• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1994년도 하계학술대회 논문집 C
• /
• pp.1526-1529
• /
• 1994

In hydro-generator, a groundwall insulation of stator windings gradually deteriorates due to mechanical, thermal, electrical and environmental stresses. These stresses combine to result in loose windings, delamination of the stator insulation and/or electrical tracking of the end winding, all of which can lead to stator insulation failures. Conventionally, off-line tests such as partial discharge measurement, DC/AC current test and ${\Delta}tan{\delta}$ test has been used for estimation of winding condition. However, off-line test requires large power supply and generator outage. In addition, major cause of insulation problems such as loose wedges and slot discharges may not be found with off-line diagnoses. This paper describes the on-line partial discharge measurement techniques in the generator stator windings. The experimental results from the UIAM #1 hydro-generator confirms a optimistic application of on-line generator diagnosis method as a reliable tool for evaluation of winding condition.

• 조명전기설비학회논문지
• /
• 제25권11호
• /
• pp.73-82
• /
• 2011

The solid insulation system of stator windings in high voltage rotational machines is usually aging in accordance with long time operation. The partial discharge test have been known to check whether insulation deterioration exist or not, and the PD test can effectively diagnose a solid insulation condition regardless of during operation(on-line) or not(off-line). The on-line PD measurement have proven to be a successful technique in monitoring stator insulation condition nowadays. This paper describes the characteristics of comparing the on-line PD measurement data using PDMS-HG(Partial Discharge Monitoring System for Hydro-electric Generator) installed in field with the off-line diagnosis measurement data(insulation resistance, winding resistance, PI, ${\Delta}tan{\delta}$ and PD) on hydro generator(13[kV]) stator windings. These results make good use of managing rotational machines through evaluating the solid insulation condition of stator windings.

• 한국안전학회지
• /
• 제17권4호
• /
• pp.94-100
• /
• 2002

As the use of automatic handling equipment for sensitive semiconductor devices is rapidly increased, manufacturers of electronic components and equipments need to be more alert to the problem of electrostatic discharges(ESD). In order to analyze damage characteristics of semiconductor device damaged by ESD, this study adopts a new charged-device model(CDM), field-induced charged model(FCDM) simulator that is suitable for rapid, routine testing of semiconductor devices and provides a fast and inexpensive test that faithfully represents ESD hazards in plants. High voltage applied to the device under test is raised by the field of non-contacting electrodes in the FCDM simulator, which avoids premature device stressing and permits a faster test cycle. Discharge current and time are measured and calculated. The characteristics of electrostatic attenuation of domestic semiconductor devices are investigated to evaluate the ESD phenomena in the semiconductors. Also, the field charging mechanism, the device thresholds and failure modes are investigated and analyzed. The damaged devices obtained in the simulator are analyzed and evaluated by SEM. The results obtained in this paper can be used to prevent semiconductor devices form ESD hazards and be a foundation of research area and industry relevant to ESD phenomena.

• 한국전문물리치료학회지
• /
• 제14권3호
• /
• pp.81-89
• /
• 2007

The purpose of this study was to utilize the K-MBI (Korean Modified Barthel Index) and subscales of K-MBI in predicting the length of hospital stay (LOS) and the discharge destinations for stroke patients. The study population consisted of 97 stroke patients (57 men and 40 women) admitted to the Seoul National University at the Bundang Hospital. All participants were assessed by K-MBI at admission and discharge after rehabilitation therapy and the information available was investigated at admission. The data were analyzed by using the Mann-Whitney U test, the stepwise multiple regression and the logistic regression. The median LOS was 30 days (mean, 32.8 days; range, 22 to 43 days). The K-MBI score at initiation of rehabilitation therapy (p<.001), the type of stroke and living habits before a stroke were the main explanatory indicators for LOS (p<.05). Within the parameters of K-MBI measured at initiation for rehabilitation, feeding and chair/bed transfer were the explanatory factors for LOS prediction (p<.01). Confidence in the prediction of LOS was 20%. Significant predictors of discharge destination in a logistic regression model were the discharge K-MBI score, sex and hemiplegic side. Dressing in items of discharge K-MBI was the significant predictor of discharge destination. The K-MBI score was the most important factor to predict LOS and discharge destination. Knowledge of these predictors can contribute to more appropriate treatment and discharge planning.

• 한국해양환경ㆍ에너지학회지
• /
• 제15권4호
• /
• pp.281-291
• /
• 2012

MPUV와 Plasma를 사용하여 선박의 평형수를 처리하는 ARA Plasma BWTS가 개발되었으며, 이로부터 방류되는 배출수가 해양생태계 미치는 영향을 파악하기 위하여 Skeletonema costatum, Tigriopus japonicus 및 Paralichthys olivaceus를 이용하여 배출수독성시험과 생성된 화학물질에 대한 환경위해성을 평가하였다. 34 psu 배출수는 P. olivaceus에 대하여 미약한 만성 독성영향을 보였다($7d-LC_{50}{\Rightarrow}100.00%$ 배출수, $7d-LC_{25}{\Rightarrow}85.15%$ 배출수). 34 psu 배출수에서 Bromobenzene, chlorobenzene과 4-chlorotoluene이 해수의 배경농도보다 높게 검출되었다. MAMPEC을 이용한 Bromobenzene, chlorobenzene과 4-chlorotoluene의 PEC 산출결과는 각각 3.34E-03, 2.10E-03 및 1.73E-03 ${\mu}g\;L^{-1}$이었고, PNEC는 1.6, 0.5 및 1.9 ${\mu}g\;L^{-1}$였다. 세 화학물질의 PEC/PNEC 비율은 1을 초과하지 않았고, PBT 특성을 보이지 않았다. 따라서 WET test 결과와 환경위해성평가결과는 ARA Plasma BWTS에 의하여 처리된 해수가 해양생태계에 수용 불가한 영향을 미치지 않을 것임을 시사하였다.

• 한국분무공학회지
• /
• 제25권3호
• /
• pp.95-102
• /
• 2020

Six shear coaxial injectors for a 3 tonf-class liquid rocket engine using oxygen and methane as propellants were designed and manufactured by considering geometric design parameters such as a recess length and a taper angle. Cold-flow tests on the injectors were performed using water and air as simulants. By changing the water mass flow rate and air mass flow rate, the injection pressure drop under single-injection and bi-injection was measured. The discharge coefficients through the injector oxidizer-side and fuel-side were calculated and the discharge coefficient ratio between bi-injection and single-injection was obtained. Under single-injection, the recess served to reduce the injection pressure drop on the injector fuel-side. For the injectors without recess, the discharge coefficients under bi-injection were almost the same as those under single-injection. However, for the injectors with recess, the taper angle and bi-injection had a significant effect on the discharge coefficient.

• 정보학연구
• /
• 제7권4호
• /
• pp.61-69
• /
• 2004

본 논문에서는 6.6kV급 고압전동기 모델 코일을 4가지의 권선의 인공적인 결함을 갖도록 제작하였다. 운전중 모의를 위해 모델 코일에 80pF의 에폭시-마이카 커플러를 설치하였으며, TGA를 사용하여 NQN, 부분방전 크기 및 부분방전 패턴 등을 측정하였다. 웨이블렛 변환기법을 이용한 고압전동기의 고정자권선의 결함에서 발생된 부분방전신호의 파형을 통하여 여러 가지의 통계적인 파라메터를 통하여 특징을 추출하였다.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2007년도 춘계학술대회논문집
• /
• pp.633-640
• /
• 2007

In this paper, 3-D reciprocating compressor is taken into flow-structure interaction analysis. The full cycle process consisted of cylinder expansion and compression has been modeled without considering flow leakage through cylinder wall. Fully-coupled FSI analysis of this compressor model was iteratively solved and gives sufficient result with the experimental test. The study is emphasized to thoroughly investigate discharge valve motion, opening and closing, in order to determine discharge valve region which is prone to have high effective stress. The cylinder pressure is successfully validated before conducting impact analyses between discharge valve and other susceptible supported structure. Velocity profile has been obtained in FSI analysis is used as initial condition to carry out further impact analyses. Stress result of discharge valve and valve spring gives preliminary estimation of higher stress area due to its impact phenomena.

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제50권7호
• /
• pp.334-339
• /
• 2001

A silent type ozone generator using water surface has been studied and improved its ozone generation characteristics by the controlling the height of Taylor cone by installing a mesh electrode, a dielectric bed of glass beads in the just under th surface of the water. The current-voltage characteristics and characteristics of ozone generation quantity of the test system were investigated and discharge current oscillograms of the each cases of the mesh electrode and the beds were observed and compared each other to analyze the discharge conditions. The Taylor cone height could be the cause of the discharge bridge to decrease the ozone generation on the discharge spacing. In this study, the hight of Taylor cone could be reduced greatly by installing the mesh and the glass beads bed just under the water surface. Therefore a higher ozone generation also could be obtained.

• 한국농공학회지
• /
• 제28권1호
• /
• pp.51-59
• /
• 1986

Through the hydraulic model test, a more convenient and accurate method of deter- mining discharge coefficients in the sluice type of tide gates can be derived by the use of aubmergence ratio as a parameter. The results obtained are summarized as follows; 1. Discharge coefficients under submerged flow conditions can be obtained by the application of sutmergerice ratio (S) to the free flow equation of the broad-erested we r. 2. The critical submergence ratios (Scr) for the flat basin and the broad-crested types of sill have the same value of 0.8. 3. Under free flow conditions, the discharge coefficient (m) are 0.37 and 0. 35 for the flat basin and the broad-crested types of sill respectively. However, when submerged flow condition exists, the discharge coefficients for both types of sill is given by a regression equation of discharge coefficients (IL) on submergence ratios (8) expressed as; m 1.3- 1. 17S. 4. The relationships between S and Froude number (Fr), for the flat basin and the broad-crested types of sill are Fr=2. 79-2.495 and Fr2.5=5. 7-6.16S respectively. From the above relationships, it can be concluded that m can also be expressed in terms of the Froude number which is a very relevant hydraulic parameter of the open channel hydraulics.