• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.110-115
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• 2014

The nuclear power plant was launched by Kori unit 1 in 1978 years. Currently, 23 nuclear power plants have been operating in Korea since 1978 years. The localization was completed for most of the reactor facility from Hanbit(Youngkwang) unit 3&4. However, RCP(Reactor Coolant Pump) and MMIS(Man Machine Interface System) is an important technology that has been excluded from the scope of the technical transfer has been dependent on a specific overseas vendor. Recent success in RCP development through co-operation with government and industries. Developed RCP will be applied to Shin-Hanul unit 1&2 nuclear power plants. The RCP operates in high speed and high pressure condition and only rotating component in the NSSS(Nuclear Steam Supply System). Therefore, the problem of vibration has arisen caused by the hydraulic forces of the working fluid. These forces can influence on the stability characteristics for entire RCS(Reactor Coolant System) loop, and can act as significant destabilizing forces. In this study, vibration evaluation of the pump shaft of development RCP estimated under normal operation and over speed conditions. In order to predict the vibration characteristics and dynamic behavior, modal analysis, critical speed analysis and unbalance response spectrum analysis were performed.

• 조명전기설비학회논문지
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• 제29권12호
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• pp.83-87
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• 2015

This paper presents a simple notch filter, which is so suitable for three-phase unbalanced and distorted power line. In the d-q synchronous transformation, three-phase unbalanced and distorted voltages generate lots of ripple voltages on d-q axes. The ripples make disturbances on controllers such as PLL of phase tracking. Unbalanced state makes ripple of double the frequency of power line. Odd harmonics 5th and 7th on the line make even 4th and 6th ripples on d-q axes due to the rotating reference frame, respectively. Cascaded two comb filters, delay lines 1/4T and 1/8T, are adopted for the ripple rejection. The filter rejects harmonics 2nd, 4th, 6th, 10th and so on. They are very effective to remove the ripples of both unbalance and distortion. The filter, implemented by two FIFOs on an experimental system, is adopted on a PLL controller of power line phase tracking. Through the simulation and experimental results, performance of the proposed comb filter has been validated.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제48권12호
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• pp.691-700
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• 1999

This paper proposes a novel switching strategy of 1Mvar STATCON using cascade multilevel H-bridge inverter(HBI) for FACTS application. To control the reactive power instantaneously, the d-q dynamic system model is described and analyzed. A single pulse pattern based on the SHEM(Selective Harmonic Elimination Method) technique is determined from the look-up table to reduce the line current harmonics and a rotating fundamental frequency switching scheme is presented to adjust the DC voltage of each inverter capacitor at the same value. So the voltage unbalance problem between separately DC bus voltage is improved by using the proposed switching scheme. As a result, the presented inverter configuration not only reduces the system complexity by eliminating the isolation at the AC input side transformer but also improves the dynamic response to the step change of reactive power.

• Journal of Mechanical Science and Technology
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• 제20권10호
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• pp.1653-1661
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• 2006

AC induction motors have been widely used for fan motor of the air conditioner indoor unit. Noise of these AC induction motors is usually caused by the coupling effects of structural and electrical systems. The rotating torque and the noise from AC induction motor were discussed in this paper,. First, the modification of motor was carried out in order to reduce the unbalance magneto motive force between main and sub winding. Second, structural modification based on normal mode analysis and modal testing was carried out so that the fan motor does not have the natural frequencies near the 2f-line frequency. Numerical modifications through these two processes were verified by experiments, which showed that the sound pressure level at 2f-line frequency of the modified system became about 25dB less than that of conventional one.

• 플랜트 저널
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• 제4권4호
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• pp.56-61
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• 2008

The phenomena of oil whip in steam turbines take place for the unbalance force between a rotor shaft and bearing oil film. The several parameters that affect onset of oil whip have been well known. However, the major parameter of oil whip is shaft mis-alinement. A oil whip causes the high vibration and the shutdown of rotor system. We mostly stop the steam turbine to adjust a shaft re-alinement concerning oil whip. In this case, it needs many costs for maintenance and long shutdown times. In this study, we study and observe the oil whip of the 300MW steam turbine in many years and we conduct the field test for another steam turbine for reducing vibration from oil whip. The results of this study are that a oil whip takes place with a particular rotating speed or a particular turbine output and the oil temperature change is a very effective method for on-line oil whip treatment.

• 한국자동차공학회논문집
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• 제17권2호
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• pp.150-158
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• 2009

A centrifugal turbo blower is one of the part to generate electric power of fuel cell electric vehicle(FCEV). In order to generate the electric power of FCEV, the centrifugal turbo blower operates at very high speed above 30,000rpm in order to increase the pressure of the air, which supplied to a stack of FCEV, using rotation of its impeller blades. Vibration which originated from the blower is generated by unbalance of mechanical components, rotation of bearings and rotating asymmetry that rotate at high speed. The vibration is transmitted to receiving structure through vibration isolators and it can causes serious problems in the noise, vibration and harshness(NVH) performance. Thus, the study about reducing this kind of vibration is an important task. Quantifying the effectiveness of vibration isolation can be effectively accomplished by using vibrational power flow because relative contributions of each isolator to the total vibration transmission can be easily represented. In this paper, vibrational power flow is applied to the centrifugal turbo blower mounted on FCEV in order to analyze the most dominant vibration transmitting path. As a result, the main contributor among four isolators is a mount #3 of the blower. Also, a 30 percent lowering of the mount #3 stiffness shows 34 percent decrement of vibrational power flow by the simulation.

• 대한기계학회논문집A
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• 제40권1호
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• pp.97-102
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• 2016

회전 기계에서 회전에 따른 진동은 성능 저하 및 고장의 직접적 원인이 되어, 진동을 예측하고 저감 방안을 수립하는 것이 매우 중요하지만, 회전 기계의 조립이나 설치 과정에서 발생하는 불평형의 변화나 지지 구조물의 진동 모드는 예측이 어려워 그 영향을 사전에 평가하기 어렵다. 본 논문에서는 자기베어링에 의해 지지된 터보 압축기의 전달함수를 시스템 식별과정을 통해 구하고 이를 활용하여 압축기의 불평형 응답을 예측한다. 식별된 전달함수는 회전체의 진동 모드와 지지 구조물의 진동 모드를 함께 포함하고 있어, 불평형 응답에 대한 지지 구조물의 영향을 실질적으로 평가할 수 있다. 저속 운전에 의해 불평형을 추정하고 정격 속도까지의 불평형 응답을 시험 결과와 비교하여 예측의 적절성과 문제점을 파악하였다.

• 소음진동
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• 제5권4호
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• pp.543-553
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• 1995

Modern steam turbine generators are being built as a higher power and larger system, experiencing more frequent starts and stops of operation due to a constant change of power demands. Hence, they are inevitably more vulnerable to various vibrations, and more often exposed to the danger of sudden vibration accidents than ever before. Even under the circumstances, in order to secure the system reliability of steampower plants and there by to supply safely the public electricity, it is important to prevent a sudden vibration accident in one hand and even when it happens, to raise an operating efficiency of the plants throught swift and precise treatments in the other. In this study, an interactive vibration diagnostic system has been developed to make the on-site vibration diagnosis of steam turbine generators possible and convenient, utilizing a note-book PC. For this purpose, at first the principal vibration phenomena, such as various unbalance and unstable vibrations as well as rubbing, misalignment, and shaft crack vibrations, have been systematically classified as grouped parameters of vibration frequencies, amplitudes, phases, rotating speeds at the time of accident, and operating conditions or condition changes. A new complex vibration diagnostic table has been constructed from the causal relations between the characteristic parameters and the principal vibration phenomena. Then, the diagnostic system has been developed to screen and issue the corresponding vibration phenomena by assigning to each user-selected combination of characteristic parameters a unique characteristic vector and comparing this vector with a diagnostic vector of each vibration phenomenon based on the constructed diagnostic table. Moreover, the diagnostic system has a logic whose diagnosis may be performed successfully by inputing only some of the corresponding characteristic parameters without having to input all the parameters. The developed diagnostic system has been applied to perform the diagnosis of several real cases of steam turbine vibration accidents. And the results have been quite satisfactory.

• 한국정밀공학회지
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• 제28권3호
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• pp.285-291
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• 2011

The error motion of a machine tool spindle directly affects the surface errors of machined parts. The error motions of the spindle are not desired errors in the three linear direction motions and two rotating motions. Those are usually due to the imperfect of bearings, stiffness of spindle, assembly errors, external force or unbalance of rotors. The error motions of the spindle have been needed to be decreased to desired goal of spindle's performance. The level of error motion is needed to be estimated during the design and assembly process of the spindle. In this paper, the estimation method for the five degree of freedom (5 D.O.F) error motions of the spindle is suggested. To estimate the error motions of the spindle, waviness of shaft and bearings, external force model was used as input data. And, the estimation models are considering geometric relationship and force equilibrium of the five degree of the freedom. To calculate error motions of the spindle, not only imperfection of the shaft, bearings, such as rolling element bearing, hydrostatic bearing, and aerostatic bearing, but also driving elements such as worm, pulley, and direct driving motor systems, were considered.

• Journal of Acupuncture Research
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• 제17권1호
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• pp.43-54
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• 2000

Previously two papers dealing with YoungSu(against the meridian course and following the course of the meridian) Acupuncture were published by our group. Here we are reporting the further analysis of YoungSu and WonBang(by twisting and rotating the needle) acupuncture methods. It is very important to understand objectively the Qi variation induced by the reinforcing-reducing manipulation method in the acupuncture therapy. We decided the medical treatment by utilizing the PyongChi Method (a kind of method to figure out the way of treatment by observing the unbalanced state of five phases). The Qi variation in the meridian treated by YoungSu and WonBang, the recovery of five phases deviation were measured by choosing single acupoint instead of complex acupoints. By using Youngsu and WonBang, we increased or decreased the Qi of the phase which caused the unbalanced state. We observed whether the Qi of the treated meridian can be increased and if the state of unbalance can be recovered. To achieve the effect of reinforcing-reducing, we needed a correct choice of treating method and a selection of a proper meridian in advance. This study was carried out by adding another way of acupuncture from the previous paper. We discovered that the effects of reinforcing-reducing by each manipulation method could be superposed each other when two counteracting Youngsu and WonBang methods were treated at the left and the right side of human body which was correspondent with our previous paper. We found that the Qi variation of the treated meridian, which was induced by Youngsu and WonBang, was linearly proportional to the reduction of five phase deviations. The slope of Qi variation was almost similar (y = -0.413x - 0.138) as that of previous paper (y = -0.266x - 0.038, Y = -0.446x - 0.079). It is assumed that the addition of other basic methods on the top of reinforcing-reducing manipulation method would magnify the effect of acupuncture.