• Proceedings of the KSR Conference
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• 2011.05a
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• pp.82-92
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• 2011

This paper presents a PFC(Power Factor Correction) system to control the power factor of input current of the converter system which is working in the propulsion system of KTX high speed train. In the KTX train system, initially introduced from ALSTOM, the thyristor converter with phase controlling technique is adopted in the current fed type powering system. The input current induces harmonic losses highly because the waveform becomes rectangular shapes according to the filter inductor current increased as the train speed increasing gradually. Especially the interference with the signalling systems is severe concerned due to high current harmonics on the catenary line. To protect this problem, a frequency trap filter(notch filter) is operating with the input converter system. In this paper, an analysis work and PC simulation have been done on the PFC system to upgrade its performance and maintenance efficiency.

• Journal of the Korean Society of Propulsion Engineers
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• v.5 no.2
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• pp.8-15
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• 2001

In the continuing quest for increased turbomachinery efficiency, the part played by blade profile shape remains crucial. The application of a heated thin metallic film with CTA(constant temperature anemometer) to the measurements of the laminar and turbulent boundary layer behavior(shock-boundary layer-interaction) in a transonic wind tunnel. Results of measurements with hot-film sensors on transonic compressor blades are extremely difficult to interpret because of ambiguous probe signals due to the complexity of the local flow pattern. In order to get the explicit information and give the designer to interpret characteristic signals from hot-film probes, a method was developed by comparing the results with other measuring technic results.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2002.04a
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• pp.50-54
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• 2002

With a view to estimating the effect of flows on evolving sprays and combustion in ramjet combustor and corresponding extent of combustion, ram air flows in combustion chamber is numerically experimented. Preconditioned three dimensional Navier-Stokes system of equations per transient, compressible, turbulent flows in IRR(Integral Rocket Ramjet) combustor is numerically integrated. Flow properties in the side-dump ramjet combustor, rectangular duct with two 60-deg curved inlets located radially at an angle of 180-deg, are addressed in terms of mixing quality and extent of combustion efficiency.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.523-526
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• 2011

This is concerned with the structural reliability analysis(RA) considering uncertainties in material properties. This method is performed by the stochastic process using Kriging with calculating the distribution of probability and equation of limit state for saving calculated and analyzed time. The proposed methodology is applied to the rocket motor case and compared with monte-calro simulation in efficiency and accuracy of this process.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.92-95
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• 2011

A multi-step quasi-global mechanism is developed for the kerosene/oxygen combustion analysis including dissociation products. Reaction constants of the global reaction are determined to have agreement with experimental data. The mechanism is used for the numerical analysis of the combustion flow field of the kerosene/oxygen shear coaxial injector. The results from high-resolution numerical analysis confirmed qualitatively that the recess enhance the fuel/air mixing and combustion efficiency by the increased flow instabilities.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.40 no.3
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• pp.250-257
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• 1991

In the analysis of the electric machine by finite element method, the primary current has been selected as a driving source. But the voltage is constant and the primary current varies according to the load condition in the pracdtical system. Therefore, in this paper, magnetic flux distribution, primary current, input effective power, power factor, efficiency and propulsion force of S.L.I.M. were calculated by the finite element method cnsidering the voltage as a driving source. Because the driving characteristics could not be measured in the S.L.I.M., voltage-current curve, 3-phase current curve, and propulsion force were measured at the starting and they were compared with theoretical values.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.34-37
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• 2009

The present study presents a numerical methodology for early conceptual trade-off study between propulsive performance, cooling efficiency, weight and size, in which combustion and cooling precesses in regeneratively cooled rocket thrust chamber are interactively simulated. To address the capabilities and reliability of the design tool, some application results are given involving contour design, performance analysis, and wall cooling prediction as well as a systematic design evaluation.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.19-22
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• 2003

Ejector-diffuser system is one of fluid machinery which can entrain the fluid in low pressure part and transport it to the higher pressure part. The conventional ejector-diffuser system has been pointed out that its overall efficiency is quite low compared with other fluid machinery since it is derived by only the pure shear stresses. In the present study, 4, 6, and 8 lobed petal nozzles with a design Mach number of 1.7 are adopted as a primary nozzle to improve the performance, and are compared with a conventional circular nozzle.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.6
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• pp.566-572
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• 2015

This study introduces an LCC resonant converter operating on a continuous conduction mode. The LCC resonant converter has the advantage of improving system efficiency, especially under the rated load condition, because it can reduce conduction loss by improving the resonance current shape and switching loss by increasing the lossless snubber capacitance. The proposed LCC resonant converter is applied to various applications, including a 60 kW EV fast charger, a 24 kJ/s high-voltage capacitor charger, and a 20 kV, 20 kW high-precision DC power supply. Experimental results prove that the proposed LCC resonant converter topology can be effectively used as a converter topology for these applications.

• Proceedings of the KIEE Conference
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• 1998.07a
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• pp.152-154
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• 1998

This paper deals with propulsion system for the UTM-01(Urban Transit Maglev). We experiment about the LIM and the inverter at 4 running test maglev vehicle. It is measured voltage, current, power factor for inverter output. And we discussed about efficiency of the LIM about maglev system.