• 전기전자학회논문지
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• 제16권3호
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• pp.217-223
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• 2012

본 논문은 트리거 시간을 조절하여 펄스 성형이 가능한 150 MW 펄스 파워 시스템의 설계와 동작특성을 알아보았다. 이 시스템은 2개의 커패시터 뱅크 모듈로 구성되어 있고, 각 커패시터 뱅크 모듈은 병렬로 연결되어 있다. 그리고 커패시터 뱅크 모듈은 메인스위치, 커패시터, 에너지 덤프회로, 크로바 회로, 펄스 성형 인덕터로 구성되어 있다. 또한 이 시스템의 모듈 선택과 트리거 시간은 트리거 제어부에서 조정된다. Pspice 시뮬레이션은 실험회로의 결과를 예측하고, 시스템의 구성품의 파라미터를 결정하기 위한 것으로 사용하였다. 실험 결과, 시뮬레이션은 실험결과와 잘 일치하였다. 출력 전류의 펄스폭은 커패시터 뱅크 모듈에서의 순간적 점화 시간 제어로 300~650 us의 펄스폭이 형성되었다. 그리고 최대 전류값은 2개의 커패시터 뱅크 모듈이 동시에 트리거 되었을 때 약 40 kA 정도이다. 이 150 MW 펄스 파워 시스템은 파암 전원, Rail Gun, Coil Gun, 나노분말 제조, HPM 등과 같은 대전류 펄스 파워 시스템에 적용할 수 있다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1997년도 전력전자학술대회 논문집
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• pp.45-48
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• 1997

The low frequency pulsed MIG welding process of new current waveform control to switch over unit pulse conditions (pulse current, pulse duration) in the fixed cycle was developed and its effect were investigated for aluminium and its alloy. By using this new welding process, the bead appearance having clear ripple pattern, such as TIG welding bead can be obtained and the gap tolerance of lap and butt welding joint can be expanded.

• 전자공학회논문지D
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• 제34D권10호
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• pp.85-92
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• 1997

For a InGaAsP buried - heterostructrue $1.3\mu\textrm{m}$ LD with fabry-perot cavity structure, the procedures of ultra-short optical pulse genration ar eanalyzed by simulating the rate equations. Investigting the effects of injected current pulse parameters such as bias $J_b$, pulse width $T_d$ and pulse amplitude $J_p$ on the generated optical pulses, we derive the optimum conditions to obtain a single optical pulse with strong peak value. We also observe that the repetition rate of current pulses needs to be restricted under a certain threshold to generate a train of single optical pulses, and that the period doubling phenomenon takes place by increasing the repitition rate.

• 한국표면공학회지
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• 제43권5호
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• pp.224-229
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• 2010

$Ni-Si_3N_4$ nano-composite coatings were prepared by pulse current (PC) electrodeposition and direct current (DC) electrodeposition techniques. The micro-structure of the coatings was characterized by scanning electron microscopy (SEM), vickers microhardness, X-Ray Diffraction (XRD) and wear-friction tests. The results showed that the micro-structure and wear performance of the coatings were affected by the electrodeposition techniques. Pulse current electrodeposited $Ni-Si_3N_4$ composite coatings exhibited higher microhardness, smooth surface, and better wear resistance properties as compared to coatings prepared under DC condition. The $Ni-Si_3N_4$ composite coatings prepared at 50 Hz pulse frequency with 10% duty cycles has shown higher codeposition of nano-particles. Consequently, increased microhardness and less plastic deformations occurred in coatings during sliding wear test. The XRD patterns revealed that the increased pulse frequencies changed the preferred (100) nickel crystallite orientations into mixed (111) and (100) orientations.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2000년도 제18회 학술발표회 논문개요집
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• pp.200-200
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• 2000

AC-PDP의 구동은 인가되는 Pulse의 파형에 의하여 결정된다. 이번 실험은 AC-PDP의 Subfield 파형중 Sustain 부분 첫 번째 Pulse의 폭(Width)에 변화를 주어 다음 Suatain Pulse 기간동안의 전기 광학적 특성을 구속 카메라와 전류의 변화를 통하여 측정하였으며 Sustain Pulse의 Rising Time을 변화 시켜 방전특성을 측정하였다. 이를 통하여 적합한 Sustain 구간의 초기조건을 예측하였으며, 적합한 Sustain Pulse를 찾아가는 실험 방법을 찾고자 하였다.

• Journal of Welding and Joining
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• 제15권5호
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• pp.84-91
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• 1997

The metal transfer phenomenon of the pulsed-GMAW is simulated by formulating the electromagnetic force incorporated with the Volume of Fluid algorithm. The free surface profiles, pressure and velocity distributions within the drop are computed numerically. Axial velocity and acceleration generated during peak current period are found to have a significant effect on drop detachment. Therefore, the accelerated inertia force becomes one of important factors affecting metal transfer in the pulsed-GMAW. When the pulse current parameters are selected properly, the molten drop is detached just after current pulse, and the operating range of the pulsing frequency increases with higher peak current and duty cycle. Calculated operating ranges show reasonably good agreements with the available experimental data.

• 한국표면공학회지
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• 제35권1호
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• pp.53-63
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• 2002

Ni coating was carried out by pulse plating at room temperature. So, experimental conditions for Ni-coating were based on Watt's bath, and new additives(propionic acid) were introduced in the Watt's bath electrolyte as $H_3$$BO_3$ alternatives. By adding propionic acid, coating layer demonstrated a good adhesion and uniformity without special pre-treatment of the 316L stainless steel at room temperature. With a decrease of amount of propionic acid and applied average current density, cathode current efficiency increased. Also, edge effect was decreased with decreasing a peak current and increasing a pulse frequency in the same bath condition. It was found that the optimum condition for Ni coating was a current density of 10~20mA/$\textrm{cm}^2$ at below 500 mA peak current in the $5m\ell/\ell$ propionic acid solution.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제52권12호
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• pp.573-578
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• 2003

In this study, new type of induction charging system for electrostatic spraying was manufactured and proposed to improve the electrical safety and charging efficiency. And parameters of proposed system to generate the maximum deposition current with electrical safety were selected and investigated. The selected parameters were frequency of square pulse and thickness of insulation material, outer diameter of device and thickness and positions of electrode. Charging quantity of water drop was measured by deposition current detected from sensing plate indirectly. The maximum deposition current for each parameter were 3.5[uA] at the frequency of 15[kHz] and thickness of 0.25[mm] insulating layer. And maximum deposition currents were 2.8[uA] and 3.0[uA] at 25[mm] outer diameter of charging device and 0.25[mm] thickness of electrode each. Effects of electrode position from spraying nozzle on deposition current was a little.

• 한국표면공학회지
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• 제26권5호
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• pp.245-254
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• 1993

The effects of pulse current electrolysis conditions on the composition and the microstructure of Ag-Sn alloy were studied by using a pyrophosphate bath. Both cathode current efficiency and throwing power of alloy deposits formed under pulse plating conditions, decreased with increasing mean current density, and lower than those under D.C. electrolysis condition. Tin content of Ag-Sn alloy decreased noticebly with in-creasing the mean current density, while it increased with the increase of On-time from 1 to 10 ms. The pre-ferred orientation of Ag-Sn alloy changed with increasing cathode overpotential in the sequence of (100)longrightarrow(100)+(111)longrightarrow(111) at $20^{\circ}C$ and (110)longrightarrow(111)longrightarrow(111)+(100) at $30^{\circ}C$. The effective crystal grain size of the alloy was decreased by decreasing temperature from $30^{\circ}C$ to $20^{\circ}C$ and the surface structure of them was related to the preferred orientation.

• 한국통신학회논문지
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• 제40권9호
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• pp.1693-1698
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• 2015

본 논문은 이중 펄스 폭을 지닌 PFM(Pulse-Frequency Modulator) 부스트 변환기를 제안한다. 부스트 변환기의 구동 회로 구조는 밴드 갭 기준 전압 발생 회로와 이를 이용해 여러 가지의 기준 전압을 생성하는 기준 전압 발생 회로, 소프트 시동 회로, 에러 증폭기, 고속 전압 비교기, 인덕터 전류 센싱 회로, 펄스 폭 발생 회로로 구성되어있다. 변환기는 부하 전류 상태에 따라 서로 다른 최대 인덕터 전류 값을 갖도록 구성해 부하 범위를 넓히고, 출력 전압 리플을 감소하도록 했다. 제안된 PFM 부스트 변환기는 입력 전압으로 3.7V를 받고, 18V의 출력 전압을 생성한다. 구동 가능한 부하 전류는 0.1~300mA의 범위를 가진다. 모의실험 결과 저 부하 전류 동작 구간에서 0.43%, 고 부하 전류 동작 구간에서는 0.79%의 출력 전압 리플을 보였다. 변환기는 저 부하 구간에서 85%의 효율을 나타내며 20mA에서 86.4%로 최대의 효율을 나타냈다.