US2647972A - High-voltage circuit breaker - Google Patents

Description

Aug. 4, 1953 J. D. WOOD ET AL HIGH-VOLTAGE CIRCUIT BREAKER Original Filed Jan. 11, 1947 3 Sheets-Sheet 2 Attorneys 1953 J. D. WOOD ET AL HIGH-VOLTAGE CIRCUIT BREAKER 3 Sheets-Sheet 3 Original Filed Jan. 11, 1947 ULILJHUHLIHUIUUUUHUUUWLJHH S M Q m n NIOWP E03 0 W dH W CA D h w s.. m OP 5 A Patented Aug. 4, 195 3 urea-veer Joseph-D. llarby, Cas

well,,Philadelphia, Pa., assignors to I. T. E.

Circuit Breaker Company, v Pliiladelphia, Pa}, 3'

cbrporatiofiof Pennsylvaniai I I I J Original applicationflanuary. 1 1-," .1947",. Serial :No'. 721,648,;npw ratentNo. 2,613,299, dated Ct -i her 7, 1952. Divided and this application June 4, 1947, Serial N 0. 752,427

Ourfpresent invention which advisionfof our application Serial No. 721,648, filedJanuary 11, 1947, now PatentNo. 2,613,209, datedoctober 7, 1952, relates to high voltage; high capacity; circuit'breakers, and more particularly to circuit breakers having an interrupting rating oi 50,000 kvaand better in anyvoltage range between 2300 and 5000 volts and at current ratings of 600and 1200 amperes. v

Essentially our'invention is directed to the productionof high voltage high capacityair break switchgear in such a manner as to provide" the increased interruptingcapacity required by means of the simplest elements which are manu factured and assembled by mass v production methods in the most economical way. a i

This novel circuit breaker includes a simple unitary arc chute structure made as a single unit provided with a disconnect and so arrangedthat' it may readily be mounted on the circuit breaker and connected thereto or removed-therefrom as a whole without the necessity'for'special tools.

Ournovel arc chute thus combines the essential ideas of simplified construction ior'greater economy and simplified arrangement in theform bf a single unit assembly which may readily be mounted on any circuit breaker ofthe class to which the'arc chute is to be applied. The are chute may readily be removed for inspection' of the contacts of the circuit breaker or for replacement or repair of anypart that may re-" quire such replacement or repair.

In a high voltage high capacity. circuit breaker," one of "the most'important problems is the provision of proper insulation and the avoida'nce of any dielectric breakdown which may: occurinthe operation of the circuit breaker.

An important object ofour inventionythere fore, is the novel arrangement of thenarc chute so that the front are runner or arcing thorn is entirely disconnected from the back terminal in 5 any position of the circuit breaker; whether closed or open. This is achieved by so arranging the movable arcing contact that it may transfer the arc to the front are runner solely: byireas'onz" of its proximity thereto during a portionrcfthe opening movement; the arcing contact at the completion of the openings movement-moves suf ficently far away from the front arcqrunner'so' that 'there'is no connection or likelihood ofany connection therebetween; ",This'front ,arcrrunner is entirely disconnectedand .thewfrontlofithe arc-1' t member "is completely safe forhandlin'g even while the circuit breaker is racked into posi tiQH-T plates on 'each side Thefblow out mechanism comprises essentially a"U-'shaped ironstructure, the base of which is V surroundedhy'the blow-out coil and the legs of which extend out perpendicularly to the panel on which the-circuit breaker is mo of the- -U-'shaped iron structure carry the arc chute';'-and the arc'chute may he slid on to or I off these 'legs for placement or removal.

' The'blo'w-out iron circuit is made up of a core around which the blow-cu ends-of the co're are attached the side plates which project forward nearly the entire depth of the arc chute. or' 'runners and supports for the arc chute and the complete assembly is thus supported directly on the back panel support.

Her'eto'iorein the construction of blow-out mechanisms, it has been found that a concentration'of flux at the coil end occurs with solid side plates 'so'that only thecoil end of the arc chute is used;

Accordingly,another object of this invention is the novel arrangement of the blow-out iron in such a mannerthat the flux is relatively evenly distributed overall of the side plate area so that the-entire arc chute is used.

In actual operation we ha y H g I, ve found'that an economical combination of f our 4/ inch thick 7 gave a fairl tribution over the full length.

In addition, and in out effect, auxiliary b tach'ed to the runner chu't'e'and 'divert part ofthe main down into the vicinity of the conta Bythis novel construction the b ture'and the arc chute'structure are mechanically separated and independent of each other so that the-arc chute is much lighter and easier to remove low-out iron 'plates are atfor inspection and so thatthe blow-out construe tion acts as a support Accordingly an ob construction of a high capacity highvoltage"cir le of interrupting arcs "of y 01' even-better, andeconomical m design and construction, capable of unitisub' assembly manufacturing operation} and soreducedin cost that its price may compare "favorably and" at times even be lower '7 for the arc chute.

50,000JkV a. lcapait unted. These legs t coil is wound; to the Theseplates also act as slides y even flux dis order to enhance the blow-' strip on each side of the arc,

low-out strucject of ourinvention is the I than that of many lower capacity lower voltage circuit breakers on the market today.

In actual practice, the commercial circuit breaker hereinafter described, which was designed for 50,000 kva. interrupting capacity has been subjected to four successive tests at 63,000 kva. interrupting capacity although standard practice requires only two successive tests at the full rate interrupting capacity. I

Furthermore, by changing the material of the arc chute plates it was discovered that the interrupting capacity of the breaker was greatly increased. For instance, in one case, a breaker that would interrupt 65 mva. was found capable of interrupting current in excess of 125 mva. by no other change except the change in the material of the arc chute parts.

It is therefore an object of this invention to provide superior materials for arc chute parts.

In addition, in high capacity circuit breakers which are designed to interrupt arcs of substantial kva., it frequently occurs that the blow-out mechanism will effectively move the arc into the arc chute causing it to be extinguished at or near the full rated interrupting capacity, while the blow-out mechanism is not able to perform the job of moving the arc up into the arc chute at very low current values represented by the charging currents of transformers or cables owing to the fact that the flux through the blow-out mechanism or coils is very low and ineffective. This has resulted, in some prior art circuit breaker construction, in the addition of further devices such as puifers and the like to assist the blow-out coil in performing its operation. Alternatively the prior art blow-out coil has been provided with sufficient turns to obtain the required ampere turns even for low current failures. Such prior art devices have thus utilized the expedient simply of assisting an inefiective construction by adding additional construction thereto rendering it unnecessarily bulky.

Another and primary object of our invention is the arrangement and construction of the blowout mechanism of our novel circuit breaker so that it may move an are at low interrupting current as well as an arc at high interrupting current properly into the arc chute so that the same may be extinguished; the said blow-out mechanism operating for this purpose over the entire range of interrupting capacity of the circuit breaker without the necessity for additional aid or other expedients. This we achieve in part by passing only a portion of the arcing current through the blow out coils, the percentage of such current decreasing as the fault current increases. For very low value currents, we provide a separate arc chute.

The foregoing and many other objects of our invention will become apparent from the following description of the drawings in which:

Figure 1 is a side view in perspective, partly broken away showing our novel circuit breaker assembled and mounted on a truck.

Figure 2 is an enlarged side front view in perspective partially broken away showing the lower terminal assembly, upper terminal assembly, the blow-out coil assembly and the movable contact bridge assembly.

Figure 3 is a side view of the arc chute assembly.

Figure 4 is a front view of the arc chute assembly.

Figure 5 is a top view of the arc chute assembly.

Referring now to Figure 1, our novel circuit breaker is shown preferably mounted on a movable truck. The movable truck comprises a back main supporting structure which includes the vertical support members l0 and II connected together and interbraced at the lower end by the Masonite panel I2 and at the central and upper portion by the cross-bars l3, l4 and 15 which are connected as shown, in any appropriate manner, as for instance by bolts and nuts to the vertical members I0 and II. The lower ends of the vertical members [0 and H are provided with bearings H and 18 for the shaft l9 which carries the rear wheels 20 and 2| of the truck. The vertical members It! and H together with the cross bracing elements above described and the wheels 20 and 2| constitute a single unitary member of assembly.

Certain of the assemblies are standard and require no specific discussion here. Thus, the control panel assembly 4'! and the trip unit assembly 48 may be substantially standard units which require no specific description. Also, the control switch contacts indicated generally at H: of Figure l and the grounding contacts II, 12 of Figures 1 and 2 may be standard units. The essential elements as above pointed out with respect to these units is the unit assembly arrangement which is possible with the construction herein shown.

The rear end of the operating mechanism assembly 46 is supported on the cross bar 14 which is held by the bolts 15, I5 across the top of the lower panel :2. Cross bar 14 also provides means for supporting additional assemblies. The specific novel assemblies or sub-assemblies shown in Figure l and forming an essential part of the novel circuit breaker here shown are the lower terminal asesmbly shown in Figure 2, the upper terminal assembly of Figure 2, the movable contract arm or bridge assembly of Figure 3, the blow out assembly of Figure 2, the arc chute assembly of Figures 3, 4 and 5. The specific operation of these individual assemblies renders possible the entire high speed high capacity circuit breaker which our novel unit embodies.

The various assemblies above mentioned will be described in order, going from the bottom to-v ward the top of the circuit breaker without: specific emphasis on any one of the assemblies. over the other.

It must be emphasized, however, that an im portant feature of the circuit breaker is in thenovel are chute construction in conjunction with the novel blow out construction.

The operating mechanism utilizes as closely as possible the simple principle of the lever op-. erated switch with only enough addition thereto. to provide automatic response to over-current; conditions in order to trip the circuit breaker and also to provide a solenoid closing means. The. simplification of this operating mechanism makes possible the production of the inexpensive circuit breaker herein described.

Thus, while the arc chute assembly and the blow-out assembly make possible the high capacity operation and high speed operation which are esesntial to the operation of the circuit breaker as a whole, the simplicity of the other assemblies makes possible the economical and efficient construction.

The individual unit assemblies facilitate storage of parts preparatory to final assembly and thus make it possible to fill orders quickly.

Thus. the first sub-assembly which consists of the back panel and the back wheels 20 and 2| is essentially a simple flat member which may readily be stored anddoes nctitake' up any-tutstan'tial amount or space '(see Figure 1').

Heretofore, the diffi'culty encountered injpremanufacture of sub-assemblies 'injanticipation of future orders resided in thefact that the mainframe of the circuit breaker or o'therjjswitch gear usually was as big'as the circuit breaker itself, so that the manufacture and "especially the storage of the main 'frame presented [the same problem as the storing of an entire circuit breaker. No real economy was effected by' -pr'emanufacture of the main framesince'the entire circuit breaker could be stored just as readily.

By means of our novel device, the back ,panel and the rear wheels of the truck whihconstitute a single flat structure may readily be stored awaiting specific orders for assembly of Specific circuit breakers.

The truck structure'is' completed byimeans of a lower or bottom platform 23 which carries a front wheel 24 in the front swivelglti (Figure 1). The'bottom platform 23's secured at the rear end of the lower end of the vertical members l and l I above the bearings l'l and l' fl 'for the rear wheel. The bottom platform 23in connection with the back panel form the vertical supporting members I0 and l I and their interbracing structure and taken together withthe rear wheels 20 and 2! and the front swivel wheel 24 comprises the truck or mounting for the circuit breaker. Thus the bottom platform 23 and the front swivel wheel constitutes a single sub-assembly which may readily be stored without requiring any additional space and which may readily be attachedbytwo screws to the lower end of the vertical members I0 and H. I This type of unitary sub-assembly construction which may readily be interconnected with other element in order to make a. complete truck, facilitates modification and variation of sub-assemblies in order to meet the specific orders.

Thus in the event various control elements must be multiplied to a substantial-extent in the final circuit breaker thus requiring perhaps a custom built lower platform 2 3, ;19hi8510W61 platform 23 may be built-tmthe unique speci fications of the customer-and may then becombined with the standard back panehconstruction which is kept in stock. However the entire truck construction including the-first and second Sub-assemblies v des r -bedar bu' ltiin fu l anticipation of all requirements to which the particular 1 circuit breaker may; ba -put, .so that particular custom madeback or bottomgportions of atruck will be required only insexceptional cases. "The upper terminal assembly;;30,; and the lower terminal assembly 3! for. each of the three poles is formedfrom a single bar of copper of rectangular cross section appropriatelyinsulated by phenolic insulation as-describedmoregspecifically hereinafter in connection with-Figure 2. 'Each of the vertical members. l 0, ltand t'z is'rece'ssed at 33, "33 to receive the terminal members and accurately position the same. a v

Each of the vertical reinforcements" |0 ll and 32 is'a rectangular steel member so that while the recesses33f33 are cut out in the vertical reinforcement they are inc'i sed only in the o tion of the rectangular; steel. member which is normal to the back panel- 56. Thelegsofreach of"the"rectangularmembers l 0, j l and 3 2 carry thebolts d6, 36 which "engage-thefiangemembers 35-ofthe terminal element Esta tr the upper and lower terminal as- 13, which is'secined v H and 32 by the'bolt guide the truck into and.

snitlvmeiiiliers '3'0 r a d 531i tea-waste spas;

biased disconnect "contact "elements at, -at "also hereinafter more specifically described in con-- nection with Figure 1, but. shownalso in'Pa'tent Numberg2,'029;02'8. 'Ihe'i nterm'ediate "cross "bar to't e vertical members 'HI,

WU, also carries at its outer end thewheels 42 ,on anappropriate shaft eitensio'n 'the'reonthe said wheels 42 cooperating n th .0mma rwn out of 'the'.:compartment witnappropriate tracks properly; J I .Thje racking andindic'ator assembly shown enerally Lat 43 "of Figure 1 also *carries {the front wheels 344,, 1414 j to ride on 'Tthe guide tracks .of the cfompartineritiih .Whi'chithe. circuit breaker is "housed.

course has as many. poles as there are .upper and lower terminal assemblies,,.three in the particular instance shown, is p'rovided with contact elements hereinafter more particularly described in connection with Figure 2. I'hei-blow out coil assembly 53 which includes. the ,coil f5f4 ofIFigure '2 and the laminated blow outiron-legsii55,

mounted on the upper insulating vbackpanel- 56 also across the bars I15 and 7 l4 .and the "upper portion of vertical supporting members 10 =.and

Hand issupportedthereby, I

-Itis spaced. from. the. bars [0, ll, 32,, J4, and

15 by'the upper insulating back panel f55 which panel is securedacross the bars Mi, Ll I and -32 asshown in Figure 2, Appropriate openings: 59, Marc provided in-the panel 56 to permit; the terminal members 30 and 3| to project there through: in amanner shown in Figures i and 2.. The arc chute assembl 51 is-supported-.by' the blow out assembly 53 and particularly .by the laminated legs 55 of the blowout ironwhich ride between the bracing bars 58, 58 on each side of the-arc chute as shownin Figures 1v and 3, and as will be, more specifically described hereinafter in connection with Figures 1, 2 and 3. The are chute is entirelywsupported by the laminated legs 55 of the blow out iron on each side, being retained in position by the "latch assembly 6| (Figure 3) also'hereinafter more specifically described. a

All of the elements of the circuit breaker as will beseen from an inspectiontof Figurel, and of subsequent figures may be inexpensivelyma'de from ordinary sheet metal or cut from ordinary bars, and 1 no complicated casting or machining operation is required, thus leading to great economy in the manufacture and n assembly .of the device. s p

Also from the previous discussion it will i be seen that the assemblyv operation consists ofta number of units as above described, each of which may readily be. stocked and kept. in storagenwithout consuming an .undue amount ofsspacedand which may readilylbe assembled simply'lby a few bolt or". screw manipulating operations tointerconnect an entire circuit breakerifromthe .unit assemblies.

Lowcrter'mz'nal dsseiiit'zy' The 'idwertetmmai assen'itit is. shbwifis Figures 1 and 2 comprises a bar of copper I50 insulated by an oblong Bakelite tube II with a conductive inner lining into which it has been pressed. The front end I52 supports the movable contact bridge assembly 50 in a manner hereinafter specifically described, while the main disconnect contacts 38 are secured to the rear end The lower terminal 3I has the side flanges I56, I56 secured thereto in any suitable manner, to cooperate with the movable contact arm as shown in Figure 2. In the usual procedure for insulating a terminal bar such as that shown in Figures 1 and 2 phenolic insulation material is wrapped around the bar and tightly pressed thereon. This is a complicated process which must be performed on special machinery and by those having special skills in the field.

In the present construction, instead of wrapping phenolic insulation tightly around the bar I50, the flat tube I5! is used, said tube being provided with a conductive lining I62. This tube is placed over the bar I50 and then pressed into tight engagement with the bar I50 to provide the insulation cover therefor.

The principal reason for wrapping the insulation in the prior art was that no minute air pockets could be permitted since at high voltages these would result in Corona discharge, causing progressive dielectric resulting in breakdown of the insulation. Consequently great care was required in the wrapping of the insulation.

We have discovered that by using a sleeve of insulating material and making the inner surface of the sleeve conductive, the sleeve may simply be pressed down around the tube to conform with the contour of the bar and provide a completely engaging surface to surface contact thus according any deleterious effects resulting from any minute air pockets that may remain. Thus where the prior cost of wrapping such bars was in the neighborhood of $12.00 per bar and it was necessary to send the bar out to be wrapped by special machinery, our invention makes possible the insulation of the bar at the circuit breaker plant at a cost of about $1.50.

Upper terminal assembly The upper terminal assembly 30 shown in Figures 1 and 2 also comprises a bar I60 of copper having an insulating sleeve I6I mounted thereover in the same manner as previously described in connection with the lower terminal assembly of Figure 4.

The rear end of the bar I60 has the conformation I54. to receive and. hold the main disconnect contacts 38 shown in Figures 1 and 2. The front end of bar I60 has secured thereto the stationary main contact I61 and the stationary arcing contact I06 (Figure 3). The upper end of the front portion of bar I60 has secured thereto the insulating plate I having the upper slotted extension I10a. Connector I1I is secured in any suitable manner to the insulating blocks I65 and I68 but isinsulated from the contact bar I60 and the arcing contact I66 and stationary contact I61.

Connector I1I has a cut-away portion at its front end between which, and spaced from either edge, the forward end 208 of the movable contact arm 1, comes to rest when the contacts are in engagement as will be described hereafter.

M mqcble contact assembly In Figure 2 we have shown one of the contact deterioration and thereby arms 80. The contact arm comprises a pair of copper bars I80, I8I between which is secured, at the upper end by pin 205, the arcing contact arm 204. The movable arcing contact arm 204 is held in proper spaced relation by the spacer washers I84--I84, all of which are forced into proper current carrying relation by the spring washers 233-233. The upper inside edge of the copper bars I80I8I carry special arc resisting silver alloy contact blocks I85 which comprise the main movable contacts.

The lowerends of the bars I80 and I8I is provided with the registering openings to receive the pin I81 (Figures 1 and 2) which pin passes through the openings.

The pin I81 is provided on each side with a lug I (Figures 1 and 2) carrying the bar I9I which passes through opening I93a (Figure 2) of the side flanges I56. Compression springs I93 on each side are captured between flanges I56 on each side and the lug I90 of pin I81 on each side thus forcing the lower end or pivot of the contact arm out toward the right with respect to Figures 1 and 2 at the pivot point I86.

The contact arm eifectively pivots about pin 200 (Figure 1) which is connected between the arms I8I and I80 and which carries the end of link 5I connected to contact operating arm 52. Thus, compression springs I93 force the contact arm 80 to rotate counterclockwise about the pin 200 within the limit of the length of slot I88 on the lower terminal and thus forces the movable contact I85 into close wiping engagement with the stationary contact member I61 (Figures 1 and 2).

In any position of the arm 80 other than the closed position of the arm 80, compression springs I93 push the pin I86 over to the far right end slot I88 of the lower terminal of Figure 2. When the contact arm reaches the closed position of the contacts, the movable contact I85 bears against the stationary contact I61 and as the link 5| forces pin 200 and contact arm 80 into the closed position, the spring I93 yields because of the slope of the angular slot I88 to permit the wiping action to occur between the contacts I85 and I61 and the contacts to close firmly.

The forward end I52 of the lower terminal is provided with silver alloy inserts 202, 202 to bear against the inner surfaces of arms I80, I8I of contact arm 80. Thus it will be seen that no pigtails are use, but appropriate elements are used on pin I81 to squeeze the lower ends of arms I8I, I80 against the insert contacts 202 on the lower terminal.

The contact springs I93 are located close to the pivoted stud I81 which is a distinct advantage because they are well away from arcing zone. The connection of link 5I to the contact arms is at a point 200, as above pointed out, well above the center point of the arms 80, so as to make these contacts blow-on contacts as explained in the following description.

In ponse to a rise in currents, magnetic forces developed in these contacts tend to increase contact pressure at all contact points. The arcing contact arm 204 is pivotally mounted on the pin 205 between the contact arms I80, I8I and the spacer washers I84, and is provided with an arcing contact element 206 and the horn 201. The lower end of arcing contact arm 204 is connected by the floating pin 2") to the link 2 II which in turn at this lower end bears against the milled surface 2 I2 of the milled pin 2 I3 carried between the arms I80, I8 I.

Tension spring 2 I5 connected between lug 2I6 andspring eye 2 l 1 is: arrangedrto rotate link .21 I clockwise around the bearing furnished by th mil-led-portionliz. of pin. 213.- Thelug. 216; is adjustably mounted on screw 220 which in turn is received in the tapped openingt22l of. pin. 222 carriedjetween-the-arms [80,181. Rotationtof screw220 resultsin moving lug. 216; to change the tension of spring 215- and thus: increase.v the bias thereof;

Spring 2l5 thus acts on-links- 2| I; tocause the toggle 241-210-404 to collapse. in a direction to force the arcing contact 206 to the left. The full collapse of this toggle is prevented: by the adjustment of screw HO-which bears againsttthe end 225' of arcing contact arm 204. Tension spring 2l5, however, thus drives the arcing con.- tact element 206 out to the left with respect to Figure 3 where it will make contact. with the stationary arcing contact I66 before. the main contacts engage and where it will maintain contact with the stationary arcing contact until after the main contacts have separated.

Since the center 205 of arcing contact arm 204 is well above the mid-point thereof, a blow-on action of the arcing contact occurs, also thus 7 ensuring that the arcing contacts will remain firmly in engagement until the main contacts have separated;

The position of the arcing tips 206 above the main contacts I61 forms an upward loop in the circuit which tends to initiate a blow out action to start the arc upward when drawn.

In order to protect the lower terminal structure against any possible defect in the arc chute or blow out mechanism which would tend to drive an are down, an insulating shield 230 is provided secured to the screws I83 and flared out to protect the uninsulated portion of the lower terminal bar I50.

Spring 2l5 ensures that the movable arcing contact will move into engagement with the stationary arcing contact as the contact arm begins to open and before the main contact separates. The arcing contacts will then stay in en- :gagement for a substantial portion of the opening movement depending on the settingof screw 220 (Figure 2).

Blow out assembly -'I'he blow out assembly 53 comprising thetcoil 5'4 and the laminated blow out iron Elegs 1555a].- r'ea dy referred 'to in Figures 1 and :2, is shown *more specifically in Figure 12. The coil 54 is connetted by the lead 235 and bolt 12 36 'CFigures ,1 and 2) to t'h'eupperterminal-bar 1| so. The .opposite end of coil 54 is connected by :lead .238 to ext 'nsifo'n 11m on contact bar -|"H :passing lthrough a lot in the upper 'exten'sion :.I 7.022 :of insulating 'st'rip l -HI (Figure3'). Coil:54 is woundaon-anriron core 240 to which is secured the laminated blow out iro'n leg's 5'5 on either si'de.

, We havefound that preferably rour such:side pistes on each side ithick ensures ;a :proper -distiibiition of magnetic blow :out flux 'over the full length of the -side 'Splates. .-Also we have found that in order to obtain a proper blowout "without inserting to :much; impedance 1: in

is with" the ar'c, itiis desirable rthatrthe coil 4jc'on'sist of 18': turns 'ofs copper strips of; 5% x Ih'e side frame imembers 242, 242 (Figure :2) of the blow-out assembly aresecured' against the cor e' 240 by bolts 2-43 which: :also secure; the plates '55 against the core. :The" side iframe members 242 or the 'blow out assembly have secured therelietween the upper block 245 bye-mean ot .pin

2.46.. and the... low r. l ck not sh wn) y means fl'p n 4 nd plat .49jj y. means. fl g ifli g Block 245 and ts. or pon in q r hlqs are provided with ap ed p pinesjb me n f W ich. the entire lpwr t. as emb y me fb readily securedto the frame ot thecircuit brealg er. It Willtthus be seen that the entire blow; out assembly, may b eadil moun ed on. nd r mov d. from. he ircui b eaker a pa e unit.

Arc chute;

The blow-out. assembly serves as support-for the arc chute described in Eigures2, 3-, 4and 5 The are chute. assembly 51 mounted abovethe contact assembly 80 provides for a positiveand efiicient are interruption, It consists" of insula tion side walls 251, front and back: arcru em 29! and 290 respectively and a series of} ce ic plates mounted inspaced relation transve e of the a c path; nd; strong ma n tic l w b field to force the arc into the are chute.

The sides 2 51; (F gures 3- and 5). have fastened at ir lower r ion. adja nt t e ar e a a; i ner ar r s n i ti ice EW tZ-QQ at special composition hereinafter described. arc resisting plates 269 are chanifered along their up r ed es a il-.262 to. p ov de a s rai ht locking edge for the cross plates 2-611 and the sp ce s. 26 h ow r en s o the r ss plates 260 and the spacers 2 1 a e ap rop iat y s aped to fit the chamfered edge 262.

As the arc is driven into the chute by the magnetic field, it; passes rapidly through the arse):- tineuishing ceramic la e 2 hi h are ec.- taneular in sh pe t ir op and ave a one tapered lower edg ext din from t e cente of one side of the p a e to the low corn r on the opposite side of the Pl te- A e ami spac 26| is provi ed t sup o t ea h p ate and nos tion it with respect to adj ent pla s an fo m with the long tapered suriac of he p ate. a tr angular opening with the apex at the top tor the passage of the arc. Each plate with its spacer presents a decreasing area for the are a it rises and gradually squeezes it into a narrow 8191 3.01.

The platesrZBil are assembled alternately an interleaved relation and spaced tram ea h oth r so that the long tapered surfaces ,cross at the cent r or the chute directly above th Path .Q the are as it travels up the chute. As the arc passes the cross over point of the plates, it is forced into a zig-zag or sinuous path gradually but'r pidly in re sin {it l n th nd brin in it into co ta t :with lar r and la e ri tfa es of th pla shea mu t uebe za b undth edges of the plates which are .eifective in circuit interruption. The positive andgflicientarc interruption is afiected by the cooling, length ng and squeezing of the are -at ;nun erouspoints all along its path.

-Provision for the interruption of .low ,current arcsiis built intothe arc chute. Nomovin arts or auxiliary equipment are necessaryr Shortbir- ,cuit or normal over {currents .are' extinguished before the-movingarc horn 20,1 p,asses the front are 1 runner. The -.arc formed by curr ent s I ,of .low value is extended in the chute} beyond the .front are runner 218i and.eifectivelyconled and deionizedtbyla set of plates .322 (Figure.-.4) .located in .thewcurrent path.

. ,Arc travel toward the. front, of the QDPP i -volves, ,a transfer from I the arc tcpntact arm 20 1 to :the forward "are runner. The. absence of the re rn, con e n-from. t i rr nt e tt h s owe' lead is a new feature in high voltage breaker design. Without this connection, the dielectric strength of the open breaker is not dependent upon the arc chute, whose inner surfaces are bound to deteriorate through use. Without this connection, the are between the contact arm 204 and runner continues as long as the arc exists. On high values of current, the arc is extinguished before the arc contact arm 204 passes the runner.

Progress of the are up into the chute brings it in contact with the cross plates 260 which are shaped and assembled so as to cause the arc to follow a gradually increasing zig-zag form, thereby securing a long arc length in a short length of chute. Maximum length in a crosswise direction is realized at a point opposite with the top of the blowout iron side plates 55 where it enters a narrow confining slot 301. The length of the plates 268 above this point is used to cool and deionize the incandescent gases which result.

When the current to be interrupted is of low value, low magnetic action existing at that time is still sufficient. The are is extended by the long travel of the arcing tips and cooled by the specially located plates 322 below the front areing horn 29!.

The plates 268 are held in position in the arc chute by the insulating cross bar 263 (Figures 3-5) carried in the slot 264 of the end pieces 261. Insulating cross bar 263 is securely fastened by bolts 265, 266 respectively, at the front and back end pieces 261 of the arc chute assembly 51 which extend up above the side plates 251.

The side plates 251 are connected together at the front and back end of the arc chute by bolts 268 which connect them to the front and back strips 261. The side plates are provided with insulating bracing bars 58 secured thereto by the bolts 268 and spaced apart by the width of the laminated blow-out iron legs 55.

The materials used in the construction of the arc chute play an extremely important part in the performance of the circuit breaker.

The side plates 251 are made of Bakelite with a layer of fibre on each side. During interruption not only full voltage is applied to these plates, but frequently switching surges of very high value. are encountered. The high insulating value of Bakelite is desired but it alone would not be satisfactory since it has the characteristic of carbonizing and tracking if any arc or high temperature are gases come in contact with it.-.

Consequently, the Bakelite is coated with fibre which does not have this characteristic. Furthermore, an arc-resisting insulating varnish is applied to the fibre to keep it from absorbing moisture. Furthermore, the spacers 26l for the crossplates 260 completely line the inside of the arc chute in the lower part where the arc is drawn and prevents the are coming in contact with the side plates at any point.

The material of which the cross plates 260 and the spacers 26! are made, determines to a large extent the ability of the breaker to interrupt currents. The least expensive material that is at all suiable for this application is the asbestos cement board called Transite. This material gives fair operation and for low interrupting capacities is quite suitable. In an effort to increase the interrupting capacity, numerous materials were tried. Gas forming materials such as fibre were found to be unsatisfactory as they increased the display incident to circuit interruptions and the excess gas had a tendency to initiate arcing in other parts of the breaker.

Inert materials 7:} are on the were better. Porcelain, while quite good was too fragile and could not be manufactured in thin plates with suflicient accuracy to make it practical.

By far the best material found was the glass bonded mica consisting of mica dust and glass fused and pressed at high temperature and pressure. It is inert at the temperatures encountered in the arc chute, an excellent insulator, does not absorb moisture and is a non-gas-forming material. This material when used for the are plate and spacers increased the interrupting capacity to more than twice the value shown by other materials. It is used not only for the cross plates 260 and spacers 26! but also for the arc resisting plates 269 that come in contact with the arc.

The arc chute may be mounted in position by being slid on to the laminated blow-out iron legs so that the reinforcing bars 58, 58 act as runners to receive the laminated legs 55 in the manner shown especially in Figure 1, thus holding the arc chute in position.

In order to ensure a further distribution of magnetic blow-out flux down into the region of the contacts, an additional iron plate 210 (Figure 1) is provided on each side of the arc chute secured to the bracing bars 58 by screws 21l and having extension 212 extending down into the re ion of the contacts outside the plates 51.

The blow-out flux through the laminated blow-out iron legs 55 is also communicated to plate 210 and by extension 212 is communicated down into the region of the contacts to increase the blow out effect in that region. The runners or bracing bars 58' on one side of the arc chute are provided with the bronze springs 280 connected as shown in Figure 5 between the runners or bracing bars 58 by screws 281 and a latch assembly 6| secured thereto in any suitable manner as by the screws 283, 283 (Figures 3 and 4) and having a projection 282 which engages a corresponding detent 284 in the laminated iron leg 55 (Figure 1). Thus the arc chute is supported by the laminated legs 55 between runners 58 on each side and is latched in position by the latch assembly 6| engaging detent 284 in laminated legs 55. To remove the arc chute it is only necessary to press in the latch assembly 6| to disengage the detent 284 from laminated iron legs 55 so that the arc chute may he slid out. As already stated, the arc chute is provided with a back are runner 290 and a front are runner 29l converging below the arc chute and toward the center in the region of the contacts, the front are runner 29l having extension 29! toward the contact and the rear arc runner 298 having extension 290A toward the contacts and the further rearward extension 293.

The portion l1lA (Figure 2) of the upper terminal to which lead 238 of the blow out coil is connected is also provided with the spring clip 300 (Figures 1 and 2) to receive the rearward extension 283 of the rear arc horn 290 of the arc chute 51. Thus no special connection need be made for the arc chute; but when the arc chute is slid into position, the rear extension 293 of the rear arc horn 290 moves into the spring clip 30!! and the rear arc horn is thus connected to the end 238 of blow out coil 54.

The section 2903 of the rear arc horn rests on plate Hi to obtain further contact to the rear are horn 290. Thus when the section of the stationary arcing contact jumps to section 290A 'ofxtherrear arc horn, theicurrent pathii's fromiterminalifll, :bolt;236 to lead-235 to coil 54. to lead 238 tossection; IHA" of member IP'H andspringclip 300.. 1 Then from spring clip 300 to sectionizsllb ofvrear arcr horn 2.8!). Then through lithe are: chute to? the movablev rarcing contact andethenrtofthe:front arcrunner 29i as hereinafter morei specifically described.

The cross plates-.260. asshown particularly in Figure 4 are each of an insulating non-carbonizing m'aterialr preferabl'3 a glassbonded mica ceramic material ,or 'aof a":- materiali-known as Transita These plates are longitudinal membersas' shown in Figures 4 and 5,, having a" curve at section 3830f a very large radius; upward'of this position they have a curve 304 ofsmaller rajdius";"and above that position have an extension 305 entering the notch 26s and closing off that side of the plate, r 1

llThei'side of each plate opposite the. curve-is flatl- When the arc is firstdrawn it is driven upby the blowout mechanism "into the notch 3l0 of v' shape'd cross section formed 'bythe curves 303-494 of the alternately arranged plates. As the arc is driven up further beyond the apex of the notch, it is caused to zigzag laterally in flowing past the curves 304 of the alternately arranged plates. It thus passes through the relatively narrow notch on one side of one plate and then through a similar relatively very narrow notch on the opposite side of the alternate plate and back and forth laterally through the arc chute.

If the arc is not extinguished when the arc has reached this point, the magnetic blow out blows the are up still further past extension 395 where in addition to the lateral zigzagging and lengthening of the arc, the arc is zigzagged vertically. This combination of extreme lateral zigzagging with vertical zigzagging of the arc ensures extinguishment of the arc before the top of the arc chute is reached. The combination of lateral zigzagging with vertical zigzagging limits the upward travel of the arc.

Thus it will be seen that one of the essential elements of the arc chute herein described is first the lateral zigzagging or lengthening of the are as it is blown up into alternating thin narrow slots on each side. Thereafter the portion of the arc between the cross-plates 260 is free to move up to superimpose on the lateral zigzagging or lengthening of the arc, a vertical zigzagging or lengthening.

Also it will be seen that there is no connection whatever between the front are horn 29l and the lower terminal or any other terminal when the circuit breaker is closed or open.

It will be noted that extension 212 of the iron plate 21!] (Figures 3 and 4) comes down on each side of the arc chute adjacent to the arcs between I'HB and 208 and also between I'HB and IE6. This increases the flux density at this point. The effect on the are between I'HB and 208 which is horizontal is to drive it rapidly up the runners 290, '29l and into the arc chute 51. The effect on the are between I'HB and IE6, which is vertical, is to drive it back against the insulating and heat resisting block I58. This insulating block may be provided with slots, grooves, holes I63 or other cooling means to deionize the arc and efiect the blow-out characteristics of the breaker. It will be apparent that the size, shape and spacing of the extensions 212 will also effect the blow-out characterist cs.

It will also be noted that the conductive bar l. this o i s'v u" t ....,l I a? LH-rhas a, .u 'I'nQt i, dicated e nera1 xtJIiB therein; in; which.-the upper arcing horn- 2 01 registers,- thus provided for; simplified trans: ference..of.-the-,arc,gto the contact bar- UL. and hence tosection 29lla of the rear arc runner 290;;oi.the:arc chute ,5

, On -=funther; opening of the. contacts;-. the arc is.-b1own@up:into: the arczchute, the current path including contact .bar-,,3,0 .throug-h bolt 23 6 .an,d lead-$2,315 :through the blow-out coil, 54 ,and then throushrrspri g clip 390 a du n bana t0. 1' the; :arc: runner 1; 290. The are then passes throughcthe arc chute to; the front. are runner 28:|i,;t.then 1to,thei-arcing-horn201 on the movable arcing contact :and ,down through the moving contactstructure 8.0 ,to-t'he lower terminal- 3|.

-:..It. will be ;seen"-thatrthe gap, between the.,arc ingz horn .-20| and section -29lB-of the. front are a; runnerissmall enou zhytorpermit transfer ofthe arct'toithefmnt ardrunner as; the contact moves past."ittrgdultinggopening; The q arc shou1d .b.e blown out abDut-Cthegtime the open position i reachedzor'very:"shortl rthereafter.- :sNormally the arc where the-shortcircuitpurrent is large will be extinguished as the movable contact toward open position. In the event of an opening of the circuit breaker with relatively low currents where there is relatively very low blow-out flux, then the arc may continue to be drawn until the movable contact reaches the open positions, the are extending from section 29|B of arc runner 29l below this are runner to arcing horn 201 on the moving arcing contact 204 and there the arc is cooled and blown out through the auxiliary arc chute 320 (Figure 4) comprising the insulating side plates 269 carrying between them the spaced insulating plates 322 which are spaced by washers 323 on bolts 324 which secure the plates 322 in position and also secure the entire auxiliary arc chute 320 between the main side plates 25! of the arc chute 51.

It will thus be seen that on opening of the circuit breaker under relatively high overcurrent conditions, the arc is blown up and blown even high and extinguished. In opening the circuit breaker on relativel low currents, a longer arcing path is relied upon, the double are being drawn where the upper section of the arc is extinguished by the cooling plates already described in the main arc chute, and the lower section of the are is extinguished by the auxiliary arc chute 320.

The insulating shield 230 above described in connection with Figure 2 prevents a low current are from being blown down accidentall contacting the terminal 3|. Oscillograph tests have shown the rates of arc extinguishment ranging from .58 cycle at 63,200 kva. (4200 volts) to 2.5 cycles at 3728 kva. (5000 volts).

The arcing time may be even slower at lower voltage and curent values, but these values illustrate the efficiency of our novel device.

Since many variations and modifications of our invention should now be obvious to those skilled in the art, we prefer to be bound not by the specific disclosure herein contained, but only by the appended claims.

We claim:

1. In a circuit breaker having contacts, an arc chute comprising a plurality of plates, a blowout coil, a blow-out iron circuit comprising a core for said blow-out coil, and laminated iron plates connected to said core and extending at right angles to said core, said blow-out iron circult being so arranged that the flux induced therein when current flows in said coil is substantially evenly distributed over all of the said plate area for making maximum use of said are chute, and auxiliary blow-out iron plates mechanically and magnetically attached to said laminated plates and extending at right angles to said plates toward said contacts on each side of said are chute for diverting a portion of the ablow-out field into the vicinity of the contacts, said blow-out structure and are chute structure being mechanically separate and independent of each other, said are chute being removable independent of said blow-out structure, said blow-out structure acting as a support for said arc chute.

2. In a circuit breaker having an arc chute comprising a plurality of plates, a blow-out coil, a blow-out iron circuit comprising a core for said blow-out coil, and laminated iron plates connected to said core and extending at right angles to said core, said blow-out iron circuit being so arranged that the flux induced therein when current flows in said coil is substantially evenly distributed over all of the said plate area for making maximum use of said arc chute, and

auxiliary blow-out iron plates mechanically and magnetically attached to said laminated plates and extending at right angles to said plates toward said contacts on each side of said are chute for diverting a portion of the blow-out field into the vicinity of the contacts, said blow-out structure and are chute structure being mechanically separate and independent of each other.

JOSEPH D. WOOD. ARTHUR S. CASWELL.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,155,626 Steen Oct. 5, 1915 1,164,257 Carichofi Dec. 14, 1915 1,313,176 Evans Aug, 12, 1919 1,590,402 Aalborg June 29, 1926 1,603,820 Wade Oct. 19, 1926 2,147,430 Ellis et a1 Feb. 14, 1939 2,240,654 Jochem et a1 May 6, 1941 2,255,886 Hudson Sept. 16, 1941 2,378,124 Bolsterli June 12, 1945

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