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Electrical Contacts (HOLM), 2010 Proceedings of the 56th IEEE Holm Conference on

Date 4-7 Oct. 2010

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Displaying Results 1 - 25 of 93
  • HOLM 2010 [Title page]

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  • HOLM 2010 [Copyright notice]

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  • HOLM 2010 Sponsors

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  • HOLM 2010 Steering Committee

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  • HOLM 2010 Officers and Committee

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  • HOLM 2010 Table of contents

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  • HOLM 2010 Foreword

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  • HOLM 2010 Ragnar HOLM Scientific Achievement Award

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  • HOLM 2010 Morton Antler Lecture

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  • HOLM 2010 Erle Shobert Prize Paper

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  • HOLM 2010 Armington Recognition Award

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  • HOLM 2010 author index

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  • Interpretation of Low DC Current Measurements of a Transformer's Winding Resistance and the Effect of the Tapchanger's Contacts

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    Low current (<;10A) dc measurements of the transformer windings show a uniform decrease in the resistance as the tapchanger selector switch is advanced from the first tap to the last tap. When the resistance data for a newly manufactured transformer is plotted vs. the odd and even tap positions on its primary windings, the data lies with some small, but acceptable variation, on the same straight line with a slope of -3.9 for each of the three phases. After 20 months in operation there is a considerable change in the measured resistance data. The data for the odd and even tap positions each still lie with more variation on a line with the same slope (-3.9), but they lie on quite different lines. In Phase-1 the difference between the data for the odd and even tap positions is about 14.2mΩ. The other two phases also show a difference, but are somewhat less than that on Phase-1. The analysis of this data shows that these differences do not imply that there is an internal problem with the transformer windings or with the internal bolted connections to those windings. Tarnish film formation on the Cu and W-Cu contacts in a transformer oil environment is discussed. These resistive films grow thicker with time and their growth on the tapchanger's selector switch and its diverter switch contacts adequately account for the difference seen in the resistance measurement between the new transformer and after it had been in operation for 20 months. A discussion of the rupture of these resistive films by the combination of high contact forces and the transformer's normal load current is also presented. View full abstract»

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  • Contribution of Nanotechnologies on the Study of the Physical Phenomena of the Arc Birth

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    The interaction between electrical arc and cathodic surface causes circuit breakers failures which is a crucial problem in their conception. The properties of the electrical arc are governed by the emissive sites which are directly linked to physical parameters of the electrodes like their spacing, their composition, geometry and surface state.The literature provides lots of theoretical results on the formation of cathode spots and their impact on the contacts erosion. Very few experimental studies have been led on the subject at micro and submicronic scale. We propose here to evaluate the arc cathode interaction at submicronic scale by using methods of fabrication offered by nanotechnology such than electron beam lithography (EBL). In order to investigate the influence of microprotrusions on the arc birth in the electrical contact phenomena, tip matrix designs are produced on cathodes with a controlled roughness (under 40 nm). These microprotrusions are created by carbon adsorption on a copper electrode and are subjected to an arc impulse. After discharge, the eroded surfaces are studied by scanning electron microscope (SEM) and optical profilometer. These observations contribute to study the erosion mechanism and to develop a theoretical ablation model of the tip. A comparison between the experimental observation of the cathodic erosion and the numerical results is proposed. View full abstract»

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  • Voltage Fluctuation of Short-Time Arc at Slowly Separating Silver-Based Contacts

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    Arc discharge at breaking electrical contact is considered as a main source of an undesired electromagnetic (EM) noise. Short-duration time arc before an ignition of the continuous metallic arc discharge arises and causes high frequency EM noise. To clarify the characteristics and the mechanism of the generation of EM noise, the fluctuation of voltage and duration of short-time arc at slowly separating silver-based contacts are investigated experimentally in this paper. The opening velocity of the moving electrode was 60 μm/s and it was determined so that it satisfied quasi-thermal equilibrium condition. Ag and Ag88.3wt% ,SnO(211.7wt%) were chosen as contact test material. Breaking waveforms and aspects are measured. The voltage fluctuation for the Ag material case is larger than that for the Ag88.3wt% SnO(211.7wt%). For the Ag material case, some short-duration time arcs before the ignition of the continuous metallic arc discharge are observed. The arc duration of the continuous metallic arc at the first operation is relatively short. The measured aspects by highspeed camera indicate that the locations of the short-time arc are changed by each short-time arc. As operation numbers increase, arc duration becomes longer rapidly. The measured aspects by the high-speed camera indicated that the locations of the short-time arc are changed by each short-time arc and melting region on the contact surface due to the short-time arcs is enlarged dramatically by the short-time arc. These results are basic and useful finding and consideration to clarify not only the correspondence to noise generation of the contact-breaking phenomena but the material dependency for EMC problems. View full abstract»

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  • Cathode Root Motion Studies of High Current Arcs Using an Optical Fiber Array Based Imaging System

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    An integrated portable measurement system is presented for the study of high speed and high temperature unsteady plasma flows such as those found in the vicinity of high current switching arcs. The system permits direct and nonintrusive measurement of arc light emission images with a capture rate of 1 million images per second (1MHz), and 8 bit intensity resolution. Novel software techniques are reported to visualise the arc motion and to measure arc trajectories. Results are presented on high current (2kA) discharge events where the electrode and arc runner surfaces are investigated using optical surface scanning methods; such that the position of the arc roots on the runner can be correlated to the measured trajectories. The results show evidence of the cathode arc root stepping along the arc runners. View full abstract»

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  • A Multi-Physics Finite Element Analysis of Round Pin High Power Connectors

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    In the past decade, the general public's means of transportation has begun to undergo a radical transformation, moving away from only using gasoline and moving toward using a combination of gasoline and electricity. One parameter that shouldn't stand in the way is the overall reliability of the electric vehicle, which is dependent upon the electric connections between the power source and the motor. Using a multi-physics finite element software package and multiscale predictions of electrical and thermal contact resistance, a model was constructed to predict the behavior of a round pin, high power connector under normal vehicle operating conditions. To test the validity of the model, an experiment was devised to measure connector resistance and temperature. The theoretical and experimental results showed the same trends. The possible influence of fretting was also considered by artificially increasing the contact resistance. The model shows that for increasing current and increasing electrical contact resistance, that current becomes more concentrated along the path it travels through the connector. This constriction of current could lead to much higher surface temperatures than the model currently predicts, resulting in thermally induced softening or distortion in the connector. View full abstract»

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  • Computational Modeling of Electrical Contact Crimping and Mechanical Strength Analysis

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    Several thousands electrical connections are necessary in airplanes. Electrical cables are joined to contacts using manual crimping devices in industrial plants. When mechanical defects appear, the replacement of the defective connections has to be made directly on the airplane. This operation is difficult and time-consuming due to reduced accessibility, making it very costly. The aim of this paper is to simulate the crimping operation and then evaluate the mechanical strength of the obtained connection in order to identify, understand and eliminate defects due to unsatisfactory crimping operations. Material behavior data is accessed through mechanical testing performed on cables and contact; accurate material data is mandatory to improve the accuracy of the simulation results. The Forge® software is used to perform the numerical simulation to predict the stress and strain distribution as well as the crimping force during crimping operations. Resulting mechanical strength of the joint is also analysed using numerical simulation. Experimental and numerical results are then compared. View full abstract»

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  • Modeling and Analysis of a Blade/Receptacle Pair for the Prediction of Thermal Cycling and Temperature Dependent Vibration Driven Fretting Corrosion

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    Two of the major drivers for fretting corrosion are vibration and thermal cycling, with most previous studies focusing on experimental evaluation. It would be useful to develop and test a strategy for using computer modeling techniques to simulate the effects of vibration and thermal cycling induced fretting corrosion. Toward this end, finite element models are developed for a single blade/receptacle pair. Both thermal cycling induced and vibration induced fretting effects are considered. Example studies were performed and the results presented and discussed in detail. View full abstract»

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  • Comparison of Hard Au versus Hard Au Flashed PdNi as a Contact Finish

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    This work addresses the comparison of hard Au versus hard Au flashed PdNi contact finishes. Extensive qualification and re-qualification data are available, but this testing varies greatly and by definition is designed to 'pass' or fail' a connector design. Since this type of testing does not specifically compare variations in finish parameters, the ability to directly compare such data sets relative to finish performance is limited. In addition, PdNi high speed plating chemistries have evolved since the 1980s when they were first developed and qualified in response to increases in gold metal prices. Therefore, the testing was done to provide product level data comparing the two gold based finishes. To specifically compare finish performance, as opposed to connector performance; using current industry accepted testing conditions and finish variations. To better understand the contact performance implications of interchanging these two gold based finished. View full abstract»

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  • Time Dependence Investigation of the Electrical Resistance of Au / Au Thin Film Micro Contacts

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    As MEMS microswitches realization time is too long for experiments aimed at the evaluation of new contact materials, an innovative test method is designed for studying electrical resistance of metallic micro contacts by reproducing microswitches geometry. The test structures, constituted by micro bars that are flat on one side and provided with tens of aligned spherical micro bumps on the other one, are put in contact at low loads in the 100 - 1000 μN range using a nanoindenter, thus enabling direct electrical contact resistance (ECR) measurements. This configuration is used for the study of gold/gold thin film contacts and allows the comparison of first contact closure resistance for different parameters sets including statistical results with the same sample. Results present resistance variations in the 0.2 - 2 Ω range primarily governed by time. Adhesion is also considered through pull-off forces. It is increased by load and values of the order of several hundreds of μN are needed to separate the contact surfaces. Finally, effects of successive contact openings and closings are investigated for both ECR and pull-off forces. View full abstract»

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  • Analysis of Contact Resistance Behavior for Electric Contacts with Plating Layer

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    It is very important to predict the force-contact resistance relation for the virtual connector designing. In this study, the prediction of electrical contact resistance in various cases was examined. The specimens consisted of a copper alloy with tin or silver plating. To predict the contact resistance at each contact force, the relationship between contact resistance and contact force were separated into two parts as the force-contact area relationship and the contact area-resistance relationship. The force-contact area relationship was predicted by using Finite Elemental Modeling (FEM) contact analysis. The contact area-resistance relationship was analyzed by the theory of constriction resistance with plating layers. To combine these relations, the prediction of force-resistance relation is obtained. As the results, the experimental results of the silver plating sample, which has no oxide film, were in good agreement with the prediction results, and the experimental results of the tin plating sample, which has oxide film, were in agreement with the prediction results in high-load region of practical use of a terminal connector in which constriction resistance is dominant. Therefore, this technique is useful for the virtual connector designing. View full abstract»

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  • A Reliability Study of a New Nanocrystalline Nickel Alloy Barrier Layer for Electrical Contacts

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    This paper will present a reliability study of a new nanocrystalline nickel alloy undercoating barrier layer for electrical contacts. The new barrier layer material presented in the paper will be shown to be a viable alternative to the industry standard nickel sulfamate undercoating layer which has been the standard barrier layer in the electronics industry for electrical contacts for many decades. While nickel sulfamate has proven to be a reasonably effective barrier layer against both corrosion and diffusion, the authors of this paper will show that the new nanocrystalline nickel alloy will improve the corrosion resistance, minimize contact wear, and significantly reduce the formation of intermetallics resulting from interdiffusion at interfaces. Both materials will be put through a series of industry standard qualification tests such as mixed flowing gas, thermal shock, humidity cycling, and mechanical vibration to demonstrate the relative effectiveness of each material as an undercoating layer. These qualification tests will be performed in accordance with the Telcordia GR-1217CORE specification and EIA-364 test procedures. This reliability study will also include select test-to-failure sequences to quantify the full achievable performance of the nickel sulfamate relative to the new nanocrystalline nickel alloy as a barrier layer. View full abstract»

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  • Study of Arc Mobility and Reignition in a Static Gap Discharge with Magnetic Field

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    Arc mobility on contact surface is an important factor in contact erosion and circuit interruption. The two stages of arc mobility are the initial immobile arc followed by the running arc. Past work in the literature showed that immobile arc time is dependent of contact material, current and contact separation speed until a minimum separation speed is reached. When the arc is in the running stage, then contact material strongly affects arc velocity. In this paper, we re-examine the contact material effect with analysis of the arc spot eroded surface morphology to compare material modifications that can affect the arc mobility and reignition. A static gap discharge with various external magnetic field strength is used to affect the arc mobility. Several groups of contact materials are examined including Ag or Cu, Ag, and in composites with C, W, WC, CdO, SnO2. View full abstract»

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  • Rotational Drive of Arc Discharges by a Permanent Magnet Embedded in an Electrical Contact Mounted on a Relay

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    A column-shaped permanent magnet is embedded in the center of an electrical contact mounted on a relay. Another contact is conventional shape without the magnet. The magnet forms radial magnetic field to rotate arcs around the center axis of electrical contacts. A series of experiments is carried out in a 42V-10A resistive circuit. The contact material is Ag/SnO2 12wt%. The electrical contacts that are used in switches on the circuit current are called the make-only contacts, and switches off the circuit current are called the break-only contacts. Experimental results for make-only and break-only operations with the magnet are compared with those without the magnet. Following results are obtained. Rotational motion of the arcs occurring during the contact bounce for make-only operations is not observed. However break arcs for break-only operations are successfully rotated. Without the magnet the area of contact erosion on the contact surfaces is concentrated on the tip of contacts. With the magnet, on the other hand, the area of contact erosion is wide on contact surfaces by the rotational motion of break arcs. For break-only contacts the arc duration with the magnet is almost equal to that without the magnet. These results show that the effect of the magnet is confirmed to uniform the area of contact erosion for break-only contacts and the effect is not remarkable for make-only contacts. View full abstract»

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