• Journal of the Korea Society of Computer and Information
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• v.17 no.2
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• pp.23-29
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• 2012

To recently, light of the sun and fuel cell etc. which is new and renewable energy is developed with the direct current energy source mostly. And it is necessary that the utilization plan which does supply it properly. In this case, the direct current illumination system can be a typical alternative of it. The system similar to the development system is composed of type which connects to each other the photovoltaic pannel, the charge kit, and the battery bank. I develop all-in-one system which the power supply system and photovoltaic pannel which can charge and use efficiently. Additionally, I exploit the DC lamp module of three wave which can separate the electronic ballasts from the module. Developed the DC Lamp module of all-in-one which can turn on or can turn off, by operation of ON/OFF button. It can be used semipermanently by changing just only electronic ballasts.

• Journal of Electrical Engineering and Technology
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• v.13 no.6
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• pp.2441-2446
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• 2018

This paper presents a radio frequency-to-direct current (RF-to-DC) converter for special RF power harvesting application at 915 MHz. The major featured components of the proposed RF-to-DC converter is the combination of a cross-coupled rectifier and an active diode: first, the cross-coupled rectifier boosts the input voltage to desired level, and an active diode blocks the reverse current, respectively. A prototype was implemented using $0.18{\mu}m$ CMOS technology, and the performance was proven from the fact that the targeted RF harvesting system's full-operation with higher power efficiency; even if the system's input power gets lower (e.g., from nominal 0 to min. -12 dBm), the proposed RF-to-DC converter constantly provides 1.47 V, which is exactly the voltage level to drive follow up system components like DC-to-DC converter and so on. And, maximum power conversion efficiency is 82 % calculated from the 0 dBm input power, 2.3 mA load current.

• Journal of Korea Society of Industrial Information Systems
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• v.29 no.3
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• pp.41-49
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• 2024

In this paper, we validate simulation results for the design optimization of a Superconducting Fault Current Limiter (SFCL) intended for use in Medium Voltage Direct Current systems (MVDC). With the increasing integration of renewable energy and grid connections, researchers are focusing on medium-voltage systems for balancing energy in new and renewable energy networks, rather than traditional transmission or distribution networks. Specifically, for DC distribution networks dealing with fault currents that must be rapidly blocked, current-limiting systems like superconducting current limiters offer distinct advantages over the operation of DC circuit breakers. The development of such superconducting current limiters requires finite element analysis (FEM) and an extensive design process before prototype production and evaluation. To expedite this design process, the design outcomes are assimilated using a Reduced Order Model (ROM). This approach enables the verification of results akin to finite element analysis, facilitating the optimization of design simulations for production and mass production within existing engineering frameworks.

• Journal of Power Electronics
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• v.6 no.2
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• pp.146-162
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• 2006

This paper deals with the analysis, design and implementation of an AC-DC Zeta converter in discontinuous current mode (DCM) of operation used for power quality improvement at AC mains in direct torque controlled (DTC) permanent magnet synchronous motor (PMSM) drives. The designed Zeta converter feeds a direct torque controlled PMSM drive system. Modeling and simulation is carried out in a standard PSIM software environment. Test results are obtained on the developed prototype Zeta converter using DSP ADMC401. The results obtained demonstrate the effectiveness of the Zeta converter in improving power quality at AC mains in the PMSM drive system.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.161-162
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• 2015

최근 세계적으로 전력계통의 대륙 간 연계나 신재생에너지, 분산전원의 계통 연계를 위해 HVDC(High voltage Direct Current)에 대한 연구가 활발히 진행되고 있다. 대용량, 장거리 송전이 필요한 경우 HVAC에서의 전력손실과 송전거리의 한계를 극복하기 위하여 HVDC가 새로운 대안으로 떠오르고 있으며, LCC(Line commutated Converter)와 VSC(Voltage Source Converter)의 기술발전이 비약적으로 이뤄지고 있다. 특히, DC Grid화를 위해서 유럽에서는 해상풍력을 연계한 Windfarm을 DC Grid화 하는 프로젝트가 활발히 진행되고 있다. 이러한 신재생 에너지의 계통 연계를 위해서 DC Grid가 본격적으로 논의가 되고 있고 관련분야에서는 기술개발을 앞다퉈 진행하고 있는 상황이다. DC Grid 구현을 위해 VSC HVDC가 최근 주목받고 있으며, VSC로 연계된 DC Grid의 AC 계통과의 연계를 위해 가장 필요한 것이 바로 DC 차단기라고 할 수 있겠다. 본 논문에서는 DC Grid의 고장분석을 위한 기초연구로써 MMC(Modular Multilevel Converter) VSC를 기반으로 한 Point-to-Point HVDC Grid에서의 DC 고장에 대한 분석을 실시하였으며 그 특징을 분석하였다.

• Korean Journal of Metals and Materials
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• v.48 no.11
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• pp.1014-1020
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• 2010

In order to improve the purity on deposit in cobalt electrowining, a fundamental study using Pulse-Reverse Current (PRC) was carried out. Based on a sulfate solution, Cu, Ni, and Fe as impurities were added during cobalt electrowinning. There were four reverse waveforms and frequency conditions from 1 Hz to 10 kHz, and the purity of each condition was compared with the Direct Current (DC) purity. From the results, it was found that the anodic potential induced by reverse current affects selective dissolution of impurities. In this work, the case of the highest reverse peak current density ($I_r$) with a short reverse time ($t_r$) at 100 Hz showed a higher purity than that of the DC. This PRC condition also showed only a 4% low current efficiency comparable to the DC. We concluded that an optimized PRC for cobalt electrowinning could improve the purity with little loss of current efficiency.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.5
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• pp.198-201
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• 2005

Carbon nanofibers were formed on silicon substrate which was applied by negative direct current (DC) bias voltage using microwave plasma-enhanced chemical vapor deposition method. Formation of carbon nanofibers were varied according to the variation of the applied bias voltage. At -250 V, we found that the growth direction of carbon nanofibers followed the applied direction of the bias voltage. Based on these results, we suggest one of the possible techniques to control the growth direction of the carbon nanofibers.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.3
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• pp.69-72
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• 2012

It is well known that speed of a direct current shunt motor is inverse proportional to flux. This paper presents speed expression to show that speed is not inverse proportional to flux. The presented speed vs. flux curves are verified by experimental result that shows the need of the revision of speed vs. flux curves shown in conventional text books.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.128-131
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• 2000

The main objective of this paper is to design and test a new type of polymer ZnO surge arrester for DC power system of railroad vehicles. The rated voltage is 1500V direct current. The main research works are focused on structure design by finite element method, rating voltage, temporary over voltage and studies of characteristics of polymeric surge arrester.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.1912-1917
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• 2010

Fiber Reinforced Plastic (FRP) insulators for direct current (DC) were developed and their electrical characteristics were investigated. Electrical tests were carried out to measure withstanding and flashover voltages under common use frequency condition. Tensile and bending tests were performed for the mechanical characteristics. The test results showed that DC FRP insulators had superior voltage resistances and strengths to porcelain insulators.