• 전기학회논문지
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• 제58권1호
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• pp.35-41
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• 2009

This paper proposes a stand alone type single-phase fuel cells micro-source with a voltage sag compensator for compensating the ac output voltage variations (sag or swell) of micro-source. The proposed micro-source is consist of a PEM(polymer electrolyte membrane) fuel cells simulator, a full bridge de converter, a 60Hz PWM(pulse width modulation) VSI(voltage source inverter), and a voltage sag compensator. Voltage sag compensator is similar to the configuration of hybrid series active power filter, and it is directly connected to micro-source through the injection transformer. Compensation algorithm of a voltage sag compensator adopts a single phase p-q theory. Effectiveness of the proposed the system is verified by the PSIM(power electronics simulation tool) simulation in the steady state and transient state which the proposed system is able to simultaneously compensate the harmonic current and source voltage sag or swell.

• 한국표면공학회지
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• 제29권6호
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• pp.735-738
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• 1996

Amorphous nickelphthalocyanine(NiPc) thin films were prepared by vacuum evaporation and their electrochromic behavior and voltammograms were examined in the five kinds of aqueous electrolytes. Amorphous NiPc films were prepared on indium-tin-oxide(ITO) glass substrates cooled to-$120^{\circ}C$ by using liquid nitrogen under a vacuum of $2.4 \times 10^{-4}$. The voltammetric and electrochromic measurements were made using a potential galvanostat. In order to confirm the color change, optical vis-transmission spectra of the NiPc films were measured by a spectrophotometer with various electrode potential applied. The NiPc amorphous thin films exhibited most clearly electrochromism in $KNO_3$ aqueous electrolyte. The specimen films underwent 3 color transitions (from blue to yellow-green, then to red violet, then to dark blue), corresponding to the three peaks on the voltammograms in $KNO_3$ aqueous electrolyte. Blue is color of the as-prepared film. When the potential was swept, charge compensation was attained upon oxidation by injection of anions from the electrolyte and upon reduction by expulsion of anions.

• 대한조선학회논문집
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• 제42권2호
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• pp.73-79
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• 2005

The characteristics of a tilt sensor utilizing the resistance change of an electrolyte associated with inclination is investigated, and a dynamic compensation modeling is proposed to make the real-time measurement of the absolute slope possible even with sporadically dynamic motion. Although the proposed system is small, economical and accurate for quasi-steady slope measurement, since it contains a freesurface the evolution of the liquid surface that has no direct relation to the real slope must be excluded for any rapid rotations or translations. For various artificial motions the response of the sensor is analyzed and simplified modeling equations are proposed.

• 전력전자학회논문지
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• 제15권1호
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• pp.75-85
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• 2010

본 연구에서는 비선형 부하에서 발생되는 기본파 무효전력 및 고조파를 보상하기 위한 종전의 전압형 및 전류형 PWM 능동전력필터를 대체 할 수 있는 Z-소스 인버터 토폴로지의 하이브리드 능동전력필터에 대하여 고찰하였다. Z-소스 토폴로지의 능동전력필터의 보상 DC전원으로는 PEMFC가 사용되며, Z-소스 인버터의 shoot-through 듀티비의 조절에 의하여 낮은 연료전지의 전압을 높은 보상 전압으로 부스트 한다. 제안된 시스템은 병렬형 Z-소스 능동전력필터와 7차 고조파 (420Hz) 동조 필터로 구성되며, 이 구성에 의하여 Z-소스 능동전력필터의 스위치 디바이스의 전압 스트레스는 감소된다. 제안된 Z-소스 하이브리드 능동전력필터의 보상 알고리즘으로는 전류 동기 검출법이 사용되었다. 3상 220V/60Hz, 25A급 비선형 다이오드 부하 조건하에서 PSIM 시뮬레이션을 수행하였으며, 정상상태 및 과도상태에서의 제안된 시스템의 보상 성능을 파악하였다.

• 대한의용생체공학회:의공학회지
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• 제19권6호
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• pp.595-602
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• 1998

근관장 측정기 중 주파수 의존형이 다른 방법보다 정확도도 높고 사용이 간편한 것으로 평가되고 있다. 그러나 주파수 의존형 또한 실제 임상 사용시 근관내의 전해질 유무에 영향을 받는다. 본 연구에서는 전해질의 영향을 최소화한 자동 보정 주파수 의존형 전자 근관장 측정기를 개발하였다. 또한 500Hz와 10kHz가 임피던스 측정을 위해 사용되는 교류신호로써 측정오차를 최소화하는 최적 주파수임을 상품화된 제품의 주파수(400Hz, 8kHz)와 비교하여 확인하였으며, 신호의 파형에 따른 통계적 유의성은 없었다(p>0.05). 두 신호의 임피던스 비는 파일의 근관 내의 위치를 알려주고, 본 연구에서 적용한 두 신호의 전압차는 근관내 용액의 상태를 나타내 준다. 전압차를 이용하여 보정한 결과 측정오차를$H_2O_2$ 용액에서는 평균 +0.54mm에서 +0.18mm로(p<0.01), NaOCl 용액에서는 평균 -0.33mm에서 -0.01mm로(p<0.01) 줄일 수 있었다. 정확도는 허용오차를 ${\pm}$0.5mm를 기준으로 할 때, $H_2O_2$ 용액에서는 71.1%에서 91.1%로, NaOCl 용액에서는 82.2%에서 100%로 향상시켰다.

• 전기학회논문지P
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• 제66권2호
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• pp.82-87
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• 2017

This paper presents performance improvement of CO gas sensor signal conditioner for early fire warning system. The warning system is based on the CO sensor and its advanced signal conditioning modules network that employ electochemical gas sensor. The electochemical has advantage of having a linear output and operating with a low consumption and fast response. This electrochemical gas sensor contains a gas membrane and three electrodes(working, counter, reference electrode) in contact with an electrolyte. To use a three-electrode sensor, a voltage has to be applied between the working and the reference electrode according to the specification of the sensor. In this paper, we designed these requirements that should be considered in temperature compensation algorithm and electrode measurement of CO sensor modules by using advanced signal conditioning method included 3-electrode. Simulation and experimental results show that signal conditioner of CO sensor module using 3-electrode have a advantage linearity, sensitivity and stability, fast response etc..

• 한국안전학회지
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• 제37권2호
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• pp.76-87
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• 2022

Lithium-ion batteries (LIBs) have attracted much interest for their high energy density (>150 mAh/g), high capacity, low self-discharge rate, and high coulombic efficiency. However, with the successful commercialization of LIBs, fire and explosion incidents are likely to increase. The thermal runaway is known as the major factor in battery-related accidents that can lead to a series of critical conditions. Considering this, recent studies have shown an increased interest in countering the safety issues associated with LIBs. Although safety standards for LIB use have recently been formulated, little attention has been paid to the safety around the manufacturing process for battery products. The present study introduces a risk assessment method suitable for assessing the safety of the LIB-manufacturing process. In the assessment method, a compensation parameter (Z-factor) is employed to correctly evaluate the process's safety on the basis of the type of material (e.g., metal anode, liquid electrolyte, solid-state electrolytes) utilized in a cell. The proposed method has been applied to an 18650 cell-manufacturing process, and three sub-processes have been identified as possibly vulnerable parts (risk index: >4). This study offers some crucial insights into the establishment of safety standards for battery-manufacturing processes.