• Journal of Magnetics
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• 제19권4호
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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.

• 조명전기설비학회논문지
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• 제25권7호
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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.

• 조명전기설비학회논문지
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• 제24권9호
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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].

• 조명전기설비학회논문지
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• 제25권6호
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• pp.57-67
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• 2011

Purpose of this study is to find the mitigation method of magnetic field by finite length multi-conductors such as indoor distribution lines and to be applicable to design of the distribution lines. For this purpose, exact formula about the components $B_x$, $B_y$, $B_z$ of magnetic field need in case of straight line-conductor with finite length forward any direction. In this study simple formula of the components were deduced and by using these formula magnetic fields for various models of line-configurations were calculated. And also a calculation method of induced currents in conductive shield was presented and using this method, programing of calculation is relatively easy and calculation time is short. The magnetic field after cancellation by these induced currents was calculated. All of calculations were performed by Matlab 7.0 programs. Through the calculation results it could be obtained followings for the mitigation of magnetic fields. The separation between conductors ought to be smaller than smaller as possible. In case of 3-phase, delta configuration is more effective than flat configuration. In case of 3-phase, unbalanced currents ought to be reduced as possible.. In case of more than two circuits of 3-phase, adequate locations of each phase-conductor such as rotating configuration of 3-phase conductors are more effective. The magnetic shielding effect of the conductive shielding sheet is very high.

• 조명전기설비학회논문지
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• 제24권6호
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• pp.154-159
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• 2010

본 논문에서는 0.1[Hz]에서 60[Hz]의 저주파 자기장을 차폐할 수 있는 경량의 자기차폐실을 설계하고, 차폐실을 제작하여 차폐율을 측정하였다. 자기차폐실의 크기는 산업용 측정기기가 들어갈 수 있는 3.0[m](W)$\times$ 3.0[m](L)$\times$3.0[m](H)로 하였으며, 투자율이 높은 자성체의 직류차폐와 교류차폐특성, 도전성물질의 와전류에 의한 차폐율을 계산하였고, 설계된 결과로부터 차폐실의 구조 값을 구하였다. 설계된 차폐실의 타당성을 검토하기 위하여 저주파 차폐실을 제작하고 차폐율을 측정하여 계산값과 비교하였다. 측정결과는 0.1[Hz]에서 5배 이상의 차폐율을 만족하였고, 60[Hz]에서는 86배였다. 따라서 본 논문에서 제작한 자기차폐실은 저주파 자기차폐실로 사용할 수 있을 것으로 생각된다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.609-612
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• 2001

To investigate the magnetic field distribution of power line, we used amorphous wire sensor. And we discuss extremely low frequency magnetic field distribution dependent upon arrangement of power line and shielding pipe made from iron or alumimum materials by both measurement and FEM(Finite Element Method) analysis. Appling current of single phase 60 [Hz] 15 [A] is supplied to copper wire coated enamel resign. As the results, we confirmed that linear characteristics of amorphous wire sensor is very excellent and measurement value agrees with FEM calculation. Magnetic field distribution due to shielding materials is changed by permeability and conductivity.

• Journal of Magnetics
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• 제18권1호
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• pp.9-13
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• 2013

Shielding effects in conductive and magnetic materials were investigated as a function of properties, thickness and diameter. In this work, evaluations on passive conductive and magnetic shield specimens were achieved through experimentation set-up using 50 Hz single and three phase induction field sources. Analysis on material microstructure properties and characteristics of shielding specimens were performed with the use of vibrating sample magnetometer (VSM) and field emission scanning electron microscopy (FESEM). An induction field at $136{\mu}T$ of single phase system and $50{\mu}T$ of three phase systems were observed to the shield specimens with the thickness ranged of 0.2 mm to 0.4 mm. It is observed that shield specimen efficiency becomes inversely proportionate to the increment of induction fields. The decrease was attributed to the surface structure texture which relates to the crystallization and non-crystallization geometrical effects.

• 전자공학회논문지SC
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• 제40권3호
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• pp.181-188
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• 2003

본 논문에서는 영구자석 자기공명영상시스템에 나쁜 영향을 기치는 외부 자기 잡음을 효율적으로 차폐하는 기술을 서술하였다. 유한요소법 전자계 해석을 통하여 영구자석의 주자계 방향과 일치하는 자기 잡음 성분이 자기공명영상에 주로 영향을 미치는 것을 밝혔고, 이의 해석 결과를 기반으로 자기잡음센서, 보상코일, 그리고 코일구동기로 구성되는 능동형 자기 잡음 차폐시스템을 개발하였다. 개발된 자기 잡음 차폐시스템은 수 Hz 미만의 저주파 대역의 자기 잡음에 대하여 30dB 이상의 차폐율을 보였으며, 0.3Tesla 전신형 자기 공명영상시스템에 자기 잡음 차폐시스템을 적용하여 자기 잡음에 의한 영상 잡음이 크게 개선됨을 실험적으로 밝혔다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 B
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• pp.932-934
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• 2002

In this paper, we proposed a method to shield perpendicular magnetic fields in high Tc superconductor(HTS) tape of a shell-type HTS transformer with double pancake windings. A diamagnetism of characteristics of superconductor is used to shield magnetic field. For a shielding experiment, a proper shielding model is chosen, and several kinds of HTS are used such as a monofilament HTS tape, two kinds of multifilament HTS tapes and YBCO film disk. The effect of shielding for the perpendicular magnetic field is measured with HTSs for shielding and their utility for shielding is proved.

• 한국전자파학회논문지
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• 제28권1호
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• pp.61-68
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• 2017

본 논문에서는 저주파 대역에서 동작하는 무선전력전송 시스템에서 발생하는 자기장을 저감하기 위한 개선된 자기장 저감 구조를 제안하였다. 제안된 구조는 자성체와 도체로 구성되었으며, 적용된 다양한 설계 파라미터를 최적화하여 전력전송을 위한 자기장의 상쇄효과는 최소화 하면서 시스템 주변으로 누설되는 자기장 상쇄효과는 개선되도록 하였다. 무선전력전송 시스템의 효율과 주변으로 누설되는 자기장 저감 효과를 컴퓨터 시뮬레이션과 측정을 통하여 분석 및 검증을 하였다. 시뮬레이션 분석 결과, 제안된 구조가 적용된 무선전력전송 시스템의 전력전송효율은 약 77 % 수준으로 기존의 전력전송효율과 동등한 수준을 유지하였다. 또한, 고효율을 유지하는 구조들과 비교하여 최대 근접지점에서 누설되는 자기장의 세기를 약 29~37 % 저감할 수 있었다.