• International Journal of Control, Automation, and Systems
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• 제6권5호
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• pp.670-676
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• 2008

While the matrix converter has many advantages that include bi-directional power flow, a size reduction, a long lifetime, and sinusoidal input currents, it is vulnerable to the input voltage disturbances, because it directly exchanges the input voltage to the output voltage. So, in this paper, a critical evaluation of the effect of various abnormal voltage conditions like unbalanced power supply, balanced non-sinusoidal power supply, input voltage sags and short time blackout of power supply on matrix converter fed induction motor drives is presented. The operation under various abnormal conditions has been analyzed. For this, a 230V, 250VA three phase to three phase matrix converter (MC) fed induction motor drive prototype is implemented using DSP based controller and tests have been carried out to evaluate and improve the stability of system under typical abnormal conditions. Digital storage oscilloscope & power quality analyzer are used for experimental observations.

• Journal of Information Processing Systems
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• 제15권6호
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• pp.1392-1405
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• 2019

The cathode voltage of aluminum electrolytic cell is relatively stable under normal conditions and fluctuates greatly when it has an anomaly. In order to detect the abnormal range of cathode voltage, an anomaly detection algorithm based on sliding window was proposed. The algorithm combines the time series segmentation linear representation method and the k-nearest neighbor local anomaly detection algorithm, which is more efficient than the direct detection of the original sequence. The algorithm first segments the cathode voltage time series, then calculates the length, the slope, and the mean of each line segment pattern, and maps them into a set of spatial objects. And then the local anomaly detection algorithm is used to detect abnormal patterns according to the local anomaly factor and the pattern length. The experimental results showed that the algorithm can effectively detect the abnormal range of cathode voltage.

• 대한전기학회논문지
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• 제35권2호
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• pp.55-61
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• 1986

This paper describes the generation region and suppression effect of the abnormal field voltage induced when the synchronous generator is switched to the infinite bus, the critical value of negative field current is calculated by simmulation which has parameters of the phase difference and voltatge ratio between the bus and the generator. The suppression effect of discharge resistance connected in parallel with the field circuit is also investigated. According to this study, the optimal value of discharge resistance which can suppress effectively the abnormal field voltage may be calculated.

• Journal of Preventive Medicine and Public Health
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• 제31권2호
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• pp.183-198
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• 1998

In order to determine the prevalence rate and find out the sexual difference of abnormal electrocardiographic findings manifested by computerized EKG, which is equipped with auto-analyzing function, a total of 2,083 electrocardiograms that were taken from population over 20 years-old from October 1996 to February 1997 were studied according to their age, gender and blood pressure. 1. Using the electrocardiography with auto-analyzing function, 33 kinds of abnormal findings were manifested. The prevalence rate of abnormal findings was 52.8% in male and 43.7% in female. Among them, the most common finding was sinus brady-cardia found in 17.6% of male and 15.4% of female. Left ventricular hypertrophy by voltage criteria, minimal voltage of left ventricular hypertrophy, left axis deviation and atrial fibrillation were more common in male than in female statistically. Both of nospecific T wave and ST segment abnormality were more common in female than in male statistically. 2. Thirty-three kinds of abnormal findings were manifested. They revealed one abnormal finding alone or combined with some other ones making 128 kinds of abnormal finding. The most common abnormal finiding that manifested alone was right axis deviation (100%), then myocardial ischemia (95.7%) the next. The most common abnormal finding that complexed with other abnormal findings were left anterior fascicular block(percentage of single manifestation, 26.2%) and nonspecific T wave abnormality(percentage of single manifestation; 32.9%). Also, combination of sinus bradycardia and minimal voltage of left ventricular hypertrophy, and combination of sinus bradycardia and left ventricular hypertrophy were included in 25th sequences of abnormal findings. 3. The prevalence rate of abnormal electrocardiographic findings were higher in older group, hypertensive group, and the group of higher systolic or diastolic pressure in both sexes. 4. Abnormal findings that commonly manifested with sinus bradycardia were voltage criteria or minimal voltage of left ventricular hypertrophy(38.6%): sinus arrhythmia(10.5%): nonspecific T wave or ST segment abnormality(18.4%) and first degree AV block(7.2%) in descending order. 5. The most common site which manifested myocardial ischemia was posterior and inferior wall with equal percentage of 23.4%. And then anterior wall(19.1%), and antero-lateral wall and septum with equal percentage of 10.6% was noted in descending order.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 추계학술대회 논문집
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• pp.10-13
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• 2008

Fuel cell systems have witnessed remarkable development in recent years as they offer a clean and efficient alternative for power generation. Testing was conducted to determine the safety performance of a residential fuel cell system when subjected to abnormal operation condition, especially for voltage sag and fuel cut. In case of voltage sag to 198V, its arriving time at rated power had shown a slight lag but there wasn't any noticeable change when operating it between rated voltage(220V) and 10% voltage sag(198V). In case of fuel cut, it also showed stable shut-down characteristics. The test results are being used to develop a new safety evaluation for residential fuel cell system.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2009년도 정기총회 및 추계학술대회 논문집
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• pp.287-289
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• 2009

This paper deals with a parallel processing uninterruptible power supply (UPS) for sudden voltage fluctuation in computer applications to integrate power quality improvement, load voltage stabilization and UPS. To reduce the complexity, cost and number of power conversions, which results in higher efficiency, only one voltage-controlled voltage source inverter (VCVSI) is used. The system provides sinusoidal voltage at the fundamental value of 220V/60Hz for the load during abnormal utility power conditions or grid failure. Also, the system can be operated to mitigate the harmonic current and voltage demand from nonlinear loads and provide voltage stabilization for loads when sudden voltage fluctuation occur, such as sag and swell. System operation simulation demonstrates that the system protects against outages caused by abnormal utility power conditions and sudden voltage fluctuations and changes.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 F
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• pp.2674-2677
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• 1999

Resonant converters have several salient features such as high efficiency and low noise. Therefore, ZVS-PWM controlled series resonant converter with active-clamp technique is presented. The combination of an active-clamp technique and resonant circuit makes it possible to control the output voltage of the resonant converter with PWM. This new resonant converter was implemented and has achieved a good controllability. In this paper, the normal load characteristics and abnormal voltage increase in the case of the light load are analyzed. As a result, it is clarified that the stray capacitance of the transformer is a cause of the abnormal voltage increase. Then, it is confirmed that the abnormal voltage increase is suppressed by decreasing the duty ratio. ZVS condition is analyzed. The maximum efficiency of 89% is obtained for the output of 10V and 5A.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1161-1162
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• 2007

In year 2004 korea runs high speed train KTX for the 5th time in the world. And now the traction power system is quite stabilized. But still a lot of work to develop and abnormal voltage problem is one of them. In this paper, by actual measuring we have collected the abnormal data on the high speed train sub-staion for more than 15 days. The collected data has been evaluated. In the near future collected data will be used planing a countermeasure.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 전력전자학술대회 논문집
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• pp.314-318
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• 1998

This paper discusses the development of electronic ballast for neon lamp as an application of a zero voltage switching high frequency inverter. Abnormal increase of secondary voltage due to grounded fault or partial damage of serial arranged loads is clarified and the protection circuit for this abnormal voltage increase is proposed. Also stable lighting condition for removing the unstable characteristics due to different load conditions is proposed.

• 한국화재소방학회논문지
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• 제28권3호
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• pp.87-91
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• 2014

본 논문은 선풍기 모터의 회전을 정상 및 고정상태로 구분하여 주권선에서의 전압 및 전류, 모터 전체의 온도특성을 분석하여 전기화재 위험성을 제시하는 것을 목표로 하고 있다. 전압과 전류 신호에 대하여, 전압의 경우 정상상태와 고정상태에 대하여 큰 차이점은 없었으며, 전류의 경우는 비정상상태(최대 203 mA)보다 정상상태(최대 309 mA)가 상당히 높았다. 온도신호의 경우, 모터 전반에 있어서 온도 분포도가 다르게 나타났으며, 정상상태의 경우는 $4^{\circ}C$, 고정상태는 $18^{\circ}C$ 차를 보였다. 특히 대부분의 선풍기의 전기배선이 모터의 고정자철심에 부착되어 있었으며 해당전선의 허용온도가 $60^{\circ}C$를 감안했을 때에 절연열화가 가속될 수 있다. 또한 본 데이터는 선풍기 안전장치개발의 기초자료나 전기화재에 대한 조사 자료로 활용할 수 있다.