Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H1/00—Contacts
  • H01H1/02—Contacts characterised by the material thereof
  • H01H1/021—Composite material
  • H01H1/025—Composite material having copper as the basic material
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H1/00—Contacts
  • H01H1/64—Protective enclosures, baffle plates, or screens for contacts
  • H01H1/66—Contacts sealed in an evacuated or gas-filled envelope, e.g. magnetic dry-reed contacts

Definitions

• any gas which does not react in an undesirable manner with the contact material (as would be possible with nitrogen with the formation of nitride) and which does not release any harmful decomposition products under the action of the switching arc can be used as protective gas.
• argon is the only protective gas that can be used, because argon is cheap and consequent Due to its large atomic radius, it is easy to enclose, ie, with modest effort, it is possible to implement an argon-filled switching chamber from which the argon will not diffuse for years. Unfortunately, however, argon has a very low dielectric strength (see Manfred von Ardenne: Tables on Applied Physics, Volume 3, page 418; VEB Deutscher Verlag dermaschineen Berlin 1973).
• the low dielectric strength of the argon gives rise to concerns that the arc cannot be reliably re-ignited after a switch has been opened, and this concern has arisen in studies carried out by the inventors, inter alia, on contact pieces made of 88% by weight copper and 12% cadmium oxide, from 75% by weight copper and 25% by weight chromium.
• a contact material for encapsulated contact systems in low-voltage switching devices which contains 5 to 25% by weight, preferably 10% by weight, molybdenum and the balance copper. None is known about the type of protective gas used. According to the information in this published specification, a contact resistance was measured with contact pieces made of 10% molybdenum and 90% copper, which was comparable to the contact resistance of contact pieces made of silver with 12% by weight cadmium oxide. However, this material does not behave satisfactorily with regard to the resistance to erosion and the tendency to weld as well especially with regard to the reignition of the arc after opening the switch.
• the invention has for its object to find a contact material which is particularly suitable in switchgear, in particular in those for low-voltage energy technology, for use under argon as a protective gas.
• This object is achieved through the use of a contact material which, apart from any minor addition of one or more metals serving as a sintering aid or wetting aid, consists of 35 to 75% by volume of tungsten or molybdenum and 0 to 12% by volume of one or more elements consists of the group tellurium, antimony and bismuth as well as the rest of copper.
• the contact material used according to the invention contains a very high proportion of heavy metals (in the case of tungsten, the 35 to 75% by volume corresponds to a content of around 55 to 85% by weight. -%).
• the additional metals tellurium, antimony and bismuth - of which antimony is particularly suitable - represent at most a small proportion of the contact material; they are preferably used in a proportion of 1 to 6% by volume (corresponding to approximately 0.5 to 2.5% by weight) in the contact material, low contents being particularly preferred.
• Contact pieces can be produced from the contact material according to the invention by first producing a porous molded body from tungsten powder or from molybdenum powder by sintering, which is then infiltrated with copper, which contains the additional metals tellurium, antimony and / or bismuth, optionally as alloy metals, and preferably by excess soaking.
• the tungsten powder or the molybdenum powder can contain small amounts of an additional metal in a manner known per se which promotes the sintering process; Suitable sintering aids are, for example, nickel or cobalt, which may be added to the tungsten in a proportion of around 0.5% by weight.
• the contact material can contain small amounts (less than 1% by weight) of one or more Contain metals, which serve as a wetting aid and favor the infiltration of the copper or the copper alloy;
• Contain metals which serve as a wetting aid and favor the infiltration of the copper or the copper alloy
• cobalt and nickel are also suitable as wetting aids, which can optionally be added to the copper to be infiltrated.
• the tungsten or molybdenum powder with copper powder as well as with antimony, tellurium and / or bismuth powder, possibly also with an additional metal provided as a sintering aid or wetting aid, and produce a shaped body from the powder mixture by sintering in the liquid phase.
• an excess amount of the impregnating material (copper and the intended additional metal from the group of antimony, bismuth and tellurium) is preferably placed on the powder mixture given in a mold in order to impregnate the tungsten or molybdenum structure formed during sintering as completely as possible guarantee and at the same time to get a well solderable and weldable surface layer on one side.
• Contact pieces made of the material according to the invention not only have a low contact resistance and thus only a low contact heating, but also a long service life, sufficiently low erosion and sufficiently low tendency to weld, and in particular excellent suitability for arc quenching, especially under argon as a protective gas.
• tungsten powder with an average grain size between 1 and 10 ⁇ m (FSSS) and 0.5 part by weight of fine-grained nickel powder are mixed together, placed in a mold, compacted therein and then at a temperature of around 1100 ° C for a period of 30 min. sintered under cracked gas.
• a molded body is formed from a porous tungsten framework, which is then impregnated with an alloy of copper with 3% by weight of antimony. Soaking takes place at a temperature of approx. 1150 ° C in a vacuum.
• the contact piece blank After the impregnation process, the contact piece blank has a residual porosity of less than 2% and has the following composition by weight
• Arc duration r arc 10 ms) to values between 300 - 400 ⁇ rise.
• the corresponding values for contact pieces made of silver with 12% cadmium oxide when switching in air are 300 - 400 ⁇ or 500 - 700 ⁇ .
• the burnup for the contact pieces made of silver with 12% cadmium oxide in air is 20 mg / 1000 switching cycles, for the contact pieces made of the material according to the invention in the above composition in combination with argon as protective gas, 15 mg / 1000 switching cycles.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Composite Materials (AREA)
• Materials Engineering (AREA)
• Contacts (AREA)

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• 1984
  • 1984-08-18 DE DE19843430490 patent/DE3430490A1/de active Granted
• 1985
  • 1985-07-25 EP EP85109354A patent/EP0172442A3/fr not_active Withdrawn

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