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. She relates more particularly to a contact material with extinguishing effect arc and its manufacturing process.
• Such a type of material finds its application mainly for the realization of contacts called "low voltage", that is to say whose operating range is approximately between 10 and 1,000 volts and between 1 and 10,000 amps.
• These contacts are generally used in the domestic fields, industrial and automotive, both direct and alternative current, for switches, relays, contactors and circuit breakers.
• the energy released by the electric arc is sufficient to melt the material constituting the studs, which not only leads to the degradation of the parts metal, but also, sometimes, their welding, with the consequence blocking of the device.
• the electric arcs are very stable, especially when the voltage is significantly higher than 10 volts.
• a solution to cut the arch is to increase its length so that it becomes unstable and disappears by itself. For a voltage of 14 volts, a distance of the order of a millimeter is sufficient while for a tension of 42 volts, especially when an inductive load is present, this distance may be several centimeters. This seriously complicates the construction of the breaking devices and the duration of the arcs created reduced strongly their lifespan.
• one solution consists in using pseudo-alloys comprising a silver or copper matrix and, inserted into this matrix, a fraction consisting of approximately 20% by volume of refractory particles (for example, Ni , C, W, WC, CdO, SnO 2 ) of a size generally between 1 and 5 microns.
• refractory particles for example, Ni , C, W, WC, CdO, SnO 2
• This method does not limit the mergers and, because of their repetition, problems of erosion and welding of the studs can occur in the short or medium term.
• the present invention therefore aims to provide a contact material electric with which one can make studs whose operation is not altered neither in the short term nor in the long term, by the energy of an electric arc.
• the contact material with extinguishing effect comprises a conductive metal matrix and an unstable fraction incorporated into this matrix with the property of decomposing to a temperature between the temperature of use of the contact and the melting temperature of the metal, giving off a gas liable to destabilize an electric arc.
• the residue is a metal, having partially or fully reacted with oxygen and nitrogen from the air, which can substitute, totally or partially, for the refractory fraction. This is not therefore not an essential component of the contact material.
• the unstable fraction alone constitutes 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 unstable fraction is, at less, 2% by volume.
• the material according to the invention can advantageously comprise, in addition, small amounts of dopants intended to optimize the properties thereof.
• these dopants are Bi 2 O 3 , CuO, Re.
• Pairs of contact pads can be made using materials of the same or different compositions. In this case, it is only one of the two contacts may contain an unstable fraction.
• an electrical contact material which, under the effect of heat produced by an electric arc, gives off an essentially formed gas of hydrogen in the case where, advantageously and as mentioned previously, the unstable fraction broken down is a hydride. This gas cools and destabilizes the arc which then dies out quickly.
• the basic constituents of the material are in the form of powders which are then mixed by way dry, wet or by the technique known as "mechanical alloying" which causes the particles to weld together and then break into particles smaller.
• the mixture obtained is then compacted in the form of a pellet, either by pressing uniaxially cold, either by hot pressing but at temperature moderate and possibly under hydrogen pressure, that is to say in hydrogen temperature and pressure conditions where the unstable fraction does not does not decompose, or again by impact (adiabatic compaction process).
• the resulting part is then sintered at moderate temperature and possibly under hydrogen pressure. Note that this operation is optional in cases where compaction was carried out at moderate temperature or by impact.
• the part is shaped by cold recompaction.
• the method uses the same first steps than the embodiment described above, the mixture being, this time, compacted by pressing in the form of a band.
• the pressing is performed in cold or moderate temperature uniaxial mode, the part resulting being then sintered at moderate temperature, possibly under hydrogen pressure.
• sintering is not necessary if the pressing has already been done at moderate temperature.
• the the part is finally shaped by rolling.
• the same initial mixture is compacted in the form of a billet, either by cold pressing or in a mode isostatic, ie at moderate temperature.
• the resulting part is then sintered also at moderate temperature and possibly under pressure hydrogen. Sintering is optional if pressing has already been done at temperature moderate.
• the part is finally shaped by temperature extrusion moderate in the form of bands or threads.
• the various constituents are also supplied in powder.
• the unstable fraction is not in its final form, but in the form of a precursor, that is to say that the metal atoms of the unstable fraction have a zero degree of oxidation.
• 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 can be free or alloyed with the matrix.
• the different powders are then mixed dry, wet or by “mechanical alloying”. Then, the mixture is compacted into a pellet shape by cold pressing uniaxially, by hot pressing or by impact.
• the part is then sintered at high temperature, without hydrogen, optionally if the pressing has been done hot or by impact, before being subjected, in a hydrogen atmosphere, to a heat treatment for hydrating the precursor of the unstable fraction. .
• the part is shaped by cold recompaction.
• the sintering can be carried out directly in a hydrogen atmosphere, which then avoids the specific hydriding treatment.
• the same mixture as that described in the previous embodiment is compacted by cold isostatic pressing, or by uniaxial hot pressing.
• the part obtained is then either sintered at high temperature, optionally if the pressing was done hot, or sintered under a hydrogen atmosphere, so as to hydrate the precursor of the fraction unstable.
• it is necessary that the compacted billet is sufficiently porous to allow access of hydrogen to the center of the room.
• the sintering was done at high temperature without hydrogen, the part is shaped by high temperature extrusion before undergoing a hydriding treatment. In the event that the sintering was carried out under an atmosphere of hydrogen, the part is shaped by temperature extrusion moderate.
• the same mixture as that described in the previous embodiment is compacted into a strip shape by pressing uniaxially cold or hot.
• the part obtained is then either sintered at high temperature, optionally if the pressing was done hot, or sintered under a hydrogen atmosphere, so as to hydrate the precursor of the fraction unstable.
• the part is shaped by rolling before undergoing, if necessary, hydriding treatment.
• the different constituents of the material are supplied in the form of a solid alloy containing the precursor of the unstable fraction.
• the alloy is then melted and cast in the form of a billet or an ingot then, in the case of a billet, extruded under high temperature, typically at 900 ° C, or, if it is an ingot, transformed into a strip or wire by successive plastic deformation operations (rolling, drawing, hammering, ...) interspersed with heat treatments, before undergoing final hydriding.
• the parts undergo conventional final treatments, for example cutting, forming, polishing, thermal expansion treatment.
• a thin sub-layer generally of the same composition as the conductive metal used (generally silver or copper), intended to facilitate, thereafter, the welding and brazing operations that the part may undergo during its use.
• the unstable fraction can consist of a mixture, either of several of the elements proposed above to form said fraction, either of of these elements but under different particle sizes. In this way, it is possible to obtain varied decomposition kinetics so that the material obtained can operate under a wide range of conditions.
• the invention provides an electrical contact material likely to destabilize an electric arc occurring between two studs contact, so as not to be affected in the long term by the effects of heat released.
• the process for manufacturing this material due to its great flexibility, makes it possible to produce contact parts in all forms usual, using the same means of production as for materials current.

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)

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

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