US3327080A - Arc chute for electric circuit breaker - Google Patents

Description

G. J. MErNDl-:Rs 3,327,080

ARC CHUTE FOR ELECTRIC CIRCUIT BREAKER 23, 1964 2 Sheets-Sheet l June 20, 1967 Filed Dec.

/l fff/f////f///////////////M/J/f/ June 20, 1967 G. J. MEINDERS l3,327,080

ARC CHUTE FOR ELECTRIC CIRCUIT BREAKER 2 Sheets-Sheet 2 Filed Dec. 25, 1964 cgt@ /l United States Patent O 3,327,080 ARC CHUTE FOR ELECTRIC CiRCUlT BREAKER Gerardus J. Meinders, Walpole, Mass., assignor to Allis- Chalmers Manufacturing Company, Milwaukee, Wis. Filed Dec. 23, 1964, Ser. No. 420,746 Z Claims. (Cl. 200-144) ABSTRACT F THE DISCLSURE An arc chute comprises a pair of vertical spaced apart insulating Walls between which a stack of spaced apart metal plates slotted in their lower edges are arranged in two groups. A pair of arc runners extend into the chute at each end of the stack of plates. The arc chute is disposed above a pair of separable contacts which are nearer to one end of the stack of plates than to the other. A iirst insulating plate is located between the one end of the stack and its associated arc runner. A second insulating plate is located between the two groups of metal plates. They first and second insulating plates overlap the uppermost portions of the metal plates. In one embodiment of the invention, additional insulating plates are in edgewise association with certain of the metal plates. In the other embodiment of the invention, additional insulating plates are in edgewise association with all of the metal plates.

In both embodiments of the invention, there are hollow baille members transversely arranged between the insulating side walls and between each adjacent pair of insulating plates;

This invention relates generally to arc chutes for electric circuit breakers and, particularly, to those which employ a plurality of spaced -apart metal plates to divide up an arc into smaller segments during extinguishment.

Some circuit breakers for interrupting alternating current use an arc chute which comprises a stack of spaced apart metal plates located between a pair of arc runners and adjacent the circuit breaker contacts. Such arc chutes operate on the principle of dividing the long arc across the runners into a multiplicity of series connected smaller arcs as it moves through the are chute; the object being to raise the reignition voltage of the arc to a level which permanently exceeds the recovery voltage. Extinguishment is aided by the cooling of the small arc in contact with the metal plates and -by the turbulence present as the arc move through the slots between the metal plates.

To prevent the arc from reigniting after passing through the stack of plates, it has been the practice to place insulating plates in coplanar edgewise relationship with the top edge of some or all of the metal plates. However, in order for this to be completely effective there must be a close tolerance t between the edges of the metal plates and 'the insulating plates. Insulating plates have also been interspersed between the metal plates to aid arc extinguishment by providing a more tortuous path for the arc. In any event, the use of insulating plates in various arrangements with metal plates to aid in arc extinguishment, while achieving the desired electrical result, has resulted in more Vcostly and complicated arc chutes. `It is desirable, therefore, to provide new and improved arc chutes wherein the metal plates and insulating plates are arranged so as :to improve'the extinguishing ability of the arc chute while at the same time reducing the number of parts otherwise required and simplifying manufacturing operations.

The present invention contemplates an arc chute wherein a stack or plurality of spaced apart metal plates are disposed between a pair of arc runners and wherein one end of the stack of plates is relatively closer to the arc initiating separable contacts than the other end. It has been discovered that in such an arc chute the arc is most powerful and arc by-products are most numerous near the end of the stack of metal plates closest to the point where the arc is initiated. Consequently, after the arc has moved through the stack, flashover or reignition of the arc is more likely at that end of the stack than at the other end. In accordance with the present invention, then, it is proposed to insert insulating plates between metal plates near the said one end of the stack to prevent flashover and to increase the length of the arc path but to use insulating plates in conjunction with the rest of the stack only insofar as necessary in 4order that as many metal plates as possible can be retained in the stack to give the voltage drop necessary to provide higher are voltage.

It is an object of the present invention to provide an improved arc chute which employs a combination of metal plates and insulating plates to effect arc extinguishment and prevent restriking of t-he arc.

Another object is to provide an arc chute of the aforesaid character which provides an elongated path for the arc and inhibits restriking of the arc across the top of the metal plates.

Another object is to provide an arc chute which does not require close tolerance fitting between constituent elements to effect eliicient arc extinguishment.

Another object is to provide an arc chute of the foresaid c-haracter which is economical to fabricate and reliable in use.

Other objects and advantages will hereinafter appear.

The 'accompanying drawings illustrate several preferred embodiments of the invention but it is to be understood that the embodiments illustrated are susceptible of modications with respect to details thereof without departing from the scope of the appended claims.

In the drawings:

FIG. 1 is a side elevational view, partly in section, of a portion of a circuit breaker employing an arc chute incorporating the present invention;

FIG. 2 is a View taken along line II-II of FIG. 1;

FIG. 3 is a view similar to that in FIG. 1 but showing a second embodiment of the invention; and

FIG. 4 is a view taken along line IV-IV of FIG. 3;

Referring now to FIGS. 1 and 2 of the drawings, the numerals 10 and 12 designate a stationary and movable contact, respectively, of an electric circuit breaker which separate to establish an arc. An arc chute 14 is associated with contacts 10 and 12. Arc chute 14 comprises a pair o-f spaced apart side walls 16 and 18 which are made of electrical insulating material such as ceramic, fiber, or the like. It is to be understood that the side walls 16 and 18 are mirror images of each other and are formed with suitable projections and recesses to support various components therein when the side walls are fastened together. The side walls 16 and 13 define an arcing chamber 20 in the lower portion of arc chute 14 wherein stationary contact 10 and movable contact `12 are disposed.` Stationary contact 10 is rigidly mounted with respect to arc chute 14 and is located at one end of chamber 20. Stationary contact 10 is electrically connected to a rst stationary electrically conductive arc runner 22 which is also located at the aforesaid one end of chamber 20 of arc chute 14. Movable contact 12 is pivotally mounted for clockwise and counterclockwise movement (with respect to FIG. 1) within chamber20 of arc chute 14 into and out of engagement, respectively, with stationary contact 10. When movable contact 12 is moved counterclockwise it comes into proximity with a second stationary electrically conductive arc runner 24 which is located at the other end of chamber 20' of arc chute 14 and spaced apart from arc runner 22. During circuit interruption, an arc established between the contacts and 12 is transferred therefrom so that it becomes established between the arc runners 22 and 2'4 and travels upward thereon, as hereinafter explained.

Arc chute 14 comprises a stack of metal plates 26 which span the side walls 16 and 18 above chamber 20 and are disposed in spa-ced apart relationship between the arc runners 22 and 24. One end of the stack of metal plates 26 is closer to the contacts than the other end.

All plates 26 are of the same shape and size and may be assume-d to be made of copper plated steel. The plates 26 are arranged with respect to each other so that the upper edge of each plate or the edge most remote from the contacts terminates in a first common horizontal plane. The upper edges of the arc runners 22 and 24 also terminate in or below the irst plane. The lower edge of each plate 26 or the edge facing the contacts terminates in a second common horizontal plane. The plates 26 are held in position by entrapment in grooves 30 provided in the side walls 16 and 18. Each plate 26 is provided with a triangular slot 28 at its lower edge to guide the arc into the stack of plates during operation.

In accordance with the invention, a first insulating platte 32, rectangular in shape, is located between arc runner 22 and the metal plate 26 nearest to arc runner 22. Insulating plate 32 which is` understood to be made of fiber type insulating material, is arranged so as to be in overlapping relationship with a substantial part of the uppermost portion of its associated metal plate 26. Insulating plate 32 has a straight lower edge 34 which lies well above the apex of slot 28 in its associated metal plate 26. The'upper portion of insulating plate 32 extends well above the rst plane in which the top edges of the metal plates 26 lie.

A second insulating plate 36, similar in size, shape and insulating properties to insulating plate 32, is located between a pair of metal plates 26 in overlapping relationship with a substantial part of the uppermost portion of each of the two adjacent metal plates and extends well above their upper edges. Insulating plate 36 has a straight lower edge 38 which lies above the apex of the notch 28 in its two associated metal plates 26. In the embodiment shown, there are three metal plates 26- intervening between the insulating plates 32 and 36 but a greater or lesser number of plates could intervene provided that insulating plate 36 is ultimately located relatively nearer to the end of the stack of metal plates 26 closest to the contacts 10 and 12 Ibetween which the arc is initiated.

Since the insulating plates 32 and 36 do not extend to the bottom of the stack of plates 26, an arccan enter the stack and become established therein as a series of smaller arcs before it hits the bottom edge of either insulating plate. Furthermore, since the insulating plates 32 and36 transect the plane in which the top edges of the metal plates 26 lie and extend for a substantial distance on either side of this plane, iiashover of the arc at this end of the stack is effectively prevented. The arrangement of insulating plates 32 and 36 also requires a more tortuous path for the arc as it meets the lower edges of those plates and begins to move up the stack.

Arc chute 14 further comprises a plurality of insulating plates such as 40' which are disposed in edgewise association with the remote edges of at least some of the metal plates 26 which are farthest from the contacts 10 and 12. The plates 40 inhibit tiashover of the arc at the end of the stack remote from the contacts but need not be in close tolerance tit with their associated metal plates because the flashover tendency is substantially reduced by the insulating plates 32 and 36.

Arc chute 14 is provided with means for cooling the exhaust gases expelled from the top of the stack of plates 26. Such means take the form of hollow battle members 42 which are supported lby perforated insulating members 44.

. FIGS. 3 and 4 show another embodiment of the invention. An arc chute 46 shown in FIGS. 3 and 4 is similar to the arc chute 14 hereinbefore described except that it is provided with a plurality of insulating plates 48 and 50 which are disposed in edgewise association with the remote edges of every metal plate 26a in arc chute 46. The modification disclosed in FIGS. 3 and 4 enables arc chute 46 to interrupt more powerful arcs than arc chute 14.

Arc chute 14 operates as follows. Assume that the contacts 10 and 12 of the circuit breaker are closed and that current is flowing therethrough. As movable contact 12 is moved counterclockwise (with respect to FIG. l) from closed toward open position, an arc appears between contacts 10 and 12. Because of electromagnetic forces present, the terminal point of the arc on contact 10 then transfers to arc runner 22 and the terminal point of the arc on contact 12 moves to the extreme tip of contact 12 and the arc forms an inverted U-shape with its highest point entering within the slots 28 in those metal plates 26 at the end of the stack nearest arc runner 22. As movable contact 12 moves closer to arc runner 24, the arc terminal on the form transfers to the latter, and an elongated arc is established between the arc runners 22 and 24. As the elongated arc moves up through and past the slots 28 in the stack of metal plates 26, it is divided into a plurality of small arcs which are in series with each other. The small arcs tend to move upward through the stack at a relatively uniform rate. However, as the small arc between the plates 26 on either side of insulating plate 36 hits edge 38 thereo-f, its upward travel is slowed down. The same effect occurs as the small arc between arc runner 22 and plate 26 on the opposite side of insulating plate 32 hits edge 34 of plate 32. This slowing down of the arc at two points has the effect of elongating the arc and increasing its voltage. As the arc moves further through the stack itl is prevented from flashing over the top edges of the metal plates 26 in the stack by the insulating plates 3-2v and 36 and by the insulating plates 40'. As hereinbefore noted, the arcing forces and arc Iby-products are most numerous at the end of the arc chute nearest stationary contact 10 (i.e., the point of arc initiation) and the insulating plates 32 and 36 are disposed in this region to be most effective. Since the arcing forces and lay-products are lessl effective at the opposite end of the stack, the insulating plates 40 are suicient to reduce the likelihood of ashover across the top of the metal plates. As previously mentioned, it is desirable to retain as many metal plates as possible in Vthe stack in order to increase the arc voltage. Exhaust products from the arc are cooled and condensed by means of the baffles 42 before being expelled from the arc chute.

Arc chute 46 shown in FIGS. 3 and 4 operates in the same manner as arc chute 14 but, since it is intended to handle a more powerful arc, it is provided with the insulating plates 48 and 50 which effectively aid the longer insulating plates in` preventing flashover.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined aS follows:

1. In combination, a pair of contacts between which an arc is established upon separation, a pair of spaced apart arc runners to which said arc is transferred from said contacts, a stack of spaced apart metal plates ar'- ranged in two 4groups and located between said pair of varc runners and having one of its ends nearer to said contacts than the other, each metal plate having an edge near to and another edge remote from said contacts, said remote edge of said metal plates terminating in a first common plane and said near edge of said metal plates terminating in a second common plane, said near edge being provided with a slot, the end of at least one of said arc runners terminating between said rst and second common planes, a first insulating plate located between said one end of` said stack andits associated arc runner, a second insulating plate located between said two groups of metal plates, said rst and second insulating plates being in overlapping relationship with the uppermost portions of the adjacent metal plates and extending through and beyond said rst common plane, said rst and second insulating plates having no metal plates in edge Wise association therewith, a plurali-ty of other insulating plates in edgewise association with the remote edge of at least some of the metal plates in said stack and hollow baffle members disposed between each pair of adjacent insulating plates above sa-id rst 10 3,031552 common plane.

2. The combination according to claim 1 including a plurality of other insulating plates in edgewise association with the remote edge of all of the metal plates in said stack.

References Cited UNITED STATES PATENTS 2,215,797 9/1940 Sauer 200-147 2,734,970 2/1956 Spears ZOO-147 2,908,787 10/ 1959 Scully 20G-144 4/ 19162 Stewart a.. 20G-144 ROBERT S. MACON, Primary Examiner.

Claims (1)

1. IN COMBINATION, A PAIR OF CONTACTS BETWEEN WHICH AN ARC IS ESTABLISHED UPON SEPARATION, A PAIR OF SPACED APART ARC RUNNERS TO WHICH SAID ARC IS TRANSFERRED FROM SAID CONTACTS, A STACK OF SPACED APART METAL PLATES ARRANGED IN TWO GROUPS AND LOCATED BETWEEN SAID PAIR OF ARC RUNNERS AND HAVING ONE OF ITS ENDS NEARER TO SAID CONTACTS THAN THE OTHER, EACH METAL PLATE HAVING AN EDGE NEAR TO AND ANOTHER EDGE REMOTE FROM SAID CONTACTS, SAID REMOTE EDGE OF SAID METAL PLATES TERMINATING IN A FIRST COMMON PLANE AND SAID NEAR EDGE OF SAID METAL PLATES TERMINATING IN A SECOND COMMON PLANE, SAID NEAR EDGE BEING PROVIDED WITH A SLOT, THE END OF AT LEAST ONE OF SAID ARC RUNNERS TERMINATING BETWEEN SAID FIRST AND SECOND COMMON PLANES, A FIRST INSULATING PLATE LOCATED BETWEEN SAID ONE END OF SAID STACK AND ITS ASSOCIATED ARC RUNNER, A SECOND INSULATING PLATE LOCATED BETWEEN SAID TWO GROUPS OF METAL PLATES, SAID FIRST AND SECOND INSULATING PLATES BEING IN OVERLAPPING RELATIONSHIP WITH THE UPPERMOST PORTIONS OF THE ADJACENT METAL PLATES AND EXTENDING THROUGH AND BEYOND SAID FIRST COMMON PLANE,

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