US2426250A - Gas blast circuit breaker - Google Patents

Description

Aug. 26, 1947. P. l.. TAYLOR 2,426,250

GAS B LAST CIRCUIT BREAKER Filed May 21, 1943 3 Sheets-Sheet l uwnlmnwr P. L. TAYLOR GAS BLAST CIRCUIT BREAKER Aug. 2s, 1947. 2,426,250

Filed' May 21 1943 5 Sheets-Sheet 2 Aug. 26, 1947. P. L. TAYLOR 2,426,250

GAS4 BLAST CIRCUIT BREAKER Filed May 21, 1943 3 Sheets-Sheet 3 Patented Aug. 26, 1947 UNITED STATES PATENT OFFICE GAS BLAST CIRCUIT BREAKER Application May 21, 1943, Serial No. 487,888

9 Claims. l

This invention relates in general to gas blast circuit breakers and particularly to an improved method of and means for increasing the interrupting capacity and improving the performance of gas blast circuit breakers by the control and limitation of the arc products,

In prior art gas blast circuit breakers of the type provided with a nozzle or orifice type of contact through which the arc is blasted, the interrupting ability of the circuit breaker has been considered to be principally dependent upon the manipulation of (l) air pressure, (2) Dort area, (3) number of breaks and (4) insertion of resistors. Prior art breakers of this type are limited as to interrupting ability, particularly When built within the space and other limitations of modern circuit breaker practice. This limitation has been believed by some to result from the effective plugging of the orifice by an arc core of large diameter.

In a particular case, attempts were made to extend the interrupting range of a prior art gas blast circuit breaker of nozzle contact type to L10,000 amperes at 2300 volts, Within the space and other limitations dictated by modern circuit breaker practice. It was found that at currents of the order of 20,000 amperes and above, the arc was reignited in or transferred to regions in the circuit breaker Where extinction of the arc Was difficult or impossible and the breaker failed. The prior art gas blast circuit breaker of the nozzle contact type was thus found to be inadequate.

The principal difculty encountered was the failure to adequately control and limit the arc and its products, especially at and before the orifice. it was found that the metallic vapor and particles, developed by the extremely rapid vaporization of the contact material at the point of contact and arc inception, were driven back along the stream of gas, in a direction adverse to that necessary for efficient interruption. Pressures Were developed of sufficient magnitude to effectively overcome the pressure of the gas blast in certain sections and to drive the arc products back along the gas stream. This caused arc transfer or restriking of the arc in locations where it Was difficult or impossible to interrupt the arc. Also, these arc products, after having lost the impetus imparted to them by the explosive force, are swept back into the zone of the arcing contacts by the gas blast thus prolonging the arcing in that region.

It was further found that the nozzle type of breaker permitted in some cases excessive development or propagation of the arc inception areas, particularly on the stationary contact, in a direction away from the orifice, thereby delaying the movement of the arc terminal to and through the orifice and -causing the production of excessive conducting vapor on the gas inlet side of the orifice.

It is therefore an object of the present invention to avoid the above disadvantages in a nozzle type gas blast circuit breaker by limiting, controlling and localizing the conductive products of arcing so `as to minimize contamination of the gas blast and to facilitate circuit interruption.

It is a, further object of the present invention to provide a gas blast circuit breaker With an interrupting chamber oi geometrical configuration such that arc products not immediately scavenged will be trapped and prevented from reaching portions of the interrupter in such concentration that their presence is detrimental to the eiicient operation of the circuit breaker.

It is also an object of the present invention to provide in a gas blast circ 't breaker, provided with arcing contacts and main current carrying contacts in circuit therewith, an impediment to the transfer of arc products from the region of the arcing contacts to the region of the main current carrying contacts.

It is also an object of the present invention to limit in a gas blast breaker the development and propagation of the arc inception areas and arc terminals in a direction adverse to that conducive to efficient interruption and to thereby reduce the time required to drive the arc into the interrupting zone.

Objects and advantages other than those above set forth will be apparent from the following description When read in connection With the accompanying drawing, in which:

Fig. 1 is a view partly in elevation and partly in cross-section of a circuit breaker embodying the present invention;

Fig. 2 is an axial cross-section through the contact chamber of the embodiment illustrated in Fig. 1;

Figs. 3, 4 and 5 are axial views partly in crosssection of modified interrupting and contact chambers that may be substituted in the circuit breaker shown in Fig. 1 for the interrupting and contact chambers shown in Fig. 2;

Fig. 6 is a diagrammatic illustration of desirable relative positioning of the main current car- 3 rying contacts and of the arcing contacts shown in Figs. 2, 3, 4 and 5; and

Fig. '.7 illustrates a modified form of the invention as shown in Fig. 4.

Elements performing the same function in these different embodiments are designated therein by the same reference characters although such elements may be of'different configuration in the various embodiments shown.

Referring more particularly to the drawing by characters of reference, reference numeral II designates a reservoir serving both as structuralv element and as source of supply fluid under pressure for the circuit breaker. Theiluid utilized may be any of the insulating extinguishing an arc but will be assumed to be compressed air preferably maintainedatf a pressure of the order of 100 to 225 pounds per square inch. Reservoir I I may be placed in communication with a hollow cylinder I2 dening a contact chamber I3 through a valve I4 and throughl a hollow insulator I5. The ilow` of iluidfrom reservoir II to. atmosphere continues from` contact chamber i3. through an orifice typecOntact I1 and through an arc extinguishing or interrupting chamber I 8. Chamber lis generally defined by an elbow I9 of conductive material havingasubstantially uniform cross-section and by a` cylinder 23. of insulating material,

Valve I4 is preferably operatedi'by means of `a pneumatic motor ZIadapted to be` supplied with air. fromv reservoir II through a valve 22. controlled by a solenoid 23. When-valve I4 is open air is also suppliedltherethrough to a second air motor 24 serving to open amovable disconnecting contact 25 cooperating with a xed disconnecting contact 21.y Contact 26=may` be reclosed by a third pneumatic motor 28 connected with reservoir Il through a valve 2!!` controlled by a solenoid 33. The circuit controlled by the circuit breaker is assumed to be an alternatingcurrent circuit represented by two sectionsofconductors 3| which are joined to disconnecting contacts-26, 21 inserieswith the main andfarcing contactsy of the circuit breaker.

As illustrated in Fig. 2, the contact chamberY I3 provided with a pair of relatively movable arcing contacts 5I and52. Contact 5I is illustrated as being stationary and of the type provided withan orifice or nozzle I1: Relatively movable main contacts 32 and33 .are in parallel with arcing contacts 5I and 52. Contact 32 is preferably made of a` series of segments resiliently mounted, as shown more clearly in Fig. 3, to form an annular stationary contact..

When the main contacts 32, 33 are parted the entire current flows through the arcing contacts 51, 52.- In prior art circuit breakers of 'this type, the cooperatingsurfaces of the arcing contacts were of copperor some similar material. Asthese contacts were heated by the heavy current flowing therethrough upon opening of main contacts, a point often near the edge ofv the stationary contact was heated nally to incandescencel The emanationof ionizedparticlesfrom this incandescent'spot sometimes causedanarc to be struck across the edge of the two arcing contacts, even prior to parting thereof.; This'was conducive to propagation of the arc inception area in a direction adverse to that vnecessaryi'or efficient interruption.

Pressures were` developedin the arc inception region of suhicientv magnitude to effectively overcome the pressure of the air blast and to drive the conductive particles and vapors back along iluids suitableA for the air stream. The metallic particles and vapors not only contaminated the air stream to be utiized for interrupting the arc, but also cause arc transfer to or restriking of the arc at the main contacts or in other regions where interruption was difficult or impossible.

In the present invention the metallic vapors and, particlesare localized andfminimized. As illustrated in Fig.` 2, the contact surfaces 53 and 54 are preferably made of a highly arc resistant material such as a tungsten-silver sintered mixture effective-to reduce metallic emission. Contact face 54 is made slightly larger in diameter than-contact face 53. Insulating material 55, preferably refractory, is provided immediately adjacent the contact face 54 whereby the root of the-arc forming on the material 54 will be prevented from being driven along the contact 5I toward the side walls 51.

The arcing contacts 5I and 52 are so shaped and'arranged-as` to expedite the'propagation of the arc into the orifice I1. The angle at which the contact faces 53and 54meet issodesigned that'any metal particles emanating from `the arc region are trapped by. the sidewalls 51 of the chamber I3 and prevented from reaching the main.contacts or other undesirable'regions. The wall 0r; barrier. member 58 further` isolates the mainl contacts 32, 33; from the arcing region of the circuit breaker.

The operation of the movable' contacts 33 and 'E2-is similar in.a1l the modifications. As illustrated in Fig. 4, the movable main contact 33 is connected by a spider 1| to astud 4I on which a. piston 42 is secured by pin 43soas to be slidablegin a cylinder 12; Main contact 33 is biased togits closed position (shown in Fig. 4) by a spring 44; Arcingcontact 52 is threadedonto a hexagonal stud 13 which is slidably mountedsin the insulating disk 14 and biased to closed position by spring 45; Thestud 4I is conductively connected to the stud 13 by means. of` pietails 15. Current entering from theleft handsconductor 3l through connector 16 flows through the shell 11, throughmainicontacts 32, 33 and arcing contacts5l, r52 in-parallel to4 thel stud 4I, disconnect contactsV 2.1,` 26 to the-right hand' conductor` 3l. Althoughthe arcing contacts-.are'closed imparallel.with the mainv contacts, the ow of current willfgenerally pass almost entirely through the main contacts becausel ofy they relatively small area of, the cooperating surfaces of the arcing contacts and because of the higher resistance thereof.

When the circuitis to be opened, solenoid 23 is energized from asuitable source of, current (not shown) to cause actuation of valve V22. The valve admits compressedair from the reservoir I I to the motor 2l, which opensthe blast valve I4. Air underpressure-is then supplied from .the reservoir I.I.through,valve I4 to lchamber I 3fand tomotor 2,4. When the air pressure within the contact chamber buildsup substantially tothepressure of reservoir I I, such pressure is communicated to cylinderA 12 through the aperture 'mthereby moving piston 42` to the right, as. viewed in Fig. 4. against the action of spring 44. Movement of piston42 first separates main contacts 32y 33Iwhile spring 45 maintains, arcing contacts 5I, 52. closed. Upon separation of the maincontacts .the flow of current is diverted from the main contacts to the arcingcontacts. Volatilization of the arcing contact surfaces and emanation of metallic particles therefrom is minimized by the arc resistantcooperating surfaces 53 and 54.

When piston 42 reaches a predetermined position, the insulating disk 'ld engages a shoulder 1S on the stud 'i3 to move contact 52 jointly with contact 33. Contacts 5l, 5t are thereby separated and an arc is drawn therebetween while a blast of air is projected from the contact chamber i3 into the interrupting chamber lil through orifice The air blast issuing from the contact chamber between contacts 5l and drives the arc toward the interrupting chamber lli. Movement of the root of the arc on contact in a direction up stream of the blast, is prevented by the insulatmaterial @Si immediately adjacent the Contact surface rihis arc root is moved through the orifice l'i to a point on contact 5i near the auzo iiiary contact 8G. The arc is extended and loops into the interrupting chamber i8 where it ccntacts auxiliary electrode thereupon breaking into two portions. A. iirst arc portion extends ben tween electrodes and and a second portion between electrode and contact 5l or elbow lil.

The rrst arc portion is located in a zone where the air blasting from the chamber it at maximum velocity suddenly expands to substantially atmospheric pressure w a corresponding drop in temperature. The incandescent ionized air in the arc path is therefore replaced at a rapid rate by cool non-.ionized air, thereby rendering the continuous ionization or the arc path possible only as the arc current remains of relatively high intensity. rlhis portion of the arc path is shunted by resistor lill, which likewise connects auxiliary electrode with contact 52.

When the flow of current through the circuit breaker decreases toward the end of the first half cycle of arcing, the rate of ionization of the arc path between the electrodes 52 and Sii becomes lower than the rate of deionization of the arc path by the blast. The arc between electrodes 52 and 'therefore extinguished, thereby interrupting the fault current. The remnant current thon hows through the circuit breaker through shell ll, elbow itl, the remaining second. arc portion, electrode resisto-r E conductor 8i to the disconnect contacts El. 'TL s current is limited to a relatively low value by the resistor Et. The resistance of resistor @il is of relatively high Value so that the current is substantially in phase coincidence with the voltage of the circuit. rllhis current dissipates the stored energy in the circuit 3 l.

When the voltage reaches zero value, the re` maining arc is easily extinguished by the air blast, the voltage thereupon reverses and follows its normal wave without presenting the over-voltages that would result from a current interruption omitting the discharge of the sto-red energy of the circuit. The air blast carrying the heat dissipated in the arc is cooled and substantially deionized by means of 'cailles S2,

In the embodiment shown in Fig. 3, the Contact chamber i3 is provided with an insert El@ of insulating material a configuration that will collect and cool the metallic vapor and particles while at the same time shielding and isolating the main contacts The inner surface E2 of the insulating material il@ is arranged to stream line the air flow so as to effect a sweeping of the zone of arc inception by a high velocity uniform flow of air approaching the orifice l1. The surface ll provides a surface on which metallic particles from the arc may be trapped out of the main air stream. The surface 6l may be porous as in the case where insert 6l) is of refractory material, and it may be either smooth or ribbed.

An illustration of a modiiied combination of throat and trap member is shown in Fig. 7 The ribs l are formed on the insulation @il so that the faces thereof may easily trap metallic particles, but at the same time form little impediment to the now of gas. The insulating material lill is preferably refractory although fiber has been found to be satisfactory.

The surface tl is so designed as to form a region of substantially reduced velocity or reduced pressure adjacent thereto. This zone of reduced pressure or reduced velocity is effective in trapping, by eddying or otherwise, metallic vapors emanating from the arc. This metallic va por is thereby localized and prevented from reentering the main stream. of air flow in such concentration that its conducting properties would contaminate the air to utilized for arc extinction.

In the embodiment shown in Fig. Il the insulating material in the arcing chamber i3 is designed to have a greater capacity for trapping and condensing of metallic vapor and particles although at some sacrifice in streamlining the flow of gas tothe orifice il. The zone of reduced pressure or reduced velocity air in the chamber i3 is more pronounced than the interrupting head shown in Fig. 3.

Fig. 5 illustrates another embodiment of the present invention. In this embodiment the trapping surface li of the insulating material @il is more closely adjacent the movable arcing contact 52, and therefore the zone of reduced velocity and pressure adjacent the surface il! is less pronounced.

The markedly improved performance of a circuit lorealier embodyinor the present invention over prior art circuit breakers of this type is evidenced by test results on a circuit breaker such as shown in Figs. 3 and ll. In one test this circuit breaker performed over 913 interruptions on a single set of contacts at currents ranging from 10,060 to 40,090 ampercs at 235i@ volts using air pressure at to 1.5i) pounds. On another series of tests, this circuit breaker performed 32 interruptions on a single set of contacts at 37,5%@ amperes at 2390 Volts using air under pressure of 1GO to ll() pounds. On these series of tests; the visible demonstration was considerably less than in prior art circuit breakers in current ranges where operative. In the above tests the fault current was interrupted within one-half cycle after adequate parting of the arcing contacts.

The above tests are particularly good evidence of the improved operation of a circuit breaker embodying the present invention, inasmuch as except for the above disclosed changes in the arcing contacts and contact chamber structure. the circuit breaker tested was the same as the prior art breaker referred to in column l, that failed to interrupt currents of the order of 20,000 amper-es. The high number of circuit interruptions possible on a single of contacts is a further measure of the improved performance of a circuit breaker embodying the present invention.

Fig. 6 illustrates a desirable dimensional arrangement of main and arcing contacts in a circuit breaker of the nozzle contact type. The distance a between the liXed main contacts 32 and the fixed arcing contact lll should be equal i to or greater than twice the distance d, the dis'- tance between they lined arcing contact di and the movable arcing contact when the latter is in the circuit interrupting position shown in dotted lines.

In the embodiments illustrated in Figs. 2, 3, 4 and 7, the surface is for at an angle thejet of metallic particles or vapor ejected the aroing contacts. In 3 4 d 7 angle is substantially a righ-t a -Y near the arcing contacts. ping of the particles and vapor that im such surface. By connecting portion of insulation [lil that is adjacent materi l (and is parallel to the jet of vapor or particles) with the trapping surface fi! that is substantially at right angles to the jet by a curved intermediate portion tangential to both, a structure similar to the bucket of a Pelton wheel provided. Any jet of vapor ejected with a high initial velocity has its velocity reduced by friction and is de` ionized by the insulating material With the structure shown this trapping is accomplished with a minimum of cruitamination` of the gas blast. In 7, the surface available for trape ping has been increased by the ribs (l.

Although but several embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various changes and modications be made therein without departing from te spirit of the invention or from the scope of une appended claims.

It is claimed and desired to secure b; Letters Patent:

1. In a gas blast circuit brealer, a Contact chamber, a pair of relatively movable arcing con tacts adapted to draw an in said chamber, one of which contacts for?. s orifice providing a gas outlet for said chamber, a pair of relatively movable main contacts connected in rillcl with saidarcing contacts and arranged so that the distance between the main Contact and the fixed arcing contact is edual to or greater' than twice the distance between said arcing contacts when in circuit interrupting position, a gas pas'- sage between said main and arcing contacts, insulating material lining said and extending from said outlet substantially to said main contacts, and means for estalilishiiiig a flow ci gas sequentially through and said outlet.

2. In` a gas blast circuit breaker, a contact chamber, a pair of relatively movable contacts adapted to draw arc in said chamber, one of which contacts forms an orifice providing a gas outlet for said chamber, means for establishing a flow of gas through said chamber and said outlet, and means for trappii f roducts of said arc and providing minimum resistance to said iiow of gas, said means comprising insulating material surrounding said orifice and provided with ribs formed at an angle to said flow of gas.

3. In a gas blast circuit breaker, a contact chamber, a pair of relatively movable arcing contactsthe cooperating faces of which meet in a predetermined surface and are adapted to draw an arc in said chamber, one oi which contacts forms an orifice providing a outlet for said chamber, means for establishing a flow of gas through said chamber and said outlet, and a member of insulating material in said chamber immediately adjacent orifice and provided with a rst surface portion forming a continuation of said predetermined surface substantially in alignment therewith and provided with a second surface portion forming a continuation of said first surface portion and extending at a substantially wide angle therefrom toward one of said contacts.

4. In a gas blast circuit breaker, a contact chamber, a pair oi relatively movable contacts adapted to draw an arc in said chamber, one of which contacts forms an oriice providing a gas outlet for said chamber, means for establishing a flow of gas through said cham er and said outlet, and means for minimizing mixture of products of arcing with said ilow of gas, said minimizing means comprising a, portion of said chamber providing a region of reduced gas flow adjacent said orifice contact, said minimizing means further comprising a wall of insulating material in said chamber forming a continuation of the arcing surface of said orice contact.

5. In a gas blast circuit breaker, a contact chamber, a pair of relatively movable contacts adapted to draw an arc in said chamber, one of which contacts forms an orifice providing a gas outlet for said chamber, means for establishing a flow of gas through said chamber and said outlet, and means for minimizing mixture of products of arcing with said .flow of gas, said minimizing means comprising a portion of said chamber providing,r a region of reduced pressure adjacent said orifice contact, said minimizing means further comprising a wall of insulating material in said chamber forming a continuation of the arcing surface of said orifice contact.

6. In a gas blast circuit breaker. a contact chamber, a pair of relatively movable arcing contacts provided with coacting surfaces adapted to draw an arc therebetween in said chamber, one of which arcing contacts iorms an orice providing a gas outlet for said chamber, a pair of main current carrying contacts connected in parallel with said pair of arcing contacts, means for establishing a flow or gas through said chamber and said outlet sequentially across said main contacts and said arcing contacts, means i comprising a surface of insulating material forming a continuation of said coacting surfaces and extending in said contact chamber at a substantial angle to a plane through said coacting surfaces to a position substantially between said pair of main contacts and said pair of arcing contacts for trapping products of arcing at said arcing contacts and minimizing mixture of said products with said gas flow.

7. A gas blast circuit breaker comprising a contact chamber' forming a portion of a passageway for gas flow, an interrupting chamber forming another portion of said passageway, said another passageway portion having a cross-sectional area greater than the cross-sectional area oi said pas-- sageway portion in said contact chamber whereby said gas may expand upon entering said interrupting chamber from said contact chamber, a pair of relatively movable contacts, one of said contacts being an orifice type contact constitu*- ing a third portion of said passageway and connecting said chambers, the other of said contacts being adapted to draw an arc substantially at the Contact chamber end of said orifice contact, means for establishing a flow of gas through said passageway for moving a portion of arc into said interrupting chamber, means preventing movement of the root of said arc on said orifice type Contact in adirection away from said interrupting chamber, said movement preventing means comprising an insulating surface in said contact chamber forming a continuatio-n of the arc drawing surface ci said orifice contact, and said movement preventing means further comprising diiicultly vaporizable material on the arcing surface of said orifice Contact immediately adjacent said insulating material and on the cooperating contact surface of said other arcing contact.

8. In a gas blast circuit breaker, a first charnber provided with a pair of main contacts therein, a second chamber provided with a pair of arcing contacts therein connected electrically in parallel with said main contacts, an interrupting chamber adjacent said second chamber, means for establishing a flow of gas sequentialy through said first, second and interrupting chambers, and means comprising a barrier member positioned between said pair of arcing contacts and said pair of main contacts for impeding movement to said pair of main contacts of products of arcing emanating from an arc at said pair of arcing contacts.

9. In a gas blast circuit breaker, a rst chamber provided with a pair of main contacts therein, a second chamber provided with a pair of arcing contacts therein connected electrically in parallel with said main contacts, an interrupting chamber adjacent said second chamber, means for establishing a flow of gas sequentially through 10 said first, Second and interrupting chambers, and means comprising a barrier member of insulating material positioned between said pair of arcing contacts and said pair of main contacts for impeding movement to said pair of main contacts of products of arcing emanating from an arc at said pair of arcing contacts.

PHILIP L. TAYLOR.

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

UNITED STATES PATENTS Number Name Date 2,287,039 Jansson June 23, 1942 2,125,525 Thommen Aug. 2, 1938 1,928,470 Whitney et al Sept. 26, 1933 2,282,268 Thommen May 5, 1942 1,955,213 Whitney et al. Apr. 1'1, 1934 2,106,032 Lange Jan. 18, 1938 2,063,173 Lange Dec. 8, 1936 1,532,081 Rankin Mar. 31, 1925 FOREIGN PATENTS Number Country Date 352,826 Great Britain July 16, 1931

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