US2629798A - Cross air blast circuit breaker - Google Patents

Description

u v Ink 1 E I 7 Feb. 24, 1953 E SALZER CROSS AIR BLAST CIRCUIT BREAKER Filed Oct. 50, 1948 Patented Feb. 24, 1953 CROSS AIR BLAST CIRCUIT BREAKER Erwin Salzer, Brookline, Mass., assignor to Allis- Chalmers Manufacturing Company, Milwaukee, Wis., a corporation of Delaware Application October 30, 1948, Serial No. 57,577

11 Claims. (01. 200-148) My invention relates to gas blast circuit breakers for interrupting high alternating currents, and more particularly air blast circuit breakers.

t has been found that extinction of high current arcs can be achieved most efficiently where the arc incident upon separation of a pair of relatively movable contacts is moved by an arc-extinguishing blast of gas against an arc-restraining barrier of insulating material. In such an arrangement the arc is caused to form two loops, i

one on each side of the arc-restraining barrier. The interrupting efiiciency of such a structure is probably primarily due to the fact that the gas blast acts on a plurality of arc loops and that the portion of the are which is urged by the blast into engagement with the arc-restraining barrier is effectively deionized by surface action thereof. That surface action can be enhanced by making the arc-restraining barrier of an insulating material, preferably of organic nature, evolving 1 large amounts of gases or vapors when exposed to the heat of the arc, resulting in cooling and dilution of the arc stream into which they are caused to diffuse.

These advantageous features are, however, in part ofiset by the fact that the arc length is rapidly increased by the arc-extinguishing blast during the time elapsing between arc initiation and are extinction. That rapid increase of the length of the are results in an increase of the total arc energy or switch energy defined by the equation wherein ea is the arc voltage which increases as the arc length increases, is the arc current and T the time of arc extinction.

It is therefore one object of my invention to provide a circuit breaker of the gas blast type wherein the surface action of an aro restra-ining barrier of insulating material plays a major part in the interrupting process and wherein the length of each of the two arc loops which are formed on opposite sides of the arc-restraining barrier is limited, thus limiting the total are energy involved in the process .of circuit interruption.

It has been found that extinction of arcs in gas blast circuit breakers can .be considerably facilitated by the provision of probe electrodes and resistors for shunting predetermined arc sections. If the ohmic value of such a shunt resistor ,is small compared to the resistance of the arcsecr tion which is shunted by it, a relatively large portion of the arc current flows through the shunt resistor and the resulting decrease of current in the shunted arc section is correspondingly high. The arc section carrying but a small portion of the total are current is then rapidly extinguished under the action of the gas blast. Upon extinction of such an arc section the resistor is serially related to the remaining portion of the arc, thus limiting the arc current.

The smaller the ohmic value of a shunt resistor, the easier it is to extinguish by the blast of gas the section of the are which is shunted by the resistor, but the less eifective is the action of the resistor when it is subsequently arranged in series with the remaining portion of the arc. Conversely, where the ohmic value of a shunt re sistor is relatively large, the resulting decrease of current in the shunted arc section is relatively small, and hence it is relatively dificult to extinguish the shunted section of the are by the blast of gas. Whenever this can be achieved the resistor, which is then serially related to the remaining portion of the arc, will be relatively effective owing to its relatively high ohmic value.

It is thus apparent that provision of shunt resistors having either a relatively low ohmic value, or a relatively high ohmic value, is subject to serious limitations.

It is therefore another object of my invention to provide a circuit breaker of the gas blast type permitting insertion of a relatively large total amount of resistance into the circuit in two consecutive steps each involving but a relatively small amount of resistance wherein each such step comprises elimination, by a shunt resistor, of one of the arc sections, relatively remote from the surfaces of the arc-restraining barrier, of the two are loops situated on opposite sides of said barrier, and wherein a residual or low current are extending transversely across the upstream end of the arc-restraining barrier is allowed to subsist until after elimination of said sections of the arc, and wherein said residual are extending transversely across the upstream end of the arcrestraining barrier forms the portion of the arc last to be extinguished by the blast.

In gas blast circuit breakers wherein the arc is moved against an arc-restraining barrier and is lapped around it by a blast of gas directed substantially transversely to the direction of contact separation, the arcing zone at the time of arc extinction is situated far downstream from the point where the arc was initiated. Metal vapors which are evolved from the hot arc terminals and electrons which are emitted from the .arc terminal forming the cathode of the arc discharge are transferred by the blast in down- 3 stream direction into the arcing zone and greatly impair the dielectric recovery thereof.

It is therefore another object of my invention to provide a circuit breaker of the cross-gas-blast type precluding or greatly limiting contamination of the downstream arcing zone by metal vapors evolved from and electrons emitted from any are terminals situated upstream from the arcing zone.

-In gas blast circuit breakers comprising an arc chute wherein the arc is moved against an arc-restraining barrier and lapped around it by an arc-extinguishing blast of gas directed substantially transversely to the direction of contact separation, the amount of ionization within the two blast passages located on opposite sides of the arc-restraining barrier depends, among other factors, upon the length of the arc loop within each passage and upon the number of arc roots or arc terminals located in each passage or upstream of the passage and feeding arc products into the passage. Under otherwise similar conditions, the amount of ionization within each blast passage tends to be the smaller, the shorter the length of the arc loop within the passage.

type wherein portions of the arc loops formed on opposite sides of the arc-restraining barrier are eliminated in the early stages of the interrupting process, resulting in a shortened arc path which is being deionized to the point of final arc extinction in the ultimate stages of the interrupting process without being seriously contaminated by evolution of metal vapors and by thermionic emission from any are terminal located at any point upstream from the arc path.

The are in a cross-gasblast circuit breaker comprises two critical portions. One of these portions is the arc section situated immediately adjacent the stationary contact where there is a cloud of metal vapors evolved and of electrons emitted from the stationary contact. The other of these portions is the arc section situated immediately adjacent the movable contact where the atmosphere is likewise electrically contaminated. This second critical portion is situated closest to the opening provided in the arc chute for withdrawal therefrom of the movable contact, and the hot are products resulting from that second critical portion of the are have a certain tendency to leak out from the arc chute through said opening.

lit is therefore another object of my invention to provide a circuit breaker of the cross-gas-blast type wherein the arc is eliminated in three consecutive steps comprising elimination of the section of the are immediately adjacent the stationary contact, subsequent elimination of the section of the are immediately adjacent the movable contact, and finally elimination of an intermediate substantially V-shaped arc section ex tending from one side of the arc-restraining barrier transversely across the upstream edge portion thereof to the other side of the arc-restraining barrier.

In a gas blast circuit breaker wherein the combined action of the arc-extinguishing blast and of the arc-extinguishing structure is sufficiently effective in building up the dielectric strength of the arc gap after current zeros to preclude any subsequent gap breakdown by the rising recovery voltage, there is relatively little need to rely on the insertion of resistance into the circuit during the interrupting process. In such cases resistance switching may be considered as a safety factor rather than a vital feature of the circuit breaker. Under such circumstances resistors can be used which have a relatively small ohmic value which, in turn, minimizes .possible failure of proper transfer of the arc current to the resistor.

It is therefore one of the objects of my invention to provide a circuit breaker of the gas blast type having one or more shunting resistors the resistances of which are sufficiently low to efiect rapid and reliable extinction of the respective arc section which is shunted by them and which circuit breaker has a large inherent interrupting capacity suflicient to clear shout circuit currents though not very much reduced by previous in sertion of resistance into the circuit.

Further objects and advantages of my invention will become apparent as [the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming pant of this specification.

Referring to the drawings,

Fig. 1 is an elevational, sectional view taken along plane 1-1 of Fig. 2 of a medium high voltage cross-air-blast circuit breaker embodying my invention in the closed circuit position thereof;

Fig. 2 is a cross-section along the plane II--II of Fig. 1;

Fig. 3 is a cross-section along the plane IIIIII of Fig. 1; and

Fig. 4 is a cross-section along the plane IV-IV of Fig. 1.

The circuit breaker comprises essentially relatively movable contacts I and 2. The stationary contact I is formed by finger contacts and the movable contact 2 is a substantially sickle shaped blade contact. Stationary contact I is connected to terminal 3 and movable contact 2 is connected to a terminal not shown in the drawing. Movable contact 2 is hingedly supported at 4. Hinge structure 4 may be adapted to carry current from the terminal member not shown to blade contact 2. Operating lever 5 is hinged at 6 to contact blade 2. Pulling lever 5 in a downward direction results in rotation of blade contact 2 in a clockwise direction about hinge 4 and disengagement of contact 2 fro-m contact fingers I. Pushing lever 5 in an upward direction results in a similar counterclockwise rotation of blade contact 2 and engagement of blade contact 2 by contact fingers I.

Blast tube I connects the arc chute which has been generally indicated by reference sign 8 with a tank (not shown) wherein a supply of are extinguishing gas as, for instance, compressed air at a pressure ranging from 150-250 lbs. per square inch, is stored. Arc chute 8 comprises a front plate 9a, a back plate 9?), side plates I0 and a nozzle member I I. Nozzle member II is made of an insulating material that evolves relatively large amounts of gaseous products when exposed to the heat of the are as, for instance, hard fiber. Nozzle member II may be moulded, if desired, from a. compound consisting of a mixture of cement and asbestos. Such a nozzle member will evolve fairly large amounts of gaseous products when exposed to the heat of the are, the amount or gas evolved being, however,

smaller than in the case or a nozzle member made of fiber or of a suitable synthetic resin as, for instance, a carbamide resin. A pair of arc runners or are horns l2, I3 is arranged at the entrance or nozzle H a little downstream from the downstream "edge of blade contact 2. Arc horns l2 and I3 are aligned the direction of se aration or contacts 1 and z and arranged on opposite sides of nozzle member H. Their pur pose is to cause rapid movement of any are which is drawn btwh contacts 4 and 2 into nozzle passage H which is defined by nozzle member H.

As can best be seen from Fig. 2, the area ex posed to now of nozzle member it increases all the way from intake I5 to outlet Ii. Fig. 1 shows that the rate or increase of the area exposed to flow or cross-section or passage H is much larger toward outlet is than close to inlet l5.

It will be observed that passage l1 defined by blast tube 1 and passage l4 defined by nozzle member II are coaxial, while the arc extinguishing' blast through passages I! and i1 is directed transversely to the direction of separation of contacts I and 2.

The are products which are formed within nozzle passage H are cooled in a chamber 18 situated downst'rcamlrom passage H.

Nozzle portion ll has a relatively small average area exposed to ilow, and the entrance or inlet l5 and the exhaust or outlet IG thereof are spaced a relatlvely small distance apart from each other. Cooling chamber l-B has a relatively large area exposed to flow, and an entrance porti-on l9 and an exhaust portion 20 which are spaced a relatively large distance apart from each other.

The arc-restraining barrier 2| of heat-resisting insulating material is arranged in cooling chamber i8 and protrudes into nozzle passage ll defined by nozzle member ll. Barrier 2| is arranged transversely to the direction of separation of contacts I and 2. The upstream end of barrier 21 is formed by a member 22 of organic insulating material which evolve relatively large amounts of gas when "exposed to the heat or the are, e. g. hard fiber. It will be noted that the po'rtiofi'of member 22 enga ed by the are increases in width in doamstream direction to pro the are and member 22. Member :22 is provided with a groove 2-3 receiving the plate-shaped portion of barrier 21 which :subdivldes cooling chamber IB into two separate passages 28, 25. The plate-shaped portion of barrier 2| and the upstream barrier member '22 are secured together by means of pins 26 which are made of insulat ing material as, for instance, hard fiber. The upstream arc-receiving edge or barrier 21 is provided with a shallow notch 21 which tends to prevent lateral movement of the section of the are which is lapped around member '22 or barrier 2|. Member 22 of barrier 2| is secured to nozzle member H by means of pins 28, as can best be seen in Fig. 2. y

Single probe electrodes 29 andco are arranged on opposite sides of barrier 21 and barrier member 22, respectivel Probe electrodes '29 30 are so insulated from "each other as to be capable to be at a sufli'ciently different potential to form terminals Eior an are extending 'therebe'tween. Probe electrodes :29 and 8-0 are fiormed "by plates arranged substantially transversel to the aroextinguishing blast and having arc-engaging edges which project :into home passage ll. The

are terminals formed on probe electrode plates 23, 30 have a certain tendency to move to the downstream surfaces of said plates, 1. e. their surfaces which are not exposed to the blast. The are terminals will stay there, until complete and final extinction of the arc has been achieved, since they are precluded from moving in downstream direction. It is therefore apparent that the terminal-forming points of probe electrodes 29 and 30 are located downstream from the upstream end of barrier 2|, 1. e. downstream from the upstream end of barrier member 22. On the other hand, the terminal-forming points of probe electrodes 29 and 30 are located upstream from the downstream end or exhaust 16 of nozzle passage 14.

Probe electrodes 29 and are born [2 are connected by a shunt 3|. Similarly, probe electrode 30 and are horn [3 are connected by a shunt 32.

Shunts 3| and 32 may have virtually zero resistance, or one of them may have virtually zero resistance while the other may be constituted by a resistor having an appreciable resistance, or both of them may be constituted by resistors having an appreciable judiciously selected resistance. The operating characteristics of the circuit breaker differ depending upon which of the above alternatives is being adopted, and depending upon which ohmic value, or ohmic values, is being given to one or both of the resisters. This affords a great flexibility which can be achieved with a minimum of changes.

Arc horn I2 is conductively connected to stationary finger contacts I. In a similar way, arc horn I3 is conductively connected to movable blade contact 2. The conductive connection between arc horn l3 and blade contact 2 comprises a metallic irame structure 33 supporting sets of contacts 34 arranged on opposite sides of and engaging blade contact 2.

Stacks 35, 36 of spaced metal plates are arranged in passages 24 and 25, respectively, for increasing the rate of cooling of the products of arcing flowing past said stacks. Stack 35 is 'condu'otively connected by conductor 31 to probe electrode 29 and by shunt 3| to stationary contact 1. Similarly, stack 36 is conductively connected by conductor 38 to probe electrode 30 and by shunt 32, frame 33 and contacts 34 to movable blade contact 2. Conductors 3! and 38 constitute evidently a second pair of shunts in addition to the pair of shunts 3|, 32.

The are formed upon separation of contacts I and 2 is urged into nozzle passage M by a blast of gas rushing through blast tube I. The arc terminal formed on the stationary contact finger situated farthest downstream and projecting farthest into the blast is immediately transferred to are horn l2. The other are terminal which is formed on blade contact 2 is moved to the right, as viewed in Fig. 1. As soon as the arc loop engages probe electrode 29, the section of the arc extending between arc horn l2 and probe electrode .29 will be shunted, and rapidly extinguished hereafter. Vaporization of the metal of which are horn i2 is made and emission of electrons from arc horn 12 are stopped almost instantly upon transfer of the entire arc current to shunt 3i and probe electrode 29. From then on probe electrode 29 forms one of the terminals of the main are which extends from probe electrode 29"transversely across barrier member 22 to movable blade contact 2 which forms the other are terminal. As soon as the arc loop on the right side of barrier member 22, as viewed in Fig. 1, engages both arc horn |3 and probe electrode 39, the section of the arc shunted by shunt 32 tends to become unstale and will be rapidly extinguished thereafter by the arc-extinguishing blast.

Upon shunting and extinction of the arc section extending between arc horn l3 and probe electrode 30, the current path through the circuit breaker is as follows: terminal element 3, stationary finger contacts l, are horn l2, shunt 3| and probe electrode 29. The gaseous current path begins at the arc termianl on probe electrode 29 and extends from there in upstream direction, then transversely across the arc-restraining edge of barrier 2| or barrier member 22, respectively, and then in downstream direction to probe electrode 30, where the second portion of the metallic current path begins. That portion includes probe electrode 30, shunt 32, metal frame 33, stationary contacts 34 and sickle shaped blade contact 2. Complete interruption of the circuit is achieved when the section of the are extending between probe electrodes 29 and 30 has been extinguished. This section of the arc is particularly vulnerable because it is subjected to the combined action of the arc-extinguishing blast and to the flow of gaseous products which are evolved under the heat of the arc from member 22 of barrier 2|. Moreover, and this is particularly important, there is no arc root or are terminal situated at any point upstream from the section of the arc extending between probe electrodes 29 and 30 and lapped around member 22 and, therefore, there is no precontamination of the blast which acts upon that are section by products of arcing formed at any upstream arc root or are terminal. Since the section of the arc which is lapped around member 22 is situated upstream from the arc roots or are terminals formed on probe electrodes 29 and 30, contamination of that are section by products of arcing formed on either arc root or are terminal is minimized. Electrons which are emitted from either of both probe electrodes 29, 30 are subject to a strong tendency to fiow with the arc-extinguishing blast in a downstream direction and out of passage l4 into cooling chamber l9, rather than against the arc-extinguishing blast in an upstream direction transversely across member 22 and thence to the other probe electrode. Owing to these facts the dielectric recovery along the upstream wedge-shaped end of barrier 2| will be relatively rapid, resulting in great interrupting eiiiciency.

It has been pointed out above that the probe electrodes 29 and 30 must be insulated from each other in such a way as to cause the path of least resistance of any are section interconnecting said probe electrodes to extend transversely across the upstream edge of barrier 2|. If pins 26 were made of metal rather than insulating material, this is likely to cause such lowering of the insulation level between probe electrodes 29 and 30 and such change of the electric field or potential distribution between said probe electrodes that the path of least resistance of any are section interconnecting probe electrodes 29 and 30 would extend from probe electrode 29 to the left end of one of the pins 26 and from the right end thereof to probe electrode 30. Therefore, if pins 26 were made of metal, the section of the arc lapped around the upstream edge portion of member 22 would be shunted by two serially related arcs, one extending from probe electrode 29 to one of pins 26 and the other from the one of pins 26 to probe electrode 30. This would result in unstability and rapid extinction of the arc section lapped transversely across the upstreamedge of member 22. Upon extinction of that are section the current would be carried solely by the two serially related arcs from probe electrode 29 to pin 26 and from pin 26 to probe electrode 30. Extinction of these two arcs would involve rather unfavorable conditions as virtually complete elimination of the deionizing surface action of barrier member 22 and an increase of the number of arc terminals from two to four and consequent contamination of the zones of both arcs by metal vapors and other are products formed at points situatedupstream from the arcing zones of the two arcs. The proper insulation level between probe electrodes 29, 30 is, therefore, a crucial factor and an undue reduction of the insulation level between said probe electrodes will materially effect the mode of operation and the interrupting efficiency of the circuit breaker.

In order to obtain the desired operating characteristics, including an arc section last to be extinguished extending transversely across the upstream edge portion of the arc-restraining insulating barrier 2|, that barrier should extend from nozzle member II to a considerable length in downstream direction. The length of barrier 2| must be suflicient to preclude a transfer of the arc section which is urged by the arc-extinguishing blast into engagement with the upstream edge of barrier 2| to and transversely across the downstream edge thereof.

Assuming that there is a sufficiently high insulation level between the probes 29 and 30 but that, for one reason or another, the arc section last to be extinguished extending transversely across member 221s allowed to subsist for some time. Under such conditions, the two blasts of gas on either side of nozzle passage l4 will'cause continued elongation of the arc. If sufiicient resistance has been introduced into the circuit by means of shunts 3| and 32, as should normally be done, continued arc elongation is not likely to result in excessive arc energy. But where the ohmic value of shunts 3|, 32 is very small, the arc should not be allowed to elongate freely. Shunts 31 and 38 are provided for limiting the elongation of the arc section extending between the probe electrodes 29 and 30 and being lapped transversely across barrier member 22. When the arc-extinguishing blast on the left side of nozzle passage l4 causes the arc to loop until it engages the stack 35 of cooling plates, the section of the are extending between probe electrode 29 and stack 35 will be short-circuited by shunt 31 and thus instantly eliminated. This results in a transfer to stack 35 of the terminal of the are which was heretofore on probe electrode 29. Similarly, when the arc-extinguishing blast on the right side of nozzle passage |4 causes the arc to loop until it engages stack 36 of cooling plates, the section of the arc extending between probe electrode 30 and stack 36 will be short-circuited by shunt 39 and thus instantly eliminated. This results in a. transfer to stack 36 of the terminal of the are which was here-' The longer an arc section is allowed to persist 9. in a circuit breaker, the more difficult it may be to extinguish it thereafter. For this reason it might prove to be desirable in a given application to provide shunt 31 in addition to shunts 3| and 32, while shunt 38 may be dispensed with.

Where the ohmic values of shunts 3i and 32 are not too small to limit short-circuit currents to an appreciable extent, shunt 31 may likewise be dispensed with.

Provision of shunts 31 and 38 results in that a relatively high voltage prevails across barrier 2| after circuit interruption has been achieved. Hence it is necessary to take precautions to preclude at any time any electric breakdown across barrier 2|. Since this entails additional expense, it is optional to dispense with at least one of shunts 31 and 38.

While I have illustrated and described as a preferred embodiment of my invention a circuit breaker wherein the nozzle portion and the cooling chamber are clearly distinguishable from each other, it will be apparent that my invention is likewise applicable to circuit breakers comprising arc chutes of fish-tail shape wherein the nozzle portion merges gradually into the cooling chamber.

Although but one embodiment of the present invention has been illustrated and described, it

will be apparent to those skilled in the art that various modifications and changes may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

It is claimed and desired to secure by Letters Patent:

1. A gas blast circuit breaker for interrupting high currents in alternating current circuits comprising a pair of relatively movable contacts for drawing an arc therebetween upon separation thereof; a nozzle structure of insulating material arranged adjacent said contacts substan-- tially transversely to the direction of contact separation; means for producing an arc-extinguishing blast of gas transversely across the gap formed upon separation of said contacts and axially through said nozzle structure; means defining a cooling chamber arranged downstream from said nozzle structure for receiving the blast escaping from said nozzle structure, the average cross sectional area of said cooling chamber being large compared to the average cross sectional area of said nozzle structure and the length of said cooling chamber being largecompared to the length of said nozzle structure; an arc-restraining barrier of heat-resistant insulating material arranged transversely to the direction of contact separation and projecting from said cooling chamber into said nozzle structure; a pair of arc horns aligned in the direction of contact separation each arranged on opposite sides of said nozzle structure for causing .rapid movement of said are into said nozzle structure; a pair of probe electrodes each on an opposite side of said barrier downstream from the point thereof situated highest upstream; a pair of shunts each connecting one of said pair of contacts and one of said probe electrodes for eliminating the sections of the are on opposite sides of said barrier relatively remote from the surfaces thereof while an arc section extending between said probe electrodes still persists, at least one of said pair of shunts being formed by a resistor for inserting resistance into the circuit under interruption prior to complete ex- 10 tinction of said arc, and means for insulating said probe electrodes from each other in such a way as to cause the path of least resistance of any are section formed between said pair of probe electrodes to extend transversely across the upstream end of said barrier.

2. In a gas blast circuit breaker for interrupting high currents in alternating current circuits, a pair of relatively movable contacts for drawing an arc therebetween upon separation thereof; means for producing an arc-extinguishing blast of gas adjacent said pair of contacts substantially transversely to the direction of contact separation; an arc chute comprising a nozzle portion arranged substantiall in the direction of said blast and a chamber for cooling the are products escaping from said nozzle portion, said nozzle portion having a relatively small average area exposed to flow and an entrance portion and an exhaust portion spaced a relatively small distance apart from each other, and said cooling chamber having a relatively large average area exposed to flow and an entrance portion and an exhaust portion spaced a relatively large distance apart, from each other; an arc-restraining barrier of heat-resistant insulating material in said cooling chamber protruding into said nozzle portion and arranged transversely to the direction of contact separation, the portion of said barrier engaged by said are increasing in width in downstream direction to provide an effective surface of interaction between said are and said barrier; a pair of arc runners each connected to one of said contacts and extending into said nozzle portion to transfer said are from said contacts into said nozzle portion, the downstream ends of said are runners being situated within said nozzle portion upstream from said chamber for cooling the are products and upstream from the upstream edge portion of said barrier, the only metal parts arranged in said nozzle portion in addition to said are runners being single probe electrodes on opposite sides of said barrier, said probe electrodes being so insulated from each other as to be capable to be at a diilerent potential to form a pair of terminals for an are extending therebetween, the terminal-forming points of said probe electrodes being located downstream from the upstream end of said barrier; a pair of shunts each connecting one of said pair of contacts to one of said probe electrodes for causing extinction of the sections of said are situated immediately adjacent said pair of contacts prior to extinction of the section of said are extending between said probe electrodes; and means for so distributing the potential across the gap formed between said probe electrodes as to cause the arc path of least resistance therebetween to extend transversely across said upstream end of said barrier to preclude formation of any other current path across said gap.

3. In a gas blast circuit breaker for interrupting high currents in alternating current circuits, a pair of relatively movable contacts for drawing an arc therebetween upon separation thereof; means for producing an arc-extinguishing blast of gas adjacent said pair of contacts transversely to the direction of contact separation; an arc chute comprising a nozzle portion arranged substantially in the direction of said blast and a chamber for cooling the are products escaping from said nozzle portion, said nozzle portion having a relatively small average area eX- posed to flow and an entrance portion and an exhaust portion spaced a relatively small distance apart from each other, and said cooling chamber having a relatively large average area exposed to flow and an entrance portion and an exhaust portion spaced a relatively large dis tance apart from each other; a single arc-restraining barrier of heat-resistant insulating material in said cooling chamber protruding into said nozzle portion and arranged transversely to the direction of contact separation; a pair of arc runners each connected to one of said contacts and extending into said nozzle portion to transfer said arc from said contacts into said nozzle portion, the downstream ends of said are runners being situated within said nozzle portion upstream from said chamber for cooling the are products and upstream from the upstream edge portion of said barrier; a pair of probe electrodes each arranged on an opposite side of said barrier transversely to the direction of said blast between said entrance portion and said exhaust portion of said nozzle at a point located downstream from the upstreamend of said barrier, said pair of probe electrodes being insulated from each other in such a wa as to cause the path of least resistance of any are section interconnecting said pair of probe electrodes to extend transversely across said upstream end of said barrier; and a pair of shunts each connecting one of said pair of contacts to one of said pair of probe electrodes.

4. An alternating current circuit interrupter comprising a pair of relatively movable contacts for drawing an arc therebetween upon separation thereof, an arc restraining insulating barrier arranged substantially edgewise with respect to said arc, means for producing an arc extinguishing blast of gas substantially transversely to the direction of contact separation, are runners arranged adjacent said contacts and conductively connected thereto for transferring said are from the region of arc initiation to a point downstream therefrom, a pair of probe electrodes arranged on opposite sides of said barrier downstream from said are runners and from the upstream edge of said barrier, said probe electrodes being insulated from each other in such a way as to cause the path of least resistance of any are section interconnecting said probe electrodes to extend transversely across said upstream edge of said barrier, and a pair of shunts each connecting one of said are runners and one of said probe electrode for eliminating the sections of the are situated on opposite sides of said barrier relatively remote from the surface thereof.

5. An alternating current circuit interrupter comprising a pair of relatively movable contacts for drawing an arc therebetween upon separation thereof, an arc restraining insulating barrier arranged substantially edgewise with respect to said are, means for producing an arc extinguishing blast of gas substantially transversely to the direction of contact separation, arc runners arranged adjacent said contacts and conductively connected thereto for transferring said are from the region of arc initiation to a point downstream therefrom, a pair of probe electrodes arranged on opposite sides of said barrier downstream from said are runners and from the upstream edge of said barrier, said probe electrodes being insulated from each other in such a way as to cause the path of least resistance of any arc section interconnecting said probe electrodes to extend transversely across said upstream edge of said barrier,

and a pair of shunts each connecting one of said are runners and one of said probe electrodes for eliminating the sections of the are situated on opposite sides of said barrier relatively remote from the surface thereof prior to extinction of the section of the arc extending from one of said probe electrodes in upstream direction to and transversely across said upstream edge of said barrier and thence in downstream direction to the other of said probe electrodes.

6. An alternating current circuit interrupter comprising a pair of relatively movable contacts for drawing an arc therebetween upon separation thereof, a nozzle structure of insulating material arranged adjacent said contacts transversely to the direction of contact separation, means for producing an arc extinguishing blast of gas substantially transversely across the gap formed upon separation of said contacts and axially through said nozzle structure, an arc restraining barrier of heat resistant insulating material ar-' ranged transversely to the direction of contact separation and projecting into said nozzle structure, arc runners arranged adjacent said contacts and conductively connected thereto for transferring said arc from the region of arc initiation to a point within said nozzle structure, a pair of probe electrodes on opposite sides of said barrier downstream from the point thereof situated highest upstream, a pair of shunts each connecting one of said arc runners and one of said probe electrodes for eliminating the sections of the are on opposite sides of said barrier relatively remote from the surfaces thereof while an arc section extending between said robe electrodes still persists, at least one of said shunts being formed by a resistor for inserting resistance into the circuit under interruption prior to complete extinction of said are, and means for insulating said probe electrodes from each other in such a way as to cause the path of least resistance of any are section formed between said probe electrodes to extend transversely across the upstream end of said barrier, said insulating means including the dielectric integrity of said barrier.

7. An alternating current circuit interrupter comprising a pair of relatively movable contacts for drawing an arc therebetween upon separation thereof, means for producing an arc extinguishing blast of gas adjacent said contacts substantially transversely to the direction of contact separation, an arc chute comprising a nozzle portion arranged substantially in the direction of said blast and a chamber for cooling the are products escaping from said nozzle portion, said nozzle portion having a relatively small average area exposed to flow and an entrance portion and an exhaust portion spaced a relatively small distance apart from each other, and said cooling chamber having a relatively large average area exposed to flow and an entrance portion and an exhaust portion spaced a relatively large distance from each other, an arc restraining barrier of heat resistant insulating material in said cooling chamber protruding into said nozzle portion and arranged transversely to the direction of contact separation, arc runners arranged adiacent said contacts and conductively connected thereto for transferring said are from the region of arc initiation to a point within said nozzle, single probe electrodes arranged on opposite sides of said barrier downstream of said are runners, said probe electrodes being so insulated from each other as to be capable of being at different potentials to form a pair of terminals for an arc extending therebetween, the terminal forming points of said probe electrodes being located downstream from the upstream end of said barrier and upstream from the downstream end of said nozzle, and a pair of hunts each connecting one of said are runners to one of said probe electrodes.

8. An alternating current circuit interrupter comprising a pair of relatively movable contacts for drawing an arc therebetween upon separation thereof, an arc chute for receiving said are, a single insulating barrier arranged within said are chute adjacent the gap formed upon separation of said contacts, means for producing an arc extinguishing blast of gas substantially parallel to the axis of said barrier for driving said are against an arc restraining edge portion of said barrier, are runners arranged adjacent said contacts and conductively connected thereto for transferring said are from the region of arc initiation to a point within said are chute, a pair of probe electrodes arranged on opposite sides of said barrier at points located downstream from said are restraining edge portion, a pair of shunts each connecting one of said contacts to one of said probe electrodes for eliminating the sections of said are situated on opposite sides of said barrier relatively remote from the surfaces thereof, and means for causing the section of said are last to be extinguished by said blast to extend from one of said probe electrodes in upstream direction to and transversely across said are restraining edge portion and thence in downstream irection to the other of said probe electrodes.

9, An alternating current circuit interrupter comprising a pair of relatively movable contacts for drawing an arc therebetween upon separation thereof, means for producing an are extinguishing blast of gas adjacent said contacts, an arc chute comprising an upstream relatively short and narrow nozzle portion arranged substantially in the direction of said blast and a downstream relatively long and wide cooling portion for reducing the temperature of the products of arcing formed within said nozzle portion, said nozzle portion having a relatively restricted inlet and a widely flaring outlet, a single are restraining barrier of heat resistant insulating material in said cooling chamber protruding into said nozzle portion and arranged transversely to the direction of contact separation, the portion of said barrier engaged by said are increasing in width in downstream direction to provide an effective surface of interaction between said are and said barrier, arc runners arranged adjacent said contacts and conductively connected thereto for transferring said are from the region of arc initiation to a point within said are chute, probe electrode means on opposite sides of said barrier consisting of a single pair of probe electrodes separated by said barrier, said probe electrodes being so insulated from each other as to be capable of being at different potentials to form a pair of terminals for an arc extending therebetween, the terminal forming points of said probe electrodes being located downstream from the upstream end of said barrier and between said inlet and said outlet of said nozzle portion, means for so distributing the potential between said probe electrodes as to cause the arc path of least resistance therebetween to extend transversely across the upstream end of said barrier, and means for shunting the sections of said are extending between said are runners and said probe electrodes. I

10. An alternating current circuit interrupter comprising a pair of relatively movable contacts for drawing an arc therebetween upon separation thereof, means for producing an are extinguishing blast of gas substantially trans versely to the direction of contact separation, an arc chute comprising a nozzle portion arranged substantially in the direction of said blast and a chamber for cooling the products of arcing escaping from said nozzle portion, said nozzle portion consisting of an insulating material evolving relatively large amounts of gas when exposed to the heat of the arc and having a relatively small average area exposed to flow, said cooling chamber having a relatively large average area exposed to flow and by far exceeding the length of said nozzle portion, a single arc restraining barrier of insulating material arranged in said cooling chamber transversely to the direction of contact separation, said barrier being free from any metal masses exposed to arcing and having an upstream portion projecting into said nozzle portion and being provided with an arc restraining notch, arc runners arranged adjacent said contacts and conductively connected thereto for transferring said are from the region of arc initiation to a point within said nozzle, single probe electrodes on opposite sides of said barrier, said probe electrodes projecting transversely across said nozzle portion with the inner ends thereof projecting into said area of said nozzle portion exposed to flow, said probe electrodes being arranged in spaced relation from said barrier to form an air gap between said barrier and each said probe electrode, said probe electrodes being so insulated from each other as to be capable of being at different potentials and to form a pair of terminals for an are extending therebetween, the terminal forming points of each said probe electrodes being located in such a way as to be separated from each other by said upstream portion of said barrier, means for so distributing the potential between said probe electrodes as to cause the arc path of least resistance therebetween to extend transversely across said upstream portion of said barrier, and a pair of shunts each interconnecting one of said contacts and one of said probe electrodes.

11. An alternating current circuit interrupter comprising a pair of relatively movable contacts for drawing an arc therebetween upon separation thereof, means for producing an are extinguishing blast of gas adjacent said contacts transversely to the direction of contact separation, an arc chute comprising a nozzle portion arranged substantially in the direction of said blast and a chamber for cooling the are products escaping from said nozzle portion, said nozzle portion having a relatively small average area exposed to flow and an entrance portion and an exhaust portion spaced a relatively small distance from each other, and said cooling chamher having a relatively large average area exposed to flow and an entrance portion and an exhaust portion spaced relatively large distance from each other, a single arc restraining barrier of heat resistant insulating material in said cooling chamber protruding into said nozzle portion and arranged transversely to the direction of contact separation, said barrier being free from any metal masses exposed to arcing, arc runners arranged adjacent said contacts and conductively connected thereto for transferring said are from the region of arc initiation to a point within said are chute, single probe electrodes on opposite sides of said barrier, said probe electrodes projecting transversely across said nozzle portion with the inner ends thereof projecting into said area of said nozzle portion exposed to flow, said probe electrodes being arranged in spaced relation from said barrier to form an air gap between said barrier and each said probe electrode, said probe electrodes being so insulated from each other as to be capable of being at different potentials to form a pair of terminals for an are extending therebetween, the terminal forming points of said probe electrodes being located downstream from the upstream end of said barrier and upstream from the downstream end of said nozzle, and a pair of resistors each connecting one of said pair of contacts and one of said probe electrodes.

ERWIN sALzER.

1 6 REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,861,129 Milliken May 31, 1932 1,944,402 Clerc Jan. 23, 1934 2,284,842 Prince et al June 2, 1942 2,345,724 Baker et al. Apr. 4, 1944 2,451,669 Eichenberger Oct. 19, 1948 2,486,127 Davies Oct. 25, 1949

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