• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.1
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• pp.1-8
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• 2014

The conventional Three-Stage electronic ballast is stable, but Two-Stage electronic ballast has been researching because of efficiency. Three-Stage electronic ballast is consisted of PFC circuit, buck converter, and inverter circuit, but Two-stage is consisted of PFC circuit, Buck-Inverter full bridge circuit. The Buck-Inverter full bridge inverter consists of two half bridge inverters for low frequency switching, and high frequency switching. In the case of street lamp it is far from a lamp to a ballast, the conventional pulsed high voltage ignitor can not turn on the HID lamps because of reduction of ignition voltage. Therefore, it needs to do the research on a resonant ignition to turn on the HID lamps. Therefore, in the Two-Stage electronic ballast which has the resonant tank for ignition, the transient resonant current because of low frequency changing is analyzed, the novel algorithm is proposed to resuce the transient current.

• Journal of Power Electronics
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• v.11 no.3
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• pp.375-380
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• 2011

A STATic synchronous COMpensator (STATCOM) is a shunt connected voltage source converter (VSC) based FACTS controller using Gate Turn Off (GTO) power semiconductor devices employed for reactive power control. The operation principal is similar to that of a synchronous condenser. A typical application of a STATCOM is voltage regulation at the midpoint of a long transmission line for the enhancement of power transfer capability and/or reactive power control at the load centre. This paper presents the modeling of STATCOM with twenty four pulse three level VSC and Type-1 controller to regulate the reactive current or the bus voltage. The performance is evaluated by transient simulation. It is observed that, the STATCOM shows excellent transient response to step change in the reactive current reference. While the eigenvalue analysis is based on D-Q model, the transient simulation is based on both D-Q and 3 phase models of STATCOM (which considers switching action of VSC).

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.24-26
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• 1995

In this paper, we investigated transient fault currents in a magnetic coupling High-Tc superconducting current limiter(HCL). It has an important effect on the reliability and stability of the power system. In order to analyze transient fault characteristics of HCL, we fabricated a magnetic coupling HCL and tested it in different fault conditions. An important parameter of design and manufacture which makes HCL inherently reliable is reduction of inrush fault currents. Without inrush fault currents, the currents flowing under such conditions can be limited to a desired-value within one cycle. Inrush fault current depends on saturation, normal spot propagation velocity, turns ratio and the fault angle.

• Proceedings of the KIEE Conference
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• 1987.11a
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• pp.283-285
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• 1987

Transient conduction current (I - t characteristics) were measured in thin PPMMA (plasma-polymerized methyl methacrylate) films over the temperature range $60^{\circ}C-140^{\circ}C$ and the applied voltage range 3V - 30V. The current, which increased with temperature rise at constant applied voltage, showed less absorption current (current decay with time) at higher temperature region compared with those at lower temperature region. And the current, which increased with applied voltage rise at the constant temperature, showed less absorption current at higher voltage compared with those at lower voltage. The electric field current density characteristic curves were abtained from the conduction current values were after applying voltage for 30 minutes. And transient conduction currents were analyzed with high field conduction theories.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.3
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• pp.422-426
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• 2012

Transient radiation is emitted during a nuclear explosion. Transient radiation causes a fatal error in the CMOS circuit as a Upset and Latch-up. In this paper, transient radiation NMOS, PMOS, INVERTER SPICE model was proposed on the basisi of transient radiation effects analysis using TCAD(Technology Computer Aided Design). Photocurrent generated from the MOSFET internal PN junction was expressed to the current source and Latch-up phenomenon in the INVERTER was expressed to parasitic thyristor for the transient radiation SPICE model. For example, the proposed transient radiation SPICE model was applied to CMOS NAND circuit. SPICE simulated characteristics were similar to the TCAD simulation results. Simulation time was reduced to 120 times compared to TCAD simulation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.1
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• pp.133-143
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• 2001

This paper describes the correlation of the transient impedance and its parameters with the stationary resistance of a grounding system to a square pulse current and a lightning impulse current. In the experiment, the grounding system consists of a single grounding rod$(\Psi10[mm], 1[m])$and/or a triple-grounding rods of equilateral triangles with 5[m] spacing for operation. To analyze the transient impedance characteristics of the grounding system, a pulse generator which can produce square wave of a 30[ns] rise-time and a $20[\mus] $pulse duration is designed and fabricated. The injected content in the grounding system and the developed potential were recorded, and the time variation of the transient impedance were calculated as the ratio of the potential rising to the injected current at each time. The transient impedance and the effective surge impedance Z3 which defines economic protection level in power system were quite higher than the stationary resistance. The grounding impedance is decreased by the application of the triple-rods grounding system, and its effect is decreased as the frequency of the current is increased due to the inductance of the grounding leads.

• KEPCO Journal on Electric Power and Energy
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• v.6 no.4
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• pp.393-397
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• 2020

Shunt reactor, a facility for reactive power compensation, is switched several times a day depending on the load pattern. When the circuitbreaker opens the shunt reactor over-voltage is generated by several factors which degrade the insulating performance of internal parts of the circuit-breaker and cause severe voltage stress on the equipment in the power system. Transient phenomenon occurring during the switching of shunt reactor are available in laboratories that verify the performance of the circuit-breaker by simulating the power system. However, it is difficult to measure the transient phenomenon that occurs during actual operation in actual power system due to many limitations. Therefore, this paper deals with the modeling using EMTP to analyze the reignition and current chopping which causes more severe transient recovery voltage in the small inductive current breaking in actual power systems. In addition, this paper analyzes the main phenomenon that cause circuit-breaker failure in opening shunt reactor using EMTP model.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.04b
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• pp.43-46
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• 2000

In this paper, the stress and transient currents associated with the on and off time of applied voltage were used to measure the density and distribution of high voltage stress induced traps in thin silicon oxide films. The transient currents were due to the discharging of traps generated by high stress voltage in the silicon oxides. The trap distributions were relatively uniform near both cathode and anode interface. The trap densities were dependent on the stress polarity. The stress generated trap distributions were relatively uniform the order of $10^{11}\sim10^{21}$[states/eV/$cm^2$] after a stress. The trap densities at the oxide silicon interface after high stress voltages were in the $10^{10}\sim10^{13}$[states/eV/$cm^2$]. It appear that the stress and transient current that flowed when the stress voltage were applied to the oxide was caused by carriers tunneling through the silicon oxide by the high voltage stress generated traps.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.5
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• pp.98-105
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• 2014

Soil discharges near the ground rod play an important role to reduce the ground potential rise and the ground impedance and to help the fault current to spread into the earth. This paper presents the effects of soil discharges on the transient and conventional ground impedances when the lightning impulse voltage was applied to a ground rod with radial needles. The current-voltage (I-V)curves and transient ground impedance curves were calculated based on the measured current and potential traces. Soil discharge behaviors related to I-V curves and transient ground impedance curves were analyzed as a function of the magnitude of lightning impulse voltages. As a result, the soil discharges occurred near the ground electrode contribute to the reduction of conventional ground impedance and limits the ground potential rise effectively under lightning impulse voltages.

• Progress in Superconductivity and Cryogenics
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• v.23 no.3
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• pp.55-59
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• 2021

A thermoelectric cooler (TEC) is promising as an alternative refrigeration technology for the sake of its inherent advantages; no-moving parts and refrigerant-free in its operation. Due to the compactness, reliability and excellence in temperature stability, TECs have been widely used for small cooling devices. In recent years, thermoelectric devices have been attractive technologies that not only serve the needs of cooling and heating applications but also meet the demand for energy by recycling waste heat. In this research paper, multistage TEC is proposed as a concept of demonstrating the idea of transient cooling technology. The key idea of transient cooling is to harnesses the thermal mass installed at the interfacial level of the stages. By storing heat temporally at the thermal mass, the multistage TEC can readily reach lower temperatures than that by a steady-state operation. The multistage TEC consists of four different sizes of thermoelectric modules and they are operated with an optimized current. Once the cold-part of the uppermost stage is reached at the no-load temperature, the current is successively supplied to the lower stages with a certain time interval; 25, 50 and 75 seconds. The results show the temperatures that can be ultimately reached at the cold-side of the lowermost stage are 197, 182 and 237 K, respectively. It can be concluded that the timing or total amount of the current fed to each thermoelectric module is the key parameter to determine the no-load temperature.