• Journal of Electrical Engineering and Technology
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• v.8 no.3
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• pp.595-602
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• 2013

An air circuit breaker (ACB) with novel double-breaker contact and permanent magnet actuator (PMA) is presented. Three-dimensional (3-D) finite element method (FEM) is employed to compute the electro-dynamic repulsion forces, including the Holm force and Lorentz force, which are acting on the static and movable contacts. The electro-dynamic repulsion forces of different contact pieces are computed, illustrating there is an optimal number of contact pieces for the ACB being studied. The electro-dynamic repulsion force of each contact, which varies from the outer position to the inner position, is also computed. Finally, the contacts of the double-breaker are manufactured according to the analyzed results to validate the simulations.

• Proceedings of the KSR Conference
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• 2009.05b
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• pp.201-206
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• 2009

In the testing stage of HEMU-400X(next Korean high speed train) developing project, maximum speed(400km/h) tests will be conducted. On present and near future conditions of the overhead contact lines, 400km/h is over the design speed criteria. The predictions of current collection performance including the percentage loss of contact(arcs level) parameter through dynamic interaction simulation of HEMU-400X maximum speed test run are described in this paper. Various simulations are conducted at the condition of two different contact wire tensions to draw the proper contact wire increasing values in the 400km/h test line under the available contact wire tension supporting condition of that line.

• Transactions of Materials Processing
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• v.12 no.1
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• pp.34-42
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• 2003

This paper presents a rigid-plastic finite element method to handle the frictional contact problem between two deformable bodies experiencing large deformation. The variational formulation combined with incremental quasi-static model is employed for treating the contact boundary condition. The frictional behavior of the model obeys Coulomb's law of friction. The proposed contact algorithms are classified into two categories, one for searching contacting nodes and the other for calculating contact forces at the contact surface. A slave node and master contact segment are defined using the geometric condition of finite elements on the contact interface. The penalty parameter is used to limit the penetration between contacting bodies, and the finite elements are coupled with contact boundary elements.us gates and cavity thicknesses. Through this study we have observed that the jetting is related to the die swell of material. This means that the jotting is strongly affected by the elastic flow property rather than the viscous flow property in viscoelastic characteristics of molten polymer. Different resins have different elastic properties, and elastic flow behavior depends on the shear rate of flow, i.e. injection speed. Large die swell would eliminate jetting however, the retardation of die swell would stimulate jetting. In the point of mole design, reducing the thickness ratio of cavity to gate can reduce or eliminate jetting regardless of amount of elasticity of polymer melt.

• Progress in Superconductivity and Cryogenics
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• v.7 no.2
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• pp.21-26
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• 2005

Breakdown characteristics and survival probability of turn-to-turn models were investigated under ac and impulse voltage at 77K. For experiments, two test electrode models were fabricated: One is point contact model and the other is surface contact model. Both are made of copper wrapped by O.025mm thick polyimide film(Kapton). The experimental results were analyzed statistically using Weibull distribution in order to examine the wrapping number effects on voltage-time characteristics under ac voltage as well as under impulse voltage in LN$_{2}$. Also survival analysis were performed according to the Kaplan-Meier method. The breakdown voltages of surface contact model are lower than that of point contact model, because the contact area of surface contact model is wider than that of point contact model. Besides, the shape parameter of point contact model is a little bit larger than that of surface contact model. The time to breakdown t$_{50}$ is decreased as the applied voltage is increased, and the lifetime indices slightly are increased as the number of layers is increased. According to the increasing applied voltage and decreasing wrapping number, the survival probability is increased.

• Tribology and Lubricants
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• v.11 no.1
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• pp.27-36
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• 1995

Maximum allowable PV values of oilless composite bearing materials (70% epoxy-resin/30% Graphite) were measured and compared at various types of test rigs that have different contact geometry and the operating conditions. Test results showed that material failure was mainly characterized by the sharp increase in both coefficient of friction and surface temperature, and different PV values were measured under different Contact geometry. The discrepancy in measurement of PV values was analyzed in the light of theoretical frictional heating analysis. Results show that surface temperature rise depends on its contact geometry, and PV values could be overestimated in the testing conditions of high sliding velocity. Test data of different contact geometry were normalized by using a normalized contact pressure and sliding velocity; it showed a good correlation. This work suggests that normalized PV values could be more effective in evaluating bearing materials than conventional PV values for a design parameter of journal bearings.

• Journal of KSNVE
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• v.9 no.5
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• pp.1050-1057
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• 1999

The existence of clearance at the link joint of a machine is inevitable for assembly and mobility. During the cyclic operation of a machine, rapid changes of the direction and magnitude of connection forces cause momentary loss of contact between the pin and the bushing at the link joint. Contact loss at the clearance joint gives rise to undesirable impact. The impulsive force affects on the performance of the machine, and leads to excessive vibration, noise and faster wear in the connecitons. In this paper, experiment and theoretical analysis were carried out for the variation of crank speed and clearance size. The link mechanism employed in this investigation was newly designed to check the effects of parameter changes on the occurrence of contact loss and on the magnitude of the impact force. The contact loss and impact position were calculated with various driving conditions.

• Bulletin of the Korean Chemical Society
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• v.30 no.4
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• pp.882-886
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• 2009

The electrode contact poling is one of the efficient tools to induce a stable polar order of nonlinear optical (NLO) chromophores in the solid film. Self-assembled NLO chromophores with high electro-optic (E-O) activities were utilized for quantitative determination of the chromophore order induced under contact poling by spectroscopic changes. We found that NLO chromophores rarely decompose under the high electric field during contact poling. The absorption spectra were de-convoluted into a sum of Gaussian components to separate energy transitions for a binary composite system which contains a secondary guest chromophore AJC146 in the self-assembled chromophore HDFD. Poling efficiency was significantly improved in the binary system compared to the individual components.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.804-807
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• 2005

In this paper, a double scotch yoke mechanism for moving simultaneously the fixed contact and moving contact of a gas circuit brake, is proposed and designed to improve the breaking characteristics of the circuit breaker. Firstly, the design parameters of the scotch yoke are kinematically determined from the desired design condition of the circuit breaker. Next, the stroke curve of the moving contact is designed by considering the design parameter and the specified opening characteristics of electric contacts. Based on the scotch yoke and stroke curve, the dynamics of the electric contacts is analyzed using ADAMS model of switch mechanism.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.5
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• pp.531-537
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• 2012

Fretting fatigue tests were conducted to investigate the effect of contact pressure on fretting fatigue behavior in aluminum alloy A7075-T6. Test results showed that when the contact pressure is so low that gross or partial slip occurs at the pad/specimen interface, fretting fatigue damage increases with the contact pressure. However, when the contact pressure is high enough to prevent slip at the interface, fretting fatigue damage decreases with the contact pressure. In order to understand how the contact pressure influence the fretting fatigue damage, finite element analyses were conducted and the analysis results were used to evaluate critical plane fretting fatigue damage parameters and their components. It is revealed that fretting fatigue damage estimated with the parameters exhibits the same variation as that in the tests. Moreover, the variation of fretting fatigue damage is closely related with that of the maximum normal stress on the critical plane rather than the strain amplitude on the critical plane.

• Proceedings of the KIEE Conference
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• 1994.11a
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• pp.261-263
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• 1994

This paper deals with the on off arc characteristics of electromagnetic relay contacts contaminated by NaCl and $H_2SO_4$. In this paper, I have studied the characteristics of on-off voltage waveform. the contact errosion, contact surface analysis by SEM and EDAX under changed R-L parameter of testing circuit. After considers these result, I have tried to promote the diagnosis method and developed the contacts. As a results, (1) The arc duration and the numbers of arc occurrence characteristics are depended on contamination degree. The contamination degree is high when the arc characteristics is high. (2) Under clean condition, arc occurrence voltage, surge peak voltage, arc duration and the rate of contact errosion is lower than wet condition. (3) Surge peak voltage and arc duration is depended on L parameter. When L is High, the arc characteristics is high.