• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.143-148
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• 1998

The Design criteria of the auxiliary resonant snubber inverter (ARSI) using a load-side circuit are discussed in relation to electric propulsion drives. In this regard, this paper attempts to develop a set of design criteria for the ARSI. First, the switching characteristics of IGBTs under soft-switching mainly in terms of dv/dt/, di/dt and switching losses are discussed and utilized for optimizing the selection of the resonant components in the system. After that, the proper control strategies of ARSIs are analyzed and simulated based on voltage space vector modulations. Later, the design, control and implementation of the auxiliary resonant circuit suitable for industrial products are analyzed and presented. And finally, other factors including power stage layout, packaging and the choice of current sensors are included. The detailed simulation and experimental results will be included based on a laboratory prototype. The proposed design criteria of the ARSI would help the implementation of an electric propulsion drive system.

• 전력전자학회논문지
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• 제22권4호
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• pp.297-304
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• 2017

The purpose of this paper is to analyze losses because of switching devices and the secondary side circuit diodes of 500 W full bridge dc-dc converter by applying gallium nitride (GaN) field-effect transistor (FET), which is one of the wide band gap devices. For the detailed device analysis, we translate the specific resistance relation caused by the GaN FET material property into algebraic expression, and investigate the influence of the GaN FET structure and characteristic on efficiency and system specifications. In addition, we mathematically compare the diode rectifier circuit loss, which is a full bridge dc-dc converter secondary side circuit, with the synchronous rectifier circuit loss using silicon metal-oxide semiconductor (Si MOSFET) or GaN FET, which produce the full bridge dc-dc converter analytical value validity to derive the final efficiency and loss. We also design the heat sink based on the mathematically derived loss value, and suggest the heat sink size by purpose and the heat divergence degree through simulation.

• 한국표면공학회지
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• 제41권1호
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• pp.38-42
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• 2008

316L stainless steel welding tube was electrolytically polished and the inner surface characteristics of the tube were tested. Electro-polishing variables such as current, voltage, concentration of electrolyte and electropolishing time were changed to seek for optimum condition. These makes a optimum conditions for the electro-polishing as 4000 A, 9 V, 1.7 specific gravity of electrolyte, and 30 minute of electro-polishing time. It makes the surface roughness as Ra < $0.25{\mu}m$. XPS test resulted as the ratio of CrO/FeO equals or more to 3/1. AES test resulted as the thickness of CrO film of $38{\AA}$. DTA test resulted as the tube did not react with $N_2,\;H_2\;and\;O_2$ gas below 1073K. As summarize above results, the electro- polished 316L stainless steel welding tube satisfied the conditions to apply as a pipeline for semi- conductor production facility and clean room.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.1614-1616
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• 2000

The purpose of this study is to manufacture and test a thermoelectric generator which converts unused energy from close-at-hand sources, such as garbage incineration heat and industrial exhaust, to electricity. A manufacturing process and the properties of a thermoelectric generator are discussed before simulating the thermal stress and thermal properties of a thermoelectric module located between an aluminum tube and alumina plate. We can design the thermoelectric modules having the good properties of thermoelectric generation. Resistivity of thermoelectric module for thermoelectric generation consisting of 62 cells was $0.15{\sim}0.4{\Omega}$. The maximum power of thermoelectric generator using thermoelectric generating modules can be defined as temperature function, and in this case it can be analogized the linear relation between current and voltage characteristics as function of temperature. The thermoelectric generator using 128 generating modules was assembled with 4 parallel connected modules sets composed with 32 directly connected modules.

• 조명전기설비학회논문지
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• 제26권10호
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• pp.52-59
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• 2012

In this paper, The cast resin transformer's vibration is measured using noncontact raser vibrometer(LV110D). The vibration characteristics of transformer windings and core are analyzed for relation between vibration magnitude and cause. Using the analysis results, the technique is presented to diagnose cast resin transformer. which is able to diagnose transformer' deformation in winding and core geometry. The magnetostriction and electromagnetic force act on the core and windings, causing them to vibrate. The vibration from windings and core penetrates into transformer cast resin and reaches the outside walls. The fundamental frequency of the core and windings vibration signal is twice that of the power frequency(120Hz). The results show that the magnitude of core vibration is linear to driving voltage amplitude and magnitude of windings vibration is increased to loading current under the some level and then stabilized.

• 한국진공학회지
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• 제7권s1호
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• pp.106-117
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• 1998

Fluorocarbonated-SiO2 films were deposited on p-type Si(100) substrate using FSi$(OC_2H_5)_3$ (FTES), and $O_2$ mixture gases by a helicon plasms source. High density $O_2$/FTES/Ar plasma of ~$10^{12} \textrm{cm}^{-3}$ is obtained at low pressure (<3mTorr) with RF power above 900 W in the helicon plasma source. Optical emission spectroscopy (OES) is used to study the relation between the relative densities of the radicals and the film properties. The FTES and $O_2$ gases are greatly dissociated at the helicon mode that is launched at the above threshold plasma density. FTIR and XPS spectra shows that the film has Si-F, and C-F bonds during the formation process of the film which may lower the dielectric constant greatly. The relative dielectric constant, leakage current density, and dielectric breakdown voltage are about 2.8, $8\times10^{-9}\textrm{A/cm}^2$, and > 12 MV/cm, respectively.

• 한국표면공학회지
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• 제56권3호
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• pp.169-179
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• 2023

This work studies dielectric breakdown behavior of AAO (anodic aluminum oxide) films formed on pure aluminum at a constant current density in 5 ~ 20 vol.% sulfuric acid (SA) and 2 ~ 8 wt.% oxalic acid (OA) solutions. It was observed that dielectric breakdown voltage of AAO film with the same thickness increased with increasing concentration of both SA and OA solutions up to 15 vol.% and 6 wt.%, respectively, above which it decreased slightly. The dielectric breakdown resistance of the OA films appeared to be superior to that of SA films. After dielectric breakdown test, cracks and a hole were observed. The crack length increased with increasing SA film thickness but it did not increase with increasing OA film thickness. To explain the reason why shorter cracks formed on the OA films than the SA films after dielectric breakdown test, the generation of tensile stresses at the oxide/metal interface was discussed in relation to porosity of AAO films obtained from cross-sectional morphologies.

• 전자공학회논문지SC
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• 제48권1호
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• pp.31-38
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• 2011

다양한 산업 응용분야에 사용되는 전동기 구동시스템의 고장은 심각한 문제를 초래한다. 본 논문에서는 전압형 PWM 인버터의 스위치 개방고장에 대한 검출 기법을 제안한다. 제안방법은 dq 전류를 정규화하여 dq 상전류의 평균값으로 고장을 검출하고 1차 분류를 실시한다. 분류된 결과에 따라 dq 상전류의 관계, 값의 범위, 전류의 분포 위치 등의 특정을 이용하여 2차 분류를 실시하여 그 결과로 고장 스위치를 진단한다. 제안방법은 MATLAB을 이용하여 인버터 스위치 개방고장진단에 관한 모의실험을 수행하였고 제안방법의 실용성을 입증하였다. 제안방법은 간단한 알고리즘으로 구현이 가능하며 그로 인해 일반적인 유도전동기 구동시스템에 추가하여 사용하는 것이 가능하다.

• 대한조선학회논문집
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• 제35권4호
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• pp.65-75
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• 1998

GMA 용접 중 100% $CO_2$ 가스를 사용하는 $CO_2$ 용접은 경제적이고 고능률적이라는 점 때문에 많이 사용되고 있다. $CO_2$ 용접의 아크현상과 스패터 발생량은 용접용 와이어의 화학성분, 실드가스, 용접조건 등에 영향을 받는다. 특히 용접조건은 용적이행 모드를 결정하기 때문에 스패터 발생량에 커다란 영향을 미친다. 본 연구는 $CO_2$ 용접 재료 중 두 type의 FCW(titania계, semi-metal계)를 이용하여 용접조건을 변화시켜 아크현상과 스패터 발생량을 파악하여 용접부의 품질 평가와 용접조건 설정에 기여코져 한다. 본 연구를 통해, 다음과 같은 결론을 얻을 수 있다. 1) 저전류 영역(140A)의 FCW 모두 22V까지는 전형적이 단락이행이 나타났고, 스패터 발생량의 증가와 저전류 스패터 입도를 대립화하였다. 2) 대전류 영역(320A)의 전형적인 globular이행에서 titania계 FCW가 semi-metal계 FCW보다 아크 안정성이 양호하였다.

• The Korean Journal of Physiology
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• 제29권1호
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• pp.13-27
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• 1995

single $K^{+}$ channels of skeletal muscle from the rat and frog were into planar lipid bilayers and their properties were studied. Fusion was induced by an osmotic gradient. Of the four types of $K^{+}$ channels recorded, the two most frequently observed were a voltage and $Ca^{2+}-activated$ $K^{+}$ channel and a $K^{+}$ channel with a prominent conductance substate. The first $K^{+}$ channel was identified as the large $Ca^{2+}-activated$ $K^{+}$ (BK) channel because the open-state probability was increased with depolarization (e-fold change per $10.6{\pm}3.5$ mV, n=8) and internal $Ca^{2+}$ (half-activation at $16.7{\pm}3.8$ mV, n=8, pCa 4) and its conductance was large ($247{\pm}4.9$ pS, n=24 in 0.1 M KCI). Lifetime distributions of open- and closed-states could be fitted with single exponentials of several milliseconds. The mean open- and closed-lifetimes were linearly dependent on the intracellular $[Ca^{2+}]$ and $1/[Ca^{2+}]$, respectively. The second $K^{+}$ channel showed a conductance substate at $30{\sim}60%$ of the open state. Its current-voltage relation was linear in the range of $-80\;{\sim}\;+80\;mV$. The slope conductance of the substate and open-state were 40 and 144 pS in 0.2 M KCl, respectively. The channel was highly selective for $K^{+}$ over Cl. The open-state probability was weakly voltage-dependent (e-fold change per 35 mV. The lifetime distributions of open- and closed-states were fitted with two exponentials and the major gating occurred slowly at several hundred milliseconds. Based on the above results, we think the second type of $K^{+}$ channel is the sarcoplasmic reticulum $K^{+}$ (SRK) channel. In addition, both types of channel were also incorporated into the lipids extracted from the skeletal muscle. The channel properties recorded in the bilayers termed from synthetic and extracted lipids were qualitatively similar. Our data indicate that BK and SRK channels are rich in the skeletal muscle and their properties and regulation could be effectively studied in planar lipid bilayer.