US3667871A - Contact structures for vacuum-type circuit interrupters having radially outwardly-extending spokes - Google Patents

Contact structures for vacuum-type circuit interrupters having radially outwardly-extending spokes Download PDF

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Publication number
US3667871A
US3667871A US797930A US3667871DA US3667871A US 3667871 A US3667871 A US 3667871A US 797930 A US797930 A US 797930A US 3667871D A US3667871D A US 3667871DA US 3667871 A US3667871 A US 3667871A
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Prior art keywords
contact
arc
primary
vacuum
outwardly
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Expired - Lifetime
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US797930A
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English (en)
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Richard L Hundstad
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Westinghouse Electric Corp
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Westinghouse Electric Corp
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    • 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
    • H01H33/60—Switches wherein the means for extinguishing or preventing the arc do not include separate means for obtaining or increasing flow of arc-extinguishing fluid
    • H01H33/66—Vacuum switches
    • H01H33/664—Contacts; Arc-extinguishing means, e.g. arcing rings

Definitions

  • WITNESSES NVENTOR Richard L. Hundstod 3,667,871 CONTACT STRUCTURES FOR VACUUM-TYPE CIRCUIT INTERRUPTERS HAVING RADIALLY OUTWARDLY-EXTENDING SPOKES Richard L. Hundstad, Pittsburgh, Pa., assignor to Westinghouse Electric Corporation, Pittsburgh, Pa. Filed Feb. 10, 1969, Ser. No. 797,930
  • the primary electrode contact surfaces of conventional circuit interrupters i.e., the surfaces which conduct the current from one electrode to another during normal steady state operation, are subjected to very intense heat while performing their function during a current inter ruption.
  • the electrode surface must support the arc from its initiation at the time the electrodes open until its extinction at approximately zero current. This are energy causes melting, erosion and general deterioration of the surfaces. 'The construction set forth in the aforesaid United States patent partially circumvents this problem by providing primary surfaces for conducting the current during normal steady'state operation, and additional surfaces surrounding the primary surfaces for arc-energy dissipation during an interruption.
  • Spiral slots in the energy-dissipation surfaces cause the are to spiral radially outwardly under the influence of the jXB forces.
  • the spiral slots also provide a cusp-type magnetic field, which causes the arc to rotate under the influence of the jXB forces.
  • Electrodes for vacuum-type circuit interrupters of the construction set forth in the aforesaid patent are not very elfective in providing:' the; necessary jxBforces to g 3,667,871 Patented June 6, 1972 move the arc radially outwardly and away from the contact surfaces.
  • the conically-shaped energy dissipation portion of the electrodes, which extend radially outwardly from the contact surfaces, have a large cross-sectional area through which the current may flow radially outwardly. As a result, the current densities are low, and the self-induced magnetic fields are small, distributed, and ineffective in forcing the are from the contact surfaces.
  • the contact construction'for a vacuum-type circuit interrupter having primary and secondary, or arc-dissipation surfaces. The are is initially established at the primary contact surfaces, and then is moved radially outwardly to the arcdissipation surfaces, and arc extinction occurs at these latter secondary surfaces.
  • the construction according to the present invention has spokes, or radially-outwardly-extending contact bars which extend from the primary contact surfaces, and these spokes are purposely made smallv in cross-sectional area adjacent to the primary contact button so as to concentrate the self-induced magnetic fields as well as the arc columns and, thereby, effectively provide the necessary j B forces to move the arc radially outwardly and away from the primary contact surfaces.
  • a morespecific object of the present invention is to provide an improved contact, or electrode construction for a vacuum-type circuit interrupter utilizing primary contact surfaces and outwardly-extending spokes, or contact bars, which move the initially established are outwardly away from the primary contact surfaces.
  • Still a further object of the present invention is the provision of an improved electrode or contact construction for a vacuum-type circuit interrupter in which primary contact surfaces are provided of one material, and the secondary orarc-dissipation surfaces are provided utilizing another contact material. 7
  • a vacuum-type circuit interrupter has separable contacts, at least one of which uses, preferably, a generallydiscshaped primary contact surface of one material, such as a copper-bismuth alloy, and spokes or contact bars, which extend radially outwardly from the primary contact surfaces, and the secondary contact surfaces are preferably formed of a difierent contact material, such as pure copper, for example.
  • FIG. 1 is a vertical sectional view of a vacuum-type circuit interrupter embodying the contact construction of the present invention the contacts being shown in full lines in the open-circuit position;
  • FIG. 2 is a detailed side elevational view taken of the contact structure of FIG. 1 in an initial stage of the opening operation
  • FIG. 3 is a view similar to that of FIG. 2, but illustrating the arc position at a later point of time during the opening operation;
  • FIG. 4 is a plan view of one of the contacts drawn to an enlarged scale
  • FIG. 5 is a sectional view taken along the line VV of FIG. IV; and, I
  • FIG. 6 is a plan view of the primary contact button prior to assembly.
  • a metallic arc initiates between the separating electrodes, and serves as a vehicle for current conduction until the normal alternating current cyclic variation of current drops the magnitude of the current below the chopping current.
  • a highly-evacuated envelope 1 comprising a casing 2 of suitable insulating material, and a pair of metallic end caps 3 and 4 closing off the ends of the casing. Suitable seals 5 are provided between the end caps and the casing to render the envelope vacuum-tight.
  • the normal pressure within the envelope 1 under static conditions is lower than torr; so that reasonable assurance is had that the mean free path for electrons will be longer than the potential breakdown paths within the envelope.
  • a pair of relatively movable disk-shaped contacts or electrodes 7 and 8 shown in full lines in their separated or open-circuit position. When the contacts are separated, there is an arcing gap 9 located therebetween.
  • the upper contact 7 is a stationary contact suitably secured to a conductive rod 10, which at its upper end is united to the upper end cap 3.
  • the lower contact 8 is a movable contact joined to a conductive operating rod 11, which is suitably mounted for movement.
  • the operating rod 11 projects through an opening 12 in the lower end cap 4, and a flexible metallic bellows 13 provides a seal about the rod 11 to allow for movement of the rod without impairing the vacuum inside the envelope 2. As shown in FIG. 1, the bellows 13 is secured in sealing relationship at its respective opposite ends to the operating rod 11 and to the end cap 4.
  • suitable actuating means (not shown) is provided for driving the movable contact 8 upwardly into engagement with the stationary contact 7 so as to close the interrupter.
  • the closed position of the movable contact is indicated by the dotted line 14.
  • the actuating means is also capable of returning the contact 8 to its illustrated solid-line open position so as to open the interrupter.
  • a circuit-opening operation will, for example, entail a typical gap length, when the contacts are fully separated, of perhaps /2 inch.
  • the internal insulating surfaces of the casing 2 are protected from the condensation of arc-generated metallic vapor and particles thereon by means of a tubular metallic shield 16 suitably supported on the casing 2 and preferably isolated from both end caps 3 and 4.
  • This shield 16 acts to intercept and to condense arc-generated metallic vapors before they can reach the casing 2.
  • a pair of end shields 17 and 18 are provided at opposite ends of the central shield 16.
  • a contact, or electrode 8 which has radially-outwardlyextending spokes, or contact bars 19. With attention being area of the spoke, or contact bar at its outward periphery 19b. Although only six spokes or contact bars 19 are shown, there may be more or less depending on the current rating of the vacuum-interrupting device.
  • a highly efficient conducting material which has a relatively low weld strength, such as a copper-bismuth alloy, such as set forth in United States patent Lee et al. 2,975,256.
  • the arc which is initially established, is formed at the primary contact surfaces 7a, 8a, and is designated by the reference numeral 16. Soon thereafter, by virtue of the magnetic forces, the initially-established are 15 is moved outwardly along the spoke, or contact bar surfaces 19 to the outer edges of the secondary contacts, where are extinction takes place.
  • the construction proposed by the present invention alleviates the problem of general deterioration by effectively confining the arc and resultant melting to the en ergy-dissipation surfaces.
  • the proposed construction has spokes extending from the contact surfaces, and these spokes are purposely made small in cross-sectional area adjacent to the primary contact surface so as to concentrate the self-induced magnetic fields as well as the arc columns, and thereby effectively provide the necessary jXB forces to move the arc radially outwardly and away from the primary contact surfaces.
  • the center primary contact button may be made of a copper-bismuth alloy, such as, for example, 99.7% copper and .3% bismuth by weight. In this event, it is desirable to have the outwardly extending spokes or contact bars made of pure copper.
  • spoke portions 19 of the two contacts need not be axially or longitudinally aligned, but better results are achieved if they are in longitudinal alignment as shown directed to the plan view of FIG. 4 of one of the elec- I trodes 8, it will be noticed that the cross-sectional area at the hub portion 19a is less than the cross-sectional in the drawing.
  • a vacuum-type circuit interrupter including, in combination: (a) means defining an evacuated envelope; (b) a pair of separable contacts disposed within the I evacuated envelope separable to establish arcing; (0) at least one of the separable contacts including a central primary contact portion and a plurality of circumferentially spaced radially-outwardly-extending conducting spoke portions emanating only radial- 1y outwardly from said central primary contact portion and connected thereto,
  • the primary separable contacts each has a central primary contact portion and a plurality of radially-cutwardly-extending conducting spoke portions emanating radially outwardly from said central primary contact portion and connected thereto.

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  • High-Tension Arc-Extinguishing Switches Without Spraying Means (AREA)
US797930A 1969-02-10 1969-02-10 Contact structures for vacuum-type circuit interrupters having radially outwardly-extending spokes Expired - Lifetime US3667871A (en)

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US79793069A 1969-02-10 1969-02-10

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US3667871A true US3667871A (en) 1972-06-06

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US (1) US3667871A (de)
AT (1) AT294964B (de)
CH (1) CH503365A (de)
DE (1) DE2003781A1 (de)
GB (1) GB1291045A (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3814880A (en) * 1972-06-20 1974-06-04 Westinghouse Electric Corp Vacuum interrupter contacts having energy dissipation surfaces
US3889081A (en) * 1972-06-20 1975-06-10 Westinghouse Electric Corp Vacuum interrupter contacts having energy dissipation surfaces

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3814880A (en) * 1972-06-20 1974-06-04 Westinghouse Electric Corp Vacuum interrupter contacts having energy dissipation surfaces
US3889081A (en) * 1972-06-20 1975-06-10 Westinghouse Electric Corp Vacuum interrupter contacts having energy dissipation surfaces

Also Published As

Publication number Publication date
DE2003781A1 (de) 1970-09-03
AT294964B (de) 1971-12-10
CH503365A (de) 1971-02-15
GB1291045A (en) 1972-09-27

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