US2070315A - Circuit interrupter - Google Patents

Description

Feb. 9, 1937. H. RAwLlNsLE-r AL CIARCUITINTERRUPTE'R Filed 0.011. 18, 1934 2 Sheets-Sheet 1 FeB. 9, 1937. H. l.. RAwLlNs Er AL 2150705315 CIRCUIT INTERRUPTER Filed 001'.. 18. 1934 Compressed Borz'c Acz'a" WITNESSES lNvENToRs Herben* L. Raza/i775 and Milln? /v Uniti/70. w

ATTORNEY Patented Feb. 9, 1937 PATENT' oFFIcE 2,070,315 cmocrr INTERRUPTER Herbert I.. Rawlins, wilkinsbrg, and william n,

Cuttino, Pittsburgh, Pa., assignors to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation o! Pennsylvania Application october 1s, 1934, serial No. 748,802

11 Claims.

Our invention relates, generally, to expulsion circuit interrupters and is particularly concerned vwith the provision of improved mounting arrangements for such apparatus.

While expulsion circuitfintemupters take a multitude ofiorms, the so-called expulsion fuse is probably the best known example of these devices. Ordinarily, an expulsion fuse consists of a tubular member for dening the walls of an arc passage, a fusible element for establishing an arc within that pass/age, and a means for caus- A ing a blast of arc extinguishing gas to ilow longitudinally through the arc during the arc extinguishing operation. The blast of arc extinguishing gas is most readily secured by lining the arc passage with a material which is capable of evolvingl a suitable gas when placed in proximity to an electric arc, and to make the blast most effective, the tube is preferably closed at one end. Y

Expulsion fuse devices, such as those described above,vhave proven themselves very satisfactory and very `reliable'in operation when used out of doors, or in locations where space is not an imy i portant consideration. However, when the devices are utilized in restricted placs, several complications arise. Flrst,\the gas which is expulsively ejected from the fuse tube during the arc extinguishing operation is usually rather highly -ionized and thus semi-conducting. It such gas is allowed to contact adjacent live partsserious short circuits may be produced, with considerable resultant damage to the involved equipment. And second, due to space limitations, the fuses are usually mounted on two supporting insulators in such manner that the reaction forces of the out-ilowing gas blast produced within the f tube during the interruption of very large overloads produce cantilever stresses on those insulators. Frequently, the magnitude oit-'these stresses becomes sumciently greatto create a serious danger that the supporting insulators will be cracked or even entirely broken, and in many installations, due to the risk oi possible failure of the fuse supports, more oil switches have have had to be utilised.

One application for which expulsion fuses are particularly suitable k for the interconnecting of the individual capacitan'units of a power type capacitor, such'as Biosa used for power fac-A tor correction. In this service, space is almost always an important consideration and the usual high voltages involved so seriously complicate the problem of circuit interruption that a high capacity breaker must be used; oil or other liquid type breakers are impractical both because of their size and cost, and the most feasible solution appears to be inthe use of expulsion devices.

The prior art structures utilized expulsion type interrupters in conjunction'with numerous complicated arrangements for interconnecting the `capacitance units, but none of the arrangements so far developed has been quite satisfactory.. In the interests of economy, it is most desirable that the fuses be supported upon the'terminal insulators of the capacitors themselves, but the prior art fuses, due to their size, have always had to be mounted at such an angle that cantilever stresses were induced in those insulators during the circuit opening operation. Frequently, the insulators were broken as a result of these stresses,

-and the out-owing gases often contacted adjacent live parts with the result that short circuits developed. Further, the fuses were usually mechanically connected tothe strap conductors which interconnect the capacitance units and these conductors were many times bent in such manner that the re-straightening of them became impractical or quite impossible. Y A

As mentioned above, interconnecting means for this type of service preferably include expulsion fuses or like devices for disconnecting individual units from the associated circuit upon the failure of the insulation within that unit, or upon the occurrence of other predetermined conditions. To overcome the disadvantages of the prior art devices, the means Afor supporting the expulsion fuses should'be so arranged that the lstrap connectors are subjected to substantially nov stress during the opening'operation of the fuses. Also, the reaction forces exerted by the fuse should not subject the supportinginsulators to any substantial cantilever stress, and the outilowing gas should be directed away from the capacitance units and the adjacent live parts.

The primary object of our invention is to provide a structure capable of meeting the require ments which shall be simple in design andV relatively inexpensive to manufactm'e.

This object of our invention is accomplished through theprovislon of a novel means for interconnecting the individual capacitance units with each other. and with the appara-f tus. By mounting the expulsion ruses vertically upon the supporting insulators for the terminals of the capacitance units, all cantilever stresses are eliminated, and the out-flowing blast of arc extinguishing gas is directed away from the live parts of the apparatus.' Further, through' the provision of novel means which we will describe A in some detail later, the strap members which serve to interconnect the several units are subjected to substantially no stress during the operation of the fuse devices.

In order to further reduce the reaction forces exerted by the fuses, we prefer to utilize a device wherein the arc extinguishing gases.are,rfor the most part, condensable. If this is done, a condenser means may be added to the expulsion fuse structure, for controlling the out-flow of the arc extinguishing gas, and this device, by condensing at least some of the arc extinguishing gas minimizes both the possibility ofthe development of excessive pressures within the fuse and the reaction forces exerted by the outiiowing gases.

A further object of our invention is to provide an improved means for mounting expulsion fuses or similar devices, our improved mounting means to utilize but a single supporting insulator and Ato include means for preventing cantilever stresses from being induced in that insulator during the operation of the fuse.

A still further object of our invention is to simplify the structure of capacitor devices generally and to increase their reliability of operation.

yThese and other objects of our invention will be made more apparent by reference to the following drawings and description wherein we have particularly set forth the structural features of a preferred embodiment of our invention.

Referring to the drawings:

Figure 1 is an elevational view of a threephase capacitor structure embodying the princi- A4g-ing one ofthe interconnecting arrangements utilized in the prior art structures;

Fig. 5 is an enlarged elevational view of one of the expulsion fuse devices which is utilized in ,this embodiment of our invention;

Fig. 6 is a sectional view through the fuse structure shown in Fig. 5; and i Fig. 7 is a sectional view taken on the line VII- VH of Fig. 5.

' The capacitor structure shown in Figs. 1, 2, and 3 comprises, generally, a main closure I, a plurality of individual-capacitance uniis.'3, a means 5 for interconnecting those units, three hollow insulators I for permitting the passage of external leads through the closure I, and three -pin type insulators 9, supported on one of the end portions of the closure I, for providing terminals for the interconnected capacitance units.

As shown in the drawings, the main closure I comprises a frame II of angle iron and a base plate I2 which are welded together. Suitable top and side members of heavy wiremesh or sheet steel, which are removably supported upon the angle iron frame II by suitable screw fastenings or the like, serve to protect the individual units while at the same time permitting ready observation of their condition.

The capacitance units 3 are not an important part of our invention andlmay take anyy of the well known forms. As shown, they comprise an outer metallic casing I3 for enclosing the condenser units, and three hollow porcelain insuinterconnected by a strap conductor I6 and sultable cap screws I8.

The means 5 for interconnecting the several capacitance units includes three strap members I9 of flexible conducting material and twelve expulsion fuse devices 2i, two of which are associated with each of the capacitance units. One of the strap members I9 is adapted to engage the conducting member II which extends through the central-insulator I5 of each of the capacitance units and to be electrically and -mechanically connected to those members by suitable nuts 23. One of the expulsion fuse devices is supported upon each of the outer insulators I5, and these devices are electrically connected together by the two other conducting straps I9, as will be described later.

Each of the fuse devices 2| includes an arc extinguishing portion and a. condenser portion, as shown particularly in Figs. 5, 6, and 1. The outer walls of each of the arc extinguishing portions is defined by a rather thick walled tube 24, of fiber or other mechanically strong insulating material, which is threaded at either end. A hollow cylindrical liner member 25, preferably formed of compressed boric acid or some other material which is capable of evolving an arc extinguishing gas substantially all of which is condensable, when placed in proximity to an electric arc, is disposed within the `ber tube 24 and serves to define the outer walls of the arc passage 2l. A plug member 29 of conducting material is threaded into the lower end of the main iiber tube I and serves both to close one end of the arc passage 21,'and to provide a terminal for the fuse structure itself. a

The condenser portion of each of the yfuse devices is enclosed within a metallic tubular member 3| which is screwed onto the upper end of the cooperating tube 24. A threaded stud 33 projects outwardly from each of the tubular members to provide an upper terminal for the device, the

inner end of this stud engaging a hollow cylindrical conducting member 35 which is adapted to abut against the upper end ofthe fuse tube 24 and the liner member 25. A pin 31 prevents the stud 33 from disengaging the member 35.

Each of the tubular members 3| is lled with copper shavings or similar material, in order that it may act as a condenser during the normal operation of the fuse device of which it forms a part. The upper` end of each of the tubular members 3| is closed by means 'of a threaded plug 39 of insulating material which `has a plurality of openings 4I cut therein in order to prevent excessive pressure from being'developed within the condenser during its operation. A at circular member 43 of insulating material Vis normally positioned on top of each plug member 4I in order to 'close theupper end of the` fuse structure. Preferably the member 43 is retained in place by an adhesive or some other means which will allow it to be moved to open the upper end of condenser to the atmosphere upon the development of a predetermined pressure within the fuse device. -Through this arrangement, the member 43 can be used as an indicatorfor showing when the associated fuse has operated.

A fusible element is provided for completing the electrical circuit between the lower plug member 29 and the upper terminal (the outwardly projecting stud 33,) of each of the fuse devices. 'I'he lower' end of each of the fusible elements extends into a suitable opening 49 formed within they cooperating plug member and is soldered therein. and the upper end of each of the fusible elements is soldered lto aterminal portion 6| which is connected to the adjacent cylindrical conducting member 35 by a suitable screw 53.

The lowerend oi each of the plug members 29 is provided 'with a threaded opening 55 for engaging the threaded end of the conducting member I1 which extends through each of the lnsulators i5 `suilpported upon thev capacitance units 3. Through this arrangement, each of the fuse devices 2l is entirely supported upon one of the insulators which provide terminals for the capacitance units..l

By providing a separate fuse device in series with the electrical circuit connectingeach of the capacitance units with the associated equipment, the maximum possible protection is assured at all times. For example, upon the development ci a fault or other abnormal condition within any one of the individualv capacitance units the associate fuse immediately removes that unit trom the circuit and allows vthe remaining sound units, connected in parallel therewith, to function in the normal manner.

Since the end oi each of the expulsion iuse devices 2i which is open during the circuit intern rupting operation is positioned away from the capacitance units and the means for interconnecting those units, substantially all oi the gas which is liberated during the normal operation oi these devices is caused to vent away from the live parts of the apparatus, thereby assuring that voltage breakdown or short circuits will not result. The axis of the are passage 2l through each ci the expulsion iuse'devices substantially coincides with the axis of the conducting member il' extending through the cooperating supporting insulators therefor., By virtue of this, the ceramic portions oi the 4several insulators le are sub jected only to compressive stresses during the circuit opening operation ci the fuses. This ar rangement, through the elimination of cantilever stresses, eiectlvely prevents any cracking of the insulators l5, ordinary ceramic materials being comparatively strong in compression, although they are comparatively weak when subjected to cantilever stresses.

in order to minimise the reaction forces which are exerted by the individual fuse devices during the circuit opening operation, each of the are passages 21 is lined with a material which is ca .pablo of evolving an arc extinguishing gas, substantially all oi which is condensable in nature, when placed in proximity to an electric arc. The

- preferred material, borlc acid is particularly satisfactory, but other substances capable of evolving condensable gases may be used. When such a lining material is used, the condenser may be so proportioned that a very considerable portion of the outflowing gases may be condensed within the fuse itself. and as a result much ci the reaction iorce normally exerted by expulsion devices is effectively eliminated. Further, substantially all of the out-flowing gases may be readily cooled sulciently to render them non-conductive, and

vas a result, a much safer and much more reliable device is made possible.v i

A fragmentary perspective viewof' oney of the prior art devices is shown in Fig. 4'. In this structure, each of the capacitance units |03y ,is

provided with only two terminal insulators H5,

it having been found undesirable in .these structures to attempt. to utilize a double section unit,

due to the fact that it was diiilcult-to secure sufficient spacing of the insulators to accommodate the fuse devices without unreasonably and unnecessarily increasing the size of the units themselves. The inner terminals of each of the groups of two units are connected one to anu other by means of straps H9 of conducting ma terial,` and these straps are, in turn, interconnected by a third strap member |21 also oi conducting material, A porcelain insulator 123 is supported upon each of the short straps H9, and these insulators serve to .support a bus structure which includes a. loingitudinally extending conducting member 25 and a plurality of laterally extending conducting members i2'l. A. single fuse i2 is provided for each of the capacitance units. One end of each of these fuses is affixed `to the outer insulator H5 of the associated unit,

ythe :fuses i2@ were always mounted at a substan tial angle with respect to the longitudinal airis oi the insulators 'i i5. Further, their mounting was not rigid. Upon the occurrence oi a fault condition within any one of the capacitance devices, the ruse l2@ protecting that portion of the circuit blew in the customaryrnanner, and the arc extinguishing gas was liberated either at the upper end or the lower end of the fuse tube. Since atleast one of the terminals of each 'of the fuses engaged the conducting .means utilized for connecting` that fuse into tice circuit, the reaction forces produced durin@ the circuit interrupting operation often caused serious benoling of the interconnecting means, frequently resulting in sumcient damage to that means to necessitate its being completely removed when the unit was serviced. Moreover, the extreme iength oi the prior art fuse devices and their resulting angular displacement with respect to the axis of the supporting insulators H5, resulted in the production of large cantilever stresses during the interruption oi. abnormal overloads and the like,

which stresses often caused the breaking or the cracking of those insulators.

The advantages of our invention over this arrangement are obvious. Each of the expulsion fuse devices 2l is mounted so that the gas blast resulting from the operation of that device is nifl Further, the replacement of the fuse devices following their operation is much simpler in the structure of our invention than in the prior art arrangements. Since the conducting straps are A the stud 33 to the cooperating strap lilV and then to unscrew the fuse device itself from the conducting member il.

While in the foregoing we have disclosed how our invention may be utilized in conjunction with connecting means for capacitors, it is to be understood that many of the features of our invention are capable of much wider application. For example, the improved means .for' mounting expulsion fuse devices on a single insulator is capable of wide general application in the art. It is our desire, therefore, that the language of the accompanying claims shall be accorded the broadest reasonable construction, and that our invention shall be limited only by 'what is expressly stated therein, and by the prior art.

We claim the following as our invention:

l. In combination, a plurality of insulator unitsweach of which includes a means of frangible insulating material and a terminal member rigidly supported thereon, and means for electrically interconnecting said terminal members, each of `said terminal members having a threaded portion formed integral therewith, said interconnecting means including strap conductors for interconnecting at least some of said terminal members and a plurality of expulsion fuse devices for dis-v connecting individual terminal members from said plurality of interconnected members upon the occurrence of predetermined conditions, each of said fuse devices including means for defining an arc passage which is open at one end during the operation of said device, means for drawing the arc incident to the operation of said device within said passage, means for creating an expulsive blast of arc extinguishing gas through said arc passage during the arc extinguishing operation, a member of conducting material for closing one end of said arc passage, said member having a threaded portion adapted to cooperate with the threaded portion of one of said termina-l members in order that each of said fuse devices may be supported on that terminal member, said cooperating threaded portions being so arranged that the longitudinal axis of the arc passage withineach of said devices shall substantially coincide with the longitudinal axis of the insulating means upon which said device is supported, and a means of conducting material extending outwardly from each of said fuse devices adjacent the open end thereof and substantially at right angles to the longitudinal axis of the associated arc passage in order that said fuse devices may be interconnected without placing any of said strap conductors in the normal path of the arc extinguishing gas blast.

2. In electrical apparatus, the combination of a terminal insulator, and a fuse which is adapted to be mounted directlyupon said terminal insulator, said fuse comprising a tubular means of insulating material for dening the walls oi.' an

arc passage, a threaded member of conducting material which is adapted to close one end of said arc passage and to engage said terminal insulator in such manner that said fuse is rigidly supported thereon, the other end of said ,arc .passage being open at least during the circuit opening operation, means for establishing an arc within said arc passage, means lining said arc passage which is capable of evolving an arc extinguishing gas, a considerable portion of which is condensable,- when placed in proximity to an electric arc, and a condenser means entirely supported on said tubular member adjacent said open end for cooling and condensing the outowing arc extinguishing gas, during the circuit opening operation, in order to minimize the reaction forces exerted by said device on said terminal insulator.

3. A fuse which is adapted to be mounted dir rectly upon one of the terminals of the apparatus protected by said fuse, comprising a tubular 6 means for dening the walls oi an arc passage,

a threaded member of conducting material-which' is adapted to close one end of said arc passage, and to engage one terminal of the apparatus protected by said fuse, the other end of said arc t10 passage being open during the circuit opening operation, means for establishing an arc within said arc passage, means lining said arc passage which is capable of evolving an arc extinguishing gas when placed in proximity to an electric arc, 'l5 and a means for cooling said gas and for controlling the speed of outflow of said gas, during the circuit opening operation in order to minimize the reaction forces exerted by said device.

4. In electrical apparatus, a terminal insulator 20 therefor which comprises a centrally disposed conductor, threaded at one end, and a ceramic insulating member surrounding said conductor, and an expulsion fuse device for protecting said apparatus and the associated equipment upon '2 the occurrence of abnormal conditions,` said fuse being adapted to be entirely supported upon said terminal insulator and comprising a tubular means of insulating material for defining the Vwalls of an arc passage, a threaded member of 30 conducting material which is adapted to close one end of said arc passage and to engage the threaded end of said conductor in such manner that said fuse device is rigidly supported thereon, the other end of said arc passage being open at '35 least during the circuit opening' operation, means l for establishing an arc within said arc passage, means lining said arc passage which is capable oi evolving an. arc extinguishing gas, a considerable portion of which is condensable, when placed in proximity to an electric arc, and a condenser means entirely supported on said tubular member arhacent said open end for cooling and condensing the outfiowing arc extinguishing gas, during the circuit opening operation, in order to minimize the reaction forces exerted by saidy device on said terminal insulator.

5. In combination, an insulator, comprising a centrally disposed conductor of substantial length and a means of insulating material surrounding said conductor, an expulsion fuse device, and means for supporting said fuse device on said insulator in such manner that substantially all of the stresses induced therein during the operation of said fuse device are compressive in nature, 5 said fuse device comprising means for dei'lning an arc' passage, means for producing an expulsive flow of arc extinguishing gas, substantially all of which is condensable, through said arc passage, during the arc extinguishing operation, 60 and a condenser means for condensing at least a portion of said arc extinguishing gas during the arc extinguishing operation in order to minimize the reaction forces exerted by said fuse device on said insulator during the operation thereof. fc5

6. In combination, a plurality of spaced insulator columns which are arranged in such manner that the longitudinal axes thereof are substantially parallel to each other, each of said insulator columns being formed, at least in part, 70 of frangible insulating material; a. conducting terminal member supponted on each of said insulator columns; a plurality of expulsion fuse devices; means for supporting each of said fuse devices on one of said terminal members; and 75 a common bus bar means, adapted to be entirely supported upon said fuse devices, for electrically interconnecting those devices; said fuse devices being supported on said insulator columns in such manner that substantially all of the stresses induced in said insulator columns during the operation of said fuse devices are compressive in nature and that the arc products expelled from said fuse devices during the operation thereof are directed away from said bus bar means and said insulator columns.

7. In combination, a plurality of spaced insulator columns which are arranged in such manner that the longitudinal axes thereof are substantially parallel to each other, each of said insulator columns being formed, at least in part, of frangible insulating material; a conducting terminal member supported on each of said insulator columns at one end thereof; a plurality of expulsion fuse devices, each of which includes a tubular member which is closed at one end and is open at the other-end during the operatin thereof, means for establishing the arc incident to the operation of the device within said tubular member, means for causing a blast of arc extinguishing gas tonow expulsively through said arc to effect its extinguishment, and an outwardly projecting terminal means positioned intermediate the ends of said device; means for supporting each of said fuse devices at the closed end thereof on one of said terminal members; and a common bus bar means which is adapted to engage said outwardly projecting terminal means and to be entirely supported 85 cxthereon, for electrically interconnecting said fuse devices; said means for supporting said fuse de- `vices positioning each of those devices in such manner-that the longitudinal axis of said tubular member substantially coincides with the longitudinal axis of the supporting insulator column .therefor in order that substantially all the stresses induced in said insulator columns during the operation of said fuse devices shall be compressive in nature and in order that the blast of arc extinguishing gas incident to the operation of each of the fuse devices shall be directed away from said insulator columns and said bus bar means.

8. In combination, a plurality of spaced insulator columns which are arranged in such mannerr that the longitudinal axes thereof are substantially parallel to each other, each of said insulator columns being formed at least in part'of frangible insulating material; a conducting terminal member having a threaded portion supported on each of said insulator columns at one end thereof; a plurality of expulsion fuse devices, each of which includes tubular means for defining an arc passage which is open at one end -during the operation 'of said device, means for v said fusible devices may be supported upon one of said insulator columns in such manner that the longitudinal axis of the arc passage within the device shall substantially coincide with the longitudinal axis ot the supporting insulator Y therefor. and a terminal means of conducting material which projects outwardly from each of said fuse devices intermediate the ends thereof and substantially at right angles to the longitudinal axis thereof; and a common bus bar means which is adapted to engage said outwardly projecting terminal means for electrically interconnecting said fuse devices.

9. In combination, a plurality of insulator units, each of which includes a means of frangible insulating material and a terminal member rigidly supported thereon, and means for electrically interconnecting said terminal members in a predetermined arrangement, said interconnecting means including exible strap members of conducting material and fuse devices, each of said fuse devices being entirely supported on one of said terminalmembers, and means carried by each of said fuse devices for engaging and supporting at least one of said exible strap members in a current-carrying position, said strap conductor being supported in its current-carrying position on each of said fuse devices unaffected by the reaction forces exerted by the opening of any one o f said fuse devices which support it.

l0. In combination, a plurality of insulator units, each of which includes a means of frangible insulating materialfand a terminal member rigidly supported thereon, each of said terminal members having a threaded portion formed integral therewith, and means for electrically interconnecting said terminal members in a predetermined sequence, said interconnecting means including strap connectors and fuse devices, each of said fuse devices including tubular means i'or defining an arc passage, means for establishingc -the arc incident to the operation of said device other end of said arc passage being open at least during the circuit opening position, and means carried by each of said fuse devices intermediate its ends for engaging and supporting at least one of said strap conductors in a current-carrying position, said strap conductor being supported in its current-carrying position on said fuse devices unaffected by the reaction forces exerted by the opening of any one of said fuse devices which carry said means for supporting said strap conductor. y

11. In combination, a plurality of insulator columns, a terminal member rigidly mounted on each of said columns, and means for electrically connecting said terminal members including a plurality of expulsion fuses and continuous strap members of conducting materiall associated therewith, means carried by each of said fuse devices for supporting at least one of said strap members associated therewith in a current-carrying position for providing a continuous conducting path between the fuse devices connected by the strap member, each oi said fuse devices being entirely supported upon one of said terminal members and being-so positioned with respect to the associated insulator and said strap member that the continuous conducting path provided between said fuse devices by said continuous strap member is ,unaffected by the reaction forces exerted by the opening of any one of said fuse devices. C, HERBERT L. RAWLINS.

WILLIAM H. CUTTING.

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