US2886673A - Arc extinguishing chamber - Google Patents

Description

May 12, 1959 A. VAN RYAN & 5

ARC EXTINGUISHING CHAMBER Filed Feb. 2, 1956 2 Sheets-Shaet 2 NVEN TOR.

United States Patent O ARC EXTINGUISHIVG CHAMBER Anthony Van Ryan, Ocean Springs, Miss., assignor to McGraw-Edison Company, a corporation of Delaware Application February 2, 1956, Serial No. 563,()14

4 *Claims. (Cl. 200-150) This invention pertains to crcuit interrupters of the liquid immersed type.

A general object of this invention is to provide a circuit interrupter with an improved form of arc extinguishing chamber. Other objects are to provide the following: An arc extinguishing chamber characterized by high efiectiveness despite relatively small physical dimensions; a chamber which is rugged, simple in form, and convenient to assemble; a chamber characte'zed by the drawing of an arc into proximity with a fresh quantity of dielectric fluid, such as oil, and wherein the movable contact travels in a direction opposite from the flow of the dielectrically impaired fluid and gases generated by the arc during crcuit interruption; a chamber which is adaptable to the so-called dead tank type of interrupter having a large quantity of dielectric fluid or to low oil content crcuit interrupters; and, an arc extinguishing chamber which requires no pressure generating enclosure, thereby tending to interrupt consistently eflective regardless of whether high or low magnitude currents are flowing.

Achievement of the aforegoing and other more specific objects will be apparent on various occasions throughout the ensuing specification.

In general terms, the invention comprises a stationary arcing contact located at the end of an insulated tubular casing, and an elongated movable contact rod extending through the tubular casiug centrally and into contact engagement with the stationary contact. By any suitable Operating mechanism, the movable contact rod is caused to execute a rapid separation from the stationary contact and thereby draw an arc. The arc is drawn toward the direction in which the movable contact travels and into an arc extinguishing chamber which is characterized by it having a central passageway and one or more adjacent fluid ducts disposed about and communicating with the central passageway substantially coextensive with its length. Withdrawal of the movable contact rod creates an arc in the passageway formerly occupied by the rod. The arc is surrounded by the fluid ducts which confine individual columns of dielectric fluid which in turn act on the arc and eflect its extinction in a manner which will be described hereinafter.

The arcing chamber proper is completely blocked off at one end except for the single central bore which admits the movable contact therethrough. At is opposite end, the fluid ducts of the arcing chamber and the contact passageway open into the vicinity of arc initiation. The fluid and dielectrically impaired gases developed by arcing are expelled through relief orifices located in the insulating tubular casing immediately adjacent the stationary Contacts. The entire structure thus far outlined is completely immersed in a dielectric fluid such as oil.

According to the invention, when an arc is drawn by means of axial separation of the Contacts, it is initiated in the vicinity of the relief orifices and extended into the central passageway formerly occupied by the movable contact. The energy of the crcuit being interrupted Z,886, 673 Ice Patented May 12, 1959 is then converted to arc energy in the form of heat which manifests itself in a number of different ways, among which are vaporizing some of the metallic contact material, vaporizing and de-composing the fluid dielectric ambient, and elevating the temperature of the vapor and gases thus created to a superheated state. These components or total arc energy continue to increase while the movable contact increases its distance from the stationary Contacts. The object during this time interval is to dissipate as much as possible of the arc energy by expelling the dielectrically impaired, highly ionized, hot gases through the aforesaid relief orifices so that as the current wave form successively passes through zero, the amount of energy dissipated is greater than the additional energy derived from the arc at that time. Dissipation of the arc energy by means of expelling the hot ionized gases commences immediately upon arc initiation and is made a continuous process by `drawing the arc into the contact passageway which is surrounded by the fluid ducts. Hence, as arcing continues, more and more of the arc energy is expended upon fluid stored in the ducts. The fluid is vaporized and set in motion contiguous with the envelope of the arc in the direction of the relief orifices and the columns of the oil are maintained in the fluid ducts by virtue of the arc pressure, so that the movable contact is continuously drawn into fresh fluid until arc extinction is accomplished.

It is now clear that the delectric fluid stored in the fluid ducts exposes a continually receding front of cool oil to the extendng arc, thus, initially absorbing heat of vaporization and absorbing further superheat as the vapors are projected toward the open end of the ducts adjacent the relief orifices. By ,this means the fresh fluid columns attack the arc envelope completely about the latter`s periphery with violent turbulence, thereby tending to difluse the dielectrically impaired gases in the arc without extending the arc appreciably because of its confinement within boundaries of the fluid ducts. In one embodiment of the invention, turbulence is enhanced by impressing the fluid ducts with a helical configuration which causes the hot gases to develop a rapid rotary motion resulting in discharge of the gases through the relief orifices.

Embodiments of the invention will now be described in greater detail in conjunction with the accompanying drawings in which:

Fig. 1 is an elevation view, in section, of one form of crcuit interrupter embodying the arc extinguishing chamber constituting the subject of the instant invention;

Fig. 2 is an enlarged sectional view taken on a line corresponding with 2-2 in Fig. l, looking in the direction of the arrows;

Fig. 3 is a fragmentary elevation view, partly in section, of a modified version of the novel arc extinguishing chamber;

Fig. 4 is a sectional view taken on the line 4-4 of Fig. 3;

Fig. 5 illustrates the conflguration and stacking sequence of the discs comprising the arcing chamber of Fig. 3;

Fig. 6 is a sectional view of an alternative form of the novel arcing chamber; and

Fig. 7 illustrates the configuration and stacking sequence of the discs comprising the arcing chamber of Fig. 6.

Fig. 1 depicts the novel arc extinguishing chamber adapted to a crcuit interrupter of the low oil content type which includes an insulating housing 1 of porcelain or other dielectric material. Housing 1 is supported on a metallic base 2 to which a lead wire, not shown, may be connected. Base 2 is provided with an upstanding flange 3 which defines a socket for surrounding the housing`1 and 'cementing it at 4 into liquid tight sealing relationship. At its'upper end insulating housing 1 is cemented at 5 to a similar annular flange 6 depending from a metallic contact mechanism enclosure 7. Although enclosure 7,'in Fig. lis shown broken away, it is understoodthat the enclosureis substantially oil tight. The Operating mechanism may be of anywell known type which may cause movable contact lil to execute asubstantially straight line axial movement when subjected to its influence, but only one actuating link 11 thereof is illustrated here, for the sake of brevity. t is to be appreciated that radial swinging of link ll will cause movable contact rod 1 59 to travel axially with aquick action during a circuit interrupting operation.

The interier cylindrical bore 12 of porcelain housing 1 constitutes a concentric fluid reseivoir filled with dielectric fluid to a level indicated by dashed lines 13. A plurality of round holes 14 are provided `for the purpose of permitting expansion of dielectric fluid into lPPer metallic enclosure shell 'I' during circuit interruption and "for facilitating restoration of the normal fluid level by draining fluid back into reservoir 12 when the circuit interrupter has attained inactive condition.

An electric circuit through the circuit interrupter is established by means of a line wire, not shown, attached to metallic enclosure 7 which is in electrical connection with a set of stationary wiping contact fingers 15 pivotally 'supported on an annularly grooved post 16 and biased radially toward movable contact rod by means of tensonal garter springs 17. Current passes through movable contact rod 7.0 to another comparable set of stationary arcing contact fingers 20 normally electrically engaged with the free end of movable contact rod 10. stationary arcing contacts 20 are supported on a tubular conductive post 21 threadably mounted on a cylinder 22 which is in conductive relation with base casting 2 in a manner clearly evident from inspection of Fig. 1.

.Mounting cylinder 22 is Secured in position by a fianged attaching stud 23 which in turn is provided with 'a 'centrally located threaded and gasketed fluid drain plug 24.

In Fig. 1 the 'arcing 'chamber proper is indicated by the reference numeral 25 and is shown confined within an insulating tube 26, of Bakelite or similar material, rigidly interposed between lower 'column 22 and the bottom of metallic'enclosure 7. In this embodiment arcing chamber 25 consists of a plug of insulating material bored straight through its center to deflne a passageway 30 for movable contact 10 and it is also provided with a plurality of adjacent, parallel, longitudinal fluid ducts 31 which communicate with the central contact passageway 30.

Fluid ducts 31 are normally filled with oil so that there is in efiect three contiguous fluid columns coextensive with the central contact passageway 30. The fluid ducts 31, in Fig. 1 and the other modification, are each sealed off at an end toward which the movable contact 10 travels by a concentric disc 32 which is imperforate except for the central hole 30 admitting movable contact 10 into arcing chamber 25. Thus the arcing chamber is closed at one end, but at the other end the fluid ducts are arranged to discharge and communicate into a volumetric arc initiating region 33 immediately adjacent stationary contact 20. Region 33 is provided with a plurality of radial pressure relief orifices 34 which penetrate insulating tube 26 and permit the discharge of gases incident to arcing into oil reservoir 12. Upon cessation of arcing, orifices 34 also permit replenishment of the fluid in ducts 31 by reverse flow.

The Operating mode of the novel arcing chamber will now be set forth to aid in understanding the structure thus far described. When it is desired'to interrupt the circuit, movable contact 10 is rapidly retracte'd from engagement with stationary contact20, thus initiatng an electric arc between contacts 20 and 10 in the region 33. Upon this event, some'of the delectric fluid is Vaporzed and converted into a highly ionized, highly conductive gas and vapor mixture which is immediately discharged through relief orifices 34. As contact rod 10 continues to travel from arcing contacts 20, the arc is drawn into central contact passageway 30 in an area previously occupied by contact 10, the arc being confined by and exposed to the surface of the fluid columns in fluid ducts 31. As the arc is extended, it exposes a continually changing front of fresh fluid to its influence, thereby vaporizing more dielectric fluid and increasing the pressure of the generated gases. The pressure thus generated has the dual effect of holding fluid up in ducts 31 and also expelling the gases along the central arc envelope in the direction of relief orifices 34 during which process the freshly created gases intermix and entrain quantities of the earlier delectrically impaired and hotter gases. During the early stages of interruption, the arc energy continues to increase and much of that energy is transferred to fluid stored in the ducts. During this short interval of approximately one-half cycle, the arc is accumulating more energy than the interrupter is capable of dissipating. However, when the current wave form passes through zero, the energy inherent in the hot gases becomes eflective to further vaporize oil and impel the vapors from the ducts peripherally into the arc envelope. consequently, during the time that the current wave form approaches and passes through Zero, the amount of energy dissipated by the arcing chamber exceeds that being supplied to the chamber by the circuit under interruption and there results a net cooling and deionizing effect on the arc which tends to re-establish the delectric strength between the now spaced stationary contact 20 and the tip of movable contact 10, thereby precluding reestablishment of the arc following one of the. few subsequent current zeros.

Attention is now invited to Fig. 3 where is shown an alternative form of arcing chamber employing the principles of the invention discussed earlier. This modification of the invention has important attributes which were not brought out while discussing the embodiment of Figs. 1 and 2 but discussion of them will be deferred temporarily until comparable characteristics of the embodiments are described, using like reference numerals insofar as they are consistent. In Eig. 3 it will be noted that the arcing chamber, now designated by reference numeral 35, is confined by an insulating tube 26 similar to that shown in Fig. 1. The arcing chamber is likewise sealed at one end by a retained imperforate disc 36, which closes off the fluid ducts 41, 42 and 43 respectively, and has a central aperture 40 for admitting movable contact 10 therethrough. A volumetric space 33 in the region of arc initiation freely communicates with fluid ducts 41, 42, and 43 and permits free discharge of dielectrically impaired gases through it and radial relief orifices 34.

Considering Fig. 3 in conjunction with Figs. 4 and 5 it will be observed that the arcing chamber is composed of a plurality of individual non-conductive discs, which may or may not be oil absorbent, and that each disc is provided with a plurality of fluid duct apertures 41, 42 and 43 spaced from each other by an angle of degrees in this instance. The various discs, when stacked as n Fig.'3, are held in axial position by an insulating anchor pin 44 which extends through a selected one of a plurality of index holes 46, 47, 48 and 49 located near the margin of each disc.

By forming arcing chamber 35 of discs, it is possible to build up a structure of appropriate length to the partcular delectric strength desired. There is further advantage in permitting development of several helical fluid ducts adjacent the central contact passageway 40 without suflering the disadvantage of having to turn or internally bore the helical configuration. Helically shaped 'fluid ducts enable storing a greater quantity of delectric fluid for acting upon the arc drawn in the central contact pas,-

sageway 40. The method of forming an arcing chamber like that of Fig. 3 may be most clearly understood by reference to Fig. 5 where the various discs are arranged in the sequence in which they are stacked. Each of the consecutive identical discs are marked alphabetically.

Each of the discs are identical in the respect that they have a plurality of fluid duct apertures 41, 42 and 43 and a series of small, equally spaced index 'holes 46, 47, 48 and 49 arranged in an arc near their marginal periphery. In Figs. 3 and 4 the uppermost disc A is positioned with its index hole 46 placed upon insulating anchor pin 44. The next successive disc B is positioned with its'index hole 47 registering with the anchor pin 44 so that the latter disc is helically advanced with respect to the preceding one by an amount equal to the angle between the index holes. By repeating this process with the ensuing alphabetically successive discs C, D, E, F and G, three stepped helical fluid ducts are developed by the fluid duct apertures 41, 42 and 43. In this illustrative example, where the index holes are spaced 20 degrees apart, the stacking of eighteen plus one discs will cause the apertures to develop one complete helical fluid duct convolution.

It is not necessary that number of index holes in the discs form a complete circle around the discs for it may be seen that when index hole 49 of disc D is registered with the anchoring pin 44 and there are no more holes in a clockwisedirection following 49, it is merely necessary to invert disc E for properly positioning the next desired index hole 48 in line with anchoring pin 44. The number of discs stacked will, of course, determine the length of arcing chamber 35 which will in turn depend, to some extent, upon the voltage of the circuit to which the interrupter will be applied. Hence this embodiment is more versatle than that of Fig. l because it permits fabricating an arc extinguishing device of any desred voltage rating by using the same type of discs only in diiferent quantities.

When the arcing chamber is fully stacked according to the above outlined procedure, it is placed as a unit within an insulating tube 26 as shown. Thereupon an imperforate disc 36 is inserted to block off or blind end one corresponding end of each fluid duct, and the whole assembly is Secured in the tube 26 by a snap ring 51. The lower ends of the fluid ducts remain open and in communication with the arc initiating region 33, see Fig. 4.

The diameter of the various fluid duct apertures 41, 42, 43 and the contact passageway aperture 40 are selected in accordance with the magnitude of the current which it is intended for the arcing chamber to extinguish. Experimentation has shown that optimum interrupting Capacity, for any given interrupter built according to the invention, may be somewhat dependent upon the amount of helical advance between successive discs comprising the arcing chamber. The angular advance of the discs is easily controlled by varying the angle between the index holes.

Figures 6 and 7 illustrate fabrication of an arcing chamber which in final form is substantially identical with that described above, but it is modified in the respect that the various discs H, I, J and K are provided with only one index hole 56. Although the fluid ducts 58, 59 and 60 and contact passageway 55 in each of these discs is the same in size and shape as in the preceding embodiments, there is a dissimilarity between the discs in that the index hole 56 is shifted through an angle wit-h respect to the ducts, which angle corresponds with the helical advance of the ducts. This embodiment likewise permits stacking of an arcing chamber 54 of any desred length without requiring a diflerent type of disc for each layer of the helix, because as soon as the fluid ducts traverse a helix angle equal to the angular displacement of the ducts, stacking of the discs becomes repetitive. In the embodiment of Fig. 6, four different kinds of discs are required and the disc which would follow K would be merely an inversion of disc J.

It should be appreciated, that in connection with the description of all the previous embodiments, that the arcing chamber is not limited to any specific number of fiuid ducts. It is contemplated that where a design is proposed for interrupting larger magnitude current that the central movable contact 10 Would be larger in diameter and therefore, the discs and number of fluid ducts would be increased so as to provide a maximum quantity of oil contiguous with the central contact passageway when the movable contact is withdrawn during circuit opening operation.

The arcing chambers of Figs. 3 and 6 perform their arc extinguishing function in a manner somewhat similar to that described in connection with the structure of Fig. l. However, in the structure of the latter figures, action by the fluid in the ducts upon the arc drawn in contact passageway is greatly augmented by the turbulating action of the oil when it is emitted from the helical fluid ducts for attacking the arc completely about its periphery and through its length. This multi-sided attack upon the arc occurs not only in the arcing chamber itself but extends to the region 33 where the arc is initiated, and wheren further gyratory action occurs which tends to dilute and carry highly ionized, hot gases out through the relief orifices 34. The helical fluid duct configuration also has the advantage of increasing the total amount of fluid which may be brought into action against the arc envelope.

The invention has been described in connection with a circuit interrupter of the low oil content type. However, it will be perfectly obvous to those versed in the art that the novel arcing chamber, if properly mounted, may also be employed in connection with the large oil Volume or dead tank type of circuit breaker. The invention is also equally well adapted to a circuit interrupter wheren the movable contact executes its axial movement in a downward direction. This amounts to merely inverting the novel arcing chamber within its oil reservoir and taking appropriate steps to assure that the arcing structure is completely immersed in dielectric fluid as was the case in the embodiments described. Regardless of whether the arcing chamber is inverted or not, it is important, in order to comply with the teachings of the invention, that the arcing chamber be sealed at one end so that the arc is extended in a direction opposite from that in which the dielectrically impaired gases are expelled from the arcing chamber.

Although specific and general examples of the invention have been set forth, they are to be regarded as exemplary and not limiting, for the invention may be variously embodied and is to 'oe interpreted as claimed.

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

1. A circuit interrupter of the fluid immersed type comprising a s'tationary contact and a movable contact for drawing an arc therebetween, an arc extinguishing chamber having an axial passageway in which said movable contact is adapted to axially reciprocate, the end of said passageway remote from said stationary contact being closed by said movable contact in all axial positions thereof, said chamber being provided with a plurality of axially continuous fluid ducts of substantially equal cross sectional area which are substantially equiangularly spaced around and equidistant radially from said axial passageway, each of said ducts beginning adjacent said stationary contact with an opening in communication with the exterior of said chamber and terminating in a closed end axially remote from said stationary contact, the margin of said fluid ducts opening only into said axial passageway substantially coextensive with its length, whereby an arc drawn between said contacts is exposed only to the fluid in said fluid ducts and the dielectrically impaired gases produced thereby are discharged from said axial passageway and from said fluid ducts in a direction opposite of the movement of said movable contact.

'7 "2. The invention'according to claim 1 wherein each of said 'fluid ducts defines'a helixwhose peripheral nargin opens'into communication with a'dfierent porton 'of the margin of'said 'contact passageway as the ducts advance longitudinally of said passageway.

3. VA circuit interrupter ofthe fluid irnmersed type comprising, a stationary contact 'and 'amovable contact for drawing an arc therebetween, an are extinguishing chamber `having an axial passagewayiin which said movable contact is adapted to axially reciprocate the end of said passageway remote from said stationary contact being closed by said movable contact in all axial positions thereof, said chamher including a stack of insulating discs which are imperforate through their peripheries and each of which has a plurality of fluid duct apertures of substantially equal cross sectional area which are equiangularly spaced around and equidistant radially from the center of discs and a contact passageway'aperture intersecting therewith, each successive disc being uniformly rotatiorally advanced With successive fluid 'aperturesdefining a `uniform step-like helical fluid duct beginning With an opening adjacent said stationary contact and opening contiguously along its helical length only into said contact passageway, means 'for securing said 'discs in compressive relation, and means for blocking said fludducts at an end remote from said stationary contact Whereby gases incident to drawing an arc in said contact passageway discharge from said passageway and fluid duct in'a direction opposite from the movement of said movable contact.

- v 4. A circuit interrupter of the fluid immersed type comprising, a stationary contact and a movable contact for drawing an arc therebetween, insulating tube means enclosingsaidcontacts and having a relief orifice adjacent the vicinity of arc nitiation, an arc extinguishing chamber having an aXial contact passageway occupied by said mo /able contact and closed at one end thereby When an are is initiated, said chamber including a stack of discs that are imperforate through their peripheries and each having an axial contact passageway aperture and a plurality of fluid duct apertures of equal cross sectional area and radially and circularly equally spaced about the periphery of said axial aperture and intersecting there- With, each successive disc being uniformly angularly advanced in a step-like helical arrangement for defining independent fluid ducts of uniforrn cross section throughout their lengths and corresponding With the number of fluid duct apertures in each disc, and means for blocking said fluid ducts at an end remote from said stationary contact whereby gases, incident to arcing, flow only out of said relief orifice from the contact passageway and fluid ducts in a direction opposite to the movement of said movable contact.

References Cited in the file of this patent UNITED STATES PATENTS 2,109,685 Ainsworth Mar. 1,- 1938 2,467,542 Taylor Apr. 19, 1949 2,566,09S Scarpa Aug. 28, 1951 2,634,351 Umphrey Apr. 7, 1953 FOREIGN ,PATENTS 683,() Germany Oct. *28, 1939

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