• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.6
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• pp.262-270
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• 2003

In this paper, the characteristics of single-phase line-start permanent magnet synchronous motor driven by constant voltage are analyzed on d-q axis vector diagram and compared with that of current controlled motor. The coupled method of symmetrical coordinates and d-q axis voltage equation are applied to the analysis method like the analysis of single-phase induction motor. From the result of the analysis, it is seen that motors driven by constant voltage source have effects on not only the amplitude of current and torque but also current and current phase angle, so overall characteristics such as power factor and load angle are affected by circuit parameters. For precise analysis and design of single-phase line-start synchronous motor, its characteristics should be analyzed on d-q axis vector plan in consideration of the variation of circuit parameters.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.500-502
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• 2003

This paper reviews calculating of induced voltage onto a communication line from 22.9kV-Y Distribution Lines. The coexistence of both power line and communication line in parallel generates the induction of significant longitudinal voltage in the weak current line. In order to evaluate a precise induced voltage, this paper indicated some problems about coefficient and numerical formula. It also presents some induced voltage production technology standard application.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1995.05a
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• pp.163-166
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• 1995

A solar cell I-V (current-voltage) characteristic measurement facility is crucial, for the characteristic of solar cells, The solar cell I-v tester has been designed and fabricated to characterize the solar cell at SAIT.

• Journal of Power Electronics
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• v.11 no.5
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• pp.655-661
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• 2011

This paper presents two topologies for single-stage single-phase double-buck type PFC converters, designed to operate at high power factor, near sinusoidal input currents and adjustable output voltage. Unlike the known buck type PFC topologies, in which the output voltage is always lower than the maximum input voltage, the proposed converters can operate at output voltages higher than the ac input peak voltage. A reduced number of switches on the main path of the current are another characteristic of the two proposed topologies. To shape the input line currents, a fast and robust controller based on a sliding mode approach is proposed. This active non-linear control strategy, applied to these converters allows high quality input currents. A Proportional Integral (PI) controller is adopted to regulate the output voltage of the converters. This external voltage controller modulates the amplitude of the sinusoidal input current references. The performances of the presented rectifiers are verified with experimental results.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.2069-2070
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• 2011

In this paper, the fault diagnosis for a gearbox of BLDC motor. The stator of BLDC motor consists of coil winding so it is easy to cool down and it also has a high reliability. In addition, it doesn't have a brush so it is less trouble and good in maintenance. Coupling with the motor which is the power sources, the gear has a high power transfer efficiency and various rotation speed. The gear gets a high driving force through deceleration. Thus it has been widely used. The gearbox fault detection area has not attracted much attention from electrical engineering community. A few papers describe gearbox fault based on vibration. Gearbox fault is diagnosed through FFT analysis of current and voltage. Fault characteristic frequency side band detected by calculating fault frequency. A threshold value is suggested by comparing normal peak value with fault peak value using detected fault characteristic frequency side band. Experimental results demonstrate that motor current and voltage signal analysis are viable tools in detecting these gear faults. Lower side band(LSB) is bigger than upper side band(USB) in current FFT. LSB and USB are similar in voltage FFT. Finally, fault diagnosis system that can easily detect flaws is developted for gearbox of BLDC motor.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.10
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• pp.93-100
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• 2013

Generally, the conventional battery charging system using an analog method has the large, heavy hardware and low efficiency. Also, it has the disadvantage that it is necessary to replace the control circuit on the basis of the characteristic curve of the specific battery cell. The proposed programmable digital LLC resonant charging system use high efficiency control system(CC-CV), and has characteristic a small hardware and advantage that a digital programming of the voltage, current, and battery capacity characteristics can be flexible. The system proposed the use of Half-bridge LLC resonant converter is possible to improve efficiency and reduce switching losses by using ZVS topology. Further, a constant voltage - constant current(CC-CV) control algorithm apply to the charger which using a buck converter. The performance of the proposed system is demonstrated through experiments.

• Progress in Superconductivity
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• v.2 no.2
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• pp.71-75
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• 2001

The effect of annealing step-edges of LaAlO$_3$ and MgO single crystal substrates on YBa$_2$Cu$_3$O$_{7}$ junction has been studied. The step-edge was fabricated by argon ion milling and was annealed at 105$0^{\circ}C$ in 1 attn oxygen pressure. We compared AFM image near step-edge of the substrates between before and after annealing process. And YBa$_2$Cu$_3$O$_{7}$ thin film was deposited on the step-edge by a standard pulsed laser deposition. The step-edge junctions were characterized by current-voltage curves at 77 K. The annealing of step-edges of MgO substrate improved the current-voltage characteristic of Josephson junction: double steps in the current-voltage characteristic disappeared. However the annealing for LaAlO$_3$ did not improve the junction property.rty.

• Proceedings of the KIEE Conference
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• 2005.11b
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• pp.261-263
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• 2005

In the extra and ultra high voltage system, the coupling capacitor voltage transformer (CCVT) measures the primary voltage with a small scale of voltage transformer (VT). However, the CCVT generates errors caused by the hysteresis characteristics of iron core and by the ferroresonance, inevitably. This paper proposes a compensation algorithm for the secondary voltage of a CCVT considering the hysteresis characteristics of an iron core. The proposed algorithm calculates the seconda교 current of a VT by summing the current flowing the ferroresonance circuit and the burden current; it estimates the secondary voltage of a VT; then the core flux is calculated by integrating of the secondary voltage of a VT, then estimates the exciting current using ${\lambda}-i$ characteristic of the core. The method calculates a primary voltage of a VT considering the estimated primary current. Finally, the correct voltage is estimated by compensating the voltage across the inductor and capacitor. The performance of the proposed algorithm was tested in a 345kV transmission system. The test results show that the proposed method can improve the accuracy of the seconda교 voltage of a CCVT.

• Transactions on Electrical and Electronic Materials
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• v.17 no.5
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• pp.289-292
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• 2016

This paper dealt with the optimal design of a follow current disconnector for DC arresters used in electric traction vehicles. The disconnector separates the ground lead from an arrester to prevent a line-to-ground fault of an aged arrester and should not affect the operation and function such as the reference and the clamping voltage of the connected arrester. The designed disconnector is composed of a resistor, a spark gap, and a cartridge. The results showed that the sparkover voltage increased with the gap distance whereas the reference voltage was almost the same as that without the disconnector. The sparkover voltage was 3.95 kV when the gap distance was 0.5 mm. Regardless of the gap distance, the reference and the clamping voltage of the assembled disconnector with an arrester were measured to be the same as those of the arrester alone.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.459-461
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• 2005

This paper analyses the induced voltage characteristic of CCPU with unbalanced current from distribution line on underground transmission power cable systems. In switching surge strokes, in order to obtain the data of induced voltage/current on CCPU, the actual proof test carried out. This paper is expected to contribute the establishment of proper protection methods of CCPU against the unbalanced current from distribution line on underground transmission power cable systems.