US2546007A - Circuit interrupter - Google Patents

Description

March 20, 1951 H. J. LINGAL ET AL CIRCUIT INTERRUPTER Filed Feb. 1, 1945 6 4 c w fam my i HI/ Open Solenoid Core Tra VeZ fiflj Closed INVENTORS mm a z. N Mm m Wu H 6 A .L J m 1 Patented Mar. 2Q, 1951 UNITED :STATES .iPATENT OFFICE 5 CIRCUIT INTERRUPTER ;-Harry J. Lingal, Forest Hills, and James -M. Cumming, Turtle. .Creek, Pa., assignorsto'Westinghouse Elcctric"Corporation, East Pittsburgh, 1 Pa.', a corporation of Pennsylvania Application February 1, .1945, Serial No. 575,714

V 2 Claims.

-1 This invention relates in general to electric circuit interrupters, and more especially to such interrupters which are designed for automatic high-speed reclosing.

In order to meet modern requirements for highspeed re'closing of..an automaticreclosing circuit breaker, it has. been proposed that the breaker .be closed before .it reaches its .full open position upon a circuit interrupting operation, preferably,

verse movement .of themovable contact ofv the breaker, and todo this .the kinetic energy of all the moving parts .of. the breaker must be absorbed,

.andthereafterthese parts must be .movedand .accelerated ..in.the .opposite direction. ..usual breaker, therefore, muchtime is lost after ..the.bre'aker. contacts are'stopped .in-. a mid-open .position,. before theactuating mechanism can In. the

accelerate theparts. toclosethe breaker contacts. Accordingly, .one object .of this invention-is to reduce the duty. on reclosing means for an auto- .matic .reclosingncircuit-breaker when such. reclosing meansis .ener'gized at. an intermediate .poi'nt inv the. opening movement .of. the breaker contacts.

Another object of-this invention .-is to provide a relatively high mechanicaladvantage for .cir-

-cuit. breaker actuatingmechanism at a midstroke position-to decrease the timerequired to .close .the' breaker contacts from this position.

Another object .oithis invention is toprovide in high-.speadautomatic partial-stroke reclosing .circuit breakers, novel actuating mechanism. hav

ingits greatest mechanical. advantage substantially atv a. point midway ofthetnormal operating .stroke of. the..mov'able breaker contact. between closed and full open positions.

.A morespecific object of .this invention is. .to

, provide novel, but simple,.actuatinglinkage' for a circuit breaker-which isv capable "of automatically reclosing the breaker contacts at a, point intermediate the ends'of movement thereof in a normal circuit interruptingoperation, which linkage provides 'themost'iavorable' arrangement to produce high-speed -movementsubstantially at said'intermediate point.

These and other objects of this invention'will i become more apparent upon consideration of the iollowing-detailed description of a preferredem- -bodimentthereof, when taken in connection with the attached drawing, in which:

'Figure 1 is a longitudinal sectional view of a circuit breaker tank, with the breaker" mechanism comprising this invention'i-l-lustrated in elevation;

Fig. 2 is aschematicdiagram of an automatic reclosing-;circuit breaker system 'for controlling operation of thew-breaker shown inv Fig. 1; and

Fig. 3 illustrates characteristic power curvesof a breakerconstructed in accordance"withi'thisainvention and prior art. constructions.

. The'circuit breaker lsshownzon theidrawinga' is illustrated as having the contacts:andecertainfof the operating imechanismi thereof. mounted Within. airnetal tank 2. which is adapted to be iilled with. an arc extinguishing liquid substantiallyup V to the level L. Tank' 2 is providedwitha cover dadapted to be releasably secured in .position, for

example by boltsE, and the coveris adapted 'to support thebreaker contacts andthat; part 0f the operating mechanism located within-tank 2.

' 'Tank cover lisprovided with 'apertures 'for*the reception .of bushings 6 of insulating material, such for example as porcelain-or the' like,= and the bushings are constructed-in a well known manstructures 8, in spaced relation. Contact- 'structures 8 are adapted to be bridged-by a movable bridging contact bar Ill mounted-onthe lowerend tact structures 8.

of a lift rod 2, for movementwiththerod into and out of bridging relation with respect to con- Lift rod l2 isof aninsulating material, such as a moldedinsulated material, and is adapted to move bridging contact bar -10 from the closed circuit-position shown in full lines to the full open circuit position 'showrr by dot and dash lines in Fig. l, or from the openposition shown by the dot and dash lines in Fig. 1-'to the closed position shown-by the full lines in Fig. 1.

In order to guide Iift'rod l2 for substantially rectilinear reciprocating movementtank cover 4 has secured Within a hollow'portion i8 thereof a pair of spaced guide' members l4,-which"are "adapted to guide the upper "end of lift rod I2 portion of lift rod [2, and have their'lower'ends joined by a connecting bar 5. A floating actuating lever Zilis adapted to be connectedtothe upper end of lift rod 2, for example as b pivot pin 22, and the other end of the actuating lever is pivotally supported as at 2G- by a supporting lever 26, with the supporting lever 26 being pivotally mounted on an actuating shaft 28 for movement relative to the shaft. Actuating shaft 28 extends transversely of the hollow portion I8 of cover 4 and has one end extended outside of the cover to be connected with an actuating lever 36, which may be motivated by a connecting link 38 adapted to be connected to a closing solenoid or the like. Floating actuating lever is adapted to be actuated by toggle lever 38 and link 32 pivotally connected together by a knee pivot pin 34, with link 32 pivoted to an intermediate point on floating actuating lever 20, and with toggle lever rigid with actuating shaft 28. Preferably, a coil spring 43 is provided, reacting between the upper end of lift rod l2 and cover l, to bias contact bridging bar It] to the full open circuit position shown in the dot and dash lines in Fig. 1.

In the operation of the structure shown in Fig. 1 of the drawing, the breaker mechanism is normally latched in the closed circuit position shown in full lines in Fig. 1., by means to be hereinafter described. It will be apparent that when such latching means is released, spring 43 will be free to move lift rod i2 downwardly and thus actuate contact bridging bar It to the full open circuit position shown in dot and dash lines. In order to close the breaker contacts, it will be necessary to exert a force on connecting link 38 in a direction downwardly as viewed in Fig. 1, to rotate actuating shaft 28 in a counterclockwise direction. Such rotation of actuating shaft 28 will cause toggle lever to lift floating lever 20 through toggle link 32, and since the outer end of floating lever 20 is constrained for rectilinear movement by guides Hi, lifting of this lever by the toggle links causes it to assume various angular positions during its movement corresponding to movement of contact bridging bar II) from the full open to the closed circuit position. It will be noted that as the breaker contact bridging bar iii moves between the full line position and the position shown by dot and dash lines that togglelever 3i! and link 32 will assume a substantially right angle relation when the bridging contact bar It is at a point intermediate its closed circuit position and its full open circuit position. Consequently, at such intermediate position, preferabl at a point substantially midway between the ends of the path of movement of bridging contact bar It, the motive means applying force to connecting link 38 will be most effective to move contact bridging bar Ill, because the ratio of breaker travel to travel of the solenoid or other actuating means is a minimum at such intermediate position as shown by curve 82 in Fig. 3. This means that the actuating means is able to stop circuit opening movement of the breaker parts and accelerate them in a circuit closing direction in less time than conventional mechanisms having a high ratio of breaker travel to solenoid travel, at mid-stroke, such as the mechanism illustrated by curve 80 in Fig. 3.

Conventional mechanisms for obtaining straight line movement of a circuit breaker lift rod generally have a ratio of breaker travel to solenoid travel which varies from about 5:1 at the full open position of the breaker contacts, to 1:1 at the closed position of the breaker, as illustrated by curve 60 in Fig. 3. This means, by

Way of example, that a force of five pounds would have to be exerted on connecting link 38 in order to move the breaker closed, if the breaker had a resistance of one pound at the fully open position, and at the closed circuit position the full five-pound force would be applied to the breaker contacts. However, at mid-stroke, it would be evident that after a breaker travel of about 2 inches, assuming a five-inch stroke, the mechanical disadvantage would be about 3.25:1 as shown by curve 80. The curve for the mechanism illustrated in Fig. 1 is designated 82 in Fig. 3, and obviously has quite a different characteristic than the conventional mechanism typified by curve 80. The curve 82 is notable in that the mechanical disadvantage is substantially decreased at mid-stroke. This means that the power available at mid-stroke is considerably raised, which isof especial importance in connection with a partial stroke automatic reclosing circuit breaker, as will be hereinafter described. Thus, assuming the power available to reclose to be 1000 pounds, then the power obtained at mid-stroke on curve 88 would be only about 307 pounds, whereas that obtained at midstroke on curve 82, with the mechanism illustrated in Fig. 1, would be approximately 690 pounds, or over twice that obtained with conventional mechanisms. 7

In Fig. 2 there is illustrated diagrammatically a suitable reclosing circuit breaker system for controlling the circuit breaker shown in Fig. 1. A trip coil 40 and closing solenoid 42 are indicated schematically with trip coil fill adapted to release a latch 4| which normally maintains the breaker contacts in closed circuit position against the bias of opening spring 53. The reference numeral 46 indicates a supply circuit which is arranged to be connected to a load circuit 48 by the circuit breaker I. A fault responsive relay 50 is connected so as to be energized in accordance with the current flowing through circuit breaker I. When the current supply to load circuit 43 exceeds a predetermined value, overload relay 50 is arranged to effect energization of trip coil 40, provided the circuit breaker is closed. Also, overload relay 50 initiates the closing operation of the circuit breaker before it has completed the opening operation, preferably, as previously described, this closing operation is initiated substantially at a point midway between full open and closed circuit positions of the breaker contacts. This result is obtained by having relay 50 complete an energizing circuit or instantaneous reclosing circuit for a closing control relay 52, which, in turn, completes an energizing circuit for closing coil 42.

As previously pointed out, a reclosing operation of the breaker I, which is caused to take place before the breaker bridging contact has attained its full open position, imposes an extremely heavy duty on the closing solenoid, because the momentum of all of the parts which are moved by opening spring 43 during the circuit opening operation must be absorbed, and the movement of these parts rapidly reversed in order to rapidly reclose the breaker contacts. The reason for the particular mechanism illustrated in Fig. 1, having the characteristic curve 82 shown in Fig. 3, will now be apparent, because this particular mechanism afiords the lowest mechanical disadvantage at mid-stroke which is the point at which closing solenoid 42 is energized for a partial stroke reclosure by the means shown in Fig. 2,

.5 and; thus permits: faster-,:-reclosingof the .'-conacts.

In order to. limit the number of instantaneous partial stroke reclosures .of thebreaker to a predetermined number, which, in the arrangement shown,;is one,,a lockout relay 54 is provided .which, after theinitial reclosuremaintains the instantaneous reclosing circuit described above for relay 52, openfor a. predetermined time interval if the circuit breaker remainsiclosed and maintains the instantaneous reclosing-circuit permanently open if the circuit breaker remains open at theexpiration of the predetermined time interval.

As shown, the operating coil 56 of'lockout relay 541s connected in series with closing coil 42. The operating coil 55 when energized opens the circuitof relay 52 which is completed by overload relay 50, -so that a subsequent operation of relay 50 does not affect immediate energization of closing relay 52. Lockout relay is arranged in any suitable manner so that it is held in its energized position after the operating winding fifiisdeenergized. In the arrangement shown this result is obtained by means of a latch- 58 which holds-the relay in energized position, and which-is arranged to be released by a release coil 50 when energized.

There also is provided additional automatic reclosing-means 150f any suitable type, for effecting reclosing of thecircuit breaker a predetermined number of-times'with relatively long time intervals between successive reclosures, so that the breaker movable bridging contact'moves to full open circuit position each time, in case the breaker does not remain closed after initial reclosure. Reclosing-means 16 also is adapted to effect energization of --release coil' 58 ifjthe breaker remains closed after operation of automatic reclosing means 16 for a predetermined period of time. Such reclosing means 16 may be similar to that disclosed in R. J. Wensley Patent No. 1,786,324, granted December 23, 1930, and assigned to the same assignee of this invention.

The particular reclosing system illustrated in Fig. 2 operates in detail substantially as follows:

Under normal load conditions the breaker remains closed and the control devices are in the positions shown. When an overload occurs overload relay 5B closes its contacts 52 to complete a circuit through the auxiliary contacts 64 on the breaker for energizing trip coil 40 and thus cause release of latch 4i and opening of the breaker by spring 43. At thesame time an energizing circuit is completed for reclosing relay 52 through the contacts 65 of relay 56 and the contacts 68 of lockout relay 54. By closing its contacts 19, relay 52 completes a series energizing circuit for closing coil 42 and the operating winding 56 of lockout relay 54. Energization of closing coil 42 results in reclosing of the breaker contacts in the manner previously described. Energization of lockout relay 54 causes opening of its contacts 68 to prevent a subsequent energization of overload relay 5%] from effecting another instantaneous reclosure of the circuit breaker.

Closing of the auxiliary contacts 12 of the circuit breaker by initial opening thereof completes a starting circuit 14 for automatic reclosing means 76. If the fault persists when the breaker is reclosed, overload relay 50 again causes its contacts 62 to energize trip coil 40 and thus again open the breaker. Closing of contacts 66 does not close the instantaneous reclosing circuit re- After the second ppening of ,thebircuit breaker I a time; interval elapses; before reclosing. means it completes a closing circuit' 18 for ;relay 52.

. When this, closing circuit is -completed,qrelay 52 by closing its contacts completes an energizing circuit for closing coil 42 as previously described to effect another ClOSlIlgfif the breaker.

The automaticreclosing means .16, arranged in a manner welkknovvn inthe-art to eifect aipredetermined number; of energizationsrofi closing r-relay 52-; and if the breaker,failsitoremaingclesed -afterjthis, number of reclosures; automatic: re-

closing means 16 is renderedinoperative to nake nyafur herwreclosure. Iftherrbr ak rs remain closed before the predetermined; number .Of :re-

; closures has occurred, reclosing means 16 .is-pperativeto release latch 58 by energization of circuit 8 to restore; lockout; rel y. 54.1150... its...n0r;m al position.

ltcan thus be seenfromtheioregoingzthat in ,;,an, automatic reclosing circuit brea-kerzwherein a predetermined reclosing operation, intanylse- ,quence of closely;-succ.essive circuit interrupting -operationsris'instantaneous and of;thei.partial stroke variety,ythe;;mechanismdisclosed herein permits the use of relatively ,smalLreclosing motive; means, such 2.51 a reclosingsolenoid .or the like, while, rendering .such ;instantaneous reclosure particularly efficient and; at a. more rapid rate due to the characteristics ofthemechanism which renders the force, delivered 1301 13116 contact fromthe reclosing means to be amaximum. at

the point in the stroke. where .reclosure occurs.

As previously pointed out, such, instantaneous partial stroke reclosing preferably occursiat the mid-point in the. stroke of, the movable. bridging contact bar, of jthe; breaker ,from .ClOSGdxCllCllit position to full'open circuit position. Although the mechanism illustrated has a somewhat higher ratio of breaker to solenoid travel at the closed circuit position than conventional mechanisms, as illustrated in Fig. 3, this is not a disadvantage because it Will be observed that the ratio is not as high as at open position, and although greater resistance is encountered than at the open position, advantage may be taken of the kinetic energy of the moving parts adjacent closed position, so that the higher ratio at this position is not detrimental.

Having described a preferred embodiment of the invention in accordance with the patent statutes, it is desired that the invention be not limited to this particular embodiment, inasmuch as it will be apparent to persons skilled in the art that many modifications and changes may be made therein Without departing from the broad spirit and scope of this invention, as defined in the following claims.

We claim as our invention:

1. In an automatic reclosing circuit breaker, separable contact means at least one of which is movable and is biased to a full open circuit position, means for releasably holding said movable contact means in closed circuit position and being operable in response to predetermined conditions to release said movable contact means, reclosing means comprising a closing lever connected to said movable contact means, an operating lever for applying force through a connecting link to a fixed point on said closing lever in a direction for moving said movable contact means from full open to closed circuit position, means responsive to a predetermined circuit opening operation of 7 said breaker to cause said reclosing means to halt opening movement of said movable contact means at a point before said movable contact means reaches full open circuit position and to immediately return said movable contact means to closed circuit position, the fulcrum of one of said levers being movably mounted relative to the fulcrum of the other lever, and a guide for said one lever to shift said movable fulcrum for varying the effective lever arm from the pivot of said operating lever to the said fixed point where it tion, means for releasably holding said movable contact means in closed circuit position and being operable in response to predetermined conditions to release said movable contact means, reclosing means comprising a closing lever connected to said movable contact means, an operating lever for applying force through a connecting link to a fixed point on said closing lever in a direction for moving said movable contact means from full open to closed circuit position, means responsive to a predetermined circuit opening operation of said breaker to cause said reclosing means to halt opening movement of said movable contact means at a point before said movable contact means reaches full open circuit position and to 8 immediately return said movable contact means to closed circuit position, the fulcrum of one of said levers being movably mounted relative to the fulcrum of the other lever on a pivoted supporting link, and a guide for said one lever to shift said movable fulcrum for varying the effective lever arm from the pivot of said operating lever to said fixed point where it applies force to said closing lever in response to movement of said movable contact means so that this distance is a minimum thereby causing the force delivered to the movable contact means by said reclosing means to be highest substantially at the point in the movement of said movable contact means corresponding to the aforesaid point in the path of movement of said movable contact means where opening movement may be halted HARRY J. LINGAL.

JAMES M. CUMMING.

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

UNITED STATES PATENTS Number Name Date 907,108 Elden Dec. 15, 1908 1,001,716 Wallace Aug. 29, 1911 1,021,746 Badeau Mar. 26, 1912 1,371,536 Aalborg Mar. 15, 1921 2,031,447 Anderson Feb. 18, 1936 2,125,835 MacNeill Aug. 2, 1938 2,282,348 Thumim May 12, 1942 2,295,307 Thumim Sept. 8, 1942 2,319,645 Thumim May 18, 1943 2,326,061 Ow Aug. 3, 1943 2,378,270 Westervelt June 12, 1945 2,385,013 MacNeill et a1 Sept. 18, 1945 2,403,055 Cunningham July 2, 1946

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