US3214548A - Gas-blast circuit interrupters with both stationary and movable pneumatically-operated contacts - Google Patents

Description

1965 J. E. SCHRAMECK ETAL 3,214,548

GAS-BLAST CIRCUIT INTERRUPTERS WITH BOTH STATIONARY AND MOVABLE PNEUMATICALLY-OPERATED CONTACTS Filed Jan. 24, 1962 5 Sheets-Sheet 1 V////////[&

. INVENTORS WITNESSES. Jack E Schromeck 0nd Rm/W81 R 6 WigiYom R. Segor.

Oct. 26, 1965 J. E. SCHRAMECK ET 3,214,548 GAS-BLAST CIRCUIT INTERRUPTERS WITH TATIONARY AND MOVABLE PNEUMATICALLY-OPERATED TS Filed Jan. 24, 1962 Sheets-Sheet 2 26 32 Fig.3. 2s

1965 J. E. SCHRAMECK ETAL 3,214,548

GAS-BLAST CIRCUIT INTERRUPTERS WITH BOTH STATIONARY AND MOVABLE PNEUMATICALLY-OPERATED CONTACTS Filed Jan. .24, 1962 5 Sheets-Sheet 3 United States Patent 3,214,548 GAS-BLAST CIRCUIT INTERRUPTERS WITH BOTH STATIONARY AND MOVABLE PNEUMATICAL- LY-OPERATED CONTACTS Jack E. Schrameck, Pittsburgh, and William R. Segar, Breutwood Boro, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed Jan. 24, 1962, Ser. No. 168,396 8 Claims. (Cl. 200-148) This invention relates generally to compressed-gas circuit interrupters and, more particularly to compressed-gas circuit interrupters having contacts which are pneumatically actuated.

A general object of the present invention is to provide an improved compressed-gas circuit interrupter which is of high speed and in which are erosion of the contacts is considerably reduced.

A more specific object of the present invention is to provide an improved compressed-gas circuit interrupter in which pressure-responsive means is associated with the relatively stationary contact structure of the circuit interrupter to insure that the main relatively stationary contacts will have no arc-erosive action exerted thereon.

Another object of the present invention is the provision of an improved compressed-gas circuit interrupter in which the main contacts are separated more rapidly than the arcing contacts of compressed-gas circuit interrupters of the prior art; and, consequently, the overlap distance between the arcing contacts maythereby be shortened to result in a circuit interrupter of considerably reduced arcing time.

Still another object of the present invention is the provision of an improved compressed-gas circuit interrupter in which by the simple expedient of utilizing the gas blast, which is normally used to effect are interruption, the relatively stationary contact structure may be modified to provide faster breaker operation, and, in addition, to reduce arc erosion exerted upon the contacts.

Generally, according to one particular feature of the present invention, an extendable auxiliary arcing contact is piston-actuated to eliminate arcing at the relatively stationary contacts. The gas blast, which is employed during the opening operation, is effective to operate the piston-actuated auxiliary contact toward the opening direction of the movable contact, so that the arc will be established between the movable and auxiliary contacts and not at the relatively stationary contact. As a result, the contact surfaces of the relatively stationary contact are maintained free of pitting and other arc-erosive action, was to be in good current-carrying condition in the closed-circuit position of the interrupter. According to another feature of the present invention, main contact structure is associated with arcing contact structure, and pressure-responsive means, responsive to the blast pressure, is operable to effect movement of the main movable contact structure in opposite directions to thereby more quickly effect the separation thereof. The overlap distance between the arcing contact structure may, therefore, be minimized to consequently result in a breaker having a shorter arcing period.

Further objects and advantages will readily become apparent upon reading the following specification taken in conjunction with the drawings, in which:

FIG. 1 illustrates a side elevational view of a compressed-gas circuit interrupter embodying features of the present invention, the contact structure being illustrated in the closed-circuit position;

FIG. 2 is a considerably enlarged fragmentary view of the contact structure disposed at the upper end of the circuit interrupter of FIG. 1, the contact structure likewise being illustrated in the closed-circuit position;

ice 1 FIG. 3 is a fragmentary view, somewhat similar to that of FIG. 2, but illustrating the position of the several contact parts during the existence of blast pressure conditions, with the auxiliary contact being shown in its extended position;

FIG. 4 illustrates a modification of the invention taken substantially along the line IV-IV of FIG. 5, the contact structure being illustrated in the closed-circuit position;

FIG. 5 is a sectional view taken substantially along the line V-V of FIG. 4, again the contact structure being illustrated in the closed-circuit position; and

FIG. 6 is a fragmentary view somewhat similar to that of FIG. 5, but illustrating the position of the several parts during the initial portion of the opening operation under blast-pressure conditions, in which the piston-actuated movable main contacts are illustrated in their partially retracted position.

Referring to the drawings and more particularly to FIG. 1 thereof, the reference numeral 1 generally designates a compressed-gas circuit interrupter. Generally, the compressed-gas circuit interrupter 1 includes a tank of high-pressure gas 2 containing a suitable high-pressure fluid 3, such as air under pressure. The pressure may approximate 300 p.s.i.g., for example.

Blast valve means, generally designated by the reference numeral 4, is effective to control the passage of high-pressure gas 3 from the tank 2 upwardly through a blast tube 5 and into an arc-chute structure 6, within which the established arc is extinguished, as more fully brought out hereinafter. Reference may be had to United States Patent 2,739,206 issued March 20, 1956, to Fritz E. Florschutz and Raymond H. Leitzel, and assigned to the assignee of the instant application for a description of the operation of the blast-valve mechanism 4. Briefly, the operation of the blast-valve structure 4 is such that counterclockwise rotation of the operating shaft 7, as effected by a piston rod 8, causes a cam 10 to valve disposed within the valve casing 12, and permit thereby a blast of gas to pass upwardly through the blast tube 5 between a movable hook-shaped and blade-shaped contact 13 and relatively stationary contact structure, generally designated by the reference numeral 14. As well known by those skilled in the art, the are, which is established between the contact structure 13, 14, is moved laterally upwardly into the arc-chute structure 6, where suitable splitter plates or other interrupting structure may be disposed to effect rapid extinction of the established arc.

FIG. 2 shows somewhat fragmentarily, and on a considerably enlarged scale the relatively separable con tact structures 13, 14 associated with the circuit interrupter 1. With reference to FIG. 2, it will be noted that the movable hook-shaped and blade-shaped contact 13 is cooperable with a jaw-type flexible relatively stationary contact 14 comprising a pair of split furcations 14a, between which the tip portion 13a of the movable contact enters for good contacting engagement, as illustrated by the closed-circuit position of FIG. 2. Additionally, it will be observed that an auxiliary movable arcing contact 16, having an arc-resisting tip portion 16a, is associated with the upper tip portion 13b of the movable contact 13. The movable auxiliary arcing contact 16 is fixedly secured to an operating rod 17 having a rod-end 18 secured thereto. Pivotally connected, as at 20, to the rod-end 18 is a rotatable actuating lever 21, pivotally supported intermediate its ends upon a stationary pivot 22, and having the lower end thereof linked, as at 23, to a link 24. The left-hand end of the link 24, as viewed in FIG. 2, is pivotally connected, as at 25, to a pressure-responsive means 26, assuming the form of a piston 27, which is responsive to the blast pressure present within a conduit 28, leading to the interior of the blast tube 5, as at the location 30.

From the foregoing description, it will be obvious that during the existence of blast pressure conditions within the interior 31 of the blast tube 5, this blast pressure will act through the conduit 28 and efiect rightward movement of the piston 27 to effect thereby, through the disclosed linkage, leftward extension of the auxiliary movable contact 16. As a result, all arcing will take place between the movable contact 13 and the pressureresponsive auxiliary movable arcing contact 16. As mentioned hereinbefore, the arc-resisting tip 16a insures resistance to arc-erosive action.

The practice used for switch connection in the high voltage compartment of the compressed-air circuit breakers incorporates the technique of a moving contact arm fitting between finger contacts, which gives good contacting pressure in the closed position. During are interruption, the arc is drawn upon the finger contacts and moved upwardly from the contact fingers to an arc tip directly above them due to the magnetic effect of the looped current path through the breaker plus the action of the compressed-air blast. A silver-tungsten tip embedded in the upper contact finger is electrically a part of the upper terminal casting. This tip is highly arc-resistant and withstands the burning action of the are thus eliminating burning of the contact fingers.

The circuit interrupter used for electric arc furnace duty is subjected to a larger number of operations than those used for power-house service duty thus increasing the mechanical wear on the moving parts. This increased mechanical wear on the moving contact arm and finger contacts, due to the two sliding metal-to-metal surfaces, causes grooves to form upon the cupaloy surfaces and results in extensive burning of the finger contacts. This may result in the frequent replacement of parts.

In the present invention, it is proposed to use a combination of pneumatically-operated butt and finger contacts. The pneumatically-operated butt contacts 16, with a silver-tungsten tip 16a, will reduce the mechanical wear exerted upon the arcing surfaces and can be adjusted to extend well beyond the finger contacts thus eliminating burning of the finger contacts 14a. During arc interruption, the arc will be drawn upon the silver-tungsten surface 16a of the butt contact 16, which will withstand the burning action of the arc. The finger contacts will give good contacting pressure for carrying normal load current of the interrupter.

As illustrated in FIG. 2, the physical structure of the contact arrangement comprises a piston 27 mounted within an operating cylinder 32 and connected by a mechanical lever 21 to the butt contact 16, which is operated by the air pressure during arc interruption and is returned by the stored energy in a compression spring 33 following are interruption.

The opening operation is as follows: During arc interruption, rotation of the shaft cam causes various levers to open a blast valve, thus allowing compressed air to pass from the reservoir tank 2 upwardly through the blast tube 5 and between the separating contacts 13, 14. Compressed air at the same time travels through a pipe connection 28, connected with the blast tube 5, and puts air pressure upon the piston 27 mounted in the aluminum cylinder 32. The piston 27 is connected by the mechanical lever 21 to the butt contact 16. R0- tatable lever 21 is pivotally mounted at the fixed pivot 22 by a brace 34 to give the desired forward and backward movement of the contact 16 during and after arc interruption. The force exerted upon the piston 27 is such that upon tripping of the breaker the acceleration of the butt contact 16 will be great enough to prevent the moving contact arm 13 from running away from the butt contact 16, thus eliminating arcing upon the contact fingers 14a, The silver-tungsten tip 16a embedded in the butt contact 16 withstands the burning action exerted by the arc. FIG. 3 shows the position of the contacts 13, 14 with the movable arcing contact 16 extended.

During arc interruption, spring 33 is compressed, and the stored energy used for subsequent returning of piston 27 to the closed-position upon completion of the interruption. After circuit interruption, the shaft cam 10 allows the blast-valve levers to drop off the cam, and the blast valve recloses. This exhausts the compressed air within blast tube 5 to atmosphere, which at the same time exhausts the air within conduit 28 and in back of piston 27, thus allowing compression spring 33 to return the piston 27 to the closed position.

FIGS. 4-6 illustrate a modification of the invention, as applied to the same type of compressed-gas circuit interrupter, as illustrated in FIG, 1. A trifurcated hookshaped movable contact arm 40 cooperates with three spaced jaw-type relatively stationary contacts 41-43 to complete the electrical circuit passing through the interrupter, as illustrated in the closed-circuit position of the interrupter 1, as exemplified in FIGS. 4 and 5 of the drawings. As more fully disclosed in FIG. 5, the trifurcated movable contact 40 includes an outer pair of main movable contacts 40a, 40c. Interposed between the outer main contacts 40a, 40c is an intermediate movable arcing contact 40b. It will be observed that the intervening movable arcing contact 4012 is disposed directly above the exhaust end 45 of the blast tube 5 so as to receive a direct blast of gas therefrom.

Relatively stationary main contacts 41, 43 have pistons 47 secured thereto, which are operable within pistonoperating cylinders 48. As viewed in FIG. 4, an air inlet passage 28' pneumatically interconnects the interior 31 of the blast tube 5 with the working faces 47a of the pistons 47 so as to exert fluid pressure thereon in a direction to drive the pistons 47 and hence the relatively stationary main contacts 41, 43, in a rightward opening direction to thereby more quickly effect the separation thereof from the movable main contacts 40a, 40c.

Preferably retracting springs 49 are provided, disposed between the base portions 41a, 43a of the relatively stationary main contacts 41, 43 respectively, and the cylinder heads 48, so as to effect retraction of the main stationary contacts 41, 43 following cessation of the gas blast traversing the blast tube 5.

In a manner similar to that previously described in connection with FIGS. 1-3 of the drawings, during the opening operation blast pressure causes rightward movement of the movable stationary main contacts 41, 43 from the movable main contacts 40a, 4110 to quickly effect separation therefrom. During the counterclock- Wise rotative opening movement of the trifurcated movable contact 40 about the pivot 50, as caused by the operating rod 51, an arc is established over the exhaust end 45 of the blast tube 5, whereby the upwardly passing flow of high-pressure gas carries the established are upwardly into the arc-chute structure 6, where arc extinction occurs in a manner described by the aforesaid patent.

FIG. 6 illustrates fragmentarily the position of the several parts during the opening operation, when the relatively stationary main contacts 41, 43 have been retracted by the operation of the gas blast. Following closing of the blast-valve structure 4, anda reduction of pressure within the blast tube 5, the retracting spring 49 effects leftward movement of the relatively stationary main contacts 41, 43 to the position illustrated in FIGS. 4 and 5 of the drawings.

The practice used for high continuous current rated low-voltage compressed-air circuit breakers incorporates the combination of main and arcing contacts. The main contacts are used for carrying the current rating of the breaker, and the arcing contacts are those on which the arc is drawn after the main contacts have separated. In order to prevent arcing upon the main contacts, the

moving mains are adjusted for a inch overlap on the finger contacts and a 2 /8 inch overlap of the moving arcing contact. This excessive overlap of the moving arcing armincreases the tripping time of the breaker. As defined. herein, the tripping time is the interval existing between the energizing of .the trip coil and the parting of the arcing contacts.

In the present invention it is proposed to use pneu matically-operated main finger contacts, which, during arc interruption, will part from the moving main contacts before starting movement of the moving contacts. This will decrease the amount of overlap needed on the arcing contact, thereby decreasing the tripping time of the breaker.

The physical structure of the pneumatically-actuated contact structure comprises a pneumatically operated piston 47 mechanically connected to each relatively main finger contact 41, 43 and operated by air pressure during arc interruption, and returned by the stored energy in the spring 49 after circuit interruption.

By way of recapitulation, the sequence of operation is such that during arc interruption, the trip coil of the magnet valve is energized allowing compressed air from the breaker reservoir tank 2 to pass through the valve on the upper side of the pneumatic mechanism, which operates the shaft 7 for parting of the moving contact arms 40. Compressed air at the same time will travel through blast pipe connection 5 on the outlet side of the blast valve within valve casing 12 to the back of contact pistons 47. This compressed air is then utilized to operate the contact pistons 47, breaking the contact between the relatively stationary main contacts 41, 43 and the outer contacts 40a, 40c of the trifurcated movable contact 40 before movement of the arcing contact 40b. This is accomplished due to the amount of overtoggle of the shaft 7 with respect to the operating rod 51 that locks the breaker in the closed position.

After circuit interruption, the compressed air is exhausted in back of the pistons 47 due to the reduction in air pressure in the upper part of the blast tube 5 and conduit 28' after blast-valve reclosure allowing thereby the stored energy in the springs 49 to return the contact pistons 47 to their closed positions, as illustrated in FIGS. 4 and 5 of the drawings.

The arrangement illustrated in FIG. 2 of the drawings utilizing the available air blast provides positive follow of the arcing contacts during interruption of the circuit, yet does not allow the usual restricting force of biasing springs which oppose closing of the circuit breaker. Thus the full closing effort of the mechanism is available for overcoming magnetic forces and permits using a smaller mechanism on higher-rated breakers.

Although there has been illustrated and described specific structures, it is to be clearly understood that the same were merely for the purpose of illustration, and that changes and modifications may readily be made therein by those skilled in the art, without departing from the spirit and scope of the invention.

We claim as our invention:

1. A compressed-gas circuit interrupter having a tank of compressed gas, a blast tube, an arc chute at the upper end of said blast tube, a trifurcated hook-shaped movable contact cooperable with three side-by-side relatively stationary jaw-type contacts to complete the electrical circuit through the interrupter, the central stationary jawtype contact being immovable, the combination therewith of pistons associated with the outer relatively stationary contacts, conduit means interconnecting said pistons with the blast tube, whereby the outer relatively stationary contacts move in an opposite direction than the movable trifurcated contact to increase the speed of arc drawal, and further whereby said central stationary jaw-type contact acts as a stationary arcing contact.

2. A compressed-gas type of circuit interrupter including a pair of side-by-side relatively stationary contacts,

, and the other relatively fixed in relation thereto, a pair of cooperating simultaneously movable contacts movable in the same direction and cooperable with said pair of sideby-side relatively stationary contacts, a source of highpressure gas, conduit means for supplying a blast of highpressure gas to the space between said other relatively stationary contact and one of the movable contacts for arc-extinguishing purposes, means utilizing a portion of the high-pressure gas flowing through said conduit means to pneumatically move said one relatively stationary contact in a direction opposite to the opening direction of the movable contacts, whereby arcing will occur only between said other relatively stationary contact and said one movable contact.

3. The combination in a gas-blast type of circuit interrupter of a source of gas under pressure, a pair of separable main contacts, a movable auxiliary arcing contact, means electrically connecting the movable auxiliary arcing contact with one of said separable main contacts, pneumatic means responsive only to the opening operation of the interrupter to move said movable auxiliary contact in the opening direction of movement of the other of said separable main contacts, whereby said one main contact may be relieved from arcing, and biasing means em ployed for efiecting retraction of said movable auxiliary arcing contact to thereby minimize the closing eflort imposed upon an associated operating mechanism.

4. A gas-blast type of circuit interrupter including a relatively stationary jaw-type contact, a movable bladeshaped contact cooperable with said relatively stationary jaw-type contact to complete the electrical circuit through the interrupter, a movable auxiliary arcing contact, means electrically connecting the movable auxiliary arcing contact to said relatively stationary jaw-type contact, pneumatic means responsive only to the opening operation of the interrupter to move said movable auxiliary arcing contact in the opening direction of movement of said bladeshaped contact, whereby said relatively stationary jawtype contact may be relieved from arcing, and biasing means employed to eifect retraction of the movable auxiliary arcing contact to thereby minimize the closing efiort imposed upon an associated operating mechanism.

5. A gas-blast type of circuit interrupter including a relatively stationary jaw-type contact, a movable bladeshaped contact cooperable with said relatively stationary aw-type contact to complete the electrical circuit through the interrupter, a movable auxiliary arcing contact, means electrically connecting the movable auxiliary arcing contact to said relatively stationary jaw-type contact, a tank of gas under pressure, a blast tube for communicating said tank with the region adjacent said contacts for are interruption, blast-valve means for controlling the flow of high pressure gas through said blast tube, pneumatic means responsive only to the opening operation of the interrupter to move said movable auxiliary arcing contact in the opening direction of movement of said blade-shaped contact, whereby said relatively stationary jaw-type contact may be relieved from arcing, and biasing means employed for etfecting retraction of the movable auxiliary arcing contact to thereby minimize the closing eflfort imposed upon an associated operating mechanism.

6. A circuit interrupter including a pair of separable main contacts, means defining a pair of separable arcing contacts, means responsive only to the opening operation of the interrupter to effect simultaneous opposite opening movement of said pair of separable main contacts, whereby arc drawal upon the pair of separable arcing contacts may be more rapidly achieved, and spring retraction means employed in connection with at least one of the separable main contacts to reposition the same at the end of the opening operation to a point which is closer to the cooperating movable main contact than the position of the same during the opening movement thereof.

7. A circuit interrupter including a pair of separable main contacts, means defining a pair of separable arcing contacts, means mechanically and electrically interconnecting one of said main and arcing contacts, means responsive only to the opening operation of the interrupter to effect simultaneous opposite opening movement of said pair of separable main contacts, whereby arc drawa'l upon the pair of separable arcing contacts may be more rapidly achieved, and spring-biased retraction means associated with one of the pair of separable main contacts.

8. In combination, a pair of separable main contacts, means defining a pair of separable arcing contacts, a source of gas under pressure, a blast tube for transmitting a flow of high pressure gas from said source to the region adjacent said contacts, means responsive only .to the openingoperation of the interrupter to effect simultaneous opposite opening movement-of said pair of separable main contacts, whereby arc drawal upon the pair of separable arcing contacts may be more rapidly achieved, and the responsive means including a pressure operated piston, and spring-biased retraction means associated with said piston.

References Cited by the Examiner UNITED STATES PATENTS 1,834,550 12/31 Reed 200--151 1,910,714 5/33 Reed 200 -151 1,944,403 1/3'4 Clerc '200148 2,822,449 2/58 Thommen 200-146 FOREIGN PATENTS 448,558 5/48 Canada. 643,304 4/ 37 Germany. 675,370 5/ 39 Germany. 87,834 11/36 .Sweden. 97,040 '10/ 39 Sweden.

KATHLEEN H. CLAFFY, Primary Examiner.

BERNARD ,A. GILHEANY, Examiner.

Claims (1)

1. A COMPRESSED-GAS CIRCUIT INTERUPTER HAVING A TANK OF COMPRESSED GAS, A BLAST TUBE, AN ARC CHUTE AT THE UPPER END OF SAID BLAST TUBE, A TRIFURCATED HOOK-SHAPED MOVABLE CONTACT COOPERABLE WITH THREE SIDE-BY-SIDE RELATIVELY STATIONARY JAW-TYPE CONTACTS TO COMPLETE THE ELECTRICAL CIRCUIT THROUGH THE INTERRUPTER, THE CENTRAL STATIONARY JAWTYPE CONTACT BEING IMMOVABLE, THE COMBINATION THEREWITH OF PISTONS ASSOCIATED WITH THE OUTER RELATIVELY STATIONARY CONTACTS, CONDUIT MEANS INTERCONNECTING SAID PISTONS WITH THE BLAST TUBE, WHEREBY THE OUTER RELATIVELY STATIONARY CONTACTS MOVE IN AN OPPOSITE DIRECTION THAN THE MOVABLE TRIFURCATED CONTACT TO INCREASE THE SPEED OF ARC DRAWAL, AND

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