• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.5
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• pp.372-377
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• 2007

This paper proposes a novel fault diagnosis method of a electrolytic capacitor used for DC-link voltage smoothing in adjustable speed drives. The equivalent series resistance (ESR) of the electrolytic capacitor is directly estimated from DC-link voltage and load currents and the status of the electrolytic capacitor is determined from the estimated ESR. To compensate the variation of the ESR owing to temperature variation, diodes are located on the same PCB near the capacitor and the temperature of the capacitor is sensed indirectly from the voltage drop of diodes. Simulation and experimental studies show the effectiveness of the proposed method.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2022.06a
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• pp.1305-1307
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• 2022

자동차 부품의 결함은 시스템 전체의 성능 저하 및 인적 물적 손실이 발생할 수 있으므로 생산라인에서의 불량 검출은 매우 중요하다. 따라서 정확하고 균일한 결과의 불량 검출을 위해 딥러닝 기반의 고장 진단 시스템이 다양하게 연구되고 있다. 하지만 제조현장에서는 정상 샘플보다 비정상 샘플의 발생 빈도가 현저히 낮다. 이는 학습 데이터의 클래스 불균형 문제로 이어지게 되고, 이러한 불균형 문제는 고장을 판별하는 분류 모델의 성능에 영향을 끼치게 된다. 이에 본 연구에서는 모터의 동작음으로부터 불량 모터를 판별하는 불량 검출 시스템 설계를 위한 데이터 불균형 해결 방법을 제안한다. 자동차 사이드 미러 모터의 동작음을 학습 및 테스트를 위한 데이터 셋으로 사용하였으며 손실함수 계산 시 학습 데이터 셋의 클래스별 샘플 수 가 반영되는 label-distribution-aware margin(LDAM) loss 와 Inception, ResNet, DenseNet 신경망 모델의 비교 분석을 통해 불균형 데이터를 처리할 수 있는 가능성을 보여주었다.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.2
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• pp.56-66
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• 2016

Robustness is essential for model based FDI (Fault Detection and Isolation) and it is inevitable to have modeling errors and sensor signal noises during the process of FDI. This study suggests an improved method by applying NARX (Nonlinear Auto Regressive eXogenous) model and Kalman estimator in order to cope with problems caused by linear model errors and sensor signal noises in the process of fault diagnoses. Fault decision is made by the probability of the trend of gradually accumulated errors applying Fuzzy logic, which are robust to instantaneous sensor signal noises. Reliability of fault diagnosis is verified under various fault simulations.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.266-266
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• 2009

This paper describes important parameters used to evaluate the insulation performance of power supply components in metro substations. For online fault diagnosis of power supply components, we have developed a new remote condition monitoring system using wireless technology. Our developed system can continuously monitor electric power equipment such as transformers, circuit brakers, and rectifiers and have powerful wireless networking functions.

• Transactions of the Korean hydrogen and new energy society
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• v.28 no.3
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• pp.252-272
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• 2017

Fuel cell systems have to satisfy acceptable operating reliability, sufficient lifetime and price to enter the market in competition with existing products. Fuel cells are made up of complex element technologies and various problems related to the failure of the components can affect the reliability and safety of the system. This problem can be overcome by introducing a monitoring and supervisory control system in addition to automatic control to detect the failure of the fuel cell quickly and properly diagnose the performance degradation. For the fault detection and diagnosis of polymer electrolyte fuel cells, the model based method using the theoretical superposition value and the non-model based method of checking the signal tendency or the converted signal characteristic can be applied. The methods analyzed in this paper can contribute to the development of integrated monitoring and control technology for the whole system as well as the stack.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.2087-2088
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• 2011

배전선로 정전고장 예방활동으로 순시/점검은 전력회사 기준에 따라 매년 시행하고 있다. 전력공급 장애 요소를 사전에 제거하거나 불량 기자재를 적출하여 정전을 예방하고 있다. 매년 수 천 건의 설비 불량개소를 개선하여 전력공급 품질 목표를 유지하고 있다. 설비가 방대하고 복잡, 다양해져 시간과 비용이 많이 소요되는 인력점검 보다 진단 장비 사용이 증가하고 있다. 설비운영방법에 있어서도 경년에 따른 교체보다 설비 노후도를 평가하여 교체하도록 하고 있어, 현장에서 설비의 상태 판단이 중요하다. 따라서 제한된 자원으로 최대의 효과를 얻기 위해 과학적인 장비를 이용한 진단방법이 도입되었으며, 본 연구에서는 국내 가공 배전선로 진단에 사용하고 있는 비접촉식 진단장비의 현장 적용시 검출특성과 상태 판정시 고려해야할 기술적 사항에 대한 결과 얻을 수 있었다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.11
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• pp.705-710
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• 2011

Fault detection has to be proceeded by steady state filtering to get rid of transient effect associated with thermal capacity. Coefficient of variance (COV), ratio of standard deviation devided by moving average, was employed as steady-state filter. Engine speed and refrigerant pressures were selected as parameters representing system dynamics. The filtered values were registered as members of steady-state DB. They were found to show good functional relationship with ambient temperature. The relationship was fitted with a second order polynomial and the distribution bounds of the data around the fitted curve were expressed by visual inspection because of varying average and random data interval. Fault data were compared with the steady-state data obtained during normal operation. The fault data were easily isolated from the fault-free one. To make such isolation reliable, tests to construct good DB should be designed in a systematic way.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.11
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• pp.587-595
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• 2015

In this study, fault symptoms were simulated and analyzed for a single-effect absorption chiller. The fault patterns of fault detection parameters were tabulated using the fault symptom simulation results. Fault detection and diagnosis by a process history-based method were performed for the in-situ experiment of a single-effect absorption chiller. Simulated fault modes for the in-situ experimental study are the decreases in cooling water and chilled water mass flow rates. Five no-fault reference models for fault detection of a single-effect absorption chiller were developed using fault-free steady-state data. A sensitivity analysis of fault detection using the normalized distance method was carried out with respect to fault progress. When mass flow rates of the cooling and chilled water decrease by more than 19.3% and 17.8%, respectively, the fault can be detected using the normalized distance method, and COP reductions are 6.8% and 4.7%, respectively, compared with normal operation performance. The pattern recognition method for fault diagnosis of a single-effect absorption chiller was found to indicate each failure mode accurately.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.7
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• pp.508-516
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• 2008

Fault detection and diagnosis(FDD) system is beneficial in equipment management by providing the operator with tools which can help find out a failure of the system. An experimental study has been performed on fault detection and diagnosis method for a water chiller. Bayes classifier, which is one of classical pattern classifiers, is adopted in deciding whether fault occurred or not. Failure modes in this study include refrigerant leakage, decrease in mass flow rate of the chilled water and cooling water, and sensor error of the cooling water inlet temperature. It is possible to detect and diagnose faults in this study by adopting FDD algorithm using only four parameters(compressor outlet temperature, chilled water inlet temperature, cooling water outlet temperature and compressor power consumption). Refrigerant leakage failure is detected at 20% of refrigerant leakage. When mass flow rate of the chilled and cooling water decrease more than 8% or 12%, FDD algorithm can detect the faults. The deviation of temperature sensor over $0.6^{\circ}C$ can be detected as fault.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.7 s.337
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• pp.37-44
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• 2005

This paper presents effective test patterns and their BIST implementations for SoC and Board interconnects. Initially '6n'algorithm, where 'n' is the total number of interconnect nets, is introduced to completely detect and diagnose both static and crosstalk faults. Then, more economic 4n+1 algorithm is described to perfectly capture the crosstalk faults for the interconnect nets separated within a certain distance. It will be shown that both algorithms can be easily implemented as interconnect BIST hardwares with small area penalty than conventional LFSR.