US3596025A - Vacuum-type circuit interrupter with contacts containing a refractory metal - Google Patents

Vacuum-type circuit interrupter with contacts containing a refractory metal Download PDF

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Publication number
US3596025A
US3596025A US763116A US3596025DA US3596025A US 3596025 A US3596025 A US 3596025A US 763116 A US763116 A US 763116A US 3596025D A US3596025D A US 3596025DA US 3596025 A US3596025 A US 3596025A
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United States
Prior art keywords
bismuth
vacuum
contact
contacts
refractory metal
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US763116A
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English (en)
Inventor
Joseph L Talento
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
General Electric Co
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General Electric Co
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Filing date
Publication date
Application filed by General Electric Co filed Critical General Electric Co
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Publication of US3596025A publication Critical patent/US3596025A/en
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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
    • H01H1/0203—Contacts characterised by the material thereof specially adapted for vacuum switches

Definitions

  • This invention relates to contact structure for a vacuumtype circuit interrupter and, more particularly, relates to contact structure of this type which is mechanically strong and has a high resistance to arc erosion and to contact welding.
  • a type of contact material that has a high resistance to arc erosion is one which comprises a refractory metal matrix infiltrated with a high conductivity metal.
  • the refractory metal of the matrix is typically tungsten or molybdenum or a comnound thereof and he high conductivity metal is typically copper or silver. If the contacts of a vacuum-type circuit interrupter are made of such a material, they have a tendency to weld together following a closing operation, particularly a closing operation that takes place under high current arcing conditions. One reason for this is that the surfaces of the contacts of a vacuum interrupter are kept exceptionally clean,
  • An object of my invention is to greatly improve the weld resistance of refractory metal matrix contacts in :a vacuum interrupter and to do this without significantly impairing the mechanical strength of the contacts and the brazability of the contacts to appropriate supports.
  • I make the contacts of the vacuum interrupter of a refractory metal matrix and infiltrate the matrix with an alloy of copper and bismuth.
  • the percentage of bismuth in the alloy is limited to less than 2 percent by weight of the alloy and is preferably less than 1 percent.
  • a vacuum-type circuit interrupter comprising a sealed envelope 11 evacuated to a pressure of l torr or lower.
  • the envelope 1 1 comprises .a tubular casing 12 of insulating material and a pair of metal end caps 13 and 14 suitably sealed to the opposite ends of casing 12.
  • contact 17 is a stationary contact brazed to the lower end of a stationary conductive contact rod 170; and contact 18 is a movable contact brazed to the upper end of vertically movable conductive rod 180.
  • the movable contact rod 18a projects freely through an opening in the lower end cap 14, and a flexible metal bellows 20 provides a suitable seal thereabout that allows vertical movement of the contact rod 18a without impairing the vacuum inside envelope 11.
  • All of the internal parts of the interrupter are substantially free of surface contaminants. hese clean surfaces are obtained by suitable conventional vacuum processing, which involves baking out the interrupter during its evacuation.
  • Closing of the interrupter is effected by driving the contact rod 18a in an upward direction to drive movable contact 18 into engagement with stationary contact 17. Opening is effected by returning the movable contact from its engaged position downwardly to its solid line position shown.
  • an arc is drawn therebetween. Assuming an alternating current, this are persists until a natural current zero, at which time it vanishes and is prevented from reigniting by the high dielectric strength of the vacuum in the envelope 12.
  • a suitable metal shield 21 "of tubular form surrounds the contact to condense the metal vapors generated by the arc, thus assisting in the interrupting process.
  • the illustrated interrupter is intended for use in applications where it will be opened and closed frequently.
  • I include as a major component of the contact material a refractory metal such as tungsten, which because of its high melting and boiling points has less tendency to vaporize than nonrefractory metals.
  • the tungsten is in the form of a sintered matrix of a porous character. The pores of the matrix are filled with the high-conductivity copper-base alloy soon to be described.
  • the contacts When the contacts are driven into engagement during closing, they may bounce apart slightly and draw an arc therebetween before being driven back into engagement. This arc tends to produce welding together of the contacts.
  • the contacts of a vacuum interrupter have a greater tendency toward such welding than those of other type interrupters because their surfaces are exceptionally clean and free of weld-inhibiting films.
  • the refractory metal matrix will help resist such welding.
  • weld resistance as possible of the refractory metal
  • 1 infiltrate the tungsten matrix with an alloy of copper and bismuth containingless than 2 percent bismuth by weight of the alloy.
  • I use less than 1 percent bismuth by weight, e.g., one-half percent.
  • My contacts are made by sintering refractory metal particles in hydrogen and then infiltrating the sintered mass with a substantially gas-free alloy of copper-bismuth in a hydrogen atmosphere at a temperature above the melting point of the copper (about 2,200 E). The resulting composite is then cooled and thereafter degassed by heating to a temperature slightly above the melting point of copper, about 2,000 F., in an argon atmosphere.
  • a vacuum-type circuit interrupter comprising a highly evacuated envelope and a pair of contacts within said envelope which are relatively movable into and out of engagement with each other, each of said contacts comprising a porous matrix of a refractory metal and an alloy consisting essentially of copper and bismuth filling the pores of said matrix, the percentage of bismuth being less than 2 percent by weight of the copper-bismuth alloy, said refractory metal constituting the major percentage by weight of the contact material; a pair of contact-support members, one for each contact, within said envelope; and a brazed joint between each of said contacts and its associated support member, said brazed joint being in contact with the porous matrix of said contact; the brazed joint having a tensile strength substantially greater than any welds forming between the contacts of said interrupter during operation thereof, thereby rendering said brazed joint capable of acting as the sole means for attaching said contact to its support member.

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  • High-Tension Arc-Extinguishing Switches Without Spraying Means (AREA)
  • Contacts (AREA)
US763116A 1968-09-27 1968-09-27 Vacuum-type circuit interrupter with contacts containing a refractory metal Expired - Lifetime US3596025A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US76311668A 1968-09-27 1968-09-27

Publications (1)

Publication Number Publication Date
US3596025A true US3596025A (en) 1971-07-27

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ID=25066919

Family Applications (1)

Application Number Title Priority Date Filing Date
US763116A Expired - Lifetime US3596025A (en) 1968-09-27 1968-09-27 Vacuum-type circuit interrupter with contacts containing a refractory metal

Country Status (4)

Country Link
US (1) US3596025A (de)
DE (1) DE1948451A1 (de)
FR (1) FR2019077A1 (de)
GB (1) GB1213759A (de)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3805000A (en) * 1970-03-23 1974-04-16 Itt Vacuum interrupter and methods of making contacts therefor
JPS505866A (de) * 1973-05-19 1975-01-22
US4399339A (en) * 1981-03-02 1983-08-16 Cherry Electrical Products Corporation Electrical contact
US5557083A (en) * 1993-07-14 1996-09-17 Hitachi, Ltd. Vacuum circuit breaker and electric contact
US5852266A (en) * 1993-07-14 1998-12-22 Hitachi, Ltd. Vacuum circuit breaker as well as vacuum valve and electric contact used in same

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS60172117A (ja) * 1984-02-17 1985-09-05 三菱電機株式会社 真空しや断器用接点

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3805000A (en) * 1970-03-23 1974-04-16 Itt Vacuum interrupter and methods of making contacts therefor
JPS505866A (de) * 1973-05-19 1975-01-22
JPS5341782B2 (de) * 1973-05-19 1978-11-07
US4399339A (en) * 1981-03-02 1983-08-16 Cherry Electrical Products Corporation Electrical contact
US5557083A (en) * 1993-07-14 1996-09-17 Hitachi, Ltd. Vacuum circuit breaker and electric contact
US5852266A (en) * 1993-07-14 1998-12-22 Hitachi, Ltd. Vacuum circuit breaker as well as vacuum valve and electric contact used in same
US6048216A (en) * 1993-07-14 2000-04-11 Hitachi, Ltd. Vacuum circuit breaker as well as vacuum valve and electric contact used in same

Also Published As

Publication number Publication date
FR2019077A1 (de) 1970-06-26
DE1948451A1 (de) 1970-04-09
GB1213759A (en) 1970-11-25

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