• 한국초전도ㆍ저온공학회논문지
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• 제18권1호
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• pp.46-49
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• 2016

The wireless power transfer (WPT) system using a magnetic resonance was based on magnetic resonance coupling of the transmission and the receiver coils. In these system, it is important to maintain a high quality-factor (Q-factor) to increase the transmission efficiency of WPT system. Our research team used a superconducting coil to increase the Q-factor of the magnetic resonance coil in WPT system. When the superconductor is applied in these system, we confirmed that transmission efficiency of WPT system was higher than normal conductor coil through a preceding study. The efficiency of the transmission and the receiver coil is affected by the magnetic shielding effect of materials around the coils. The magnetic shielding effect is dependent on the type, thickness, frequency, distance, shape of materials. Therefore, it is necessary to study the WPT system on the basis of these conditions. In this paper, the magnetic shield properties of the cooling system were analyzed using the High-Frequency Structure Simulation (HFSS, Ansys) program. We have used the shielding materials such as plastic, aluminum and iron, etc. As a result, when we applied the fiber reinforced polymer (FRP), the transmission efficiency of WPT was not affected because electromagnetic waves went through the FRP. On the other hand, in case of a iron and aluminum, transmission efficiency was decreased because of their electromagnetic shielding effect. Based on these results, the research to improve the transmission efficiency and reliability of WPT system is continuously necessary.

• 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.

• KEPCO Journal on Electric Power and Energy
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• 제1권1호
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• pp.15-20
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• 2015

To examine the magnetic shielding effect for carbon-based materials at extremely low frequencies (60 Hz), two types of carbon black (Super-P and Denka Black) and a natural graphite (HC-198) were mixed into organic binder at 10 wt.% to produce a coating solution, and a powder coating with varying thickness was applied on an aluminum disk measuring 88 mm in radius. A device was developed to measure the sheielding effect at extremely low frequencies. A closed circuit was achieved by connecting a transformer and a resistor. The applied voltage was fixed at 65 V, and the magnetic field was measured to being the range of 4.95~5.10 mG. Depending on the thickness of the coating layer, the magnetic field showed a decreasing trend. The maximum decrease in the magnetic field of 38.3% was measured when natural graphite was coated with specimens averaging $455{\mu}m$. This study confirmed that carbon-based materials enable magnetic shielding at extremely low frequencies, and that the magnetic shielding effect can be enhanced by varying the coating thickness.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2001년도 High Temperature Superconductivity Vol.XI
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• pp.71-71
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• 2001

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 B
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• pp.978-979
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• 2006

Recently, Peoples are exposed the ELF(Extremely Low Frequency) magnetic fields in the vicinity of underground transmission lines, and there are the generally accepted opinion that the magnetic fields affect the human body and there are possibility of the disease. Also in relation to this problem, technical solution methods and research are advanced for reducing the magnetic fields. In this paper, to practically understand the magnetic fields underground transmission lines, We analyze the electromagnetic field distribution in the underground transmission lines by means of FEM(Finite Element Methods) and present that improvement of the effective shielding methods by applying cable arrangements and shielding materials, eddy current problem to the underground transmission lines by means of the numerical analysis Tool.

• Journal of Welding and Joining
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• 제20권1호
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• pp.76-82
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• 2002

In these days, many advanced nations have enforced import restrictions against things emitting electromagnetic wave which has report that it is so harmful. In general, electromagnetic wave is composed of electric wave and magnetic wave. The reflection of electromagnetic wave is mainly reflected by conductive materials and the magnetism loss is generated by magnetic ferrite. The magnetism loss of ferrite is separated by eddy current loss, residual magnetism loss and hysteresis loss. Thermal sprayed coating is intended to manufacture because of simple processes and high efficient electromagnetic wave shielding. The high efficient thermal sprayed coatings were made from the magnetic ferrite materials that characterizes absorption of electromagnetic wave, and the electric conductive materials that characterize emitting of electromagnetic wave. This study was manufactured thermal sprayed coatings to improve absorption-efficiency, and measured the electromagnetic wave shielding efficiency. As the experimental results, high electromagnetic wave shield efficiency was obtained at wave frequency 2GHz to thermal sprayed ferrite coatings manufactured by size distribution range of spray powders, $38~88\mu\textrm{m}$.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 C
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• pp.1960-1962
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• 2004

In this paper, we have studied shielding characteristics of high conductivity or high permeability materials on ELF magnetic fields generated from single or three phase AC line. Perm alloy has been selected as high permeability material and copper as high conductivity material. Four-plate shield (square section) was considered as a shielding shape. We found copper showed stable shielding effects more than perm alloy.

• 전기학회논문지
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• 제59권7호
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• pp.1265-1271
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• 2010

Power cable of an AC arc welder can surround a body of worker at the moment of welding. Applying the boundary element method, we calculated current densities induced in organs inside a worker to study the magnetic field reduction characteristics of shielding wear materials. We knew shielding wear with high permeability materials lowers current density more than high conductivity materials. We also found current density was lowest when high permeability materials were inside high conductivity materials in double layer shielding wear.

• 전기학회논문지
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• 제64권4호
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• pp.623-628
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• 2015

In this paper, the shield plate was applied to the wireless power transfer (WPT) system. Then we compared transmission efficiency of WPT system between transmitter and receiver coils. The superconductor coil was applied to transmitter and receiver coils in order to increase the transmission efficiency of WPT. The superconductor coil was more effective to power transmission as its current density was higher than normal conductor coil. Efficiency of WPT between transmitter and receiver coils was changed by a quality of shielding. We used the shielding materials such as glass, iron, steels, aluminum etc. The efficiency of WPT system was depended on the shielding materials of transmitter and receiver coils. As a result, magnetic material such as aluminum, iron reduced the magnetic flux density and the efficiency of WPT. remarkably, but in non-magnetic material such as glass and plastic, the efficiency of WPT was unaffected.

• 전기학회논문지
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• 제63권6호
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• pp.770-775
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• 2014

According to ICNIRP guidelines for limiting exposure to time-varying electric, magnetic and electromagnetic fields up to 300GHz, magnetic flux density which range from 3Hz to 150kHz are regulated to lower than $6.25{\mu}T$. In order to comply with its standard, OLEV(On-Line Electric Vehicle) have been designed considering EMF(Electro-Magnetic Field) reduction. However, if a current flowing in power line would be bigger for increasing power transfer efficiency, the established shield system no longer acts their role properly. In this paper, therefore, FCCL(Flexible Copper Clad Laminate) is applied to power line and pick-up devices to solve the problems. Though, the FCCL is normally utilized to insulator on circuit board, because of its high heat resistance characteristic, flexibility and thin properties, it makes effectiveness in the shielding device as well. 4 types of FCCL shielding structure are introduced to power line and pick-up devices. From the results, the FCCL which are placed in proposed positions shows maximum EMF reduction compared to the established shielding structure. Henceforth, if OLEV is applied FCCL shielding structure in practice, it will not only be more safe but also step forward to commercialization near future.