US3686456A - Contact structure for an electric circuit breaker - Google Patents

Contact structure for an electric circuit breaker Download PDF

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Publication number
US3686456A
US3686456A US26888A US3686456DA US3686456A US 3686456 A US3686456 A US 3686456A US 26888 A US26888 A US 26888A US 3686456D A US3686456D A US 3686456DA US 3686456 A US3686456 A US 3686456A
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United States
Prior art keywords
contacts
bismuth
circuit breaker
silver
contact
Prior art date
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
US26888A
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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
Application granted granted Critical
Publication of US3686456A publication Critical patent/US3686456A/en
Anticipated expiration legal-status Critical
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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
    • H01H1/021—Composite material
    • H01H1/023—Composite material having a noble metal as the basic material
    • H01H1/0233—Composite material having a noble metal as the basic material and containing carbides

Definitions

  • ABSTRACT Discloses a circuit breaker with a pair of contacts that [56] References c are located in a fluid medium and are relatively mova- UNITED STATES PATENTS ble into and out of engagement with each other. Each 1 of these contacts comprises a porous skeleton of a 3,610,859 10/1971 Schremel' et --200/166 C refractory material, such as tungsten or-tungsten car- 2,247,754 7/1941 I-Ienselet al.
  • a high conductivity metal that has excellent properties for use as the infiltrant is silver.
  • Silver has the highest electrical and thermal conductivity of all metals, has the'lowest Contact resistance, and will not form stable oxides on its surface.
  • An object of my invention is to impart improved weld resistance to refractory material-silver contacts without significant loss of the desired high conductivity properties of the silver and without significantly impairing the ability of the contacts to withstand high impacts without fracturing or being otherwise mechanically damaged.
  • I provide a circuit breaker with a pair of contacts that are located in a fluid medium and are relatively movable into and out of engagement with each'other.
  • Each of these contacts comprises a porous skeleton of refractory conductive material andan alloy of silver and bismuth filling the pores of the skeleton.
  • the percentage of bismuth is less than about 2 percent by weight of the silverbismuth alloy.
  • FIGURE is a simplified showing of Contact structure embodying one form of the invention.
  • This circuit breaker comprises a contact arm that is mounted for limited pivotal motion on a stationary fulcrum l2.
  • Atension spring 14 biases arm 10 in a counterclockwise direction about its fulcrum 12 into engagement with a stationary stop 16.
  • Movable into and out of engagement with the stationary Contact is a movable contact 20.
  • This movable Contact 20 comprises a contact arm 22 and a Contact element 24 brazed to the surface of the Contact arm facing the stationary contact 10, 18.
  • contact arm 7 22 When contact arm 7 22 is driven to the left, its contact element 24 engages into a suitable arc chute (not shown) where it isexttationary contact element 18, thereby completing a circuit through the contacts.
  • the stationary Contact 10, 18 pivots in a clockwise direction about fulcrum 12 against the bias of spring 14 to provide for a small amount of Contact wipe.
  • the movable contact 20 follows the stationary contact 10, 18 during such Contact wipe, and the two contacts are in high pressure engagement with each other at the end of the closing operation. Contact pressure while the circuit breaker is closed is maintained by the spring 14.
  • the material heretofore found most satisfactory for the above-described contact elements has been a tungsten carbide-silver material comprising a skeleton of tungsten-carbide infiltrated with substantially pure silver.
  • this material is characterized by good resistance to arc erosion and contact-welding, by high electrical and thermal conductivity, and by low contact resistance.
  • This material is characterized by good resistance to arc erosion and contact-welding, by high electrical and thermal conductivity, and by low contact resistance.
  • there are certain switching applications that are especially severe from a contact-welding standpoint where these prior contacts have not provided enough resistance to contact-welding. Excessive forces have sometimes been required during an opening operation to fracture the weld between the contacts, particularly those welds which are formed by closing against high short circuit currents or by contactpopping in response to high short circuit currents.
  • a preferred percentage of the bismuth is about one-half percent by weight of the silver-bismuth alloy.
  • Tests were run in order to compare the strength of the welds formed with the tungsten carbide-silver contacts with those formed under corresponding conditions with the tungsten carbide-silver-bismuth contacts.
  • a pair of engaged contacts corresponding to those illustrated were traversed by high currents that caused them to pop apart, immediately following which they were forced to reengage under arcing conditions, with resultant welding together of the contacts.
  • the strength of each weld was established by determining the pounds of force subsequently required to break the weld to separate the contacts. With the prior contacts, i.e., the WC-Ag contacts, welds having a strength of 280 to 480 pounds were formed.
  • the strength of the welds formed under substantially the same conditions of operation was drastically reduced to only to 35 pounds.
  • the tungsten carbide was present in an amount of about 50 percent by weight.
  • the maximum amount of bismuth that can be used is limited by the minimum permissible impact strength of the resultant contacts.
  • specimens of rectangular cross-section bar form, each thirteen-sixteenths inch long, one-fourth inch wide, and one-eighth inch deep, were prepared and subjected to an Izod or Standard Impact Test. The energy required to fracture each specimen was measured and recorded. The results of these tests may be tabulated as follows:
  • the above contacts were made by first providing the various ingredients in powdered form in the weight percentages desired for the final contact. Then, all of the bismuth powder is mixed with part of the silver powder, and this mixture is pressed into a blank of suitable form, which is reserved for use later in the process. All
  • the tungsten carbide powder is thoroughly mixed with the remainder of the silver powder, and this mixture is pressed and sintered at a temperature of approximately 2,300 F in a hydrogen atmosphere to provide a rigid structure.
  • This structure is cooled and then reheated in hydrogen to a temperature above the melting point of silver, at which time the silver-bismuth blank previously formed is placed in contact with the WC-Ag structure, causing the blank to melt and infiltrate the WC-Ag structure. Thereafter; the resulting composite is c led and machined to ize.
  • a circuit breaker comprising a pair of contacts located in a fluid medium and relatively movable into and out of engagement with each other, at least one of said contacts comprising a porous skeleton of a refractory material and an alloy consisting essentially of silver and bismuth filling the pores of said skeleton, the percentage of bismuth being less than about 2 percent by weight of the silver-bismuth alloy.
  • circuit breaker of claim 1 in which said refractory material is tungsten carbide.
  • circuit breaker of claim 1 in which said refractory material is tungsten carbide, and the percentage of bismuth is less than about 1 percent by weight of the silver-bismuth alloy.
  • circuit breaker of claim 1 in which said refractory material is tungsten carbide, and the percentage of bismuth is about A percent by weight of the silverbismuth alloy.
  • circuit breaker of claim 4 in which both of said contacts are of the same composite material defined in claim 4.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Composite Materials (AREA)
  • Materials Engineering (AREA)
  • Contacts (AREA)
US26888A 1970-04-09 1970-04-09 Contact structure for an electric circuit breaker Expired - Lifetime US3686456A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US2688870A 1970-04-09 1970-04-09

Publications (1)

Publication Number Publication Date
US3686456A true US3686456A (en) 1972-08-22

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Family Applications (1)

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US26888A Expired - Lifetime US3686456A (en) 1970-04-09 1970-04-09 Contact structure for an electric circuit breaker

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US (1) US3686456A (enrdf_load_stackoverflow)
JP (1) JPS464683A (enrdf_load_stackoverflow)
DE (1) DE2116450A1 (enrdf_load_stackoverflow)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3778576A (en) * 1970-01-29 1973-12-11 Echlin Manuf Corp Tungsten electrical switching contacts
US4088480A (en) * 1976-09-10 1978-05-09 Gte Laboratories Incorporated Process for preparing refractory metal-silver-cadmium alloys
US4999464A (en) * 1990-03-23 1991-03-12 General Electric Company Molded case circuit breaker contact and contact arm arrangement
US20240013985A1 (en) * 2022-07-05 2024-01-11 Miba Sinter Austria Gmbh Safety switch

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5514931A (en) * 1978-07-19 1980-02-01 Kokusan Denki Co Ltd Ignition device for internal combustion engine with over-rotation preventing device
DE3430490A1 (de) * 1984-08-18 1986-02-27 Doduco KG Dr. Eugen Dürrwächter, 7530 Pforzheim Schaltkammer fuer ein elektrisches schaltgeraet, insbesondere zur verwendung in der niederspannungs-energietechnik

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2247754A (en) * 1939-12-02 1941-07-01 Mallory & Co Inc P R Electric contact
US2975255A (en) * 1958-07-24 1961-03-14 Gen Electric Vacuum circuit interrupters
GB892339A (en) * 1957-08-01 1962-03-28 Siemens Ag Improvements in or relating to electrical contacts
US3143626A (en) * 1962-03-15 1964-08-04 Siemens Ag Sintered electric contact of high contact-fusing resistance
US3305324A (en) * 1966-05-26 1967-02-21 Mallory & Co Inc P R Tungsten powder bodies infiltrated with copper-titanium-bismuth or copper-titanium-tin
GB1071664A (en) * 1963-08-19 1967-06-14 South Wales Switchgear Improvements in or relating to vacuum circuit breakers
US3411902A (en) * 1968-01-22 1968-11-19 Mallory & Co Inc P R Method of producing infiltrated contact material
US3610859A (en) * 1967-08-05 1971-10-05 Siemens Ag Composite contact structure for vacuum-type circuit interrupters

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2247754A (en) * 1939-12-02 1941-07-01 Mallory & Co Inc P R Electric contact
GB892339A (en) * 1957-08-01 1962-03-28 Siemens Ag Improvements in or relating to electrical contacts
US2975255A (en) * 1958-07-24 1961-03-14 Gen Electric Vacuum circuit interrupters
US2975256A (en) * 1958-07-24 1961-03-14 Gen Electric Vacuum type circuit interrupter
US3143626A (en) * 1962-03-15 1964-08-04 Siemens Ag Sintered electric contact of high contact-fusing resistance
GB1071664A (en) * 1963-08-19 1967-06-14 South Wales Switchgear Improvements in or relating to vacuum circuit breakers
US3305324A (en) * 1966-05-26 1967-02-21 Mallory & Co Inc P R Tungsten powder bodies infiltrated with copper-titanium-bismuth or copper-titanium-tin
US3610859A (en) * 1967-08-05 1971-10-05 Siemens Ag Composite contact structure for vacuum-type circuit interrupters
US3411902A (en) * 1968-01-22 1968-11-19 Mallory & Co Inc P R Method of producing infiltrated contact material

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3778576A (en) * 1970-01-29 1973-12-11 Echlin Manuf Corp Tungsten electrical switching contacts
US4088480A (en) * 1976-09-10 1978-05-09 Gte Laboratories Incorporated Process for preparing refractory metal-silver-cadmium alloys
US4999464A (en) * 1990-03-23 1991-03-12 General Electric Company Molded case circuit breaker contact and contact arm arrangement
US20240013985A1 (en) * 2022-07-05 2024-01-11 Miba Sinter Austria Gmbh Safety switch

Also Published As

Publication number Publication date
DE2116450A1 (de) 1971-10-28
JPS464683A (enrdf_load_stackoverflow) 1971-11-18

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