• Journal of Energy Engineering
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• v.8 no.1
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• pp.101-109
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• 1999

전력계통의 정태안정도 해석에서 발전기의 특성을 정확히 모델링하는 것을 해석결과의 정확도에 매우 큰 영향을 미치게 된다. 본 논문은 발전기 무한모선 계통을 사용하여 발전기의 특성을 정확히 해석하고자 하는 경우에 발전기의 포화특성을 종래의 동일축 전류성분에 의한 포화특성뿐만 아니라 교차자화 효과에 의한 포화특성까지 고려하여 보다 정확한 해석이 가능하도록 하였다. 동일축 성분의 포화 특성과 교차자화 효과에 의한 포화특성을 고려하여 발전기를 해석하기 위한 기준 좌표계로 발전기의 d축이 q축 보다 위상이 90$^{\circ}$앞서는 좌표계를 사용 관계식을 재정립하여 정태안정도 해석에 사용하던 기존의 발전기모델과 일치하도록 하였다. 사례연구를 통해서 포화특성을 정확히 고려하여 발전기를 모델링하는 것이 해석결과의 정확도에 매우 큰 영향을 미치는 것을 보였고, 다양한 계통조건에 대한 정태안정도 해석을 통해서 계통조건의 변화에 따라 포화특성에 영향을 미치는 요소들의 변화를 파악하였다.

• Journal of the Korean Vacuum Society
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• v.9 no.4
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• pp.428-435
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• 2000

Negative ion generation in an inductively coupled oxygen plasma was investigated by using a Langmuir probe. It was observed that the probe current ratio of the positive ion saturation current and the negative current which is consisted of the electron current and the negative ion current, and also the potential difference between the floating potential and plasma potential vary with the RF input power and more sensitively with the operating pressure, respectively. Results show that the operating condition to achieve the maximum probe current ratio and the minimum potential difference shift from the low pressure region to the high pressure regions with increasing the input power. It implies that the generation of the negative oxygen ions increases and the recombination of the positive and negative ions are enhanced in the plasma.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.237-238
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• 2007

전동기 코어 소재로 사용하는 무방향성 규소강판을 토로이달 형태가 아닌 전동기 적용 모형과 동일한 적층형으로 회전자 코어를 제작하여 초기 및 포화 자화 특성에 대한 고찰을 하였다. 초기자화 특성은 전동기가 처음 기동할 때 토크나 기동전류에 큰 영향을 미친다. 초기 자화 특성을 향상시키면 기동 전류를 줄일 뿐 아니라 전동기의 장기간 수명에도 영향을 미친다. 본 연구에서는 무방향성 규소강판의 가공, 설계, 제작 특성이 초기 기동 특성에 미치는 영향을 간접적으로 조사하기 위하여 초기로 포화 히스테리시스 특성에 대한 고찰을 실시하고 이들 요소가 갖는 여러 가지 가능성을 제시하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.4
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• pp.39-48
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• 2020

Since the fire accident of ESS (energy storage system) occurred at Gochang KEPCO Power Testing Center in August 2017, 29 fire cases with significant property losses have occurred in Korea. Although the cause of fire accidents have not been identified precisely, it should be considered battery and PCS (power conditioning system) as well as unbalance issues in the distribution system. In particular, circulating currents in a neutral line of a grid-connected transformer, which can affect a magnetized current, may have a negative effect on the ESS with unintentional core saturation and surge voltages at the secondary side of the transformer. Therefore, this paper proposes the modeling of the distribution system, which was composed of a substation, grid-connected transformer, and customer loads using PSCAD/EMTDC S/W, to analyze the phenomena of circulating current and surge voltages of the transformer with unbalanced currents in the distribution system. This paper presents a countermeasure for a circulating current with the installation of NGR (neutral grounding resistor) in grid-connected transformer. From the simulation results, it is clear that exceeding the circulating current and surge voltage at the secondary side of the transformer can be one of the causes of fire accidents.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.5 no.4
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• pp.211-215
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• 2012

Surgery equipment in operating room is very important at treatment procedure of patients. In this circuit of large equipment, a sudden change of current make big problem such as short circuit. when the current is converted suddenly, the current converter becomes in saturate and it caused by the induction curve of the inductor. in this case, the rates of the primary and secondary winding are broken and it becomes a open circuit. in this paper, we will look around the current transform of the primary and secondary winding when current converter becomes in saturate.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.3
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• pp.231-239
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• 1999

An improved version of current-regulated delta modulator (CRDM) is investigated for the output cunent control of v voltage-source inverters that have transformer-coupled series resonant load and are operated at the resonant frequency. Conventional CRDM has not only CUlTent offset problem but also transformer flux saturation problem when i it is applied to induction heating systems that have transformel-coupled loads. To cope with these problems, the effect of flux saturation is analysed, and simple method to av이d the problem is proposed. And integral type of CRDM is a adopted to remove the cunent offset. The boundaries of integrator gain for stable operation is calculated using the c concept of sliding mode controL The validity of proposed strategy is vel퍼ed through simulations and prototype e experiments.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.8 no.5
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• pp.49-55
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• 1994

평판 디스플레이용 비정질 실리콘 박막 트랜지스터의 전기적인 특성과 수학적인 모델에 대하여 연구되었고 이론적인 모델은 실험을 통하여 그 타당성을 입증하였다. 게이트전압이 고정된 상태에서 드레인 전압 증가에 따른 드레인 포화전류는 증가되었고 디바이스의 포화는 드레인 전압이 증가될수록 더 증가되었으며 문턱전압은 감소되었다. 세 개의 변수로 구성된 디바이스의 전달특성과 출력특성에 대한 실험 결과값에 대한 모델식이 제시되었는데 이 모델은 디비이스의 기하학적인 구조를 간단화 하기위한 모델식이다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.2
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• pp.94-98
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• 2007

The fault current limiting characteristics of a flux-lock type superconducting fault current limiter (SFCL) considering hysteresis characteristics of a flux-lock reactor, which is an essential component of the flux-lock type SFCL, were investigated. In the normal state, the hysteresis loss of iron core in the flux-lock type SFCL does not happen due to its winding's structure. From the equivalent circuit for the flux-lock type SFCL and the fault current limiting experiments, the hysteresis curves could be drawn. Through the hysteresis curves together with the fault current level due to the inductance ratio between the primary and the secondary windings, the increase of the number of turns in the secondary winding of the flux-lock type SFCL made the fault current level increase. On the other hand, the saturation of iron core was prevented.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.10
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• pp.29-34
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• 2007

The fault current limiting characteristics of a flux-lock type superconducting fault current limiter(SFCL) according to fault angles were investigated. From the electrical equivalent circuit with the magnetization branch, the inner magnetic flux of this SFCL due to fault angles was induced and its effect on the limited fault current was analyzed. From the fault current limiting experiments, the exciting current, which described the saturation of the iron core, was calculated and its dependence on the fault angle was analyzed. Before the fault happened, the exciting current did not happen, that it kept zero value. However, after the fault happened, the exciting current flowed and, the exciting current in case of the additive polarity winding showed higher value than for the case of the subtractive polarity winding. The analysis results were compared with the experimental ones, and experimental results agreed with the analysis ones.

• 한국지구물리탐사학회:학술대회논문집
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• 2009.10a
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• pp.90-92
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• 2009