• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.1
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• pp.89-95
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• 2015

A surge phenomenon cause noise and pulsations in a turbo compressor, which is an unstable operating regime. Because surge protection ensures a safe compressor operation, it is important to understand the physics of the surge phenomenon. In this study, the surge characteristics of a 250-hp class turbo-compressor were evaluated experimentally. The experimental parameters were the rotational speed, opening angles of the inlet guide vane and exit valve, and inlet pipe diameter and flow rates of the inlet gases. The results showed that the compressor surge was very sensitive to the gas flow rates, exit pressure, rotational speed, and bypass flow rates.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.11 no.4
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• pp.109-116
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• 1997

This paper describes the surge protective device combined with varistor and LC low pass filter on AC power circuits. Up to now varistors alone have been used as a surge protective device on AC power circuits, but it gives negative effects on the equipments to be protected due to the steep rise and high remnant voltage. Therefore in this work, for the purpose of improving the cutoff performance of surge protective device on AC power circuits, the hybrid-type surge protective device with varistor and LC filter was designed and prepared. And the experiments for operational characteristics and clamping performance of the surge protective device were carried out with an 1.2/50[$\mu$s] impulse generator. As a result, the proposed surge protective device with the combination of varistors and LC filter can limit the surge voltage to lower value and reduce the value of dV /dt to very small values. Also the attenuation of high-frequency voltages across the output port is effectively provided by LC filter. Therefore this result may be all the more helpful avoiding both damage and upset of electronic systems.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.1
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• pp.25-37
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• 2015

Tide-surge interaction during typhoon periods has been analyzed. The quantitative analysis of the Chi-square test shows that the interaction is most prominent at the Southwestern coast whereas the Western and the Southeastern regions are not. Patterns of surge type were divided into two groups, that is, steep type and mild type. Then, the interaction was turned out to be more prominent for mild type data. The weak interaction at the Western region is considered due to negative surges when the south-track typhoons attack. However, the interaction is remarkable when the west-track typhoons attack. The weak interaction at the Southeastern coast is, on the other hand, considered due to abundance of the steep type typhoons. Thus, inundation risk would be so apprehensive at that region because large-scale surge might be caused even at high tide.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.2065_2066
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• 2009

In this paper, we have developed high performance SPD(surge protective device) and evaluated the characteristics in comparison with typical SPD used in the inside and outside of the country. The new SPD was composed of MOV(metal oxide varistor), GDT(gas discharge tube) and impedance such as resistors, capacitors or varistors. To estimate operating the characteristic of the SPD which was developed, it was measured surge voltage caused by fault current or surge according to IEC 61000-4-5. As a result it was found that the power supply was cut off by high performance SPD when caused a short-circuit. In addition we could know that it could prevent ELB(earth leakage breaker)'s malfunction caused by surge.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1810-1812
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• 1996

This paper deals with the surge protective devices to minimize damages of communication equipments in signal data lines. The basic circuit consists of zener diodes, spark gap and series impedances. Therefore the hybrid circuit using bipolar zener diodes as clamps and a three-electrode spark gap as crowbars was proposed. The surge suppression performances and the characteristics of frequency response were investigated experimentally. Consequently, it was found that the frequency bandwidth and surge suppression performances are excellent.

• The KSFM Journal of Fluid Machinery
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• v.11 no.1
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• pp.33-39
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• 2008

Hybrid power generation systems combining a solid oxide fuel cell and a gas turbine is promising due to their high efficiency. In the pressurized hybrid system, the operating condition of the gas turbine may play a critical role in designing the hybrid system. In particular, prevention of surge of the compressor can be a critical issue. The existence of fuel cell between the compressor and the turbine may cause an additional pressure loss and thus compressor operating points tend to approach the surge if the original turbine inlet temperature is pursued. In this study, bypassing some of the turbine inlet gas directly to the turbine exit side is simulated. Its effects on suppressing the surge problem and change in performance characteristics are discussed.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.2
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• pp.69-74
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• 2004

In general the surge pressure generated in hydraulic systems causes noise, vibration and odd effect to the system. To reduce the surge pressure, high frequency PWM control of 20KHz was attempted. To estimate the braking noise caused by surge, a vehicle equipped with on-board ABS hydraulic modulator has been experimented with respect to the various breaking condition. Thorough this experiments, it was found that breaking noise has been reduced using high frequency PWM control method compare with low frequency method. To evaluate high frequency control m practice, including verification of general functionality, EMI tests was experimented. Its was found that it is necessary to have the solution to electromagnetic interference(EMI) generated by switching elements.

• Proceedings of the KIEE Conference
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• 1997.07e
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• pp.1642-1644
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• 1997

The simulation study of lightning faults reducing effects by the installation of surge arresters on the 154 kV transmission line is stated here. For the purpose of detailed simulation of arcing horn, a flashover model with dynamic characteristics of arcing horn gap was represented as a non-linear inductance which is controlled by EMTP/TACS(Electromagnetic Transient Program/fransient Analysis of Control Systems) switches. The back flashover inducing current was increased from 50 kA to 88 kA by the installation of surge arresters on the transmission line which has one ground wire and 20 ohms of tower footing resistances. The great advantage of surge arrester installation on one circuit of the double circuit transmission line is to prevent the simultaneous back flashover up to 190 kA.

• Nuclear Engineering and Technology
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• v.40 no.3
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• pp.239-250
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• 2008

If there is a water flow with a range of temperature inside a pipe, the wanner water tends to float on top of the cooler water because it is lighter, resulting in the upper portion of the pipe being hotter than the lower portion. Under these conditions, such thermal stratification can play an important role in the aging of nuclear power plant piping because of the stress caused by the temperature difference and the cyclic temperature changes. This stress can limit the lifetime of the piping, even leading to penetrating cracks. Investigated in this study is the effect of thermal stratification on the structural integrity of the pressurizer surge line, which is reported to be one of the pipes most severely affected. Finite element models of the surge line are developed using several element types available in a general purpose structural analysis program and stress analyses are performed to determine the response characteristics for the various types of top-to-bottom temperature differentials due to thermal stratification. Fatigue analyses are also performed and an allowable environmental correction factor is suggested.

• Journal of the Korean Society of Safety
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• v.28 no.5
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• pp.15-20
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• 2013

This paper dealt with melting characteristics of low-voltage miniature cartridge fuse used for 220 V electronic equipment. The experimental sample is low-voltage miniature cartridge fuse with rating of 250 V(3A) and size of $5{\times}20$ mm. In order to evaluate melting and scattering characteristics of the fuse, we applied to 8/20 ${\mu}s$ surge current, overload current and external thermal stress such as flame of fire. From the experimental results, the fuse element was melted and scattered by applied surge current(above 0.79 kA) and overload current(above 4.5 A). It was also attached to the inner surface of the fuse tube. The fuse element was attached as a thin film on inner surface of fuse tube when large surge current was applied. It was confirmed, however, the fuse element was not changed by external thermal stress such as flame and hot-air.