• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.6
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• pp.569-575
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• 2003

This paper present a new fully-automated PC-based instrumental system that could quickly measure and analyze the efficiency of switching power supplies for the entire operating range. In the proposed system, we applied an Indirect method for high-voltage low-current measurements and a direct method for low-voltage high-current measurements, in order to obtain a high accuracy with minimum equipment requirement. Compared to the conventional methods, the newly proposed system offers more accurate and much faster real-time assessment of the efficiency with minimum measurement error. The performance and accuracy of the proposed system are verified using a 50 W switching power supply intended for telecommunication applications.

• Journal of The Korean Society of Integrative Medicine
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• v.9 no.4
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• pp.105-117
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• 2021

Purpose : This study examined the effect of transcranial direct current stimulation (tDCS) combined high intensity interval training (HIIT) on the aerobic exercise capacity of college soccer players. Methods : The subjects of this study were 30 college soccer players. They were divided into a high intensity interval training group combining transcranial direct current stimulation (Group I) and a high intensity interval training group (Group II). Each group had 15 subjects randomly assigned. After receiving general soccer training, each group additionally received high intensity interval training combined with transcranial direct current stimulation and high intensity interval training for 30 minutes 5 times a week for 8 weeks. Their VO₂max and 20 meter shuttle run test, Yo-Yo intermittent recovery test were analyzed before the intervention. After 8 weeks of intervention, the above items were re-measured and an intergroup analysis was performed. Results : As a result of comparative analysis of VO₂max intake between groups, 20 meter shuttle run test and Yo-Yo intermittent recovery test, a statistically significant difference was found. The high intensity interval training group (Group I) combined with transcranial direct current stimulation showed a significant difference in aerobic exercise capacity compared to the high intensity interval training group (Group II). Conclusion : These results showed that high intensity interval training group combined with transcranial direct current stimulation was more effective for aerobic exercise. Based on this study, this study proposes an effective program for patients as well as elite athletes. In the future, it is necessary to develop an effective transcranial direct current stimulation program and to study how to apply it for various patients.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.6
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• pp.452-458
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• 2019

This study proposes a new test circuit and control method for the submodules of modular multilevel converter (MMC)-based HVDC systems. The test current of conventional submodule test circuits cannot provide the DC offset components or may have some distortion in the linearized current with the DC offset. The proposed scheme can provide not only the DC component but also linearized current without distortion. Therefore, the submodule test current waveform is relatively similar to that of a real submodule consisting of an MMC-based HVDC system. The validity of the proposed circuit and control method is verified through a simulation and experiment.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.192-194
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• 2018

In this paper a new single-stage ac-dc converter with high frequency isolation and low components count is introduced. The proposed converter is constructed using two interleaved boost circuits in the grid side and non-regulating full bridge in the DC side. An optimized switching is implemented on the two interleaved boost circuits resulting in a ripple-free grid current without a ripple cancellation network; hence very small filter inductors are used. A simple and reliable closed-loop control system is easily implemented, since the phase-shift angle is the only independent variable. Moreover, current imbalance is avoided in the presented topology without current control loop in each phase. The proposed charger charges the battery with a sinusoidal-like current instead of a constant direct current. ZVS turn on of all switches is achieved throughout the operation in both directions of power flow without any additional components.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.6
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• pp.117-125
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• 2007

Recently, a fuel cell with low voltage and high current output characteristics is remarkable for new generation system. It needs both a DC-DC step-up converter and DC-AC inverter to be used in fuel cell generation system. Therefor, this paper, consists of an isolated DC-DC converter to boost the fuel cell voltage 380[VDC] and a PWM inverter with LC filter to convent the DC voltage to single-phase 220[VAC]. Expressly, The fuel cell system which it proposes DC-DC the efficient converter used PWM the phase transient control law and it depended to portion resonance ZVS switching, loss peek voltage and electric current of realization under make schedule, switching frequency anger and the switch reduction. And mind benevolence it sprouted 2 in stop circuit and it added and a direct current voltage and the electric current where the ingredient is reduced in load side ripple stable under make whom it will be able to supply. Besides the efficiency of 92[%]is obtained over the wide output voltage regulation ranges and load variations. Also, under make over together the result leads simulation and test, the propriety confirmation.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.7
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• pp.1221-1225
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• 2010

The application of the AC and DC lines on the same transmission tower is an economical and practical approaching that increase the power transmission capacity of an existing transmission corridor. But, In this case, Inductive and capacitive coupling between AC and DC lines on the same tower should be investigated in advance. According to the installation plan of 80kV ${\pm}$60MW bipole HVDC in Cheju, KOREA that will be commissioned until 2011, DC lines will parallely operate with 154kV 2 AC lines in existed 154kV AC 4 lines transmission tower. This paper presents the steady state analysis results about the interaction between 154kV AC and 80kV DC lines in the same transmission tower.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.1
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• pp.14-19
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• 2011

The implemetation of the AC and DC lines on the same transmission tower is an economical and practical approaching that increase the power transmission capacity of an existing transmission corridor. But, In this case, Inductive and capacitive coupling between AC and DC lines on the same tower should be investigated in advance. According to the installation plan of ${\pm}80kV$ 60MW bipole HVDC in Jeju island, KOREA that will be commissioned until 2011, DC lines will parallely operate with 154kV 2 AC lines in existed 154kV AC 4 lines transmission tower. This paper presents the transient analysis results about the interaction between 154kV AC and 80kV DC lines in the same transmission tower.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.432-433
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• 2018

A new DC-DC converter circuit for LVDC(Low Voltage Direct-Current) distribution is proposed. DC-DC converter consists of two stage which are voltage balancer and converter stage. The balancing circuit adjust balance input voltage of converter circuit and compensate for unbalanced loads and short circuits. The converter circuit control the bipolar output voltage ${\pm}750V$. Simulation is carried out for this DC-DC converter system.

• Progress in Superconductivity and Cryogenics
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• v.17 no.1
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• pp.32-35
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• 2015

Many kinds of high temperature superconducting (HTS) devices are being developed due to its several advantages. In particular, the advantages of HTS devices are maximized under the DC condition. A line commutated converter (LCC) type high voltage direct current (HVDC) transmission system requires large capacity of DC reactors to protect the converters from faults. However, conventional DC reactor made of copper causes a lot of electrical losses. Thus, it is being attempted to apply the HTS DC reactor to an HVDC transmission system. The authors have developed a 8 mH class HTS DC reactor and a model-sized LCC type HVDC system. The HTS DC reactor was operated to analyze its operational characteristics in connection with the HVDC system. The voltage at both ends of the HTS DC reactor was measured to investigate the stability of the reactor. The voltages and currents at the AC and DC side of the system were measured to confirm the influence of the HTS DC reactor on the system. Two 5 mH copper DC reactors were connected to the HVDC system and investigated to compare the operational characteristics. In this paper, the operational characteristics of the HVDC system with the HTS DC reactor according to firing angle are described. The voltage and current characteristics of the system according to the types of DC reactors and harmonic characteristics are analyzed. Through the results, the applicability of an HTS DC reactor in an HVDC system is confirmed.

• Corrosion Science and Technology
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• v.20 no.3
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• pp.112-117
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• 2021

Inductively coupled plasma magnetron sputtering (ICPMS) has the advantage of being able to dramatically improve coating properties by increasing the plasma ionization rate and the ion bombardment effect during deposition. Thus, this paper presents the comparative results of CrN films deposited by direct current magnetron sputtering (dcMS) and ICPMS systems. The structure, microstructure, and mechanical and corrosive properties of the CrN coatings were investigated by X-ray diffractometry, scanning electron microscopy, nanoindentation, and corrosion-resistance measurements. The as-deposited CrN films by ICPMS grew preferentially on a 200 plane compared to dcMS on a 111 plane. As a result, the films deposited by ICPMS had a very compact microstructure with high hardness. The nanoindentation hardness reached 19.8 GPa, and 13.5 GPa by dcMS. The corrosion current density of CrN film prepared by ICPMS was about 9.8 × 10^-6 mA/cm², which was 1/470 of 4.6 × 10^-3 mA/cm², the corrosion current density of CrN film prepared by dcMS.