US2249499A - Electric circuit interrupter - Google Patents

Description

July 15, 1941. .1. w. SEAMAN ELECTRIC CIRCUIT INTERRUI TER Inven r. \Toa p V\/.Se nfina is Att ney Patented July 15, 1941 UNITED STATES PATENT OFFICE ELECTRIC CIRCUIT INTERRUPTEB Joseph W. Seaman, Upper Darby, Pa., assignor to General Electric Company, a corporation of New York Application December 2, 1938, Serial No. 243,587

Claims. (Cl. 200-144) My invention relates to electric circuit interrupters, more particularly to air circuit interrupters of the type wherein the arc is to be interrupted within confining or partially confining means, such as an arc chute, and has for its principal object the provision in an air circuit interrupter of the character above deiined of improved arc-interrupting means that is effective rapidly to extinguish a high voltage power are within a comparatively small space, and to confine under all operating conditions the are within this space.

The use in arc chutes of arc cooling and quenching structures, such as metal or insulating plates, between which the arc is driven, and spaced metal pins or bars positioned transversely of the arc path is known in the air circuit breaker art. In a well-known form, a circuit breaker of the magnetic blow-out type is provided with a plurality of spaced metal plates within an arc chute arranged so that the arc, as it is driven into the plates by the blow-out field, is divided into a plurality of serially related sections.

It has also been proposed to use in the arc chute spaced metal pins or bars for the purpose of cooling and quenching the arc. The design factors, however, have not been clearly understood, particularly with respect to the spacing and arrangement of the arc-quenching elements, with the result that are interruption has not been reasonably consistent except in the case of spacious arc chutes having a large aggregate mass of cooling material.

I have found that in the case of spaced metal elements, such as pins or bars, there is an optimum for the relative spacing of these elements within the arc chute, regardless of both the aggregate mass of cooling metal within the chute and the magnitude of the current to be interrupted. This optimum spacing results in a compact and efilcient arc chute for a given interrupting rating. Specifically, I have found that pins composed of a suitable non-magnetic metal, such as copper for example, positioned transversely of the arc path between the insulating walls of an arc chute aremost eifective for are interruption when spaced approximately from each other, the spacing being between adjacent pin arcing surfaces as contrasted with pin centers. A tolerance of plus or minus is within the scope of my invention, although the fa" spacing is preferred. I

I have also found that an arc chute provided with arc-extinguishing structure of the charatcer above described can also be made even more effective and compact by the use of an insulating arc baiile structure at the exhaust end of the chute. The baille structure is made up of baille plates spaced so as to form a plurality of approximately parallel narrow slots each approximately V." in width extending substantially parallel to the arc path. These slots are effective not only as an aid in extinguishing the arc in case it is driven through the main arc extinguishing means, but also to prevent extension of the arc exteriorly of the chute. The slots however provide free venting of the arc gases within the chute.

My invention will be more fully set forth in the following description referring to the accompanying drawing, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

Referring to the drawing, Fig. 1 is an elevational view, partly in section, of the essential portion of an air circuit breaker embodying the present invention; Fig. 2 is an end viewof the circuit breaker structure shown by Fig. l, and Fig. 3 is an enlargeddetail view of the arc interrupting structure.

' carried on a operating arm 6 that is secured to an insulating shaft 1 for rotative movement therein and has a resilient connection at 6' with the main operating arm for permitting limited overtravel or "wipe when the contacts are closed.

The arc-extinguishing structure or are chute 3 comprises in the present instance a pair of spaced insulating plates 8 composed of asbestos board or the like forming an arc chamber that is adapted at its lower end to receive the arc and to vent the are gases at the upper or exhaust end. The are chute is substantially closed at one side by the arcing horn I and an insulating spacing and supporting member 9 secured to the support or panel 4. and at the opposite side by the arcing horn 2'. As illustrated, the arcing horn I forms part of the fixed contact structure and is secured in position by the terminal conductor 5. The arcing horn 2 is secured between the insulating plates 8 by an insulating spacing member 10. The arc chute so far described is of a more or less conventional design, the arc formed between the contacts I and 2 being blown by a magnetic field, for example, into .the arc chute along the arcing horns I and 2 so that the arc is greatly lengthened and cooled.

For the purpose of greatly increasing the interrupting capacity and efilciency of the arc chute, a compactly arranged group of spaced metal elements, such as copper pins H, are mounted between the plates 8 so that the pins extend preferably in staggered rows as shown transversely of the arc. As previously stated, the copper pins are preferably spaced from each other approximately 3 3" with respect to the adjacent arcing surfaces of the pins. That is, the outer cylindrical surfaces of the pins are spaced approximately from each other throughout the arc chute. The theoretical reasons for this precise spacing are not believed necessary for a clear understanding of the invention' as it has been definitely proved that improved interrupting action takes place when the pins so spaced. It is of particular importance to note that this spacing is substantially independent of the magnitude of the current to be interrupted and also of the exact number of plus within the chute, assuming, of course that there is sufiicient mass of metal within the chute "to dissipate the initial heat of the are so that the pins are not vaporized greatly. The spacing is also substantially independent of the voltage impressed across the circuit breaker terminals, a ough it ould be understood that for high voltagm an ease ill size of the arc chute structure is nose Under non" interrupting conditions the arc enters the chute along the arcing horns i and 2' and is split up as it moves among the pins so that extinction generally occurs well within the chute. In the case of heavy overloads or short circuits, the arc may be driven toward the exhaust or upper end of the chute. In such cases have found that spaced parallel insulating baffles 52 arranged to form a plurality of narrow slots are effective to maintain the arc within the chute and also to cause final extinction. The

- narrow slots, although very effective to prevent extension of the arc exteriorly of the arc chute, provide sufficient exhaust area openings to permit free venting of the arc gases formed within the chute.

As shown, the insulating bafiles 12 comprise a plurality of arcuate strips of suitable arc resisting insulating material, such as asbestos board or the like clamped between the upper edges of the plates 8 by means oi through bolts l3 and insulating spacers i4. tend throu hout the length of the exhaust end of the chu e, The slots so formed are preferably in width or less as I have found that a number of narrow slots having a sufllciently large aggrega e exhaust gas venting area are most effective in maintaining the are within the chute and aiding are extinction. If desired, an integral moulded bafile structure can be used.

An air circuit breaker constructed as above described is compact in size as compared with air circuit breakers of similar rating having the conventional type of arc chutes. Furthermore, arc interruption is more consistent and the duration of arcing is considerably less.

The are can be driven into the arc chut y The bailles preferably exfrom the arcing horns.

conventional magnetic blow-out means, although in the present instance I have shown a magnetic structure associated with each of the contacts for initiating movement of the are along the arcing horns into the chute. This magnetic structure comprises a pair of yokes I5 and I6 composed of iron or other suitable magnetic material. The yokes are secured, as illustrated, to the contacts so that the open ends face each other in a position offset with respect to the point of contact engagement so as to be more remote That is, the iron yokes are mounted somewhat beneath the point of engagement between contacts i and 2 so that there will be present upon separation of the contacts a magnetic flux tending to drive the arc into the arc chute. The arcing horn 2 and the movable contact 2 are connected as in the usual case through flexible conductors i3 to the other terminal of the circuit breaker (not shown).

It has been found that in severe are interarrangement the ends of the pins seat within cylindrical recesses at i8, each cylindrical recess being countersunk as at [9 to form a conical recess so that the pins are spaced from that part of the wall insulation that is flush with the inner sides of the chute. This arrangement serves effectively to prevent excess fusing of the pin metal at the side walls of the chute. An alternate arrangement consists in turning down the ends of each pin a certain distance so as to increase the spacing between the pins where they are in contact with the side walls of the arc cnute.

It should be understood that my invention is not l mited to specific details of construction and arrangement thereof herein illustrated, and that changes and modifications may occur to one skilled inthe art without departing from the spirit of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electric circuit interrupter having arcforming means and an arc chute for receiving the arc comprising spaced insulating side walls and a compactly arranged group of metal pins mounted between said insulating walls transversely of the arc, the adjacent arcing surfaces of said pins throughout said chute being spaced substantially uniformly from each other approximately 1%".

2. An electric air circuit interrupter having arc-forming means and an arc chute for receiving the arc comprising spaced insulating walls open at one end for venting the arc gases, a compact oup of metal pins mounted within said chute between said walls in substantially uniformly spaced relation to extend transversely of the arc path, the spacing of said pins from each other at the arcing surfaces thereof being approximately and insulating baffle structure disposed beyond said pins at the exhaust end of said chute, said baille structure forming a plurality of narrow slots not exceeding ,4," in width parallel to the are for confining said are within a d chute.

3. In an electric air circuit interrupter having arc-forming means, an arc chute comprising a pair of spaced insulating walls and a plurality of metal pins mounted in said plates so as to extend between said walls, the ends of said pins being mounted within conical shape recesses in said insulating Walls for minimizing fusing of the pin metal at said walls.

4. In an electric air circuit interrupter having arc-forming means, an arc chute comprising a pair of spaced insulating walls and a plurality of metal pins mounted in said plates so as to extend between said walls, the ends of said pins "being mounted within enlarged recesses in said insulating walls whereby the insulation of said walls in flush alinement with the inner sides of I said chute is spaced from said pins.

between said walls, the metal adjacent to the ends of said pins subject to arcingbeing spaced with respect to the insulation surfaces of said walls for minimizing fusing of the pin metal at said walls.

JOSEPH W. SEAMAN.

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