US2077276A - Circuit interrupter - Google Patents

Description

April13,1937. f J sLEPlAN `2,077,276

CIRCUIT INTERRUPTER Original Filed Oct. 13, 1931 WITNESSES; 43 lNvl-:NToR' ATTORNEY Patented Apr. 13, 1937 'PATENT' OFFICE 2,077,276 n CIRCUIT INTERRUPTER Joseph Silepian, Pittsburgh, Pa., assignor to Westinghouse Electric & Manufacturing Company, a corporation of Pennsylvania,

Application October 13, 1931, Serial No. 568,554 Renewed October 1, 1935 45 Claims.

My invention relates to circuit interrupters and more particularly to the type in which the arc is drawn in and expulsion chamber through which a blast of gas is passed to extinguish the arc.

AnY object of my invention is to provide a circuit interrupter in which a deionizing blast of gas for extinguishing the arc is caused by the decomposition of a solid material which gives off a non-inflammable condensable gas when acted on by the arc. This may be accomplished by using blocks of boric acid which give oi water vapor 1n large quantities when acted upon by the arc. Boric acid is a most desirable material for this purpose due to the fact that it may be compressed into solid cakes which may be arranged along the arc path. Further advantages of the use of boric acid lie in the fact that it is non-hygroscropic so that it maintains its insulating properties Where the air is damp, and in that it remains a good insulator even when its surface is molten.

Another object of my invention is to provide a circuit interrupter in which the arc is drawn between a pair of closely spaced Walls which reduce the cross section of the arc and cause it to take the form of a thin sheet having a large area of contact with the Walls, thus providing surfaces which aid the deionization of the arc. In addition, the closely spaced walls provide that a maximum amount of material is in contactwith the arc so that it may be decomposed, giving off a large volume of gas to extinguish the arc by causing turbulence, so that quantities of cool, unionized gas are in-mixed with the hot arc gases to deionize them.

A further object of my invention is to provide a circuit interrupter of the expulsion type which is open at one end only so as to cause a longitudinal flow of gas through the arc stream to deionize it.

A further object of my invention is to provide a condenser over the opening from the expulsion chamber so as to condense the gases which are expelled. This makes it possible to make the circuit interrupter completely closed, and at the same time avoid building up high pressures Within the arc chamber. A further advantage of this construction lies in the fact that there are no gases exhaustedfrcm the device so that there is no danger of ilash-over due to the hot ionized gases coming in contact with adjacent apparatus. This use of a condenser makes possible a completely closed device without sacricing the advantages of a flow of gas through the arc, out the end of an expulsion chamber.

(Cl. 20D-144) In general, the circuit interrupter of my invention comprises a tubular enclosing member which is lined on the inside with solid members of boric acid having rectangular openings therethrough. A fuse element or a movable contact rod is actuated by any suitable means through this opening to draw the arc. The arc isthus drawn in contact with the walls of the boric acid members causing the boric acid to be decomposed and give oif water vapor which flows longitudinally through lo the arc and out the end of the expulsion chamber into a closed condenser secured to the end of the tubular enclosing member.

The circuit interrupter of my invention has important advantages over circuit interrupters which use oil as the arc extinguishing medium in that the oil is inflammable, thus causing a considerable re risk, and also provides amuch simpler structure, since no tanks for holding the oil are required. Another important advantage over oil 2 circuit breakers, and over circuit interrupters in which the expulsion action is obtained by decomposition of ber, is that the gas given oil with the circuit interrupter of my invention is not inammable and is condensable which is not true 25 of the gases given ofi from either oil or organic insulating materials such as fiber. An analysis of the gases given off from fibre shows that they are largely hydrogen and carbon monoxide, which are permanent gases not readily condensed and are inammable.

My circuit interrupter gives a much desired improvement over devices which use water in the liquid state as the arc extinguishing medium. in that liquid-tight containers must be provided for the Water, and that the liquid water evaporates thus making it necessary to continually replace itin order to keep the circuit interrupter in readiness to extinguish an arc at any time. My circuit interrupter is also desirable in that it is entirely self-contained and does not require the use of storage tanks for holding compressed gas for the purpose of extinguishing the arc. Devices using a supply of compressed gas are always dangerous, due to the fact that the' supply of gas 45 may fail at just the time when it is necessary to extinguish the arc.A

These and other objects and advantages of my invention will be more fully apparent from the following description of the drawing which illustrates a specific embodiment of the invention, andin which Figure 1 is a longitudinal sectional view through a fuse constructed according to the principles of my invention.

Fig. 2 is a transverse sectional view through the condenser of Fig. 1 taken on the line II-Il'. thereof.

Fig. 3 is a transverse sectional view through 5 the arc extinguishing chamber taken on the line III-III of Fig. 1, and

Fig. 4 is a partial longitudinal sectional view similar to Fig. 1 but showing a circuit vbreaker constructed according to my invention.

1o The fuse illustrated in Figs. 1. 2 and 3 comprises an outer tubular casing 5 of fibre or any other suitable insulating material and has metal terminal members 1 and 9 to which electrical connection to the fuse is made. The terminal member 1 comprises a cap which is suitably secured to the tube 5, as by a screw thread, and is provided with an opening Ii in the end thereof. The cap 9 is removably secured to a sleeve I3 which is suitably fastened, as by a screw thread,

to the tubular casing 5.

Within the bre tube 5 is placed a plurality of cakes I5 of an insulating material which has the property of providing anon-inflammable, condensable gas when acted upon by an arc. While various materials may be used to provide the deionizing gas, it has been found that materials such as boric acidy gypsum, and ammonium alum give desirable results. 0f these materials it has been found that boric acid is by far the most desirable, since its properties are such as to give best results. It has been found that boric acid may be readily compressed into cakes by the application of pressure and that these cakes have such mechanical strength that they may be used in circuit interrupters without diiilculty. When boric acid (H3303) is acted upon by the arc, it is decomposed giving off water vapor (H20) leaving boric oxide (B203). Boric acid also has the advantage that it is an extremely good insulator and that it retains its insulating properties even when it has been heated to a high temperature and is in a molten state. Another very desirable property of boric acid is that it is non-hygroscopic, thus repelling water so that it does not lose its insulating properties when placed in a humid atmosphere.

' For some applications, it has been found that a desirable material for giving off the deionizing gas is gypsum (CaSOiZHzO) which is a calcium sulphate having water combined therewith. 'This material is decomposed by the arc giving oi water vapor (H2O), sulphur dioxide (S02) and oxygen (02) leaving a solid calcium oxide (CaO) While gypsum does not give results anywhere near as good as boric acid, it may be used in circuit interrupters where very high interrupting capacities are not necessary.

Another material which may be used in some constructions is ammonium alum 6 (Ammin son 4241120).

This is decomposed by the arc giving oft water vapor (H20), sulphur dioxide (S02), ammonia (NH3) and leaving the solid aluminum oxide (A1203). In general, ammonium alum is not as satisfactory a material as boric acid due to the fact that it is necessary for the un-decomposed portions of the walls of the gas generating members to withstand the full circuit voltage after the arc is extinguished, with the passage of little current. It therefore must be a good insulator,

. not only when cold, but also when at the high temperature at which rapid decomposition takes place, since the surface of the material will be at this high temperature at the momfnt arc exacvm'ro tinction takes place. Ihis explains why boric acid is more eective than ammonium alum. since boricL acid has a high resistivity even at a temperature of several hundred degrees centigrade at which it decomposes rapidly. Ammonium alum is superior to boric acid from the standpoint of volume of gas evolved but when tested in an expulsion lfuse of the type illustrated, it is much inferiorl as to its voltage interrupting capacity. While ammonium alum is a good insulator when cold. it melts at 89 C. and becomes a good conductor. It loses water rapidly at C. so that this may be taken for the temperature of rapid decomposition. This means that the surface left immediately after the arc extinction will be an electrically conducting lm of the molten salt which will break down under voltage and restart the arc, unless especial constructions are used to provide other insulation along the arc path. It is thus seen that boric acid is a most desirable material and gives the highest voltage interrupting capacity due to the fact that it combines all of the desirable properties which such an arc extinguishing material should have.

Each of the blocks of arc extinguishing material I 5 is provided with an opening I1 in the shape of a rectangle which is of several times greater breadth than width, and is of such width that it constricts the cross section of the arc and causes it to spread out in the form of a thin sheet so that there is a large area of the arc in intimate contact with the cold walls of the boric acid. This large surface aids the deionization of the arc and in addition makes possible the rapid decomposition of the boric acid or other arc extinguishing material so that a large quantity of deionizing gas is evolved. Experimental results show that such a narrow rectangular cross section is much superior to a circular section, for example, tests have been made with a slot 1A," x 1%" showing that 2100 volts per inch could be interrupted at 450 amperes while a hole with a circular section of the same area having a diameter' of 0.53 inch was able to interrupt only 400 volts per inch. 'Ihis shows that the rectangular section was over ve times Aas effective as the circular section.

The rectangular openings I1 in the boric acid blocks I5 are all alined and form a long, narrow chamber in which the arc may be extinguished. A fusible element I9, having a reduced section 2| which is melted upon the occurrence of excess current, extends through the chamber formed by the openings I1 and extends through the opening II in the cap member 1 and is fastened to the cap member at 23. The other end of the fusible element is connected at 25 to an annular collar 21. A compression spring 29 is placed between the collar 21 and a washer 3| at the end of the boric acid disks I5. Electrical connection is made to the fuse I9 from the terminals 9 and I3 by means of a disc 33 which is secured between the sleeve I3 and the cap 9 and a conductor 35 which makes sliding contact with the collar 21.

When the fuse element I9 is ruptured at the reduced section 2i, the spring 29 withdraws the fuse Ielement from the arc extinguishing chamber formed by the openings I1 and draws the arc in contact with the narrow walls of boric acid. The lower end of the chamber I1 is substantially closed by the fuse element so that the gas given off y'hy the arc extinguishing material is caused to ilow longitudinally through the arc and out the opening Il in. the lcap l. A condenser which comprises a closed container 31 is secured tothe cap l. thus totally enclosing the opening il from thelarc extinguishing cham-ber. The condenser Il is provided with a large number of metal tubes 3l which remain relatively cold and condense the gases given ofi' byl the arc. extinguishing material after it has 1o passed through the arc.

condenser makes possible an expulsion fuse which is totally enclosed, since thev gas Vgiven olf by the arc extinguishing material I6 is condensable at temperatures and pressures which are found in such a fuse, thus. reducing the pressure in the condenser and making possible the ilow of a large volume oi' gas even thoughlthe' device/ is totally enclosed. 'I'his prevents hot ionized gases from being expelled from the fuse and eliminates all danger from dash-over due to the ionized gases coming in contact with adjacent apparatus. At the same time 'the' operation of the fuse is made extremely' quiet as compared with the explosive sound which usually accompanies the blowing of an expulsion fuse.

In Fig. 4, wherein parts similar to Fig. l are indicatedI by similar reference characters, there is illustrated the'application of my invention to. a circuit breaker by the substitution 01,

a pair of contact members 4I and a movable contact rod 43 for vthe fusible element shown in Fig. 1. The contact members 4i. are biased together by springs l5 which makecontact with the movable contact rod 43 when inthe closed circuit position. The springs 45 are of such dimensions that they do not cause the contact members 4i to close the opening Il in the cap member 1. The movable contact rod I3 may be actuated to open position bya spring as shown in Fig. 1 and may be provided with a device for holding the contacts in closed position. or may be actuated by anyrwell known circuit. breaker operating means.

While I have shown and described a speciilc embodiment of the invention, it is understood that many modiiications and changes may be made without departing from the spirit of the invention as defined in the following claims.

I claim as my invention:v

1. In a device the normal function of which is to interrupt an electric current, means between which' an arc is established and arc extinguishing means including a solid member adjacent the arc c when acted upon. by the arc gives. oil? gas substantially all of which is non-innammable, and means for preventing the free eiiiux of the major portion of said path, said member being of a material which 2. In a device the normal function ofwhich is to interrupt an electric current, means between which an are is established and arc extinguishing means including closely spaced walls betweenV which the arc plays, the innersurface of said- Y structure including The provision ofthe thev apparatus, and having a quantity of boric acid along the arc path lan arc, means along said i evolving a gas substantially all of which is nonvfor generating a lis non-inflammable upon gas from said member without ilowing through the arc path.

4; In a circuit interrupterfan arc extinguishing generates gas substantially all of which is noncircuit and means'for preventing the free eillux of gas from said members except into said opening.

5. In a device the normal function of which is to interrupt a circuit. means between which an arc is established, and an arc extinguishing device having a pair of closely spaced walls between which the arcl plays, said WallsV being of an inor-.

ganic, non-hygroscopicmaterial which gives olf a non-inflammable gas when acted upon by the arc and leaves a surface whichfis a good insulator at high temperatures and an impervious wall 'about said spaced walls. f

6. In electrical apparatus, means between which-an arc plays in the normal functioning of an arc extinguishing device to aid the extinction of the arc.

.7. In a circuit interrupter, means for causing arc for continuously innammable in response to the presence of said arc as long as the arc plays and means for causing said gas to flow longitudinally through the arc to extinguish it.

8. In a. circuit interrupter, an expulsion chamber open at one end, means for causing an arc in said chamber, and solid means in said chamber gas substantially all of which the occurrence of said arc to aid its extinction.

9. In a circuit interrupter, an insulating tube open at one end, ,electrical terminal members adjacent the ends of said tube, means within said tube for interrupting the circuit between said terminal members and causing an arc, and a solid `insulating material adjacent the path of said arc a pair of closely spaced c one or more members of a material which'when acted upon by the arc walls, conducting means electrically connected in the circuit to be interruptedA extending between said walls, said conducting means being separable andvhaving means for relatively moving itsparts to drawan, arc in contact with said walls, and said walls being of boric acid for giving oif a gas when said arc is drawn to extinguish the arc.

12. In a circuit interrupter, an arc extinguish-` ing structure including a 'pair of closely spaced walls, means for causing an arc between said walls, the breadth of the space betweensaid walls being several times the distance therebetween, and said distance between so small las to cause the arc to take the formof a thin sheet with a large area said walls, a portion of said walls beingof va material which gives oil` axgas substantially. all of which is non-inflammable to aid the extinction of the arc and an impermeable wall about said arc path. v

the walls beingy in contact with lil) 413. In a circuit lnterrupter. a rectangular expulsion chamber closed on its sides by walls and aving one end open, the distancebetween an opposing pair of said walls being so small as to cause the arc to take the form of a flat sheet with a large area in contact with said walls, a portion of said* walls being of a material which gives off a gas Isubstantially all of which is noninammable, and said chamber causing said gas to now through the arc and out the open end of the chamber to extinguish the arc.

14. In a circuit interrupt/er, means for causing an arc, solid means for supplying water vapor to the arc, and a condenser for condensing said water vapor.

15. In a circuit interrupter, means for causing an arc, means for supplying an arc extinguishing gas to the arc, and means for condensing said gas, said condensing means being substantially enclosed to prevent escape of said gas and said means for causing the arc having all operating parts thereof within the enclosure preventing escape of said gas.

16. In a circuit interrupter, an arc extinguishing structure comprising an elongated tube open at one end thereof, means within said tube for causing an arc therein, means for causing a blast of a condensable non-metallic gas through the tube to extinguish said arc, and a closed condenser connected to the open end of said tube.

17. In a circuit interrupter, means adjacent the arc path which evolves a gas when acted upon by the arc, substantially all of said gas being nonmetallic, non-inflammable and in the'liquid state when cooled to room temperatures, and a condenser for condensing' said gas.

18. In a circuit interrupter, means for causing an arc, and an arc extinguishing structure having a solid member adjacent the arc, said member being of material which gives oi a'non-inammable, non-metallic gas when acted upon by the arc, said gas being condensable at room temperatures and means for condensing said gas.

19. In a circuit interrupter, means for causing an arc, and a cake of solid. material along the arc path which when acted upon by the arc gives off water vapor to extinguish the arc, and a device for condensing said water vapor.

20. In a circuit interrupter, an expulsion charnber open at one end, means for causing an arc in said chamber, and solid non-metallic means in said chamber for generating a non-inflammable, condensable gas upon the occurrence of said arc to aid its extinction, and a condenser closing the end of said expulsion chamber.

21. In a circuit interrupter, an insulating tube open at one end, electrical terminal members adjacent the ends of said tube, means within said tube for interrupting the circuit between said terminal members and causing an arc, and non-metallic means along the path of said arc for causing a blast ofk a condensable gas substantially all of which is non-inflammable longitudinally through the arc and out the open end of the tube, and a condensing device at the open end of said tube.

22. In a circuit interrupter, an arc extinguishing structure, including a pair of closely spaced walls, conducting means electrically connected in the circuit to be interrupted extending between said walls, said conducting means being separable and having means for relatively moving its parts to draw an arc in contact with said walls, and said walls being of boric acid for giving ol a gas when said arc is drawn to extinguish the arc, and

a device for condensing the gas given of! by the borlc acid.

23. In a circuit interrupter, an arc extinguishing structure including a pair of closely spaced walls, means for causing an arc between said walls, the breadth of the space between said walls being several times the distance therebetween, and said `distance between the walls being so small as to cause the arc to take the form of a thin sheet with a large area in contact with said walls, and a portion of said walls being of a material which gives off a gas which condenses at room temperatures to aid the extinction of the arc, and means for condensing said gas.

24. In a circuit interrupter, an insulating tube open at one end, electrical terminal members adl jacent the ends of said tube, one or more members of boric acid in said tube, a rectangular opening extending through said members of boric acid, said rectangular opening having a breadth several times its width, conducting means electrically connected to said terminal members and extending through/said rectangular opening, said conducting means being separable and having its parts relatively movable to draw an arc in said opening, the breadth of said opening being so small as to cause the arc to take the form of a thin sheet with a large area in contact with the walls of said opening in the boric acid for causing Water vapor to be evolved and flow longitudinally through the arc out the open end of said tube, and a condensing device enclosing said opening at the end of the tube for condensing the water vapor.

25. In a circuit interrupter, means for causing an arc adjacent to a solid material which has the property of decomposing under the influence of heat to evolve a gas and of recombining with said gas when cooled to the vicinity of room temperature, and means for condensing said gas. 26. In a circuit interrupter, means for causing an arc adjacent to a solid material which has the property of decomposing under the inuence of heat to evolve a gas and a substantially unvented chamber enclosing said means and said material, said gas being condensable when cooled to the vicinity of room temperature, and means for condensing said gas.

27. In a device the normal function of which is to interrupt an electric current, means between which an arc is established and arc extinguishing means including a solid member adjacent the arc path, said member being of a material which when acted upon by the arc gives oil water vapor` only, and means for preventing the free eiilux of i the major portion of said water vapor from said member without flowing through the arc path.

28. In a device the normal function of which is to interrupt an electric current, means between which an arc is established and arc extinguishing means including a cake of solid material along the path of said arc, which when acted upon by the arc gives off gas substantially all of which is water vapor, an impermeable wall about said arc path, andfmeans for causing said water vapor to ow through the arc to extinguish it.

29. In a device the normal function of which is to interrupt an electric current, means between which an arc is established and arc extinguishing means including a pair of closely spaced walls between which the arc plays, said walls being of an inorganic, non-hygroscopic material which gives olii a non-inflammable gas when acted upon by the arc and leaves a surface which is a good insulator at lhigh temperatures, an impervious wall about said spaced walls and means for causing said gas to ow through the arc to extinguish it Y through the arc to extinguish it.

31. In a device the normal function of which is to interrupt an electric current, means between which an arc is established and arc extinguishing means including a solid member adjacent the arc path, said member being of a material which when acted upon by the arc gives oif gas substantially all of which is non-inflammable, means for preventing the free eiilux of the major portion of said gas from said member without flowing through the arc path, and means for causing said gas to flow through the arc path.

32. In a device the normal function of which is to interrupt an electric current, means between which an arc is established and arc extinguishing means including a solid member adjacent the arc path, said member being of a material which when acted upon by the arc gives off gas substantially all of which is non-infiammable and which is an insulator of high resistance at elevated temperatures, and means for 'Y preventing the free elux of the major portion of said gas from said member without flowing through the arc path.

33. In a circuit interrupter, an entirely enclosed chamber, means for initiating an arc adjacent to one end of the chamber, cooling means positioned within the end of the chamber adjacent which the arc is initiated, and means for causing a flow of fluid toward the end of the chamber where the arc is initiated and into said cooling means.

34. In a circuit interrupter, an entirelyenclosed chamber, means for initiating an arc adjacent to one end of the chamber, movable means for drawing said arc toward the other end of the chamber and all moving parts of said arc drawing means being within saidgenclosed chamber, cooling means positioned within the end of the chamber adjacent which the arc is initiated, and i means for causing a flow of uid toward the end of the chamber where the arc is initiated and into said cooling means.

35. In a circuit interrupter, a tubular member of insulating material, an electrical terminal adjacent each end of the tubular member, said tubular member being closed at one end and having a normally closed chamber containing cooling means positioned over the other end thereof, means within the tubular member for normally completing a circuit between said electrical terminals and for initiating opening of the circuit and causing an arc at a point adjacent said cooling chamber, and means for causing a ow of fluid along the tubular member toward the point where the arc is initially caused and into said cooling chamber.

36. In a circuit interrupter, means of insulating material having a tubular passage therethrough, an electrical terminal adjacent each end of the tubular passage, means for normally closing each end of the passage, said closing means for one end of the passage comprising a normally closed metal cooling chamber containing a'plurality of metal cooling members, conductingv means extending through the tubular passage, said conducting means being separable for causing an arc, means for elongating said arc in the direction away from said cooling chamber., and means for causing a blast of uid along the tubular passage and through the arc in the direction toward said cooling chamber.

37. In a circuit interrupter, means of insulating material having a tubular passage therethrough, an electrical terminal adjacent each end of the tubular passage, means for closing each end of the passage, said closing means for one end of the passage comprising a closed metal cooling chamber containing a plurality of metal cooling members, conducting means extending through the tubular passage, said conducting means having a fusible section adjacent the end of the tubular passage closed by said cooling chamber for causing an arc, spring means within the tubular passage for moving one part of said conducting means and drawing the arc back into the tubular passage away from said cooling chamber, and means for causing a blast of uid through the arc in the tubular passage and into said cooling chamber. t

38. In a circuit interrupter, means for causing an arc, means for supplying an arc extinguishing gas to the arc, and means for condensing said gas, said condensing means including means having a large number of spaced portions providing a large area of surface to contact with the gas and cool it and being normally enclosed by a wall member directly surrounding said means providing the large area of surface, and said means for causing the arc having all operating parts thereof within the enclosure formed in part by said wall member of the condenser.

39. In a circuit interrupter, an arc extinguishing structure having a restricted opening therein for confining the arc, conducting means electrically connected in the circuit to be interrupted extending through said restricted opening, said conducting means being separable and having spring means for relatively moving its parts to draw the arc in contact with the wall of said restricted opening, and said wall when acted upon by the arc giving oi substantially entirely water vapor to extinguish the arc, and a condenser for condensing said water vapor.

40. In a circuit interrupter, means having a restricted passage therethrough of such small cross section as to hold the arc to a definite path and prevent it from bowing substantially in a lateral direction, means for causing an arc in said restricted passage, means for causing a blast of gas through the restricted passage to extinguish the arc, and a cooling chamber at one end of the passage and into which said gas ows, said cooling chamber comprising a chamber largely i-llled with metallic means having interstices providing a large surface area to contact with the arc gases, and said chamber being closed at least during operation of the circuit interrupter under ordinary overloads.

41. In a circuit interrupter, means of insulating material having a restricted passage therethrough for confining the arc to a denite path, separable conducting means extending through said restricted passage, a spring for separating said conducting means and establishing the arc in said passage, means for causing a blast of gas through the restricted passage to extinguish the arc, said restricted passage of insulating material holding at least one portion of the arc directly in the path of said blast of gas, and la cooling chamber at one end of the passage and into which said gas ows, said cooling chamber comprising a chamber which is closed at least during the occurrence of ordinary overloads and having therean arc, means oi solid insulating material deflning a restricted passage in which the arc plays, said passage having means for liberating water vapor when the arc plays therein and said passage being so narrow as to hold the arc in a substantially xed path and causing the water vapor to iiow through the arc with an expulsion action, and acondenser into which the water vapor flows to be condensed.

44. In an arc extinguishing device, a tubular member of insulating material permitting a flow of uid out therefrom and a quantity of boric acid in said tubular member of insulating material.

45. In a device for a circuitinterrupter, a tubular member of insulating material, means for establishing an arc in said tubular member, a quantity of boric acid in said tubular member, and said tubular'member permitting a ow of iiuid out one end thereof when the arc is drawn. l

JOSEPH SLEPIAN.

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