US2717293A - Electric circuit interrupter - Google Patents

Description

Sept. 6, 1955 c. H. TITUS ET AL ELECTRIC CIRCUIT INTERRUPTER Filed Jan. 23, 1953 2 Sheets-Sheet l 2 i. J .I 24 Z: A

Inventors: Charles H. Titus, Richard E. Beclnar-ek,

Their After-neg.

Sept. 6, 1955 c H mus ETA,"

E IC CIRCUIT INTERRUI-Lfifl 2 Sheets-Sheet 2 Filed Jan. 25, 1953 fm 9 m m Wm M; w n .//t 5M @d QMW mm m c J T UJ .0 WWW 7 w W United States Patent ELECTRIC CIRCUIT INTERRUPTER Charles H. Titus, Havertown, and Richard E. Bednarek, Philadelphia, Pa., assignors to General Electric Ccrnpany, a corporation of New York Application January 23, 1953, Serial No. 332,914

4 Claims. (Cl. 200-150) Our invention relates to electric circuit interrupters and more particularly to high speed circuit breakers of the fluid-blast type which are required to interrupt alternating power circuits within a few half cycles.

It is recognized in the art that the effective interrupting range of a fluid blast circuit breaker depends, at the lower extreme, upon its ability to interrupt light current arcs and, at the opposite extreme, upon its ability to withstand without damage the high pressures generated when interrupting heavy current arcs. This invention relates to a scheme for meeting these requirements as they exist in circuit interrupters of the type wherein the are products are vented laterally from the general path of the are.

In this specific type of circuit breaker, as fresh unionized dielectric fiuid is driven into the arc path by appropriate means, such as by arc-generated pressure or by an impulse piston, exhaust passages direct the ionized gaseous products of arcing radially from the arc path. If these exhaust passages are made large enough to permit a sufficiently rapid discharge of fluid so as to prevent excessive pressure rises upon the interruption of heavy current, difficulty will be had, on the other hand, in interrupting a light current. This is the case because a light current arc generates a relatively weak pressure within the interrupter, and the exhaust vents are so large that this weak pressure will not impart suflicient velocity to the fluid blast to successfully extinguish the arc.

An additional consideration in this type of breaker is that because the vented arc products are highly ionized conducting gases, it is important, under most conditions of current interruption, in order to minimize the hazard of arc-restriking that these gases be dissipated as rapidly as possible from the interrupter and into the safer dielectric regions surrounding the interrupter. In order to effect this rapid dissipation, the exhaust stream should be vented by the shortest possible path to the surrounding dielectric medium. In this same connection, where a plurality of exhaust streams are provided, these streams should be directly vented to the surrounding dielectric medium without being allowed to communicate with each other or to accumulate within the interrupter. In order to obtain this desired control over the exhaust streams, it is important that the exhaust paths be precisely disposed in optimum directions and locations.

In accordance with the illustrated embodiments of our invention, we have provided a novel fluid-blast circuit interrupter which is simple in construction and coinprises a resilient bafile assembly which not only provides exhaust paths precisely disposed in optimum directions and locations but also provides exhaust vents which vary in size in accordance with the magnitude of the current being interrupted.

It is, therefore, an object of our invention to provide a new and improved fluid blast electric circuit interrupter which is simple in construction.

It is another object of our invention to provide a fluid 'blast circuit breaker which has exhaust vents which vary in size as a function of the magnitude of the current being interrupted.

A further object of our invention is to provide exhaust vents which not only are of variable size but which are also precisely disposed in optimum directions and locations within the interrupter so as to minimize the hazard of arc-restriking.

The invention will be better understood by considering the following description taken in connection with the accompanying drawings and its scope will be pointed out in the appended claims.

In the drawings, Fig. 1 is a sectional view through the axis of a conventional tank-type oil circuit breaker employing one form of the interrupter of our invention; Fig. 2 is an enlarged sectional view taken along the line 2-2 of Fig. l and showing a resilient baffle in its contracted position; Fig. 3 is a view similar to Fig. 2 except the resilient battle is shown in expanded condition; Fig. 4 is a sectional view of an interrupter which is a modified form of the interrupter shown in Fig. 1; Fig. 5 is a sectional view taken along the line 5--5 of Fig. 4 and i1lus trating one form of resilient baflle which might be used in the interrupter of Fig. 4; Fig. 6 is a view identical to Fig. 4 except the resilient baffle is shown in its maximum expanded condition; Fig. 7 illustrates an alternative form of expansible baffle; Fig. 8 illustrates still another form of expansible bafl le; and Fig. 9 is a cross-sectional view along the line 9-9 of Fig. 8.

Fig. l of the drawings illustrates a single interrupter element ll of a tank-type oil circuit breaker. The breaker comprises a pair of these interrupter elements (only one being shown). The interrupter elements depend fixedly from the top cover 2 of an enclosing tank 3 by means of a pair or" symmetrically inclined conductor bushings, one of which is indicated at 4.

Each of the interrupters 1 is disposed well below the surface of a dielectric fluid F, which preferably is oil, the level L of which is indicated as being near the top of tank 3. The interrupters 1 are electrically connected in series when a lift rod 5 is in the upper or closed position as shown. In this position a conducting switch blade 6 interconnects the current conducting structures within the interrupters 1, thereby completing a closed circuit through the breaker unit from an external line terminal 7 of the bushing 4 to the corresponding external terminal of the opposite bushing.

When the breaker is tripped to open, the lift rod 5 and its switch blade 6 are moved downwardly at high speed by suitable mechanism in housing 8. This downward movement effects circuit interruption by extinguishing the arcs drawn in the interrupter structure 1 as a rod-type contact 9 carried by the blade 6 is withdrawn from the interrupter structure. In a well-known manner, a downwardly spring-biased intermediate contact 16 moves in follow-up engagement with the contact 9, thereby separating from a fixed contact 11 to draw a pressure generating are between fixed contacts 10 and H. The separation distance between the fixed contact 11 and the intermediate contact 10 is limited by a stop shoulder 12, which constitutes a portion of the intermediate contact W and is adapted to abut against the top surface of a lamination 13, thus preventing further downward movement of the intermediate contact 10. When this intermediate contact it) becomes restrained against further downward movement, the rod contact 9 moves rapidly away from intermediate contact 10, thereby drawing an interrupting are between contacts 9 and 10. The pressure-generating are between contacts 10 and 11 subjects the fluid within the interrupter to a pressure which impels the fluid transversely through the interrupting arc in the direction of the arrows B shown in Fig. 1. This cross-blasting action will be explained in greater detail hereinafter.

The interrupter 1 additionally comprises an interrupter adapter casting 14 which defines a portion of a generally annular pressure chamber 15 about the pressure generating break. The remainder of the pressure chamber is defined by annular insulating plates 13 and 18 secured to the adapter 14 in a suitable manner to be described in more detail hereinafter. The chamber 15 may be provided with gas vents such as 16 to facilitate the reentry of fluid after each interruption. A valve disk 17 may be employed for closing these openings automatically so that pressure is not wastef lly dissipated their openings from the pressure chamber 15 during a Cil'CL interruption. Ample volume for this chamber provides for a rapid reclosing cycle for the circuit breaker.

The are extinguishing portion of the interrupter 2 comprises a stack of insulating plates 19, 2'3, and 2 with respect to pressure chamber 15 by suitable such as fiber or other insulated bolts 22 extending through registering openings in plates 33, 1?, 2t and a 'l internally threaded lugs 22' formed on the inner i of the adapter 14. Each plate 19, 22, and la. tral opening. These central openings register 11" other thereby defining a contra; arc passageway in the contacts 9 and 16 may move. The intermedwte insulating plates 13 and 1.) are additionally provided aligned openings defining a vertical blast passage such as 23. The arc-generated pressure from the chamber is effective to drive a blast of arc-extinguishing fluid don-:1 the passageway 23 and transversely through the intcn rupting arc in the direction of the arrows 8 show i in so Figs. l-3. This cross-blast effectively sweeps the i rproducts of arcing from the interrupter through the lateral vents 24 and directly into the surrounding fluid F in the tank 3. The exhaust vent 24 defines a direct straight line path extending from the path of the arc to the exterior of the interrupter.

In order to effectively interrupt heavy currents Without damage to the interrupter structure, it is necessary that the high are pressures produced by the heavy current flow be rapidly vented from the interrupter. On the other hand, light currents, such as encountered in ca tor switching, can be elfectively interrupted only if t e low arc pressures produced by the light current flow are utilized to the maximum extent. in order to the above requirements, it is desirable that the exhaust vents of the interrupter be comparatively large under ieavy current interruption, so as to permit rapid venting, and be highly restricted under light current interruption, so as to prevent excessive pressure relief, thereby permitting full utilization of the limited pressure generated.

In order to provide vents having a size varying accordance with the magnitude of the current, s constructed the baffle plates 29 of a fiber possessing a moderate degree of resilience, so that these baflies a e capable of expanding from the closed or almost cl-- condition shown in Fig. 2 to the condition shown in 3. A specific material may be the vulcanized ellulose fiber described in greater detail in U. S. Patent 2,284,342 to D. C. Prince et al., assigned to the same assignee as the present application. prises a bight portion 29a having mutually separable arms 2% gonneeted thereto. End portions of the arms 13') define the variable size exhaust vent 24. in order to a lot for the expansion of the baflles 20, these baffles are vided with registering openings 25 of a size consider: greater than that of the bolts 22 passing therethrou The openings 25 are positioned with respect to the bolts in a manner such that the bolts are adapted to serve as stops for limiting both the degree of expansion and the degree of contraction of the resiliently-expansible baflie. The bolts 22 merely anchor the resilient baflies 2-3 in the proper position with respect to the adjacent structure. These bolts 22 do not apply an axial pressure upon the resilient baflies which would be effective to prevent their operative expansion and contraction. It is obvious, of

Each expansible baffle 29 comcourse, that the bolts could be spring loaded so as to apply a frictional drag to the expansible baflies, if so desired.

It will be apparent that when a heavy current is being interrupted by the breaker, a relatively high pressure is generated in the pressure chamber 15. This high pressure impels fluid within the interrupter down the vertical passage 23, across the interrupting arc and through the vent 24 with a force sufficient to expand the resilient baffles 29 into the condition shown in Fig. 3. On the other hand, when light currents are being interrupted by the breaker, a relatively low pressure is generated within the interrupter. This low pressure is not of sutficient magnitude to expand the contracted batfle 20. Thus, it may be seen that the vent 24 remains substantially closed or as a mere slit, such as is shown in Fig. 2, during interruption of light currents. Because the vent is highly restricted during light current interruptions, suflicient pressure is built up within the interrupter to establish a cross-blast of sutficiently high velocity to effectively extinguish the light current are and to prevent its reignition after a current zero. It is obvious that currents of a magnitude intermediate the heavy and light extremes described above would expand the resilient baffle 20 to a condition intermediate that shown in Figs. 2 and 3, the exact condition being a function of the current.

in view of the above mode or" operation, it should be apparent that high current arcs are effectively extinguished without damage to the interrupter and that the low pressure generated by light currents is efiiciently utilized to extinguish the are accompanying such light currents.

Another feature of the invention which is apparent from the mode of operation described above is that the interrupting are is subjected to a cross-blast of dielectric fluid irrespective of the magnitude of the current being interrupted. Under all conditions of current interruption, a

concentrated de-ionizing blast is caused to act in a direction transverse to the axis of the arc. Thus, it is apparent that the are products are directed in the same predeten mined advantageous direction under all conditions of arc interruption.

In the arrangement shown in Fig. 4, we have shown the invention as applied to a single-break interrupter instead of the double-break interrupter of Fig. l. The invention as shown in the modification of Fig. 4 contains certain other additional features which are described in detail hereinafter.

The interrupter 30 of Fig. 4 comprises an adapter casting 31 having secured thereto a strong cylindrical pressure-confining insulating casing 32 for enclosing and reinforcing the internal structure of the interrupter. The lower end of the insulating casing 32 is defined by the throat member 33 constructed of insulating material and suitably secured into the casing, as by screw thread means 3 5. Mounted within the enclosing casing 32 is a baffle stack shown generally at 35 and held in position by suitable insulating spacer sleeves 36 and 37 interposed between the bafile stack and the respective end walls of casing 32.

The baffle stack 35 comprises a plurality of superposed horizontally spaced insulating plates 38, 39, 4'1), and 41. Between these insulating plates are disposed resiliently expansible baflie plates 42 shown in detailed plan view in Fig. 5. These insulating plates which form the baflie stack 35 have generally registering central openings which together define a centrally disposed arcing passageway.

Since the central openings in the plates 38-41 are generally circular, whereas the openings in plates 42 are irregular in shape, as may be seen in Fig. 5, the arcing passageway has a highly irregular surface. This irregular surface is eifective in promoting a turbulently impelled blast of dielectric fluid across the arc and through the vent 45, as will be explained in more detail hereinafter. The insulating plates of the baflle stack are held as a unit by a fiber bolt 43 extending through a passageway formed by registering apertures in the insulating plates. The

apertures of the resilient insulating plates 42 are substantially larger than the bolt cross-section so as to permit expansion of the resilient baffle from the contracted position shown in Fig. to the expanded condition of Fig. 6. As may be seen in Fig. 5, each of the resilient batiies 42 is generally annular in shape while in a contracted condition. Each baffle 42 has a bight portion interconnecting a pair of substantially oppositely-disposed thickened arm portions 44, the end portions of which define a closed, or substantially closed, exhaust vent 45, which may become enlarged to the size shown in Fig. 6 when the baflie is expanded by excessive arc generated-pressure. The enclosing casing 32 is formed with appropriate ports 45a arranged to properly register with the vents 45 of the resilient baffles. The exhaust vent 45 defines a direct straight line path extending from the path of the arc to the exterior of the interrupter. The thickened arm portions 44 of the bafile 42 are given the desired degree of resilience by providing them with suitable saw slots 46 extending along the length of said arms.

Above the baffle stack 35 is a pressure generating chamber 47 defined, in part, by adapter 31 and spacer sleeve 36 mounted within casing 32. Mounted within the chamber 47 are a plurality of fingers which are resiliently urged together to form a conventional stationary contact of the cluster-type. These fingers 48 may be spring pressed together by compression springs 49 interposed between the fingers 48 and a retaining cage 50 secured to the adapter 31. The movable contact is a reciprocable rod-type contact 51 which coacts with the stationary cluster-type contact so as to be embraced by the fingers 48 with appropriate contact pressure when the interrupter is in closed condition.

The operation of the arrangement shown in Figs. 4-6 may be described as follows. When the circuit is to be interrupted, the movable contact 51 is moved rapidly away from the stationary contact, thereby drawing an arc between these two contacts. This are reacts with the surrounding oil to generate a pressure within chamber 47. As the movable contact is further withdrawn and the arc extended into the arc passageway, the pressure within chamber 47 forces a mixture of relatively un-ionized gas and oil to be turbulently impelled against the irregular surfaces of the arc passage, into the path of the arc, and through the exhaust vents 45 and 45a. This blast action rapidly extinguishes the are at a current zero and sweeps the resulting are products in a transverse direction through the exhaust vents 45 and 45a. The effectiveness of the interrupting action is further promoted by the tendency of battles 38, 39, and 40, to elongate the are as it is impelled by the blast action about and against the surfaces 38a, 39a, 40a adjacent the central arc passageway. Since the pressure generated within the interrupter is a function of the current being interrupted, it is apparent that the resilient baffies 42 will be expanded to a degree dependent upon the magnitude of the current. Thus, when only a light current is being interrupted, the pressure generated within the interrupter may be insufiicient to expand bafiies 42. As a result, only a limited amount of fluid in the form of a diminished, but concentrated, exhaust stream is permitted to be vented through the highly restricted slit at 45 (Fig. 5), thus assuring that within the interrupter sufiicient pressure will be built up so as to effectively extinguish, or prevent a re-establishment of, the arc. Similarly, when a heavy current is being interrupted, the high fluid pressure which accompanies such a flow of current, forces the bafiie into an expanded condition, thereby enlarging the exhaust vent 45 and permitting the interrupter to be more rapidly vented of are products, thus preventing damage to the interrupter. Fig. 6 shows the resilient bafiie expanded to maximum condition, which occurs when maximum current is being interrupted. Intermediate values of current would, of course, cause the baffle 42 to be expanded to a condition intermediate that shown in Figs. 5 and 6.

An important feature of this embodiment of the invention is that under heavy-current interruptions, when the resilient bafile 42 is subjected to maximum stress, it is effectively supported about its entire peripl eral surface by the inner circumference of the strong cylindrical casing 32. I

' It should be noted that the bolts 43 merely anchor the resilient baffles in place. Neither these bolts nor the screw thread means 34 exert an axial pressure which would be effective to prevent the operative expansion and contraction of the resilient baffies 42. If desired, the axial pressure could be controlled, or eliminated entirely, by surrounding the bolt 43 with suitable spacer sleeves interposed between the rigid insulating plates 38, 39, 40,

and 41. Similarly, the bolt could be spring loaded so as to apply a frictional drag to the expansible baffie, if so desired.

Fig. 7 shows a type of resiliently-expansible bafiie 52 which might be used instead of baflie 42 in an interrupter similar to that shown in Fig. 4. This baffie 52 is formed of a shape which provides a substantially uniformly tapering cross section from the bight 53 to the vent 54. This particular cross section provides the resilient baffle 52 with a high degree of inherent flexibility. In the modification of Fig. 7, we have used a plurality of bolts 55 instead of the single bolt 43 shown in Fig. 4. These bolts 55 would be incorporated into the bafile stack in substantially the same manner as is the single bolt 43 of Fig. 4. By using more than the single bolt 43 of Fig. 5, there is no possibility that the expansible bafiles would become displaced out of proper registry with the vent 45a while in a contracted condition. It is readily apparent that the interrupter using bafiies 52 would operate in a manner similar to the operation described with respect to the interrupter of Figs. 46 and, therefore, no further description is considered to be necessary. Similarly, it is apparent that baffle 42 or 52 could be used in an interrupter of the type shown in Figs. 1-3 merely by substituting one of these types of bafiies for the bafiie 20 of Figs. 13.

In the modification of Figs. 8 and 9, there is shown still another form of resilient baffle which might be used instead of bafile 42 in an interrupter comparable to that of Fig. 4. In this modification the resilient baffle generally indicated at 60 comprises an arcuate bight element 61 and a pair of segmental arms 62, 63 which are pivotally connected to opposite ends of the element 61. The adjacent end portions of these arms 62, 63 form at 63a an expansible vent which registers with vent 45a. These pivoted arms 62 and 63 are forced together and into the contracted position shown in Fig. 8 by compression springs 64 and 65, which are anchored in registering pockets formed in the inner periphery of the casing 32 and the outer surfaces of the arms 62, 63. Bight element 61 is slotted at each of its ends so as to provide a pair of clevises 66, 67 at each end. Between the clevises of each pair is mounted the tongue portion 68 formed on each of the arms 62 and 63, as clearly shown in Fig. 9. Pins or bolts 69 and 70 extend through registering openings in the clevis and tongue parts 66-68 to serve as pivots for the arms 62 and 63. Each of these bolts could extend through the baffle stack in a manner similar to that disclosed for bolt 43 in Fig. 4. With the arrangement of Figs. 8 and 9, it may be readily observed that there would be no need for spacers about the bolts 69, 70 to control the axial pressure on the pivoted arms since, by properly dimensioning the parts of the baflle, the clevises themselves could inherently function to limit this axial pressure. As an alternative arrangement, the pins 69 and 70 could each be of a length less than the thickness of a resilient bafile. In such an alternative arrangement the bafiie would be anchored in position within the casing only by means of springs 64 and 65.

Since the operation of the device of Fig. 8 would be similar to that of the interrupters of Figs. 1-3 and 4-6, no further description is considered necessary.

Our interrupting tests have shown that for certain current ranges it is advantageous to hold the arms of the expansible batfle pressed together in a closed condition by a pre-determined spring force. The modification of Figs. 8 and 9 provides such a force by means of springs 64, 65. The integrally-formed baflies of Figs. 17 could be given this pre-loading, where desired, by constructing them of a more efiectively resilient insulating material, such as melamine glass, which is a melamine-aldehyde resin, in which case the arms would be provided with facings of fiber (or methyl-methacrylate, or other more heat resistant insulating material), suitably applied adjacent the vent slit. The resilient arms would force these facings together at the vent area thereby providing the desired closed, but expansible, pre-loaded vent. Although the vents in each baffle assembly have been shown and described as beingarranged in vertical alignment along the peripheral wall of the interrupter, it will be understood that these vents may be staggered about the periphery of the interrupter so as to produce the beneficial opposite or divergent exhaust vents described in U. S. Patents 2,539,175 and 2,545,334, both of which issued to C. J. Balentine and are assigned to the same assignee as the present application.

From the foregoing description it will be appreciated that the various forms which the bat-fie of our invention may assume all may be classified as being of an expansible split ring configuration having means for anchoring the baflie within the interrupter structure; anchoring means serving to maintain the split portion of the batfie disposed in a predetermined position so that said split portion may serve as a vent of varying size disposed in an optimum direction.

While we have shown and described particular embodiments of our invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from our invention, e. g., the bafiiles of our invention could be applied to gas blast interrupters. We, therefore, intend by the appended claims to cover all such changes and modifications as fall within the true scope and spirit of our invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

l. A fluid'blast circuit interrupter comprising a pressure confining structure containing an arc-extinguishing fluid; relatively movable contacts Within said str cture adapted to separate to draw an arc to be extinguished by fluid-blast action; said structure including a baflle stack having internal openings for directing said fluid blast into the path of said arc, said baflle stack containing a resiliently expansible baflle which comprises a bight portion and a pair of arms connected to said bight portion, said arms having end portions which together define an exhaust vent at one side of said baflle stack, said arms being mutually separable to vary the size of said exhaust vent in accordance with arc-generated pressure within said structure, and a pair of parallel spaced-apart rod members fixedly positioned in said baffle stack, said resiliently 1 expansible baflie having spaced-apart apertures each receiving one of said rod members, said apertures being large relative to the cross-section of said rod members and providing sufiicient clearance with respect to said rod members to permit said battle to expand and contract relative to said rod members and within limits determined by said rod members.

2. A fluid-blast circuit interrupter comprising a pressure confining casing containing an arc-extinguishing fluid; relatively movable contacts within said casing adapted to separate so as to draw an arc to be extinguished by fluidblast action within said casing; a baflle stack within said casing having openings for directing said fluid blast into the path of said are, said baflies stack containing a resiliently-expansible bafile which comprises a bight portion and a pair of arms connected thereto, said arms having end portions which define an exhaust vent on one side of said bafiie stack, said arms being separable in response to arc-generated pressure Within said casing to vary the size of said exhaust vent as a function of said pressure, the radially outer surface of said baflie having a configuration conforming to the radially inner surface of said casing and substantially coinciding with said radially inner surface when said baffle is fully expanded, and said casing having an exhaust port which is in substantial registry with said exhaust vent.

3. A fluid-blast circuit interrupter comprising a pressure confining casing containing an arc-extinguishing fluid; relatively movable contacts within said casing adapted to separate so as to draw an arc to be extinguished by fluid-blast action within said casing; a baflle stack within said casing having openings for directing said fluid blast into the path of said arc, said baflie stack containing a resiliently-expansible baifle which comprises a bight portion and a pair of arms, at least one of said arms having a slot therein extending along the length of said arm for increasing the flexibility of said bafile, said arms additionally having end portions which define an exhaust vent one one side of said baflle stack, said arms being separable in response to arc-generated pressure Within said casing to vary the size of said exhaust vent as a function of said pressure, and said casing having an exhaust port which is in substantial registry with said exhaust vent.

4. A fluid-blast circuit interrupter comprising a pressure confining casing containing an arc-extinguishing fluid; relatively movable contacts within said casing adapted to separate so as to draw an arc to be extinguished by fluidblast action within said casing; a bafile stack within said casing having openings for directing said fluid blast into the path of said arc, said baffle stack containing a resiliently expansible battle which comprises a bight portion terminating at one end in a clevis and a pair of arms one of which terminates in a tongue received in pivotally connected relationship in said clevis, said arms having end portions defining an exhaust vent, spring means forcing said arms together, said arms being separable in opposition to said spring means to vary the size of said exhaust vent as a function of said arc-generated pressure, said casing having an exhaust port which is in substantial registery with said exhaust vent.

References Cited in the file of this patent UNITED STATES PATENTS 1,955,213 Whitney et a1. Apr. 17, 1934 1,955,216 Whitney et a1. Apr. 17, 1934 2,539,175 Balentine Jan. 23, 1951

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