US2836683A - Arc-extinction casing for circuit-breaker - Google Patents

Description

May 27, 1958 A. A. H. soUcHET 2,336,683

ARC-EXTINCTION CASING FOR CIRCUIT-BREAKER Filed Feb. 28, 1956 United States Patent ARC-EXTINCTION CASING FOR CmCUIT-BREAKER Andr A. H. Souchet, Nanterre, France, assignor to La Telemecanique Electrique (Societe Anonyme), Nanterre, France, a company of France Application February 28, 1956, Serial No. 568,311 Claims priority, application France August 29, 1955 1 Claim. (Cl. 20G-144) It is known that, in current-breaking devices and especially in those which have a protective function and are intended to break currents of very high value (shortcir-cuits), it is necessary to provide devices for extinguishing the are which is struck between the contacts which are in the process of separating.

This extinction is generally effected by blowing the arc, either magnetically or by compressed air, within the interior of a casing which surrounds the contacts. These casings are sometimesy formed by pole plates between which the blowing device lengthens the arc by incurving it until it is extinguished.

In the arc-blowing casings of known construction, the arcs which are produced at the moment of the breaks give rise to llames which pass outside the casing and are liable to reach the metallic parts located in the vicinity. In this way there may be produced destructive arcs which are liable to produce, by short-circuit, melting of the conductive members of the apparatus.

It thus becomes essential to leave large air spaces, known as safety perimeters between the casings of the circuit-breaker apparatus and the metallic casings in which they are housed. In the same way, in order to prevent arcing between adjacent poles, it is necessary to locate the poles at fairly large distances from each other.

The present invention has for its object a blowing casing in which the rupture of the electric current is obtained with practically no external sign of its occurrence. In a casing of this kind, the flames of the arc are prevented from passing out of the casing; the casing however enables the gases heated by the flames to be evacuated.

In accordance with the invention, the casing is formed by a portion in the shape of a convergent nozzle which encloses the contacts, this nozzle opening through a narrow passages into an expansion chamber which communicates with the exterior. Preferably, and in known manner, the portion in the form of a nozzle is divided into compartments by means of fins orientated in the general direction of the nozzle, these tins tending to split up the arcs and cool the gases produced by the arcs.

In an advantageous form of construction, the nozzle and the expansion chamber have a common wall and the communicating passage between these two spaces is delimited between the edge of this common wall and a partition which is substantially at right angles to the said wall, and which forms at the same time the space of the nozzle and that of the expansion chamber.

This arrangement has a two-fold advantage; on the one hand the choice of the position of the partition with respect to the common wall enables the dimensions of the narrow passage to be regulated, and on the other hand, the gases passing out of the nozzle are slowed down by their contact with the partition and they pass into the expansion chamber in a direction which is practically opposite to that of their passage out of the nozzle.

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This passage in the form of a baffle assists the effect of cooling and of slowing down of the gases.

The casing is preferably formed by two pole plates having the general shape of quarters of a circle, coupled at their periphery by a partition, the pole plates being hollowed out, on the one hand internally so as to form a flattened nozzle when they are brought together and on the other hand, in the thickness of these pole plates,`on each side of the said flattened nozzle, so as to form the expansion chambers.

The description which follows below with regard to the attached drawings (which are given by way of example only and not in any sense by way of limitation) will make it quite clear how the invention may be carried into effect, the special features which are brought out, either in the drawings or in the text, being understood to form a part of the said invention:

Fig. l shows in cross-section, following the line I--I of Fig. 2, an arc-extinction casing improved in accordance with the invention. Y

Fig. 2 is a cross-section taken along the line II-II of Fig. l.

Fig. 3 shows a cross-section, similar to that of Fig. 2, of an alternative form of embodiment.

In the device shown in these figures, the current reaches the incurved xed contact 1 through a metallic winding 2 which is intended to create a magnetic field which ensures the extinction of the arc. This eld is guided along a core 14 of magnetic metal, which assembles together the magnetic pole plates 12 held in place by the. insulating cross-member I3 in the form of a reel. In the case of high nominal current values, this winding may be reduced simply to a bar which passes through and which is sufficient to create the necessary magnetic field.

With the contact 1 co-operates the moving contact 3 which can pass from the position shown in full lines (closed position) to the open position 3a shown in dotted lines. When the contacts are opened, the arc which is struck between the contacts 1 and 3 moves along these contacts towards the exterior and extends in a curve under the effect of the magnetic field. This arc is thus developed between the insulating jaws 4, which have the general shape of a quarter of a circle, of the arc casing. These jaws are hollowed-out internally so as to form a kind of convergent attened nozzle 5 which is directed towards the periphery of the casing. In the narrower portion of the nozzle are arranged the fins or blades 6, the general direction of which is radial. These tins may be fitted into slots formed in the pole plates. The pole plates are connected together by an incurved partition 7 of insulating material, which is fitted into oppositelydisposed slots in the pole plates, and which practically closes the casing, with the exception of the small spaces 8 formed between the partition 7 and the edge 9 of the peripheries of the pole plates which constitute the extremity of the nozzle 5.

In the jaws 4 are formed hollow spaces 10 which, with the partition 7, form expansion chambers which communicate with the nozzle through the spaces 8. Towards the top of the casing, there is a gap in the partition 7, so that the spaces 10 of the jaws communicate with the exterior through the openings 11.

The device which has just been described operates in the following manner:

The gases heated inside the casing by the arc, as it curves outwards, are increased in speed by the convergent nozzle 5 and are thus led into the narrow part of this nozzle. When the arc comes into contact with the fins 6, it becomes split up by these fins and the small sections of arc are extinguished in each of the compartments which are formed by the lins. In effect, by reason of the presence of the partition 7, there is produced a pressure of gas towards the extremity of the paths followed by the arc elements, and this pressure assists the rupturing power since the dielectric rigidity of ther air increases with pressure. The hotgasespass through the narrow spaces@ which draw Ythem out and give -them a curved trajectory, so that the gases'are very powerfully cooled during this passage. The gases then expand into the chambers 10 andvthis still further accentuates the cooling effect. From the chambers '10, the gases, escape to the exterior, either 'through 'the open-r ings 11 which can be directed in such manner that the gases cannot in any event be dangerous, or through the base of the casing where the chambers `10 may not be entirely closed.

.,'The dimensions of the spaces 8 canv be fixed by experiment in accordance with the values of current to be broken. In fact, if these spaces 3 are too great, the effect of gas pressure which contributes to the extinction kof the arcs is not obtained, and ames may pass out through the openings of the chambers 1t), whilst if these spaces are too small, the gas pressure obtained at the extremities of the nozzle maybe excessive so that 'the arcs are forcedback, and this may give rise to .the production of fresh arcs on the contacts which are in course of separation, resulting lin 'damage to the contact surfaces.

In order to simplify the construction, as shown in Fig. 3, the partition 7 may have a U-section which encloses the section of the casing. ln this case, the hollow spaces 10 are formed on the external faces of the cheeks.

It will of course be understood that modifications may bemade to the forms of embodiment which havebeen described above, in particular by the substitution of equivalent technical means Without thereby departing 'from the spirit or from the scope of the present invention.

What I claim is: f

In combination with a circuit-breaker having sep- 4 l arable contact members liable to give rise to an arc upon separation thereof, an arc-extinction device comprising a attened chamber in which said contact members are housed, a at convergent nozzle communicating with said chamber and forming an extension thereof, and a wall extending opposite the discharge end of said nozzle at a distance therefrom to provide a lateral restricted passage between said wall and said nozzle end, whereby any hot gases generated in said chamber upon formation therein of an arc, expand through said nozzle and issue therefrom in the form of a jet striking said wall and diverted thereby into said lateral restricted passage, said flattened chamber being in the general shape of a sector of a circle, said flat nozzle extending along theperiphery of said sector over a generally circular arc, and said wall extending over an arc of a circle substantially concentric with the former-mentioned arc, said device further comprising two elongated and flattened expansion chambers extending on both sides yof the nozzle and communicating therewith, and said expansion chambers extending over arcs of a circle and having, lat one end thereof, an outlet aperture opening to the atmosphere.

References Cited in the iile of this patent UNITED STATES PATENTS 1,836,994 ASlepian Dec. 15, 1931 2,215,797 Sauer Sept. 24, 1940 2,292,158 Prince Aug.14, 1942 2,293,452 Boehne Aug. 18, 1942 2,393,164 Hobson Jan. l5, 1946 v2,555,993 Oppel et al. June 5, 1951 v2,633,518 Miller Mar. 31, 1953 FOREIGN PATENTS '732,196 'Great Britain June 22, 1955

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