• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.12
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• pp.22-31
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• 2000

A new analysis method of Tap-011 for CATV and DBS systems was proposed and investigated by using 4-port and 3-port equivalent circuits. As an analysis method the even odd-mode theory for a symmetrical coupled-line directional coupler was introduced, and then it was applied to transformer type directional coupler. By comparing the results of simulation and measurement, the validity of the proposed analysis method was confirmed. Furthermore, the Tap-off has been broadened from 5 MHz to 2.500 MHz by adopting the proposed theory.

• Journal of the Korean Electrochemical Society
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• v.8 no.3
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• pp.117-124
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• 2005

Electrochemical oxidation of ethanol at nickel electrodes has been studied in 1 M KOH solution containing 0.20M ethanol using electrochemical impedance spectroscopy. Equivalent circuits have been worked out by simulating the impedance data, and the results were used to model the oxidation of ethanol as well as the passivation of the electrode. The maximum rate of oxidation of $Ni(OH)_2$ to NiOOH was observed at about 0.37V vs. Ag/AgCl reference electrode, while the maximum rate of ethanol oxidation at the Ni electrode was observed at about 0.42V, The charge-transfer resistance for oxidation of the electrode itself became smaller in the presence of ethanol than in its absence. These results suggest that the $\beta-Ni(OH)_2/\beta-NiOOH$ redox couple is acting as an effective electron transfer mediator far ethanol oxidation. The kinetic parameters also were obtained by the experimental and simulated results.

• Journal of Power Electronics
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• v.7 no.3
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• pp.246-256
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• 2007

In this paper, a novel type auxiliary active edge resonant snubber assisted zero current soft switching pulse modulation Single-Ended Push Pull (SEPP) series load resonant inverter using IGBT power modules is proposed for cost effective consumer high-frequency induction heating (IH) appliances. Its operating principle in steady state is described by using each switching mode's equivalent operating circuits. The new multi resonant high-frequency inverter with series load resonance and edge resonance can regulate its high frequency output power under a condition of a constant frequency zero current soft switching (ZCS) commutation principle on the basis of the asymmetrical pulse width modulation (PWM) control scheme. Brand-new consumer IH products using the proposed ZCS-PWM series load resonant SEPP high-frequency inverter using IGBTs is evaluated and discussed as compared with conventional high-frequency inverters on the basis of experimental results. In order to extend ZCS operation ranges under a low power setting PWM as well as to improve efficiency, the high frequency pulse density modulation (PDM) strategy is demonstrated for high frequency multi-resonant inverters. Its practical effectiveness is substantially proved from an application point of view.

• Journal of Power Electronics
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• v.6 no.2
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• pp.95-103
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• 2006

In this paper, a novel prototype of auxiliary switched capacitor assisted voltage source soft switching PWM Single-Ended Push Pull (SEPP) series capacitor compensated load resonant inverter with two auxiliary edge resonant lossless inductor snubbers is proposed and discussed for small scale consumer high-frequency induction heating (IH) appliances. The operation principle of this inverter is described by using switching mode equivalent circuits. The newly developed multi resonant high-frequency inverter using trench gate IGBTs can regulate its output AC power via constant frequency edge-resonant associated soft switching commutation by using an asymmetrical PWM control or duty cycle control scheme. The brand-new consumer IH products which use the newly proposed edge-resonant soft switching PWM-SEPP type series load resonant high-frequency inverters are evaluated using power regulation characteristics, actual efficiency vs. duty cycle and input power vs. actual efficiency characteristics. Their operating performance compared with some conventional soft switching high-frequency inverters for IH appliances is discussed on the basis of simulation and experimental results. The practical effectiveness of the newly proposed soft switching PWM SEPP series load resonant inverter is verified from an application point of view as being suitable for consumer high-frequency IH appliances.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.1
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• pp.69-78
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• 2014

In this paper, characteristics of wireless power transfer (WPT) systems using magnetically coupled resonance scheme with relay coils are investigated and modeled. Especially, asymmetric frequency splitting characteristics in over-coupled region of WPT with relays are measured and accurately modeled. Transmitter, receiver, and relay coils are modeled with R, L, C equivalent circuits. Using these circuit models and mutual inductances between coils, a WPT system is described with a linear matrix equation. For under-coupled region, a matrix is simplified considering only mutual inductances between adjacent coils. An analytical transfer characteristic of WPT system vs. distance is extracted using an inverse matrix that is acquired by Gauss elimination method for the simplified matrix. For over-coupled region, a matrix considering mutual inductances between non-adjacent coils is used to predict a frequency splitting characteristics accurately. A 6.3MHz WPT system with relay coils is implemented and measured. An accuracy of the model is investigated by comparing the output of the model with the measured results.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.207.1-207.1
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• 2013

Tantalum oxide has been extensively investigated as one of the promising Resistive switching materials applicable to Resistive Dynamic Access Memories. Impedance spectroscopy offers simultaneous measurements of electrical and dielectric information, separation of electrical origins among bulk, grain boundaries, and interfaces, and the monitoring of electrical components. Such benefits have been combined with the resistive states of resistive switching devices which can be described in terms of equivalent circuits involving resistors, capacitors, and inductors, The current work employed pulsed laser deposition in order to prepare the oxygen-deficient tantalum oxide. The fabricated devices were controlled between highresistance and low-resistance states in controlled current compliance modes. The corresponding electrical phenomena were monitored both in the dc-based current-voltage characteristics and in the ac-based impedance spectroscopy. The origins of the electrical switching are discussed towards optimized ReRAM devices in terms of interfacial effects.

• Journal of Power Electronics
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• v.17 no.6
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• pp.1500-1511
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• 2017

The purpose of this paper is to study a high-performance control scheme for neutral-point-clamping three-level (NPC-3L) inverter fed dual three-phase permanent magnet synchronous motor (PMSM) drives by considering some asymmetric factors such as the non-identical parameters in phase windings. To implement this, the system model is analyzed for dual three-phase PMSM drives with asymmetric factors based on the vector space decomposition (VSD) principle. Based on the equivalent circuits, PI controllers with feedforward compensation are used in the d-q subspace for regulating torque, where the cut-off frequency of the PI controllers are set at the twice the fundamental frequency for compensating both the additional DC component and the second order component caused by asymmetry. Meanwhile, proportional resonant (PR) controllers are proposed in the x-y subspace for suppressing the possible unbalanced currents in the phase windings. A dual three-phase space vector modulation (DT-SVM) is designed for the drive, and the balancing factor is designed based on the numerical fitting surface for balancing the DC link capacitor voltages. Experimental results are given to demonstrate the validity of the theoretical analysis and the proposed control scheme.

• Journal of Power Electronics
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• v.19 no.6
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• pp.1413-1428
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• 2019

In this paper, a novel zero-voltage and zero-current switching (ZVZCS) interleaved two switch forward converter is proposed. By using a coupled-inductor-type smoothing filter, a snubber capacitor, the parallel capacitance of the leading switches and the transformer parasitic inductance, the proposed converter can realize soft-switching for the main power switches. This converter can effectively reduce the primary circulating current loss by using the coupled inductor and the snubber capacitor. Furthermore, this converter can reduce the reverse recovery loss, parasitic ringing and transient voltage stress in the secondary rectifier diodes caused by the leakage inductors of the transformer and the coupled inductance. The operation principle and steady state characteristics of the converter are analyzed according to the equivalent circuits in different operation modes. The practical effectiveness of the proposed converter was is illustrated by simulation and experimental results via a 500W, 100 kHz prototype using the power MOSFET.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.12
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• pp.963-968
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• 2018

In this paper, a compact common mode filter using passive elements is designed and fabricated. To design a common mode filter with required frequency response, the equivalent circuits of the common mode filter in differential mode and common mode were analyzed. Compared with the former filter using a ${\lambda}/4$ resonator, the size of the proposed structure was reduced by 60 %. The fabricated common mode filter has a maximum differential mode insertion loss of 1.2 dB and a minimum common mode absorption efficiency of 78.2% in the CMA - bandwidth of 27.5 %.

• Progress in Superconductivity and Cryogenics
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• v.12 no.1
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• pp.61-65
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• 2010

To develop the thermal analysis method for the thermal behavior of HTS power cable system, cooled with sub-cooled liquid nitrogen, new thermo dynamic model for HTS cable system is introduced. The introduced thermal model is mainly modified from the thermal circuit following to IEC60287 for underground power cable systems such as XLPE or paper wrapped insulation cables. The thermal circuits for HTS cables are similar to the forced cooled underground cable system but the major thermal parameters and the configuration is apparently different to the normal cable systems so there has been no proposals in this field of analysing method. In this paper, 154kV HTS cable system has been introduced as an aspects of thermal models and a thermal circuit is proposed for the fundamentals on the dynamic rating systems for the HTS cable system. By using the thermal circuit developed in this paper, the optimal controls on the sub-cooling system's capacity become possible and it is expected to make the efficiency of HTS cable higher than conventional static controls.