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
• • 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
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H11/00—Apparatus or processes specially adapted for the manufacture of electric switches
  • H01H11/04—Apparatus or processes specially adapted for the manufacture of electric switches of switch contacts

Definitions

• the invention relates to a material for electrical contacts with the composition specified in the preamble of claim 1.
• a material is described in US Pat. No. 4,011,426.
• the materials described in this publication contain a metal powder, for example a nickel powder, furthermore an inorganic, electrically non-conductive powder, for example quartz powder, aluminum oxide powder or dolomite powder, and furthermore a plastic which, under the action of an arc, releases gases which are able to extinguish the arc, in particular a plastic that releases electronegative gases under the influence of an arc, e.g. Polytetrafluoroethylene.
• a binder namely thermosetting plastics are mentioned as binders, e.g.
• Phenolic resin, urea resin, melamine resin, in particular a multi-component epoxy resin When epoxy resin is used, the known materials are produced in such a way that the powdery constituents are stirred into a liquid to pasty resin preparation which, in addition to the epoxy resin base substance, also contains solvents and hardening agents which cause the curing (crosslinking) of the synthetic resin.
• the invention has for its object to provide a material of the type mentioned, which is characterized by good arc quenching ability and low burn-up with sufficient electrical conductivity. This object is achieved by materials with the composition specified in claim 1.
• Advantageous developments of the invention are the subject of the dependent claims.
• the material according to the invention is characterized by the selection of a special duromer, which allows a given electrical conductivity to be achieved with a lower proportion of the metal powder in the material than before.
• the proportion of the metal powder in the duromer should be between 5 and 20% by volume, preferably between 8 and 12% by volume.
• thermosets which are produced from molding compositions which can be cured without the occurrence of a liquid phase, in particular by heating under pressure are curable.
• the molding compositions usually contain fillers, e.g. Rock flour, wood flour.
• Single-component foams are suitable for the invention.
• Examples are: Type 802 according to DIN 16911, Type 3515 from Bakelite GmbH in D-5680 Iserlohn (an unsaturated polyester resin with spherical, inorganic filler), type 870 according to the withdrawn standard DIN 16912, type 152 according to DIN 7708. These are thermosetting molding compounds.
• molding compositions which can be used in other ways, e.g. allow to harden by radiation, provided that no liquid phase occurs during hardening.
• metal powder those can be used which have sufficient electrical conductivity, in particular special silver powder, copper powder, silver-plated copper powder. Nickel powder can also be used, but has the disadvantage of having poorer electrical conductivity.
• the contact material according to the invention contains no further organic constituents (such as polytetrafluoroethylene) for the elimination of electronegative gases under the action of an arc.
• the arc extinguishing ability is based solely on the decomposition products of the duromer under the influence of an arc; Arc quenching is primarily caused by the hydrogen generated during the decomposition of the duromer, but other gaseous decomposition products, namely carbon monoxide, also contribute to the arc quenching capacity.
• the arc quenching capacity of these decomposition products is not based on their electronegativity, but rather on the fact that they blow the arc column in the axial direction and effectively cools through their high thermal conductivity.
• the electrical conductivity can be increased without increasing the volume fraction of the metal powder in the contact material by replacing part of the duromer with an inorganic, electrically non-conductive powder, the particles of which have the largest possible volume / Have surface ratio.
• an inorganic, electrically non-conductive powder reduces the volume in which metal powder is located, thereby favoring the formation of current paths.
• the effectiveness of this additional inorganic filler depends on the shape and size of its particles.
• the most suitable is a filler whose particles have a spherical shape and a size of not more than 300 ⁇ m, preferably not more than 100 ⁇ m; at the same time, the particle size of the metal powder should be smaller by a factor of 10 to 20 than the size of the particles of the other inorganic filler, because with such a choice of the particle sizes, the metal powder particles can form chains most easily around the particles of the further filler.
• this further filler in the contact material should not exceed 40% by volume, preferably between 25 and 35% by volume. At higher contents, the arc extinguishing capacity is reduced too much and the burn-up is increased too much.
• the inorganic, non-electrically conductive filler are, for example minerals and quartz flour, preferably a 'glass powder is used.
• Claim 12 specifies a new method for producing the material according to the invention.
• a metal powder and, if appropriate, the optionally provided inorganic, electrically non-conductive, powdery filler, in particular with the stated particle sizes, are used and these are best mixed dry with a thermosetting molding compound which has been pulverized for this purpose and which under Bypassing a liquid phase is thermosetting.
• the best way to pulverize is to grind a granulate from the thermoset molding compound. It is state of the art that such granules can be ground at low temperatures.
• a powder is preferably produced by grinding the granules, the particles of which are smaller than 300 ⁇ m, more preferably smaller than 100 ⁇ m.
• An unsaturated polyester resin, type 804 according to DIN 16911 is used as the molding compound.
• This molding compound is ground to a powder at room temperature and sieved with a 200 ⁇ m mesh size. 88% by volume of the pulverized molding compound with a particle size of less than 200 ⁇ m are dry mixed with 12% by volume of a flaky silver powder with an average particle size of 9 ⁇ m. From this mixture, tablet-shaped moldings are cold-pressed using a pressure of 1.2 10 8 to 1.5 10 8 N / m 2 and then at a temperature of 165 ° C. under a pressure of 1.8 10 8 to 2.2 - 10 8 N / m 2 hardened.
• An unsaturated polyester resin molding compound type 3515 from Bakelite GmbH in D-5860 Iseriohn is used as the molding compound.
• This molding compound is ground to a powder at room temperature and sieved with a mesh size of 100 ⁇ m. 88% by volume of the pulverized molding compound with a particle size of less than 100 ⁇ m are dry mixed with 12% by volume of a flaky silver powder with an average particle size of 9 ⁇ m, using a pressure of 1.2-10 8 to 1 , 5 - 10 8 N / m 2 cold pressed into tablets and then cured at a temperature of 165 ° C under a pressure of 1.8-10 8 to 2.2 108 N / m 2 .
• the material has a higher conductivity, but a lower arc extinguishing capacity than the material described in the first example.
• An epoxy resin molding compound type 870 according to the withdrawn standard DIN 16912 is used as the molding compound.
• This molding compound is ground to a powder at room temperature and sieved with a mesh size of 100 ⁇ m. 88% by volume of the pulverized molding material with a particle size of less than 100 ⁇ m are dry mixed with 12% by volume of a flaky silver powder with an average particle size of 9 ⁇ m, using a pressure of 1.2 10 a to 1.5 -10 8 N / m 2 cold pressed into tablets and then cured at a temperature of 165 ° C under a pressure of 1.8 - 10 a to 2.2 10 8 N / m 2 .
• the material has a higher conductivity and a higher arc extinguishing capacity than the material described in the first example.
• a melamine resin molding compound, type 152 according to DIN 7708 is used as the molding compound.
• This molding compound is ground to a powder at room temperature and sieved with a mesh size of 100 ⁇ m.
• 88 vol .-% of the pulverized molding material with particle sizes of less than 100 microns are dry mixed with 12 vol .-% of a flaky silver powder with an average particle size of 9 microns, using a pressure of 1.2-10 8 to 1.5 - 10 8 N / m 2 cold pressed into tablets and then at a temperature between 155 and 160 ° C under a pressure of 1.8 - 10 a to 22. 10 8 N / m 2 hardened.
• the material has a lower electrical conductivity, but a significantly higher arc extinguishing capacity than the material described in the first example.
• Example 4 is modified such that the contact material contains 30% by volume of glass balls, 58% by volume of the molding composition and 12% by volume of silver powder. Glass balls with a diameter ⁇ ⁇ 0.1 mm are used.
• the material has the highest electrical conductivity of all five examples and a similarly good arc extinguishing capacity as the material from the first example.
• thermosetting molding composition in Examples 1 to 4, too, a corresponding proportion of the thermosetting molding composition can be replaced by glass balls to increase the electrical conductivity.
• An increase in electrical conductivity by increasing the metal part of the material would have the disadvantage that, unlike the addition of an inorganic, non-conductive powder, the arc extinguishing capacity would be significantly reduced (a higher metal content leads to increased, undesired metal evaporation under the influence of the arc).
• the low erosion of contact pieces produced according to the invention is related to the fact that, on the one hand, the arc extinguishing capacity of the thermosets used is favorable and, on the other hand, under the influence of arcs on the contact surface there is no - molten phase, which experience has shown to be associated with greater erosion and, moreover, that Contact resistance increased by interrupting current paths.
• the proportion of the metal powder is so low that even when the inorganic, electrically non-conductive powder is added as a further filler in the amounts specified, the contact pieces produced therewith still have sufficient strength.

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• Compositions Of Macromolecular Compounds (AREA)
• Arc-Extinguishing Devices That Are Switches (AREA)
• Contacts (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=6266999

Family Applications (1)

Country Status (5)

Cited By (2)

Families Citing this family (5)

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• 1985
  • 1985-04-01 DE DE19853511879 patent/DE3511879A1/de not_active Ceased
• 1986
  • 1986-03-08 EP EP86103152A patent/EP0197332A3/fr not_active Withdrawn
  • 1986-03-26 BR BR8601544A patent/BR8601544A/pt unknown
  • 1986-03-28 JP JP61070668A patent/JPS61237310A/ja active Pending
• 1988
  • 1988-02-08 US US07/153,510 patent/US4778958A/en not_active Expired - Fee Related

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