• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.3
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• pp.26-31
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• 2006

Through the KOMPSAT program, Koreanization of thruster have been carried out successfully, but there are still many difficulties in Koreanization of most core parts of propulsion system. Because the development of core parts is essential to participate in the advanced nations, KARI has carried out development of Fill/Drain valve for propellant/pressurant supply of satellite, which has high possibilities to be koreanized, with Hanwha Corp.. This paper summarizes overall processes of development including design, manufacturing and test, and finally 4 sets of modules were successfully made. Also the satisfaction of performance requirements are verified through performance tests.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.1
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• pp.38-42
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• 2017

This study proposes an idea for energy saving in apartment machine rooms. A conventional district heating system is equipped with constant-flow pumps and bypass valves to regulate pump differential pressure. Each family unit is equipped with a constant-flow on/off valve. This leads to excessive hot water circulation and a high return temperature. To reduce energy loss, this study assumes that each family unit is renovated with a heating valve which regulates the return temperature at $35^{\circ}C$. The hot water supply pump is also replaced with a pump with an inverter to vary flow rate. Expected energy savings is then estimated from field test data. According to the results, pump electricity consumption was reduced by 6,100 kWh for a family unit building over about half a year. The supply temperature can also be lowered by $5^{\circ}C$, which can contribute to a production of electricity of 10.3 kWh/ton of hot water.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.4
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• pp.363-368
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• 2015

This paper deals with an improved current source using full-bridge converter type for thyristor valve test of HVDC system. The conventional high-current and low-voltage source of synthetic test circuit requires additional auxiliary power supply to provide the reverse voltage for the auxiliary thyristor valve during turn-off process. The proposed circuit diagram to provide the reverse voltage is extremely simple because no additional component is required. The reverse voltage can be obtained from the input DC voltage of the high-current and low-voltage power supply. The operation principle and design method of the proposed system are described. Simulation and experimental results in scaled down STC of 200 V, 30 A demonstrate the validity of the proposed scheme.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.876-881
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• 2004

In this study, A special quality analysis and experiment for low power consumption type pneumatic on-off micro valve was performed. And flow characteristics of the micro valve by stroke change was numerically investigated. As a result, it is shown that magnetic force(2.4N) is exerted enough to move poppet with 0.3mm stroke with 0.01 seconds of response time, and that there is no magnetic force emitted by yoke. Under the condition of poppet stroke smaller than about 0.8mm, dynamic pressure acts to poppet wall up to supply pressure level. But, that is decreasing to 40% when poppet stroke is 0.8mm.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.7
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• pp.697-702
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• 2000

This study is to investigate the pressure wave characteristics and the maximum pressure rise generated by instantaneous valve closure at the end of the straightening copper piping system. Experiments were conducted under the following conditions : initial pressure 1~5 bar, flow velocity 0.6~3.0 m/s and water temperature $20^{\circ}C$ . Results indicated that the peak pressure generated by quick valve closure reached Joukowsky's value. And we also found that the maximum pressure rise and the pressure history were depended on not only closing time but also flow velocity.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.77-82
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• 2009

If we can supply accurate minute flow rate to the households, we can solve many problems that are occurring in consequences of uncontrolled flow rate for the households. Therefore, this paper presents an innovative solution to the source of the problems by illustrating how we can control the flow rate to the household. This paper proves such problems even can be solved in a case when there is a room turned off the heating.

• Transactions of The Korea Fluid Power Systems Society
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• v.1 no.2
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• pp.15-19
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• 2004

In this study, Design and simulation for low power consumption type pneumatic on-off micro valve was performed. And flow characteristics of the micro valve by stroke change was numerically investigated. As a result, it is shown that magnetic force(6.8N) is exerted enough to move poppet with 0.438mm stroke with 0.01 seconds of response time, and that there is no magnetic force emitted by yoke. Under the condition of poppet stroke smaller than about 0.4mm, dynamic pressure acts to poppet wall up to supply pressure level. But, that is decreasing to 40% when poppet stroke is 0.8mm.

• Transactions of The Korea Fluid Power Systems Society
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• v.7 no.4
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• pp.15-22
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• 2010

The typical hydraulic hoisting system of the rack-bar type sluice gate is composed of a hydraulic supply unit using an uni-directional pump, a direction control valve, a hydraulic motor, a counter balance valve, and flow control valves. Here, the hydrostatic transmission is applied to the hoisting system of rack-bar type sluice gate to simplify the operation of gate such that the upward and downward direction of gate is simply controlled by the direction of pump rotation. The new hydraulic hoisting system is composed of a bi-directional pump, a hydraulic motor, a counter balance valve, two check valves, two pilot-operated check valves, two relief valves and a shuttle valve. The characteristics of a suggested system are analyzed by computer simulations and experiments.

• 유공압시스템학회:학술대회논문집
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• 2010.06a
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• pp.86-92
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• 2010

The typical hydraulic hoisting system of the rack-bar type sluice gate is composed of a hydraulic supply unit using an uni-directional pump, a direction control valve, a hydraulic motor, a counter balance valve, and flow control valves. Here, the hydrostatic transmission is applied to the hoisting system of rack-bar type sluice gate to simplify the operation of gate such that the upward and downward direction of gate is simply controlled by the direction of pump rotation. The new hydraulic hoisting system is composed of a bi-directional pump, a hydraulic motor, a counter balance valve, two check valves, two pilot-operated check valves, two relief valves and a shuttle valve. The characteristics of a suggested system are analyzed by computer simulations and experiments.

• The Transactions of the Korean Institute of Power Electronics
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• v.28 no.1
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• pp.76-81
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• 2023

A new test circuit for an MMC-based valve HVDC power converter is proposed. The proposed scheme satisfies the required clauses from IEC-62501. The valve test current contains second harmonic component and DC offset as well as a fundamental component that is quite similar to the real operating arm current of MMC based HVDC power system. The structure of the proposed test circuit is simple compared to conventional test circuits. Furthermore, the power supply voltage rating of the proposed test circuit is reduced dramatically around 20% of the conventional scheme with the same current rating. The validity of the proposed test circuit is verified through simulation and experimental results.