• 한국발생생물학회지:발생과생식
• /
• 제4권2호
• /
• pp.243-250
• /
• 2000

To find the mechanism underlying the ADP-induced increase in the outward current in ovulated mouse oocytes, we examined changes in voltage-dependent currents using the whole cell voltage clamp technique and the internal perfusion technique. Eggs were collected from the oviduct of superovulated mice with PMSG and hCG. Membrane potential was held at -60 mV (or -80 mV in the case of recording $Ca^{2＋}$ currents) and step depolarizations or hyperpolarizations were applied for 300 ms. By step depolarizations, outward currents comprising steady-state and time-dependent components were elicited. They were generated in response to the positive potential more than 20 mV with severe outward rectification and were blocked by external TEA, a specific $K^{＋}$ channel blocker, suggesting that they be carried via $K^{＋}$ channels. Internally-perused 5 mM ADP gradually increased outward $K^{＋}$ currents (IK) 1 min after perfusion of ADP and reached slowly to maximum (150~170％) 5 min later over the positive potential range, implying that ADP might not be acted directly to the $K^{＋}$ channels. IK were decreased by 5 mM ATP without affecting the steady-state component of outward current. In contrast to the effect of ADP and ATP on IK, both effect of ATP and ADP on inward $Ca^{2＋}$ currents (ICa) could not be detected due to the continuous decrease in current amplitudes with time-lapse ("run-down" phenomena). To check if there is a G protein-involved regulation in the ionic current of mouse oocytes, 1 mM GTP was applied to the cytoplasmic side, and the outward current and inward currents were recorded. ICa was promptly increased in the presence of GTP whereas IK was not changed. from these results, it is concluded that the ATP-dependent regulation is likely linked in the ADP-induced increase in the outward $K^{＋}$ current, and G protein-involved cellular signalling might affect ion channels carrying $Ca^{2＋}$ and $K^{＋}$ in mouse oocytes.

• 한국산학기술학회논문지
• /
• 제8권4호
• /
• pp.748-757
• /
• 2007

본 논문은 대용량 유도전동기가 기동할 때 발생하는 큰 돌입전류로 인해 PCC(Point of Common Coupling)에 심한 전압 강하가 발생하게 되어 기동에 실패하는 문제를 해결하기 위해 대상 유도전동기의 기동 특성과 배전계통을 모델링하고 시뮬레이션을 수행함으로써 유도기 기동시에 전압저하 현상을 해석하였다. 문제가 되는 유도전동기는 2500KVA 용량의 펌프용 농형 유도전동기로 리액터 기동법을 채용하고 있다. 2500KVA 유도전동기 한대의 기동에는 문제가 없으나 기동 완료 후 PCC 전압이 다소 떨어진다. 하지만 추가로 동일 용량의 유도전동기가 기동하게 되면 PCC의 심한 전압강하로 기동에 실패하게 되는 문제가 발생하였다. 이러한 문제 해결을 위해 본 논문에서는 실제 기기의 기동시 토크-속도 곡선을 이용한 유도전동기의 기동 특성을 정확히 모델링하고 시뮬레이션을 수행하여 두 대의 대용량 유도전동기가 순차적으로 기동에 성공할 수 있는 적절한 전압보상 방안을 제안하였다. 본 논문에서 논의되는 대용량 유도전동기는 한국수자원공사의 취수장에서 운전되고 있으며 대상 유도전동기 및 배전계통은 PSCAD/EMTDC 소프트웨어를 사용하여 모델링 및 시뮬레이션을 수행하였다.

• 전기전자학회논문지
• /
• 제13권2호
• /
• pp.208-215
• /
• 2009

본 논문에서는 DT-CMOS(Dynamic Threshold voltage CMOS) 스위칭 소자를 사용한 모바일 기기용 고 효율 전원 제어 장치(PMIC)를 제안하였다. 휴대기기에서 필요한 높은 출력 전압과 낮은 출력 전압을 제공하기 위하여, 부스트 변환기(Boost Converter)와 벅 변환기(Buck Converter)를 원칩(One-chip)으로 구현하였다. 그리고 높은 출력 전류에서 고 전력 효율을 얻기 위하여 PWM(Pulse Width Modulation) 제어 방식을 사용하여 PMIC를 구현하였으며, 낮은 온 저항을 갖는 DT-CMOS를 설계하여 도통 손실을 감소시켰다. Voltage-mode PWM 제어 회로와 낮은 온 저항 스위칭 소자를 사용하여 구현한 부스트 변환기와 벅 변환기는 100mA 출력 전류에서 92.1%와 95%의 효율을 구현하였으며, 1mA이하의 대기모드에서도 높은 효율을 구현하기 위하여 LDO를 설계하였다.

• Journal of Power Electronics
• /
• 제15권2호
• /
• pp.356-365
• /
• 2015

This paper presents a new single phase front-end ac-dc bridgeless power factor correction (PFC) rectifier topology. The proposed converter achieves a high efficiency over a wide range of input and output voltages, a high power factor, low line current harmonics and both step up and step down voltage conversions. This topology is based on a non-inverting buck-boost (Zeta) converter. In this approach, the input diode bridge is removed and a maximum of one diode conducts in a complete switching period. This reduces the conduction losses and the thermal stresses on the switches when compare to existing PFC topologies. Inherent power factor correction is achieved by operating the converter in the discontinuous conduction mode (DCM) which leads to a simplified control circuit. The characteristics of the proposed design, principles of operation, steady state operation analysis, and control structure are described in this paper. An experimental prototype has been built to demonstrate the feasibility of the new converter. Simulation and experimental results are provided to verify the improved power quality at the AC mains and the lower conduction losses of the converter.

• 한국조명전기설비학회:학술대회논문집
• /
• 한국조명전기설비학회 2007년도 추계학술대회 논문집
• /
• pp.195-197
• /
• 2007

This paper presents experimental results on the safety of persons due to a ground fault in 22.9 kV-Y distribution system In order to evaluate the touch voltages due to internal ground faults in a step down transformer based on the newly prescribed KS C IEC 60364 standard series, the verification tests in a 22.9 kV multi-grounded neutral system were carried out From the experimental results, it was found that there will be significant potential rise jeopardizing LV equipment insulation in case of separate grounding between HV and LV system and the effective measures against hazardous touch voltages due to a IN side ground fault in the common grounding system between HV and LV system are proposed. As a consequence, it was found that the equipotential bonding is an important prerequisite for the effectiveness of the protective measures for the safety of persons in the common ground system between 22.9 kV-Y and low-voltage grounding system.

• Journal of Electrical Engineering and Technology
• /
• 제1권1호
• /
• pp.63-72
• /
• 2006

The purpose of this raper is to address the negative impedance instability in DC/DC converters. We present the negative impedance instability of PWM DC/DC converters loaded by constant power loads (CPLs). An approach to design digital controllers for DC/DC converters Is presented. The proposed method, called Power Alignment control technique, is applied to DC/DC step-down choppers operating in continuous conduction or discontinuous conduction modes with CPLs. This approach uses two predefined state variables instead of conventional pulse width modulation (PWM) to regulate the output voltage. A comparator compares actual output voltage with the reference and then switches between the appropriate states. It needs few logic gates and comparators to be implemented thus, making it extremely simple and easy to develop using a low-cost application specific integrated circuit (ASIC) for converters with CPLs. Furthermore, stability of the proposed controllers using the small signal analysis as well as the second theorem of Lyapunov is verified. Finally, simulation and analytical results are presented to describe and verify the proposed technique.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1996년도 하계학술대회 논문집 A
• /
• pp.461-463
• /
• 1996

A FB-ZVS(Full Bridge Zero Voltage Switching) PWM DC/DC converter for electric vehicles is analyzed in this paper. The converter considered is a step-down DC/DC converter with the ratings of 3l2/I3.5V and 1.35kW. The steady state analysis of this converter is divided into six operating modes. Digital simulations using PSPICE are carried out to verify the steady-state analysis.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1993년도 정기총회 및 추계학술대회 논문집 학회본부
• /
• pp.114-116
• /
• 1993

A novel Neural networks controller for Buck type DC-DC converter is presented and compared with the operation of sliding node coupled several control strategies for the converter. The connection weights of neural networks are trained by error back propagation algorithm. The behavior of the control system that arises fred the use of those methods is analyzed from the viewpoint of dynamic and steady state errors and simulation results are presented.

• Journal of Electrical Engineering and Technology
• /
• 제5권3호
• /
• pp.477-483
• /
• 2010

This paper is studied on a novel buck-boost isolated converter for high efficiency and high power factor. The switching devices in the proposed converter are operated by soft switching technique using a new quasi-resonant circuit, and are driven with discontinuous conduction mode (DCM) according to pulse width modulation (PWM). The quasi-resonant circuit makes use of a step up-down inductor and a loss-less snubber capacitor. The proposed converter with DCM also simplifies the requirement of control circuit and reduces a number of control components. The input ac current waveform in the proposed converter becomes a quasi sinusoidal waveform in proportion to the magnitude of input ac voltage under constant switching frequency. As a result, it is obtained by the proposed converter that the switching power losses are low, the efficiency of the converter is high, and the input power factor is nearly unity. The validity of analytical results is confirmed by some simulation results on computer and experimental results.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2013년도 전력전자학술대회 논문집
• /
• pp.362-363
• /
• 2013

기존 Fan Motor용 인버터의 경우, 높은 전압으로 인버터를 구동하기 때문에 높은 내압의 IPM을 사용해야 하는 문제점이 있다. 본 논문은 Fan Motor 구동용 인버터의 내압을 줄일 수 있는 Dual 공진 강압형 DC/DC 컨버터를 제안한다. 기존의 강압형 DC/DC 컨버터를 사용할 경우에는 큰 인덕터를 사용하기 때문에 회로의 전체적인 부피가 커지고 제작단가가 증가하는 단점이 있다. 반면 제안된 회로는 작은 크기의 인덕터를 사용한 Dual 공진 강압형 DC/DC 컨버터로써, 낮은 출력전압으로 인버터 구동이 가능하고, 영전압 스위칭을 하기 때문에 소형화 및 고효율화가 가능한 장점을 갖는다. 본 논문에서는 제안된 회로의 이론적인 특성을 분석하고 모의실험을 통해 확인하였으며, 1.8kW급 Fan Motor 구동용 인버터 회로에 적용하여 실험을 통해 우수성을 검증하였다.