• Proceedings of the KIEE Conference
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• 1998.07c
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• pp.834-836
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• 1998

Current transformer (CT) saturation may cause a variety of protective relays to malfunction. The conventional CT is designed that it can carry up to 20 times the rated current. However, the possibility of CT saturation still remains, because the fault current may have substantial amounts of ac and/or de components. This paper presents a iron-cored CT design method to prevent CT saturation. The proposed method employs the overdimensioning factor $(K_{ta})$ considering dc components contained as well as symmetrical ac components in the fault current.

• Journal of Power Electronics
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• v.14 no.1
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• pp.135-142
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• 2014

In the design of battery chargers, limiting the output ripple current according to the manufacturer's recommendation is important for reliable service and extended battery life. Ripple components can cause internal heating of the battery and thus reduce the service life of the battery. Care must be exerted in the design of the switching converter for the charge application through the accurate estimation of the output current ripple value. This study proposes a method to reduce the output current ripple of the converter and presents a detailed analysis of the output current ripple of the DC-DC boost converter to provide a guideline for the design of the battery charger.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.326-329
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• 2002

The dc reactor type superconducting fault current limiter is composed of a power converter, magnetic core reactors and a do reactor that is a superconducting coil. When a fault occurs, the dc reactor maintains the stability of system by limiting its fault current. In this study, we focus on the design of the dc reactor using FEM(Finite Element Method). In order to design it, various elements should be considered such as magnetic field intensity, Lorentz's force, its inductance and so forth. Firstly, we forecast the values of those elements from the simulation of FEM and then measured with a copper wire magnet. Finally, verify the reliability of this FEM method by comparing with two results.

• Proceedings of the KIEE Conference
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• 1998.07c
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• pp.1231-1234
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• 1998

Design & Operation of power system for meeting increase of electric power demand is becoming more difficult and complex. One of reasons is increase of fault current. As one of the most effective methods for suppressing the fault current, installation of SFCL is expected. This paper describes a method of fault analyses of power system with SFCLs, and also discusses determination of specification of SFCLs, effects of limiting the fault current due to SFCLs by use of the model system of two - bus electric power system with parallel circuit model transmission line. Also, describes the definition of six specific parameters of SFCL for power system application & a proposal of design method of specific parameter of a resistance type SFCL in overhead transmission lines considering operation of protective relays.

• Journal of Power Electronics
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• v.7 no.3
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• pp.238-245
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• 2007

This paper considers the problem of regulating the output voltage of a current doubler rectified asymmetric half-bridge (CDRAHB) DC/DC converter via fuzzy integral control. First, we model the dynamic characteristics of the CDRAHB converter with the state-space averaging method, and after introducing an additional integral state of the output regulation error, we obtain the Takagi-Sugeno (TS) fuzzy model for the augmented system. Second, the concept of parallel distributed compensation is applied to the design of the TS fuzzy integral controller, in which the state feedback gains are obtained by solving the linear matrix inequalities (LMIs). Finally, numerical simulations of the considered design method are compared to those of the conventional method, in which a compensated error amplifier is designed for the stability of the feedback control loop.

• Journal of The Korean Digital Architecture Interior Association
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• v.11 no.1
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• pp.91-98
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• 2011

This study is to concern about the effort of architectural practice to realize the sustainable architecture. It is necessary to know about the integrated design method which combines the passive design method with the active design method from the initial design phase. One case study is followed to explain the method. Integrated design starts from defining the project and goal setting, site evaluation, design concept, design optimization, documents and specifications, bidding and construction and post occupancy evaluation followed respectively. In order to construct the sustainable design, sophisticated understanding about nature and its' principle is important and adaptable application of nature and climate depending on location is followed. In conclusion, architects and specialists of sustainable design should make an effort more study.

• Progress in Superconductivity and Cryogenics
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• v.5 no.3
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• pp.26-29
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• 2003

Nowadays, one of the serious problems in KEPCO system is much higher fault current than the SCC(Short Circuit Capacity) of circuit breaker. As the superconductivity technology has developed, the HTS-FCL(High Temperature Superconductor-Fault Current Limiter) can be one of the attractive alternatives to solve the fault current problem. But the parameters of HTS-FCL should be designed optimally to have the best performance. Under this background, this paper presents the optimal design method of parameters for resistive type HTS-FCL using Monte Carlo technique.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.33 no.2
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• pp.76-82
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• 1984

This paper presents the design and the optimal control method of current-fed half-brige switching regulator. To achieve fast response load current variation is fed to control input, and simple optimal control model has been derived with provision of current control loop in the control circuit. Test results show that the control system model is correct and 5ms response time has been obtained at 25 KHz switching frequency.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.39 no.7
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• pp.680-691
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• 1990

In this paper the conventional resonant inverters are compared and a novel parallel resonant dc pulse inverter for high performance motor drive system is proposed. The design method and related equations for the novel resonant inverter are derived. Also, a current controller for the resonant inverter is proposed and compared with PI current controller of the conventional PWM inverter by analog simulation. The novel resonant inverter and the current controller are implemented to verify the suggested design principles. The analog simulation and the experimental results shown the satisfactory operation of the proposed inverter and the controller.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.365-368
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• 2002

The design of industrial arc plasma systems is still largely based on trial and error although the situation is rapidly improving because of the available computational power at a cost which is still fast coming down. The desire to predict the behavior of arc plasma system, thus reducing the development cost, has been the motivation of arc research. To interrupt fault current, the most enormous duty of a circuit breaker, is achieved by separating two contacts in a interruption medium, $SF_{6}$ gas or air etc., and arc plasma is inevitably established between the contacts. The arc must be controlled and interrupted at an appropriate current zero. In order to analyze arc behavior in $SF_{6}$ gas circuit breakers, a numerical calculation method combined with flow field and electromagnetic field has been developed. The method has been applied to model arc generated in the Aachen nozzle and compared the results with the experimental results. Next, we have simulated the unsteady flow characteristics to be induced by arcing of AC cycle, and conformed that the method can predict arc behavior in account of thermal transport to $SF_{6}$ gas around the arc, such as increase of arc voltage near current zero and dependency of arc radius on arc current to maintain constant arc current density.