The silver and tungsten contacts combine the high erosion resistance of the high melting tungsten with the high thermal and electrical conductivity of silver. These materials are known for their resistance and their high strength to welding or sticking. They are basically made by infiltration and the nominal silver content varies from 20-50%. By increasing the amount of tungsten, the actual hardness and welding are reduced.
You will be surprised to know that this composite group of alloys is especially preferred for use in air. Because of the excellent properties, silver and tungsten contacts have found a wide field of applications. They are used successfully with high tungsten content as burn-off contacts for large low-voltage circuit breakers and with lower contents as contacts carrying a steady line current for molded case circuit breakers and in various protective circuit breakers. Silver and tungsten contacts are also used in high current contactors where resistance to contact welding and arc erosion are required.
The silver and tungsten carbide composites exhibit initial resistance to the formation of surface films and possess good anti-weld and arc erosion resistance. These are specially used for devices requiring more consistent millivolt drop as compared to silver tungsten. Modison manufactures these composites by powder metallurgy. Pressed parts are sintered and infiltered by silver in a liquid phase
Modison is one such company that manufactures electrical contact materials and finished contacts for low, medium and high tension switchgear industry under one roof starting from Silver Refining to producing all the contact materials ( Ag Alloys, CuCr, CuCrZr, ETP, OFC, Cu-Ag 0.1%, CuNi2Si etc. ) by Powder Metallurgy or by melting & alloying is carried out in house. In addition having state-of-the-art Electron Beam Welding machines, VIM furnaces, CNC Machining Centers and Ag plating plants all under one roof, is an added competitive edge.
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