US2486127A - Air blast electric circuit breaker - Google Patents

Description

Oct. 25, 1949. v s 2,486,127

AIR BLAST ELECTRIC CIRCUIT BREAKER Filed May 8, 1945 FigJ. Z6 Z7 J I 9 20 a J \F I0 4 3 4 w If. t lZ Inventor:

David R. Davies,

is Attorney.

Patented a. 25,

r 1 2,486,127 era BLAST ELECTRIC cmcmr anaemia 1mm Reginald 1min, sue, lin man-si ner;

by mesne assignmen ts, to General Electric Company, a corporation or New York ApplicationMay' 8,1945,ScrialNo.592,589 a InGrcat Britain June 26,1944

My J-invention relates to electric circuit breakers and more particularly to'electrlc circuit breakers of the typeemploying a blast of air or ctherfluid to"extiziguish the are formed when the-circuittis broken between relatively movable :contacts. Specifically, my invention is an improvement on .iUnited States Letters Patent 2,284,842, Prince :et al.,granted June 2, 1942,

1 wherein a blast of gas is directed at high velocity transversely across the arc" gapformed between the relatively separable contacts.

The cross-gas blast circuitrbreaker'disclosed in the above mentionedPrince et a]. patent achieved very efiectivearcinterruption by blasting the are drawn between the separable contacts sidewise against and elong'atingly around the edges of a plurality oftran'sverse barriersarranged fanwise in a divergent arc chute. It is nowjrecog *nized that the interrupting characteristics of this general type of cross'blast breaker can be eiiectivelyimproved by first transferring the are 'drawn'by the separable. contacts to a pair of adjacent electrodes which constitute a so-called ffixed gap whereby'the arc length, and consequently the liberated arc energy, is effectively reduced. -As a result of this limitation of arc length and energy, are interruption can now be attained more efficiently even though but one transverse barrier is provided for suppressing the bowing of the arc downstream into the arc chute structure in the manner disclosed in U. S.-Patent 2,452,953 to Paul et al., patented Nov. 2, 1948' and assigned to thesame assignee as the present application I I My-invention is directedto the further improvement of a fixed-gap, singlebarrier type of cross gas blastbreaker whereby better control of the arc and extinguishment" thereof is made possible? Also contemplated-is an improved exhausti'arrang'ement fora cross gas blast circuit breaker whereby the gas products'of the single are are dividinglydiverted into atleast two se regated exhaust passages for'minimizing thepossibilityof restrike voltage breakdown through the ionized are products; 1

' It is therefore-an object of'iny invention to proof electric circuit breakers It is another f-object cfmy invention to provide'a cross gas'blasttype circuit breaker having vide an improved fixed'gap across 'gasblast type a cialms. (CL'200148) ing in which ized products of the single arc drawn by the relatively movable contactsare divided and segregatingly isolated into a pair of divergent insulating exhaust tubes.

Further objects and advantages of my invention willbecome apparent as the following description' proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claimsflannexed to and forming a part of this specification; I w e For a better understandingcf my invention reference may be had to the accompanying draw- 7 I Fig, 1 is an elevational viewinsection of an electric circuit breaker embodying my invention showing the circuit, breaker in the closed position; and Fig. 2 is asornewh'at schematic diagram of"thecontact structureof Fig. 1 with the contacts 'shown'separated'tp 'a' predeterminedextent during the circuit interrupting operation. 7 j

Referring now to the drawings, I have illustrated an electric circuit breaker generally indicated at-l in the form of a removable unit for use with metal-clad switchgear. The circuit breaker-i is enclosed withina metal housing 2 from which extend a plurality of conductor studs 3, the terminals 4 of which are adapted to be electrically connected with cooperating terminals mounted withinan associated metal enclosure (not shown). p

Suitably supported withinmetal enclosure 2 is an insulating arc extinguishing structure 5 provided with a firstf'passageway 6 therein, and a second "passageway 'i arranged substantially transverse oi said first passageway A stationary contact 8 comprising a plurality of spring biased contact fingers 5 is mounted within passageway Q and a' movable'arcuate contact 'I Ois adapted to move in passageway 8 todraw anarc therein upon relative separation from stationary contact 8 Stationary contact 8 is electrically connected to the upper conductor stud Qasby means of conducting member ll. Movable arcuatecontact It, on the other hand; is illustrated as forming an in-' tegral part of a swinging link I! pivotally mounted at It to the end of lower conductor stud I which extends into housing 2. It will be obvious to those skilled in the art that swinging link I2 will be connected to a suitable operating mechanism (not shown) as by means of the link It to cause relative separation of contacts I and II. When the contacts I and ID are closed in the manner shown in Fig. 1 the circuit is completed between the terminals I of conductor studs 2 through contacts I and It.

The second passageway 1 is preferably connected to a conduit ll which in turn is connected to a source of fluid under pressure, such as air or other gas, through a suitable blast valve (not shown). As was mentioned above, the passageway I is substantially transverse to the passageway 8 within which the arc is drawn whereby the circuit breaker I may be correctly termed a cross gas blast circuit breaker. Also arranged within insulating arc extinguishing structure I are a pair of diverging passageways l6 and I1 arranged in divergent relationship to each other and each connected to passageway I near its intersection with passageway I, as is clearly shown in Fig. 1 of the drawing. Diverging passageways l6 and I1 might well be considered as branches of passageway I.

As is disclosed and claimed in the aforementioned Paul et al. Patent 2,452,953 improved in terrupting capacity is obtained when the arc is extended to some short preferred gap length and extinguished. In accordance with the disclosure of the above mentioned copending Paul application, I provide a preferred arcing gap l8, formed between a stationary electrode l9 arranged in passageway It and a stationary electrode 20 arranged in passageway l'l. Stationary or fixed arcing electrode It extends along diverging passageway it for a predetermined distance and similarly, fixed electrode 20 also extends along passageway I! for a predetermined distance so as in effect to provide a pair of divergent fixed electrodes. Fixed or stationary electrode is is electrically connected to conducting member H and consequently stationary contact 8. Fixed electrode 20, on the other hand, is electrically connected to a sliding contact 2| in sliding engagement with movable contact ll. With this arrangement it is obvious that upon relative separation of contacts 8 and I an arc is drawn between them which arc is transferred to electrodes I9 and 20 which provide a fixed preferred gap It for optimum arc extinguishing action. The fixed gap l8 remains effective until movable contact It moves out of engagement with sliding contact 2| by which time the are drawn will have been extinguished and l the separation of movable contact Ill from sliding contact 2| will provide the desired isolating gap.

The diverging electrodes l9 and 20 provide a very desirable function in connection with my invention in that the current flowing through the loop formed by the diverging electrodes and the arc across gap It will produce a magnetic field tending to force the arc downwardly in opposition to the fluid blast from conduit I5. As a consequence thereof the arc tends to dwell near the point where the gas blast is most effective and furthermore is maintained short so that the energy liberated in the arc extinguishing structure is maintained at a minimum.

The above-mentioned magnetic eflect influencing the are which is transferred to the gap electrodes will be best understood by referring to Fig. 2. It is well-known that two spaced parallel conductors carrying current in the same direction will be attracted toward each other by virtue of the magnetic lines of force produced around the conductors due to the current flowing in each. Conversely, two spaced parallel conductors due to the current flowing in each. Conversely, two spaced parallel conductors carrying current in opposite directions will be urged apart by the magnetic lines of force which crowd in between the two conductors. In either of these situations the magnitude of the force is proportional to the amount of current flowing and inversely proportional to the distance between the two conductors. When the downwardly extending portions of the electrodes I2 and 2| are connected in series, as when Joined by the are A, it will be evident that current flows through the downwardly extending portions of these electrodes in counter-directions. i. e., downwardly in one and upwardly in the other. Accordingly, in conformance to the above well-known theory, the magnetic eflect will tend to force the electrodes apart, the magnitude of this force being greatest across the lowermost ends of the electrodes. 1. e., where the distance between these ends of the electrodes is relatively small. Since electrodes II and 2| are fixed, they, of course, remain stationary and the are A instead is moved downwardly by this crowding of the lines of force and. consequently, is bowed downwardly as shown. Stated more simply. the electrodes It and 2|. together with the are A deflne a loop circuit which tends physically to expand or get larger due to the crowding of the lines of force in the space between the electrode. Since the arc portion or the loop is not flxed, the magnetic eflect moves the arc downwardly against the fluid pressure so that the arc may assume a position such as that indicated at A in Fig. 2. films, it will be seenthatthisarclengthandenergylimiting feature ismost effective at the very time when it is important that the arc length and energy be controlled, i. e., immediately after transfer of the arc to the electrodes I2 and 20 and before current zero is reached. After the current peak and as current zero is armroached, the intensity of the arc A diminishes so that it is readily extinguished and its re-ignition is prevented by the gas blast. Should the arc persist and move upwardly along the downwardly extending portions of electrodes II and 22, the tendency for it to bow downwardly progressively decreases for the reason that the loop progressively becomes less clearly deflned and will finally disappear altogether if the conflguration thereof assumes the equivalent of a straight line conductor. Should this condition be reached. i. e., with the downwardly extending portions'oi electrodes is and 20 out of the circuit, the arc would then have no tendency to bow downwardly, but rather would bow upwardly due to the fluid blast to assume a position such as is indicated at B in Fig. 2. The wedgelike member 2| shown in Fig. 1 will ordinarily prevent the are from assuming the position indicated at B in Fig. 2. Should the arc for any reason persist long enough to bend around the member II, the loop conflguration of the arc would still be preserved and the magnetic effect would still be operative to limit the length and energy of the arc.

Extending from diverging passageway II is a tube of insulating material 22 which is secured to the arc extinguishing structure 5. Similarly, extending from diverging way I1 is an insulating tube 22. These tubes 22 and 22 are arranged. jdivergingrelationshipwith respect to each otherwith their .upper ends extending into apertures 24 and 25, respectively, formed-in the top: of metal. enclosure 2... Thesev aperturesare preferably .coveredby. asuitablexhood such as 26 and 2.1; respectively.. 1 Suitable 'arc .andgas, cooling means are preferably ,disposedin insulating tubes 22 an'd23. As

illustrated..'the cooling meanscomprise groups of perforated metal platesorgrids 28 between which are disposed a plurality of metal balls 29. These metal balls might be bras's or other suitable material. illustrated', 'one group in each tube is-preferably arrangednear theentrance to the tubes.

In order to aid the interrupting operation, I preferably provide a resistor 30 connected across fixed electrodes I9 and 20 as is clearly shown in Fig. 2. In accordance with my invention, resistor 30 is preferably supported by being wound around diverging tubes 22 and 23, as is clearly shown in Fig. 1.

The operation of the circuit breaker I described above will be obvious to those skilled in the art in view of the detailed description included above. During the circuit opening operation movable contact Ill is separated from fixed contact 8 and an arc is drawn in first passageway 6. This arc is impelled by the air blast in passageway i to move to electrodes i9 and 20 which define fixed gap l8. Due to the inverse loop configuration of fixed electrodes I9 and 20 the current flowing through these electrodes and through the arc across gap 18 will produce a magnetic field in such a direction to produce a force on the are 2-- which will oppose the force produced on the arc by the fluid blast thereby retaining the arc with-- in the gas blast at the lower end of the fixed contacts i9 and 20. Also holding the are physically in this desirable extinguishing zone is the wedgeform barrier structure 3|. By this cooperation the arc is rapidly extinguished at the first current zero and the movable contact It continues to move to produce the necessary isolating gap.

It will be understood that the hot gases evolved during the interrupting. operation are cooled within the two tubes before expulsion from the upper ends thereof to the exterior of the metal enclosure 2. As long as the movable contact i electrically engages sliding contact 2! the resistance 36 is connected in parallel with the arcing contacts. This arrangement will aid circuit interruption in' a manner well understood by those skilled in the art.

It will be understood that where desired, more than two insulating tubes such as 24 and 23-may be provided for the arc extinguishing structure, and these tubes may be disposed in positions other than those indicated.

It will be seen that with the arrangement according to the invention the ionized gas produced upon interruption of current through the circuit breaker is divided into two or more independent streams which are adequately cooled before being discharged to the atmosphere and that this subdivision is obtained bymeans of discharge passages comprising insulating tubes separate from one another so that all hazardous intercommunication by leakage of the ionized gas between the passages is obviated. The above described arrangement therefore provides a cross gas blast circuit breaker possessing exceptional arc extinguishing characteristics which moreover is capable of withstanding high rates of recovery voltage without danger of the are 6 restriking by re-establishment through the ionized arc products.

While I have shown and described a particular embodiment of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from my invention in its broader aspects and I, thereforefaim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

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

' 1. A gas blast electric circuit breaker of the cross blast type comprising an insulating are extinguishing chamber including a first passageway therethrough, a pair of relatively movable contacts adapted to draw an arc in said first passageway, a second passageway substantially transverse of said first passageway, means for supplying a blast of gas under pressure to said second passageway, and means for limiting the energy of the are drawn between said relatively movable contacts comprising a pair of electrodes mounted in said second passageway downstream from said contacts, one end of each of said electrodes being spaced from said contacts and from the corresponding end of the other of said electrodes, the other end of each of said electrodes being more remote from said contacts than said one end, and conducting means respectively connecting said other ends of each of said electrodes to different contacts to define aloop circuit for the current after transfer of the arc to said electrodes by the action of the gas blast during a circuit interrupting operation, thereby to limit the length and energy of the are.

2. A fiuid blast electric circuit breaker of the cross blast type comprising an arc extinguishing chamber including a first passageway therethrough, a pair of relatively movable contacts adapted to draw an arc in said first passageway, a second passageway substantially transverse of said first passageway, means for supplying a blast of fiuid under pressure to said second passageway, a, pair of branch passageways in said chamber terminating at the intersection of said first and second passageways, an electrode in each of said branch passageways, one end of each electrode being spaced from said contacts and from the corresponding end of the other electrode, the other end of each of said electrodes being more remote from said contacts than said one end, and conducting means respectively connecting said other ends of each of said electrodes to difierent contacts to define a loop circuit for the current after transfer of the arc to said electrodes by the action of the fluid blast during a circuit interrupting operation.

3. A gas blast electric circuit breaker of the cross blast type comprising an arc extinguishing chamber including a first passageway therethrough, a pair of relatively movable contacts adapted to draw an arc in said first passageway, a second passageway substantially transverse of said first passageway, means for supplying a blast of gas under pressure to said second passageway, a pair of branch passageways in said chamber terminating opposite the intersection of said first and second passageways, an electrode in each of said branch passageways, each electrode having a portion thereof disposed near the entrance of the branch passageways and another portion thereof downstream from the entrance of the branch passageways, and means for respectively 7 inbroonneetinathedownatmmportlonofelch lhnnbu' F eioctmde and a dines-ant one of said contacts.

Ram M Ruppei May 18, 1933 Ruppel Feb. 13, 1934 Clerc Dec. 18, 1934 Clare Aug. 4, 1936 Clerc Aug. 4, 1986 Rankin July 21, 1942 All"! et a1. Oct. 13, 1942 Baker et :1. Am. 4. 1944 Blepian May 23, 1944 FOREIGN PATENTS Country Date Great Britain Nov. 25, 1930 Germany July 'I, 1938

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