US2365082A - Electric circuit breaker - Google Patents

Description

Dec. 12, 1944. G. E. JANssoN ELECTRIC CIRCUIT BREAKER Filed May 16, 1942 2 Sheets-Sheet 1 Patented Dee. 12, 1944 UNITED .STATES PATENT ori-'ICE ELECTRIC CIRCUIT BREAKER Gustav E. Jansson, North Quincy, Mass., assignor to Allis-Chalmers Manufacturing Company, Milwaukee, Wis., a corporation of Delaware I Application May 16, 1942, Serial No. 443,255

9 Claims. (Cl. 20o-148) arc is extinguished, its reignition must be prevented while the circuit is being opened permanently either by further separating the arcing contacts or by opening other contacts connected in series therewith. Reignition of the arc may Y be prevented by continuing the iluicl blast at its full intensity after interruption of the arc. This method, however, entails a large consumption of arc extinguishing fluid, which is particularly ob.

jectionable when the fluid is obtained from a source of limited capacity. As an alternative, the ilow of fluid may be stopped at the outlet of the arcing chamber to confine fluid under pressure within the chamber and about the arcing contacts. This methodalso is disadvantageous in that the arcing chamber remains filled with partly ionized fluid which is contaminated with metallic vapors and in that the contacts are not suiiiciently cooled by the confined fluid.

It is therefore preferable, as soon as the arc may be assumed to be interrupted, only to reduce the ow of fluid to such an extent that reignition of the arc may be prevented for the greatest possible length of time with the amount of fluid available. The regulation of the iluid flow should take into account the capacity of the source, its residual pressure at the time of extinction of the arc, the quantity of metallic vapors-to be removed, and the relative dielectric strength of the fluid when in motion and when at rest. The flow of fluid through the entire circuit breaker is preferably 'initiated prior to opening of the arcing contacts. The contacts are preferably so arranged that the action of the fluid blast o-n the contacts and onf the arc is assisted by the electromagnetic effect of the current.

It, is therefore one of the objects of the present invention to provide a circuit breaker of the fluid blast type in which the flow of fluid is adjusted at different values for extinguishing the arc and for preventing reignition of an arc.

Another object of the present invention is to provide a circuit breaker of the fluid' blast type in which the dielectric strength of the arc path is maintained at the highest possible value after extinction of the arc with a minimum expenditure of extinguishing fluid.

Another object of the present, invention is to provide a circuit breaker of the fluid blast type in which the extinguishing action of the fluid blast is assisted by the electromagnetic eiect of the current.

Objects and advantages other than those above set forth will be apparent from the following description when read in connection with the accompanying drawings in which:

Fig. 1 is a view in elevation, partly in cross section, of an outdoor circuit breaker embodying the present invention;

Fig. 2 is a vertical cross sectional view of the arcing chamber of the embodiment illustrated ln Fig. 1 showing the main and arcing contacts in closed position;

Fig. 3 is a fragmentary view through the arcing chamber of the circuit breaker showing the contacts in fully open position; and

Fig. 4 is a bottom end view of the movable arcn ing contact of the circuit breaker.

Referring more particularly to the drawings by characters of reference, the circuit breaker illustrated in Fig. 1 comprises a reservoir 6 constituting a source of are extinguishing fluid under pressure of limited capacity. The fluid may be an inert gas such as nitrogen, but it will be assumed herein that the fluid is air under pressure of the order of 200 or more pounds per square inch supplied to the reservoir by a suitable compressor (not shown). Reservoir B andthe other elements of the circuit breaker are supported on a suitable frame l. The frame supports the current carrying parts of the circuit breaker through insulators 3, 9. Insulator 3 supports a terminal I I and a fixed disconnecting contact I2. Insulator 9 is surmounted by a hollow conductive member I3 on which a movable disconnecting contact III is pivotally mounted. Contact I4 may be opened and closed by means of a double acting air motor I6 through a pivoted insulator I 'I and suitable gears I8.

Member I3.supports a hollow insulator I9 enclosing the main and arcing contacts of the circuit breaker. A conductive cylinder 20 mounted on insulator I9 cooperates therewith to define an arcing chamber 2 I. Cylinder 20 also contains the actuating mechanism for the main and arcing contacts and must generally be divided into a plurality of parts to permit machining of its inner working surfaces and to permit introduction of the contact actuating mechanism therein.

Cylinder carries a terminal 22 and a stop 23 for limiting the movement of contact I4. The cylinder also supports an insulating bushing 24 containing an electrode 26 extending through the cylinder top wall. The upper end of the electrode is connected with member I3 through a suitable resistor 21 which is supported on member I3 and is encased within a hollow insulator 2B.

Insulator 3 is hollow and provides a connection between reservoir 6 and arcing chamber 2i through a suitable control valve 29 and a conduit 30 for the purpose of directing a blast of arc extinguishing iiuid under pressure between the arcing contacts and through the arcing chamber.

The operation of valve 29 may be controlled in any suitable known manner and is correlated with that of motor i8 as is well known. In particular, air is preferably admitted to motor 29 from conduit 30 through a conduit 35 to cause opening of contact it after interruption of the current at the arcing contacts.

As shown in Fig. 2, arcing chamber 2i contains cooperating main contacts si, 32 and cooperating arcing contacts 33, 30. connected in parallel therewith. The main and arcing contacts are also serially connected with contacts t2, ifi through member iii. Contact 3i is a xed contact shaped as a streamlined solid of revolution and is bolted to member i@ so as to extend into the bore of insulator lli). Contact Si is bounded by a plurality of surfaces including a plane surface intersecting a convex surface of revolution Si. The cooperating main contact 32 is divided into a plurality of segments resiliently mounted on a conductive annular contact support 38. Support is coaxial with contact 3l and is bounded oy a piurality oi surfaces including a plane surface 39 intersecting a convex surface of revoiution llil. The segments of contact 32 are arranged about surface d@ and are urged thereagainst by springs so as to dene substantially a concave surface of revolution Q2. Contacts 3G, 3i? are preierably maintained in mutual engagement by means of a spring Support S8 is mounted on a sleeve it adapted to slide into the bore of cylinder 2d. An annular piston flo :mounted on sleeve ld cooperates with other elements of the circuit breaker to actuate the sleeve for opening contacts 3i, under the action of the air pressure within the arcing chamher. Piston 635 is arranged within an enlarged portion it of cylinder 2@ which is open at its lower end and which is vented to atmosphere at its upper end. The down stroke of sleeve EJI- is limited by engagement of support 3&3 with Contact 3l and the up stroke of the sleeve is limited by engagement of an annular thrust member 25 with the wall of cylinder portion llt. The conduction of current between sleeve 44 and cylinder 2li is effected by any suitable means such as a plurality of segmental sliding contacts l1 arranged in an annular recess di? oi the cylinder and resiliently held in engagement with the sleeve and with the cylinder wall.

Contact 3l is hollow and partially surrounds the so-called iixedarcing contact 33. The latter is provided with a stem portion 49 guided into a bore of contact 3i and carrying a piston 5U. The Apiston is adapted to slide within a short cylinder 5I provided within contact 3i, the portion of cylnder 5I below piston 50 communicating with the space within member I3 through an apertured baiiie 15. Contact 33 is resiliently urged upward by a spring 52 which is relatively weak compared to spring 43. Current is conducted between conaseaoea tacts 33 and 3| through any suitable means such as a plurality of flexible conductors 53.

The movable arcing contact I4 is an annular contact dening an orice 5l and is mounted on sleeve M. Means are provided, including thev dimenslonin'g of contacts 33, 34, to insure that when an arc is drawn therebetween the current through the portions of the contacts adjacent their arcing surfaces follow substantially parallel paths in opposite directions, to urge the arc to travel towards orifice 54 by electromagnetic action and thus assist the extinguishing action of the air blast. Contacts 33, 34 preferably comprise mutually engaging portions 58, 59 having substantially parallel engaging surfaces and relatively thin walls connected at their periphery to the main portion of contact 33 and to support 38, respectively. In addition, contact 34 preferably has its arcing surface subdivided by a suitable plurality of radial slots 60 to limit the circumferential spread of the arc.

When the arcing contacts are closed, contact 33 substantially closes orifice 54. The arcing contacts may then be considered as dividing arcing chamber 2l into an inlet chamber 55 and an outlet chamber 56. The inlet chamber is generally dened by insulator i8 and sleeve 44 and has its inlet at the juncture of insulator i3 with member i3. r.ihe outlet chamber is generally contained within sleeve @it and extends upward to suitable outlet means el provided on cylinder Slots [iii extend through the thickness of arcing portion 59 of contact 3ft so as to define a plurality or ports shown in Fig. fl. The slots therefore form a path for the i'iow of air from the inlet chamber into the outlet chamber through apertures 65 provided in the wall of Contact 3l.

Chamber 56 contains the lower part of electrode 2G. The electrode is preferably surrounded by a plurality of coaxial metallic baffles Si connected therewith and serving to limit the length of the arc and to cool and deioniae the air blast passing through the arcing chamber. Sleeve 44 is preierably lined with a cylinder of insulating material G2 to prevent iashovers between electrode 2S and the sleeve. A shield G3 arranged adjacent a portion of cylinder 62 prevents deposition thereon of material vaporized from the arcing contacts.

Battles Sil may be arranged within outlets 51 to assist baffles di in cooling the air blast and to prevent accidental introduction of foreign material into the circuit breaker. Spring loaded check valves t6 may be further provided to prevent circulation of dust or snow laden air from one outlet to the other through the arcing chamber.

Outlets 51 are controlled by suitable valve means G1 operable to partly close the outlets after opening of contacts 33, 34 and extinction oi the are by the air blast. Valve 61 may consist of a sleeve arranged to slide into an enlarged bore of cylinder 20 around the upper part of sleeve 44 as shown in Fig. 2. Valve 81 is normally maintained in the position shown by a spring 68 and may be actuated by any suitable means such as an annular piston 69 adapted to move in an annular space 10 provided in cylinder 20. When valve 61 is in raised position it obstructs outlets 51 incompletely to provide a path for a reduced blast of air sufilcient to maintain the arcing contacts open and to prevent reignition of the arc. This path may be defined by a plurality of ports 1| in the portion of valve 61 registering with outlets 51 or by any other equivalent means. For example, valve 61 may divert the air blast through outlets other than outlets 51, or else permanently open outlets may beprovided in addition to outlets 51.

In order toA permit accurate adjustment of the time offclosure of valve 61. the operation of piston 69 is preferably rendered responsive to the pressure within inlet chamber '55 with an adjustable time delay and independently of the operation of the arcing contacts. The lower portion of' space 10 is connected with chamber 55 through ports 12, recess 43 and a relatively narrow port 13. The ow of air through port 13 may be adjusted by means of a needle Valve 14 to delay the opening of valve 61 and to cause this opening to 'begin slowly. A relatively wide port 16 provided with a needle valve 11 connects recess 48 with an intermediate point of space 10 to cause valve 61 to close rapidly after port 18 is uncoveredby piston 69.

`as illustrated in Figs. 1 and 2, current flows between terminals II and 22 through contacts I2 and I4` member I3, contacts 3|, 32, 33, 34, support 38, sleeve 44, contacts 41 and cylinder 20. The flow of current takes place mostly through the main contacts 3|, 32 because of the relatively small area of the cooperating surfaces of arcing contacts 33, 34, of their burning by previously established arcs and of the relatively low contact pressure afforded by spring 52. Opening of the circuit breaker is initiated by opening valve 29. The valve then admits air under pressure from reservoir 6 into conduit 30, insulator 9, member I3 and the inlet portion 55 of the arcing chamber. Air pressure is thereby applied to the lower faces of pistons 45 and 50 and of contact 34, the upper faces of which are subjected to atmospheric pressure. The pistons accordingly lift" contacts 32, 33 and 34 against the action of spring 43. The

area of piston 50, which is preferably much larger than the area of aperture 54, is also large compared with the area of piston 45. The action of piston 50 is therefore preponderant in accelerating the contacts and this action also maintains ' contacts 33, 34 closed under a high pressure.

Upward movement of the contacts causes support 38 and contact 32 to disengage contact 3|. Opening of contacts 3l. 32 causes the entire flow of current to be transferred to contacts 33, 34 through conductors 53. This current transfer takes place without difficulty because the high pressure to which` contacts 33, 34 are then subjected by piston 50 causes the resistance of the arcing contacts to be very low. Air also passes through apertures 6,5 and slots 60 into outlet chamber 56, thereby setting in motion the air column contained within the outlet chamber and facilitating. thefsubsequent establishment of a blast therein upon'opening of contacts 33, 34.

Upward movement of contact 33 is stopped by engagement. of rpiston I) with the end wall of cylinder 5 Contact 33 is Athen in the position shovvnin Fig. 3.l Contacts 32 34 thereafter continueitheir upward movement as aresult lof the impulse-imparted thereto by piston 50 and of the continuedl application'of airpressure of the lower facese-.of-.piston 45 and of contact 34. Continued movement ofcontact 34 causes portion 59 thereofto .disengage portions58 of contact 33. An arc Contacts 32.34u`ltimately reach the fully open position shown in Fig.l 3 toestablisha gap between contacts 33, 34 of such width as to result in the most emcient arc extinguishing action of the air blast therethrough.

The air blast causes the arc to move from its initial position toward orifice 54. The roots o! the arc rst travel aiongthe surfaces oi' contact portions 58, 59, one root ending at the tip of contact 33 and the other ultimately traveling upward along the bore of contact 34. The arc thus sweeps through a series of positions such as the position indicated in dotted lines in Fig. 3. During this movement of the arc, the flow of current through contact portions 58, 59 follows substantially the path indicated by the arrows in Fig. 3. Thecurrent through the contactsand through the arc thus forms a loop. As is well known, such a loep tends to expand in all directions under the action of its self-induced electromagnetic field, which urges the arc toward orifice 54 and thereby assists the extinguishing action of the air blast. As the contact portions 58, 59 included in the loop form parallel paths through `which current flows in opposite directions, an electromagnetic eiect of repulsion also takes place between the contacts assisting the action of the air blast in maintaining the contacts open.

The arc looped between contacts 33, 34 ultimately reaches the tip of electrode 26 and thereupon breaks into two portions. One portion extends between contact 33 and electrode 26 and is connected in parallel with resistor 21. The resistor preferably has a resistance of value equal to substantially thirty times the so-called short circuit impedance of the circuit breaker. The short circuit impedance is defined as the circuit impedance required to limit the current through the circuit breaker to its rated interrupting capacity. It has been found experimentally that when resistor 21 has the above specified value the arc portion connected in parallel therewith is relatively unstable and is readily extinguished toward the end of the first half cycle of arcing. The second arc portion, which extends between electrode 26 and contact-,'34, is then connected in series with resistor 21. The arc current is therefore reduced to a relatively low intensity and is sub stantially in phase with the line voltage so that it is readily extinguished by the air blast. When the voltage impressed between contacts 33, 34 reverses, the steepness of its wave front is limited by resistor 21 to that of an aperiodic oscillation of the circuit. The recovery voltage impressed between the arcing contacts rises less rapidly than the dielectric strength of the gap dened by the contacts, and the air blast is therefore able to prevent reignition of the arc without difficulty.

During the above described operation, air under pressure flows from inlet chamber 55 through ports 12. recess 48, and port 13 to the lower portion of space 10. The air pressure on the lower face of piston 69 builds up at the rate depending on t'ie adjustment oi valve 14. When this pressure exceeds the effort exerted by spring 68, piston 63 moves valve 61 at a rate also determined by the adjustment of valve 14. Until piston 69 uncovers port 16 the upward movement of the valve 61 into outlet 51 does not affect materially the flow of air through the circuit breaker. This movement is preferably so regulated by adjustment of valve 14 that port 16 is uncovered by piston 61') as soon as the arc may be considered to have been extinguished. Additional air under pressure thereafter being admitted under piston 69 through port 16 causes rapid upward movement of valve 61 to the end of its stroke.

l of the arc between the arcing contacts.

The now of air through the circuit breaker then continues at a reduced rate through ports 1I, and the air pressure within outlet chamber 66 rises to a value intermediate atmospheric pressure and the pressure within the chamber 65. The elements of the circuit breaker, including ports 1I, must be so dimensioned that the pressure of the lower face of piston 45 and the differential pressure on the two faces of contact 34 remains sufficient to maintain the contacts open.

To prevent reignition of the arc, the blast must insure sufficiently rapid removal of the metallic vapors from the arcing chamber, sufficient cooling of the arcing surfaces of contacts 33, 34 and sufficiently rapid, removal from the air gap defined by the contacts of the air stressed by the dielectric field of the gap. The flow of air takes place at substantially 90 degrees to the dielectric field to hinder the formation of an ionized path in the direction of the field. Subject to the above limitations, the blast is reduced by ports 'll to the lowest possible value so as to extend the duration of the blast possible within the capacity of reservoir 6. Reducing the blast intensity causes the air pressure in the gap between the arcing contacts to increase, thereby causing the dielectric strength of the gap to increase also.

During the above described current interrupting operation, air under pressure is admitted from reservoir 6 through valve 29, conduit 30 and conduit 35 to motor i6, and the motor opens contact I4. The operation of motor i6 is so adjusted that contact I4 begins to open immediately after reduction of the air blast by closure of valve 69, and reaches full open position while the air blast is still of such intensity as to prevent reignition Valve 29 may then be reclosed either manually or automatically as is well known.

Upon reclosure of valve 29 the arcing chamber returns to` atmospheric pressure by discharge of the air through port 1I, and contacts 3l, 32, 33, 34 return to the position shown in Fig. 2 under the action of spring 43. During this reclosing operation, contact 34 first engages contact 33, and further movement of the contacts results in sequential sliding engagement of contact 3| with the concave surface of segments 32 and abutting engagement of surfaces 34 and 36 to stop the contacts. Spring 68 returns valve 61 to the position shown.

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 changes and modifications 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:

l. An electric circuit breaker comprising an arcing chamber having an outlet, a pair of cooperating arcing contacts arranged to divide said chamberv into an inlet portion and an outlet portion, means for opening said contacts, means for introducing arc extinguishng'fluid under pressure into said inlet portion to produce a blast of fluid between said contacts and through said chamber, valve means for controlling said outlet,

"and pressurel responsive means distinct from said contact opening means and so arranged as to be subjected to the pressure within said inlet portion simultaneously with said contact: opening means for causing operation of said valve means.

2. An electric circuit breaker comprising an arcing chamber having an outlet, a pair of cooperating arcing contacts arranged to divide said chamber into an inlet portion and an outlet portion, means for introducing arc extinguishing fluid under pressure into said inlet portion, means responsive to the pressure within said inlet portion for opening said contacts to draw an arc therebetween toI be extinguished by a blast of said fluid, valve means for controlling said outlet, and pressure responsive time delay means distinct vfrom said contact opening means and so arranged as to be subjected to the pressure 'within said inlet portion simultaneously with said contact opening means for causing operation of said valve means.

3. An electric circuit breaker comprising an arcing chamber having an outlet, a pair of cooperating contacts arranged in said chamber, means for opening said contacts, valve means for controlling said outlet, means for producing a blast of arc extinguishing fluid directed between said contacts and through said chamber, pressure responsive means distinct from said contact opening means and so arranged as to be subjected to the pressure within said arcing chamber immediately upon production of said blast for causing slow operation of said valve means, and means responsive to operation of said valve means a predetermined extent for causing rapid operation of said valve means.

4. An electric circuit breaker comprising an arcing chamber having an outlet, a pair of cooperating contacts arranged in said chamber, means for opening said contacts, means for producing a blast of arc extinguishing fluid directed between said contacts and through said chamber, valve means for controlling said outlet, actuating means for said valve means, pressure responsive time delay means distinct from said contact opening means and so arranged as to be subjected to the pressure Within said arcing chamber immediately upon production of said blast for controlling the operation of said valve actuating means, and means for varying the time of operation of said time delay means.

5. An electric circuit breaker comprising an arcing chamber having an inlet and an outlet, a pair of cooperating arcing contacts arranged to divide said chamber into an inlet portion and an outlet portion, valve means for controlling said outlet, means for introducing arc extinguishing fluid under pressure into said inlet portion, means forming a path for the flow of said fluid from said inlet portion into said outlet portion prior to opening of said contacts, means for opening said contacts to draw an arc therebetween and to cause a blast of said fluid between said contacts to extinguish the arc, and means for causing operation of said valve means while said contacts are open.

6. An electric circuit breaker comprising an annular conductive member bounded by a plane surface intersecting a convex surface of revolution. a plurality of contact segments arranged about said surface of revolution to define substantially a concave surface of revolution, means for resiliently mounting said segments on said member and for urging said segments against said convex surface of revolution, a fixed contact coaxial with said member'bounded by a second plane surface intersecting asec'ond convex surface of revolution, and meansl for. moving said member toward said fixed contact to cause sef quential sliding engagement of said fixed contact 7. An electric circuit 'breaker comprising an annular arcing contact deilnlng an oriice, a second arcing contact arranged to substantially close said oriiice when engaging said annular contact, means for opening said contacts to establish a gap therebetween, means for directing a blast of fluid through said gap and through said orice to extinguish an arc drawn between said contacts upon opening thereof, said contacts forming a sinuous path comprising substantially parallel portions for the flow of current therethrough to urge the arc toward said orifice by electromagnetic action of the current and one of said contacts having a subdivided arcing surface to limit the circumferential spread of the arc.

8. An electric circuit breaker comprising an annular contact having aA peripheral current leading portion and a central engaging portion defining an once, a plug contact having an engaging portion for engaging said annular contact and for substantially closing said orifice, a reciprocable contact stem of smaller diameter than said plug contact for supporting said plug contact and for conducting current thereto, means for separating said contacts to establish a gap therebetween, and means for directing a blast of iuid from the periphery of said contacts through said gap and through said orifice to urge an arc drawn between said contacts upon opening thereof through said orifice to cause extinguishing of the arc, said plug contact being provided with a cavity separating said engaging portion thereof from said stem to cause the current to ow through said engaging portions ilrst inward and thereafter outward through substantially parallel paths to urge the arc inward toward said oriiice by electromagnetic action and thereby assist the 5 extinguishing action of said blast.

9. An electric circuit breaker comprising an annular contact having a peripheral current leading portion and a central engaging portion dening an orifice, a plug contact having an engaging 10 portion for engaging said annular contact and for substantially closing said orifice, a reciprocable contact stem of smaller diameter than said plug contact for supporting said plug contact and for conducting current thereto, resilient 15 means acting on said plug contact to maintain said contacts in engagement, means comprising said resilient means for imparting to said con.. tacts dierent displacements to cause opening of said contacts to establish a gap therebetween, and

zo means for directing a blast of fluid from the periphery of said contacts through said gap and through said oriiice to urge an arc drawn between said contacts upon opening thereof through said orice to cause extinguishing of the arc, said plug 25 contact being provided with a cavity separating said engaging portion thereof from said stem to cause the current to ilow through said engaging portions first inward and thereafter outward through substantially parallel paths to urge the l0 arc inward toward said orifice by electromagnetic action and thereby assist the extinguishing action of said blast.l Y

GUSTAV E. JANSSON.

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