• 한국자기학회지
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• 제5권2호
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• pp.109-111
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• 1995

단결정 Cu/ Ni/ Cu 박막의 자기탄성계수(magnetoelastic coupling coefficients)를 자성박막의 두께에 따른 효과이방성에너지(effective anisotropy energy)를 측정하여 현 상학적인 이론 모델로 구하는 방법을 제안하였다. 이러한 간접적인 방법으로 자기탄성 계수를 결정하는 방법은 다른 결정정계에서도 가능하다.

• Journal of Electrical Engineering and Technology
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• 제12권4호
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• pp.1556-1565
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• 2017

This paper depicts the design, implementation and analysis of efficient resonant based wireless power transfer (WPT) technique using three magnetic coupled coils. This work is suitable for mid ranged device due to small form factor while minimizing the loading effect. A multi turned loop size resonator is exploited for both the transmitter and receiver for longer distance. In this paper, class-E power amplifier (class-E PA) is introduced with an optimum power tracking mechanism of WPT system to enhance the power capability at mid-range with a flat gain. A robust method of finding optimum distance is derived with an experimental analysis of the designed system. In this method, the load sensitive issue of WPT is resolved by tuning coupling coefficient at considerable distances. Our designed PA with a drain efficiency of 77.8% for a maximum output of 5W is used with adopted tuning technique that improves the overall WPT system performance by 3 dB at various operating points.

• KEPCO Journal on Electric Power and Energy
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• 제1권1호
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• pp.85-91
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• 2015

전력선 통신에서 사용되는 비접촉식 커플러의 신호 전달 특성을 향상시키기 위한 비접촉식 커플러의 구조와 자기장 결합에 대한 연구를 수행하였다. 비접촉식 커플러의 결합 구조를 분석하였고, Rogowski 코일을 이용한 커플러와 자성체 코어를 이용한 커플러를 제작하여 구조에 따른 신호 전달 특성을 분석하였다. 집중 정수 소자와 임피던스 트랜스포머를 이용한 임피던스 매칭법을 제안하여 협대역과 광대역에서 신호 전달 특성을 향상시켰고 전달 신호의 크기는 대역폭과 트레이드오프가 있음을 보였다. 본 연구는 추후 부하 변동에 따른 임피던스 매칭 연구에 도움을 줄 수 있다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.1169-1177
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• 2008

The system of the railway signaling using the track transmits the approved speed to the location of a train and it. Referring to the way of transmitting train control information, there are the one transmitting it to the on-board system of a train using the direct track, the another transmitting it establishing an instrument, and the other transmitting an instrument by a railway track. The one is the method using the direct track as a conductor for composing the part of the track and attaining the information controlling a train by transmitting a signal to the track. It is used for the high-speed railway and the subway. The method using the track attains information by transmitting it to returned information, and the on-board system of a train attains it by magnetic coupling. Because many reinforcing bars on the concrete slab track are used, interaction between a rail and a reinforcing bar that is not produced on ballast track is made. Due to the interaction, the electric characteristic of rail is changed. In the current paper, we numerically computed the coupling coefficient between the rail and the reinforcing bar based on the concrete slab track throughout the model related to the rail and the reinforcing bar using the concrete slab track that is used in the second interval of the Gyeongbu high-speed railway, and we defined the coupling coefficient not changed in the electric characteristic of rail in the condition that there is no interaction between the rail and the reinforcing bar.

• Journal of electromagnetic engineering and science
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• 제16권4호
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• pp.219-224
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• 2016

In this paper, coupled-mode theory (CMT) is used to obtain a transient solution analytically for a wireless power transfer system (WPTS) when unit energy is applied to one of two resonators. The solutions are compared with those obtained using equivalent circuit-based analysis. The time-domain CMT is accurate only when resonant coils are weakly coupled and have large quality factors, and the reason for this inaccuracy is outlined. Even though the time-domain CMT solution does not describe the WPTS behavior precisely, it is accurate enough to allow for an understanding of the mechanism of energy exchange between two resonators qualitatively. Based on the time-domain CMT solution, the critical coupling coefficient is derived and a criterion is suggested for distinguishing inductive coupling and magnetic resonance coupling of the WPTS.

• 한국자기학회지
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• 제5권2호
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• pp.112-114
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• 1995

매우 얇은 박막에서 자기탄성계수는 효과이방성에너지와 마찬가지로 박막두께에 반비례하여, B/sup eff/ = B/sup b/ + B/sup s/ /t 으로 수학적, 물리적으로 예측됨을 보였다. 이러한 박막두께가 얇아질수록 표면자기탄성계수(surface magnetoelastic coupling coefficient)에 의한 영향이 커지므로 많은 공학적 의미를 내포하고 있다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 B
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• pp.803-805
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• 2004

This paper proposes the calculation method of magnetic coupling coefficient of the contact-less energy transmission system by 3D finite element method with a variation of the secondary core positions. The primary, secondary self and leakage inductances and the capacitances of a resonant circuit are calculated by the finite element analysis results. From these values, the magnetic coupling coefficients are obtained. The secondary voltages and currents at the secondary core positions are calculated by using the resonant circuit and compared.

• 세라미스트
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• 제23권1호
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• pp.38-53
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• 2020

Magnetoelectric (ME) composites composed of magnetostrictive and piezoelectric materials derive interfacial coupling of magnetoelectric conversion between magnetic and electric properties, thus enabling to detect ultra-low magnetic field. To improve the performance of ME composite sensors, various research teams have explored adopting highly efficient magnetostrictive and piezoelectric phases, tailoring of device geometry/structure, and developing signal process technique. As a result, latest ME composites have achieved not only outstanding ME conversion coefficient but also sensing of ultra-low magnetic field below 1pT. This article reviews the recent research trend of ME composites for sensing of ultra-low magnetic field.

• 전기전자학회논문지
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• 제22권2호
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• pp.480-483
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• 2018

Wireless power transfer (WPT) is the technology that forces the power to transmit electromagnetic field to an electrical load through an air gap without interconnecting wires. This technology is widely used for the applications from low power smartphone to high power electric railroad. In this paper, the model of wireless power transfer circuit for the low power system is designed for a resonant frequency of 13.45 MHz. Also, a feedback WPT circuit to improve the power transfer efficiency is proposed and shown better performance than the original open WPT circuit, and the methodology for power efficiency improvement is studied as the coupling coefficient increases above 0.01, at which the split frequency is made.

• 한국초전도ㆍ저온공학회논문지
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• 제19권2호
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• pp.29-32
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• 2017

The use of electronic devices such as mobile phones and tablet PCs has increased of late. However, the power which is supplied through wires has a limitation of the free use of devices and portability. Magnetic-resonance wireless power transfer (WPT) can achieve increased transfer distance and efficiency compared to the existing electromagnetic inductive coupling. A superconducting coil can be applied to increase the efficiency and distance of magnetic-resonance WPT. As superconducting coils have lower resistance than copper coils, they can increase the quality factor (Q-factor) and can overcome the limitations of magnetic-resonance WPT. In this study, copper coils were made from ordinary copper under the same condition as the superconducting coils for a comparison experiment. Superconducting coils use liquid nitrogen to keep the critical temperature. As there is a difference of medium between liquid nitrogen and air, liquid nitrogen was also used in the normal conductor coil to compare the experiment with under the same condition. It was confirmed that superconducting coils have a lower reflection-coefficient($S_{11}$) than the normal conductor coils.