• 한국항해학회지
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• 제6권2호
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• pp.35-55
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• 1982

The attempt of this paper is to examine the basic theory on the analysis of the effect of a shading coil fitted to an electromagnetic contactor, and to compare experimentally the attracting force of an AC electromagnetic contactor with that of a DC electromagnetic contactor, with varying the airgap length. Equations are also proposed for calculating the AC and DC attracting force per unit consumption wattage by using the circuit constants measured from the experiment, and these calculated attracting forces are compared with those actulally measured, and then, the experimental contactor is examined in the view of its design. The calculated attracting forces are appeared to coincide well with the measured ones and the experimental contactor fitted with shading coil is revealed not so well designed for reducing the fluctuation of the attracting force.

• 한국물환경학회지
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• 제26권4호
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• pp.585-589
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• 2010

In order to evaluate the performance of a powdered activated carbon (PAC) contactor, two water treatment plants (WTP) were selected as target sites. The result of tracer tests showed that the plug flow portion of a bisymmetry-type contactor (H WTP) was more than 70%. A maze-type contactor (C WTP) also had more than 70% of plug flow portion after intra-basin baffles were installed. According to the operating data of the target WTPs, there was no clear evidence that the addition of PAC contributed to the removal of organics. However, the results of jar tests, conducted with the raw water taken from the H WTP, proved that PAC could remove dissolved organic carbon (DOC) to some extent when the proper velocity gradient was maintained. It was estimated that the production rate, defined as the ratio of the operating flowrate to the design flowrate, of the C and H WTPs was only 27 and 50%, respectively. Because of these lower production rates, the mixing intensity in the contactor was much less than the designed value and, finally, the performance of the PAC contactor was much lower than what was expected.

• 환경위생공학
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• 제14권4호
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• pp.41-49
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• 1999

The water treatment by was performed to remove VOC and organic substances in the multi-stage ozone contactor. Ozone is mainly utilized to change the chemical structures of organic substance, of which finally has the purpose to degrad them. The removal efficiency of VOC has 20~60% at the ozone concentration of 3 ppm, in case of trichloroethylene, its efficiency is reduced by 85% at the ozone contact time of 8 min. Design factors such as the number of stage, ozone concentration, zone contact time are determined for optimal treatment in the multi-stage contactor.

• Journal of Advanced Marine Engineering and Technology
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• 제8권2호
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• pp.67-73
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• 1984

The Author researched and published its results on how effectively the arcs suppressed when the contactors are opened at current zero point which indispensively exsists in AC circuits. In order to increase the effectiveness of suppressing the arcs in larger current, the author suggests a new suppressing method using auxiliary contactor which contains resistance which is connected in parallel with main contactor. The author's firm belief is that the arcs are suppressed remarkably, but there are several problems, especially how to determine the optimal resistance connected in series with auxiliary contactor.

• Journal of international Conference on Electrical Machines and Systems
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• 제3권4호
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• pp.481-486
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• 2014

The demand for a DC power distributed system is increasing as renewable energy sources and DC electrical load are proliferating. For the automation of a power system, a magnetic contactor for the DC power system is required. The conventional magnetic contactors are mostly equipped with a solenoid magnetic actuator. However, the conventional magnetic contactor has problems with continuous power consumption, and heat generation. To address these problems, a permanent magnet type DC magnetic contactor is proposed in this paper.

• 환경위생공학
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• 제15권1호
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• pp.14-24
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• 2000

The water treatment by ozone was performed to remove VOC and organic substances in the multistage ozone contactor. This paper is secondary paper about the theme of ozone treatment since the first paper (Kor. Sanitary J., 15, 1(2000)) publicized, it was compared experimental results with theoretical those which were derived from the mathematical model associated with chemical reactions and mass transfer. Basic designing factors were determined as an optimal conditions for the removal rate of VOCs as follows: ozone input concentration in the contactor was 2mg/L, ozone contact time was 7 min and number of contactor was three-layered.

• 상하수도학회지
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• 제24권5호
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• pp.519-525
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• 2010

From the results of tracer test for the existing chlorine contactor in Y water treatment plant, $T_{10}$ and $T_{10}$/T were calculated as 130 min and 0.16, respectively. Therefore it required the modification schemes for improving hydraulic efficiency, surrogated by T10 and $T_{10}$/T, and disinfection performance. In this study, in order to reduce dead zone within contactor, the installation of porous baffles in the near of each corner was suggested and verified using transient CFD(Computational Fluid Dynamics) simulation technique and tracer tests on dynamic condition. From the results of simulation and tracer tests, it was revealed that porous baffles installed have been effective to reduce dead zone within contactor, and increase plug flow fraction.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.42-44
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• 2001

This paper proposes impact vibration theory of magnetic contactor moving mechanism and correlation test the bouncing time with the spring load. Mechanical and electrical lifetime is under the influence of impact vibration of magnetic contactor moving mechanism. In shortage of technique, we have experienced many difficulties in magnetic contactor development. By this research, we analyzed total moving mechanism and applied results to optimum 4p magnetic contactor development.

• 한국신뢰성학회지:신뢰성응용연구
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• 제17권4호
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• pp.316-324
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• 2017

Purpose: The purpose of this study is to determine the replacement cycle applied age replacement policy by reliability analysis based on railway vehicle contactor's failure history data. Method: We performed reliability analysis based on railway vehicle contactor's failure history data. We found a suitable distribution by goodness of fit test and predicted the reliability through estimation of scale & shape parameter. Considering cost information we determined the replacement cycle that minimize the opportunity cost. Result: Suitable distribution was the Weibull and scale parameter & shape parameter are estimated by reliability analysis. The replacement cycle was predicted and MTTF, $B_6$ percentile life were suggested additionally. Conclusion: We confirmed that failure rate type of railway vehicle contactor is degradation model having a time dependent characteristic and examined the replacement cycle in our country's operating environment. We expect that this study result contribute to railway operation agency for maintenance policy decision.

• 상하수도학회지
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• 제18권5호
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• pp.656-665
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• 2004

An Ozone reaction model combined with CFD(Computational Fluid Dynamics) technique was developed in this research, in the simulation of ozonation, hydrodynamic behavior as well as reaction model is important because ozone is supplied to treated water as gas ozone. In order to evaluate hydrodynamic behavior in an ozone contactor, CFD technique was applied. CFD technique elucidated hydrodynamic behavior in the selected ozone contactor, which consisted of three main chambers. Three back-mixing zones were found in the contactor. The higher velocities of water were observed in the second and third compartments than that in the first compartment. The flow of the opposite direction to the main flow was observed near the water surface. Based on the results of CFD simulation, the ozone contactor was divided into small compartments. Mass balance equations were established were established in each compartment with reaction terms. This reaction model was intended to predict dissolved ozone concentration, especially. We concluded that the model could predict favorably the mass balance of ozone, namely absorption efficiency of gaseous ozone, dissolved ozone concentration and ozone consumption. After establishing the model, we discussed the effect of concentration of gaseous ozone at inlet, temperature and organic compounds on dissolved ozone concentration.