The effects of graphite particle size and processing on the performance of silver-graphite contacts

Wingert, P.C.; Allen, S.; Bevington, R.

doi:10.1109/33.142888

Cited by 15 publications

(6 citation statements)

References 6 publications

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“…The greater weight loss of the material with the finer graphite particles is consistent with past work (9). The more continuous area of silver in a given cross-section of the bulk contact would be expected to provide a greater probability that a mass of silver on the surface would be able to remain attached to the silver matrix.…”

Section: Discussionsupporting

confidence: 70%

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The effects of interrupting elevated currents on the erosion and structure of silver-graphite

Wingert

Electrical Contacts - 1996. Proceedings of the Forty-Second IEEE Holm Conference on Electrical Contacts. Joint With the 18th In

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The surfaces of silver-5% graphite contacts are greatly disrupted when they are subjected to the interruption of arcs of over 1000 amperes. This paper describes the disruption structures observed and proposes mechanisms for their formation. Large masses of silver and layers rich in graphite develop on the contact surfaces. It is suggested that poor wetting of the graphite by molten silver is a major cause of this phase separation. Even if welds form between silver masses on the surfaces of opposing contacts the total weld strength is low due to the lack of metallic continuity between the silver masses and the silver in the bulk contact. It is shown that silver masses of up to .040 grams can be ejected from the arc region to distances of up to 5 mm. The loss of silver in large masses makes the weight loss in consecutive operations erratic. The probability of arcs restriking increases after the initial interruption operations. The greater probability of restriking is thought to be a result of greater carbon concentration on the contact surfaces andlor the mating through the large silver masses on the surface which can break up into the intercontact gap during interruption. Test results for pure silver and pure graphite are presented for comparison with the results for the composite materials.

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Section: Discussionsupporting

confidence: 70%

“…The surface structures of the carbon layers showed signs that perhaps both of these mechanisms were active. The build-up of carbon surface layers on tested silver-graphite contacts has been noted in previous work after testing at lower currents (9).…”

Section: Discussionmentioning

confidence: 81%

The effects of interrupting elevated currents on the erosion and structure of silver-graphite

Wingert

Electrical Contacts - 1996. Proceedings of the Forty-Second IEEE Holm Conference on Electrical Contacts. Joint With the 18th In

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“…The contact anti-welding was performed on a model switch with an induced contact bounce as described [2,8]. The stationary contacts were from Table I, and the moving contacts were always fine silver to induce sufficient welding for comparison.…”

Section: E Weld Testmentioning

confidence: 99%

“…Early work by Lambert et al [1] showed that various Ag/C manufacturing methods can result in the graphite orientation being pressed random, extruded perpendicular or extruded parallel, and have with very different electrical performances. Later, Wingert [2,3] showed that coarse graphite is better for erosion but worse in antiwelding; that sintered densities are important factors; and presented a model to explain the decomposition of C and erosion process. Behrens [4] found graphite fibers can improvement on erosion at the cost of worse anti-welding.…”

Section: Introductionmentioning

confidence: 98%

Electrical and mechanical lives of Ag/C and Ag/WC/C contacts

Leung¹,

Harman²,

Doublet³

et al. 2012

26th International Conference on Electrical Contacts (ICEC 2012)

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Several Ag/C and Ag/WC/C contact materials used as stationary contacts in MCCB (molded case circuit breakers) are compared for electrical and mechanical properties. The mechanical lives of the MCCB can be limited by the stationary contact chipping due to the impact by the much harder moving contacts of Ag/W and Ag/WC. Transverse Rupture Strengths are therefore measured by a 3 point bending test, and impact lives on a model switch designed to evaluate material cracking and chipping. The test results are discussed to illustrate the optimization of metallurgical and electrical properties.

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“…So far, the study of the conductive properties of the Ag-C contacts has been focused on the analysis of their dependence on the size and shape of graphite particles [5][6][7][8] and on the microstructure, which is inextricably linked with the method of the composite's manufacture [9,10]. Moreover, research on the application of different allotropes of carbon to Ag-C composites has also been conducted [11,12].…”

Section: Introductionmentioning

confidence: 99%

The Influence of the Microstructure on the Switching Properties of Ag C, Ag-WC-C and Ag-W-C Contact Materials

Wójcik-Grzybek¹,

Frydman²,

Borkowski³

2013

Archives of Metallurgy and Materials

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The correlation between the microstructure of Ag-C, Ag-WC-C and AgWC composites and their switching properties was investigated. Two methods were used to manufacture the starting powder mixtures, namely classical milling and mechanical alloying . The arc erosion, contact resistance and welding forces of the contact materials obtained by different methods were measured using model devices. This paper presents the results achieved for the tested materials. It was found that weight loss was lower for the contacts produced by high energy milling.Keywords: electrical contacts, microstructure, switching properties, mechanical alloying W pracy badano wpływ mikrostruktury kompozytów Ag-C oraz Ag-WC-C i Ag-W-C na ich właściwości łączeniowe. Do wytworzenia kompozytów stosowano dwa sposoby przygotowania mieszanin wyjściowych: klasyczne mieszanie proszków oraz mechaniczną syntezę (MA -mechanical alloying). Porównano odporność kompozytowych materiałów stykowych wykonanych różnymi technologiami na erozję łukową, rezystancje zestykową i odporność na sczepianie. Badania właściwości łączeniowych prowadzono w układach modelowych. Stwierdzono, że zastosowanie procesu MA do przygotowania mieszanin wyjściowych powoduje wzrost odporności na erozję badanych materiałów.

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The effects of graphite particle size and processing on the performance of silver-graphite contacts

Cited by 15 publications

References 6 publications

The effects of interrupting elevated currents on the erosion and structure of silver-graphite

The effects of interrupting elevated currents on the erosion and structure of silver-graphite

Electrical and mechanical lives of Ag/C and Ag/WC/C contacts

The Influence of the Microstructure on the Switching Properties of Ag C, Ag-WC-C and Ag-W-C Contact Materials

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