• 전력전자학회:학술대회논문집
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• 전력전자학회 1999년도 전력전자학술대회 논문집
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• pp.282-286
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• 1999

This paper presents a vector control of parallel drive, a beatless control and a low switching PWM technique for the propulsion system of Electric car as transient state which are included interrupting line voltage, changing line voltage slowly, suddenly, regenerating light load and starting from backward running. Improved performance and a validation of proposed method is shown by the experimental results using a 1.65MVA IGBT VVVF inverter and inertia load equivalent to 160 tons electric cars through a running and transient state test.

• 전기전자학회논문지
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• 제24권2호
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• pp.598-603
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• 2020

본 논문에서는 Push-Pull 패스 트랜지스터 구조로 인하여 향상된 Load Transient 특성을 향상시킨 LDO(Low Drop-Out)를 제안하였다. LDO 레귤레이터 내부의 오차증폭기의 출력단과 패스 트랜지스터의 게이트단 사이에 제안된 Push-Pull 회로와 출력단에 Push-Pull 회로를 추가하여 전압 라인에 들어오는 Overshoot, Undershoot를 개선시켜 기존의 LDO 레귤레이터보다 개선된 Load Transient 특성의 델타 피크 전압 값을 갖는다. 제안하는 회로는 Cadence의 Virtuoso, Spectre 시뮬레이션을 이용하여 삼성 0.13um 공정에서 특성을 분석하였다.

• The Journal of the Acoustical Society of Korea
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• 제17권2E호
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• pp.53-58
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• 1998

In this paper, we study the response of several anisotropic systems to buried transient line loads. The problem is mathematically formulated based on the equations of motion in the constitutive relations. The load is in form of a normal stress acting with arbitrary axis on the plane of monoclinic symmetry. Plane wave equation is coupled with vertical shear wave, longitudinal wave and horizontal shear wave. We first considered the equation of motion in reference coordinate system, where the line load is coincident with symmetry axis of the orthotrioic material. Then the equation of motion is transformed with respect to general coordiante system with azimuthal angle by using transformation tensor. The load is first described as a body force in the equations of the motion for the infinite media and then it is mathematically characterized. Subsequently the results for semi-infinite spaces is also obtained by using superposition of the infinite medium solution together with a scattered solution from the free surface. Consequently explicit solutions for the displacements are obtained by using Cargniard-DeHoop contour. Numerical results which are drawn from concrete examples of orthotropic material belonging to monoclinic symmetry are demonstrated.

• Journal of Electrical Engineering and Technology
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• 제11권3호
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• pp.675-682
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• 2016

Sudden voltage drops and outages frequently disturb the operation of sensitive loads for domestic, commercial, and industrial use. In some cases, these events may even impair the functioning of relevant equipment. To maintain power under such conditions, a UPS system is usually installed. Once a disturbance happens at the grid side, the line-interactive UPS system takes over the load to prevent an interruption. But, due to magnetic saturation of the transformer, a significant inrush current may occur for the transformer-coupled loads during this transition. The generation of such transient currents may in turn decrease the line voltage and activates over-current protecting devices of the system. In this work, a cost-effective, line-interactive UPS system is proposed that eliminates the inrush current phenomenon associated with transformer-coupled loads. The strategy was implemented by connecting a standard current-regulated voltage source inverter (CRVSI) to the secondary winding of the load transformer. During any transient condition at the grid side, the load current is monitored and regulated to achieve either seamless compensation of the load current or complete transferal of load from grid to the inverter. Experimental results were obtained for a prototype under all possible operating conditions so as to validate the performance of the proposed topology.

• 전기전자학회논문지
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• 제23권2호
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• pp.552-556
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• 2019

본 논문에서는 전류 제어 회로를 이용하여 load Transient response 특성을 향상시킨 capless LDO(low drop-out) 레귤레이터를 제안하였다. LDO 레귤레이터 내부의 오차증폭기와 패스 트랜지스터 사이에 전류 조절 회로를 두어 전압 라인에 들어오는 전류특성을 개선시켜 기존의 LDO 레귤레이터보다 향상된 transient 응답특성을 갖는다. 제안된 회로는 cadence의 virtuoso, spectre 시뮬레이터를 이용하여 0.18 um 공정에서 특성을 분석하였다. 실험 결과에 따르면, 제안된 회로 구성을 이용한 LDO의 load transient response는 기존 LDO과 비교하여 부하 전류가 rising time인 경우 1.954 us에서 1.378 us, falling time인 경우 19.48 us에서 13.33 us으로 약 29%, 28% 개선된 응답속도를 가진다.

• 대한전기학회논문지:전력기술부문A
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• 제53권7호
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• pp.397-404
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• 2004

This paper describes a study of transient characteristics in 765kV untransposed transmission lines. As the 765(kV) system can carry bulk power, some severe fault on the system nay cause large system disturbance. The large shunt capacitance and small resistance of 765kv transmission line make various difficulties for its protection. These problems including current difference between sending and receiving terminals on normal power flow, low order harmonic current component in fault current and current transformer saturation due to the long DC time constant of the circuit etc. must be investigated and solved. The analysis of transient characteristics at sending terminal has been carried out for the single phase to ground fault and 3-phase short fault, etc. The load current, charging current in normal condition and line flows, fault current, THD(Total Harmonic Distortion) of harmonics, time constants have been analysed for the 765kV untransposed transmission line systems.

• 전기의세계
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• 제18권1호
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• pp.24-29
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• 1969

This is preliminary study concerning the future construction and operation of 345KV power transmission line in Korea which will be added to the existing 161KV power system by the end of 1970 in order to increase the power carrying capacity between Seoul and Pusan area; 350 kilo meters aparts, in accordance with the ambitious second five years power development schedule of Korea Electric Company. The result of this study says that an intermidiate switching station should be installed at the middle position of the line to improve the transient stability of the system, considerable amount of capacitors or synchronous condenser are to be installed to reduce the voltage drop at receving end of line during the heavy load hours, and also in some measure to avoid the voltage rise by self-excitation of power generators during the light load hours and while energizing the line. This is the first attempt to realize the EHV power transmission line in Korea so that the additional study is necessary on the kind and size of conductors, the necessary number of insulators and the suitable clearance distances between conductor and steel tower or earth from the technical and economical view points. These are necessary steps to be taken by the writer before getting into the calculation on the transient stablity of the power system.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2005년도 춘계학술대회논문집
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• pp.406-408
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• 2005

In this literature, when the utility line is normal, the Off-Line UPS operates as an active power filter to compensate the reactive power from a load, and when the utility line is in outage, the On-Line UPS opuates as in single phase inverter to supply an active and reactive power to the load. An additional static switch in UPS was used to decrease an transient state during these mode changes. And the result shows that the transient state disappeared.

• 한국압력기기공학회 논문집
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• 제14권2호
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• pp.77-87
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• 2018

In the case of high-energy line breaks in nuclear power plants, supersonic steam jet is formed due to the rapid depressurization. The steam jet can cause impingement load on the adjacent structures, piping systems and components. In order to secure the design integrity of the nuclear power plant, it is necessary to evaluate the load characteristics of the steam jet generated by high-energy pipe rupture. In the design process of nuclear power plant, jet impingement load evaluation was usually performed based on ANSI/ANS 58.2. However, U.S. NRC recently pointed out that ANSI/ANS 58.2 oversimplifies the jet behavior and that some assumptions are non-conservative. In addition, it is recommended that dynamic analysis techniques should be applied to consider transient load characteristics. Therefore, it is necessary to establish an evaluation methodology that can analyze the dynamic load characteristics of steam jet ejected when high energy pipe breaks. This research group has developed and validated the CFD analysis methodology to evaluate the transient behavior of supersonic impinging jet in the previous study. In this study, numerical study on the transient load characteristics of supersonic steam jet impingement was carried out and amplitude and frequency analysis of transient jet load was performed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.740-741
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• 2007

This paper analyses the transient state of underground distribution system against single line to ground fault in underground transmission systems, when underground transmission systems and distribution systems are made of common grounding. Underground transmission systems and distribution systems are modeled by EMTP/ATPDraw. Simulation is carried out considering variation of parameters such as value of common grounding, balance load and unbalance load.