• Journal of the Institute of Electronics and Information Engineers
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• 제51권12호
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• pp.197-203
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• 2014

When the lightning current is injected to the ground system of information and communication facilities, analysis of the transient potential rise in the ground system is one of main factors to effectively design the ground system. The performance of grounding systems is normally estimated with the grounding impedance and the transient potential rise which represents the electrical characteristics of the grounding system. The method for calculating the grounding impedance depending on the injection point of the lightning current was proposed. The delta-gap source model was proposed to calculate the grounding impedance in the case that the lightning current is injected to the center of the horizontal ground electrode. A new program which is possible to apply the frequency-dependent soil parameters using the Debye model was developed, because a commercial program for analyzing the performance of the grounding system can not apply to the frequency-dependent soil parameters. The experiment was carried out to confirm the availability of the simulation results with the same condition. Finally, the transient potential rises of a horizontal ground electrode depending on the lightning current waveforms were analyzed by using the results of the grounding impedance which is associated with the frequency-dependent soil parameters.

• The Transactions of The Korean Institute of Electrical Engineers
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• 제58권2호
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• pp.301-307
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• 2009

In the paralleled converter module with peak current mode control, current imbalance appears when the voltage controllers with integral control of converter module are not exactly identical. In this paper, the voltage controller is designed to equal the current command of each converter module using the current command bus. The current balance controller is also proposed to balance the average currents of converter modules with imbalaced inductance. It is designed to have good transient response. Proposed method is implemented with the paralleled 2-module and 4-module boost converters with imbalanced inductance. Experimental results verify the performance of current share during both steady and transient states of converter.

• The Transactions of The Korean Institute of Electrical Engineers
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• 제67권9호
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• pp.1159-1164
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• 2018

Vacuum circuit breakers(VCB) are widely used for current interruption of high-voltage inductive loads such as induction motors. This VCB can be chopped off before the current zero due to its high arc-extinguishing capability. One of the outstanding features of VCB is that it can cut off high frequency re-ignition current more than other circuit breakers. If the transient recovery voltage generated in the arc extinguishing is higher than the dielectric strength of the circuit breaker, a re-ignition phenomenon occurs. The surge voltage of the re-ignition is very high in magnitude and the steepness of the waveform is so severe that it can act as a high electrical stress on the winding. If the high frequency current of one phase affects the other two phases when the re-ignition occurs, it may cause a high surge voltage due to the virtual current chopping. If the magnitude of the voltage allowed in the motor winding is high or the waveform level is too severe, it may lead to insulation breakdown. Therefore, it is necessary to reduce the voltage to within a certain range. In this study, we briefly explain the various phenomena at the time of interruption, analyzed the magnitude of the dielectric strength and the transient recovery voltage at the simultaneous three-phase interruption that can give the greatest influence to the inductive load, proposed a method to reduce the impact.

• Journal of Advanced Marine Engineering and Technology
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• 제25권5호
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• pp.1065-1075
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• 2001

It is common knowledge amongst electrical and marine engineers that short-circuit in electrical system may cause large mechanical torque on generator and prime mover However, it is not so widely known that the faulty synchronizing of generators may cause even higher torques than that of short-circuit. In this study, the transient phenomena related to the parallel running of synchronous generators are analyzed and the exact computer simulation method is proposed. In result, maximum transient torque and current take place in case of $120^{\circ}$ voltage angle difference between Master and Slave and that may develop higher torque than the short-circuit according to a condition of synchronizing. When synchronizing in power system using only two generators higher torque and current occur Master, but using multimachine system those occur to Slave. The short-circuit of marine generator does not happen frequently but faulty synchronizing sometimes takes place, therefore, it is necessary for designers to consider these phenomena.

• Proceedings of the KIEE Conference
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• 대한전기학회 1997년도 추계학술대회 논문집 학회본부
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• pp.361-363
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• 1997

Electronic devices are very weak against lightning surges injected from grounding systems and can be damaged. The malfunction and damage of electronic circuits bring about several disadvantages such as low operation performances, a lot of economical losses, and etc. In order to obtain the effective protection measure of electronic devices from overvoltages and lightning surges, the analysis of the transient grounding impedances is very important. The aim of this work is to evaluate the behaviors of transient grounding impedances under impulse currents and to investigate the effect of grounding lead wire. Z-t, Z-i and V-i curves of transient grounding impedance under impulse current waveforms have been measured and analyzed.

• Proceedings of the KIEE Conference
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 C
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• pp.2235-2237
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• 2005

This paper presents the transient impedance behaviors of grounding systems to lightning impulse current. The potential rise and effective impulse ground impedance of the test grounding electrodes were measured as a function of the rise time of impulse currents and lengths of down conductor. The transient ground impedances strongly depend on the configuration and size of grounding electrodes, the impulse current shapes and lengths of down conductor, and the inductance of reduce of grounding electrode inductance is an important factor to improve the transient ground impedance.

• The Transactions of the Korean Institute of Power Electronics
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• 제18권6호
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• pp.507-514
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• 2013

In this paper, the proposed charging algorithm is converted from the charging mode to compensate the transient state in the solar battery charging system. The maximum power point tracking (MPPT) control methods and the various charging algorithms for the optimal battery charging are reviewed. The proposed algorithm has excellent transient characteristics compare to the previous algorithm by adding the optimal control method to compensate the transient state when the charging mode switches from the constant current mode to the constant voltage mode based on the conventional constant-current constant-voltage (CC-CV) charging algorithm. The effectiveness of the proposed method has been verified by simulations and experimental results.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
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• pp.855-858
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• 2008

Transient current (TC) on bulk-state liquid crystal mixtures was measured. We found that TC is very sensitive to impurities and the features of TC curves depend on the type of contamination, from which the quality of materials can be definitely evaluated and the type of impurities can also be revealed.

• Proceedings of the KIEE Conference
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• 대한전기학회 1989년도 추계학술대회 논문집 학회본부
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• pp.245-249
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• 1989

From the careful analysis of the transformed dq system equations of a PWM Voltage Source Converter ( PWM - VSC ), a novel voltage control is proposed which is based on the derivative of in-phase current component of line currents and the relation between dc-link voltage and in-phase current component. A simple logical algorithm to implement the proposed scheme is also presented at transient state. The sinusoidal PWM is adopted at steady state. The simulation results show good transient characteristics.

• Proceedings of the KIEE Conference
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• 대한전기학회 2002년도 하계학술대회 논문집 A
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• pp.232-234
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• 2002

A Vacuum Circuit Breaker Model for simulation of transient overvoltages was developed by using the PSCAD/EMTDC. The Model includes the power frequency chopping current. Breaker withstand voltage, and quenching capability of High frequency currents. To verify the abilities of the breaker model, the simulation on the Lindmayer's single-phase circuit was carried out. The results show that using the proposed model, the transient overvoltages, current chopping, and multiple reignitions of vacuum breaker are properly reproduced as real phenomena. In further study, virtual chopping current will be incorporated into the model for 3 phase system.