• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.8
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• pp.6-14
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• 2006

This paper is a study about a proper method of plasma generation to cleaning method and a high frequency power equipment circuit to generation of plasma that used cleaning of chamber for TFT-LCD PECVD. The high density plasma required for cleaning causes a possibility of high density plasma more than $1{\times}10^{11}[EA/cm^3]$. It apply a ferrite core of ferromagnetic body to a existing ICP form. In case of power transfer equipment on 400[kHz] high frequency to generation of plasma it makes certain a stable switching operation in condition of plasma through using a inverter form for general purpose HB. And it demonstrates the performance of power transfer equipment using methods of measurement which use a transformer of series combination the density of plasma and the rate of dissolution of $NF_3$ in condition of $A_r\;and\;NF_3$.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.951-953
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• 2015

Learning for thinking says the behavior of the organism changes as a result of practice or experience. It is very difficult to identify focusing ability objectively when students study. But, brain of the body is not so. EEG signal means continuously electric records of brain potential variation between two points on the scalp when brain activities take place. In types of EEG, there are delta(0~4Hz), theta(4~8Hz), alpha(8~13Hz), beta(13~30Hz) and gamma waves(30~50Hz). SMR waves and Mid-beta waves appear when focused for studying. Part for the most influence on concentrating reported that Mid-beta waves. In relation to brain activities, EEG has been actively researched for evaluating brain focus index system during learning and study. So, By using Biopac system for this study, measured brain wave was converted into FFT for extracting Mid-beta domain signals that are related to learning after giving focus invoked subjects to a small number of people. When concentrating, we measured the change in the power of the Mid-beta frequency domain and presented a correlation. Based on these results, we analyzed whether students are concentrated objectively on learning or not. and hope to offer more efficient learning method.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.9
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• pp.843-852
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• 2009

In this paper, we present design, fabrication, and measured results for a frequency upconverter for a wireless communication system of UAV(Unmanned Aerial Vehicle). The specifications of such wireless communication system requires the special features of maximum range of communication as well as deployment in UAV and repairing. The frequency upconverter operating at $5.25{\sim}5.45\;GHz$ in C-band was designed and fabricated considering such special features. The AGC function was included because the required output power should be constant for optimal system operation. The fabricated upconverter showed a constant output power of $+2{\pm}0.5\;dBm$ for the $-15{\sim}-10\;dBm$ input. Spuriouses were below -60 dBc and the adjacent leakage power was below -40 dBc. In addition, LO sources in the upconverter was implemented using the frequency synthesizer with step 1 MHz. This is for the application to the situation where multiple UAVs employed and the possible change of the permitted frequency band. The synthesizer showed a phase noise of -100 dBc/Hz at the 100 kHz frequency offset.

• Journal of Power Electronics
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• v.16 no.3
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• pp.861-871
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• 2016

With high penetration of renewable energies, power electronic transformers (PETs) will be one of the most important infrastructures in the future power delivery and management system. In this study, an isolated bidirectional modular multilevel DC/DC converter is proposed for PET applications. A modular multilevel structure is adopted as switching valves to sustain medium voltages to achieve modular design and high reliability. Only one high-frequency transformer is used in the proposed converter, which significantly simplifies the circuit and galvanic insulation design. A dual-phase-shift modulation strategy is proposed to regulate the output power and achieve a simple voltage balancing control. A down-scaled (2 kW/20 kHz) prototype is constructed to demonstrate the proposed converter and verify the control strategy. The experimental results comply with the theoretical analysis well, with the highest power efficiency reaching 97.6%.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.4
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• pp.384-394
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• 1999

This paper deals with a fixed frequency full-bridge inverter type DC-DC high-power converter with high frequency high voltage(HFHV) transformer-coupled stage, which operates under quasi-resonant ZVS transition priciple in spite of a wide PWM-based voltage regulation processing and largely-changed load conditions. This multi-resonant(MR) converter topology is composed of a series capacitor-connected parallel resonant tank which makes the most of parasitic circuit reactive components of HFHV transformer and two additional quasi-resonant pole circuits incorporated into the bridge legs. The soft-switching operation and practical efficacy of this new converter circuit using the latest IGBTs are actually ascertained through 50kV trially-produced converter system operating using 20kHz/30kHz high voltage(HV) transformers which is applied for driving the diagnostic HV X-ray tube load in medical equipments. It is proved from a practical point of view that the switching losses of IGBTs and their electrical dynamic stresses relating to EMI noise can be considerably reduced under a high frequency(HF) switching-based phase-shift PWM control process for a load setting requirements.

• Proceedings of the KIEE Conference
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• 1997.07f
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• pp.1924-1926
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• 1997

With the development of power electronics, many new energy storage systems such as the superconducting magnetic energy storage, the flywheel energy storage, and the capacitive energy storage, etc. are being intensively studied recently in order to replace battery in some special applications, Among these innovative energy storage systems, the flywheel system exhibits some unique features such as high power density, easy maintenance and longer lifetime. This paper introduces the novel flywheel energy storage system. Operation and features of the system are illustrated and verified on a 6kVA, 20kHz IPM based experimental circuit for O/A application. The Halbach Array Motor is selected of the design of the three phase motor/generator for the flywheel energy storage system.

• Proceedings of the IEEK Conference
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• 2001.06a
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• pp.189-192
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• 2001

In this paper, We designed and implemented 20 watt high power amplifier which can be used for the commercial services in band of 1.86 ~ 1.870Hz at PCS. In order to satisfy ACPR, We designed by using the ADS(Advanced Design System)ver1.3. The HPA is fabricated on tepron substrate($\varepsilon_{{\gamma}}$ =3.15, H=0.78mm, T=0.02mm). The implemented HPA measured The ACPR characteristics at $\pm$ 885kHz, $\pm$ 1.25MHz, $\pm$2.25MHz. The HPA meets specification with good ACPR. The HPA is expected to use as a commercial product of PCS base station.roduct of PCS base station.

• Journal of Electrical Engineering and Technology
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• v.8 no.1
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• pp.137-143
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• 2013

This paper presents development of variable speed generation (VSG) system with energy saving function. The rubber tyred gantry crane (RTGC) requires the power from diesel-engine. Significant fuel savings by reducing the engine speed can be achieved, because all of operation modes except hoisting are required lower power than rated value of engine. When low speed operation output voltage of generator is decrease until acceptable range of motor driver inverters and auxiliary load supplier. According to power demand engine speed is varying from 20 to 60Hz, and voltage is varying between 210Vac and 480Vac. When idle mode or low power operation dc/dc converter operates by constant output voltage control and inverters dc site voltage is compensated by it. This paper proposed 3-phase interleaved boost converter which has the same structure as the commercially available 3-phase inverter and current sharing capability. 400kW interleaved converter is designed and a performance of converter is evaluated through several experiments with a RTGC system. Energy saving VSG system can cut down fuel consumption by 36% and 21.3% at idle and unidirectional load operations.

• Journal of Power System Engineering
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• v.20 no.3
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• pp.29-35
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• 2016

Because of the severe service environment of the large marine vessel, the fatigue strength and its evaluation play an important role in design and maintenance of marine crankshaft. The aim of this work is to investigate the probability distribution of fatigue lives in crank throw forged steel and to develop the methodology for estimation of the probabilistic design fatigue strength. Detailed studies were performed on the constant amplitude axial loading fatigue test. The experiments were controlled by stress ratio of -1 and 15Hz frequency for each stress level. The considerable variability of fatigue life was observed in each stress level under rigidly controlled constant fatigue testing conditions. The fatigue life of crank throw forged steel was well followed the log-normal and Weibull distribution. In addition, it can be used for the estimation of probabilistic design fatigue strength by using the proposed methodology.

• Journal of Satellite, Information and Communications
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• v.12 no.2
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• pp.33-37
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• 2017

This paper suggests a new reliable push pull converter. The proposed push-pull converter have additional two diodes comparing with conventional push-pull converter. When one of two MOSFETs of the push-pull converter is on state, the other MOSFET is automatically off state due to adding additional diodes. Therefore, the converter is under electric noise environments, the converter avoids short circuit due to turning on of two MOSFETs. In this paper, the suggested converter has been simulated by PLECS software for 100 kHz switching frequency. In simulation, the current of the converter switches increases about 10 % for $20{\mu}sec$ electric noise environments. However, the converter operates very reliably without any short circuit conditions.