• Journal of electromagnetic engineering and science
• /
• v.16 no.4
• /
• pp.219-224
• /
• 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.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.53 no.8
• /
• pp.119-126
• /
• 2016

In this paper, we proposed the planar textile resonator for constructing wearable MR-WPT system and analyzed the characteristic of textile substrates used in resonators. The planar textile resonators were designed to resonate at 1-10 MHz. The loop and coil were fabricated planar structure on textile substrate using conductive materials. Polyester fiber and cotton widely used in real life were chosen as textile resonators for wearable applications and copper tape and silver paste were used for fabricating planar loop and coil on textile substrate. For comparison analysis on transfer efficiency according to the types of textile, transmitter and receiver parts were symmetric. According to the result, for the highest transfer efficiency of wearable WPT system, the planar resonators have specifications of relative thick textile substrate with low permittivity and low surface resistance of conductive pattern. The performed experiments show that the planar textile resonator is possible to be used for resonator in wearable MR-WPT system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.26 no.3
• /
• pp.300-304
• /
• 2015

This paper presents an omnidirectionally beam-steerable orthogonal loop resonator for wireless power transfer. The resonator is composed of two orthogonal loops. These connections of two loops and the current direction on the loops are determined by the control of switch. The magnetic field direction is determined by the vector sum of each loop current. The beam is steerable to eight directions by four switch modes. Using the suitable switch mode, the simulation and measurement efficiencies in the whole azimuthal direction are 56.3~60.0 %(deviation 3.7 %) and 41.2~48.7 %(deviation 7.5 %), respectively. The results show a little variation of transmission efficiency in the azimuthal direction.

• Proceedings of the KIEE Conference
• /
• 2015.07a
• /
• pp.16-17
• /
• 2015

본 논문에서는 자기 공명 방식을 이용한 10W급 무선 전력 전송 시스템을 제안하였다. 기존의 Mhz 대역의 자기 공명 방식과는 달리 본 논문에서는 100kHz 대역의 주파수를 이용한 시스템을 제안하여 송수신 코일 간의 거리와 효율을 증가시켰다. 본 논문에서 사용된 송수신 코일은 가로 세로 20cm로 크기와 모양이 같은 동일한 구조로 제작하였고, 20cm의 거리에서 약 50%의 전송 효율을 나타내었다. 수신기는 가변 커패시터를 사용하여 거리에 따라 달라지는 공진 주파수를 수동으로 찾을 수 있도록 설계하였다.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.17 no.2
• /
• pp.213-218
• /
• 2022

In this paper, a technology for a high-efficiency wireless power transmission transmitting and receiving coil that can wirelessly charge a drone is introduced. The drone station implements the ability to charge the battery wirelessly without the need to remove the battery to charge the drone's battery. In order to charge the drone's battery in the shortest time, wireless charging efficiency must be high. In order to increase the wireless charging efficiency of the drone station, a method for manufacturing high-efficiency transmitting and receiving coils and a performance measurement method are presented. Transmitting and receiving coils were manufactured considering the size and weight of the drone so as not to interfere with the flight of the drone. Efficiency of 88% or more was realized at a distance of 40mm or more between the transmitting and receiving coils.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.29 no.7
• /
• pp.566-569
• /
• 2018

A power line coupler that can apply high-frequency power to a railway overhead line structure was analyzed. It is difficult to supply auxiliary power to an overhead line in a high-voltage environment, and doing so requires a long-distance transfer. A method is proposed that utilizes the resonance on the Rogowski coil, which does not use a magnetic core. A simple overhead line structure was fabricated that consisted of a contact wire, messenger wire, and dropper. Couplers of various sizes were fabricated and deployed on the messenger wire, and the transfer characteristics of the two couplers were compared at a distance. As a result of applying the matching circuit to the coupler, the transmission efficiency was 53% at a distance of 2.5 m. The proposed method shows that it is possible to apply the auxiliary power by using the existing conductor in a special structure, such as the overhead line.