• Journal of Advanced Marine Engineering and Technology
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• v.38 no.10
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• pp.1225-1231
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• 2014

This paper presents the performance characteristic of a Francis hydro turbine with an inline casing. This turbine is designed for city water supply system. Due to large changes in ground elevation with high points and low points, some systems may experience larger-than-normal required pressures in areas with low ground elevations. One way to dissipate these excess pressures is by the use of an inline-turbine instead of an inline-pressure reducing valve. For best applicability and minimal space consumption, the turbine is designed with an inline casing instead of the common spiral casing. As a characteristic of inline casing, the flow accesses to the runner in the radial direction, showing a low efficiency. The installation of vanes improves the internal flow and gives the positive encouragement to the output power. For the power transmission to the outside of the turbine casing from the runner axis, a belt passage is designed in the inline casing, as its influence, the region after the belt passage shows a relatively low output power. The clearance gap in the runner side space is considered, in which a small volume of flow is contracted into the clearance gap, forming the leakage flow. The leakage flow leads to a decrease in the efficiency.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.1
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• pp.436-440
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• 2014

To verity the effect of PCB plane layer to the output characteristics of the Switched Mode Power Supply (SMPS), this paper compared with a generic one-layer PCB and a double-side PCB. This paper specially focused on the voltage, the current and the high frequency noise of the output characteristic of the SMPS, using a double-side PCB which has same layout and was installed a ground plane on the opposite side. This double-side PCB was assembled by all same components which used on the SMPS using the single-side PCB. The experiment results show the SMPS using the ground plan PCB can efficiently reduce the high frequency noise to 50mV at 100MHz from 150mV in the single-side PCB. And the results also show the high harmonics frequency was reduced as well.

• Journal of the Korean Geophysical Society
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• v.6 no.3
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• pp.179-188
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• 2003

The object of grounding of electrical facility is to protect human and machine damage from the power supply interruption high voltage by use of the accident current dissipating into the ground. Generally, it is not easy to make suitable ground design for inhomogeneous subsurface geology and the variability of accident current in magnitude and duration time. To make efficient ground, ground potential rise must be controlled in the way of overall lowering and evenness. This study shows the case of optimized ground design by use of subsurface resistivity structure from electrical soundings.

• Proceedings of the KIEE Conference
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• 2009.04a
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• pp.6-9
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• 2009

Recently, there have been studied the importance of the grounding system, as electrical equipments installed in the building, such as intelligent building. The object of grounding of electrical facilities is to protect human and machine damage from the power supply interruption high voltage by use of the accident current dissipating into the ground. In this paper, we is proposed to design of grounding system with economical efficiency in electric rolling stocks facilities. To make efficient ground, ground potential rise must be controlled in the way of overall lowering and evenness instead of independent grounding method with respect to electrical facilities.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.3
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• pp.120-127
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• 2004

With the proliferation of nonlinear loads such as switching mode power supplies, high neurtral harmonic currents in three-phase four-wire distribution system have been observed. It has been known that the grounded impedance has an effect on the neutral current of a system which operates with harmonics present since the neutral conductor is grounded. On-site measurements of harmonic currents and voltages were made and the corresponding equivalent circuit was developed. The circuit model under study was simulated numerically and graphically through the use of the software MATLAB. Simulation results verifying the relationship between the neutral harmonic current and ground impedance are presented.

• Fire Science and Engineering
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• v.34 no.3
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• pp.43-48
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• 2020

The purpose of this study is to develop an earth leakage alarm circuit breaker, equipped with a leakage alarming function (JER-E2S, ETECKOREA Co., Korea), and to analyze its characteristics. The developed mechanism is exclusively used for single-phase and 220 V circuits, with a rated current of 32 A, 20 A, 20 A (for restrooms), 16 A, etc. It satisfies all characteristics of existing earth leakage circuit breakers (ELB). If a fire current, which is a resistive leakage current (Igr), flows through an electric line, the device detects the leakage current in real time and warns against the leakage through a blinking LED lamp. Since the developed device displays a tolerance to a capacitative leakage current (Igc) that inevitably occurs in LED lamps, communication devices, etc., it ensures a stable power supply. In addition, the earth leakage alarm circuit breaker protects against power failure due to a momentary ground fault. Therefore, it can supply power without the risk of the circuit breaker malfunctioning due to a momentary ground fault caused by water droplets, leaves, etc. Moreover, with a standby power of less than 0.1 W, the developed earth leakage alarm circuit breaker exhibits a power saving performance that is 3~8 times greater than that of other ELBs. Installation of approximately 10 earth leakage alarm circuit breakers in one apartment household, with an area of 120 ㎡, can save 2~5 kWh per month. Therefore, the developed earth leakage alarm breaker not only satisfies the characteristics of existing earth leakage breakers, but also exhibits outstanding power supply quality since it has the functions of electric fire prevention and malfunction prevention. Therefore, this device can innovatively contribute to electric fire prevention.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.36C no.8
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• pp.10-21
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• 1999

This paper describes a 12bit CMOS current cell matrix D/A converter which shows a conversion rate of 65MHz and a power supply of 3.3V. Designed D/A converter utilizes current cell matrix structure with good monotonicity characteristic and fast settling time, and it is implemented by using the tree structure bias circuit, the symmetrical routing method with ground line and the cascode current switch to reduce the errors of the conventional D/A converter caused by a threshold voltage mismatch of current cells and a voltage drop of the ground line. The designed D/A converter was implemented with a $0.6{\mu}m$ CMOS n-well technology. The measured data shows a settling time of 20ns, a conversion rate of 50 MHz and a power dissipation of 35.6mW with a single power supply of 3.3V. The experimental SNR, DNL, and INL of the D/A converter is measured to be 55dB, ${\pm}0.5LSB$, and ${\pm}2LSB$, respectively.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.332-338
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• 2008

This paper handles, implementation of multiple access bidirectional serial communications protocol using two common DC power lines, whict are power supply and ground, connecting multiple devices. Communication between the host and the multiple clients are performed using unique packet data with device ID unique to each devices connected on the common power lines. Host initiates data communications by transmitting command packet to the designated client with the client's ID and the client responds by transmitting response packet to the host and in this way, multiple clients and host exchange the packet through the common power lines. The normal voltage of the power communication line maintains 24V corresponding to level 1 and the host drops the voltage to 12V on sending level 0 signal, also the clients normally keeps the line voltage to 24V use pull-down circuit to drop the voltage to 12V on sending level 1 signal. Power supply originates from the host, the host senses the voltage level of the power communication lines and when the clients activates pull down circuit to send level 0 signal and the voltage drops to 12V, the hosts switches power source from 24V to 12V. Also, when clients deactivate pull down circuit to send level 1 signal, the host senses the voltage increase and switches the power source from 12V to 24V. Experimental circuit is designed with one hosts and four clients and verified the power line voltage switching operation depending on the data signal levels on the power line. The proposed research result can be applied to two wire power communications system with one host and multiple low current consumption clients.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.03a
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• pp.65-72
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• 2001

Since Pyoungtaek thermal power plant began using natural gas in 1986, the annual using volume has rapidly increased and reached 12.7 million tons in 1999. When the natural gas is cooled to a temperature of approximately -162$^{\circ}$C at atmospheric pressure, it condenses to a liquid called liquefied natural gas(LNG). LNG has a special characters such as odorless, colorless, non-corrosive, and non-toxic. So, LNG storage tank, tanker ship, transfer pipelines are required the special storage and transportation systems and technology. The presently operating LNG terminals are Pyongtaek and Inchon terminals. A total of 19 above-ground LNG storage tanks(100 thousand ㎘ grade) are currently in operation with a sendout capacity of 4,360tons/hour. To meet the growing domestic demand of LNG supply, the Inchon receiving terminal is expanding(six in-ground tank) and constructing a third LNG terminal at Tongyong. In this paper, case study on seepage analysis and countermeasure against increasing the seepage volume of in-ground LNG storage tank excavation work is reported. The results of an additional seepage analysis are presented to verify the design seepage volume of assumption section and seepage volume after curtain-grouting in the slurry wall.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.7
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• pp.1048-1056
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• 2001

Decoupling capacitors are commonly used to reduce the effect of SSN propagated through parallel power and ground planes in high-speed multilayer printed circuit boards (PCBs). In this paper, we introduced a simple high frequency measurement and proposed a wideband (50 MHz ∼3 GHz) equivalent circuit model for decoupling capacitor considering high frequency parasitic effects. The proposed model can be easily combined with the SPICE model of power supply planes far SSN analysis. The circuit simulations with the proposed model show good agreement with the measurement results. Also, we expect to accurately analyze the noise reduction effect as a function of value and location using the proposed model of decoupling capacitor.