US3497652A - Vacuum-type circuit interrupter with contact material containing a minor percentage of aluminum - Google Patents

Vacuum-type circuit interrupter with contact material containing a minor percentage of aluminum Download PDF

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Publication number
US3497652A
US3497652A US773980A US3497652DA US3497652A US 3497652 A US3497652 A US 3497652A US 773980 A US773980 A US 773980A US 3497652D A US3497652D A US 3497652DA US 3497652 A US3497652 A US 3497652A
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contacts
aluminum
alloy
copper
vacuum
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US773980A
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Fordyce H Horn
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General Electric Co
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General Electric Co
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    • 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

  • a vacuum-type circuit interrupter comprising a pair of contacts relatively movable into and out of engagement, the contacts having circuit-making and breaking regions formed of an alloy consisting essentially of copper-aluminum and bismuth, the aluminum being present in a quantity of between 9% and 15% by weight of the copperaluminum and the bismuth being present in a quantity of a few percent or less by weight of the total alloy.
  • This invention relates to a vacuum-type circuit interrupter and, more particularly, to contact structure for such an interrupter.
  • the contacts of a vacuum interrupter be formed of an alloy consisting essentially of a major constituent which which is a good-conductivity, nonrefractory metal and a minor constituent which is a metal having a lower freezing temperature than the major constituent and little or no solid-state solubility in the major constituent, the minor constituent being present in a quantity of a few percent or less by weight of the alloy.
  • Such alloys are copper-bismuth, copper-lead, copper-tellurium, silverbismuth, silver-lead, and silver-tellurium, each alloy containing a few percent or less by weight of the second mentioned, or minor, constituent.
  • Vacuum interrupters having contacts of these alloys can interrupt high inductive currents (e.g., in excess of 8,000 amperes symmetrical R.M.S.) at rated voltage, can carry and close against such currents without producing objectionable contact-welds, and can successfully withstand impulse crest voltages of at least 95 kv. and continuous 60 cycle voltages of at least 36 kv. R.M.S. when their contacts are fully separated.
  • These voltages are those which indoor oilless circuit breakers rated at 7.2 kv. and 13.8 kv. must be capable of withstanding if they are to meet the requirements of the National Electrical Manufactures Association (NEMA) Standards for Power Circuit Breakers, Publication 364-1954, March 1954, revised November 1955, part 2, page 5.
  • NEMA National Electrical Manufactures Association
  • interrupter For higher voltage ratings and for certain switching operations, such as capacitance switching, even more diflicult dielectric strength requirements are imposed upon the interrupter.
  • One severe measure of an interrupters ability to meet these more difiicult dielectric strength requirements is its ability to withstand a high transient voltage immediately following a contact-separating operation which fractures a weld between the contacts, especially the type of weld formed by closing on several thousand amperes or more current.
  • An object of the present invention is to provide a vacuum interrupter that has improved ability to withstand high voltages immediately following a contact-separating operation that fractures a weld between the contacts.
  • Another object is to consistently achieve a high dielectric strength between the contacts immediately following contact-separation which follows closing on high inrush currents.
  • Another object is to provide a vacuum interrupter capable of performing as set forth in the immediately preceding paragraphs and also capable (1) of interrupting high inductive currents of 8,000 or more amperes R.M.S. symmetrical, (2) of being free from objectionable contact-welding, and (3) of meeting the high dielectric strength requirements imposed by conventional standards at rated circuit voltages of 14.4 kv. and higher.
  • the above NEMA Standards require that an oilless circuit breaker rated at 14.4 kv. be capable of withstanding kv, peak impulse voltage and 50 kv. R.M.S. continuous voltage.
  • Another object is to provide vacuum interrupter contacts capable of performing as set forth in the above objects and also capable of being more easily and less expensively made than the beryllium-containing contacts disclosed in our pending application S.N. 647,646. The latter application was filed on June 21, 1967, and is assigned to the assignee of the present invention.
  • the vacuum interrupter with contacts having their circuitmaking and breaking regions made of an alloy of copperaluminum and bismuth.
  • the aluminum is present in a quantity of between 9% and 15 by weight of the copper-aluminum, and the bismuth is present in a quantity of a few percent or less by weight of the total alloy. In a preferred form of the invention, the aluminum is present in a quantity of between 11 and 13 percent by weight of the copper-aluminum.
  • FIG. 1 is a sectional view of a vacuum-type circuit interrupter embodying one form of our invention.
  • FIG. 2 is an enlarged perspective view of one of the contacts of the interrupter of FIG. 1.
  • a highly evacuated envelope 10 comprising a casing 11 of a suitable insulating material, such as glass, and a pair of metallic end caps 12 and 13, closing off the ends of the casing.
  • Suitable seals 14 are provided be tween the end caps and the casing to render the envelope 10 vacuum-tight.
  • the normal pressure within the envelope 10 under static conditions is lower than 10* mm.
  • casing 11 The internal insulating surfaces of casing 11 are protected from the condensation of arc-generated metal vapors thereon by means of a tubular metallic shield 15 suitably supported on the casing 11 and preferably isolated from both end caps 12 and 13. This shield acts in a well-known manner to intercept arc-generated metallic vapors before they can reach the casing 11.
  • the upper contact 17 is a stationary contact suitably attached to a conductive rod 17a, which at its upper end is united to the upper end cap 12.
  • the lower contact 18 is a movable contact joined to a conductive operating rod 18a which is suitably mounted for vertical movement. Downward motion of the contact 18 separates the contacts and opens the interrupter, whereas return movement of contact 18 reengages the contacts and thus closes the interrupter.
  • a typical gap length when the con tacts are fully-open is about /2 inch.
  • the operating rod 181 projects through an opening in the lower end cap 13, and a flexible metallic bellows 20 provides a seal about the rod 18a to allow for vertical movement of the rod without impairing the vacuum inside the envelope 10. As shown in FIG. 1, the bellows 20 is secured in sealed relationship at its respective opposite ends to the operating rod 18a and the lower end cap 13.
  • All of the internal parts of the interrupter are substantially free of surface contaminants. These clean surfaces are obtained by suitably processing the interrupter, as by baking it out during its evacuation. A typical bakeout temperature is 400 C.
  • the contacts 17 and 18 are effectively freed of gases absorbed internally of the contact body so as to preclude evolution of these gases during high current arcing. The manner in which these internal gases are removed will be referred to in more detail hereinafter.
  • each contact is of a disk shape and has one of its major surfaces facing the other contact.
  • the central region of each contact is formed with a recess 29 in this major surface and an annular circuitmaking and circuit-breaking area 30 surrounds this recess.
  • These annular circuit-making and breaking areas 30 abut against each other when the contacts are in their closed position of FIG. 1, and are of such a diameter that the current flowing through the closed contacts follows a loop-shaped path L, as is indicated by the dotted lines of FIG. 1.
  • This circumferentially-acting magnetic force is preferably produced by a series of slots 32 provided in the disks and extending from the outer periphery of the disks radially inward by generally spiral paths, as is shown in FIG. 2.
  • slots 32 correspond to similarly designated slots in the aforementioned Schneider patent and thus, force the current flowing to or from an arc terminal located at substantially any angular point on the outer peripheral region of the disk to follow a path that has a net component extending generally tangentially with respect to the periphery in the vicinity of the arc.
  • This tangential configuration of the current path results in the development of a net tangential force component, which tends to drive the arc in a circumferential direction about the contacts.
  • the arc may divide into a series of parallel arcs, and these parallel arcs move rapidly about the contact surface in a manner similar to that described hereinabove.
  • One of the problems that the present invention is concerned with is providing a single-break vacuum interrupter of the general type described up to this point that is capable of meeting the conventional NEMA specification for an oilless circuit breaker having a voltage ratlng of at least 14.4 kv. and an interrupting rating of at least 8000 amperes R.M.S. symmetrical and is also capable of consistently withstanding high transient voltages applied immediately following a contact-separating operation that fractures a weld between the contacts.
  • high transient voltages we are referring to those typically encountered in switching and interrupting circuits rated at 14.4 kv. and higher; and in referring to a weld between the contacts, we are particularly concerned with those welds such as might be formed when an arc carrying inrush currents of several thousand amperes is developed during contact-closing.
  • circuit-making and circuit-breaking portions 30 of the vacuum interrupter contacts of an alloy consisting of copper-aluminum and bismuth, the aluminum being present in a quantity of between 9 and 15 percent by weight of the copper-aluminum and the bismuth being present in a quantity of a few percent or less by weight of the total alloy.
  • a specific alloy which has shown exceptional ability to meet these requirements is a copperaluminum bismuth alloy consisting essentially of copper, aluminum in a quantity of 12 percent by weight of the copper-aluminum, and bismuth in a quantity of 1% by weight of the total alloy. This material is referred to hereinafter as Cu-Al-Bi (12% Al).
  • the material of the prior art found most satisfactory for the contacts of the vacuum interrupter has been an alloy of copper-bismuth consisting of copper and a few percent or less of bismuth by weight, e.g., 0.5 percent.
  • a vacuum interrupter with contacts of this material can meet the conventional NEMA specification for oilless circuit breakers rated at 14.4 kv. and 8000 amperes R.M.S. interrupting current, but it has not been able to withstand as consistently as might be desired a high voltage transient applied following a contact-separating operation which fractures a weld between the contacts.
  • the presence of this fine dispersion produces a better distribution of the bismuth inside the grains and greatly reduces bismuth segregation at the grain boundaries.
  • the bismuth while still being available as a weld-inhibiting agent, has much less of an embrittling effect on the parent alloy, and the result is improved mechanical strength and ductility. These improvements in mechanical strength and ductility are believed to contribute to improved dielectric strength because they reduce the possibility that discrete particles of metal will be pulled out of the opposite contact when the contacts are separated following such minor contact-welding as does occur.
  • the bismuth is not concentrated at the grain boundary in the parent alloy, it is still present, distributed throughout the grain structure and is available to segregate in the weld zone caused by arcing.
  • This segregated bismuth weakens the weld by forming a weak interface along which the contacts can easily separate when subsequently opened. This further reduces the possibility that a discrete particle of metal will be pulled out of the opposite contact along a grain boundary. By reducing this possibility, we are able to maintain contact surfaces of greater smoothness with fewer protuberances of a size that would encourage a dielectric breakdown.
  • the alloy contains a high percentage of the gamma phase and the bismuth is not dispersed in the desired manner, both resulting in excessive brittleness.
  • Such brittleness can lead to cracking on closing impact, resulting in loose pieces that can adversely affect dielectric strength.
  • the invention in its broader aspects is also considered to be applicable to copper-base alloy contacts which contain the other weldinhibiting agents of the aforesaid Lalferty et al. patent.
  • copper-base alloy contacts with lead or tellurium can be dielectrically improved by adding aluminum in an amount of 9 to 15 percent by weight of the copper-' aluminum alloy.
  • the weldinhibiting agent is substantially insoluble in the solid state in both copper and aluminum and has a lower freezing temperature than copper-aluminum.
  • silverbase alloy contacts with bismuth or lead weld-inhibitors can be improved dielectrically by including aluminum in approximately 5 to 10% by weight of the silver-aluminum alloy.
  • a nickel-base alloy with a bismuth weld-inhibitor can be improved dielectrically by including aluminum in approximately 8 to 13% by weight of the nickel-aluminum alloy.
  • the first-mentioned metal constituent of an alloy is referred to as the primary metal of the alloy.
  • each separate constituent first should ,be suitably processed to free it of sorbed gases and other contaminants, as, for example, by the zone-refining process described in US. Patent No. 3,234,351, Hebb, assigned to the assignee of the present invention.
  • the constituents are then melted and appropriately mixed together while they are in the liquid state, after which the temperature is lowered to cause the constituents to solidify and form the solid alloy.
  • a vacuum-type electric circuit interrupter (a) an envelope evacuated to a pressure of 10- mm.
  • the bismuth being present in a quantity of less than about percent by weight of the total alloy and in a suificient quantity to inhibit contact-welding, and being distributed throughout said alloy.
  • a vacuum type electric circuit interrupter compris- (a) an envelope evacuated to a pressure of mm.
  • At least one of said contacts having circuit-making and breaking regions formed of an alloy consisting essentially of copper-aluminum and a weld-inhibiting metal having substantially no solid-state solubility in copper or aluminum and having an effective freezing temperature below that of copper-aluminum,
  • the weld-inhibiting metal being present'in a quantity of less than about five percent by weight of the total alloy and in a quantity suflicient to inhibit contact-welding, and being distributed throughout said alloy.
  • a vacuum-type electric circuit interrupter comprismg:
  • the aluminum being present in a quantity of: between 9 and 15 percent by weight of the copperaluminum in the case of copper-aluminum-bismuth, between 5 and 10 percent by weight of the silveraluminum in the case of silver-aluminum-bismuth, and between 8 and 13 percent by weight of the nickel-aluminum in the case of nickel-aluminumbismuth,
  • the bismuth being present in a quantity of less than about five percent by weight of the total alloy, in a quantity sufficient to inhibit contact-welding, and being distributed throughout said alloy.
  • a vacuum-type electric circuit interrupter compris- (a) an envelope evacuated to a pressure of 10* mm.
  • At least one of said contacts having circuit-making and breaking regions formed of an alloy consisting essentially of (1) copper-aluminum containing 9 to 15 percent by weight of aluminum, Or (2) silveraluminum containing 5 to 10 percent by weight of aluminum, or (3) nickel-aluminum containing 8 to 13 percent by weight of aluminum, and a weld-inhibiting metal,
  • said weld-inhibiting metal having substantially no solid-state solubility in the primary metal of the alloy or in aluminum and having an effective freezing temperature below that of the primary metal-aluminum alloy,
  • said weld-inhibiting metal being present in a quantity less than about five percent by weight of the total alloy and in a quantity sufiicient to inhibit contactwelding, and being distributed throughout said total alloy.

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US773980A 1968-11-01 1968-11-01 Vacuum-type circuit interrupter with contact material containing a minor percentage of aluminum Expired - Lifetime US3497652A (en)

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US77398068A 1968-11-01 1968-11-01

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US (1) US3497652A (fr)
JP (1) JPS4747946B1 (fr)
DE (1) DE1954589C3 (fr)
FR (1) FR2022398A1 (fr)
GB (1) GB1270719A (fr)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3663775A (en) * 1970-03-24 1972-05-16 Gen Electric Vacuum interrupter with contacts containing a minor percentage of aluminum
US3819897A (en) * 1972-01-21 1974-06-25 Siemens Ag Vacuum switch with contact material containing a minor percentage of aluminum
US4129761A (en) * 1976-05-27 1978-12-12 Tokyo Shibaura Electric Co., Ltd. Vacuum circuit breaker
US4129760A (en) * 1976-05-28 1978-12-12 Tokyo Shibaura Electric Co., Ltd. Vacuum circuit breaker
US5508483A (en) * 1995-03-24 1996-04-16 Texas Instruments Incorporated High pressure switch apparatus
US20160314916A1 (en) * 2015-04-22 2016-10-27 Lsis Co., Ltd. Contact of vacuum interrupter

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3014108A (en) * 1959-01-02 1961-12-19 Gen Electric Vacuum switch
US3140373A (en) * 1962-01-24 1964-07-07 Gen Electric Arc ionizable beryllium electrodes for vacuum arc devices
US3246979A (en) * 1961-11-10 1966-04-19 Gen Electric Vacuum circuit interrupter contacts

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3014108A (en) * 1959-01-02 1961-12-19 Gen Electric Vacuum switch
US3246979A (en) * 1961-11-10 1966-04-19 Gen Electric Vacuum circuit interrupter contacts
US3140373A (en) * 1962-01-24 1964-07-07 Gen Electric Arc ionizable beryllium electrodes for vacuum arc devices

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3663775A (en) * 1970-03-24 1972-05-16 Gen Electric Vacuum interrupter with contacts containing a minor percentage of aluminum
US3819897A (en) * 1972-01-21 1974-06-25 Siemens Ag Vacuum switch with contact material containing a minor percentage of aluminum
US4129761A (en) * 1976-05-27 1978-12-12 Tokyo Shibaura Electric Co., Ltd. Vacuum circuit breaker
US4129760A (en) * 1976-05-28 1978-12-12 Tokyo Shibaura Electric Co., Ltd. Vacuum circuit breaker
US5508483A (en) * 1995-03-24 1996-04-16 Texas Instruments Incorporated High pressure switch apparatus
US20160314916A1 (en) * 2015-04-22 2016-10-27 Lsis Co., Ltd. Contact of vacuum interrupter
US9852858B2 (en) * 2015-04-22 2017-12-26 Lsis Co., Ltd. Contact of vacuum interrupter

Also Published As

Publication number Publication date
GB1270719A (en) 1972-04-12
FR2022398A1 (fr) 1970-07-31
JPS4747946B1 (fr) 1972-12-02
DE1954589C3 (de) 1980-06-04
DE1954589B2 (de) 1979-09-20
DE1954589A1 (de) 1970-06-25

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