• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.224-224
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• 2015

Gel have enormous applicable region due to inherently high stretchability and bio-compatibility. Here, we fabricated highly stretchable electronic conductive organogels which have long-term stability in environment. By introducing a dialysis step which can incorporate conducting polymer, PEDOT, on the procedure of gel synthesis, residual ions inside the gel were removed. In addition, we replaced the water with organic solvent, EG, inside the gels which is high stability in air. Unlike conventional hydrogels, there are no ionic conduction occurred and electrochemically driven current was prevented during electrical voltage was applied. The fabricated organogels are hardly dried during air exposure, and only electrically conductive without any electrochemical reaction at even high voltage. In order to utilize as stretchable conductor, we demonstrated a LED array circuit using the conductive organogels as electrical interconnects. It was successfully operative even stretched up to 300% strain.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1198-1201
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• 2005

A new foxtail actuator driven by V-shape beam deflection using electrostatic force has been designed, fabricated and characterized for nano-resolution manipulators. The proposed foxtail mechanism was implemented using a pair of electrostatic actuators and a pair of holding actuators, which was analyzed based on the electromechanically coupled motion of voltage - displacement relation. The proposed actuator was fabricated onto Silicon-on-Insulator (SOI) wafer and its stepping characteristics were measured by micro optical interferometer consisting of integrated micromirror and optical fiber. The fabricated foxtail microactuator was successfully operated from 1nm to 76nm, and the magnitude of step displacement was controllable up from 26nm/cycles to 53nm/cycle by changing the voltage.

• 전기학회논문지P
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• 제66권4호
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• pp.151-157
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• 2017

In this paper, it is the result of analysis of the stability by power system analysis about the influence on the power system when the southwest - offshore wind power demonstration complex is constructed to 60MW and it is linked with the onshore power system. Considering the position of the wind turbine actually installed and the length of the cooperating line, we modeled the wind generators, offshore substation and the turbine step-up transformer. Changes of voltage when internal and external faults occurred is analyzed and the reactive power demand according to the amount of electricity generation is derived. And also phase angle stability and frequency is observed through a transient analysis. This paper clarify that there is no problem in the system when only offshore wind power is linked with the grid and try to present the reactive power amount necessary for maintaining the voltage of the point of cooperation appropriately.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1064_1065
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• 2009

PV (Photovoltaic) power generation system has been widely studied as a clean and renewable power source. Tracking the MPP (maximum power point) of a PV array is usually an essential part of a PV system. This paper describes POS (Photovoltaic Output Sensorless) MPPT method and optimization technique of its operational characteristics for grid-connected PV generation system. A DC-DC converter has been used to step-up the PV voltage and DC-AC converter has been used for connecting the system to the grid. Optimization technique has been implemented to optimize the current and voltage controller gain parameters and duty ratio increment of DC-DC converter. Simulation results reveal that the proposed control has better response.

• 조명전기설비학회논문지
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• 제28권12호
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• pp.13-17
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• 2014

In this paper, the risk of electric shock is analyzed through analysis for characterization of potential distribution analysis and ground fault current analysis near the area where there are occurred a ground fault at electric vehicle wireless charging system using 20kHz. Studies for electric vehicle wireless charging system are in the works for development of efficiency increase, pickup shape design and communication module as a fundamental research step. But the research related to electrical safety and is still scarce state so that more studies are necessary to commercialize. As a result of analysis, it is verified that induced voltage is arisen more up to 45V near the a area of accident during ground fault and fault current has been maintained continuously without clearing fault condition by operating characteristics for circuit breaker and inverter.

• 대한기계학회논문집B
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• 제32권3호
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• pp.231-234
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• 2008

For the applications which need a micro-power supply such as thin and flat displays, micro-robot, and micro-system, it is especially necessary to integrate the passive components because they typically need more than 2/3 of the space of the conventional circuit. Therefore, we have designed and fabricated a novel piezoelectric micro transformer using the PZT thin film and MEMS technologies for application to the energy supply device of the micro-systems. The dimensions of the micro-transformer is $1000{\mu}m\;{\times}\;400{\mu}m\;{\times}\;4.8{\mu}m$ $(length{\times}width{\times}thickness)$. The dynamic displacement of around $9.2{\pm}0.064{\mu}m$ was observed at 10 V. The dynamic displacement varied almost linearly with applied voltage. The average voltage gain (step-up ratio) was approximately 2.13 at the resonant frequency $(F_r=8.006KHz)$ and load resistance $(R_L)$ of 1 $M{\Omega}$.

• 한국전기전자재료학회논문지
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• 제20권11호
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• pp.948-952
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• 2007

In this study, a low temperature sintering multilayer piezoelectric transformer for a DC-DC converter was manufactured using $(Pb,Ca,Sr,)(Ti,Mn,Sb)O_3$ ceramics. Its electrical properties were investigated according to the variation in frequency and load resistance. The voltage step-up ratio of the multilayer piezoelectric transformer showed a maximum value at a resonant frequency of input part and increased with an increase of load resistance. The efficiency of the multilayer piezoelectric transformer showed the highest value at a load resistance of 17 $\Omega$. The output power was increased with increasing input voltage. Temperature increase of the multilayer piezoelectric transformer was increased with the increase of output power. At the load resistance of 17 $\Omega$, the multilayer piezoelectric transformer showed the temperature rises of about $20^{\circ}C$ at the output power of 18 W, and stable driving characteristics.

• 한국전기전자재료학회논문지
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• 제34권6호
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• pp.480-486
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• 2021

Magnetoelectric (ME) composite is composed of a piezoelectric material and a magnetostrictive material. Among various ME structures, 2-2 type layered ME composites are anticipated to be used as high-sensitivity magnetic field sensors and energy harvesting devices especially operating at its resonance modes. Rosen type piezoelectric transducer using piezoelectric material is known to amplify a small electrical input voltage to a large electrical output voltage. The output voltage of these Rosen type piezoelectric transducers can be further enhanced by modifying them into ME composite structures. Herein, we fabricated Rosen type ME composites by sandwiching Rosen type PMN-PZT single crystal between two Ni layers and studied their ME coupling. However, the voltage step-up ratio at the resonance frequency was found to be smaller than the value calculated with α_ME value. The ATILA FEA (Finite Elements Analysis) simulation results showed that the position of the nodal point was changed with the presence of a magnetostrictive layer. Thus, while designing a Rosen type ME composite with high performance in a resonant driving situation, it is necessary to optimize the position of the nodal point by optimizing the thickness or length of the magnetostrictive layer.

• 한국전기전자재료학회논문지
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• 제19권7호
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• pp.655-661
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• 2006

Dielectric and piezoelectric properties of PMN-PZT ceramics with a high mechanical quality factor$(Q_m)$ and a low temperature sintering temperature were investigated as a function of PZN substitution in order to develop multilayer piezoelectric transformer for AC-DC converter. Multilayer piezoelectric transformers were subsequently manufactured using the PMN-PZN-PZT ceramic offering the optimal behavior and then the electrical performance were invetigated. At the sintering temperature of $940^{\circ}C$, density, electromechanical coupling factor$(k_p)$, mechanical qualify factor$(Q_m)$ and dielectric constant$(\varepsilon_r)$ of 8 mol% PZN substituted specimen were $7.73g/cm^3$, 0.524, 1573 and 1455, respectively. The PZN substitution caused a increase in the dielectric constant and the electromechnical coupling factor. The voltage step-up ratio of multilayer piezoelectric transformer showed the maximum value at near the resonant frequency of 76.55 kHz and increased according to the increase of load resistance. The multilayer piezoelectric transformer with the output impedance coincided with the load resistance showed the temperature increase of less than $20^{\circ}C$ at the output power of 10 W. Based on the results, the manufactured multilayer transformer using the low temperature sintered PMN-PZN-PZT ceramics can be stably driven for both step-up and down transformers.

• 마이크로전자및패키징학회지
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• 제15권3호
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• pp.19-25
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• 2008

본 논문에서는 고역률과 고효율로 동작하는 새로운 스텝-업 AC-DC 초퍼에 대해 제안한다. 제안한 초퍼는 전류 불연속제어로 구동되고, 스위치의 듀티율 일정제어에 의해 입력전류는 교류 입력전압의 크기에 비례된 불연속적인 정현파 형태로 주어진다. 그 결과 입력역률은 거의 단위역률로 되고, 듀티율 일정제어에 의해 제안한 초퍼는 제어기법이 간단하게 된다. 일반적으로 전류불연속 제어에 의한 초퍼의 경우, 사용된 스위치의 턴-온 동작은 영전류 스위칭으로 되는 장점이 있지만, 스위치의 턴-오프 동작은 최대 전류에서 스위칭되어 스위칭 손실을 증대시키고 스위치의 과중한 스트레스를 가져오게 된다. 이것은 AC-DC 초퍼의 효율을 저하시키는 요인이다. 본 논문에서는 부분공진기법에 의한 새로운 소프트 스위칭 회로가 설계되어 사용된 제어스위치들의 턴-온, 턴-오프 동작을 소프트 스위칭으로 만들어 초퍼의 효율을 증대시킨다.