US2731530A - High voltage circuit breakers - Google Patents

Description

Jan. 17, 1956 J. D. WOOD ET AL 2,731,530

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8 Sheets-Sheet 8 United States Patent 0 HIGH VOLTAGE CIRCUIT EBREAKERS Joseph D. Wood, Straiford Village, and Arthur Stephen Caswell, Philadelphia, Pa., assignors to I-T-E Circuit Breaker Company, Philadelphia, Pa.

Original application January 11, 1947, Serial No. 721,648,

now Patent No. 2,613,299, dated October 7, 1952. Divided and this application September 4, 1952, Serial No. 307,842

2 Claims. (Cl. 200-147) 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, and application Serial Number 746,554 filed May 7, 1947, now Patent No. 2,646,481, dated July 21, 1953,

relates to high voltage high capacity circuit breakers,

and more particularly to circuit breakers having an interrupting rating of 50,000 kva. and better in any voltage range between 2300 and 5000 volts and at current ratings of 600 and 1200 amperes.

Essentially our invention is directed to the production of high voltage high capacity air break switchgear in such a manner as to provide the increased interrupting capacity required by means of the simplest elements which are manufactured and assembled by mass production methods in the most economical way.

in order to achieve this result, it has been necessary to design our novel circuit breaker so that the various elements thereof may be manufactured in individual relatively inexpensive single unitary circuit breaker by a minimum number of operations.

Our novel circuit breaker also by reason of its simplicity of design and economy of operation lends itself to simplified and economical construction, and thus overcomes one of the primary objections to air-break circuit breakers of this rating.

Air circuit breakers of high kva. interrupting capacity have heretofore been very expensive in design and construction utilizing castings and welded parts and have usually been custom-built for a particular job rather than made in a particular grouping or line for particular interrupting capacities.

Our novel construction fabricated entirely from shut or bar stock into many sub-assemblies and using no castings lends itself to mass production manufacturing methods which together with simplicity in design reduce the cost of the high voltage high capacity breaker to a point where its cost compares favorably and at times is even less than many low voltage relatively low capacity circuit breakers.

In a high voltage high capacity breaker the first and most important step involved is the construction of the arc chute and of the are blow-out mechanism so that any are which is drawn between the contacts as they open may be readily extinguished before damage to the breaker or to the circuit may occur.

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

Our novel are chute thus combines the essential ideas of simplified construction for greater economy and simplified arrangement in the form of a single unit assembly which may readily be mounted on any circuit breaker of the class to which the arc chute is to be applied. The are chute may readily be removed for inspection of the 2,731,530 Patented Jan. 17, 1956 contacts of the circuit breaker or for replacement or repair of any part that may require 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 avoidance of any dielectric breakdown which may occur in the operation of the circuit breaker.

An important object of our invention, therefore, is the novel arrangement of the are chute so that the front are runner or arcing horn is 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 arc to the front arc runner solely by reason of its proximity thereto during a portion of the opening movement; the arcing contact at the completion of the opening movement moves sufliciently far away from the front are runner so that there is no connection or likelihood of any connection therebetween. This front are runner is entirely disconnected and the front of the arc chute member is completely safe for handling even whilethe circuit breaker is racked into position.

Our novel are chute is supported and carried entirely by our novel blow-out mechanism which in turn is secured to the main panel of the circuit breaker in a readily movable manner hereinafter described. The blow-out mechanism thus constitutes a unit sub-assembly by itself.

The blow-out mechanism comprises essentially a U-shaped iron structure, the base of which is surrounded by the blow-out coil and the legs of which extend out perpendicularly to the panel on which the circuit breaker is mounted. These legs of the U-shaped iron structure carry the arc chute; and the arc chute may be slid on to or on these legs for placement or removal.

The upper back connection stud and stationary contact elements constitute a single unit sub-assembly which may readily be mounted on and removed from the back panel.

The lower back connection stud and the movable contact arm with its link each constitute a single unitary subassembly which may also as above pointed out be readily mounted on and removed from the circuit breakers. Both the upper and lower back connection members have secured thereto the back disconnect contacts which are part of the same assembly.

The mechanism assembly which includes all of the operating members constitutes a single sub-assembly which may readily be mounted on the circuit breaker panel and disconnected therefrom and which may be connected to the movable contact arm by passing a single pin through the connecting link.

The other individual assemblies which may be manufactured separately and individually mounted on and removed from the circuit breaker include the racking and indicator assembly, the control panel assembly and the trip unit assembly. Other assemblies and relays may be added or removed as desired in order to complete the individual circuit breaker.

Outstanding features of our novel circuit breaker include:

1. The simplicity of construction in the vicinity of the contact. Bearings and other cooperating parts required for proper contact pressure are located at or near the contact pivot point. This reduces the momentum of the moving parts resulting in faster opening and lighter duty on the bumper. These parts are also less exposed to make possible the construction of a narrower arc chute.

2. Reduction in the difiereuce of impedance between the main and are contact current paths sufiiciently eliminated the necessity for a shunt contact. The arcing contact alone affords a maximum of protection for the main contact.

3. Our novel device makes possible the complete elimination of pigtails with all of the attendant difficulties involved in the construction, operation and maintenance of pigtails.

4. Our novel construction also permits the elimination of a return current loop required to produce a blow-on arc contact. This current loop would not only increase the impedance between the arcing and main contacts but tends to blow ionized gas down to the mains making 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 in sulation barrier unnecessary.

As above pointed out, the blow-out iron circuit is made up of a core around which the blow-out 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 slides or 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 flux 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 actual operation we have found that an economical combination of four A; inch thick plates on each side gave a fairly even ilux distribution over the full length.

In addition, and in order to enhance the blow-out 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 contacts.

By this novel construction the blow-out structure 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.

Accordingly an object of our invention is the construction of a high capacity high voltage circuit breaker, capable of interrupting arcs of 50,000 kva. capacity or even better, and economical in design and construction, capable of unit subassembly manufacturing operation; and so reduced in cost that its price may compare favorably and at times even be lower 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. in terrupting 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.

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 are 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 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 are 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 puffers and the like to assist the blow-out coil in performing its operation. Alternatively the prior art blow-out coil has been provided with sufiicient 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 blow-out mechanism of our novel circuit breaker so that it may move an are at low itnerrupting 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 achieve in part by passing only a portion of the arcing current through the blowout coils, the percentage of such current decreasing the 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 are chute assembly.

Figure 8 is a side view of the interphase barrier.

Figure 9 is a front view of the interphase barrier.

Figures 10 and ll are schematic views illustrating successive steps in assembling our novel circuit breaker.

Figure 12 is a perspective and partially exploded view of a portion of the are chute of our novel circuit breaker.

Figures 13 and 14 are schematic views of the arcing contacts and blow-out coil of our novel circuit breaker.

Referring now to Figures 1, 2 and 3, 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 10 and 11 connected together and interbraced at the lower end by the Masonite panel 12 and at the central and upper portion by the cross-bars 13, 14 and 15 which are connected as shown, in any appropriate manner, as for instance by bolts and nuts to the vertical members 10 and 11. The lower ends of the vertical members 10 and 11 are provided with bearings 17 and 18 for the shaft 19 which carries the rear wheels 20 and 21 of the truck. The vertical members 10 and 11 together with the cross bracing elements above described and the wheels 20 and 21 constitute a single unitary member of assembly.

Certain of the assemblies are standard and require no specific discussion here. Thus, the control panel assembly 47 and the trip unit assembly 48 may be substantially standard units which require no specific description. Also, the control switch contacts indicated generally at '70 of Figures 1 and 2 and the grounding contacts 71, 72 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 74 which is held by the bolts 75, 75 across the top of the lower panel 12. Cross bar 74 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 entire high speed high capacity circuit breaker which our novel unit embodies. Additional assemblies which facilitate the operation are specifically described in connection with Figures 8 and 9 which show the interphase barrier assembly.

The various assemblies above mentioned 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 overcurrent 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 essential 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 and 21 is essentially a simple fiat member which may readily be stored and does not take up any substantial amount of space (see also Figures 1 and 2).

Heretofore, the dixficulty encountered in pre-rnanufacture of sub-assemblies in 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 constitute asingle flat 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 (Figures 1 and 2). The bottom platform 23 is secured at the rear end to the lower end of the vertical members it? and 11 above the bearings 17 and 18 for the rear whee. The bottom platform 23 in connection with the back panel form the vertical supporting members 10 and ii and their interbracing structure and taken together with the rear wheels 20 and 21 and the front swivel wheel 24 comprise the truck or mounting for the circuit breaker and constitutes 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 10 and 11.

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 sub-assemblies in order to meet the specific orders. 7

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 entire truck construction including the first and second sub-assemblies above described are built in full anticipation of all requirements to which the particular circuit breaker may 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 30, and the lower terminal assembly 31 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 30, 31 are carried by the vertical supports 10 and 11, as well as the central vertical support 32 which is carried between the lower Masonite plate 12, and the upper cross bar 14, as shown in Figure 2.

Each of the vertical members 10, ii and 32 is recessed at 33, 33 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 1t), 11 and 32 is a rectangular steel member, so that while the recesses 33, 33 are cut out in the vertical reinforcement they are incised only in the portion of the rectangular steel memher which is normal to the back panel 5&5. The legs of each of the rectangular members it), 11 and 32 carry the bolts 36, 36 which engage the flange members 35 of the terminal element. Thus it will be seen that two bolts or screws 36 are all that are necessary to secure each of the terminal elements in place, these bolts being locked in secured position by the nut 37 as shown in Figure 2.

Each of the upper and lower terminal assembly membars 3% 31 also carry the spring biased disconnect contact elements 38, 38 also hereinafter more specifically described in connection with Figures 1 and 2, but shown also in Patent Number 2,029,028. The intermediate cross bar 13, which is secured to the vertical members 1%, 11 and 32 by the bolts 40, also carries at its outer end the wheels 42 on an appropriate shaft extension thereof, the said wheels 42 cooperating with appropriate tracks in the compartment to guide the truck into and out of the compartment properly.

The racking and indicator assembly shown generally at 43 of Figures 1 and 2 also carries the front wheels 44, 4-; 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 31 in the manner hereinafter described, and is provided with a link 51 which is connected to the contact operating arms 52 projecting up from the operating mechanism assembly 46. 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. The blow out coil assembly 53 which includes the coil 54 of Figure 3 and the laminated blow out iron legs 55, is mounted on the upper insulating back panel 56 also across the bars 15 and 14 and the upper portion of vertical supporting members 1i and 11 and is supported thereby.

It is spaced from the bars 10, 11, 32, 14, 15 by the upper insulating back panel 56 which panel is secured across the bars 10, 11 and 32 as shown in Figures 2 and 3. Appropriate openings 59, 59 are provided in the panel 56 to permit the terminal members 34 and 31 to project therethrough in a manner shown in Figures l and 3.

The are chute assembly 57 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, 58 on each side of the are chute as shown in Figures 1 and 5, and as will be more specifically described hereinafter in connection with Figures 1, 4 and 5.

The front are runner of the arc chute is not connected in any way to any of the other elements of the circuit breaker but is brought into the circuit by the proximity of the moving contact 29A thereto during the opening operation. The rear runner 296A of the arc chute 57 is connected to the circuit breaker through the blow out coil mechanism 53 by the clip arrangement indicated generally at 3 36 of Figures 1 and 4. The are chute is entirely supported by the laminated legs 55 of the blow out iron on each side, being retained in position by the latch assembly 61 (Figure 5) also hereinafter more specifically described.

The final unit assembly comprises the interphase barrier assembly indicated generally at 63 of Figures 2, 8 and 9, the interphase barrier being supported at the rear end by resting on the cross bar 65 (Figure 2) secured across the lower end of the panel 56 and by resting at the front end on the angle iron 66 carried by the racking and indicator assembly 43.

All of the elements of the circuit breaker as will be seen from an inspection of Figures 1 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 72l,648 filed January ll, 1947, comprises essentially a simple switch operating mechanism with the addition of the necessary tip unit trip-free operation and solenoid closing mechanism necessary for automatic circuit breaker operation.

Lower terminal assembly The lower terminal assembly 31 as shown in Figures 1, 2 and 3, comprises a bar of copper G insulated by an oblong Bakelite tube 151 with a conductive inner lining into which it has been pressed. The front end 152 supports the movable contact bridge assembly in a manner hereinafter specifically described, while the main dis connect contacts 38 are secured to the rear end 154.

The lower terminal 31 has the side flanges 156, 156 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, Z 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 159, the fiat tube 151 is used, said tube being provided with a conductive lining 162. This tube is placed over the bar and then pressed into tight engagement with the bar 150 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.

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 avoiding 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, 2 and 3 also comprises a bar 160 of copper having an insulating sleeve 161 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 160 has the conformation 164 to receive and hold the main disconnect contacts 33 shown in Figures 1 and 2. The front end of bar 169 has secured thereto the stationary main contact 167 and the stationary arcing contact 166 (Figure 3). The upper end of the front portion of bar 169 has secured thereto the insulating blocks and 168 (Figures 1 and 3), which have secured thereto the insulating plate 170 having the upper slotted extension 170a. Connector 171 is secured in any suitable manner to the insulating blocks 165 and 168 but is insulated from the contact bar 169 and the arcing contact 166 and stationary contact 167.

Connector 171 has a slotted or cut away portion 179 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.

M'ovable Contact assent/11y In Figure 3, We have shown one of the contact arms 89. The contact arm 80 comprises a pair of copper bars 18%, 131 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 rc.ation by the spacer washers 184-18=4. all of which are forced into proper current carrying relation by the spring washers 233-233. The upper ins de edge of the copper bars 18l)181 carry special are resisting silver alloy contact blocks 185 which comprise the main movable contacts.

The lower ends of the bars 13 and 181 are provided with the registering openings to receive the pin (Figures l and 3) which pin passes through the openings and through the slotted openings 188 (Figure 4) of the front end 152 of the lower terminal 31 which is received between the arms 180181.

The pin 187 is provided on (Figures 1, 3, and 4) carrying each side with 2. lug 190 the bar 191 which passes through openings 193a (Figures 3 and 4) of the side flanges 156. Compression springs 193 on each side are The contact arm eifeetively pivots about pin 200 (Figures l and 3) which is connected between the arms 181 and 180 and which carries tlee end of link 51 connected to contact operating arm 52. Thus, compression springs 193 force the contact arm 80 to rotate counterclockwise about the pin 200 within the limit of the length of slot 188 on the lower terminal and thus forces the movable contact 135 into close Wiping engagement with the stationary contact member 167 (Figures 1 and 3).

in any position of the arm 30 other than the closed position of the arm 80, compression springs 193 push the pin 1% over to the far right end slot 185; of the lower terminal of Figure 4. When the contact arm reaches the closed position of the contacts, the movable contact 185 bears against the stationary contact 167 and as the link 51 forces pin 200 and contact arm 80 into the closed position, the spring 193 yields because of the slope of the angular slot 188 to permit the wiping action to occur between the contacts 185 and 167 and the contacts to close firmly.

The forward end 152 of the lower terminal of Figure 4 is provided with silver alloy inserts 202, 202 to bear against the inner surfaces of arms 180, 181 of contact arm 80. Thus it will be seen that no pigtails are used, but appropriate elements are used on pin 187 to squeeze the lower ends of arms 181, 180 against the insert contacts 202 on the lower terminal.

The contact springs 193 are located close to the pivoted stud 187 which is a distinct advantage because they are well away from arcing zone. The connection of link 51 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 response to a rise in currents, magnetic forces developed in these contacts tends to increase contact pressure at all contact points. The arcing contact arm 204 is pivotally mounted on the pin 205 between the contact arms 180, 181 and the spacer washers 184, and is provided with an arcing contact element 206 and the horn 207. The lower end of arcing contact arm 204 is connected by the floating pin 210 to the link 211 which in turn at this lower end bears against the milled surface 212 of the milled pin 213 carried between the arms 180, 181.

Tension spring 215 connected between lug 216 and spring eye 217 is arranged to rotate link 211 clockwise around the bearing furnished by the milled portion 212 of pin 213. The lug 216 is adjustably mounted on screw 220 which in turn is received in the tapped opening 221 of pin 222 carried between the arms 180, 181. of screw 220 results in moving lug 216 to change the tension of spring 215 and thus increase the bias thereof.

Spring 215 thus acts on links 211 to cause the toggle 211--210--204 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 220 which bears against the end 225 of arcing contact arm 204. Tension spring 215, however, thus drives the arcing contact element 206 out to the left with respect to Figure 3 where it will make contact with the stationary arcing contact 166 before the main contacts engage and there 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 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 167 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 are chute or blow-out mechanism which would tendto drive an are down, an insulating Rotation 10 shield 230 is provided secured'to the screws 1 83 and flared out to protect the uninsulated portion of the lower terminal bar 150.

Spring 215 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 engagement for a substantial portion of the opening movement depending on the setting of screw 220 (Figure 3).

Blow out assembly The blow-out assembly 53 comprising the coil 54 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 236 (Figures 1 and 3) to the upper terminal bar 160. The opposite end of coil 54 is connected by lead 233 to extension 171a on contact bar 171 passing through a slot in the upper extension a of insulating strip 170 (Figure 3). Coil 54 is wound on an iron core 240 to which is secured the laminated blow-out iron legs 55 on either side.

We have found that preferably four such side plates on each side 4; thick ensure a proper distribution of magnetic blow-out flux over the full length of the side plates. Also we have found that in order to obtain a proper blow-out flux without inserting too much impedance in series with the are it is desirable that the coil 54 consist of 18 turns of copper strips of 1 x A The side frame members 242, 242 (Figure 3) of the blow-out assembly are secured against the core 240 by bolts 243 which also secure the plates 55 against the core. The side frame members 242 of the blow-out assembly have secured therebetween the upper block 245 by means of pin 246 and the lower block (not shown) by means of pin 248 and plate 249 by means of screws 250.

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 are chute described in Figures 3, 5, 6 and 7. The are chute assembly 57 mounted above the contact assembly tit) provides for a positive and eificient arc interruption. it consists of insulation side walls 257, front and back are runners 291 and 290 respectively (Figure 13) and a series of ceramic plates 260 (Figure 12) mounted in spaced relation transverse of the arc path and a strong magnetic blow-out field to force the are into the are chute.

The sides 257 (Figures 5 and 7) have fastened at their lower portion, adjacent the arcing area, inner arc resisting insulating plates 269-269 of special composition hereinafter described. The are resisting plates 269 are chamfered along their upper edges at 262-262 to provide a straight locking edge for the cross plates 260 and the spacers 261. The lower ends of the cross plates 260 and the spacers 261 are appropriately shaped to lit the chamfered edge 262.

As the are is driven into the chute by the magentic field, it passes rapidly through the are extinguishing ceramic plates 260 which are rectangular in shape at the top 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 261 is provided to support each plate and position it with respect to adjacent plates and forms with the long tapered surface of the plate, a triangular opening with the apex at the top for the passage of the arc. Each plate with its spacer presents a decreasing area for the 1 1 are as it rises and gradually squeezes it into a narrow slot 307.

The plates 260 are assembled alternately in 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 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 rapidly increasing its length and bringing it into contact with the larger and larger cool surfaces of the plates. The are 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 2tl7 passes the front are runner 291. The are formed by currents of low value is extended in the chute beyond the front are runner 291 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 207 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 arc between the contact arm 294 and runner 291 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 291.

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 3M. The length of the plates 260 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 suflicient. The are 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 260 are held in position in the arc chute by the insulating cross-bar 263 (Figures 5-7) carried in the slot 264 of the end pieces 267. Insulating crossbar 263 is securely fastened by bolts 265, 266 respectively, at the front and back end pieces 267 of the arc chute assembly 57 which extend up above the side plates 257.

The side plates 257 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 267. 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 257 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 261 for the crossplates 26% completely line the inside of the are coming in contact with the side plates at any point.

The material of which the cross plates 260 and the spacers 261 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 to increase the interrupting capacity, numerous materails 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 ma' terials were better. Porcelain, while quite good was too fragile and could not be manufactured in thin plates with sufficient accuracy to make it practical.

By far the best materialfound was the glass bonded mica consisting of mica dust and glass fused and presscd 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 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 260 and spacers 261 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 onto the laminated blow-out iron legs 55 so that the reinforcing bars 58, 53 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 270 (Figures 1 and 2) is provided on each side of the arc chute secured to the bracing bars 58 by screws 271 and having extension 272 extending down into the region of the contacts outside the plates 57.

The blow-out flux through the laminated blow-out legs 55 is also communicated to plate 270 and by extension 272 is communicated down into the region of the con tacts 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 61 secured thereto in any suitable manner as by the screws 233, 283 (Figures 5 and 6) 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 61 engaging detent 284 in laminated legs 55. To remove the arc chute it is only necessary to press in the latch assembly 61 to disengage the detent 284 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 are runner 290 and a front are runner 291 converging below the arc chute and toward the center in the region of the contacts, the front are runner 291 having extension 291A toward the contact and the rear arc runner 290 having extension 290A toward the contacts and the further rearward extension 293.

The portion 171A (Figure 3) 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 3) to receive the rearward extension 293 of the rear arc horn 290 of the are chute 57. 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 306 and the rear arc horn is thus connected to the end 233 of blow-out coil 54.

The section 29013 of the scar are horn rests on plate 171 to obtain further contact to the rear are horn 290. Thus when the section of the arc on the stationary arcing contact jumps to section 290A of the rear arc horn, the current path is from terminal Stl, bolt 236 to lead 235 to coil 54 to lead 233 to section l'ilA of member 171 and spring clip 3%. Then from spring clip 300 to section 29GB of rear arc horn 2%. Then through the arc chute to the movable arcing contact and then to the front are runner 291 as hereinafter more specifically described.

The cross plates 260 as shown particularly in Figure 6 are each of an insulating non-carbonizing material, preferably a glass bonded, mica ceramic material or of a material known as Tra'nsite. These plates are longitudinal members as shown in Figures 6 and 7 having a curve at section 303 of a very large radius; upward of this position they have a curve 304 of smaller radius; and above that position have an extension 305 entering the notch 260 and closing off that side of the plate.

The side of each plate opposite the ctn've is fiat. When the arc is first drawn it is driven up by the blow-out mechanism into the notch 314) of V-shaped cross-section formed by the curves MiG-3G4 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 307 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 305 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 are 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 of lengthening of the are as it is blown up into alternating thin narrow slots on each side. Thereafter the portion of the are between the cross-plates 260 is free to move up to superimpose on the lateral zigzagging or lengthening of the are, a vertical zigzagging or lengthening.

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

The shapes and the space between the U-shaped piece 171B and the stationary arcing tip 166 is such that the arc thereacross is struck and continues. This are is in parallel with the circuit through the windings of the blow out coil 54.

The voltage drop across the blow-out coil 54 is 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 2000 volts if all the current flows through the blow-out coil 54. This does not occur since the voltage will maintain the are between 171-B and 166. The current in the breaker therefore divides; part of it passing through the blow-out coil 54 and part of it through the are between 171-B and 166. 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-out coil is of a value such the drop in the coil equals the drop across the gap in parallel. The division of the current in the two paths is therefore different at different 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 arc is scarcely maintained. At higher current values lowing 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 accordingly 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 etfective at high current values without requiring it to carry the full short circuit current. The blow-out 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 insetting the blow-out coil is that the blow-out coil 54 is not in the circuit at any time except when opening a circuit. Therefore, it is not required 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 171*B and 166. The impedance of this gap determines the current flowing in the blow-out coil 54. By increasing or decreasing the length of this gap, its impedance is efiected 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 63 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 272 of the iron plate 270 (Figures 5 and 6) comes down on each side of the arc chute adjacent to the arcs between 171-43 and 268 and also between 171-B and 166. This increases the flux density at this point. The elfect on the are between 171-B and 2&8 which is horizontal is to drive it rapidly up the runners 2%, 291 and into the arc chute 57. The elfect on the are between 171-B and 166, which is vertical, is to drive it back against the insulating and heat resisting block 168. This insulating block may be provided with slots, grooves, holes 163 or other cooling means to deionize the arc and effect the blow-out characteristics of the breaker. it will be apparent that the size, shape and spacing of the extensions 272 will also effect the blow-out characteristics.

It will also be noted that the conductive bar 171 has a U notch indicated generally at 17113 therein, in which the upper arcing horn 207 registers, thus providing for simplified transference of the arc to the contact bar 1.71 and hence to section 290a of the rear arc runner 2% of the arc chute 57.

On further opening of the contacts the arc is blown up into the arc chute, the current path including contact bar 30 through bolt 236 and lead 235 through the blow out coil 54 and then through spring clip Silt) and conducting bar 171 to the arc runner 290. The are then passes through the arc chute to the front arc runner 291, then to the arcing horn 2597 on the movable arcing contact and down through the moving contact structure iii) to the lower terminal 31.

Normally the arc where the short circuit current is large will be extinguished as the movable contact reaches the position near the arc runner 291. 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 arc extends from section 2913 of are runner 291, below this are runner to arcing horn 207 on the moving arcing contact 264 and there the arc is cooled and blown out through the auxiliary arc chute 320 (Figure 6) 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 257 of the arc chute 57.

The insulating shield 230 above described in connection with Figure 3 prevents a low current are from being blown down accidentally contacting the terminal 31. Oseillograph tests have shown that rates of arc extinguishment ranging from .58 cycle at 63,200 kva. (4200 volts) to a 25 cycles at 3728 kva. (5000 volts).

The arcing time may be even slower at lower voltage and current values, but these values illustrate the efiiciency of my novel device.

Interphase barriers The interphase barrier assembly 63 is a complete structure shown in Figures 2, 8 and 9 sufficiently light to be easily handled by one man. Preferably it is installed as a complete unit as shown in Figure 2, but in the event storage space is at a premium, the interphase barrier may readily be stored knocked down to be assembled by driving a number of screws through registering openings.

The interphase barrier assembly as shown in Figures 2, 8 and 9 comprises a pair of side plates 330 connected together by the front plate 332. Corner pieces 335, 335 are provided at each side to receive the screws 336, 336 of the front plate 332 and the screws 337, 337 of the side plates 330.

Further reinforcing strips 340 are secured to the front panel 332 by screws 341 to provide a means of securement and spacing for the interphase barriers 345. An additional notched top strip 350 is secured to the front panel 332 at the upper end. the notches therein providing spacing elements for the interphase barriers. The rear of the interphase barrier may have cross bars 352, 352 secured thereacross by screws 353 entering into the oppo site outside panels 330. These cross bars may also be notched to receive and position the interphase barrier elements.

Each hole or space in the interphase barrier may have secured therein between appropriate reinforcing blocks 369 the horizontal barrier 361 to prevent ionized and heated gases from being blown down in the arc chute.

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, a fixed contact having a main contact member and an arcing contact member, a conductor, an insulator member extending between said conductor and arcing contact member for spacing said contact member a predetermined distance from said conductor, a

movable contact having a main contact for engaging said main contact of said fixed contact and an arcing contact for engaging the arcing contact member of said fixed contact, a floating pivot and an extension on said movable contact for electrically cooperating with said conductor, said extension being positioned further from said floating pivot than said movable contacts that after said arcing contacts separate a predetermined distance the arcing path from said fixed arcing contact to said conductor and thence to said extension forms a lower impedance path than the arcing path between said arcing contacts, and a blow-out coil connected between said arcing member of said first contact and said conductor, the spacing of said conductor and arcing member being arranged to provide a relatively low impedance path compared to the impedance of the blow-out coil for short circuit currents of large value and a relative high impedance path compared to the impedance of the blow-out coil for short circuit currents of small value to produce current flow in said blowout coil which varies inversely as the fault current.

2. In a circuit breaker, a fixed contact having a main contact member and an arcing contact member, a conductor, an insulation member extending between said conductor and arcing contact member for spacing said contact member a predetermined distance from said conductor, a movable contact having a main contact for engaging said main contact of said fixed contact and an arcing contact for engaging the arcing contact member of said fixed contact, a floating pivot and an extension on said movable contact for electrically cooperating with said conductor, said extension being positioned further from said floating pivot than said movable contact so that after said arcing contacts separate a predetermined distance the arcing path from said fixed arcing contact to said conductor and thence to said extension forms a lower impedance path than the arcing path between said arcing contacts, a blow-out coil connected between said arcing member of said first contact and said conductor, the spacing of said conductor and arcing member being arranged to provide a relatively low impedance path compared to the impedance of the blow-out coil for short circuit currents of large value and a relative high impedance path compared to the impedance of the blow-out coil for short circuit currents of small value to produce current flow in said blow-out coil which varies inversely as the fault current, and slots in said insulation for controlling the impedance of said are between said conductor and arcing contact member.

References Cited in the file of this patent UNITED STATES PATENTS 1,872,387 Baker et al Aug. 16, 1932

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