US3560685A - Arc chute for an electric cuircuit breaker - Google Patents

Arc chute for an electric cuircuit breaker Download PDF

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Publication number
US3560685A
US3560685A US827583A US3560685DA US3560685A US 3560685 A US3560685 A US 3560685A US 827583 A US827583 A US 827583A US 3560685D A US3560685D A US 3560685DA US 3560685 A US3560685 A US 3560685A
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United States
Prior art keywords
arc
insulating material
chute
circuit breaker
runners
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Expired - Lifetime
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US827583A
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English (en)
Inventor
Cecil Bailey
Oscar C Frederick
Joseph L Talento
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General Electric Co
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General Electric Co
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Publication date
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H9/00—Details of switching devices, not covered by groups H01H1/00 - H01H7/00
    • H01H9/30—Means for extinguishing or preventing arc between current-carrying parts
    • H01H9/34—Stationary parts for restricting or subdividing the arc, e.g. barrier plate

Definitions

  • This invention relates to an arc chute for an electric circuit breaker and, more particularly. to an arc chute comprising metallic arc runners along which the terminals of the usual arc travel as the arc is driven into the chute.
  • glass-bonded mica has customarily been considered to be relatively nongas-evolving (see, for example, U.S. Pat. 2,761,934-Wood, lines l8-28, column 12) it appears that at these extreme high current levels, the arc will evolve sufficient gases from the glass-bonded mica to detrimentally affect the interrupting capacity.
  • the gases evolved from the glass-bonded mica contain low ionization potential components such as sodium and potassium.
  • an object of my invention is to increase the current interrupting capacity of an arc chute that comprises (l) are runners having a major portion of their surfaces of refractory metal and (2) face plates of glass-bonded mica or a similar material containing low ionization potential components.
  • Another object is to appreciably reduce the quantity of gases that will be evolved from such insulating face plates under extreme high current conditions, yet without impairing the ability of such face plates to maintain a high dielectric strength under conditions of high humidity and without significantly impairing the mechanical strength properties of the face plates.
  • an arc chute comprising arc runners each having a major portion of its arc-running surface of a refractory metal.
  • a pair of plates of low-gas-evolving insulating material are positioned on opposite sides of one of the runners between the runners and the adjacent insulating sidewalls of the arc chute.
  • These plates are of glass-bonded mica or a similar insulating material that is characterized by (l) a high surface resistivity under conditions of high humidity as compared to the material of the arc chutes sidewalls and (2) the inclusion of ingredients which decompose upon exposure to extreme high current arcs into low-ionization-potential metal vapors.
  • the arc-exposed regions of these plates are coated with a thermally-sprayed coating of a refractory ceramic insulating material such as alumina.
  • This coating acts as a shield between the arc and the base material of the plate which significantly reduces the amount of low-ionization-potential gases evolved from the base material.
  • FIG. I is a side elevational view, partly in section, showing an electric circuit breaker embodying one form of our invention.
  • FIG. 2 is a cross-sectional view taken along the line 2-2 of FIG. 1.
  • FIG. 3 is a sectional view taken along the line 3-3 of FIG. 1.
  • FIG. 4 is an enlarged view of a portion of FIG. 1.
  • FIG. 5 is a sectional view along the line 55 of FIG. 1.
  • the circuit breaker shown therein comprises a pair of terminal bushings l and 2, both of which are fixed in position relative to the supporting frame of the circuit breaker.
  • the bushing 2 comprises a downwardly extending conductive stud 3 at the lower end of which a movable conductive switch blade 4 is mounted by means of a fixed pivot 5.
  • the blade 4 carries suitable circuit-controlling contacts such as a current-carrying contact 6 and an arcing contact 7.
  • Bushing 1 comprises a conductive stud la to which a downwardly extending conductive member 8 is electrically connected. Attached to this conductive member 8 is a curved contact-retaining member 9 which coacts with the member 8 to form a holding pocket for receiving the anchored ends of main current-carrying contact fingers 10. These fingers 10 are pivotally mounted on a curved portion 12 of the conducting member 8 and are biased for limited rotative wiping movement in a closing direction by means of suitable compression springs 9a These compression springs 9a provide for highpressure circuit-closing engagement between the stationary current-carrying contact 10 and the movable current-carrying contact 6.
  • the movable arcing contact 7 cooperates with a stationary arcing contact 13, which is mechanically and electrically connected to the conducting member 8 by suitable clamping means 14.
  • the material of the arcing contacts 7 and 13 is capable of withstanding arcing and is also of a relatively high resistivity in comparison to the material of the current-carrying contacts 10 and 6. Accordingly, when the switch blade 4 is in the closed position shown, most of the circuit current flows through the current-carrying contacts. It is only when the switch blade 4 is driven counterclockwise to open the breaker that the arcing contacts carry appreciable current. During each opening action, the current-carrying contacts first part, thereby diverting current through the arcing contacts which are still in engagement due to their extensive wipe. Thereafter, the arcing contacts part and draw a circuit interrupting are which is driven into an arc chute 20 and there lengthened, cooled, and extinguished in a manner soon to be described.
  • a reciprocable operating rod 24 pivotally joined to the switch blade at 26 is provided.
  • This operating rod When this operating rod is driven upwardly, it acts to move the switch blade counterclockwise to effect a circuit interrupting operation.
  • the circuit can be reestablished simply by driving the operating rod downwardly to return the switch blade 4 in a clockwise direction to the closed position shown.
  • the operating rod 24, which is of insulating material, is actuated by means of a suitable conventional operating mechanism (not shown).
  • the arc chute assembly 20 comprises a pair of sidewalls 21 and 22 constructed of appropriate arc-resistance insulating material. These sidewalls are clamped together in spaced-apart relationship by suitable means, not shown.
  • Each sidewall preferably comprises ribs 23 projecting toward the other sidewall and arranged to mutually interleave with the corresponding projecting ribs on the other sidewall, thereby forming a sinuous or zigzag passage as viewed from the entrance end of the chute.
  • these ribs taper toward the entrance of the chute and thereby provide a throat portion through which the arc first passes before entering the zigzag passage between the ribs 23.
  • this construction is of the type disclosed in US. Pat. No. 2,293,5 l 3Linde, assigned to the assignee of the present invention. A position of the are as it moves into the chute is illustrated by the dotted line 29.
  • a pair of conductive arc runners 30 and 31 are provided along the upper and lower edges of the chute. As shown in FIG. 1, these runners 30 and 31 extend transversely to the path of the arc and in generally divergent relationship with respect to each other from the region in which the arc is initiated.
  • the upper arc runner 30 is made up of a plurality of segments 32, 33 and 34 disposed in end-to-end relationship, with the adjacent ends thereof separated by insulating spacers 36. Electrically bridging the spacer 36 nearest the arc-initiation region is a magnetic blowout coil 37 having one terminal connected to runner segment 32 adjacent the spacer 36 and its other terminal connected to runner segment 33 immediately adjacent this same spacer 36. The other spacers 36 is bridged by blow-out coil 38 connected between adjacent runner segments in a corresponding manner/The runner segment 32 located nearest the arc-initiation region is preferably of a generally U-shaped configuration and is electrically connected to the terminal stud la.
  • blowout coils 38, 37, 40 are connected in series-circuit relationship with each other as well as with the runner segments 32, 33, 34.
  • the lower arc runner 31 is constructed in substantially the same manner as the upper are runner 30.
  • the lower arc runner comprises a plurality of elongated segments 49, 50 and 51 disposed in end-to-end relationship and separated by insulating spacers52. Spacers 52 are respectively electrically bridged by blow-out coils 46 and 47 connected between the adjacent runner segments.
  • the runner segment 49 nearest the arc-initiation region is of a U-shaped configuration and is electrically connected to the terminal conductor 3 of the circuit breaker through blow out coil 45.
  • a conductive strap 56 is electrically connected between the terminal conductor 3 and one terminal of blowout coil 45, whereas the other terminal of the blowout coil 45 is connected to the innermost end of the runner segment'49.
  • An insulating spacer 57 is provided at the lower end of runner segment 49 to prevent the coil 45 from being short-circuited by the runner structure located across its tenninals.
  • each blow-out coil is provided with a centrally located core insulated from the coil and attached to pole pieces mounted on the outer surfaces of the sidewalls of the chute.
  • the coil 40 has a core 59 attached to pole pieces such as 61 shown by dotted lines in FIG. 1.
  • the coil 37 has a core 62 attached to similar pole pieces 63.
  • all of the other blowout coils have similar cores and pole pieces, only some of which are shown.
  • the movable switch blade 4 has swung rapidly away from the stationary contact 13.
  • the switch blade 4 moves downward into proximity with the runner segment 49 of the lower arc runner, the lower terminal of the arc transfers to the runner segment 49, thus inserting the lower blowout coil 45 in series with the arc.
  • the energized coil 45 immediately creates a magnetic blowout effect which drives the lower terminal of the are along the lower runner 31 toward the interior of the chute.
  • the lower terminal of the arc passes the first insulating spacer 52, it acts to insert the next blowout coil 46 in series with the arc and the first blowout coil 45 thereby providing increased magnetic force for driving the are into the chute.
  • the arc terminals move to the end of the runners before interruption is completed.
  • a pair of projecting electrodes 60 are provided at opposite sides of the movable arcing contact 7.
  • Each of these electrodes 60 is made of an arc-resistant material such as tungsten impregnated with copper or silver. The are that is drawn between contacts 7 and 13 upon arc separation strikes one of the electrodes, causing its upper terminal to attach thereto; and immediately thereafter the upper terminal moves toward the base of the electrode onto the runner segment 32.
  • runner 31 On opposite sides of the lower are runner 31 are a pair of face plates and 81 of a glass-bonded mica material, such as that sold under the trademark Mycalex. This material has an exceptionally high surface resistivity, which it is able to maintain despite conditions of high humidity in the surrounding air. As shown in FIG. 3, the face plates 80 and 81 are sandwiched between the lateral edges of the arc runner 31 and the sidewalls 21 and 22, respectively. These face plates extend along the runner 31 over substantially the entire length of the runner that is exposed to the are.
  • the material of the sidewalls 21 and 22 and ribs 23 is preferably a reaction product of asbestos and orthophosphoric acid (such as disclosed in US. Pat. 2,366,845-Brink and Arone, assigned to the assignee of the present invention) and containing a suitable inert filler such as zircon.
  • This material while excellent for arc-extinguishing purposes, has a lower surface resistivity than the Mycalex material, particularly under conditions of high humidity; and the are chute must rely upon the Mycalex face plates to assure against a dielectric breakdown along its walls in the region between the are runners 30 and 31 under high humidity conditions.
  • Each of the metal runner segments 32, 33, 34 and 49, 50, and 51 is preferably of brass but has its surface that is exposed to the are completely coated with a layer of refractory metal, e.g., tungsten, applied by plasma-arc spraying.
  • a layer of refractory metal e.g., tungsten
  • FIG. 4 shows the layer of refractory metal in more detail at 65. This layer is preferably of greater thickness in regions such as 69 and 70 where there is greater exposure to the arc.
  • a cross-sectional photomicrograph of the coating 83 shows that the coating is laminar in structure and is constituted by flattened interlocking particles of alumina.
  • the alumina coating increases the current interrupting capacity of the arc chute. It appears from these studies that, although the bare Mycalex material will evolve relatively little gas when exposed to a high current are, if the arc is of extreme high current, some of the Mycalex will decompose into vapors containing sodium and potassium. These vapors have a relatively low ionization potential, and any which are not condensed at current zero can be ionized by the high voltages then appearing to initiate a dielectric breakdown.
  • the alumina coating is to 25 mils in thickness.
  • the refractory metal coating on the arc runners and 31 plays an important role in enabling the alumina on the face plates 80 and 81 to make its contribution to increased interrupting capacity.
  • the glass-bonded mica even if uncoated and exposed to the arc, will evolve so little glass that its presence does not appear to detract from the current interrupting capacity of the chute.
  • the refractory metal coating on the arc runners enables higher currents to be interrupted by the arc chute, i.e., currents above 25,000 amperes, r.m.s.; and it is only when such higher currents are being interrupted that the glass-bonded mica, if uncoated and exposed to the arc, would evolve a quantity of vapors sufficient to detract from interrupting ability. It is under these particular high-current conditions that the alumina coating acts to effectively prevent vaporization of the glass-bonded mica into low ionization potential vapors.
  • low-ionization potential we mean a first ionization potential under 5.5 electron volts.
  • the plasma-arc sprayed alumina coating 83 that we apply to the glass bonded mica does not significantly detract from these very desirable properties of the glassbonded mica but does significantly improve the performance of the glass-bonded mica under extreme high-current arcing conditions as was explained hcreinabove.
  • the plasma-arc sprayed alumina coating has a surface resistivit much higher t an the material of the arc-chute sidewalls, an this high surface resistivity is maintained under high humidity conditions,
  • the coated face plates to function in the same way as the bare face plates in preventing dielectric breakdowns.
  • the glass-bonded micaevolves relatively little gas under high-current conditions, particularly when it is shielded by the alumina coating, the alumina coating is able to remain tightly bonded thereto despite exposure to high-current arcing. This would not be the case with a base material such as the phosphoasbestos material of the arc-chute sidewalls, which evolves much greater quantities of gas when exposed to the temperatures produced by a high-current arc.
  • An electric circuit breaker comprising an arc chute into which an arc is adapted to be driven for the purpose of extinguishing the are, said are chute comprising:
  • said runners having refractory metal surfaces along a major portion of the paths traveled by said are tenninals during circuit interruption;
  • a pair of face plates of low-gas-evolving insulating material positioned on opposite sides of one of said runners between said runners and said insulating sidewalls, said plates being of a second insulating material that has a much greater surface resistivity under humid conditions than the material of said insulating sidewalls;
  • said second insulating material containing one or more low ionization potential metallic components that will vaporize at temperatures produced at the surface of said plates by arcs on said one runner carrying high currents within the current interrupting rating of said circuit breaker, assuming said plate surface was bare;
  • circuit breaker of claim 1 in which said refractory metal surface is constituted by thermally sprayed refractory metal.
  • circuit breaker of claim 1 in which said first insulating material is a phosphoric acid-asbestos material, said second insulating material is a glass-bonded mica material, and said refractory ceramic insulating material comprises alumina.
  • circuit breaker of claim 4 in which said coating of alumina has a thickness of at least 20 mils.

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  • Arc-Extinguishing Devices That Are Switches (AREA)
  • Coating By Spraying Or Casting (AREA)
US827583A 1969-05-26 1969-05-26 Arc chute for an electric cuircuit breaker Expired - Lifetime US3560685A (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3735074A (en) * 1971-07-14 1973-05-22 Gen Electric Arc chute for an electric circuit breaker
US3818165A (en) * 1972-06-09 1974-06-18 Gen Electric Electric circuit interrupter
DE102017125685A1 (de) * 2017-11-03 2019-05-09 Schaltbau Gmbh Schaltgerät mit Lichtbogenlöscheinrichtung und Lichtbogenführung

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1915969A (en) * 1930-11-19 1933-06-27 Gen Electric Electrical arc resistant material
US2366485A (en) * 1941-12-18 1945-01-02 Gen Electric Inorganic molding compositions and products produced therefrom
US2645693A (en) * 1949-09-13 1953-07-14 Fed Electric Prod Co Molded casing for electrical apparatus
US2761934A (en) * 1952-09-04 1956-09-04 Ite Circuit Breaker Ltd High voltage circuit breakers
US2911505A (en) * 1955-11-04 1959-11-03 Reyrolle A & Co Ltd Arc chutes
US3009041A (en) * 1959-09-25 1961-11-14 Gen Electric Arc-extinguishing device for direct current arcs

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1915969A (en) * 1930-11-19 1933-06-27 Gen Electric Electrical arc resistant material
US2366485A (en) * 1941-12-18 1945-01-02 Gen Electric Inorganic molding compositions and products produced therefrom
US2645693A (en) * 1949-09-13 1953-07-14 Fed Electric Prod Co Molded casing for electrical apparatus
US2761934A (en) * 1952-09-04 1956-09-04 Ite Circuit Breaker Ltd High voltage circuit breakers
US2911505A (en) * 1955-11-04 1959-11-03 Reyrolle A & Co Ltd Arc chutes
US3009041A (en) * 1959-09-25 1961-11-14 Gen Electric Arc-extinguishing device for direct current arcs

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3735074A (en) * 1971-07-14 1973-05-22 Gen Electric Arc chute for an electric circuit breaker
US3818165A (en) * 1972-06-09 1974-06-18 Gen Electric Electric circuit interrupter
DE102017125685A1 (de) * 2017-11-03 2019-05-09 Schaltbau Gmbh Schaltgerät mit Lichtbogenlöscheinrichtung und Lichtbogenführung
US10692671B2 (en) 2017-11-03 2020-06-23 Schaltbau Gmbh Switching device with arc extinguishing device and arc guide

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ES377969A1 (es) 1972-06-16

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