• 대한전기학회논문지:전력기술부문A
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• 제52권5호
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• pp.263-270
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• 2003

In field applications, to represent the degree of voltage unbalance, the maximum voltage deviation from the average is preferred to the voltage unbalance factor based on symmetrical component analysis. This paper first clarifies the relationship between the voltage unbalance factor and the maximum deviation factor showing that the maximum deviation factor approximates the voltage unbalance factor under relatively low unbalanced conditions. Several alternative ways of approximation are introduced and examined by comparing with the conventional maximum deviation factor. It appears that these alternatives provide more accurate approximation to the voltage unbalance factor over wider range of voltage unbalance while maintaining simplicity in their formula.

• 전기학회논문지P
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• 제54권1호
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• pp.47-53
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• 2005

Most of the loads in industrial power distribution systems are balanced and connected to three power systems. However, in the user power distribution systems, most of the loads are single & three phase and unbalanced, generating voltage unbalance. Voltage unbalance factor is mainly affected by load system rather than stable power system. Unbalanced voltage will draw a highly unbalanced current. As a result, the three-phase currents may differ considerably, thus resulting in an increased temperature rise in the machine. This paper presents a scheme on the characteristics of voltage and current unbalance factor under the load variation at the three phase 4-wire system. Load unbalance factor is measured by the power quality measurement apparatus and compared by the current unbalance factor. Two methods are indicated similar results. The voltage unbalance factor of the three-phase 4-wire system is approved by the field measurement. Each phase has an impedance each other by the unbalanced operation pattern and give rise to voltage unbalance.

• 전기학회논문지P
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• 제55권2호
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• pp.67-72
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• 2006

Most of the load distributions in low voltage power feeder distribution systems are designed with approximately balanced and connected at the three phase four wire systems. However, in the user power distribution systems, most of the loads are single & three phase and unbalanced, generating load unbalance. Load unbalance factor is mainly affected by the impedance of load system. Unbalanced current will draw a highly unbalanced voltage. This paper presents a new calculation method for unbalance factor under the load variation at the three phase four wire system. Load unbalance factor is measured by the power quality measurement apparatus and compared with the current unbalance factor. Two methods are indicated similar results.

• 대한전기학회논문지:전력기술부문A
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• 제52권5호
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• pp.257-262
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• 2003

The voltage unbalance factor derived from symmetrical component analysis requires manipulation of complex quantities. To facilitate the calculation of the voltage unbalance factor in field applications, this paper proposes the method for calculating the voltage unbalance factor in terms of the line voltage magnitudes that are readily available in moat practical circumstances. It is shown that the line voltages appear as circular Phasor loci for given voltage unbalance factor, and a graphical chart is developed that can be used to determine the voltage unbalance factor in a straightforward manner avoiding calculation.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.358-362
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• 2002

The HDD unbalance, with higher rotational speed, is directly influenced by the mechanical assembly allowance between clamping disk and platter disk. The low frequency structural vibration induced by the unbalance force finally gives rise to the structure borne noise of the personal computer. To meet the noise and vibration requirements, the absolute unbalance mass of HDD needs to be measured and adjusted in the disk assembling stage. This study introduces the measurement methods of the absolute magnitude and position of the unbalance mass of HDD based on the mobility and acceleration orbit. The absolute unbalance mass can be obtained by the acceleration responses and the mobility of the mechanical part, while the position of the unbalance mass ran be obtained by the rotation acceleration orbit.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.505-509
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• 2001

When the spindle is rotated for machining the workpiece, the vibration is generated due to the spindle unbalance. This vibration affects surface finish, dimensional accuracy, tool life, and spindle bearings. To compensate this effect of the spindle unbalance, the spindle system using an EME(electro magnetic exciter)is proposed in this paper. In the proposed spindle system, the vibration due to the spindle unbalance is monitored using vibration sensors and is compensated by electromagnetic attractive forces generated in the EME which are excited by anti-direction forces corresponded with the measured unbalance. Firstly, the spindle system using an EME and control system are constructed to compensate the effect of spindle unbalance in this paper. And then the system is modeled by bond graph to analyze the system. Finally, a controller for vibration compensation due to spindle unbalance is designed and is implemented in real experimental system. As a result, experimental results show this proposed spindle system is very effective to compensate the spindle unbalance.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.340.1-340
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• 2002

The unbalance exciting force induced by HDD of lately getting higher speed is directly influenced by the rotational speed and the mechanical assembly allowance between disk and spindle motor, and which gives rise to the structure borne noise of the personal computer. The absolute unbalance mass of HDD needs to be measured and adjusted by the counter mass to control the unbalance exciting force effectively in the stage of assembling the disk and spindle motor. This study introduces the measurement methods of the magnitude of the absolute unbalance mass and the position of HDD by 2 accelerometers. The absolute unbalance mass can be obtained by the acceleration responses and the mobility of the mechanical part, while the position of the unbalance mass can e obtained by the rotation acceleration orbit.

• Transactions on Control, Automation and Systems Engineering
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• 제2권4호
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• pp.228-234
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• 2000

The aim of the work is to present a new method of estimating the existence of a mass unbalance and mass unbalance under a crack on a rotating shaft. This is an advanced new method for the detection of a mass unbalance and a new way to estimate the position of it under crack influence. As the first step, the shaft is physically modelled with a finite element method and the dynamic mathematical model is derived by using the Hamilton principle; thus, the system is represented by various subsystems. The equation of motion of the shaft with a mass unbalance and a crack are established by adapting the local mass unbalance and the stiffness change. this is a reference system for the given system. Based on a model for transient behavior induced from vabrations measured at the bearings, an elementary Estimator is designed to detect mass unblance on the shaft. Using the Estimator, a bank of the Estimator is established to estimate the estimate the position of the mass unbalance and arranged at a certain location on the shaft. The informations for the given system are the measurements of bearing displacements and velocity.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 B
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• pp.791-793
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• 2004

Voltage unbalance is generated by the load and impedance mismatching at the 3-phase 4-wire system of customer load. Voltage unbalance factor can be changed by the voltage amplitude or phase angle, and both. A small voltage unbalance is connected to high current unbalance. If the voltage unbalance is generated at the joint system of 1-phase and 3-phase load, Induction motor due to the current unbalance increase is generated loss, noise and torque ripple. In order to analyze the effect by voltage unbalance, it is necessary to the consideration of amplitude and phase angle. In this paper, We analyzed the effects that induction motor is affected by asymmetric voltage unbalance

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제54권9호
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• pp.403-407
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• 2005

Most of the loads in industrial power distribution systems are balanced and connected to three power systems. However, voltage unbalance is generated at the user's 3-phase 4-wire distribution systems with single & three phase. Voltage unbalance is mainly affected by load system rather than power system. Unbalanced voltage will draws a highly unbalanced current and results in the temperature rise and the low output characteristics at the machine. It is necessary to analyse correct voltage unbalance factor for reduction of side effects in the industrial sites. Voltage unbalance is usually defined by the maximum percent deviation of voltages from their average value, by the method of symmetric components or by the expression in a more user-friendly form which requires only the three line voltage readings. If the neutral point is moved by the unbalanced load at the 3-phase 4-wire system. Line and phase voltage unbalance leads to different results due to zero-sequence component. So that it is difficult to analyse voltage unbalance factor by the conventional analytical method, This paper presents a new analytical method for phase and line voltage unbalance factor in 4-wire systems. Two methods indicate exact results.