• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.1
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• pp.94-101
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• 1999

In this paper the problems associated with the switching surge of PWM inverter devices were analysed. As the application of ASD for efficient speed control of AC rmtors is increased, so is the rrntor and ASD-related failure increased. In the industrial rmtor awlications, the introduction of PWM drives can sometmes cause insulation breakdown between the phase windings due to high transient voltage peak. The motor cable length combined with the high switching frequency becomes more sensitive issue for proper drive operation. Effects of the cable length and high switching frequency influence both on rmtor and inverter. When the insulation level of rmtor winding is low, the failure probability caused by high peak voltage and fast voltage rise times(dv/dt) is high. Voltage refloctions are simulated far rmtor capacities, ASD and rise times and are presented graphically. The filtering techniques are discussed to reduce the rmtor terminal overvoltage and dv/dt in inverter fed AC rrntor drive systems. We confirmed that the lower motar capacity and rmtar insulation level, the shorter switching time and cable length and the higrer the probability of insulation breakdown .kdown .

• Ocean Systems Engineering
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• v.10 no.2
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• pp.131-161
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• 2020

The objective of this study was to evaluate the downtime cost of side-by-side offloading operations in Malaysian waters. With the help of a numerical time domain tool, the structure and cable response of moored FPSO vessel was simulated for heading and beam sea-states under irregular waves. The weather downtime was assessed by comparing the response under operational wave condition with the pre defined industrial safe offloading criteria. Additionally, two cases of cable failure were simulated for each sea-state. The novel study on downtime cost was presented for three different location of Malaysia subcontinent for which the location specific wave scatter diagram facilitated to estimate the probability of occurrence of operational wave condition. It was concluded that an unpredictable increment in wave height by 0.5 m can significantly impact the production cost.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2010.10a
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• pp.216-223
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• 2010

원자력발전소의 방화지역에서 화재가 발생할 경우 케이블의 화재리스크는 온도, 열속, 화염 등 열적 특성에 의해 평가된다. 원전의 안전정지 기능에 사용되는 각종 케이블은 설계관리 및 성능분석을 위해 화재실증실험으로 열적 특성을 실측하여야 하지만 다양한 화재시나리오에 대한 실험 조건 확보와 실험 비용 등 제약이 따른다. 이에 따라 화재모델 FDS (Fire Dynamics Simulator)의 최신버전에 포함된 THIEF (Thermally-Induced Electrical Failure) 모델을 이용하여 국내 원전의 안전정지 케이블에 대한 화재모델링 분석을 수행하였다. 이 연구에서는 케이블이 설치된 형태에 따라 일정 열속에 대한 자켓 온도와 경계조건에 대한 온도분포를 분석하였다. 본 연구 결과 THIEF 모델은 원전 방화지역의 화재에서 안전정지 케이블의 내부온도를 예측할 수 있는 화재모델로 사용가능한 것으로 확인되었다.

• Journal of Aerospace System Engineering
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• v.15 no.2
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• pp.45-51
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• 2021

In this study, we aim to eliminate the flickering phenomenon in multi-function display (MFD) units during the flight of fixed-wing aircraft. To execute flight missions effectively, the video signals transmitted to MFDs must provide information accurately and seamlessly. Therefore, a method for addressing the flickering phenomenon-including cause analysis and failure diagnosis-is adopted; specifically, a wiring configuration with a direct connection between the video signal cables and with a short cable length is adopted. The proposed method is experimentally verified using a flight test.

• Steel and Composite Structures
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• v.18 no.4
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• pp.811-831
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• 2015

This paper focuses on the strengthening methods used for improving the compression behaviors of perforated box-section walls as provided in the anchorage zones of steel pylons. Rectangular plates containing double-row continuous elliptical holes are investigated by employing the boundary condition of simple supporting on four edges in the out-of-plane direction of plate. Two types of strengthening stiffeners, named flat stiffener (FS) and longitudinal stiffener (LS), are considered. Uniaxial compression tests are first conducted for 18 specimens, of which 5 are unstrengthened plates and 13 are strengthened plates. The mechanical behaviors such as stress concentration, out-of-plane deformation, failure pattern, and elasto-plastic ultimate strength are experimentally investigated. Finite element (FE) models are also developed to predict the ultimate strengths of plates with various dimensions. The results of FE analysis are validated by test data. The influences of non-dimensional parameters including plate aspect ratio, hole spacing, hole width, stiffener slenderness ratio, as well as stiffener thickness on the ultimate strengths are illustrated on the basis of numerous parametric studies. Comparison of strengthening efficiency shows that the continuous longitudinal stiffener is the best strengthening method for such perforated plates. The simplified formulas used for estimating the compression strengths of strengthened plates are finally proposed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.6
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• pp.60-71
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• 2014

Cable-stayed bridge, which is one of the representative long-spanned bridge, needs prompt maintenances when a stay cable is damaged because it may cause structural failure of the entire bridge. Many researches are being conducted to develop abnormal behavior detection algorithms for the purpose of shortening the reaction time after the occurrence of structural damage. To improve the accuracy of the damage detection algorithm, ample observation data from various kinds of damage responses is needed. However, it is difficult to measure an abnormal response by damaging an existing bridge, numerical simulation can be an effective alternative. In most previous studies, which simulate the damage responses of a cable-stayed bridge, the damages has been considered as a load variation without regard to its stiffness variation. The analyses of using these simplification could not calculate exact responses of damaged structure, though it may reserve a sufficient accuracy for the purpose of bridge design. This study suggests Gradual Bilinear Method (GBM) which simulate the damage responses of cable-stayed bridge considering the stiffness and mass variation, and develops an analysis program. The developed program is verified from the responses of a simple model. The responses of a existing cable-stayed bridge model are analyzed with respect to the fracture delay time and damage ratio. The results of this study can be used to develop and verify the highly accurate abnormal behavior detection algorithm for safety management of architecture/large structures.

• Ocean Systems Engineering
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• v.9 no.3
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• pp.219-240
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• 2019

This paper presents the comparison between SFT response with linear and nonlinear cables. The dynamic response analysis of submerged floating tunnel (SFT) is presented computationally with linear and nonlinear tension legs cables. The analysis is performed computationally for two wave directions one at 90 degrees (perpendicular) to tunnel and other at 45 degrees to the tunnel. The tension legs or cables are assumed as linear and non- linear and the analysis is also performed by assuming one tension leg or cable is failed. The Response Amplitude Operators (RAO's) are computed for first order waves, second order waves for both failure and non-failure case of cables. For first order waves- the SFT response is higher for sway and heave degree of freedom with nonlinear cables as compared with linear cables. For second order waves the SFT response in sway degree of freedom is bit higher response with linear cables as compared with nonlinear cables and the SFT in heave degree of freedom has higher response at low time periods with nonlinear cables as compared with linear cables. For irregular waves the power spectral densities (PSD's) has been computed for sway and heave degrees of freedom, at $45^0$ wave direction PSD's are higher with linear cables as compared with nonlinear cables and at $90^0$ wave direction the PSD's are higher with non-linear cables. The mooring force responses are also computed in y and z directions for linear and nonlinear cables.

• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.3
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• pp.183-191
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• 2003

A four-story reinforced concrete moment resisting frame damaged from an ultimate limit state earthquake is upgraded with prestressing cable bracing. The purpose of this study is to investigate the bracing configuration effects on the 3-D building response using thee different locations of the bracing systems for the retrofitted building. Since the previous work done by the author proved that static incremental loads to collapse analysis as a substitute to dynamic non-linear time history analysis was a valid alternative tool. Thus, static load to collapse analysis is solely applied to evaluate the seismic performance parameters of both the original and upgraded buildings in this study. In results, the exterior bracing system is effective in restraining torsional behavior of the structure under seismic loads, and no sudden failure occurs in this system that enhances the ductility of the building due to the gradual change of building stiffness as the lateral load increases.

• Tribology and Lubricants
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• v.26 no.5
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• pp.277-282
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• 2010

The purpose of this paper is to study and analysis the failure examples for parasitic current leakage produced in starting system on gasoline engine. It verified the discharge of battery by electric leakage because of internal wiring damage problem for CD auto changer installed in car. Also, it verified the no-stating phenomenon because of deposit forming by chemical reaction of battery fluid between battery post and cable fixing parts. It verified the damage for brush holder and commutator mixing by internal short phenomenon because of brush carbon a particle and engine oil that was flowed into internal of starting motor. It verified the working phenomenon of audio by a point of contact even if the driver turn to "LOCK" position the key.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.1
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• pp.1-5
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• 2020

In this study, the objective is to improve the criteria used for statistical comparison of the VLF tanδ (TD) database and failure rate according to water-tree degradation in underground distribution power cables. The aging condition of the KEPCO criteria is divided into 6 levels using the Weibull distribution, and the "failure imminent" condition is quantified by using the statistical end-point of the lifetime parameter of the VLF big-data group obtained from KEPCO. Moreover, new criteria with a 2-dimensional combination of TD, DTD, and a statistical normalized factor are suggested. These criteria exhibit high reproducibility for the detection of cables in an imminent failure state. Consequently, it is expected that the adoption of the extended VLF-2019 criteria will reduce the asset management cost of cable replacement compared to the VLF-2012 criteria of KEPCO.