• Journal of Electrical Engineering and Technology
• /
• v.11 no.3
• /
• pp.675-682
• /
• 2016

Sudden voltage drops and outages frequently disturb the operation of sensitive loads for domestic, commercial, and industrial use. In some cases, these events may even impair the functioning of relevant equipment. To maintain power under such conditions, a UPS system is usually installed. Once a disturbance happens at the grid side, the line-interactive UPS system takes over the load to prevent an interruption. But, due to magnetic saturation of the transformer, a significant inrush current may occur for the transformer-coupled loads during this transition. The generation of such transient currents may in turn decrease the line voltage and activates over-current protecting devices of the system. In this work, a cost-effective, line-interactive UPS system is proposed that eliminates the inrush current phenomenon associated with transformer-coupled loads. The strategy was implemented by connecting a standard current-regulated voltage source inverter (CRVSI) to the secondary winding of the load transformer. During any transient condition at the grid side, the load current is monitored and regulated to achieve either seamless compensation of the load current or complete transferal of load from grid to the inverter. Experimental results were obtained for a prototype under all possible operating conditions so as to validate the performance of the proposed topology.

• Journal of Power Electronics
• /
• v.19 no.4
• /
• pp.934-943
• /
• 2019

A current balance problem exists in multi-phase LLC converters due to the resonant parameter tolerance. This paper presents a current balancing method for interleaved three-phase half bridge LLC converters. This method regulates the phase shift angle of the driving signals between the three phases based on a converter with a floating Y-connection. The floating midpoint voltage has different influences on each phase current and makes the three-phase current balance performance better than midpoint non-floating systems. Phase shift control between modules can further regulate the midpoint voltage. Then three phase current sharing is realized without adding extra components. The current distributions in a midpoint non-floating system and a midpoint floating system are compared. Then the principle and implementation of the proposed control strategy are analyzed in detail. A 3kW prototype is built to verify the validity and feasibility of the proposed method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1999.11a
• /
• pp.513-515
• /
• 1999

In this study, we evaluated the relation of the test and theory of low impedance cable As the result We could obtained the result in accordance the test with theory in 85 ~ 95% tolerance . Test method measured the relation of the current and temperature of cable jacket in using CT to put in 3 phase AC current simultationiously. The current and temperature of it was calculated in according to JCS- l68D

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1997.11a
• /
• pp.306-308
• /
• 1997

The Maxwell displacement current was investigated in the connection with stwiching characteristics by photoisomerization of monolayers. The displacement current was generated due to the trans-to-cis photoisomerization by irradiation with ultraviolet light( λ$_1$1=360nm). whereas the displacement current was generated in the opposite direction due to the sis-to-trans photoisomerization by irradiation with visible light( λ$_1$=450nm). The reversible displacement current generation was found to be sustained by alternative irradiation with UV light and visible light.

• Proceedings of the KIPE Conference
• /
• 2004.07b
• /
• pp.515-518
• /
• 2004

Increasing of the nonlinear power electronics equipments, power conditioning systems have been researched and developed for many years to compensate the harmonic disturbances and the reactive power. The main function of power conditioning systems is to reduce harmonic distortions, since extensive surveys quantify the problems associated with electric networks having non-linear loads. The main function of power conditioner compensates the current instead of the voltage. Therefore the inverter used in power conditioner is mostly the current controlled type. In this paper, we propose the power conditioner using photovoltaic system, which is operated by the PRT(Polarized Ramp Time) current control algorithm. The proposed system could also achieve Demand Side Management's function and Uninterruptible Power Supply's function simultaneously. To verify the proposed current controlled inverter for improved quality of the grid, the detail simulation and experiment results indicate that operation PCS, DSM and UPS can be achieved.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.07b
• /
• pp.864-867
• /
• 2003

Since the development of semiconductors, various related research has been conducted. During research, silicon diodes have been commonly used because of their simplicity and low cost in the manufacturing process. This research deals with p-n junction threshold voltages from silicon diodes due to transport current at a cryogenic temperature. At a cryogenic temperature(77K) we could get minimum current which junction threshold voltage becomes constant. This is experimented on GPIB communication and it consist of programmable current source, multimeter which gauge the threshold voltage in a very low temperature caused by transport current from 5nA to 1mA and $LN_2$(77K) for coolant. This experiment is programmed all process using Measurement studio(Lab window) tool.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.02a
• /
• pp.385-385
• /
• 2012

A two terminal N+/P/N+ junction device to replace the conventional selective transistor was studied as a bilateral switching device for spin transfer torque (STT) MRAM based on 3D device simulation. An N+/P/N+ junction structure with $30{\times}30nm$ area requires bi-directional current flow enough to write a data by a drain induced barrier lowering (DIBL) under a reverse bias at N+/P (or P/N+ junction), and high current on/off ratio of 106. The SiGe materials are widely used in hetero-junction bipolar transistors, bipolar compensation metal-oxide semiconductors (BiCMOS) since the band gap of SiGe materials can be controlled by changing the fraction and the strain epilayers, and the drift mobility is increased with the increasing Ge content. In this work, N+/P/N+ SiGe material based junction provides that drive current is increased from 40 to $130{\mu}A$ by increased Ge content from 10~80%. When Ge content is about 20%, the drive current density of SiGe device substantially increased to 2~3 times better than Si-based junction device in case of 28 nm P length, which is sufficient current to operation of STT-MRAM.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.4 no.2
• /
• pp.94-99
• /
• 2004

silicided 50-nm-gate-length n-type Schottky barrier metal-oxide-semiconductor field-effect-transistors (SB-MOSFETs) with 5 nm gate oxide thickness are manufactured. The saturation current is $120{\mu}A/{\mu}m$ and on/off-current ratio is higher than $10^5$ with low leakage current less than $10{\mu}A/{\mu}m$. Novel phenomena of this device are discussed. The increase of tunneling current with the increase of drain voltage is explained using drain induced Schottky barrier thickness thinning effect. The abnormal increase of drain current with the decrease of gate voltage is explained by hole carrier injection from drain into channel. The mechanism of threshold voltage increase in SB-MOSFETs is discussed. Based on the extracted model parameters, the performance of 10-nm-gate-length SB-MOSFETs is predicted. The results show that the subthreshold swing value can be lower than 60 mV/decade.

• Electrical & Electronic Materials
• /
• v.9 no.10
• /
• pp.1001-1007
• /
• 1996

The conduction mechanisms of the off-current in low temperature (.leq. >$600^{\circ}C$) processed polycrystalline silicon thin film transistors (LTP poly-Si TFT'S) have been systematically studied. Especially, the temperature and bias dependence of the off-current between hydrogenated and nonhydrogenated poly-Si TFT's were investigated and compared. The off-current of nonhydrogenated poly-Si TF's is because of a resistive current at low gate and drain voltage, thermally activated current at high gate and low drain voltage, and Poole-Frenkel emission current in the depletion region near the drain at high gate and drain voltage. After hydrogenation it has shown that the off -current mechanism is caused mainly by thermal activation and that the field-induced current component is suppressed.

• Current Optics and Photonics
• /
• v.4 no.5
• /
• pp.434-440
• /
• 2020

Based on single-mode rate equations, we present an improved equivalent-circuit model for distributed-feedback (DFB) lasers that accounts for the effects of parasitic parameters and nonradiative recombination. This equivalent-circuit model is composed of a parasitic circuit, an electrical circuit, an optical circuit, and a phase circuit, modeling the circuit equations transformed from the rate equations. The validity of the proposed circuit model is verified by comparing simulation results to measured results. The results show that the slope efficiency and threshold current of the model are 0.22 W/A and 13 mA respectively. It is also shown that increasing bias current results in the increase of the relaxation-oscillation frequency. Moreover, we show that the larger the bias current, the lower the frequency chirp, increasing the possibility of extending the transmission distance of an optical-fiber communication system. The results indicate that the proposed circuit model can accurately predict a DFB laser's static and dynamic characteristics.