it has a lot of applicability in military protection. In particular, this material contains boron, so it will be effective in shielding neutrons. In this research, experiments were conducted using Cs-137 and Co-60 sources to check the gamma ray shielding effect. In addition, the Monte Carlo N-Particle(MCNP) modeling was applied to evaluate the gamma ray and neutron shielding effect of a military command tent. As a result, as the soft magnetic thickness increased, the shielding performance improved according the linear attenuation law of gamma ray and neutron. Therefore, this research verified that the application of soft magnetic material for military purposes in radiation shielding would be effective.

A Study on the Electromagnetic Pulse Shielding Effect of Concrete Wall Sprayed with Cu-based Metal (Cu계 금속을 용사한 콘크리트 벽체의 전자파 차폐 성능에 관한 연구)

  • Jang, Jong-Min;Lee, Han-Seung
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2020.11a
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    • pp.18-19
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    • 2020
  • The ElectroMagnetic Pulse (EMP) destroys social infrastructure at once and causes social chaos. However, currently major infrastructures are constructed of concrete that does not have electromagnetic shielding performance. In this study, using the arc metal spraying method is used to evaluate the shielding performance and construction performance of concrete. The electro-magnetic shielding effect is measured by fabricating a shielding room with reference to MIL-STD-188-125, and the construction performance is evaluated by measuring the adhesion strength of thin metal sprayed film-concrete. As a result of the study, when the metal spraying method is applied, the shielding effect is higher than that of the special electro-magnetic shielding concrete, and it is considered to be more economical than the existing metal plate (3~5 mm).

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Design of Magnetic Field Compensation System Model for AC Magnetic Field Shielding (교류자기장 차폐를 위한 자기장 상쇄장치 모델의 설계)

  • Choi, Hak-Yun
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.25 no.7
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    • pp.78-82
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    • 2011
  • In this paper, magnetic field compensation system with an open architecture and can be installed indoors is designed and measured by fabricated. To verify the shielding effectiveness, two rectangular helmholtz coils with 3-axis are fabricated to generate magnetic field and measured magnetic field inside compensation coil for 1~60[Hz], According to measurements, AC shielding effectiveness of compensation system is 96[%] of 1[Hz], 95[%] of 30[Hz] and 90[%] of 60[Hz]. The performance of system therefore can be used as the magnetically shielded room for medical and industrial field.

Characteristics simulation of wireless power transfer system considering shielding distance

  • Lee, Yu-Kyeong;Choi, Hyo-Sang;Jung, Byung Ik;Jeong, In-Sung
    • Progress in Superconductivity and Cryogenics
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    • v.17 no.1
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    • pp.40-43
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    • 2015
  • Wireless power transfer technology is using the magnetic resonance recently drawing increased attention. It uses the resonance between transmitter and receiver coils to transfer power. Thus, it can improve the transfer distance and efficiency compared with the existing magnetic induction technique. The authors found from the previous study that the application of the superconductor coil to the magnetic resonance wireless power transfer system improved its efficiency. Its application to real life, however, requires the additional study on the effects of adjacent materials. In this study, the two resonance coils made by superconductor coils were used to aluminum and plastic shielding materials was placed between the coils. S-parameters were analyzed according to the position of the shielding material between the transmitter and receiver coils. As a result, the plastic of shielding material had no effect, but the aluminum of shielding material affected the wireless power transfer due to the shielding effectiveness.