Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H33/00—High-tension or heavy-current switches with arc-extinguishing or arc-preventing means
  • H01H33/70—Switches with separate means for directing, obtaining, or increasing flow of arc-extinguishing fluid
  • H01H33/76—Switches with separate means for directing, obtaining, or increasing flow of arc-extinguishing fluid wherein arc-extinguishing gas is evolved from stationary parts; Selection of material therefor
  • H01H33/765—Switches with separate means for directing, obtaining, or increasing flow of arc-extinguishing fluid wherein arc-extinguishing gas is evolved from stationary parts; Selection of material therefor the gas-evolving material being incorporated in the contact material

Definitions

• the present invention relates to the field of electrical contacts. It relates more particularly to a contact material with an arc extinction effect and to its manufacturing process.
• Such a type of material is mainly applicable for the production of what are called “low voltage” contacts, that is to say contacts whose operating range lies approximately between 10 and 1000 volts and between 1 and 10 000 amps.
• Such contacts are generally used in the domestic, industrial and automobile fields, both for DC and for AC applications, for switches, relays, contactors and circuit breakers.
• This column of ionized gas has a maximum length that depends on various parameters such as the nature and the pressure of the gas, the voltage across the terminals, the contact material, the geometry of the equipment, the impedance of the circuit, etc.
• the energy released by the electric arc is sufficient to melt the constituent material of the contact elements, which not only results in degradation of the metallic parts but also sometimes results in them being welded together, with the consequence of locking the equipment.
• the materials of electrical contacts must meet the following three requirements:
• one solution consists in using pseudo alloys comprising a silver or copper matrix and, inserted into this matrix, a fraction consisting of about 20% by volume of refractory (for example Ni, C, W, WC, CdO, SnO 2 ) particles having a size generally between 1 and 5 microns.
• refractory for example Ni, C, W, WC, CdO, SnO 2
• the material thus obtained is more resistant to the heat generated by the electric arc.
• this method does not make it possible to limit melting and, because of their repetition, problems of erosion and welding of the contact elements may occur in the short or medium term.
• the object of the present invention is therefore to provide an electrical contact material with which it is possible to produce contact elements whose operation is not impaired either in the short term or the long term by the energy of an electric arc.
• the contact material with an extinction effect comprises a matrix made of conductive metal and an unstable fraction incorporated into this matrix, the unstable fraction having the property of decomposing at a temperature between the operating temperature of the contact and the melting point of the metal, with the release of a gas capable of destabilizing an electric arc.
• the invention also relates to a process for manufacturing the material defined above. It essentially consists in:
• the contact material according to the invention essentially consists of the following three components:
• the refractory fraction is not an essential component of the contact material.
• the unstable fraction constitutes, by itself, between 5 and 50% of the volume of the contact material.
• the two fractions constitute between 5 and 50% of the volume of the material, but then the proportion of the unstable fraction is at least 2% by volume.
• the material according to the invention may advantageously include, in addition, small amounts of dopants designed to optimize the properties of the material.
• these dopants are Bi 2 O 3 , CuO or Re.
• Pairs of contact elements may be produced using materials of the same composition or of different compositions. In this case, it is possible for only one of the two contacts to contain an unstable fraction.
• the invention proposes an electrical contact material which, under the effect of the heat produced by an electric arc, releases a gas essentially formed from hydrogen when, advantageously and as mentioned above, the decomposed unstable fraction is a hydride. This gas cools and destabilizes the arc, which therefore is rapidly extinguished.
• the base constituents of the material are in the form of powders which are then dry-blended or wet-blended, or blended using the technique called “mechanical alloying”, which causes welding of the particles together, and then their fracture into smaller particles.
• the blend obtained is then compacted in the form of a pellet, either by uniaxial cold pressing, or by hot pressing, but at a moderate temperature and optionally under pressurized hydrogen, that is to say under hydrogen temperature and pressure conditions in which the unstable fraction does not decompose, or else by impact compaction (adiabatic compaction method).
• the resulting part is then sintered at a moderate temperature and optionally under pressurized hydrogen. It should be noted that this operation is optional when the compacting has been carried out at a moderate temperature or by impact compaction. Finally, the part is formed by cold recompaction.
• the process repeats the same first steps as the embodiment described above, but this time the blend is compacted by pressing it into a strip.
• the pressing is carried out uniaxially, cold or at moderate temperature, the resulting part then being sintered at moderate temperature, optionally under pressurized hydrogen.
• the sintering is not necessary if the pressing has already been carried out at moderate temperature.
• the part is finally formed by rolling.
• the same initial blend is compacted in the form of a billet, either by cold pressing, in isostatic mode, or by pressing at moderate temperature.
• the resulting part is then sintered, again at moderate temperature and optionally under pressurized hydrogen. The sintering is optional if the pressing has already been carried out at moderate temperature.
• the part is formed by extrusion at moderate temperature into strip or wire. This product is then converted into a contact part by any technique known to those skilled in the art.
• the process repeats the same first steps as above, but then the blend undergoes cold compaction without sintering.
• the resulting part is finally formed using one of the techniques already mentioned.
• the various constituents are again provided in powder form.
• the unstable fraction is not in its final form, but in the form of a precursor, that is to say the metal atoms of the unstable fraction are in the zero oxidation state.
• the powder is in the form of Ti instead of TiH 2 , Zr instead of ZrH 2 , or Mg instead of MgH 2 .
• the precursor may be free or alloyed with the matrix.
• the various powders are then blended, by dry blending, wet blending or by mechanical alloying. The blend is then compacted in the form of a pellet by cold uniaxial pressing, by hot pressing or by impact compaction.
• the part is then sintered at high temperature, without hydrogen, optionally if the pressing has been carried out hot or by impact compaction, before being subjected, in the hydrogen atmosphere, to a heat treatment for hydriding the precursor of the unstable fraction. Finally, the part is formed by cold recompaction.
• the sintering may be carried out directly in a hydrogen atmosphere, which then avoids the specific hydriding treatment.
• the same blend as that described in the above embodiment is compacted by cold isostatic pressing, or by hot uniaxial pressing.
• the part obtained is then either sintered at high temperature, optionally if the pressing has been carried out hot, or sintered in a hydrogen atmosphere, so as to hydride the precursor of the unstable fraction.
• the sintering has been carried out at high temperature without hydrogen, the part is formed by high-temperature extrusion before it undergoes a hydriding treatment.
• the sintering has been carried out in a hydrogen atmosphere, the part is formed by extrusion at moderate temperature.
• the same blend as that described in the previous embodiment is compacted in the form of a strip by cold uniaxial pressing or by hot pressing.
• the part obtained is then either sintered at high temperature, optionally if the pressing has been carried out hot, or sintered in a hydrogen atmosphere, so as to hydride the precursor of the unstable fraction.
• the part is formed by rolling before, if necessary, undergoing a hydriding treatment.
• the various constituents of the material are provided in the form of a bulk alloy containing the precursor of the unstable fraction.
• the alloy is then melted and cast in the form of a billet or ingot, and then, in the case of a billet, extruded at high temperature, typically at 900° C., or, if it is in the form of an ingot, converted into strip or wire by successive plastic deformation operations (rolling, wire-drawing, hammer swaging, etc.) interspersed by heat treatments, before undergoing the final hydriding.
• the parts undergo conventional final treatments, for example cutting, forming, polishing, expansion heat treatment.
• a thin sublayer generally of the same composition as the conductive metal used (generally silver or copper), intended to make it easier, subsequently, to carry out the welding and brazing operations that the part may undergo when it is being used.
• the conductive metal used generally silver or copper
• the unstable fraction may consist of a blend either of several of the elements proposed above for forming said fraction or of one of these elements, but with a different particle size.
• the unstable fraction may consist of a blend either of several of the elements proposed above for forming said fraction or of one of these elements, but with a different particle size.
• the invention proposes an electrical contact material capable of destabilizing an electric arc occurring between two contact elements, so as not to be impaired in the long term by the effects of the heat released.
• the process for manufacturing this material owing to its great flexibility, makes it possible to produce contact parts in any of the standard forms using the same means of production as used for the current materials.

Landscapes

• Contacts (AREA)
• Manufacture Of Switches (AREA)
• Powder Metallurgy (AREA)
• Manufacture Of Alloys Or Alloy Compounds (AREA)
• Coupling Device And Connection With Printed Circuit (AREA)

Applications Claiming Priority (3)

Publications (1)

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ID=29724605

Family Applications (1)

Country Status (8)

Cited By (1)

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Citations (11)

Family Cites Families (1)

• 2002
  • 2002-07-12 EP EP02405598A patent/EP1381065A1/de not_active Withdrawn
• 2003
  • 2003-05-30 ES ES03724760T patent/ES2350827T3/es not_active Expired - Lifetime
  • 2003-05-30 WO PCT/CH2003/000334 patent/WO2004008468A1/de active Search and Examination
  • 2003-05-30 US US10/521,036 patent/US20060169370A1/en not_active Abandoned
  • 2003-05-30 AT AT03724760T patent/ATE480862T1/de active
  • 2003-05-30 JP JP2004520256A patent/JP2005533175A/ja not_active Abandoned
  • 2003-05-30 AU AU2003229227A patent/AU2003229227A1/en not_active Abandoned
  • 2003-05-30 EP EP03724760A patent/EP1522083B1/de not_active Expired - Lifetime
  • 2003-05-30 DE DE60334099T patent/DE60334099D1/de not_active Expired - Lifetime

Patent Citations (11)

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