US2095729A - Circuit interrupter - Google Patents

Description

Oct. 12, 1937. H, BEIERsDoRF CIRCUIT INTERRUPTER 2 Sheets-Sheet. l

Filed March 8, 1935 I WITNESSES:` 606 ATTORNE Oct. 12, 1937. H, BElERSDORF 2,095,729

CIRCUIT INTERRUPTER 'WITNESSE INVENTOR Patented Oct. l2, 1937 UNITED STATES PATENT OFFICE CIRCUIT INTERRUPTER Application March 8, 1935, Serial N0. 9,980 In Germany March 22, 1934 7 Claims.

My invention relates to circuit interrupters and particularly to high capacity circuit breakers which utilize arc extinguishing structures of the expansion type.

It is well known in the art that the extinction of alternating current arcs may best be effected during the occurrence of a zero point in the current wave. In fact, the interruption of a power circuit at a time other than the zero point in the current wave is apt to produce Very undesirable transient surges, which may cause serious damage to other equipment connected into the circuit being interrupted.

The expansion type arc extinguisher is particularly designed to efiect the extinction of, arcs at the zero point in the current wave. Devices of this type depend for their operation upon the fact that an unionized molecule or atom is capable of attracting electrons or charged particles of matter thereto, and that it is much more ldiilcult to reionize an arc stream which contains comparatively few electrons per unit volume than it is to reionize one which contains a large number of electrons per unit volume, the theoretical explanation oi these experimentally proven facts being that reionization is usually brought about by the collision of electrons and molecules, and that the voltage necessary to impart sufficient velocity to an ion in order to bring about ionization by collision is much higher than for electrons. The expansion principle of arc extinction consists, therefore, in the provision of means whereby the arc stream may be surrounded, and turbulently intermixed with a large quantity of unionized gas or fluid during the period of cir* cuit interruption, this large amount of unionized fluid causing the free electrons in the arc stream, at the time of a zero point in the current wave, to attach themselves to a molecule or atom and thereby become sufficiently immobile to prevent reionization by collision as the voltage restores itself on the circuit.

It has been found that the most eiective means for producing this combination of free electrons with molecules or atoms consists in the turbulent intermingling of the arc stream with a quantity of arc extinguishing uid in the vapor state, this state yielding the largest possible number of unionized molecules or atoms per unit volume with maximum mobility of those molecules. In one form of expansion arc extinguisher, the arc is drawn within a closed pressure chamber, the Walls of which are formed by a stack of superposed contiguous laminations. A quantity of an arc extinguishing liquid which is capable of being vaporized, without breaking down into its constituent elements or compounds, is disposed within this pressure chamber, and the device is so arranged that the gas evolved by the arc from the liquid is allowed to expand adiabatically during the progress of the circuit opening operation. Since all of the heat imparted to the gas came from the arc and exists in the gas in the form of pressure energy, the free expansion of that gas during the arc extinguishing operation`wil1 lo cause it to condense and thus surround the arc stream with a quantity of arc extinguishing gas in the vapor state.

In the operation of these devices in the past, it has been found diiiicult to cause the expansion to persist over a sufliciently long period of time to assure that the arc stream shall be surrounded by arc extinguishing fluid in vapor state during at least one zero point in the current wave, and the rimary object of the present invention is to provide means for overcoming this diiiculty and thereby assuring satisfactory operation of the device under substantially all conditions.

A further object of the invention is to so design the laminations which are used in building up an arc extinguishing structure of the type discussed above that storage reservoirs shall be provided for the gas which is evolved from the arc extinguishing liquid or other source of arc extinguishing gas during the operation of the device.

Another object of the invention is to provide means for simplifying the structure of an expansion chamber, the walls of which are dened by a stack of separable, contiguous laminations, by providing means integral with the separable laminations for causing those laminations to automatically realign themselves following each operation of the breaker, and a still further object of the invention is to generally simplify and improve the structure of expansion type arc extinguishers in order to decrease the cost of manufacturing those devices and to improve their operation.

In carrying out these objects of my invention, I provide an expansion type of arc extinguishing structure which comprises a plurality of. superposed, contiguous laminations for dening the walls of an arc passage, means for establishing the arc incident to the opening of the associated interrupter Within that passage, and means for so supporting the laminations that they are separable upon the development of suiiicient pressure within the arc passage to permit a free expansion of the arc extinguishing gas evolved therein. The laminations differ from those inthe prior art Vstructures in that they take the form of casings having secondary pressure chambers formed therein, these secondary pressure chambers serving as storage spaces for the gas evolved during the operation of. thedevice, and the various elements'of the interruptor are so correlated, with regard-'to these pressure chambers, that anY adequate supply of arcextinguishing fluid in the vapor state is made available during at least onercurrent zero point. In one form Vof the invention, the laminations engage each other with-cooperating conical seats in order that they shall automatically realign themselves folj lowing each venting operation. Two specific embodiments of my invention are illustrated in the accompanying drawings, wherein Figure l is a side elevational view of a circuit Y.breaker utilizingan arc extinguishing structure Fig.V 2 is a iront elevation constructed according to the invention;

view'oi'the circuit breaker shown in Fig. l. .Y f .Y

Fig. Sis an enlarged sectional viewthrough the expansion type arc extinguisher forming a partei the'brealrer illustrated in lgs. 1 and 2.

Fig. e is Yav sectional view taken on the line YIv--iv or Fig. s.V Y f Fig. 5 is a'sectional view, similar to Fig.Y 3, of a modified iornrof my invention suitable for useV with the breaker shown in Figs. 1 and 2.

F'Qg. 6 is a sectional view on the line VI-Vloi Fig. 5, and Y Fig. 7 is a fragmentary, perspective view showing thedetails of the mounting means-for the cover or" the arc extinguisher shown in Fig. 5,

Referring particularly to Figs. l and 2, the circuit. interruptor therein illustrated comprises an L-shaped base l, a movable contact 3, an operating mechanism 5 therefor, which is mounted onrthe base i by means of a pair of insulators l,

'an arcV extinguishing structure il ior cooperating with the movable contact 3, and a third insulator column Vil for supporting the arc extinguishing structure 9 on the base l. The interruptor is provided with a pair of suitable Vterminals l for connecting Yit into an electrical circuit.

vThe movable contact 3 in this embodiment of my invention comprises a cylindrical rod member which is adapted tomove through the arc extinguishing Vdevice Si when opening and closing Y the circuit. The operating mechanism 5 for this contact rod is not an important part of the present inventiornand any ofV the mechanisms which are alreadyknown inthe art may be employed.

The arc extinguishing-device 9 includes a baseV member i5 of metallic material which is engaged by a hollow cylindrical casing Il forming the outer wall of the arc extinguishing device. The upper end of this casing il is closed by a cap -member i9 which is provided with a suitable opening 'El for permitting the passage oi the contact rod 3 therethrough and with vent openings 23 forpreventing the development oi unduly large 'pressures within thercasing itself during theop- Veration of the arc extinguisher. A. quanttyofV movable contactV rod, this guide being supportedl used Y adjacent Vthe upper endrof the hollow cylindrical member 25 by suitable arms 3 l. The piston mem- Y ber 2l comprises the main current carrying contact, and it isfbiased in the direction oi thecontact rod 3 byfour equally spaced springs memberi';7 also serves as a means for causing the introduction ci a quantity of the arc extinguishing liquidV 'l into the upper portionsV of Vthe arc -ssa-ge during each operation of the device, as

. be explained in detail later.

VAs mentioned previously, the arc extinguishing structme proper comprises a pressure chamber having an arc passage, through which the contact rod 3 moves, extending therethrough. The walls of the upper portion of the arc chamber are dened by a Yplurality or .superposed contiguous laminations 35, which are positioned immediately above the hollow cylindrical member 25, an in-Y sulating support member 3l being interposed be- VV tweenthe lowest lamination 35 and the upper intothe main are passage. Y The upper lamination.

is held in place by a suitable molded member il ThisV whichengagesl the cap member i9 through an annular member formed of rubber or other resilient material. rl`his resilient member i5 serves Y to permanently bias the laminations 35 toward cach other, while, at the same time, permittingY those lamination-S to separate a delinite amount upon the production of sufficient pressure withthearc chamber Vin orderto form vent openings inthe walls thereof. I Y

The superposed laminations 35 engage each other with cooperating conical seats d5 formed integral therein. This arrangement allows the free separation oi the laminations 35 during each venting operation, while, at the same time, it makes the stack self-centering assuring a proper realignment of the laminations when the pressure Within the arc passage has been reduced to its normal value.

The portion of the arc passage which is dened by the superposed laminations 35 is located entire- 'V ly above the normal level oi'the body of arc extinguishing liquid Zilwhich is contained within the main casing il. In order to assure a rapid evolution of gas during each' arc extinguishing operationyitis desirable to introduce a predetermined quantity of. this liquid into the upper portion of Y the arc chamber, and, as mentioned above, the movable contact 2'! is employed for this purpose. This contact El' moves as a piston within the hollow cylindrical member 25, and is provided with a pair of nap valves :il normally biased to the position shown in Fig.l3, these'valves serving Vto cover openings Il@ extending through the piston Contact member 25. Y

The lower end of the hollow cylindrical member 2l is provided with a centrally disposed opening 5i and four passages'SS connecting therewith, in

order to permit the entry of the arc 'extinguishing liquid'into'the arc chamber. rihe central Y opening 5i is normally closed by a flap valve 55 as is shown in Fig. 3. Itis apparent from an inspection of the valve land piston arrangement that the upward movement of the contact rod 3 will allow the piston contact 2'! to move'upwardly, under the biasing action of the springs 33, and will thereby cause a predetermined quantity of the arc extinguishing liquid to be moved up into CTI the arc chamber, the amount of this liquid being readily controllable by varying the stroke of the piston contact member 21. During each circuit closing operation, the valves 41 will lift and thus assure the relling of the space above the piston 21.

In order to facilitate the movement of the arc extinguishing liquid into the upper portions of the pressure chamber wherein the arc is drawn, and to attain a better distribution of that liquid between the several secondary pressure chambers 39 formed within the laminations 35, small vent openings 51 are provided for interconnecting the secondary pressure chambers 39. rlhese openings 51 are of such small diameter, however, that they do not eiect any substantial venting of the pressure chambers 39.

The circuit breaker is shown in the closed circuit position in Figs. 1, 2, and 3. Upon the occurrence of an overload or other abnormal condition, the actuating mechanism 5 is operated to move the contact rod 3 upwardly toward the normal open circuit position. This movement takes place at a relatively high speed, and, due to the retardation effect on this piston member 21 which results from the quantity of liquid entrapped above that member, an arc is drawn almost immediately between the lower end of the contact rod 3 and the central portion of the movable piston 21 which comprises the cooperating Iixed contact, (or if the piston 21 should follow the upward moving contact, between that member and the guide 29).

Very shortly thereafter, this arc is drawn into that portion of the pressure chamber which is defined by the laminations 35, and simultaneously with the drawing of the arc into the upper portions of the pressure chamber, a predetermined, measured quantity of the arc extinguishing liquid 24 is moved therein by the upwardly moving piston. The heat of the arc volatilizes a considerable portion of this arc extinguishing liquid, and the secondary pressure chambers 39 provide storage spaces for containing this gas as it is evolved.

By the time the rst zero point of the current wave has been reached, or if the arc current should be low by the time the second Zero point in the current wave is reached, the pressure of this gas which is entrapped within the arc passage will ordinarily reach a suicently large value to cause the laminations 35 to separate and form vent openings in the side walls of the pressure chamber through which the arc passage extends. The gas stored in the secondary pressure chambers, when venting, will flow longitudinally through the arc at high speed, and since the expansion is substantially adiabatic, this gas will return to the vapor state as it expands. The immediate result will be to eiect either a removal of the electrons and ions from the arc stream, or the combination of the free electrons with previously uncharged molecules at such a rapid rate that reignition of the arc following the occurrence of the zero point becomes impossible. The secondary pressure chambers 39 provide a suiiicient volume 0f gas so as to continue the expansion operation over a suiciently long period of time to assure the inclusion of one zero point in the current wave. The greatly increased volume of the chamber or passage wherein the arc is drawn which results from these secondary pressure chambers also serves to aid in preventing the building up of excessive pressures within the arc extinguisher during the extinguishment of the very large current magnitude arcs, and thus adds considerable to the safety and reliability of operation of the breaker.

The provision of the cooperating conical seats 45 for the laminations 35 is of great value in simplifying the structure of the arc chamber, particularly through the elimination ofany need for the provision of guide rods or the like for maintaining proper alignment of the laminations during the operation of the extinguisher. The amount of separation of the laminations 35 is denitely limited by the resilient member 43 to a, value which is not in excess of the cooperating engagement of the seats 45. Thus, immediately upon the removal of the pressure from within the arc chamber, the resilient member 43 causes the wall defining laminations thereof to reengage each other, as shown in Fig. 3, the conical seats 45 assuring a proper realignment of these members. If the connecting vent openings 51 are used, it may be found desirable to utilize means such as the interengaging guide ribs 59 shown in Fig. 4 for preventing any displacement of the laminations in an angular direction.

For most eicient operation of the device, it is desirable to utilize an arc extinguishing liquid which is not broken down into any of its chemical constituents when exposed to an electric arc. It is possible, however, to utiiize an arc extinguishing structure such as that previously described with decomposable fluids such as oil. Ii a fluid of this latter type is used, the extinguishing action resulting from the expansion oi the gas from a heated to a vapor condition is lost. However, the extremely turbulent intermixing of the arc stream with the gases evolved from even decompcsable are extinguishing iiuids which is brought about by the structure of my invention will effect the extinguishment of large current magnitude arcs with a greater degree of eiciency than the previously known devices.

The structure shown in Figs. 5, 6, and 1 is substantially similar in form and operation to the previously described arc extinguisher. It includes a` base member i?) l, which may be bolted to an insulator column similar to the base member I5 in the previously describe-d embodiment, a cylindrical casing |63 which denes the side walls of the main closure for the arc extinguishing structure, a cover for the main closure, a stationary Contact 151 affixed t-o the base IUI, and three superposed laminations m9, H0, and Il which dene the arc chamber proper. Each of these laminations, as in the previously described structure, is provided with a secondary pressure chamber H3 formed integral therewith. The three laminations are maintained in proper alignment by means of four tie-rods l I5 and are biased toward each other by means of an annular, resilient member H1 interposed between the lower lamination |09 and a thrust plate H9 which serve both to close the lower end of the chamber wherein the arc is drawn and to transmit the pull exerted by the tie-rods H5 to the resilient member H1.

Each of the laminations, as in the previously described embodiment, is preferably formed of molded insulated material and is substantially annular in outline. The secondary pressure chambers H3, one of which is formed in each of the laminations, are also substantially annular in outline and connect only with the central opening I2l which exists in each of the laminations for permitting the passage of the movable Contact rod 3 therethrough. A quantity of arc extinguishing liquid 123 is contained within the Cir i outer casingY H33 and the level of this is maintained at a sufficiently high ,value to assure theV complete lling of the chamberV wherein the arc provides vent passages leading from theV inside of Y theouter casing to the atmosphere. These vent passages are formed through the provisionV of a groove IES in the lower side of the cover member and suitable projections ist extending down-Y wardly into this groove for engaging the upper end of the cylindrical outer casing m3 so as to space the bottom of the groove above the topV of the casing H33. A detail of the groove |129 and Y one of these downwardly projecting-members i3# is shown in Fig. 7. Y This arrangement Yprovides Vventing passages of large sizewhile, at the same time, substantially preventing rain,rsnow, dirt or other foreign material from working into the interior of the arc extinguishing structure.

The operation of this modified-fornirci my invention is very similar to the Yoperation Vof the previously described embodiment. Upon the occurrence of an overload or other abnormal condition, the contact rod 3 is moved upwardly by the actuating mechanism and an arc is established within the arc passage extending through Y this chamber is volatilized, and a certain amount the pressure chamber. At least a portion of the arc extinguishing liquid 23 entrapped within of thisV vapor is stored within the secondary pressure `chambers H3. When the internal pressure existing within the pressureY chamber reaches a sufciently high value, the wall defin-V ing laminations E59, liti, and ill are separated against the biasing action of the resilient member ll'l and the gases then existing-within the arc chamber are allowed to vent through the annular openings thus created. The gases, in iiowing outwardly from the secondary pressure chambers H3, intermix turbulently with the are stream and eifect a rapid extinction of the are. If a ncn-decomposable'arc extinguishing liquid is used, the Varc extinguishing Yaction is further aided by the presencewof the arc extinguishing `huid in the vapor state.

In'the foregoing, I have pointed out the structural details of a new and improved Vare extinguishing device which is capable of much more efficient operation than the structures known to the prior art. While the invention is intended primarily as an improvement upon circuit interrupting devices which operate on the expansion principle, certain ofthe particular structural arrangements disclosed are suitable for use in 'arc extinguishing Vdevices whichY do not employ that principle.

'I'he improved arc extinguisher VVwhich I-haveV perhaps, the most important single feature of theV invention.

As a further means for improving structures oiY Ythe type under consideration, I have shown howillustrative and that variations in their preciseV form will be both desirable and necessary in; some applications.V I desire, therefore, that the language of the accompanying claims shall be accorded the broadest reasonable construction and that my invention shall be limited only by what is expresslystated `therein and by the priorart.v

VVI claim as my invention:V Y 1 I 1. Ina circuit interruptor, an arc extinguishing structure, including a plurality of superposed iaminations which define the walls of an arc passage, means for so supporting said laminations that they are separable upon the occurrence-of predetermined conditions to create vent openings in the walls or" said arc passagel and meansV for establishing-the arcincident to the opening of said interruptor within said arc passage, adjacent larninations. having cooperatingseat portions so shaped that said laminations automatically realign themselves with respect to the lon,- gitudinal axis of said arc passage following each separation thereof.

2. In circuit interruptor, an arc extinguisl'iingY structure including a plurality of superposed,

contiguous laminations, each of which has a cen-v trally disp sed opening therein, for defining the walls er an are passage, resilient means normally biasing said laminations toward each other, means for so supporting said laminations that they are Yseparable upon the occurrence of predetermined conditions to form vent openings in the walis of said arc passage, and means for establishing the arc incident to the opening of said interruptor within said arc passage, at least some of said laminations engaging each other with conical seatsin Yorder that said laminations shall automatically realign themselves following each venting loperation.Y Y Y 3. In a circuit interrupter, anr arc extinguishing structure including a plurality of superposed,

Vcontiguous annular members which define the nular members being of insulating materiaL means normally biasing said annular members toward each other, means for supporting said annular members abouta common axis, said sup-k porting means permittingfsaid annular members to separate upon the occurrence of predetermined conditions to create vent openings in the walls or" said arc passage, and means for establishing the aro incident to the opening of said interrupter within said arc passage, the engaging portions of adjacent members being so shaped thatV said lamnations automatically realignY themselves about common axis followingsaid each venting operation.

Li. In aV circuit interruptor, an arc extinguishing means includin r a plurality of superposed,

contiguous laminations which define the walls of a substantially closed pressure chamber, resilient means for biasing said wall defining laminations toward each other, means for so supporting said laminations that they are separable upon the occurrence of predetermined pressure conditions Within said chamber to create vent openings in the Walls of said chamber, means disposed within said chamber, at least during each circuit opening operation, which is capable oi' evolving an arc extinguishinfr gas when placed in proximity to an electric arc, and means for establishing the arc incident to the opening ci said interrupter within said chamber, adjacent laminations having cooperating seat portions so shaped 'that said laminations automatically realign themselves under the biasing action of said biasing means following each venting operation.

5. In a circuit interruptor, an arc extinguishing means including a plurality of superposed, contiguous laminations Which denne the Walls of a substantially closed pressure chamber, resilient means for biasing said Wall deiining laminations toward each other, means for so supporting said laminations that they are separable upon the occurrence of predetermined pressure conditions Within said chamber to create vent openings in the walls of said chamber, means disposed Within said chamber, at least during each circuit opening operation, which is capable of evolving an arc extinguishing gas when placed in proximity to an electric arc, and means for establishing the arc incident tc the opening of said interrupter within said chamber, said laminations engaging each other With cooperating conical seats in order that said laminations may be automatically realigned by the biasing action of said biasing means following each venting operation.

6. In a circuit interrupter, an arc extinguishing structure including a plurality of superposed contiguous laminations which denne the Walls of a pressure chamber, resilient means normally biasing said laminations toward each other, means for so supporting said laminations that they are separable upon the occurrence of predetermined conditions to form vent openings in the walls of said pressure chamber, a body of arc extinguishing liquid, means for causing a predetermined quantity of said liquid to be entrapped Within said pressure chamber during each circuit opening operation, and means for establishing the arc incident to the opening of said interrupter Within said pressure chamber, at least some of said laminations engaging each other with cooperating conical seats in order that said laminations shall automatically realign themselves following each venting operation.

7. A circuit breaker comprising a casing, a body of arc extinguishing liquid contained therein, a plurality of separable plates of insulating material positioned above said liquid, yielding means for normally maintaining said plates in contiguous relation with respect to each other, each of said plates having an opening therethrough, said opening being aligned to define an are passage, means for establishing an arc Within said passage, and means incident to the establishing of said arc for moving some of said liquid into said passage, at least some of said plates having an annular pressure chamber surrounding the opening forming said arc passage, said yielding means being responsive to the pressure v'ithin said arc passage to enable said plates to separate to thereby provide a passage for the escape ci gas from said pressure chamber through said arc passage, adjacent plates having cooperating seat portions so shaped to automatically realign said plates after each separation thereof.

HANS BEIERSDORF.

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