• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.9
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• pp.1206-1211
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• 2014

Most LV customers have been applying three-phase four-wire electric distribution system which supplies 1-phase and 3-phase load concurrently. Due to its structural simplicity, This system is easy to run. But it can also cause many problems from the unbalance, such as reduced output, increased loss etc. Also the unbalance in the load side causes the unbalance in the source side; it may lower the stability of the whole power system. In this paper, we propose the Y-Tz transformer winding method to reduce the current unbalance in the source side. Efficiency of this method was proven through the simulation and verification experiment.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.5
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• pp.64-72
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• 2008

In the three phase four wire system, voltage unbalance caused by the unbalanced load operation, gives rise to current unbalance and de-rates by the increase of machine's loss and eventually enlarges power capacity and besides has a bad effect on power quality. Power capacitor has been used for the power factor correction of inductive load and the voltage stability of power system. And it uses instead of power side for magnetic excitation of induction motor. If voltage unbalance keeps up, it affects on voltage stress at the power capacitor and finally can be caused breakdown. In this paper, we analysed that voltage and current of power capacitor increases by the voltage unbalance factor and its stress is growing more and more.

• Proceedings of the KIEE Conference
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• 2003.10b
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• pp.110-112
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• 2003

This paper describes a detailed performance of induction motor with asymmetric voltage unbalance generated at the customer distribution system. The simulation results show that the change of current and torque, with the increase of unbalance factor, are more larger and has an important effect on load system.

• 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 KIPE Conference
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• 2001.07a
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• pp.172-176
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• 2001

In this paper, a new detection algorithm of faulted voltages under the unbalanced condition and a control algorithm of the instantaneous voltage sag corrector (IVSC) are proposed. To quantify the unbalance under fault conditions, the voltages are decomposed into two balanced three-phase systems using the symmetrical components of positive and negative sequence voltages, which is defined by magnitude factor (MF) and unbalance factor (UF). New control algorithm based on MF and UF values for instantaneous voltage compensation are proposed and verified through the PSCAD/EMTDC simulation and experimental results.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.56 no.3
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• pp.123-128
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• 2007

Hydro power supplies no pollution energy, mainly induction generator has been applied at the small capacity power station. The generating power of small hydro-electric power station connects on the 22.9kV distribution system or low voltage system in the case of three-phase four-wire supply system. There are side effects of various kinds in the 3-three phase 4-wire distribution system mixing 1-phase load and 3-phase load. This system generates the voltage unbalance by unbalanced load operating condition. They have various serious effects on generator and connection system. In this paper, we analyzed what kind of operation characteristic are happened in the induction generator by customer load variation at the 3-three phase 4-wire distribution system.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.54 no.3
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• pp.134-140
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• 2005

Most of the loads in industrial power distribution systems are usually balanced and connected to three power systems. However, in the user power distribution systems, partial loads are single & three phase and unbalanced, generating voltage unbalance by the impedance mismatching. Voltage unbalance has detrimental effects on three-phase induction motors, including over heating, line-current unbalance, derating, torque pulsation, low efficiency, etc. This paper presents a scheme on operation states of a three-phase induction motor under the unbalanced voltages with harmonics components. Three-phase voltages applied to the stator winding of the studied induction motor are controlled by respectively adjusting not only fundamental but also harmonics components. Harmonic components at the voltage unbalanced factor(VUF) of the three-phase source voltages can then be examined the different values of VUF on machine's operation characteristics.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.258-260
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• 1995

This paper deals with the voltage unbalance of DC link voltage in series connected two 6-step inverters with double chopper preregulator. Each output of the 6-step inverter is connected to each transformer. The secondary windings of one of the transformers is zig-zag connected and the other star connected. The secondary terminals of the two transformers are series connected which makes 12-step output voltage waveform. In this case, the characteristics of the two transformers are rather different each other. The difference results in the voltage unbalance of the two 6-step inverter input capacitor voltages which make the DC link voltage. The degree of the voltage unbalance is analysied with the variations of load power, load power factor and % impedance of the transformer.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.256-260
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• 2013

The fan-shroud plays the important role in cooling down the engine heat by the forced convection. As the fan-shroud is made by injection molding, the unbalance of the fan blades is inevitable, and its low frequency characteristics makes it easy to excite the resonances of the environmental structures. So controlling its vibration, specially the dominant vibration source of unbalance vibration, is one of key factor to improve the sound and vibration quality of the modern vehicles. This paper introduces the plane balancing method, the most appropriate way of controlling the fan-shroud by generating the acceleration orbit measured from 2 accelerometers, and proves its balancing effect by the experiment.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.53 no.2
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• pp.58-64
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• 2004

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 is a condition in a polyphase system in which the rms values of the line-to-line voltages or the phase angles between consecutive line-to-line voltages, are not all equal. Slight voltage unbalance generates a disproportionately high current unbalance at the motor stator winding. This paper presents a scheme on operation states of a three-phase induction motor under unbalanced voltages. The three-phase voltages applied to the stator winding of the studied induction motor are controlled by respectively adjusting the magnitude and phase angle of each phase. The voltage unbalanced factor(VUF) of the three-phase source voltages can then be varied to examine the different values of VUF on machine's operation characteristics.