• Journal of the Korean Vacuum Society
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• v.15 no.6
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• pp.587-593
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• 2006

The circuit of the EEFL system and the inverter has been analyzed into the resistance RL, the capacitance C of the EEFL-backlight system, and the inductance of transformer in the inverter. The lamp resistance and capacitance are deter-mined from the phase difference is between the lamp current and voltage and from the Q-V diagram, respectively. The single Lamp of EEFL for 32' LCD-BLU has the resistance of $66\;k\Omega$ and the capacitance of 21.61 pF. The resistance, which is connected by parallel in the 20-EEFLS BLU, is $3.3\;k\Omega$ and the capacitance is 402.1 pF. The matching frequency in the operation of lamp system is noted as $\omega_M=1/\sqrt{L_2C(1-k^2)}$, where $L_2$ is the inductance of secondary coil and k is the coupling coefficient between primary and secondary coil. The lamp current and voltage has maximum value at the matching frequency in the LCD BLU system. The results of analytic solutions are in good agreement with the experimental results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.3
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• pp.399-409
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• 1998

In this paper, the broad-band design theory for weakly-coupled Tap-Off for CATV systems has been described and the transmission line impedance matching method has been proposed. The fabricated weakly-coupled Tap-Offs based on the above theory and method have been much improved in the frequency characteristics compared with conventional ones. Thus, the useful bandwidth of weakly-coupled Tap-Offs have been extended from 5 to 2000 MHz. It is also recognized that turn numbers of the coils composing the transformer are not integers but 0.9, 1, 1.9, 2, 2.9, etc., in the actual circuits. Further, the practical measurements of the frequency characteristics for a fabricated weakly-coupled Tap-Off show very good agreements with theoretical results, and hence, the validity of the proposed design theory and transmission line impedance matching method have been confirmed.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.502-504
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• 1994

This paper describes an induction heating system which is full-bridge parallels resonant inverter. This system consists of current-fed type inverter, and a parallels resonant circuit with a matching transformer. A parallels resonant scheme is employed, and operating range of the proposed circuit with operating frequency and load parameter is demonstrated from the result of steady state. Also, this equipments testing result introduces, good efficiency and reliability of the system. Finally, this paper experimental results are given.

• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.405-407
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• 2010

Simple equivalent circuit model is developed for wireless energy transfer system via coupled magnetic resonances and practical design method is also provided. Node equations for the resonance system are built with the method expanding transformer's equations and the optimum distances of coils in the system is derived analytically for optimum coupling coefficients for high transfer efficiency. Moreover, to calculate the frequency characteristics for a lossy system the equivalent model is established at an electric design automation tool. The model parameters of the actual system are extracted and the results of modeling are compared with the measurement. Through the developed model, we can understand the principles that the system shows higher efficiency than conventional magnetic coupling systems and impedance matching is important to achieve high efficiency.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.6
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• pp.522-529
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• 2014

This study proposes an isolation amplifier circuit for the sensing and feedback of inverter DC-link voltage, which is inevitable for the precise control of inverter output voltage. The isolation amplifier consists of a pulse-width modulator and a pulse transformer with dual secondary windings. The accuracy of the proposed circuit depends on the precise matching of filter parameters in dual secondary circuits. The influences of parameter inaccuracy on the amplifier performances are analyzed. A modified circuit is proposed to reduce the dependency on filter parameters. The validity of the proposed method is verified through simulation and experiment.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.1
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• pp.108-114
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• 2008

Recently, there have been several instances that the nuclear power plants were shut down due to the mechanical faults in the main transformer of the plants. These mechanical faults are primarily originated from the electromagnetically induced mechanical vibrations. Magnetostriction is identified to be the main cause of the mechanical vibration after analyzing the vibration data of the main transformers in nuclear power plants. In this study, we derived a mathematical model of the magnetostriction based on the Jiles-Atherton hysteresis model. The validity of the model is checked by matching the simulations with the experimental observations. The magnetostriction model used in this study will be the first step toward developing a design tool far the transformers that have minimal mechanical vibrations and are robust to mechanical faults.

• Journal of Electrical Engineering and Technology
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• v.9 no.4
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• pp.1365-1368
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• 2014

A CPW-fed to CPS dipole antenna of triangular loop director by microstrip tapered balun is proposed for dual and wide band operations, in this paper. The proposed antenna is consisted of a CPW-fed to CPS transform, microstrip tapered balun element, CPS dipole driver and triangular loop director. A dual and wide bandwidth of the proposed dipole antenna is realized by introducing the triangular loop director and taper matching element. The operated frequency bandwidth is 1GHz (2.14~3.14 GHz) and 1.9 GHz (4.6~6.5 GHz) to return loss criterion of less than 10 dB. The measured return loss of the proposed antenna showed good results of the dual and wide band operating frequency and the radiation pattern. The proposed antenna is able to support WLAN wireless communications applications.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.689-691
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• 1993

This paper describes an induction heating system which is developed for CRT manufacturing. This system consists of a buck chewer, a voltage source full-bridge inverter, and a series resonant circuit with a matching transformer. A series resonant scheme is employed, and operated at the zero phase of the resonant load by PLL. This ensures maximum power transfer, good efficiency and reliability of the system. Implementation of a prototype rated of 3 kW 450 kHz is described and experimental results are given.

• Analytical Science and Technology
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• v.21 no.3
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• pp.201-211
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• 2008

The treatment efficiency of PCBs containing wastes has been investigated. The samples treated by electron beam and de-chlorination method were analyzed to verify the byproducts before treatment and after treatment. In the treated samples by electron beam irradiation, PCBs were not detected by comparing the peak matching using the Korean official waste test method. On the other hand, PCBs congeners were detected by analyzing individual isotope method using HRGC/HRMS. Most of PCB congeners in waste were decomposed to 3-chlorobiphenyls, lower chlorinated congener produced during the treatment of electron beam. In the chemical dechlorination treatment, it was found that the concentrations of PCBs in treated samples were lower than those of regulation criteria in Waste & POPs management law and the after treatment concentration were satisfied to the regulation criteria. Also, dioxins were not observed after the physio-chemical treatment processes of PCBs containing wastes.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.5
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• pp.562-571
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• 2008

In this paper, we propose a novel structure of a spiral antenna with a CP characteristic for RFID reader in UHF band. Since the proposed antenna can be built by printing on a FR-4 substrate, it is appropriate for low-cost mass-production. The antenna is designed to operate in UHF band of $860{\sim}960$ MHz. The CP bandwidth is Increased enough to cover an overall UHF RFID band by using a spiral structure for the antenna arm. The matching bandwidth is broadened by using a quarter-wave transformer between the fred and the antenna body. The proposed antenna has advantages of its easy gain and pattern control with a small antenna size. The measured antenna performance shows the matching bandwidth of 13%, the CP bandwidth of 23%, and the gain of 6.5 dBi. This verifies that the proposed antenna is appropriate for RFID antennas in UHF band.