• 조명전기설비학회논문지
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• 제25권2호
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• pp.120-125
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• 2011

SPDs are increasingly being used against lightning and switching surge according to the applicable revised standard and equipotential grounding system. SPDs are equipped usually with a MOV voltage regulating element. The MOV, however, always is exposed to the danger of thermal runaway resulting from inrushing temporary overvoltage and deterioration. In this paper, the authors made two prototype SPDs built-in Instantaneous trip device and analyzed their limiting voltage through test of the MOV breakdown. As the result of the analysis, the SPDs built-in Instantaneous trip device was proven to be effective for protecting MOV against thermal runaway and Instantaneous trip device react for limiting voltage is considered that is applicable to SPD.

• E2M - 전기 전자와 첨단 소재
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• 제9권7호
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• pp.719-726
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• 1996

DLTS measurements were performed to study the annealing induced changes of the trap centers in MOV and to shed more light on the stability mechanism of the MOV. Two electron traps, Ec-0.26[eV] and Ec-(O.2-0.3)[eV], were observed in the unannealed samples in large quantities(7-9 X 1014[CM 3]), whereas the three electron traps Ec-0.17 [eV], Ec-0.26[eV] and Ec-(O.2-0.3)[eV] were observed far less in the annealed samples. The minima in the Ec-0.26[eV] trap density, coupled with the presented results that unannealed devices are unstable whereas 600.deg. C annealed devices are most stable, suggests that the instability of the MOV under long term electrical stressing is related to the Ec-0.26[eV] trap. This results support that the ion migration model for the device instability where the Ec-0.26[eV] defects may be the interstitial zinc or the migrating ions. The interstitial zinc originated as a result of the nonstoichiometric nature of ZnO might cause the degradation of the I-V characteristics of the MOV with long term electrical stressing.

• 전기학회논문지
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• 제62권9호
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• pp.1302-1307
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• 2013

MOV(Metal Oxide Varistor) is the most important part of SPD(Surge Protective Device) which can protect electric facilities from an impulse current such as a lightning. So far, the fault of MOVs have decided only by surge count without considering magnitude of surge current and an amount of input energy. This paper proposed the fault prediction algorithm for the MOV using look up table made by surge count and input current data which have non-linear characteristics for input current and are estimated by high voltage experimental results. Proposed algorithm was proved by experiment on verification at a high voltage laboratory.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.644-651
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• 2001

The purpose of this study is to develop the improvement method of MOV(Motor Operated Valve) operability without major modification or change of MOV which needs a great expense and manpower. We studied valve stem lubrication, stem packing thrust and actuator control switch which could give an major effect to MOV operability, and found the some consequences. First, the stem/stem-nut friction coefficient and stem factor is significantly effected by stem lubrication state. Second, the measured packing thrust value is appeared higer than the design value for tested valves and the preparation of optimal value selection criteria is needed. Finally, optimization of MOV control switch is another major factor for MOV operability and structual integrity.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 D
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• pp.2778-2780
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• 2003

본 논문에서는 모터구동밸브의 모터 토크를 전기적인 신호만으로 예측하고, 계산된 모터 토크신호를 주파수영역에서 분석하여 Motor Speed, Slip pole 주파수, WGTM(Worm Gear Tooth Mesh)과 같은 MOV의 기계적 특성 성분을 확인하였다. 또한 모의 고장 실험을 통해 MOV 기계적 고장이 이 특성성분의 변화로 나타나는 것을 확인하므로, 이 정보를 MOV의 고장 감시 기술로 적용할 수 있다. 아울러 전기 신호를 이용하여 Condition Monitoring 기법을 개발하고, MOV 고장 감시 Software를 개발하므로, MOV 주기적 확인에 대비한 규제검증 기술 및 정보를 제공하고자 한다.

• 조명전기설비학회논문지
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• 제25권9호
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• pp.75-79
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• 2011

The MOV(Metal Oxide Varistor), a voltage limiting element, has been installed in the SPD(Surge Protective Device) or inside the internal circuit of an electronic appliance for protection of the electric power system and electronic device against electrical surge. Such an MOV is exposed, however, to the risk of the thermal runaway resulting from excessive voltage and deterioration. In this paper, a reciprocal action has been tested and analyzed using a phosphorus bronze switching module and the low-temperature solder. And a short current break characteristic test linked with the circuit breaker has been performed to limit the inrush current when the MOV breaks down. It has been proven that the phosphorus bronze switching module installed inside the internal circuit can improve the safety of the power line system and the electronic device.

• 한국안전학회지
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• 제17권2호
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• pp.92-99
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• 2002

Safety-related motor operated valve(MOV) safety significance for Ulchin Unit 3 was categorized. The safety evaluation of MOV of domestic nuclear power plants affects the generic data used for the quantification of MOV common cause failure(CCF) events in Ulchin Units 3&4 PSA. Therefore, in this paper, MGL(multiple greek letter)parameter ${\beta}$, used for the evaluation of MOV CCF probabilities in Ulchin Units 3&4 probabilistic safety assessment(PSA), was re-estimated and the MOV safety significance was categorized. The re-estimation results of MGL parameter show that the value of(is decreased by 30% compared with the current value used in Ulchin Unit 3&4 PSA. The categorization results of MOV safety significance using the changed value of MGL parameter(show that the number of HSSCs(high safety significant components) is decreased by 54.5% compared with those using the current value of it used in Ulchin Units 3&4 PSA.

• 조명전기설비학회논문지
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• 제24권1호
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• pp.71-77
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• 2010

뇌서지 보호는 오늘날 대부분의 전기전자기기에 있어 중요한 문제 중 하나이다. 그리고 뇌서지 보호를 위한 대다수 SPD의 가장 주요 부품으로 MOV가 사용된다. 본 논문에서는 다양한 타입의 MOV 기반 SPD를 조사하고 낮은 MLV특성의 부작용에 대하여 실험하였다. 실험결과로서 상대적으로 낮은 MLV특성은 실제 현장에서 발생 가능한 TOV 고장 상태하에서 더 큰 고장률로 나타날 수 있으며, 피보호기기보다 우선하여 소손될 수 있음을 알 수 있다. 결국 안전면에서 SPD는 높은 TOV내력과 신속한 단로기의 동작이 요구된다.

• 융합보안논문지
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• 제9권2호
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• pp.79-84
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• 2009

현재의 동영상 파일은 WMV(Window Media Video)형식과 같은 극일 포맷과 압축 기술들이다. 이 같은 파일 포맷과 압축 기술을 이용한 동영상들은 화질과 압축율에 문제점을 가지고 있다. 이에 본 논문은 Macromedia(Adobe 사가 인수함)사에서 개발한 FLV(Flash Video)와는 다른 FLY 솔루션 EZ-MOV를 설계 및 구현하였다. EZ-MOV는 다음과 같은 장점들을 가지고 있다. 첫째, FLV플레이어가 배속이 가능하며 자체 DRM이 내장 죄어 있어서 불법 녹화가 불가능하고 둘째, WMV 형식 파일을 FLV로 인코딩시에 최대한 50%까지 무손실로 압축이 가능하며 셋째, 버퍼링 없는 동영상 스트리밍이 가능하다. 넷째, 스트리밍 서버 없이도 FLV 파일을 스트리밍으로 서비스가 가능하다. 다섯째, 다운로드와 스트리밍을 병행한 동영상 서비스도 가능하다. 여섯째, 양방향으로의 서비스도 가능하다.

• 한국전기전자재료학회논문지
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• 제33권2호
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• pp.130-134
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• 2020

Metal oxide varistors (MOVs) protect circuits and devices from transient overvoltages in electric power systems. However, a MOV continuously deteriorates owing to manufacturing defects or repetitive protective operations from transient overvoltages. A deteriorated MOV may result in a short circuit or a line-ground accident. Previous studies focused on the analysis of deterioration mechanisms and condition diagnosis techniques for MOVs owing to their recent growth of use. An accelerated deterioration experiment under the same conditions in which a MOV operates is essential. In this study, we designed and fabricated a surge generator that can apply a surge current to a MOV connected to AC mains. The coupling network operates at a low impedance against the surge current from the surge generator and transfers the surge current to the MOV under test. It also acts as a high impedance against AC mains for the AC voltage not to be applied to the surge generator. The decoupling network operates at a high impedance against the surge current and blocks the surge current from AC mains. It also acts as a low impedance against AC mains for the AC voltage to be applied to the MOV under test. The prototype surge generator can apply the 8/20 us up to 15 kA on AC voltages in the approximate range of 110~450 V, and it fully operates on a LabVIEW-based program.