• The KSFM Journal of Fluid Machinery
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• 제18권1호
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• pp.37-43
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• 2015

A Beta-type Stirling engine is developed and tested on the operation stability and cycle performance. The flow rate for cooling water ranges from 300 to 1500 ml/min, while the temperature of heat source changes from 300 to $500^{\circ}C$. The internal pressure, working temperatures, and operation speed are measured and the engine performance is estimated from them. In the experiment, the rise in the temperature of heat source reduces internal pressure but increases operation speed, and overall, enhances the power output. The faster coolant flow rate contributes to the high temperature limit for stable operation, the cycle efficiency due to the alleviated thermal expansion of power piston, and the heat input to the engine, respectively. The experimental Stirling engine showed the maximum power output of 12.1 W and the cycle efficiency of 3.0 % when the cooling flow is 900 ml/min and the heat source temperature is $500^{\circ}C$.

• The Transactions of the Korean Institute of Electrical Engineers P
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• 제59권4호
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• pp.477-480
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• 2010

Fault current in power system is expected to increase by demand of power capacity. Therefore, when the fault occurred, fault current was increased in the power system. Many studies have been progressed to limit the fault current. Superconducting fault current limiter (SFCL) is one of them which has been studied in worldwide. In this paper, we will analyze characteristics of a transformer-type SFCL by reclosing operation when the voltage increases. Twice opening times in the reclosing of circuit breaker were set as the 0.5 and 15 seconds, respectively. Turn's number of primary and secondary coils set 4:2 and we increased voltages from 120V to 280V for each experiment. By the current waveform, maximum fault current in second and third cycles was lowered when the voltage was increased. In the recovery waveform, recovery time was increased as the voltage was increased. The reason was that power burden of the SFCL increased when consumption power was increased, so the time to get back to SFCL took longer. We compared the characteristics of a resistive-type and transformer-type SFCL. As a result, we found that the fault current of a transformer-type was lower than resistive-type and recovery time of the SFCL was shorter. Consequently, transformer-type SFCL was more profitable for limitation of fault current and recovery time under the same condition for reclosing operation.

• Proceedings of the KIEE Conference
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1664_1665
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• 2009

Many years ago, most of thermal power plants built in this country were of subcritical pressure, of medium or small size, of constant pressure operations and of drum type steam generators with circulation type boilers. But, nowadays almost all of them were of high efficiency, of supercritical pressure, of big capacity, of sliding pressure operations, and of once through type steam generator. It has such advantage as the reduction of startup duration, but it control system and operation method are very complicated. It has a big difference in operation method of turbine and boiler. The feedforward control needs to be introduced to prevent such problems as thermal shock during the transit from normal operation into bypass operation. This paper introduces the turbine control and turbine bypass control during startup of thermal power plants.

• Proceedings of the KIPE Conference
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(1)
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• pp.189-192
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• 2003

Electrical power in satellite system should persistently satisfy specified power requirement even though that happen the failure of solar array string or battery cell during the mission operation. In this study, the solar array and battery of GEO Communication Satellite with 3kW capacity are designed, and energy balance analysis according to power operation mode are performed to meet specified power capacity at the transfer orbit

• Korean Journal of Agricultural Science
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• 제48권4호
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• pp.1039-1050
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• 2021

The purpose of this study is to measure load data for a 55 kW class agricultural tractor during a harvesting operation and to analyze the required power according to the working conditions. A field test was conducted at three different tractor speeds (1.2, 1.3, and 1.4 km·h^-1). A load measurement system was developed for the front axles, rear axles, and for power take-off (PTO). The torque and rotational speeds of the axles and PTO were measured during the field test and were calculated as the required power. The results showed that the total required power was in the range of 4.86 - 5.48 kW during the harvesting operation according to the tractor speed, and it was confirmed that this represents a ratio of 8.8 - 10.0% of the engine rated power. Also, it was confirmed that the required power of the axle and PTO increased as the tractor speed increased. In future studies, we plan to supplement the measurement system for a tractor to include a hydraulic system and perform a field test for harvesting various underground crops.

• KIPS Transactions on Computer and Communication Systems
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• 제3권9호
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• pp.273-278
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• 2014

Recent use of electricity during peak hours electricity supply-demand imbalance is inevitable that limit power use force. Therefore, in this paper, a circuit of parallel power operation equipment for peak power reduction which saves the power to electricity storage device during the non-peak power time and supply from the storage power during the expected power shortages time is designed Through this circuitry, the peak power of the commercial power supply with the parallel operation and connection of the commercial power supply and the power supply of the inverter from electricity storage that is a key feature of PRS(Peak power Reduction System) can be controlled. In addition, in order to increase the efficiency, a Transless Power Circuit DC-AC inverter is developed. Moreover, a variable impedance control is applied to the storage of electric power of an Uninterruptible Power Supply associated with a commercial power source.

• Journal of Electrical Engineering and Technology
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• 제7권3호
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• pp.304-311
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• 2012

So far, the importance for an accurate load model has been constantly raised and its necessity would be further more emphasized. Currently used load model for analysis of power system in Korea was developed 10 years ago, which is aggregated by applying the statistically estimated load compositions to load models based on individual appliances. As modern appliances have diversified and rapidly changed, the existing load model is no longer compatible with current loads in the Korean power system. Therefore, a measurement based load model is more suitable for modern power system analysis because it can accurately include the load characteristics by directly measuring target load. This paper proposes a ZIP model employing a Kalman-filter as the estimation algorithm for the model parameters. The Kamlan-filter based parameter identification offers an advantage of fast parameter determination by removing iterative calculation. To verify the proposed load model, the four-second-interval real data from the Korea Energy Management System (K-EMS) is used.

• Journal of Power Electronics
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• 제12권3호
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• pp.487-494
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• 2012

A new low cost high power density photovoltaic power conditioning system (PV PCS) with an energy storage system is proposed in this paper. Its high power density and cost effectiveness can be achieved through the unification of the maximum power point tracker and the battery charger/discharger. Despite the reduced power stage, the proposed system can achieve the same performance in terms of maximum power point tracking and battery charging/discharging as the conventional system. When a utility power failure happens, the proposed system cannot perform maximum power point tracking at the UPS mode. However, the predetermined battery voltage near the maximum power point of the PV array can effectively generate a reasonable PV power even at the UPS mode. Therefore, it features a simpler structure, less mass, lower cost, and fewer devices. Finally, to confirm the operation, validity, and features of the proposed system, a theoretical analysis and experimental results from a single phase AC 220Vrms/1.5kW prototype are presented.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 한국추진공학회 2005년도 제24회 춘계학술대회논문집
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• pp.92-95
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• 2005

The present work has been developed the type of non-electric and delay explosive bolt which does not need power supply device and has the delay function in the operation of the explosive bolt. Separation device system could be minimized because of non-electric power supply system. In order to prove the mechanism of operation, the present work used to ignite the initiator the power of air resistance caused front aviation object. we can be founded from the present work that the changes in the operation load influence directly the ignition of the initiator. The design of non-electric and delay explosive bolt is the most suitable the separation system necessary to reduce the velocity of aviation object and safe landing of parachute system.

• The Transactions of The Korean Institute of Electrical Engineers
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• 제61권10호
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• pp.1496-1501
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• 2012

A fine tuning on a control system is essential not only for stable operation but also for efficient operation of the power plant. There has been a very few studies on efficiency change by control system tuning. So, it was not clear that if it could be improved or not when the control is stable by fine tuning and how much it could be improved if it works. An accurate algorithm for measurement of the plant efficiency was newly introduced and implemented to measure integrated fuel flow and electricity MW output and to calculate the mean efficiency for given time. As a result, stable operation after fine tuning of control parameters for major controlled variables brought higher efficiency than un-stable operations like a cycling or an oscillation. The plant efficiency has been monitored during various tests and tunings to confirm how much it changes by tuning of the control system on power plant. Now, we can say that the efficiency can be improved in stable operation by fine tuning of the control system.