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 arc extinguishing effect as well as its manufacturing process.
• Such a type of material finds its application mainly for the production of so-called "low voltage" contacts, that is to say the operating range of which is approximately between 10 and 1,000 volts and between 1 and 10,000 amperes.
• These contacts are generally used in the domestic, industrial and automotive fields, both in direct and alternating 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 metal parts but also, sometimes, to their welding, with the result that the device is blocked.
• 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 mergers and, because of their repetition, erosion and stud welding problems may occur in the short or medium term.
• auxiliary means to facilitate breaking of the arc or avoiding its reignition: electromagnetic or pneumatic blowing. It has also been proposed to replace the gas present in the space separating the two contacts with a very stable gas and therefore difficult to ionize, such as SF ⁇ .
• the object of the present invention is therefore to provide an electrical contact material with which pads can be produced, the operation of which is not impaired either in the short term or in the long term, by the energy of an electric arc.
• the contact material with extinguishing effect according to the invention comprises a matrix of conductive metal and an unstable fraction incorporated in this matrix with the property of decomposing at a temperature between the temperature of use of the contact. and the melting temperature of the metal by releasing a gas capable of destabilizing an electric arc.
• the invention also relates to a method for manufacturing the material defined above. It essentially consists of:
• the contact material according to the invention essentially consists of the following three components:
• metal hydrides TiH 2 Zrhb, MgH 2 ) , multi-metallic hydrides based on Ti, Zr, Hf, V, Nb, Mg, Ta, Cr, Mo, W, Fe, Co, Ni, La, Y.
• the residue is a metal, having partially or completely reacted with oxygen and nitrogen from l air, which can replace, totally or partially, the refractory fraction. It is therefore not an essential component of the contact material.
• the unstable fraction In the absence of a refractory fraction, the unstable fraction alone constitutes between 5 and 50% of the volume of the contact material. In the presence of a refractory fraction, the two fractions constitute between 5 and 50% of the volume of the material but, then, the proportion of unstable fraction is, at least, 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 produced using materials of the same or different compositions. In this case, it is possible that only one of the two contacts contains an unstable fraction.
• an electrical contact material is proposed which, under the effect of the heat produced by an electric arc, gives off a gas essentially formed of hydrogen in the case where, advantageously and as mentioned previously, the unstable fraction decomposed 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 dry, wet or by the technique known as "mechanical alloying" which causes the particles to bond together, then breaking them up into smaller particles.
• the mixture obtained is then compacted in the form of a pellet, either by cold pressing uniaxially or by hot pressing but at temperature. moderate and possibly under hydrogen pressure, that is to say under conditions of temperature and hydrogen pressure where the unstable fraction does not decompose, or even by impact (adiabatic compacting process).
• the resulting part is then sintered at moderate temperature and optionally under hydrogen pressure. It will be noted that this operation is optional in cases where the compaction has been carried out at moderate temperature or by impact.
• the part is shaped by cold recompaction.
• the method repeats the same first steps as the embodiment described above, the mixture being, this time, compacted by pressing in the form of a strip. Pressing is carried out according to the uniaxial mode cold or at moderate temperature, the resulting part then being sintered at moderate temperature, optionally under hydrogen pressure. As in the first embodiment, sintering is not necessary if the pressing has already been done at moderate temperature. The part is finally shaped by rolling.
• the same initial mixture is compacted in the form of a billet, by pressing either cold, in an isostatic mode, or at moderate temperature.
• the resulting part is then sintered also at moderate temperature and optionally under hydrogen pressure. Sintering is optional if pressing has already been done at moderate temperature.
• the part is finally shaped by moderate temperature extrusion in the form of strips or wires. These products are then transformed into a contact part by all the techniques known to those skilled in the art.
• the method repeats the same first steps as above. But then, the mixture is compacted cold, without sintering. The resulting part is finally shaped according to one of the techniques already mentioned.
• 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”.
• 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 preceding 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 has been done hot, or sintered under a hydrogen atmosphere, so as to hydrate the precursor of the unstable fraction.
• it is necessary that the compacted billet is sufficiently porous to allow access of hydrogen to the center of the room.
• the sintering was carried out at high temperature without hydrogen, the part is shaped by a high temperature extrusion before undergoing a hydriding treatment. In the case where the sintering was carried out under a hydrogen atmosphere, the part is shaped by an extrusion at moderate temperature.
• the same mixture as that described in the previous embodiment is compacted into a strip form by pressing cold uniaxially or hot.
• the part obtained is then either sintered at high temperature, optionally if the pressing has been done hot, or sintered under a hydrogen atmosphere, so as to hydrate the precursor of the unstable fraction.
• the part is shaped by rolling before undergoing, if necessary, a hydriding treatment.
• the various 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 and then, in the case of a billet, extruded under high temperature, typically at 900 ° C., or, if it is a question of '' 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.
• the various embodiments which have just been described do not constitute an exhaustive list. Other combinations of the different means proposed for each of the stages can possibly be used.
• a thin sub-layer generally of the same composition as the conductive metal used (generally silver or copper), intended to facilitate, thereafter, the operations of welding and brazing 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, or of one 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 capable of destabilizing an electric arc occurring between two contact pads, so as not to be altered in the long term by the effects of the heat given off.
• the process for manufacturing this material due to its great flexibility, makes it possible to produce contact parts in all the usual forms, using the same means of production as for 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)

Priority Applications (1)

Applications Claiming Priority (4)

Publications (2)

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Family Applications Before (1)

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• 2002
  • 2002-07-12 EP EP02405598A patent/EP1381065A1/de not_active Withdrawn
• 2003
  • 2003-05-30 AT AT03724760T patent/ATE480862T1/de active
  • 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 WO PCT/CH2003/000334 patent/WO2004008468A1/de not_active Ceased
  • 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 DE DE60334099T patent/DE60334099D1/de not_active Expired - Lifetime
  • 2003-05-30 US US10/521,036 patent/US20060169370A1/en not_active Abandoned

Non-Patent Citations (1)

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