US2944129A - Circuit breakers - Google Patents

Description

:s sheets-sheet 1 CIRCUIT-BREAKERS -T'l a.. 1 /O/ v T. M.` COLE ETAI- -Fl L- July 5, 1960 Filed Nov. l2, 1957 g Il' IH INVENTORS THOMAS/M0046 veA/RVS. W/NGw/w ATTORNEY July 5, 1960 T. M. COLE ET Al. 2,944,129

CIRCUIT BREAKERS Filed Nov. 12, 1957 3 Sheets-Sheet 2 Tali-M555 2% INVENTORS 72104405' A4. COLE E/vm/ S. LVM/GARD ATTORNEY July 5, 1,960 T. M. COLE ET AL 2,944,129

CIRCUIT BREAKERS Filed Nov. 12, 1957 :s sheets-sheet s XR Tn" mgm #my ESS T .0 A. wm n# f v. ,Hh NR B Nw 1 r l.. um. Q

United States CIRCUIT BREAKERS Thorn'as VMQ Cole, Harrison, N.Y., and'rHenry S. Wingard, Cranford; N .'J., assignors to Federal4 Pacific Electric Y Gompany, a corporation of Delaware FiledNov. V1z'19sl1,se1r. No. 695mm '27 claims. (cr. Yzoo-1116) It has been customary to opentlie contactsof a circuit breaker by 4fast-acting mechanismsrv 21nd,. in 4the case of rriulti-pole`ci1cuit` breakers, a common mechanism has been arranged to part all of thecontacts. simultaneously in response to an overload of'either short andseverefior long' andmoderate, character. The present invention is not directly concerned l'with the latter type of fault, although devices constructed.. to handle severe overloads in accordance with the present invention may' also be arranged to respond to such moderate overloads.

To meet thertest of severe current excesses' resulting from' short circuits, the almost universal Aapproach has been* to speed the interruption of the arcs between the contacts as they part, through the use of fast contactoperating mechanisms and quick-acting,v current-responsive `tripping'mechanism; and tol design arc interrupters capable of quenching arcs developed even at'the most unfavorable portion of the alternating `current cycle.

If it should happen that the current owing' in a cir# cuit `breaker is at or rising toward Vits''pealrshort-circuit value' at the instant that the contacts start torseparate', then the ionizing energy to which the contacts of that'pole are Asubjected is most: severe, and the ioniz'ed'gas that is produced may carry the current continuously evenwith the contacts widely separated and even with carefully designed arc chutes.Y The final extinction of the arc generally occurs (if at all) during thaty portion :of the-al'- ternating current cycle when the current is passing; through itsV zero'value irrespective of the time in the-current wave when the contacts start to-separate. Asv a result, particularly -in Ya three-phase circuit breaker subjectedtof a severe' three-phase short-circuit; thel arc' in `one lofthe poles inevitably develops damaging energy during nearly.y halfa-cycle';l and the ionization due' to arcingmay besuch-astoV cause restrikingiof the arc during the suc- `ceedinghalf cycle', and repeatedly thereafter.

Therefore, considering circuit breakers and the likebf predetermined arc interrupting capacity, an object ofthe presentinvention is to increase Athe circuit breaker rating Asonas to operateeffectively to interruptl muchy heavier levels of -peak'currents developed during.' short-circuits. 1 v'In wthe detailed. description of :1n/illustrativeV1 embodimentfofthe inventionappearing below and shown-inY the accompanying drawings, a"multi-pole"circuitgbreaker is provided -in which each pole includes -an individual electent trodynamically actuated contact controllingr and operating? mechanism effective for maintaining the contacts of thatpole closed while the contacts carrypotentially damaging instantaneous values of current, and for opening the contactsv of" that individual pole when the alternating current wave is decaying toward zero and has reached a safe reduced and decliningivalue. Even thougha short circuit` may occur,.theA instantaneous valueof current at thatinstantmay be low due to the portion of thev alternating current wave. at ,the instanttthat the short circuitoccurs; and in that event, nothinghappensuntil thecurrent rises to a level suiiicient to causezthe electrodynamic actionto takeplace.r It is therefore highlyV signicant that opening of thecontacts dependsfxon there vbeing an instantaneous severe current' level duringan alternating current wave, and thatthe opening ofi the contacts of that polezor phase takes place before that current wave crosses the zero level. It' is also signiiicant that each pole vin a'multji-pole circuit breaker operates independently, in accordance with its own instantaneous;currenty conditions.

lnthe aforementioned,preferred embodiment of the invention,.the samefelectrodynamic structure-vis used for accomplishing two functions, namely, for holding the contactsv of-.each` individual pole together duringcurrent excesses and ton conditioning the contact-carrying mechanismv to partv the contacts whenthe current declines to asafevalue. for interruption. It will naturally be 4understood thatseparate electrodynamic arrangements can be provided for these two functions.

'Tlieillustrative multi-pole circuit breaker having the foregoing provisions ineach `of its poles to hold the individual contact. pairs closedduring severe current excessesand` to condition the-individual contact pairs for safe parting is also equipped with a common contact closing and opening` mechanism having a current-controlled latched-spring yarrangement' for openingall of the poles when a severe overloadv occurs in any of them. TheV operation of the-mechanism to open allY of the poles is delayed until after the individual mechanisms of the several poles lhave had time to interrupttheir several currents. vIn Vtnis vway,'the main operating mechanism does not force open a pair of contacts that,.at a particu# lar instant, maybe carrying a heavierlinstantaneous value of currentthan the circuit breaker can interrupt nor is any circuit' interruptedl where the currentV is low but is inereasingt'oward a destructive level.

The 'nature of the invention together with 'additional features and objects will be better appreciated and understood from the following detailed disclosure'of the illustrative embodiment which isV shown in ther accompanying drawings forming part of thisdisclosure. In'the accompanying drawings:

' Fig. 1- is a side elevation, largely in cross-section of one pole of a multi-pole circuit breaker embodyingcertain aspects of thepresent invention; Y

' Fig.' 2f is' the plan view of a multi-pole circuit breaker eachpole of which is constructed according to Fig. 1;

Fig. 3 is the perspective view, with a portion broken away,of a current-carrying element in Figi' 1;

Fig; 4 is'the'plan'view of the element shown in Fig. 3;

Figs 5, 6, 7 and 8 are somewhat enlarged views of the mechanism =in Fig. l in various operative configurations thereof;

Fig. 9 is a'fragrnentary elevation 'of the commonoperating mechanism ofv the multi-pole'circuit breaker of Fig. 2;

Fig.l l0 is a fragmentary cross-'sectional view along the Vline 10-10 iny Fig.' 9.

Fig. 11 is agraphic repres'entation'ofv the three-phase operationtof the1three pole circuit 4break'erfiny Figs'. 1-10'.

The illustrative circuit breaker here shown employs issued March 23, 1954, to T. M. Cole (one of the pres-v ent applicants) that patent being assigned to the assignee of this application.

The multi-pole circuit breaker shown in the accompanying drawings includes in each pole a pair of terminals and 12, an arc chute 14, a pair of contacts including a movable contact 16, a stationary contact 18, and novel means for supporting and individually operating each movable contact 16. A common operating mechanism as shown in Fig. 9 is provided for all of the poles, controlled for automatic release by a common trip bar 20. Individual current-responsive bimetals 22 for each of the poles are arranged to operate the trip bar. The bimetals act in the usual fashion to trip the circuit breaker after a relatively long interval of sustained moderate overload.

Referring particularly to Fig. 1, each movable contact 16 is carried by a conductive contact-carrying arm 24 as of copper which has a pivot 26 that operates in a slot 28 formed in contact arm 24. Pivot 26 is xed to a pair of arms 30 forming a contact-arm carrier that is in turn fixed to a square shaft 32 formed of insulation or of metal sheathed in insulation. The portion of arms 30 which flank contact arm 24 adjacent pivot 26 are quite close to each other so as to provide side guides for the movable contact arm 24. Those close-spaced guiding portions of arms 30 are connected by bends (Fig. l) to the remainder of the arms which are widely spaced to accommodate four over-centering springs 34 and 36 asv shownalso in Figs.y 9 and 10. These springs operate as a form of toggle between respective end pivots 35 of the toggle in arms 30 and pivots 37 in an upstanding ear 38 on a rearward extension of movable contact arm 2'4 to the left of pivot 26 in Fig. 1, forming the knee of the toggle. YClose nearby, movable contact arm 24 has another extension 40 which bears against a stop 42 when the contacts are open in the configuration of Figs. 8. Elements 26, 32 and 42 unite arms 30 into a sturdy supporting and guiding carrier that pivotally supports and bodily moves contact arm 24.

The configuration of the mechanism shown in Figs. 1 Y

and 9 is that corresponding to the normal operating condition with contacts 16 and 18 closed. In that conguration, extension 40 of the movable contact arm 24 is spaced away from the stop 42. The opposite ends of each spring 34 and 36 are compressed toward each other, with the result that portion 38 of movable contact arm 24 is spring-biased upward and counter-clockwise about pivot 26. This firmly but resiliently biases movable contact 16 against xed contact 18 to provide the usual contact pressure for normal operation.

The corresponding contact-carriers 30 of all of the poles are united by square shaft 32 for operation in unison, as a relatively rigid unitary element. This square shaft is operated by mechanism appearing in Figs. 9 and l0, now to be described. This common operating mechanism is provided for all the poles in the illustrative multi-pole circuit breaker. Alternatively any suitable individual operating mechanisms may be used for each pole with a trip-one-trip-all arrangement and with a common operating handle.

The common operating mechanism is aligned with the center of the three poles and operates contact-arm carrier 30 of that pole directly. This contact-arm carrier operates square shaft 32 which actuates the other contactarm carriers 30. The center-pole operating mechanism is largely carried lby a pair of plates 44 which are anchored to the bottom of the molded insulating enclosure 46. A manual operating lever 48 has a pivotal seat 5i) in each of these frame plates 44, so as to swing between the closed-contacts position in Fig. 9 and another position, to the left of that illustrated in Fig. 9, when the contacts are open. A pair of tension springs 52 'act between handle 48 and the pivot or knee 54 of a toggle including a lower toggle links S6 (Fig. 10) and upper toggle links 58. The two lower toggle links 56 have separate pivots 60 to the respective arms 30. Upper toggle links 58 are biased upward against a pivot 62 carried by a cradle or releasable member 64 that is pivoted at 66 in frame plates 44.

A secondary latch 68 having a pivot 68C in plates 44 has a right-hand end l68a which arrests cradle `64 and a left-hand end 68h that rests on a latch 70 carried by the common trip bar 20. Compression springs 72 at the ends of bar 20 bias latch 70 toward the right as seen in Fig. 9. 'This latch is shifted toward the left by one or all of the bimetals 22 in the respective poles, acting through an adjusting screw 74 in each of the poles carried by a respective bracket 76, joined to common trip bar 20. It is evident that, if any or all of the bimetals 22 should deflect toward the left, trip bar 20 will rock counterclockwise so as to release latch 70, secondary latch -68 and cradle or releasable member 64. When this occurs, as is conventional, springs 52 swing member 64 counterclockwise. At the same time, springs 52 buckle `the toggle by pulling its knee 54 past center, and springs 52 then are effective to swing moving contact-arm carriers 30 counterclockwise for swinging the contact arms 24 of all of the poles in the contact-opening direction. Manual lever 48 is also moved by springs 52' a short distance to the left of the position in Fig. 9 to provide the usual trip indication.

When secondary latch 68 is released by its latch 60,

and it attempts to rotate about its pivot 68e, it must also rotate a pendulous-mass delay element 78 pivoted at`80V by virtue of gear teeth interconnecting members 68 and 78. This delay element augments the inherent ldelay involved in the operation of a bimetal 22 (which takes time before it heats up and deflects) and the natural delay in the mechanical operation of the secondary latch and the' rest of the automatic contact-opening mechanism. As will be seen, it is desirable for a certain minimum time delay to be provided for inhibiting the opening of the contacts during severe over-load conditions. With some mechanisms there may be enough natural delay, and the delay element 78 may be unnecessary and may be omitted.

After the circuit breaker has been released by an overload, resetting is necessary. This takes place whenV manual lever 48 is swung to the extreme leEt-hand'posi-f tion so that lever portion 48a swings cradle 64 for relatching, and the knee of the toggle 54- is urged to the left. Subsequent operation of lever 48 to the right for closing the contacts acts to straighten and overset the toggle 56-58.

A link 82 is pivoted to operating lever 48 and to a twoarmed lever 84 that is carried by a pivoted square shaft 86 of insulation or insulation-sheathed steel. Shaft 86 extends across all the poles and is carried by suitable end and intermediate `bearings in molded base 46. A roller 88 coacts with the rearward projection 40 of the movable contact arm 24 during the re-setting operation, for restoring the movable contact arm 24 to its normal condition in relation to its contact-arm carriers 30, following a peakcurrent contact-opening operation. The purpose of this reset linkage is to operate arms 24 from the configuration in Fig. 7 to that-in Fig. 8, as will appear later. The'adjoining poles are similarly equipped with rollers 88 carried insulated parallel -vertical conductors 94, :extendedivia horizontal' insulated Iconductors 96 and -via vertical insulated conductors 98, to be rejoined at a pedestal 100. Them fixed contact 18 is mounted on 4pedestal 100. h i l A circuit may be traced through thel circuit breaker as follows:v Starting at terminal 10, the current follows a path-through bimetal-22` ofeachpole, and then along the f l flexible braid 101 tothe moving contact arm 24, through contacts 16 and 18, along'conductors 98, I96,,94 and'90,m

ultimately to terminal '12. In a reversal `ofvparts, the coil represented by conductors 90, 94,5916 and `98 couldjbe i interposed `in series with-the iiexible braid so that the current would theny passfrom the bimetal th'rough-suit-V` i able braid to the coil, then by braid to m'oving contactV arm'24 and ultimately' to iixed contact 1'8 connected directlyto terminal 12. In the arrangement shown, the

coil'is electrically at the potential of the terminal 12` dur-l ing end after are interruption, whereas inthe other-ar 'A rangementde'scribed, the coil -is electricallyatthe potentialI -v v andthe contact arm 24. However,`for extreme overloads,-

severe instantaneous levels of current will produce elec-jf trodynarnic'action'of considerable forge. Atorceoffatf tractionf will existfbetween arm 24 and conductor 90 whereas afforc'e of repulsion will exist between conductors 96 and contact'arm 24. vThenet result is to drivevcontact arm`" 24 downward. Movable contact 16 rocks about' its rearedge as illustrated in Fig. 5 and contact armi-24 moves bodily'downward, s'lot 28 accommodating-limited'y motion of arm 24 relative to pivot 26 duringthis opervation'. The stroke isl sufficient, however,y so thatthe spring pivot points 37 in member 24 moves overy center,l

withf'respect to the extreme left-hand andthe extreme righthand reaction points of those springsin member f= 30. The `over-centering of these springs. tends to ldrive member 2'4 counterclockwise about its pivot-26. However' at thismoment the 'electrodynamicM force producedby currentthrough member 24having' been great'enough--- to overlcenter springs 34 and 36, is sufficient to overcome# that opening spring bias. The degreeof this over-center#- mayfbc adjusted so-that the moving cont-acty arm 24 starts its openingrtravel for. separating-contact 16 from contact 18 at an appropriate level of currentduring the decliningportion ofan alternating-current halfwave.' The initial separation should occur suiciently in advance of the 'Zero cross-over ofthe alternating-current wave for consistentl arc-interruptionto` be effected but it shouldnot be so early as tocause excessive arcing Certain current directions `were assumed in Figs. l and 4 to showthe downward forces which are produced-v electrodynamically by heavy currents.- l Thesame forces, in the sameedirections, are produced during moments when the alternating vcurrent `vwave' producesfoppositelydirected currents in all these conductors.v

It mayvnow be assumed that the current has declined sufficiently for springs 34 and 36 in one of the poles to swing its contact 16 away from-the fixed contact 18. The moving'contact of that pole will then appear as illustrated i'nfFig. 6. vHoweven'this condition applies to only'one'individualpoler yThe contact arms of the other pole's'will'not open at this'instant when'used in a threephasefcircuit' The'current' in the 'other poles is likely to be higli- (Ldepending on the nature of the short circuit) -at the-instant-that"the-current inthe opened polev passesthrough zero. At this instant the contact arms inthe ad- .l

joining poles will remain unaffected if their currents are agarra@ lowior they will'be held down during the remainder-of the heavy-current portions of their current'wavesi If I they are subjected to severe current overload,- they will` be released subsequently `for opening in the manner iiidicated in'Fig. 6.`

irrespective of whether therel is a heavy current in lonlyr j. one 4of the poles or heavy currents in multiple poles, the

current-responsive bimetal or bimetals will be heated and will cause operation of thejcommon trip bar. AIn the contactv operating vmechanism Ain Fig.v,9, all carriers 30'will be automatically operated in the contact vopening direction. TEach-of the contact arms"24 vthat previously as-- sum'edfthe position of Fig. 6`due to a severe overload then assumesthe position in Fig. 7. Those contact carrying arm 24 of poles not subjectedyto severe peak overload A currents thenappearas in'Fig. 8. e

It will be understood that the kind of overload which brings into play the electrodynamic action represented in ,y Figs. 1 and'5 williordinarily be a severe overload, of the order" of tento perhaps l00`times` the tripping `level'fo'r which the bimetals are designedfto respondin'the case ofv moderate overloads.'1For"`example,"a circuit breaker f1 whose bimetals` are designedlto tripthe circuit breaker' for a persistent ampere overload current would nor:f-"l mallynot respond electrodynamically to produce the kind*v`l` of operation represented in` Figs. l5 land- 6 except for much heavier currents. This type of operation could be/made effective only 4when the curren't' "reaches' somethingin exmuni/level." For currents below'fshuch Velectro,iyr'iuriic e f'fu'nction as inv conven-'"""" tional circuit breakers. ",Followin l A.. operation,"signifyingeithr `a;persister'it 'modest' overload 'f or a shot-'circuit,"`all of thejf'cntfact 'carriers V310,'wjonl'd appearas in Figs.`7 andf8. The 'manual lever '48 con-` tripping level, the birnetals Wo ventionally moves' to a trip indicating position. In addiV tion to this trip, indication, the present invention prof* vides a short indicator. A shaft 102 carried by cover A 7 v 104l (Fig. 7) is provided with three members'106 having depending portions in the opening path of the respective ,contaet-'c'arrying varm 24 of its poler following a short# circuit tripping operatit'in.` The member 106 of the center pole is provided with a legend Short that is swung into view through an opening 108 in the cover 104. l Normally, spring 110, acting between 'at least'o'ne of the members" 106,'and the cover 104, is effective' to keepall of the mern' bers v1.06 in their'norrnal'position in which thev fshorty l indication isrotated away'mfrorn the 'window 108.

A review of the operation" of the threepole circuit breaker inea three-phase circuit 'may provehelpful to a; better understanding of the basic anddetailed concepts.

involved. Fig. llillustrates this application.

The three waves of alternating current A, B and C vare 'y shown displaced in time. At a time (t) a shfort"l circuit may'develop.' Let it be assumed to be a"'single-`4 phase short-circuifbetween one phase line and"ground.`

Considering phase A, the current that flows rises vir` tually immediately (depending on the nature of the distribution line) to AU). This is above the level (I) which represents the minimum current level eiective to overj centerv springs'ily and 36 by electrodynamic action, 'and the pole `of the circuit breaker'c'arrying phase A- shifts per Fig. 5. The holdd'own electrodynamc'bias continues to hold fthe contacts'together, u'ntil 'the current -drops' to level', which is the'poin't at which the opening spring bias Aothe springs 34 and 36 in the conguration of Fig.-

Further decline of the 'I 5 is equal to the hold-down-bias. current allows the over-centered springs to drive the oontacts apart. The contacts separate far apart (Fig. 6) before the wave A reaches-zero.- The voltagewave will have little tendency to restrike an arc, becauseithe ionizaf tion produced by the relatively low and declining current A(o) is limited, compared to that which.' would develop ,ff if an attempt were" made to interrupt the short-circuit 7 current earlier in the cycle. This is self-evident where high levels of current are considered. It is perhaps less obvious were the interruption attempted with a low, but rising/current. Such low current produces an arc that is sustained during `the ensuing rise to peak current `and during its decline to zero in a circuit breaker unaided by air blast or other special apparatus for breaking the arc. lt is not enough to part the contacts when the current is low; it is important to open the contacts during the decline so that the arcing time before the zero cross-over is minimized, consistent with adequate separation of the contacts to avoid restriking.

If a single-phase short-circuit is considered to develop in phase B at time (t), the same operation takes place that has been described or phase A. The contact arm 24 is electrodynamically shifted and the springs 34--36 are over-centered promptly, because the eurent at that instant exceeds level I. The contacts are held together and no arcing occurs until the current declines to level I at B(o), when the contacts start to part under spring bias, accompanied by limited arcing. Arc interruption is cornpleted by the time of the zero cross-over.

A single-phase short-circuit in phase C at time (t) produces Ionly moderate curent flow at that instant. The current declines through zero and then rises. Only when the current reaches level l does the operation occur such as is described for phases AV and B.

In leach phase A and B considered separately, interruption occurs within a half cycle. In phase C a slightly longer time is needed as shown. p

In the case of a two-phase short, and Ain three-phase shorts, Avarious phase shifts occur between the shirt-circuitV currents fof the4 different phases A, B and C. However,

l the basic "operation is not different from that described.

The birnetals are heated by the current surge and cause tripping of all the poles whether they were involved in the short-circuit, or not. The action of that trip-onetrip-all operation of the three-pole operating mechanism in Figs. 9 and l() is inherently slower than the operation of the mechanism in Figs. l and -8. If there is any tendency for the three poles to trip together, faster than the individual electrodynamic tripping mechanism, suitable delay may be imposed, as 4by added delay element 78. The directly heated bimetal illustrated may also be replaced by conventional indirectly heated bimetals, for additional delay. It is desirable to have delay, but only enough to be sure that the trip-one-trip-all mechanism will not function during the short-circuit operation in any of the phases, as described.

The foregoingillustrative embodiment of the invention represents an exemplary form presently contemplated but it is naturally subject to varied modification and application; and consequently the invention should be broadly construed in accordance with its i'ull spirit and scope.

Having thus described .our invention, what we claim and desire-to secure by Letters Patent is:

l. Current responsive contact opening means for use with alternating current, including a pair Iof separable contacts, spring actuated contact-opening means normally effective toclose the contacts and having electrodynamically actuated means effective during a half cycle of overload current to change said spring actuated means into condition to bias the contacts in the opening direction in response to a predetermined instantaneous overload cur- Y l rent level, electrodynamic contact biasing means including a conductor in series with the contacts eiective to hold the contacts together during instantaneous current levels comparable to said predetermined level, despite conditioning of the contact-opening means to bias the contacts Iopen, the bias of said electrodynamic biasing means declining during said half cycle and the electrodynamically conditioned spring actuated contact-opening means thereupon becoming effective to part the contacts.

contacts, and contact-opening mechanism including a current-responsive element responsive to a predetermined instantaneous level of overload current during an altermating-current cycle for conditioning said mechanism to' open the contacts at a later time in the alternating current cycle when the current has declined to a more readily iuterruptable level, said mechanism also including current-responsive means arranged to oppose the opening force of the contact-opening mechanism and effective to hold the contacts together during the time when the current remains excessive and until it declines as aforesaid.

3. Current-responsive contact-opening means for use with alternating current, including a pair of contacts, one of said contacts being carried vby a movable contact arm, electrodynamic means including said arm actuated by instantaneously high levels of current for biasing the contacts together,A and spring-actuated contact-opening mechanism having electrodynainically actuated means responsive to short-circuit levels of instantaneous current during an alternating-current cycle for operating said mechanism to apply opening bias to the contacts, said electrodynamic means being arranged to act in the direction opposite said opening bias and with sufficient force to hold the contactsV together during the flow of instantaneous levels of current in excess of that which is effective to activate the opening mechanism, the contacts thereafter opening at a time later in the alternating current cycle when the current has declined-and the opening spring bias exceeds the reduced opposite-acting electrodynamic bias.

4. A current intermpter for alternating current, includ- I i ing a pair of contacts and operating means for closing and opening the contacts, said means including an` over center spring device normally biasing the contacts together when the contacts are closed, electrodynamic current-responsive means providing driving energy for overcentering the spring means during an alternating current cycle in response to an instantaneous level of excess current, thereby providing spring bias to contacts in the.'

a. pair of contacts, one of said` contacts being carried by 'g a movable Contact arm, electrodynamic means for biasi' ing the contactsV together and spring-actuatedcontactopening means including an element responsive to a predetermined instantaneous severe-current level of an -alternatrng current cycle for conditioning said mechanism to open the contacts later in the cycle after the current declines below the Ilevel for which-said contact-holding means is effective, said electrodynamic biasing means being disposed 4to oppose the opening of the contacts by said contact-opening means.

6. Current-responsive contact-opening 'means for use with alternating current, including a pair of contacts,

one of said contacts being carried by a movable contact arm, electrodynamic means for biasing the contacts together, contact-opening means including spring meansy acting on said arm directly and normally biasing the contacts together, and an element responsive to an instantaneous severe level of current in a cycle of alternating current for reversing the bias of said spring means so as to act in the direction to open the contacts but this spring bias being effective to cause actual parting of the contacts only later in the cycle after the current declines andthe resulting electrodynamic bias falls below the# spring bias. l

7.A Curent-re's'ponsive contact-opening means for valtern'ting current use,including a pair .of contacts, one of saidv` contacts being carried by a movable contact arm, electrodynarnic means including said arm and fixed conductors in series with said contacts for biasing the contacts together, electrodynamic contact-opening means including an over-centering spring mechanism and a sup port. lfr -said contact arm allowing movement thereof about the contacts as a fulcrum in response to an instantaneous severely high level of current during'a half-cycle of alternating current, and the over-centering spring-mechanism being over-centered by that movement of the arm.

so as to bias the contacts apart. andthe electrodynamic means vincluding said arml and said xedconductors bei ing 'disposed to oppose said opening bias, actual contactY separation occurring laterwithimthat half-cycle of alternating c'urrent'vvhen the electrodynamic lbias has declined below 'the contact-opening spring bias.

8. Current-responsive contact-'opening 4means. for luse with alternating current,V includingV a-pairfof contacts, one Vvof said contacts bein'grcarried by a movable contact arm, electrodynamic means including said arm-responsive to the currer'ltftherein` for biasing the contacts together;

andfcont'act-opening mechanism including an. element responsive to a predetermined high instantaneous level of current lfor promptly. conditioning said mechanism to open .the contacts at a later time in the alternating'curent cycle.,"vvhen`said contact-holding means V'is overpowered by said contact-'opening means, said electrodynamic biasing means being disposed to oppose the opening of-i the Contact said contact-opening means.

f te t carrierforsaid movable ycontact arm electrodynainic." meanslactu'at'e'd by' instantaneously high levels of shortcircuit current for lbiasing the contacts together, and

spring-actuatedVV contact-opening mechanism acting between said-contact' arm and said contact arm carrier and having electrodynamically actuated means responsive to an instantaneous shortlcircuit-lev'el of current for prompt ly conditioning said spring-actuated lmechanism to` open..

the contacts laterin the same alternating current halfv y cycle when 'the current has ydeclined belowthe levelfor which said eectrodynamic biasing means is eiective',

said electrodynamic means being arranged tol oppose said contact-opening mechanism, the contacts thereupon opening While the manual operating means remains in its con` tacts-closed configuration, and an indicator operated in response to said electrodynamically actuated means to signal suchopening ofthe contacts.

l2. A multi-polev circuit breaker having, in each pole thereof, a pair of contacts and a current responsive trip- ,y ping element, coordinated'operating meanscontrolled by said current'responsive Aelements for causing the contacts of all the poles to move to their open positions in response -to an overload in any of the poles, an individual i ,spring-powered mechanism in each pole conditioned by an instantaneous current exceeding a predetermined heavy current-level for driving its related contacts apart', and electrodynamic means in each pole disposed to restrainy the thus conditioned spring-powered mechanismof that pole and eiiecu've to hold the contacts together QQAQur'ren't-responsivecontact-opening means Vfor use with alternating current, including a pair. of contacts;

one {of-saidcontactsbeing carried by'a Ymovable.eontact' Y arm, yelectro dynam'ic means includingksaid arm-respon: sive "to the current therein for vbiasing the contacts together, and'contact opening mechanism includinganfelen ment responsive to a; predetermined high instantaneous level of current for promptly conditioning said mechanism to open the contacts at a later time in the alternating current cycle when said contact-holding meansv is overpowered by said contact-opening means, said conditioned-contact opening mechanism and said holding means arrangedzto oppose each other and being related" to eachother to release the contact arm within an' overload half-cycle and at-a' time suilciently in advance of the alternating current cycle passing-through zero so that the Contact arm has moved to space the contactsapart amply'toavoid restriking'of anare. i

l0. Current-responsive contact-openingimeans for alternating current, including apair of contacts, one of saidvcontacts being carried by a movable contact arm," and'manua'loperating means for said arm to-openand` close the contacts, saidmanual operating means includy ing'a .carrierfor said movable contact arm electrodynamic'means actuated by instantaneously high'levels of short-circuit f current for-biasing the contacts together, and Vspring-actu'ated contact-opening mechanism. acting hetweensaid 'contact arm and said contact arm carrier and having electrodynamically actuated means responsive to an instantaneous-short-circuit level 'of current for promptly conditioning saidV spring-actuated mechanism to open-the contacts' later in the s ame alternating current half-cycles-whenthe current has declined below the level` v for which-saidelectrodynamieV biasing means is effective,

the contacts thereupon opening while the manual operating` means remains-in its contacts-closed congurationsaidelectrodynamiebiasing-means' being arranged .to 'oppose-the opening of the contacts 4byI saidcontact-opening y mechanism ll. Current-responsive :contact-opening means `for V'alternatir'ig current, Yincluding a -pair of contacts,17V one of said manual operating means for said arm'rtopenandcl'd'se` the contacts, 'said manual operating means including v"a' `contacts Abeing carried by a"..movable l'cdntact"arm,"and

during such current excess, the spring-powered mechanism being 'ineffective to part the contacts of that individualpole until after the current. of thatpole has declined and the electrodynamic holding force is overcome by the spring-powered means.

"an indilidlal Spring-Powered mechanism in each pole`v` rendered effective by such heavy current levels' for driv-f. ing its related contacts apart after the current of that" i pole hasdeclined suiciently so -that the electroclynamic' holding means is overcome by the spring-poweredrneann' 'i said electrodynamic holding means being arranged to oppose the opening ofthe contacts by the spring powered means Oi; the related pole only, said operating means""` and said coordinating means having an inherently slower operatingtime vthan said spring-powered mechanism "so as to operate only after the operation of Aany individualY spring-powered mechanism that is rendered effective by said=predetermined excessive current.

14. A multi-pole circuit breaker for alternating curprents,-including a common operating mechanism for the i i' Several poles to open and close the contacts thereof and including a releasable member,` a tripbar common to all of the poles in control relation to said releasahle member,- each pole. including a pair of contacts, a currentresponsivefbimetal, and a movable contact-carrying arm *for one of the contacts of that-pole, electrodynamically controlled means operative individually on each armffor' driving the contacts apart, said electrodynamically controlled means being conditioned to open the contacts inresponse to severe instantaneous current excesses and being operative to open the contacts later duringV such excess half-wave of alternating lcurrent when the current has declined and ris approaching zero. y

l5. multi-pole' circuit breaker" for 4alternating,cur-4 rents, including'a common operating 'mechanism for' th l"several poles'to o'perf'and close the contacts tliereofy'al"l tripping mechanism common to all of the poles operative to cause automatic opening of all the contacts in response to an overload, said mechanism providing a trip indication, each pole including a pair of contacts, a movable arm carrying one contact of said pair, a current-responsive device in control relation to said tripping mechanism, each pole also including an individually electrodynamically controlled means operative on the related contact arm individually for driving the contacts of that pole apart in response to a severe instantaneous current excess, and an indicator additional to said trip indication operated by any of said contact arms to evidence operation of the individual electrodynamic means in response to severe current excesses.

16. A multi-pole circuit breaker for alternating current use having, in each pole thereof, a pair of contacts and a current responsive tripping element, operating and coordinating means for opening and closing the contacts and for causing the contacts of all the poles to move to their open positions automatically in response to an overload in any of the poles, electrodynamic means in each pole for biasing the contacts closed, and an individual spring-powered mechanism acting directly on the contact carrying arm in each pole and rendered operative by a severe instantaneous current level for driving its related contacts apart before the mechanism-operating half-wave of alternating current has dropped to zero.

17.` A multi-pole circuit breaker for polyphase circuits, including mechanism for concurrently operating the several poles to open and close the contacts thereof, a -trip mechanism for automatically causing said operating mechanism to open the contacts of all the poles, a current-responsive element in each pole in control relation to said trip mechanism, and a contact-carrying arm for one contact Yof each pair of contacts, electrodynamic means operative to Vopen the contacts of an individual pole in response to excessive current Atherein when the instantaneous current of that pole has declined, said contact-operating mechanism being thereafter elective after an inherent delay timefor operating the contacts of all of the poles into their open-circuit positions, the delay time being long enough for each pole in the polyphase circuit to be operated electrodynamically.

18. A multi-pole circuit breaker for polyphase circuits, including a common operating mechanism for the several poles to open and close the contacts thereof and including a releasable member, a trip bar common to all of the poles in control relation to said releasable member, each pole including a pair of contacts, a current-responsive bimetal, and a movable contact-carrying arm for one of the contacts of that pole, electrodynamically actuated means including the related contact-arm to bias the cont-acts of each individual pole together during excessive levels of instantaneous current and for driving those contacts apart after the current has declined, said bimetals and said common trip bar and said` common contact-operating mechanism being effective after an inherent delay time for opening the previously unopened contacts of all remaining poles, the delay time being sufiicient to allow for the individual poles to be operated electrodynamically.V

19. A multi-pole Vcircuit breaker including operating mechanism for concurrently opening and closing the several poles, coordinated tripping means responsive to overload current in any of the poles to cause automatic opening operation of said operating means, and faster-acting electrodynamic means individual to each pole responsive to the current therein to open the contacts thereof.

20. A multi-pole circuit breaker including operating mechanism for concurrently opening and closing the several poles, coordinated tripping means responsive to overload current in any of the poles to cause automatic opening operation of said operating means, and faster-acting electrodynamic means individual to each pole and responsive only to currents of short-circuit level to open the contacts thereof, said operating mechanism including means providing an indication of automatic opening of the contacts, and an additional indicator operated by said poles severally for signalling electrodynamic'operation of an individual pole and thereby indicating occurrence of a short-circuit.

2l. A multi-pole circuit breaker, including in each dividually relative to its contact carrier to open the related contacts, and relatively delayed current responsive means for concurrently operating all said contact-arm carriers in the direction to carry the related contact arms in the contact opening direction.

22. A multi-pole circuit breaker especially adapted for polyphase circuits, including a pair of contacts in each pole, individual fast-acting short-circuit-current-responsive mechanisms in each pole for parting the contacts thereof at a favorable time in the current cycle of that pole independently of the individual mechanisms of other associa-ted poles of the multi-pole circuit breakers and of the phase of currents that may be carried thereby, and relatively slow-acting mechanism responsive to both moderate overloads and short-circuit currents for concurrently operating all the poles inthe contact-opening direction and thereby parting the contacts of poles not previously opened by one of said individual short-circuitcurrent-responsive mechanisms.

23. Current-responsive contact-opening means for alternating current, including a pair' of contacts, one of said contacts being carried by a movable contact arm, and manual operating means for said arm to open and close the contacts, said manual operating means includ-V ing a carrier for said movable contact arm, electrodynamic means actuated by instantaneously high levels of short-circuit current for biasing the contacts together, and spring-actuated contact-opening mechanism acting between said contact arm and said contact arm carrier and having electrodynamically actuated means responsive to said instantaneous short-circuit level of current for Ipromptly conditioning said spring-actuated mechanism to open the contacts later in the same alternating current half-cycle when the current has declined below the level for which said electric-dynamic biasing means is effective, the contacts thereupon opening while the manual operating means remains in its contact-closed coniguration, said manual operating means including a reset device for restoring said spring-actuated contact-opening mechanism to its contact-closing configuration While the manual operating means is in its contacts-open contiguration.

24. A multi-pole circuit breaker for alternating currents, including a common contact-operating mechanism for the several poles to open and close the contacts thereof, a tripping mechanism common to all of the poles operative to cause automatic opening of all the contacts in response to an overload, each pole including a pair of contacts, a movable arm carrying one contact of said pair, a current-responsive device in each pole in control relation to said common tripping mechanism, and each pole further including an individually electrodynamically controlled means operative on the related contact arm individually for providing energy for conditioning the contacts of that pole to be driven apart in response to a severe instantaneous current excess.

25. `Current-responsive contact-opening means for use with alternating current, including a pair of contacts, one of said contacts being carried by a movable contact arm, electrodynamic means for biasing the contacts together, contact-opening means including spring means acting on said arm directly and normally biasing the contacts together, and means including an element varranged clectrically in series with said contacts for electrodynamically providing the driving force in response to an instantaneous severe level of current during any half-cycle of alternating current for reversing the bias of said spring means so as to act in the direction to open the contacts but this spring means being effective to cause actual parting of the contacts only later in the half-cycle after the current declines and the bias resulting from said electrodynamic biasing means declines below the spring bias in the contact-opening direction. v

26. A multi-pole circuit breaker for alternating currents, including contact-operating mechanism for the several poles to open and close the contacts thereof, overload responsive means including `a current-responsive element in each of the poles operative to effect operation of said contact-operating mechanism for automatic opening of all the poles substantially simultaneously in response to an overload in any pole, each pole including a pair of contacts, a movable arm carrying one contact of said pair and each pole further including an individually electrodynamically controlled means operative on the related contact `arm individually for supplying energy for conditioning the contacts of that pole `to be driven apart in response to a severe instantaneous current excess therein.

427. A multi-pole circuit breaker for alternating cur rent, including in each pole a single-poled overload current-responsive release means, a pair of contacts, and mechanism released under control of any one or more of the single-pole overload responsive means for etecting opening of the contacts of all the poles substantially simultaneously, each pole including an arm carrying one contact of the related pair of contacts, Velectrodynamic means biasing the contacts thereof together, contact-opening means including spring means acting on said arm directly and normally biasing the contacts of that pole together, `an element arranged electrically in series with the contacts of each pole and responsive to an instantaneous severe level of current in a cycle of alternating current for reversing the bias of said spring means so as to act in the direction to open the contacts of that pole but this spring bias being effective to cause actual parting of the contacts of that pole only later in the cycle after the current therein declines and the resulting electrodynamic bias falls below the spring bias.

References Cited in the tile of this patent UNITED STATES PATENTS

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