• Journal of the Korean Vacuum Society
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• v.12 no.4
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• pp.239-250
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• 2003

The reliability degradation phenomena in the SiGe hetero-junction bipolar transistor (HBT) are investigated in this review. In the case of the SiGe HBT the decrease of the current gain, the degradation of the AC characteristics, and the offset voltage are frequently observed, which are attributed to the emitter-base reverse bias voltage stress, the transient enhanced diffusion, and the deterioration of the base-collector junction due to the fluctuation in fabrication process, respectively. The reverse-bias stress on the emitter-base junction causes the recombination current to rise, increasing the base current and degrading the current gain, because hot carriers formed by the high electric field at the junction periphery generate charged traps at the silicon-oxide interface and within the oxide region. Because of the enhanced diffusion of the dopants in the intrinsic base induced by the extrinsic base implantation, the shorter distance between the emitter-base junction and the extrinsic base than a critical measure leads to the reduction of the cut-off frequency ($f_t$) of the device. If the energy of the extrinsic base implantation is insufficient, the turn-on voltage of the collector-base junction becomes low, in the result, the offset voltage appears on the current-voltage curve.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.14 no.3
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• pp.49-58
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• 2000

This paper deals with a systematic approach to neural network controller design for static VAR compensator (SVC) using a learning algorithm of error back propagation that accepts error and change of error as inputs, the momentum learning technique is used for reduction of learning time, to improve system stability. A SVC, one of the Flexible AC Transmission System(FACTS), constructed by a fixed capacitor(FC) and a thyristor controlled reactor(TCR), is designed and implemented to improve the damping of a synchronous generator, as well as controlling the system voltage.TO verify the robustness of the proposed method, we considered the dynamic response of generator rotor angle deviation, angular velocity deviation and generator terminal voltage by applying a power fluctuation and rotor angle fluctuation in initial point when heavy load and normal load. Thus, we prove the usefulness of proposed method to improve the stability of single machine-infinite bus with SVC system.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.428-430
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• 2007

Converter that is dc source equipment source's phase by reference control function that detect source's phase because should be done compulsorily use. Source's phase detect method there be method that use source's ac voltage directly by signal, and use methods that voltage detects status by PLL method and so on via point that '0' becomes usually. All above methods to detect phase are using, wrong action of phase detector converter's ailment or converter of burn can. Ths paper compares and examined usable phase detection method in source's frequency fluctuation presuming source's frequency using observer.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.05a
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• pp.382-384
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• 2013

LED is much brighter than the traditional incandescent, and low power consumption. Development and commercialization of LED fluorescent lamp is made in order to improve efficient fluorescent lamps with this existing and environmental problems. Because, unlike fluorescent lamps, it is not possible to directly use AC power to the unidirectional element having a polarity, LED requires a power supply. The power supply function is lowered as compared with the fluorescent lamp common in terms of maintenance costs because of the high price large. In this study, we constructed a circuit that can be controlled with a constant current in order to eliminate a phenomenon that brightness of the light which rectifies the AC power supply easy to place in the power supply due to the current change due to the voltage fluctuation is changed, in maintenance, I would like to propose how to develop a device which can be easily replaced less expensive composed of interchangeable modules of Plug in / out method to distinguish the LED module this.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.9
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• pp.8-13
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• 2008

Noise in homogeneous extrinsic semiconductor samples is calculated due to distributed diffusion noise sources. As the length of the device shrinks at a fixed bias voltage, the ac-wise short-circuit noise current shows excess noise as well as thermal noise spectra. This excess noise behaves like a full shot noise when the channel length becomes very small compared with the extrinsic Debye length. For the first time, the analytic formula of the excess noise in extrinsic semiconductors from velocity-fluctuation noise sources is given for finite frequencies. This formula shows the interplay between transit time, dielectric relaxation time, and velocity relaxation time in determining the terminal noise current as well as the carrier density fluctuation. As frequency increases, the power spectral density of the excess noise rolls off. This formula sheds light on noise in nanoscale MOSFETs where quasi-ballistic transport plays an important role in carrier transport and noise.

• International Journal of Advanced Culture Technology
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• v.3 no.1
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• pp.120-128
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• 2015

In this paper, Residential roof top photovoltaic system with 9.9 kW design is proposed. The system composed of 200 Watts solar array 33 panels connecting in series 10 strings and parallels 3 strings which have maximum voltage and current are 350 V and 23.8 A. The 10 kW sinusoidal grid-connected inverter with window voltage about 270-350 is selected to convert and transfer DC Power to AC Power at PCC (Point of Common Coupling) of power system following to utility standard. However the impact of fluctuation and uncertainty of weather condition of PV may decrease the voltage stability and voltage collapse of power system. In order to solve this problem the energy storage such 120 V 1200 Ah battery bank and 30 kVAR capacitor are designed for voltage stability control. The other expensed for installing the system such battery charger, cable, accessories and maintenance cost are concerned. The economic analysis by using investment from money loan with interest about 7% and use own money which loss income of deposit about 3% are calculated as 671,844 and 547,044 for PV system with energy storage and non energy storage respectively. The solar energy from PV is about 101,616 Bath per year which evaluated by using the value of $5kWh/m^2/day$ from average peak sun hour (PSH) of the Thailand and 6.96 Bath/kWh of Feed in Tariff Incentive. The payback periods of four scenarios are proposed follow as i) PV system with energy storage and use loan money is 15 years ii) PV system with no energy storage and use loan money is 10 years iii) PV system with energy storage and use deposit money is 9 years iv) PV system with energy storage and use deposit money is 7 years. In addition, the other scenarios of economic analysis such no FIT support and other type of economic analysis such NPV and IRR are proposed in this paper.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1735-1737
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• 2001

The occurrence of fires under transmission lines is responsible for a great number of power line outages. In this paper, the ac flashover voltages and the corona onset voltages of a needle-plane electrode gap of vertical arrangement in the presence of flame were investigated. We also observed the corona discharge current and variation of shapes in flame with increasing the applied voltages. We found that the corona onset voltages and the flashover voltages were drastically decreased with the position of flames and gap length of electrodes, and observed that the deflection or fluctuation phenomena in the shape of flames.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.36 no.3
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• pp.163-170
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• 1987

It is known that reactive component of AC power in the power system gives no energy to outside and cuses enlargiment of power apparatus, voltage fluctuation and unstability of power system. The power conversion system and control system which are composed of power semiconductor devices such as tyristor, transistor, GTO and so on have been appeared as new sources of reactive power. So the cmpensation of reactive power in power semiconductor systems is one of impending problem on the point of energy conservation and inprovement of power factor. This paper treates the fundamental review of the current type power compensation system that compensates the reactive power by MOSFET inverter. This inverter detects not only the reactive power of fundamental wave but also that of all harmoics created in the power semiconductor system and is scheduled to control by sampled value.

• Proceedings of the KIEE Conference
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• 1987.11a
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• pp.359-361
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• 1987

It is known that the reactive component of AC power in the Power system gives no energy to outside and causes enlargement of power apparatus, voltage fluctuation and unstability of power system. The power conversion system and control system which are composed of power semiconductor devices such as Thyrisor, transistor, GTO and so on have been appeared as new sources of Harmonics. So the reduction of harmonics in power semiconductor system is one of impending problems on the point of energy conservation and improvement of power factor. This paper treates the fundamental review of the harmonics reduction by Current type PWM-Inverter. This Inverter-detects not only the fundamental wave but also that of all harmonics created in the power semiconductor system and is scheduled to control by sampled value.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.121.1-121.1
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• 2014

Recently, much attention has been given to plasma production under liquid and its applications [1]. However, most of plasma production techniques reported so far utilize high voltage dc, ac, rf or microwave power [2], where damage to discharge electrodes and small discharge volume are remained issues. As an alternative of plasma production method under liquid, we have proposed pulsed microwave excited plasma using slot antenna, where damage to the slot electrode can be minimized and plasma volume can be increased. We have also reported improvement of treatment efficiency with use of reduced-pressure condition during the discharge [3]. To realize low pressure conditions in liquid, various alternative technique can be considered. One possible technique is simultaneous injection of microwave power and ultrasonic wave. Ultrasonic wave induces pressure fluctuation with the wave propagation and is so far used for cavitation production in the water. We propose utilization of reduced pressure induced by ultrasonic cavitation for improvement of the plasma production. Correlation between the plasma production and the ultrasonic power will be discussed.