• Proceedings of the KSR Conference
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• 2011.10a
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• pp.3124-3132
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• 2011

Scott transformers have widely used to convert three phases into two phases and compensate the unbalance. Theoretically, the loads of the two secondary phases are same, no unbalance appears in the PCC(point of common coupling). But Due to the uncertainty of traction load, the unbalance are generally presented at the PCC. In this paper The amount of the voltage unbalance is expressed in the ratio of the negative sequence voltages to the positive sequence voltage. We tried to compensate the unbalance using SVC(Static Var Compensator）in an unbalance traction loads state by modeling. The SVC are installed and controlled to provide different amounts of reactive power compensation.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.8
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• pp.11-16
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• 1998

Recently, the motor-integrated spindle systems have been used to simplify the machine tool structure, to improve the motion flexibility of machine tool, and to perform the high-speed machining. In this study, a static and dynamic analysis system for motor-integrated high-speed spindle systems is developed based on Timoshenko theory, finite element method and windows programming techniques. Since the system has various analysis modules related to static deformation analysis, modal analysis, frequency response analysis, unbalance response analysis and so on, it is useful in performing systematically the design and evaluation processes of motor-integrated high-speed spindle systems under windows GUI environment.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.356-360
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• 2003

At rotating machinery, Many factors had caused vibration. especially one of the major factor is mass unbalance. A sort of mass unbalance are followings; Static, Coupling, Single and Dynamic. In this paper, We had investigated abnormal vibration due to mass unbalance that changed phase whenever starting of steam Turbine at Combined Cycle.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.266-271
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• 1997

본 연구는 믹서기의 다지기칼날(Mincing Knife)이 구조적으로 가지고 있는 모멘트불평형(Couple Unbalance) 문제를 해결하기 위한 밸런싱방법을 제시한다. 유한요소법에 의하여 칼날에 작용하는 원심력, 정적 불평형량(Static Unbalance) 및 불평형각위치(Unbalance Angle)를 계산하고, 이를 바탕으로 반고리(Semiannular) 형상의 질량을 설계하여 모멘트 밸런싱을 수행하였다. 밸런싱을 수행한 후의 다지기칼날은 분해칼날(Cutting Knife)과 거의 비슷한 동적거동을 가지게 됨을 확인하였다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.836-840
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• 1995

Recently, the motor-integrated spindle spindle systems have been used to simplify the machine tool structure, to improve the motion flexibility of machine tool, and to perform the high-speed machining. In this study, a static and dynamic analysis system for motor-integrated high-speed spindle systems is developed based on Timoshenko theory, finite element method and windows programming techniques. Since the system has various analysis modules related to static deformation analysis, modal analysis, frequency response analysis, unbalance response analysis and so on, it is useful in performing systematically the design and evaluation processes of motor-integrated high-speed spindle systems under windows GUI encironment.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.11
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• pp.1387-1395
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• 2013

When the center of mass of a railway wheel is not aligned with the geometrical center of the wheel axis, wheel unbalance occurs. If a railway vehicle runs without removing the wheel unbalance, vibrations will be produced. This will also cause wear and damage of the axle bearing. In this study, dynamic analysis of a railway vehicle with wheel unbalance was conducted to examine the reduction in critical speed and the resonance of the car-body and the effect on the magnitude of wheel unbalance was examined. In addition, the calculation of the car-body vibration owing to static and dynamic unbalance in the railway wheel shows that two-plane balancing is necessary.

• Journal of international Conference on Electrical Machines and Systems
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• v.3 no.2
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• pp.155-161
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• 2014

Industrial Static Var Generator (SVG) is typically applied at or near the load center to mitigate voltage fluctuation, flicker, phase unbalance, non-sine distortion or other load-related disturbance. Special attention is paid to the influence of grid voltage quality on SVG current, the non-sine distortion and unbalance of grid voltage causes not only the AC current distortion and unbalance but also the DC voltage fluctuation. In order to let the inverter voltage contain the fundamental negative sequence and harmonic component corresponding to the grid voltage, a new dual-loop control scheme is proposed to suppress the influence in this paper. The harmonic and negative sequence voltage decomposition algorithm and DC voltage control are also introduced. All these analyses can guide the practical applications. The simulation results verify the feasibility and effectiveness of the present control strategy and analyses.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.614-617
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• 1995

The unbalance heavy-load elevation driving systems are composed of rotating link-mechanism and hydraulic cylinder which actuates elevation and compensates the static unbalance moment of supporting mechanism. Control and compensation of gun driving is very difficult because these mechanism imply highly nonlinearities due to hydraulic fluid characteristics and mechanical rotation of link-mechanism. In this study, through the analysis of manufactured link-mechanism, the optimal link-mechanism design of the elevating system is suggested. Also to estimate the control performance of the unbalance heavy-load elevation servo-control driving system, modeling and simulation of the system are carried out. To prove the reliability of performance estimation program,simulation results are compared with the experimental results. Both results are similar, therefore this program will be helpful to study the control performance improvement of the system.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.4
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• pp.332-341
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• 2014

A cascaded H-bridge multi-level STATCOM(STATic synchronous COMpensator), which is composed of many cell inverters with independent dc-sources, generates inevitably dc-side voltage unbalance among phases when it compensates unbalanced load. It comes from the difference of flowing active power in each phase when this compensator makes negative-sequence current to eliminate the unbalance of source-side current. However, this unbalance can be controlled by injecting zero-sequence current which is decoupled with grid currents, so the compensator can work well during this balancing process. Both a feedback control algorithm, which produces zero-sequence current proportional to dc-side voltage unbalance within each phase, and a feedforward control algorithm, which makes zero-sequence current directly from the compensator's negative-sequence current, were proposed. The dc-side voltage of each phase can be controlled stably by these proposed algorithms in both steady-state and transient, so the compensator can have fast response to satisfy control performance under rapid changing load. These balancing controllers were implemented and verified via simulation and experiment.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.695-698
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• 2004

STSAT RWA (Reaction Wheel Assembly) micro-vibration is measured using KISTLER dynamic plate that can provide the time signals of three orthogonal forces and torques simultaneously up to 400Hz. In the post-processing, measured data are evaluated with respect to the wheel spin rate in both time and frequency domains, and the static/dynamic unbalances are evaluated from the extracted first harmonic component. Also the friction torque profile at each wheel speed is estimated from the measured data. Several higher order harmonic components are observed, that comes from its rotor shape as well as the wheel bearing characteristics. One of the most peculiar characteristics of this wheel is that the dynamic properties of two radial unbalance components are much different from each other as the RWA mounting configuration on a spacecraft is different from conventional RWA mounting configuration. Rocking mode is not appeared below 400Hz for all operating speed because the wheel size is very small. The post-processed results will be used for jitter analysis of STSAT due to RWA micro-vibration.