• Proceedings of the KIEE Conference
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• 1999.07f
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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.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.3 no.3
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• pp.11-16
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• 2004

In this study, the characteristics of signals such as acoustic emission, vibration amplitude and noise level which are derived from the abnormal condition of compressor are investigated. The normal condition, vane stick sound and roller defect condition are chosen to analyze the signal in each cases. From the feature extraction of each signals, the dominant parameters of each signals which can identify the abnormal condition are suggested.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.1
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• pp.43-47
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• 2016

This system is a diagnosis system that checks whether it causes a partial discharge of a power cable or not. It is to classify normal from abnormal-normal, PD (Partial Discharge) sound through analysis of RLCR (Relative Level Crossing Rate) and spectrogram energy algorithm. Partial discharge diagnostic system has a function that stores PD sound and analyzes the data. The wave shape of PD sound is similar to noise and is systematically generated by partial discharge. Therefore, in this paper, we could discreminate between normal and abnormal case using relative level crossing rate (RLCR) and spectrogram of frequency energy rate.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.05a
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• pp.360-364
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• 2004

The objective of this study is to estimate the feasibility of acoustic emission method Jar the internal leak from the valves in nuclear power plants. The acoustic emission method was applied to the valves at the site, and the background noise was measured for the abnormal plant condition. From the comparison of background noise data with the experimental results as to relation between leak flow and acoustic signal, the minimum leak flow rates that am be detected by acoustic signal was suggested. When the background noise level are higher than the acoustic signal, the method described below was considered that the analysis the remainder among the background noise frequency spectrum and the acoustic signal spectrum.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.463-468
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• 2007

The abnormal sound of generator frame is analyzed by a acceleration signal. The spike-like time signal is major characteristics of impacting force. The distributional map of vibration level is one of visualization method. With map, noise source was easily detected. After de_assembly of generator, loose part of internal component is the source of impact force by mechanical movement of stator inherently. In contact condition of part with clearance, the level of impact signal is different at each revolution and impact signal did not happens periodically.

• The Journal of the Acoustical Society of Korea
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• v.38 no.3
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• pp.363-369
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• 2019

Various studies have been conducted for the diagnosis of noise condition of complex rotary machines. In this study, diagnosis index using vibration signal is developed for the efficient and objective assessment of noise condition of a blower motor. The noise most commonly caused by the abnormal blower motor are Tick/Click noise and Tone noise. According to cause and noise characteristics, time-frequency analysis is used to diagnose Tick/Click noise, and smoothing in frequency domain is used to diagnose tone noise condition. The noise condition of the blower motors were diagnosed using the developed index and these results are compared with the diagnostic results by the experts. As a result, the agreement rate was about 95 %.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1994.04a
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• pp.122-127
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• 1994

본 논문에서는 산업용으로서 널리 이용되고 있는 3상 유도전동기의 전기적결함에 의해 발생하는 전자진동문제를 체계적으로 검토하고, 이를 이용하여 전동기 진동이 진단법을 신경회로망을 이용하여 구축한다. 그리고 그중에서 비교적 자주 발생하는 공극(air-gap)의 정적편심에 대해 실험을 수행하고, 그 결과를 신경회로망을 이용한 진단법에 적용하여 본 진단법의 유용성을 확인한다. 또한 현장에서 발생된 전기적인 결함에 대한 진동측정 data를 이용하여 진단이 정상적으로 수행되는가를 조사하여 본 진단법의 가능성을 조사한다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.04a
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• pp.360-366
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• 1995

국내 발전소에서 사용하고 있는 대형 회전 기계인 터빈의 상태 진단 기능을 높이기 위하여 터빈에서 발생 될 수 있는 이상 진동의 특성을 파악하고 이를 이용하여 이상 진동의 발생 가능성을 확률적으로 출력하는 새로운 알고리즘을 개발하였으며, C-언어로 프로그램하여 이를 검증하였다. 이상과 같이 본 연구에서 제안한 알고리즘을 이용한 자동 진단 시스템을 통하여 각각의 이상 진동에 대한 진단을 수행한 결과 양호한 판정 결과를 보였으며, 터빈 이상 진동에 대한 자동 진단의 가능성을 입증하였다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.1015-1019
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• 2001

There are several bearing systems at the large steam-turbines in thermal power plant. The bearing system is one of the most important parts of rotating machinery. The steam turbine vibrations mainly depend on the bearing oil and the shaft alignment condition. This paper describes on the steam turbine abnormal vibration due to the oil whip in terms of the shaft alignment in the thermal power plant.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.7 s.112
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• pp.697-703
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• 2006

This article proposes a new technique for the reduction of vibration and noise in the geared system by adjusting the distance between gear shafts. The vibration and noise may be produced by the abnormal force applied to the tooth face. And the force may be the cause of ununiform velocity in the driven shaft. If the velocity is obtained to be uniform by adjusting the distance between shafts. the vibration and noise may be reduced to some extent. In order to review, a dynamic analysis model for the gear train used in a mill turret and a test rig are developed. The velocities in the driven shaft are calculated by dynamic simulations for the model and noises in the test rig are measured with varying of the distance between shafts. The comparison of simulation and test data shows that the distance between shafts at the most uniform velocity has the lowest level of noise.