• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.1
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• pp.23-28
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• 1999

Electrical breakdown characteristics of liquid nitrogen($LN_2$) used as both coolant and insulator for high $T_c$ superconductor system are very important. This paper presents dynamic breakdown characteristics fo $LN_2$ by quench phenomena of thermal bubble under high electric field. Experimental results revealed dynamic breakdown voltage fell down drastically compared with the static breakdown voltage without the quench. Because of increasing heat power, bubble size becomes big and breakdown voltage decreases. The breakdown voltage mechanism of $LN_2$ depends on thermal bubble effect. In the Electrode arrangement, electrical breakdown voltage of horizontal arrangement appears lower than that of vertical arrangement. Also, we observed the behavior of thermal bubbles in $LN_2$ which were generated after quench using camera.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.4
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• pp.210-213
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• 2017

In this paper, we analyzed the structural design and electrical characteristics of a 3.3 kV super junction FS IGBT as a next generation power device. The device parameters were extracted by design and process simulation. To obtain optimal breakdown voltage, we researched the breakdown characteristics. Initially, we confirmed that the breakdown voltage decreased as trench depth increased. We analyzed the breakdown voltage according to p pillar dose. As a result of the experiment, we confirmed that the breakdown voltage increased as p pillar dose increased. To obtain more than 3.3 kV, the p pillar dose was $5{\times}10^{13}cm^{-2}$, and the epi layer resistance was $140{\Omega}$. We extracted design and process parameters considering the on state voltage drop.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.44 no.4
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• pp.490-495
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• 1995

A bipolar junction transistor which exihibits 1000V breakdown voltage is designed and fabricated using FLR (Field Limiting Rings). Three dimensional effects on the breakdown voltage is investigated in the cylindrical coordinate and the simulation results are compared with the results in the rectangular coordinate. Breakdown voltage of the device with 3 FLR is simulated to be 1420V in the cylindrical coordinate while it is 1580V in rectangular coordinate. Bipolar junction transistor has been fabricated using the epitaxial wafer of which resistivity is 86 .OMEGA.cm and thickness is 105 .mu.m. Si$_{3}$N$_{4}$ and glass are employed for the passivation. Breakdown of the fabricated device is measured to be 1442V which shows better greement with the simulation results in cylindrical coordination.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.1
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• pp.78-82
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• 2020

In this study, MOSFETs fabricated on Si-doped, MBE-grown β-Ga₂O₃ are demonstrated. A Si-doped Ga₂O₃ epitaxial layer was grown on a Fe-doped, semi-insulating 1.5 cm × 1 cm Ga₂O₃ substrate using molecular beam epitaxy (MBE). The fabricated devices are circular type MOSFETs with a gate length of 3 ㎛, a source-drain spacing of 20 ㎛, and a gate width of 523 ㎛. The device exhibited a good pinch-off characteristic, a high on-off drain current ratio of approximately 2.7×10⁹, and a high breakdown voltage of 1,080 V, which demonstrates the potential of Ga₂O₃ for power device applications including electric vehicles, railways, and renewable energy.

• Journal of IKEEE
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• v.22 no.2
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• pp.339-343
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• 2018

Power semiconductors are semiconductors capable of controlling power over 1W and are mainly used as switches. This power semiconductor device has been developed with the goal of reducing power consumption and high breakdown voltage. This research was analyzed electrical characteristics of IGBT(Insulated Gate Biopolar Transistor) according to diffusion length of JFET region. The Diffusion length of JFET region was controlled by temperature and time using T-CAD simulator. As a result of experiments, we could obtain 1.14V low on state voltage drop by fixing 1440V breakdown voltage.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.3
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• pp.674-679
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• 2011

In this paper, we experimented and analyzed about electric fire risk assessment methods of LED lightings for outdoor. LED lighting is composed of AC power lines, AC/DC converter, DC power lines and LED lamps. There are some risk factors of electric fire in LED lighting such as short circuit between power lines or power line and ground, dielectric breakdown, leakage current, abnormal voltage inflow, poor contacts(connections), etc. As a result of this study, insulation coverings of wire was ignited due to dielectric breakdown between power lines and molten marks were formed in copper conductor. LED lighting was blown out while short circuit, beside that, electrical disorder did not occur. When abnormal voltage was inflowed, electronic components such as varistor, condenser were damaged. Partial heating was produced and insulation was melted and carbonized by arc and heating while poor contacts were happened. We expect that the results of this study would be helpful for electrical safety of LED lightings for outdoor.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.384-385
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• 2007

The fault current through the earth originated from a power line ground fault might cause arcing through the soil to an adjacent pipeline, which might bring about not only a catastrophic accident such as gas explosion and oil leakage but also a hazard to the safety of workers responsible for the maintenance and repair of the pipeline. In this paper we experimented on the soil breakdown test using the fixture and outlined the standards for the separation distance of a buried pipeline adjacent to the power line tower.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.453-454
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• 2011

With the transmission line the ratio of lightning breakdown the while whole breaking down is occupying a high share with average 72%, is a tendency which increases continuously. In order decreasing the back flashover faults from like this lightning breakdown, it is very important to maintain grounding resistance of tower below target. In this paper, we synthetically analyzed the grounding resistance reduction effect of tower foundation and standard ground connection from construction site, and investigated efficiency for ways to increase the length of counter poise and expand the size of conductivity concrete materials.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.5-5
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• 2010

Gallium Nitride(GaN)는 LED, Laser 등에 사용되는 광학적 특성뿐만 아니라 Wide Bandgap의 전기적 특성 또한 주목받고 있다. 본 논문은 600V급 GaN(Gallium Nitride) Power SIT(Static Induction Transistor)에 대해서 Design Parameter 변환에 따른 전기적 (Breakdown Voltgage, On-state Voltage Drop)특성과 열적 (Lattice Temperature Distribution)특성변화를 분석하여 소자가 갖는 구조적 손실을 최소화하였다. 또한, 기존 실리콘 기반 전력소자와 특성 비교를 통하여 GaN Power SIT의 우수성을 증명하였다. GaN Power SIT 소자 설계 및 최적화를 위해서 Silvaco사의 소자 시뮬레이터인 ATLAS를 사용하였다. 실험 결과 수 ${\mu}m$의 소자 두께만으로도 실리콘 전력소자에 비해 더 뛰어난 열 특성과 더 적은 전력소모를 갖는 600V급 GaN Power SIT 소자를 구현할 수 있었다.

• Progress in Superconductivity and Cryogenics
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• v.5 no.1
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• pp.52-55
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• 2003

For the dielectric insulation design of any high temperature superconducting (HTS) apparatus in the electrical power systems, the breakdown properties of cryogenic coolants such as $LN_2$ are an important factor of the insulating engineering. Therefore, this paper presented an experimental investigation of breakdown phenomena in $LN_2$ under AC voltage. And we studied the breakdown properties of LN2 with decreasing temperature. Also, the Weibull plots of the breakdown voltage of subcooled $LN_2$ at 65 K for the needle-plane electrode with electrode distance d= 10 mm are studied. The dependence of breakdown voltage for needle-plane and pancake coil-pancake coil electrode on temperature is illustrated. The experimental data suggested that the breakdown voltage of L$N_2$ depend strongly on the temperature of $LN_2$. The breakdown characteristics of $LN_2$ under quasi-uniform and non-uniform electrical field for temperature ranging from 77 K to 65 K were clarified.