US2646481A - High-voltage circuit breaker - Google Patents

Description

u y 53 J. D. woon arm, 2,646,481

HIGH-VOLTAGE CIRCUIT BREAKER Original Filed Jan. 11, 1947 5 Sheets-Sheet l 25? a a; g

n o I Q 140% 52 69 H 10v Q 42 34 0 19 a o 74 0 0 11 4 D Q T2 23 Q INVENTORJ F. 1 Joseph D. Wood July 21 1953., J. D. WOOD ETAL 2,646,431

HIGH-VOLTAGE CIRCUIT BREAKER Original Filed. Jab. 11, 1947 5 Sheets-Sheet 2 F101 .2 INVENTORS J) fi seph Wood BY Amawps, Caswefl u y 2 ,1953 J. D. wow E 2;64 6,4s1

HIGH-VOLTAGE CIRCUIT BREAKER Original Filed Jan. 1-1, 1947 5 Sheeis-Sheet 4 267 I fm few 44,? "24 5 257 F1 7 a I E 268 3 F196 2 260 -REFRACTORY 68 573 BAKELITE 2 70 3 REFRAC- TORY 24,0

BAKE LITE 4 INVENTORJ 257 Jose )9 D.Wood

, 3 5 BY Avthgr 5.25m

m ttohneys Patented July 21, 1953 HIGH-VOLTAGE CIRCUIT BREAKER Joseph D. Wood, Upper Darby, and Arthur S. Caswell, Philadelphia, Pa., assignors to LT. E. Circuit Breaker Company, Philadelphia; Pa., a corporation of Pennsylvania Original application January 11, 1947, Serial No.

721,648, new Patent No. 2,613,299, dated Octoher 7, 1952. Divided and this application May 7, 1947, Serial No. 746,554

6 Claims.

Our present invention which is a division of United States application Serial Number 721,648, filed January 11, 1947, now Patent No. 2,613,299, dated October 7, 1952, relates to high voltage 2. entirely disconnected from the back terminal in 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 high capacity circuit breakers, and more par- 5 are to the front are runner solely by reasonof its ticularly to circuit breakers having an interrupt proximity thereto during a portion of the opening rating of 50,000 kva. and better in any voltage ing movement; the arcing contact at the comrange between 2300 and 5000 volts and at current pletion of the opening movement moves sufratings of 600 and 1200 amperes. ficiently far away from the front are runner so Essentially our invention is directed to the 10 that there is no connection or likelihood of any production of high voltage high capacity air connection therebetween. This front are runner break switchgear in such a manner as to provide is entirely disconnected and the front of the arc the increased interrupting capacity required by chute member is completely safe for handling means of the simplest elements which are manueven while the circuit breaker is racked into posifactured and assembled by mass production tion. methods in the most economical way. Our novel are chute is supported andcarried In order to achieve this result, it has been entirely by our novel blow-out mechanism necessary to design our novel circuit breaker so which in turn is secured to the main panel of the that the various elements thereof may be manu- 2O circuit breaker in a readily movable manner factored in individual relatively inexpensive subhereinafter described. The blow-out mechanism assemblies which could then be assembled tothus constitutes a unit sub-assembly by itself. ,sgether into a single unitary circuit breaker by The blow-out mechanism comprises essentially a minimum number of operations. a U-shaped iron structure, the base of which is Our novel circuit breaker also by reason of its surrounded by the blow-out coil and the legs of simplicity of design and economy of operation 9 which extend out perpendicularly to the panel on lends itself to simplified and economical conwhich the circuit breaker is mounted. These legs struction, and thus overcomes one of the primary of the U-shaped iron structure carry the are objections to air-break circuit breakers of this chute; and the arc chute may be slid on to or oil rating. these legs for placement or removal. 7

In a high voltage high capacity breaker the 39 Outstanding features of our novel circuit first and most important step involved is the breaker include: construction of the arc chute and of the are 1. The simplicity of construction in the vicinity blow-out mechanism so that any are which is of the contact. Bearings and other cooperating drawn between the contacts as they open may be parts required for proper contact pressure are .readily extinguished before damage to the located at or near the contact pivot point. This breaker or to the circuit may occur. reduces the momentum of the moving parts re- Our novel circuit breaker includes a simple sulting in faster opening and lighter duty on the unitary arc chute structure made as a single unit bumper. These parts are also less exposed to provided with a disconnect and so arranged that make possible the construction of a narrower arc it may readily be mounted on the circuit breaker o chute; p and connected thereto or removed therefrom as 2. Reduction in the difference of impedance a whole without the necessity for special tools. between the main and are contact current paths Our novel are chute thus combines the essensufiiciently eliminated the necessity for a shunt tial ideas of simplified construction for greater contact. The arcing contact alone affords a economy and simplified arrangement in the form 45 maximum of protection for the main contact. of a single unit assembly which may readily be 3. Our novel device makes possible the commounted on any circuit breaker of the class to plete elimination of pigtails with all of the which the arc chute is to be applied. The are attendant'difliculties involved in the construcchute may readily be removed for inspection of tion, operation and maintenance of pigtails. the contacts of the circuit breaker or forreplace- 5o 4. Our novel construction also permits the ment or repair of any part that may require such elimination of a return current loop required to replacement or repair. I produce a blow-on arc contact. This current loop 'An important object of our invention, therewould not only increase-the impedance between fore, is the novel arrangement of the arc chute the arcing and main contacts but tends to blow so that the front an; runne or arcing horn is 55 ionized gas down to the mains makin possible a restrike to the mains. A small insulation barrier has been used to prevent just this condition on some breaker designs. Our novel device makes such an insulation barrier unnecessary.

As above pointed out, the blow-out iron circuit is made up of a core around which the blowout coil is wound; to the ends of the core are attached the side plates which project forward nearly the entire depth of the arc chute. These plates also act as slidesor runners and supports for the arc chute and the complete assembly is thus supported directly on the back panel support.

Heretofore in the construction of blow-out mechanisms, it has been found that a concentration of fiuX at the coil end occurs with solid side plates so that only the coil end of the arc chute is used.

Accordingly another object of our invention is the novel arrangement of the blow-out iron in such a manner that the flux is relatively evenly distributed over all of the side plate area so that the entire arc chute is used.

In addition, and in order to enhance the blowout effect, auxiliary blow-out iron plates are attached to the runner strip on each side of the arc chute and divert part of the main blow out field down into the vicinity of the contact.

By this novel construction the blow-out struc 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 for inspection and so that the blow-out construction acts as a support for the arc chute.

In actual practice, the commercial circuit breaker hereinafter described, which was d signed 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.

In addition, in high capacity circuit breakers which are designed to interrupt arcs of substantial kva., it frequently occurs that the blowout mechanism will effectively move the are 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 wing to the fact that the flux through the blowout 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 pullers and the like to assist the blow-out coil in performing its operation. Alternatively the prior art blow-out coil has been provided with suflicient 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 ineffective 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 are 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 ach eve in P 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 l is a side view in perspective, partly broken away showing our novel circuit breaker assembled and mounted on a truck.

Figure 2 is a side, back view, in perspective, showing our novel circuit breaker mounted on a truck with the interphase barrier in position.

Figure 3 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 4 is a detail of the construction of the front end of lower terminal of our novel circuit breaker.

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

Figure 6 is a front view of the arc chute assembly.

Figure 7 is a top view of the arc chute assembly.

Figures 8 and 9 are schematic views illustrating successive steps in assembling our novel circuit breaker.

Referring now to Figures 1, 2 and 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 H3 and H connected together and interbraced at the lower end by the Masonite panel 12 and at the central and upper portion by the cross-bars 23, id and [5 which are connected as shown, in any appropriate manner, as for instance by bolts and nuts to the vertical members and H. The lower ends of the vertical members and H are provided with bearings ll and 8 for the shaft 19 which carries the rear wheels 20 and 2| of the truck. The vertical members It and II together with the cross bracing elements above described and the wheels and El constitute a single unitary member of assembly.

Certain of the assemblies are standard and require no specific discussion here. Thus, the control panel assembly i! and the trip unit as sembly 43 may be substantially standard units which require no specific description. Also, the control switch contacts indicated generally at it of Figures 1 and 2 and the grounding contacts 1!, i2 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 me hanism assembly 46 is supported on the cross bar "M 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 Figures 1 and 2 and forming an essential part of the novel circuit breaker here shown are the operating mechanism shown in Figure 1, the lower terminal assembly shown in Figure 4, the upper terminal assembly of Figure 3, the movable contact arm or bridge assembly of Figure 3, the blow out assembly of Figure 3, and the arc chute assembly of Figures 5, 6 and '7. The specific operation of these individual assemblies renders possible the entirehigh speed high capacity circuit breaker which our novel unit embodies.

The various assemblies above'rnenti'oned will be described in order, going from the bottom toward 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 important feature of the circuit breaker is in the novel 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 operated switch with only enough addition thereto to provide automatic response to over-current conditions inorder 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 essential to the operation of the circuit breaker as a whole, the simplicity of the other assemblies makes possible the economical and efiicient 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 paneland the back wheels 2% and 2! is essentially a simple flat member which may readily bestored and does not take up any substantial amount of space (see also Figures 1 and 2).

Heretofore, the difiiculty encountered in premanufacture of sub-assemblies i anticipation of future orders resided in the fact that the main frame of the circuit breaker or other switch 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 pre-manufacture of the main frame since 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 which constitutes a single fiat structure may readily be stored awaiting specific orders for assembly of specific circuit breakers.

The truck structure is completed by means of a lower or bottom platform 23, which carries a front wheel 24 in the front'swivel 25 (Figures 1 and 2). The bottom platform 23 is secured at the rear end to the lower end of the vertical members Iii and i! abov the bearings l1 and 18 for the rear wheel. The bottomv platform 23 in connection with the back panel form the vertical supporting members it and It and their interbracing structure and taken together with the rear wheels 26 and 21 and the front swivel wheel 24 comprises the truck or mounting for the circuit 24 constituting a single sub-assembly which may readily be stored without requiring any additional space and which may readily be attached by two screws to the lower end of the vertical members l0 and II.

This type of unitary sub-assembly construction which may readily be interconnected with other elements in order to make a complete truck, facilitates modification and of variation of subassemblies 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 23, this lower platform '23 may be built to the unique specifications of the customer and may then be combined with the standard back panel construction which is kept in stock. However, the'enti're stockconstruction including the first and second subassemblies above described are built in full anticipation of all requirements to which the particular circuit breaker'inay be put, so that particular custom made back or bottom portions of a truck will be required only in exceptional cases. The upper terminal assembly 39, and the lower terminal assembly 3! for each of the three poles is formed from a single bar of copper of rectangular cross section appropriately insulated by phenolic insulation as described more specifically hereinafter in connection with Figure 3. The terminal assembly elements 3%; 3! are carried by the vertical supports I s and H, as well as the central vertical support 32 which is carried between the lower Masonite plate 12, and the upper cross bar Hi, as shown in Figure 2.

Each of the vertical members [9, H and 32 is recessed at 33, 23 to receive the terminal members and accurately position the same. Each of the terminal members is provided with a side plate or flange 35. hereinafter more specifically described in connection with Figure 2.

Each of the vertical reinforcements H), H and 32 the recesses are cut out in the vertical reinforcement they are incisedonly in the portion of the rectangular steel member which is normal to the back panel 56. The legs of each of the rectangular members Hi, i I and 32 carry the bolts 3&3, 35 which engage the flange members 35 of the terminal element. Thus it will be seen that two belts or screws 35 are all that are necessary to secure each of the terminal elements in place, these bolts being locked in secured position by the nut 31 as shown in Figure 2.

Each of the upper and lower terminal assemly members and BI also carry the spring biased disconnect contact elements 38 also hereinafter more specifically describedin connection with Figures 1 and 2, but shown also in Patent Number 2,029,028. The intermediate cross bar 13, which is secured to thevertical members Hi, I! and 32 by the bolts .8, also carries at its outer end the wheels 32 on an appropriate shaft extension thereof, the said wheels 52 cooperating with appropriate tracks in the compartment to guide the truck into and out of the compartment properly. a

The racking and indicator assembly shown generally at E3 of Figures 1 and 2 also carries the front wheels Mi, ts to ride on the guide tracks of the compartment in which the circuit breaker is housed.

The movable contact assembly shown generally at of Figures 1 and 3 is connected at its lower end. to the lower terminal assembly it in the manner hereinafter described, and is provided with a link 5! which is connected to the contact operating arms 52 projecting up from theoperating mechanism assembly 2 6. The movable contact bridge assembly which of course has as many poles as there are upper and lower terminal assemblies, three in the particular instance shown, is provided with contact elements hereinafter more particularly described in connection with Figure 3.

blow out iron legs 55, is mounted on the upper is a rectangular steel member, so' that while The biow out coil assembly 53 which includes the coil 5 3 of Figure 3 and the laminated insulating back panel 56 also across the bars I5 and I4 and the upper portion of vertical supporting members I and I I and. is supported thereby.

It is spaced from the bars I0, II, 32, I l, I5 by the upper insulating back panel 55 which panel is secured across the bars I0, I I and 32 as shown in Figures 2 and 3. Appropriate openings 59, 59 are provided in the panel 55 to permit the terminal members 35 and SI to project therethrough in a manner shown in Figures 1 and 3.

The arc chute assembly 51 is supported by the blow out assembly 53 and particularly by the laminated legs 55 of the blow out iron which ride between the bracing bars 58, 53 on each side of the arc chute as shown in Figures 1 and 5, and as will be more specifically described hereinafter in connection with Figures 1, 4 and 5.

All of the elements of the circuit breaker as will be seen from an inspection of Figures 1 and 2, and of subsequent figures may be inexpensively made from ordinary sheet metal or cut from ordinary bars, and no complicated casting or machining operation is required, thus leading to great economy in the manufacture and assembly of the device.

Also from the previous discussion it will be seen that the assembly operation consists of a number of units as above described, each of which may readily be stocked and kept in storage without consuming an undue amount of space and which may readily be assembled simply by a few bolt or screw manipulating operations to interconnect an entire circuit breaker from the unit assemblies.

The operating mechanism shown in the perspective front view of Figure 3 in the parent application Serial Number 721,648, filed January 11, 1947, now Patent No. 2,613,299, dated October 7, 1952, comprises essentially a simple switch operating mechanism with the addition of the necessary trip unit trip-free operation and solenoid closing mechanism necessary for automatic circuit breaker operation.

Lower terminal assembly The lower terminal assembly 3| shown in Figures 1, 2 and 3, comprises a bar of copper I insulated by an oblong Bakelite tube I5l 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 I54.

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 3. In the usual procedure for insulating a terminal bar such as that shown in Figures 1, 2 and 3, 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 fiat tube I5I is used, said tube being provided with a conductive lining I 62. 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 deterioration and thereby resulting in breakdown of the insulation. Consequently great care was required in the wrapping of the insulation.

Upper terminal assembly The upper terminal assembly 30 shown in Figures 1, 2 and 3 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 3.

The rear end of the bar I60 has the conformation I64 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 I56 (Figure 3). The upper end of the front portion of bar I60 has secured thereto the insulating blocks I65 and IE8 (Figures 1 and 3), which have secured thereto the insulating plate I'I0 having the upper slotted extension I'IOA. Connector III is secured in any suitable manner to the insulating blocks I65 and I68 but is insulated from the contact bar I50 and the arcing contact I60 and stationary contact I 07.

Connector III has a slotted or cut away portion I19 at its front end between which, and spaced from either edge, the forward end 208 of the movable contact arm 204 comes to rest when the contacts are in engagement as will be described hereafter.

Movable contact assembly In Figure 3, we have shown one of the contact 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 contactarm 204 is held in proper spaced relation by the spacer washers I84I84, all of which are forced into proper current carrying relation by the spring washers 233233. The upper inside edge of the copper bars I80I8I carry special are resisting silver alloy contact blocks I85 which comprise the main movable contacts.

The lower ends of the bars I80 and I BI are provided with the registering openings to receive the pin I8! (Figures 1 and 3) which pin passes through the openings and through the slotted openings I88 (Figure 4) of the front end I52 of the lower terminal 3| which is received between the arms I80I8I.

The pin I8! is provided on each side with a lug I90 (Figures 1, 3 and 4) carrying the bar I9! which passes through openings I93A (Figures 3 and 4) of the side flanges I56. Compression springs I93 on each side are captured between flanges I55 on each side and the lug I90 of pin III! on each side thus forcing the lower end or pivot of the contact arm out toward the right wish respect to Figures 1 and 3 at the pivot point 20 The contact arm effectively pivots about pin 200 (Figures 1 and 3) which is connected be tween the arms I8I and I80 and which carries the end of link 5I connected to contact operating arm 52. Thus, compression springs I03 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 IB'I (Figures 1 and 3).

In any position of the arm 80 other than the 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 per mit the wiping action to occur between the contacts I 85 and I6! and the contacts to close firmly. The forward end I52 of the lower terminal of Figure 4is 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 used, but appropriate elements are used on pin I81 to squeeze the lower ends of arms I8I, I80 against the insert contacts 2I'I2 on the lower terminal. I The contact springs I93 are located close to the pivoted stud I31 which is a distinctadvantage because they are well away from arcing zone. The connection of link 5! to the contact arms is at a point 2%, 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 response to arise in currents, magnetic forces developed in these contacts tend to increase contact pressure at all contact points. The areing contact arm 204 is pivotally mounted on the pin 205 between the contact arms I89, I8l and the spacer washers I84, and is provided with an arcing contact element 206 and the horn 297.

The lower end of arcing contact arm 234 is connected by the floating pin 2I0 to the link 2! I which in turn at this lower end bears against the milled surface 2I2 of the milled pin .2I3 carried between the arms I80, I8 I.

Tension spring Elli connected between lug 2H5 and spring eye 2H is arranged to rotate link ii I clockwise around the bearing furnished by the milled portion BIZ of pin M3; The lug 255 is adjustably mounted on screw 226 which in turn is received in the tapped opening 22! of pin 222 carried between the arms see, ISL. Rotation of screw 225% results in moving lug2 It; to change the tension of spring ZI5 and thus increase the bias thereof.

Spring 5H5 thus acts on links 2H to cause the toggle 2II2Iii-2fi4 to' collapse in a direction to force the arcing contact 2 36 to the left. The full collapse of this toggle is prevented by the adjustment of screw 228 which bears against the end 225 of arcing contact arm 2M. Tension spring 2I5; however, thus drives the arcing contact element 2% out to the left with respect to Figure 3 where it will make contact with the stationary arcing contact I as before the main contacts engage and where it will maintain contact'with the stationary arcing contact'until after the main con-' tacts have been made.

Since the center 295 of arcing contact arm 23s is well above the mid-point thereof, a blow-on action of the arcing contact occurs, also thus ensuring that the arcing contacts will remain firmly in engagement until the main contacts have separated.

The position of the arcing tips 2% above the main contacts I Si forms an upward loop in the circuit which tends to initiate a blow-out action to start the are upward when drawn.

In order to protect the lower terminal structure against any possible defect in the arc chute 10 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 cut to protect the uninsulated portion of the lower terminal bar I50,

Spring 255 ensures that the movabie 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 engagement for a substantial portion of the opening movement depending on the setting of screw 2% (Figure 3).

Blow out assembly bicw-out assembly 53 comprising the coil 5t and the laminated blow-out iron legs 55 already referred to in Figures 1 and 2, is shown more specifically in Figure 3. The coil 54 is connected by the lead 235 and bolt 2% (Figures 1 and 3) to the upper terminal bar Hit. The opposite end of coil 54 is connected by lead 238 to extension I MA on contact bar I II passing through a slot in the upper extension I'IDA of insulating strip I'iii (Figure 3). Coil 5% is wound on an iron core 250 to which is secured the laminated blow-out iron legs 55 on either side.

The side frame members 242, 242 (Figure 3) of the blow-out assembly are secured against the core 24d by bolts 243 which also secure the plates 55 against the core. 282 of the blow-out assembly have secured therebetween the upper block 245 by means of pin and the lower block (not shown) by means of pin 2&3 and plate 249 by means of screws 258.

Blocks 245 and its corresponding lower block are provided with tapped openings by means of which the entire blow-out assembly may be readily'secured to the frame of the circuit breaker. It will thus be seen that the entire blow-out assembly may be readily mounted on and removed from the circuit breaker as a single unit.

Arc chute The blow-out assembly serves as support for the arc chute described inFigures 3, 5, 6, and 7. The arc chute assembly 51 mounted above the contact assembly 88 provides for a positive and efficient arc interruption. It consists of insulation side walls 257, front and back are runners 29I and 2% respectively and a series of ceramic plates 260 mounted in spaced relation transverse of the arc path and a strong magnetic blow-out field to force the are into the arc chute.

The sides 251 (Figures 5 and?) have fastened at their lower portion, adjacent the arcing area, innerarc resisting insulating plates 269-4269 of special composition hereinafter described. The are resisting plates 2-59 are charnfered along their "upper edges at 262-262 to provide a straight locking edge for the cross plates 269" and the spacers'ZGI. The lower ends of the cross plates 26d and the spacers 2ti'are appropriately shaped to fit the chamfered edge 262.

As the arc is driven into the chute by the magnetic field, it passes rapidly through the arc' extinguishing ceramic plates 265 which are rectangular in shape at thetop and have a long tapered lower edge extending from the center of one side of the plate to the lower corner on the opposite side of the plate. A ceramic spacer 25! is provided to support each plate and position it with respect to adjacent plates and forms with the longtapered surface of the plate a triangular opening with the apex at thetop for The side frame members 11 the passage of the arc. Each plate with its spacer presents a decreasing area for the arc as it rises and gradually squeezes it into a narrow slot 36?.

The plates 2% are assembled alternately an interleaved relation and spaced from each other so that the long tapered surfaces cross at the center of the chute directly above the path of the arc as it travels up the chute. As the arc passes the cross-over point of the plates it is forced into a zigzag or sinuous path gradually but rapidly increasing its length and bringing it into contact with the larger and larger cool surfaces of the plates. he arc must thus bend around the edges of the plates which are effective in circuit interruption. The positive and efficient arc interruption is affected by the cooling, lengthening and squeezing of the are at numerous points all along its path.

Provision for the interruption of low current arcs is built into the arc chute. No moving parts or auxiliary equipment are necessary. Short circuit or normal overcurrents are extinguished before the moving arc horn passes the front are runner 253i. The are formed by currents of low value is extended in the chute beyond the front arc runner EM and effectively cooled and deionized by a set of plates 322 (Figure 6) located in the current path.

Arc travel toward the front of the chute involves a transfer from the arc contact arm to the forward arc runner. The absence of the return connection from this runner to the lower 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 29l continues as long as the re exists. On high values of current the arc is extinguished before the arc contact arm 284 passes the runner 29!.

Progress of the arc up into the chute brings it in contact with the cross plates 250 which are shaped and assembled so as to cause the arc to follow a gradually increasing zigzag 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 3E1. The length of the plates 269 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 arc is extended by the long travel of the arcing tips and cooled by the specially located plates 322 below the front arcing horn 291.

The plates 266 are held in position in the arc chute by the insulating cross-bar 283 (Figures 5-7) carried in the slot 264 of the end pieces 29?. Insulating cross-bar 253 is securely fastened by bolts 265, 26% respectively, at the front and back end pieces 26? of the arc chute assembly 5? which extend up above the side plates 251.

The side plates 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 12 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 25'! 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 are 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 26! for the cross-plates 2G0 completely line the inside of the are coming in contact with the side plates at any point.

The material of which the cross plates 26!) 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 suitable 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 t 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 were better. Porcelain, while quite good was too fragile and could not be manufactured in thin plates with sufiici nt accuracy t 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 nongas-forming material. This material when used for the arc 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 26D and spacers 26I but also for the arc resisting plates 269 that come in contact with the arc.

The are chute may be mounted in position by being slid On to the laminated blow-out iron legs 55 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 27! and having extension TF2 extending down into the region of the contacts outside the plates 51.

The blow-out flux through the laminated blow-out iron legs 55 is also communicated to plate 216 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 i 13 runners or bracing bars 58 by screws 28I and a latch assembly 6| secured thereto in any suitable manner as by the screws 283, 283 (Figures 5 and 6) and having a projection 282 which engages a corresponding detent 284 in the lamihated iron leg -55 (Figure l). Thus the arc chute is supported by the laminated legs 55 between runners 583 on each side and is latched in position by the latch assembly 8! engaging detent EM in laminated legs 55. To remove the arc chute it is only necessary to press in the latch assembly SI to disengage the detent 23:1 from laminated iron legs 55 so that the arc chute may be slid out. As already stated, the arc chute is provided with a back arc runner 296 and a front arc runner 29I converging below the arc chute and toward the center in the region of the contacts, the front are runner 2I having extension EQIB toward the contact and the rear arc runner 296 having extension 290A toward the contacts and the further rearward extension 293.

The portion IIIA (Figure 3) of the upper terminal to which lead 238 of the blow-out coil is connected is also provided with the spring clip tilt (Figures 1 and 3) to receive the rearward extension 2% of the rear arc horn 29d of the arc chute 57. Thus no special connection need be made for the arc chute; but when the arc chute isslid into position, the rear extension 293 of the rear arc horn 296 moves into the spring clip 36%} and the rear arc horn is thus connected to the end 233 of blow-out coil 5 The section 29613 of the rear arc horn rests on plate ill to obtain further contact to the rear arc horn 296. Thus when the section of the arc on the stationary arcing contact jumps to section 296A of the rear arc horn, the current path is from terminal 36, bolt 236 to lead 235 to coil 54 to lead 2-38 to section I'IEA of member HI and r spring clip 3%. Then from spring clip 360 to section 29-38 of rear arc horn 290. Then through the arc chute to the movable arcing contact, and then to the front are runner ZQI as hereinafter more specifically described.

The cross plates 266 as shown particularly in Figured are each of an insulating non-carbonizing material, preferably a glass bonded, mica ceramic material or of a material known as Transite. These plates are longitudinal mem hers as shown in Figures 6 and '7 having a curve at section 3533 of a very large radius; upward or" this position they have a curve 364 of smaller radius; and above that position have an extension entering the notch 26!] and closing off that side of the plate.

The side of each plate opposite the curve is flat. When the arc is first drawn it is driven up by the blow cut mechanism into the notch 3H3 of V- shaped cross-section formed by the curves- 363-386 of the alternately arranged plates. As the arc is driven up further beyond the apex of the notch, it is caused to zigzag laterallyin flowing past the curves 3% of the alternately arranged plates. It thus passes through the relatively narrow notch Sill 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 arc up still further past extension 305 where in addition to the lateral zigzagging and lengthening of the arc, the arc is zigzag-god vertically.

Janie rel 14 This combination of extreme lateral zigzagging with vertical zigzagging of the arc ensures extinguishment of the are before the top of the row slcts on each side.

are chute is reached. The combination of lateral zigzagging with vertical zigzagging limits the upward travel of the arc. 7

Thus it will be seenthat 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 nar- Thereafter the portion of the arc'between the cross-plates 26B is free to move up to superimpose on the lateral zigzagor lengthening of the arc, a vertical zig- Zagging or lengthening.

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

The advantages of the arc chute thus described will thus be obvious.

With the circuit breaker closed, the current passes from upper terminal bar 30 through the main contacts and contact arm 89 to the lower terminal bar SI. On the occurrence of overload conditions resulting in tripping of the circuit breaker, a change in current occurs in which the initial opening movement of the contact bar (it? pulls the main moving contacts apart but re,- tains the arcing contacts in engagement. so that the current path is now through the arcing contacts.

When the moving are tips 206 first separates from the stationary contact I66. an arc is drawn between contacts E66 and 206. The blow up action and the ionized gas from this are drives the arc upwardly along contact I66 in an arcuate form until an arc is established between the contact 66 and U-shaped notch I'HB and thence from the U-shaped notch I'IIB to the forward portion 268 of the arc horn 201. The are between the arcing contacts I66 and 20.6 is in parallelwith the arcs between contacts I66 to I'I'IB to 5:66. Since the impedance of the gap between I66 and 2536 is made to be less than the gap between the arcing tips I66 and 206, after the latter has moved a predetermined distance, the are between the arcingtips. I66 and 206 is immediately extinguished.

The shapes and the space between the U- shaped piece ill B and the stationary arcing tip E66 is such that the arc thereacross is struck and continues. This, arc is in parallel with the circuit through the windings, of the blow-out coiled.

The voltage drop across the blow-out coil fi lis in proportion to the current flowing in the circuit. When the breaker is opening high, short circuit currents, the voltage might be as high as 2600 volts if all the current flows through the blow-out coil This does not occur since the voltage will maintain the are between IlIB, and its. The'current in the breaker therefore divirlcs; part of it passing through the blow-out coil 5 and part of it through the are between iHB I66. The division of current in these two paths is inversely proportional to the fault current value and to the voltage drop in the blow-out coil 54, i. e.,the current flowing in the blow-put coil is of a value such that the drop in the coil equals the drop acrossthe gap in parallel. The division of the current'in the two paths is therefore different at diiferent overload current values. For instance, at low current values, most of the current will pass through the blowout coil since the voltage across the blowout coil assembly 53 is low and the are is scarcely maintained. At higher current values flowing through the circuit breaker, however, proportionately less of the current must flow in the blow out coil 54 to maintain the voltage drop across the coil equal to the voltage drop across the gap and accordingiy more current in proportion is shunted through the arc.

This is a very desirable feature since the circuit breaker must operate on all current values up to its rating. A blow-out coil can in accordance with this arrangement, be designed to be effective at low current values and still be effective at high current values without requiring it to carry the full short circuit current. The blowout coil may be made of smaller Wire, more turns and less bracing without danger of its burning out or being distorted by the high currents.

Another advantage of this are transfer method of inserting the blow-out coil is that the blowout coil 55 is not in the circuit at any time except when opening a circuit. Therefore, it is not 'equired to carry any current continuously.

Those skilled in the art will also recognize that the performance of the breaker may be varied for a wide range of current values by the design of the arc gap between E'HB and H66. The impedance of this gap determines the current flowing in the blow-out coil 5 1. By increasing or decreasing the length of this gap, its impedance is effected and the current in the blow-out coil 54 is for any short circuit current value increased or decreased. Further any deionizing effect on this are as the result, for instance, of blowing it into narrow slots 83 or against rough edges of insulating material, will increase the arc impedance and also effect the blow-out characteristics of the breaker.

It will be noted that extension 212 of the iron plate 2'26 (Figures 5 and 6) comes down on each side of the arc chute adjacent to the arcs between Hi3 and 208 and also between [HE and USE. This increases the flux density at this point. The effect on the are between l'HB and 208 which is horizontal is to drive it rapidly up the runners 290, 29! and into the arc chute 51. The effect on the are between l'llB and I66, which is vertical, is to drive it back against the insulating and heat resisting block H58. This insulating block may be provided with slots, grooves, holes I63 or other cooling means to deionize the arc and affect the blow-out characteristics of the breaker. It will be apparent that the size, shape and spacing of the extensions 212 will also affect the blow-out characteristics.

It will also be noted that the conductive bar I?! has a U notch indicated generally at l'HB therein, in which the upper arcing horn registers, thus provided for simplified transference of the arc to the contact bar ill and hence to section 290A of the rear arc runner 290 of the arc chute 51.

The insulating shield 230 above described in connection with Figure 3 prevents a low current are from being blown down accidentally 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 current values, but these values illustrate the efficiency of our novel device.

I 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 an arc chute structure for a circuit breaker having cooperable arcing contacts, a plurality of side plates, insulating bracing bars secured thereto forming supporting slides, a blowout mechanism comprising u -shap'ed laminated iron legs, said laminated legs forming tracks on which said slides are supported, an arc chute and a latch mechanism secured to said side plates, said latch mechanism engaging a detent in said laminated iron legs for removably supporting said are chute thereon.

2. In a circuit breaker having a pair of cooperable contacts, a blow-out coil. an arc chute mounted above said contacts, said are chute being provided with a back runner and a front are runner converging below said are chute and toward the center in the region of said contacts, said front are runner having an extension toward said contacts, and the rear runner having an extension toward said contacts and electrically disconnected from said contacts at all positions thereof, and spring clips secured to said blow-out coil for receiving a rearward extension of said rear arc runner and providing a connection to said are chute and said coil to provide ready removability of said are chute from said blowout coil.

3. In a circuit breaker, a fixed contact, a back connecting stud connected to said fixed Contact, a blow-out coil, an arc chute, said blow-out coil having a disconnect contact secured to one terminal thereof, the opposite terminal of said blowout coil being electrically connected to said back connecting stud, and a conductor connected to said are chute and arranged to engage said disconnect contact when said arc chute is mounted in place on said circuit breaker, said are chute being removable from said circuit breaker, the removal of said are chute disengaging said conductor from said disconnect contact. 4. In a circuit breaker, a fixed contact, a back connecting stud connected to said fixed contact, a blow-out coil, an arc chute, said blow-out coil having a disconnect contact secured to one terminal thereof, the opposite terminal of said blowout coil being connected to said back connecting stud and a conductor connected to said are chute and arranged to engage said disconnect contact when said arc chute is mounted in place on said circuit breaker, said are chute being removable from said circuit breaker, the removal of said are chute disengaging said conductor from said disconnect contact, a movable contact for engaging said fixed contact, means responsive to fault currents for operating said movable con tact to disengage said fixed contact and an arcing horn connected to the opposite end of said are chute and arranged so as to be disengaged from said movable contact in all positions, said movable contact in its movement between its engaging positions of said first contact and its open position passing adjacent the second arcing horn for transferring an arc therefrom.

5. In a circuit breaker having a pair of cooperable contacts, an arc chute, a blow-out mechanism, said blow-out mechanism having a pair of laminated legs, said arc chute being supported on said legs, a front arc runner across the arc chute electrically disconnected from any element of said circuit breaker but brought into close proximity with said movable contact on disen- 1 7 gagement thereof, a rear arc runner; a disconnect contact carried by said blow-out mechanism, and a cooperating disconnect contact extending from said rear arc runner; said blow-out mechanism and said rear arc runner being electrically connected by said disconnect contacts.

6. In a circuit breaker having a pair of cooperating contacts, an arc chute, a blow-out mechanism having disconnects, said blow-out mechanism having a pair of laminated'legs, said are chute being supported on said legs, and a latched mechanism for removably maintaining said arc chute in the engagement with said disconnects.

JOSEPH D. WOOD. ARTHUR S. CASWELL.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,022,049 Reisbach Apr. 2, 1912 1,055,850 Von Zweigbergk Mar. 11, 1913 1,155,626 Steen Oct. 5, 1915 Number Name Date Carichoff Dec. 14, Steen Mar. 27, Baker Aug. 16, Mason June 13, Brainard et a1. June 19, Jensen et a1 1- Apr. 2, Trofimov Feb. 23, Ellis Feb. 14, Sauer Sept. 24, Jochem et a1. May 6, Hudson 1 Sept. 16, Scott, Jr Oct. 14, Nau Mar. 17, Latta Nov. 16, Powell Feb. 1, Ballou Oct. 3, Bolsterli 1 June 12, Scott Sept. 9, Dickinson May 25, Bennett Jan. 25, Wood Apr. 26, Minneci July 4,

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