• Journal of the Korean Society for Precision Engineering
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• v.25 no.10
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• pp.99-106
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• 2008

5kWh FESS(Flywheel Energy Storage System) using AMB(Active Magnetic Bearing) has been under development and 1st trial system has been finished and run the operating test. Unfortunately, the test result was not satisfactory because FESS could increase the rotational speed up to 9,000 rpm only although the target rotational speed is 18,000rpm. It's because 1st bending mode frequency of flywheel shaft was too low and imbalance response was too big. To achieve the target speed, 1st bending mode and imbalance response must be improved and the whole FESS needed to be designed again. This paper presents the newly designed FESS and what has been changed from the 1st trial FESS to improve 1st bending mode and imbalance response. The experimental results to see how much 1st bending mode frequency was improved are presented, too.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.9 no.2
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• pp.52-58
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• 2000

the quality of a TV is closely connected with the high quality surface of Braun tube. To get high quality surface an improved grinding system is needed. It has three main parts : the housing part of supporting frame the outershaft part rotat-ed by motor and the innershaft part having eccentricity from the rotation axis of the outershaft. the housing part and the outershaft part are connected by outerbearings, The outershaft part and the innershaft part are connected by innerbearings. Although the outershaft part is rotated at high-speed the innershaft part is not rotated by offset coupling. The high quality grinding surface can be obtained by this mechanism of panel surface grinder, Because the innershaft is unbalanced by eccentricity from rotation axis of outershaft the unbalancing vibration is resulted In this rotor system with high-speed rota-tion the unbalancing vibration makes the opertion unstable. In this research the transfer function is obtained bythe frequency response analysis of finite element model. The simu-lation result is proved by comparing with the experimental result measured by signal analyzer Then the results are corre-lated. in order to improve the design an optimization method is used instead of two-planes balancing method The parts of the 3-dimensional panel surface grinder satisfy the each constraint, The result shows that the design of the panel surface grinder can be optimized.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.04a
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• pp.408-414
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• 2014

After drilling operations at the offshore plant to production to crude oil to high pressure. After that time the low pressured of pipe inside when the secondary produce so oil recovery is reduced. At that time injection sea water at the pipe inside through water injection pump that the device Increase recovery so to be research and development at many industry. So developing 3-stage water injection pump at the domestic company. A variety of mathematical analysis during the detailed design analysis was not made through the dynamics characteristic. In this paper, a 2D finite element analysis is performed through the dynamics of the present study was the validation of the model.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.1
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• pp.91-103
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• 2015

This paper investigates control algorithms for a doubly fed induction generator with a back-to-back three-level neutral-point clamped voltage source converter in a medium-voltage wind power system under unbalanced grid conditions. Negative sequence control algorithms to compensate for unbalanced conditions have been investigated with respect to four performance factors: fault ride-through capability, instantaneous active power pulsation, harmonic distortions, and torque pulsation. The control algorithm having zero amplitude of torque ripple indicates the most cost-effective performance in terms of torque pulsation. The least active power pulsation is produced by a control algorithm that nullifies the oscillating component of the instantaneous stator active and reactive power. A combination of these two control algorithms depending on operating requirements and depth of grid unbalance presents the most optimized performance factors under generalized unbalanced operating conditions, leading to a high-performance DFIG wind turbine system with unbalanced grid adaptive features.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.506-507
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• 2008

소규모 풍력에너지, 연료전지 및 태양에너지 등의 신 재생에너지원들이 소규모 분산전원으로 도입되고 있다. 이로 인해, 수용가 측의 전원이 대규모 전력사업자로부터만 공급받던 시스템방식에서, 분산전원과 연계하여 동시에 사용하는 방식으로 바뀌고 있다. 이러한 분산전원이 계통에 도입될 경우 이로 인해 평상시 기존 계통의 보호방식에 미치는 영향의 경우는 상시전압변동, Flicker, 병해열로 인한 순시전압변동, 고조파, 불평형 등이 고려 될 수 있다. 또한 이러한 경우로 인해 보호계전기의 오동작도 초래 할 수 있다. 이에 본 논문에서는 태양광시스템을 분산전원으로 하는 연계 계통을 모델링하여 발생하는 파형에 대해 분석한다. 또한 디지털 보호계전기의 디지털 필터링 기법을 비교하여 빠른 연산 속도와 주파수 응답 특성을 가지는 알고리즘을 선정하고 모델링하여 모델링 된 디지털 필터로 분산전원 연계를 통해 얻어진 파형을 필터링 한다. 본 논문에서 분산전원의 계통 모의는 전력계통에 모의에 높은 신뢰성을 가지는 PSCAD/EMTDC를 기반으로 하였으며, 디지털 보호계전기의 디지털 필터 알고리즘 모델링은 MATLAB을 사용하였다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.60-64
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• 2013

Water injection pump produced the 1st oil well through the high pressure after the Deep water oil well drilling. After finish the work it is hard to produce only using itself pressure due to low pressure. Therefore it can be increased recovery factor through the injection seawater of high pressure. Is the key equipment used in the marine plant and it is developing at many industries. In this paper, Analyze changes in the natural frequency due to the stiffness of the bearing. Analyze the critical speed of the natural frequency due to the change of operation speed. And evaluate the Stability. And then analyze the displacement and clearance through the unbalance response this way has contributed to the reliability of the developing product. Through a mathematical analysis.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.8
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• pp.684-694
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• 2004

Presented in this dissertation is a new method of identifying the critical speed of rotor-bearing systems without actually reaching at the critical speed itself. Using the method, it is possible to calculate the critical speed by measuring a series of rotor responses at much lower rotating speeds away from and without reaching at the critical speed of the system. In the course of the procedures illustrated, not only the critical speed but also the damping ratio and the eccentricity of the system can be identified at the same time. Test rotor was tested on the Rotor Dynamics Test Facility at the Korea Institute of Machinery ＆ Materials. Korea, and the theory has been confirmed experimentally. The method can be adopted to monitor changes of the dynamic characteristics of critical rotating machinery before and after overhauls, repairs, exchanges of various parts, or to detect trends or direction of subtle changes in the dynamic characteristic parameters over a long periods of time.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.7
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• pp.688-694
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• 2008

A rotordynamic analysis is performed for a high thrust class liquid rocket engine turbopump considering the dynamic characteristics of ball bearings and pump noncontact seals. Complex eigenvalue problems are solved to predict the rotating natural frequencies and damping ratios as a function of rotating speeds. Synchronous rotor mass unbalance response and time transient response analyses are also performed to figure out the rotor critical speed and the onset speed of instability. From the numerical analysis, it is found that the rear bearing stiffness is most important parameter for the critical speed and instability because the 1st mode is turbine side shaft bending mode. The pump seal effect on the critical speed is enlarged as the rear bearing stiffness decreases and the front bearing stiffness increases.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.4
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• pp.511-519
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• 2013

Switching controllers for active magnetic bearings are claimed to minimize the copper losses because they do not use bias currents. In this study, we compare the performances of the switching controller with those of the widely used proportional-derivative (PD) controller. The PD controller is combined with a synchronous notch filter to reduce the effect of the unbalance disturbance. For a fair and objective comparison, the PD controller is designed systematically. The switching controller is designed so that the dynamics of the two controllers are almost identical. A system model is developed. This model includes the flexible modes of the rotor and the dynamics of the sensors and amplifiers. The simulation results show that the switching controller indeed reduces the copper loss at lower speeds. However, it fails to operate around the speed close to the bending mode of the rotor.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.6
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• pp.462-469
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• 2014

After drilling operations at the offshore plant, crude oil is producted under high pressure. After that time, oil recovery is reduced, because the pressure of the pipe inside is low during the secondary produce. At that time injection sea water at the pipe inside through water injection pump that the device increase to recovery. A variety of mathematical analysis during the detailed design analysis was not made through the dynamics characteristic at the domestic company. 2D model has reliability of analysis results for the uncomplicated model. Also element and the node the number of significantly less than in the 3D model. So, the temporal part is very effective. In addition, depending on the quality of mesh 3D is a real model and FEM model occurs error. So, user needs a lot of skill. In this paper, a 2D finite element analysis was performed through the dynamics analysis and the study model was validated.