• The Transactions of the Korean Institute of Electrical Engineers P
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• v.54 no.1
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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.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.808-815
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• 2001

The three-phase diode rectifier with a capacitive filter is highly sensitive to line voltage unbalance, and may cause significantly unbalanced line currents even under slightly unbalanced voltage condition. This paper presents an analysis of this 'unbalance amplification' effect for an ideal rectifier circuit without ac-and dc-side inductors. The voltage unbalance is modeled by introducing a deviation voltage superimposed on balanced three-phase line voltages. With proper approximations, closed-form expressions for symmetrical components of the line current and current unbalance factor are derived in terms of the voltage unbalance factor, filter reactance, and load current. The validity of analytical predictions is confirmed by simulation.

• Proceedings of the KIEE Conference
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• 2005.04a
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• pp.28-30
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• 2005

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. The voltage unbalance factor of the three-phase 4-wire system is approved by the field measurement. This system is composed of three one-phase transformer with each other capacity. Current unbalance factor is measured by the power quality measurement apparatus and compared by the load unbalance factor. Each phase has an impedance each other by the unbalanced load operation pattern and give rise to voltage unbalance.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.55 no.2
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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.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.8
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• pp.1291-1296
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• 2017

Single-phase and three-phase load can be used together in 3-phase 4-wire system. Single-phase and three-phase loads can be classified as linear loads without harmonics and nonlinear with harmonics. Single-phase linear loads are linear loads such as lamps and heat, and single-phase nonlinear loads are power converters such as rectifiers. It is recommended that the distribution of loads in the 3-phase, 4-wire distribution lines be evenly distributed within a certain range. However, harmonic currents generated in a nonlinear load flow on the neutral line and affect the phase current magnitude. The difference in the magnitude of the individual phase current due to the influence of the harmonic current present in the neutral line can produce a difference in current and load unbalance. In this study, current unbalance ratio and load unbalance ratio which can occur when a combination of linear and nonlinear loads are applied to 3-phase 4-wire distribution line are calculated.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.3
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• pp.587-592
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• 2017

In the three-phase four-wire low-voltage power distribution equipment, single-phase and three-phase load have been used mainly mixed. Also linear and nonlinear loads have been used together in the same conditions. In a three-phase four-wire distribution line, the current distribution of three-phase linear load is almost constant in each phase during driving or stopping, but the single-phase load is different from each other for each phase in accordance with the operation and stop. So that the voltage unbalance is caused by the current difference of each phase. In the three-phase four-wire distribution system, non-linear load is used with linear load. The presence of single-phase nonlinear loads can produce an increase in harmonic currents in three-phase and neutral line. It can also cause voltage unbalance. In the present study, we analyzed for the voltage unbalance fluctuations by the operation pattern of the single and three-phase linear and non-linear load in three-phase four-wire low voltage distribution system.

• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.4
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• pp.38-38
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• 2001

The three-phase diode rectifier with capacitive filter is highly sensitive to line voltage unbalance. Because of its inherent nonlinear characteristics, small line voltage unbalance may cause highly unbalanced line current, causing detrimental effects on power quality. This paper presents a theoretical basis on this ′unbalance amplification effect′ and derives an analytical model of line current characteristics under unbalanced line voltage condition for various modes of operation. The results provide a basic guideline for optimal design of a three-phase diode rectifier with capacitive filter that is most commonly used for interfacing various power conversion equipments to power lines.

• Proceedings of the KIEE Conference
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• 2006.10b
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• pp.147-153
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• 2006

Voltage unbalance will be generated by the load unbalance operation such as combination operation of single & three phase load and current unbalance will be more severe by the deteriorated voltage quality. Under the these unbalance conditions, all power electronic converters used in different types of electronic systems can increase harmonic disturbances by injecting harmonic currents directly into the feeder grid of three phase 4-wire. Harmonic current may cause torque to decrease. it may also overheat or become noisy and torque oscillation in the rotor can lead to mechanical resonance and vibration. This paper presents a scheme on the characteristics of induction motor under the combination of linear & non-linear loads at the three phase 4-wire power distribution system by the unbalance and harmonic components. It was able to confirm that the number of torque pulsation decreased and torque ripple values increased by the harmonics that reduction was difficult by five harmonics filters at additional driving time of single-phase non-linear load.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.9
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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.

• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.4
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• pp.348-361
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• 2001

The three-phase diode rectifier with capacitive filter is highly sensitive to line voltage unbalance. Because of its inherent nonlinear characteristics, small line voltage unbalance may cause highly unbalanced line current, causing detrimental effects on power quality. This paper presents a theoretical basis on this 'unbalance amplification effect' and derives an analytical model of line current characteristics under unbalanced line voltage condition for various modes of operation. The results provide a basic guideline for optimal design of a three-phase diode rectifier with capacitive filter that is most commonly used for interfacing various power conversion equipments to power lines.