• 한국항해항만학회지
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• 제26권3호
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• pp.295-302
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• 2002

현재의 디지털 통신시스템은 매우 다양한 디지털 변조방식을 채택하고 있다. 이러한 통신시스템에서는 인접채널에 대한 간섭을 최대한 줄이기 위해서 필연적으로 선형 전력증폭기를 요한다. 선형 전력증폭기는 매우 다양한데 그 중에서 전방궤환 전력증폭기는 구조상 광대역이면서 선형화 정도가 매우 우수하다. 전방궤환 전력중폭기에 사용되는 지연선로의 손실로 인하여 전체효율이 감소한다. 본 논문에서는 이러한 지연선로를 손실이 매우 작은 지연필터를 사용함으로써 효율과 선형성을 동시에 개선하였다. 측정된 결과 ACLR이 약 17.43dB 개선되었으며 이것은 지연필터를 사용함으로써 2.54dB 더 개선되었음을 나타낸다.

• 한국레이저가공학회지
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• 제3권2호
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• pp.35-43
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• 2000

Laser direct patterning of the coated photoresit (PMER-NSG31B) layer was studied to make halftone dots on gravure printing roll. The selective laser hardening of photoresist by Ar-ion laser(wavelength : 333.6nm∼363.8nm) was controlled by the A/O modulator. The coating thickness in the range of 5㎛∼11㎛ could be obtained by using the up-down directional moving device along the vertically located roll. The width, thickness and hardness of the hardened lines formed under laser power of 200∼260㎽ and irradiation time of 4.4∼6.6$\mu$ sec/point were investigated after developing. The hardened width increased according to the increase of coating thickness. Though the hardened thickness was changed due to the effect of the developing solution, the hardened layer showed good resistance to the scratching of 2H pencil. Also, the hardened minimum line widths of 10㎛ could be obtained. The change of line width was also found after etching, and the minimum line widths of 6㎛ could be obtained. The hardened lines showed the good resistance to the etching solution. Finally, the experimental data could be applied to make gravure halftone dots using the developed imaging process, successfully.

• International Journal of Precision Engineering and Manufacturing
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• 제3권1호
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• pp.26-32
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• 2002

Laser direct patterning of the coated photoresist (PMER-NSG31B) layer was studied to make halftone dots on the gravure printing roll. The selective laser hardening of the photoresist by Ar-ion laser(wavelength: 333.6∼363.8 nm) was controlled by the A/O modulator. The coating thickness in the range of 5∼11㎛ could be obtained by using the up-down directional moving device along the vertically located roll. The width, thickness and hardness of the hardened lines farmed under the laser power of 200∼260mW and irradiation time of 4.4∼6.6 $\mu$ sec/point were investigated after developing. The hardened width increased as the coating thickness increased. Though the hardened thickness was changed due to the effect of the developing solution, the hardened layer showed good resistance to the scratching of 2H pencil. Also, the hardened minimum line width of 10㎛ could be obtained. The change of line width was also found after etching, and the minimum line widths of 6㎛ could be obtained. The hardened lines showed the good resistance to the etching solution. Finally, the experimental data could be applied to make gravure halftone dots using the developed imaging process, successfully.

• 대한전기학회논문지
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• 제37권5호
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• pp.272-281
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• 1988

The problem of optimal transmission system planning is to find the most economical locations and time of transmission line construction under the various constraints such as available rights-of-way, finances, the technical characteristics of power system, and the reliability criterion of power supply, and so on. In this paper the constraint of right-of-way is represented as a finite set of available rights-of-way. And the constructed for a unit period. The electrical constraints are represented in terms of line overload and steady state stability margin. And the reliability criterion is dealt with the suppression of failure cost and with single-contingency analysis. In general, the transmission planning problem requires integer solutions and its objective function is nonlinear. In this paper the objective function is defined as a sum of the present values of construction cost and the minimum operating cost of power system. The latter is represented as a sum of generation cost and failure cost considering the change of yearly load, economic dispatch, and the line contingency. For the calculation of operating cost linear programming is adopted on the base of DC load flow calculation, and for the optimization of main objective function nonlinear Branch-and-Bound algorithm is used. Finally, for improving the efficiency of B & B algorithm a new sensitivity analysis algorithm is proposed.

• Journal of Power Electronics
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• 제6권4호
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• pp.330-339
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• 2006

This paper deals with novel electronic ballast based on single-stage power processing topology using a symmetrical half-bridge inverter and current injection circuit. The half-bridge inverter drives the output parallel resonant circuit and injects current through the power factor correction (PFC) circuit. Because of high frequency current injection and high frequency modulated voltage, the proposed circuit maintains the unity power factor (UPF) with low THD even under wide variation in ac input voltage. This circuit needs minimum and lower sized components to achieve the UPF and high efficiency. This leads to an increase in reliability of ballast at low cost. Furthermore, to reduce cost, the electronic ballast is designed for two series-connected fluorescent lamps (FL). The analysis and experimental results are presented for ($2{\times}36$ Watt) fluorescent lamps operating at 50 kHz switching frequency and input line voltage (230 V, 50 Hz).

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.694-700
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• 1998

A novel zero-voltage-transition (ZVT) isolated PWM boost converter for single stage power factor correction (PFC) is presented to improve the performance of the previously presented ZVT converter[8]. A simple auxiliary circuit which includes only one active switch provides zero-voltage-switching (ZVS) condition to all semiconductor devices. (Two active switches are required for the previous ZVT converter) This leads to reduced cost and simplified control circuit comparing to the previous ZVT converter. The ZVS is achieved for wide line and load ranges with minimum device voltage and current stresses. Operation principle, control strategy and features of the proposed converter are presented and verified by the experimental results from a 1.5 kW, 100 KHz laboratory prototype.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.97-99
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• 2007

This paper presents a fuzzy logical control method to implement an on-line optimum efficiency control for Permanent Magnet Synchronous Motor. This method real-timely adjusts the output voltage of the inverter system to achieve the optimum running efficiency of the whole system. At first, the input power is calculated during the steady state in the process of efficiency optimizing. To exactly estimate the steady state of the system, this section needs check up the speed setting on timely. The second section is to calculate input power of dc-bus. The exact measurement of the voltage and current is the vital point to acquire the input power. The third section is the fuzzy logic control unit, which is the key of the whole drive system. Based on the change of input power of dc-bus and output voltage, the variable of output voltage is gained by the fuzzy logical unit. With the on-line optimizing. the whole system call fulfill the minimum input power of dc-bus on the running state. The experimental result proves that the system applied the adjustable V/f control method and the efficiency-optimizing unit possesses optimum efficiency, and it is a better choice for simple variable speed applications such as fans and pump.

• 전기학회논문지P
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• 제58권2호
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• pp.214-220
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• 2009

Battery is one of the emergency power and its reliability is a very important to keep up the minimum of building capabilities in case of interruption of electric power. This paper, a comparison was made between three different types of instrument on 30 valve regulated lead acid(VRLA) TYPE 12[V]/100[AH] batteries, and then their indicated measured values(impedance/conductance) were compared with the measured capacity of the battery. As a result, Measured value of instrument is strongly related to battery's capacity in the same group battery and Impedance/Conductance guide line for diagnosis of lead-acid battery's state of health(SOH) is a different from each battery guoup.

• 정보통신설비학회논문지
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• 제1권1호
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• pp.26-39
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• 2002

This paper describes design and implementation of home network control protocol for networked home appliances. The proposed network protocol has four-layered protocol structure and device-modem interface structure for the flexibility of modems based on power line communication. The standard message set is specified to guarantee the interoperability between various home appliances The proposed protocol can be easily implemented because it has minimum network overhead.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권9호
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• pp.584-589
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• 2000

We fabricated resistive superconducting fault current limiters (SFCL) based on YBCO thin films grown on a 2-inch diameter Al2O3 substrate. The current limiting element was 1 mm wide and 260mm long meander line prepared by standard photolithography. The minimum quench current of the current limiting element was about 8 Apeak. This SFCL sucessfully controlled the fault current below 14.3 Apeak at the voltage of 100 Apeak which is otherwise to increase up to 141 Apeak. The quench completion time was less than 3 msec. The temperature of the current limiting element rose to about 200 K in 3 cycles after fault. The SFCL showed reproducible quench during hundreds times of repeated experiments.