• Journal of KSNVE
• /
• v.9 no.2
• /
• pp.317-323
• /
• 1999

Dynamic characteristics of catenary that supplies electrical power to high-speed trains are investigated. A simple catenary is composed of the contact and messenger wires connected by droppers possessing bi-directional stiffness properties. For slender, repeating structures such as catenary, both the wave propagation and vibration properties need to be understood. The influence of parameters that determine catenary dynamics are investiaged through numerical simulations involving finite element models. The effects of the tension and flexural rigidity of the contact wire is first investigated. The effects of dropper characteristics are then investigated. For linear droppers wave propagation as well as modal properties are determined. For large catenary motion, droppers can be modeled as bi-directional elements possessing low stiffness in compression and high stiffness in tension. For this case, impulse response is computed and compared with the cases of linear droppers. It is found that the catenary dynamics are primarily determined by contact wire tension and dropper properties, with large responses observed in 5∼40 Hz frequency range. In particular, the dropper stiffness and spacing are found to have dominant influence on the response frequency and the wave transmission characteristics.

• 전기의세계
• /
• v.18 no.6
• /
• pp.23-32
• /
• 1969

The thesis has derived the formulas and computational algorithms useful for predicting and constraining the potential rises on the neutral line in 3-phase, 4-wire distribution line systems in the case of contact faults and single-line grounding faults. In addition it has suggested economically optimal designing conditions herewith of the distribution line systems in conduction with the potential restraining cost functions.

• Proceedings of the KSR Conference
• /
• 2004.06a
• /
• pp.909-914
• /
• 2004

This study investigate the cause analysis on fracture of dropper clamp in catenary system. Dropper clamp is using as a holder between messenger wire and contact wire in catenary system. To analyze the cause analysis on fracture of dropper clamp, we have conducted experiment such as tension withstand strength test, holding strength test of a new products, SEM and EDX of field fractured specimens.

• Proceedings of the KSR Conference
• /
• 2008.11b
• /
• pp.1279-1284
• /
• 2008

This paper presents the operating characteristic of high voltage impulse(HVI) track circuit owing to the ill-contact of impedance bond lead wire. The characteristic operations of the track include rail voltage and current. Measurements are carried out using oscilloscope with current probe and it analyzed the abnormal operation due to connector of protective wire. Finally, suitable track circuit is proposed for conventional line, and operating characteristic of HVI track circuit is affected by bypass circuit.

• Design & Manufacturing
• /
• v.10 no.1
• /
• pp.19-25
• /
• 2016

Connectors are very important components that transmit electric signals to different parts. It must maintain intensity of the connector to prevent defects from impact and maintain contact to transmit electric signals. Most of the external parts of the connector, which act as the main framework, are formed by injection molding. However, bend deformation occurs for injection molded products due to the residual stress left inside the product after product molding. When the bend deformation is large, it does not come into complete contact when being assembled with other parts, which leads to connector contact intensity not being properly maintained. In result, the main role of the connector, which is to transmit electric signals, cannot be performed. In order to address this problem, this study conducted bend deformation cause analysis through bend deformation analysis to predict and prevent bend deformation of housings and wafers, which are injection molded products of pressure welded connectors that are normally applied in compact mobile and display products. Bend deformation analysis was carried out by checking the charging time, pressure distribution and temperature distribution through wire to board connector wafer and housing injection molding analysis. Based on the results of the bend deformation analysis results, the cause of the bend deformation was analyzed through deformation resulting from disproportional cooling, deformation resulting from disproportional contraction, and deformation resulting from ingredient orientation. In result, it was judged that the effects for bend deformation were biggest due to disproportional contraction for both the pressure welded connector wafer and housing.

• Proceedings of the KSR Conference
• /
• 2006.11b
• /
• pp.821-831
• /
• 2006

There are 5 railway bridges in a Seoul metro network; Jamsil, Dangsan(line 2), Dongho(line 3), Dongjak(line 4) and Chungdam(line 7). Because there are strong wind and vibration in the bridges, uplift of a contact wire caused by pantographs in the bridge section is higher than in a normal section. If the uplift at the support point exceed 10 cm, an interference between pantographs and catenary system happens. Estimated maximum uplift is obtained by applying safety factor 2 to the simulation results. The application of the safety factor is needed for taking into account of the effect of the wind, etc. Previously, we can not check whether or not the safety factor is proper. Recently, we can measure the uplift during the train operation, as a telemetry system which can measure dynamic behavior of the contact wire has been developed. The aim of this research is to review how proper the safety factor related to the uplift is, based on the measurement. We performed simulations and experiments for the uplift at the Jamsil railway bridge. The simulations were performed for the every kind of the train passing the Jamsil bridge. In order to compare the analysis results with the measurement results, we measured the uplifts at the support when the trains passed the measuring point. Finally, we proposed adequate safety factor with the uplift for the bridge section.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.33 no.4
• /
• pp.1281-1293
• /
• 2013

A sophisticated finite element model is illustrated to analyze the behavior of Prefabricated Parallel Wire Strand(PPWS) sockets for main cables of suspension bridges. An orthotropic model is proposed for the casting material by considering both effects of individual wires and a casting alloy, and the contact between surfaces of a socket and a casting alloy is idealized by using the Coulomb friction and the surface-based contact model. The proposed FE model is verified by comparing the strain distributions obtained from the tensile test and FE analysis. The mechanical behavior of a socket is investigated with respect to the variation of the frictional coefficient. The result shows that the friction between surfaces significantly diminishes the stress concentration of a socket and a casting alloy, and the normal stress from the design equation represents the averaged value of the upper and lower quartiles in the distribution of contact stresses between a socket and a casting alloy.

• International Journal of Aeronautical and Space Sciences
• /
• v.17 no.3
• /
• pp.285-295
• /
• 2016

A contact strip shape of a high speed train pantograph system was optimized with CFD to increase the aerodynamic performance and stability of contact force, and the results were validated by a wind tunnel test. For design of the optimal contact strip shape, a Kriging model and genetic algorithm were used to ensure the global search of the optimal point and reduce the computational cost. To enhance the performance and robustness of the contact strip for high speed pantograph, the drag coefficient and the fluctuation of the lift coefficient along the angle of attack were selected as design objectives. Aerodynamic forces were measured by a load cell and HWA (Hot Wire Anemometer) was used to measure the Strouhal number of wake flow. PIV (Particle Image Velocimetry) was adopted to visualize the flow fields. The optimized contact strip shape was shown a lower drag with smaller fluctuation of vertical lift force than the general shaped contact strip. And the acoustic noise source strength of the optimized contact strip was also reduced. Finally, the reduction amount of drag and noise was assessed when the optimized contact strip was applied to three dimensional pantograph system.

• Composites Research
• /
• v.13 no.6
• /
• pp.39-46
• /
• 2000

Electrical discharge machining (EDM) cuts metal by discharging electric current across a thin gap between tool and workpiece. Electrical discharge wire cutting, a special form of EDM, uses a continuously moving conductive wire as an electrode, and is widely used for the manufacture of punches, dies and stripper plates. In the wire cutting process, the moving wire is usually supported by cantilever arm and wire guides. As the wire traveling speed has been increased in recent years to improve productivity, the vibration of the cantilever arm occurs, which reduces the positional accuracy of the machine. Therefore, the design and manufacture of the cantilever arm with high dynamic characteristics have become important as the machining speed increases. In this paper, the cantilever arm for guiding the moving wire was designed and manufactured using carbon fiber epoxy composite in order to improve the static and dynamic characteristics. Specimens for the composite cantilever arm were manufactured and tested to investigate the effect of the number of reinforcing plies and length fitted to steel flange on the load capacity. Also, the finite element analysis using layer and contact elements was performed to compare the calculated results with the experimental ones. From the results, the prototype of the composite cantilever arm for the electrical discharge wire cutting machine was manufactured and the static and dynamic characteristics were compared with those of the conventional steel cantilever arm.

• Proceedings of the KIEE Conference
• /
• 2005.05b
• /
• pp.71-74
• /
• 2005

At the neutral sections, There are neutral sections inserted in overhead contact line between the substations to divide different phase current sections of AC electrified lines. except convention line, a large stress occurs in the contact wire near the fittings under passing pantographs. So, in order to raise the train speed over 150km/h, a new type section has been adopted.