US1902463A - Electric circuit breaker - Google Patents

Description

March 21, 1933. w. E. PAUL ELECTRIC CIRCUIT BREAKER Filed March 3, 19:51 2 sheets-sheet 1 ffffffffffff l March 21, 1933. w. E. PAUL 1,902,463

ELECTRIC CIRCUIT BREAKER Filed March 5, 1931 2 Sheets-Sheet 2 In Venter* VVIlliem E. Paul,

' vHis Attorneg.

' Patented Mar. 21, 1933 UNITED STATES PATENT OFFICE WILLIAM E. PAUL, OF SCHENEGTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK ELECTRIC CIRCUIT BREAKEB,

Application led March 3, 1931, Serial No. 519,757, and in Great Britain January 13, 1931.

My invention relates to electric circuit breakers, more particularly to duid-break circuit interrupters of the type wherein pressure generated in the interrupting fluid by arcing is utilized to cause interruption of 'the circuit.

7Ihe principal object of my invent-ion is the provision of an improved electric circuit interrupter of the fluid-break type having high current interrupting capacity which shall be efficient, reliable and positive in operation and simple and rugged in construction.. -Y

' A further object of my invention is an improved Huid-break circuit interrupter of the oil-blast type which shall have means for positively directing a blast of insulating liquid at high velocity from a pressure-conining chamber across an arc formed in said chamber causing interruption of the circuit.

My invention will be more fully sel'l forth in lthe following description referring to the accompanying drawings, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

Referring to the drawings, Fig. 1 is an elevational view, partly in section, of an elect-ric circuit interrupter embodying my invention;

Fig. 2 is a plan view taken along the line 2-2 of Fig. 1; Fig. 3 is a fragmentary View showing the circuit interrupter in the open circuit position; Fight is an elevational view,

' partly in section, of another form of my invention, and Fig. 5 is a fragmentary view of Fig. 4, partly in section, showing the circuit interrupter in the open circuit position.

In the embodment of my invention illustrated in Figs. 1 to 3 a switch casing generally indicated at 1 is divided into an inteoral or box-like lower pressure-confining c amber 2 and an upper chamber 3 by a strong insulating partition 4. The lower or pressure-confining chamber 2 is provided with an insulating lining -2 and contains an interrupting fluid or liquid as a. suitable insulating oil for example, the insulating liquid in the present instance filling the chamber 2 and the lower part of the chamber 3 as illustrated in Fig. 1. Immersed in the insulating liquid Wit-hin the pressureconfining chamber 2 are the circuit controlling contacts comprising a pair of stationary contacts 5 and 6 and a bridging member 7 connected to an operating arm 8 actuated in a manner hereinafter described. The stationary contacts 5 and 6 and the bridging member 7 may be of any suitable construction, as for example the well-known fingerand-wedge type, the contacts 5 and 6 being connected to the conductor studs 9 and 10 respectively extending through insulating and adjacent the break between the Contact 5 and the bridging member 7. The plan view in Fig. 2 illustrates a polyphase circuit interrupter having a set of contacts for each phase circuit and a pressure relief opening l13 opposite the upper break of each set. However, for the purpose of simplicity the description will be limited :to a single phase circuit interrupter, the apparatus and operation being identical for the other phases.

When the circuit is to be opened, the switch operating mechanism is released by the trip coil 14. in a manner hereinafter described causving the compression spring 15 to rotate the switch arm 8 in a counter-clockwise direction about its mounting shaft 16 to the position illustrated in Fig. 3. In order that the pressure relief of chamber 2 shall be practically limited to the openings 13, each switch arm 8 is designed to operate within a comparatively narrow slot 17 in the insulating partition Il communicating with each opening 13. In the open circuit position the arm 8 therefore practically occupies the| slot 17.

As is well known, the drawing of an arc in an insulating liquid, as oil, generates high pressure at a rapid rate,zthe pressure depending upon the intensity of the arc and the power to be interrupted. When the circuit breaker above described is opened under a heavy short circuit, for example,` the arcing at the moment of separation of the contacts generates gas and builds up the pressure rapidly within the chamber 2. As the contacts continue to separate it will be noted that the arc between the contact 5 and the bridging member 7 is drawn transversely of and opposite the relief opening 13, whereas the arc between the contact 6 and the bridging member is more remotely positioned with respect to the relief opening. Since the pressure within the chamber 2 can be relieved only by way of the opening 13, the arcing pressure at the remotely positioned break forces the insulatin liquid from the chamber through the relie opening 13 into the low pressure chamber 3, the insulating liquid during its flow forming a high velocity jet passing through the arc adjacent the relief opening. Due to the fact that this arc is not free to shift or dodge the blast of insulating liquid, since the flow converges thereon in passing through the relief opening, the arc is eifectively extinguished by the blastof insulating liquid with- 1n a very brief time. In an alternating current circuit the interruption of the current at the first zero value is complete if fresh dielectric is introduced between the contacts at a sufficient rate to counteract the recovery of voltage at the contacts. the arcing will not be reestab ished if the dielectric strength of the gap after the current passes through zero is increased at a rate greater than the rate of voltage recovery across the gap. In the present arrangement, the amountfand rate of introduction of dielectric into thearc gap is governed by the intensity of the arcing itself so that the current to be interrupted determines to a certain eX- tent its own interrupting power. lFurthermore, the pressure developed by the arc adjacent the relief opening can not oppose the arcing pressure within the chamber 2 in View of the rapid increase of this pressure due to the remotely positioned break so that a positive blast of'insulating iiuid is directed across the first-named arc at each circuit interruption. Therefore, the performance of this type of circuit interrupter is consistent and its interrupting capacity may be much more accurately predicted than in the case of the conventional oil circuit breaker. Furthermore, the utilization of the arcing pressure of the circuit to interrupt itself permits'-a-'zrugged and compact arrangement whereby-the interrupting capacity for a given size of breaker may be increased many times over that of the conventional liquid break switch.

The operating and tripping mechanism for In other words,

easily housed within the upper chamber 3.

The aforesaid mechanism is supported by and mounted within a housing 18 built in the detachable cover structure 19 which is secured, as by bolting, to the angle members 20 forming a frame for the casing. The opposite walls of the cover structure 19 are provided with bearings 16 Within which the shaft 16 is suitably ournaled.

`The operating and tripping mechanism comprises an overset toggle 21 having one end connected to the switch arm 8 and the other end to the link 22 which is pivotally mounted on the rigid support 22. The toggle is actuated to circuit closing position by suitable motive means, as a solenoid 23 having the plunger 23 engaging the bearing roller 24 at the pivotal connection betweenk the toggle 21 and thelink 22. The toggle is held in its overset or thrust-transmitting position by a lug 25 on one toggle link engaging a pin 26 on the other link, the reaction vof the opening spring 15 maintaining the locking toggle in the overset position shown in Fig. 1. The toggle 21 is arranged to be broken by an ofi'- set pin 27 mounted on a trip lever 28, which is normally biased by the spring 29 in a counterclockwise direction. The tripping lever-28 is provided with an extension 30 engaged by by a spring 32 into engagement with the extension 30. The opposite end of the catch 31 coacts with the movable plunger 33 of the trip coil 14 for releasing the catch upon actuation of the trip coil plunger. The consequent release of the extension 30 causes the trip lever spring 29 to rotate the trip level 28 counter-clockwise, thereby breaking the toggle 21 and causing it to collapse to the dotted line position indicated. Upon collapse of the holding toggle the opening spring 15 causes the switch arm to move rapidly to open circuit position.

During the opening movement of the switch arm 8, however, the resetting link 34 connected at one end tothe switch arm 8 and at its other end by a pin and slot connection 35-35 to the trip lever 28, is depressed causing the lever 28 to be moved against the bias of the spring 29 to its original or reset position. The link 22 in the meantime is free to drop by gravity to extend the toggle 21 to its overset position as illustrated in Fig. 3 so that the mechanism is in readiness for a reclosing operation by the solenoid plunger. When the solenoid plunger is moved upwardly from the position illustrated in Fig. 3 the consequent counter-clockwise rotation of the link 22 transmits the closing thrust directly to the switch arm 8 through the rigid'toggle 21, the link 22 forming with the rigid tolggle 21 a second or actuating toggle which is ..eld

opening 48, causes generation of high in the overset position shown in Fig. 1 by the stop member 24.

The form of my invention Aillustrated in Figs. 4 and 5 is generally similar iu principle to that above described and comprises a switch tank 36 containing an insulating liquid 37, as oil, within which the pressure-conlining casing 38 is immersed. The tank 36, which may be of the usual type employed in oil circuit breakers, is provided with an insulating lining 38 and a cover structure for supporting the insulating bushings 39 through which the conductor studs 40 extend. The lower ends of the insulating bushings 39 are immersed in the oil within the tank and have mounted thereon the stationary contacts 41, which may bev of the well known laminated brush type, and the auxiliary or arcing contacts 42 and 42'. The movable blade or bridging member 43 is provided likewise with arcing contacts 44 and 44` and is connected to the operating rod 45 extending'vertically through the tank and casing 38. In the present instance the casing 38 is supported by the bushings 39 and encloses the contact structure above described.

' In view of the high pressures to which the casing 38 may be subjected, the construction is preferably of strong laminated wood or other strong insulating material forming plate-like structure which may be rigidly bolted together at 46 as illustrated. A simple and rugged construction is obtained by bolting the opposite side walls to end wall members of sufficient width to permit free vertical movement of the bridging member within the narrow rectangular structure so formed. One of the end walls 47 is provided with a pressure relief opening 48 adjacent and substantially opposite the break formed at the arcing contacts 42 and 44. The arc between the contacts 42 and 44', which is remotely positioned with respect to the pressure relief ressure to force the oil at high velocity thrgugh the first arc and outwardly into the main oil body within the tank which is subjected only to atmospheric pressure. The extinction of the arc by the oil blast is therefore quite similar to that described in connection with Figs. 1 to 3 except for the fact that the pressureconfining chamber is immersed within insulating liquid in a larger tank. The chamber is likewise provided with suitable fluid vents (not shown) so that refilling of the chamber with oil after an interruption is not prevented by air pockets. It is also apparent that the casing 38 may be arranged so that its closed end is closer to the side wall tank, thereby reducing the size of the tank required for allowing free and substantially unrestricted venting of the pressure chamber through the relief opening 48.

Due to the high pressure generated within the casing 38 there is a piston effect tending to oppose the downward or opening stroke of the operating rod 45. This elfect in extreme cases may cause rebound of the operating. rod and bridging member toward closed position and possibly reestablishment of the arc. For the purpose of eliminating the piston effect on the operating rod and thereby eliminating the rebound action due to high pressure generated within the pressure-confning chamber, the operating rod is provided with an extension structure 49 equalizing the pressure acting on the operating rod. In the present instance the pressure equalizing means comprises hollow telescoping members 49', the upper member as illustrated in Fig. 4 suitably connected to the bridging member 43 and the lower member to the bottom of the casing 38. The lower telescopic member extends through the bottom of the pressure casing so that the interior of the telescopic structure is in communication with the main oil body within the tank 36. Accordingly, the pressure acting on the operating rod 45 within the chamber is equalized in both directions so that the aforesaid piston eii'ect is eliminated. When the switch is in the open position illustrated in Fig. 5 the telescopic structure occupies but little space in the lower part of the casing so that 'the pressure casing may be adjacent the bottom of the tank 36 if desired. If, however, limitation of space is not a consideration the operating rod 45 may have av solid extension passing entirely through the casing 38 and extending below the casing in the open circuit position for accomplishing the same result.

Itwill of course be apparent that the pressure-confining casing 38 may be arranged within the tank 36 so that the relief opening 48 is in the upper wall thereof and but a short Vdistance below the oil level. In this arrangement the insulating bushings 39 may extend through the side walls of the tank as indicated in the preferred arrangement in Fig. 1. The advantages of having a minimum hydraulic head at the pressure relief opening are at once clear since the mass of oil to be accelerated by the oil jet in passing through the arc is greatly reduced. Accordingly, the jet of oil encounters loss resistance and is blasted through the relief opening at high velocity. y

In the preferred arrangement illustrated in Figs. 1 to 3 the vertical arrangement of the chambers 2 and 3, in addition to limiting the hydraulic head at the relief opening 13 provides an unobstructed exhaust for the high velocity jet. In other words, the oil jet is not deflected in exhausting directly from the pressure chamber and is restrained only by the upper wall of the chamber 3. With this arrangement the pressure within the chamber 2 is not only materially reduced for a given interrupting capacity, due to the fact that the pressure in the chamber 2 is a considerable function of the hydraulic head at the contacts, but also high stresses in the switch casing are eliminated, as well as reduction of the Velocity of the escaping oil and gas clue to high friction losses.

Although in the present instance the con- Vrelief opening may be accelerated prior to the actual oil blast, thereby insuring maximum velocitv of the oil jet through the arc.

' This action likewiseoccurs to a varying degree when the contacts separate simultaneously or practically so.

It should be understood'that my invention is not limited to specific details of construction and arrangement thereof herein illustrated, and thatv changes and modications u may occur to one skilled in the art Without departing from the spirit yof my invention. What I claim as new and desire to secure by Letters Patent of the United States, is:

1. An electric circuit interrupter comprising a pair of contacts and a bridging member coacting therewith forming two breaks in series, a common pressure-confining casing for said contacts containing an insulating liquid in which said contacts are immersed, said casing provided with a pressure relief opening opposite and adjacent one of said breaks arranged so that the arc is drawn transversely of said opening, the other of said breaks being remotely positioned with respect to said relief opening so that pressure generated by arcing at said last-named break is effective to blast the 'arc formed at saidl first-named break through saidrelief opening by a high velocity jet of insulating liquid.

V2. An electric circuit interrupter comprising a casing having a partition dividing said casing into upper and lower chambers, said partition having an aperture therein` coacting circuit controlling contacts disposed within said lower chamber, an insulating liquid in which said contacts are immersed filling said lower chamber, and operating mechanism in said upper chamber causing separation of said contacts to form a plurality of breaks vin series, one of said breaks being adjacent and Aopposite said aperture arranged so that the arc drawn at said break is transversely7 of said aperture, and the other of .said breaks being remotely positioned with respect to said aperture so that the arcing pressure in said lower chamber is effective to blast the arc at said first-named break through said .aperture by a high velocity jet of insulating upper chamber. j

3. An electric circuit interrupter comprising a casing, an insulating partition dividing said casing into upper and lower chambers, said partition provided with.A an aperture forming a pressure relief opening for the lower chamber, coacting circuit controlv ing a tank containing an insulating liquid,

a pressure-confining casing within said tank and immersed in'said liquid, said pressureconfining casing provided with a relief opening freely communicating with the interior of said tank, and coacting circuit controlling contacts including a bridging member disposed within said casing and arranged to draw two arcs in series, one-of said arcs being adjacent and transversely of said relief opening and the otherv of said arcs remotely positioned with respect to said relief opening. said last-named arc generating pressure within said casing causing a blast of insulating liquidfrom said casing into said tank across and through said first-named arc.

5. In a circuit interrupter including a pressure-confining casing and coacting circuit controlling contacts disposed within said casing, said contacts actuated by an operating rod extending through a wall of said casing, anti-rebound means comprising structure forming a collapsible extension of said operating rod including a plurality of telescopic members subject to the pressure exteriorly of said casing so that said operating rod is not substantially influenced by the pressure within said casing.

6. A polyphase circuit interrupter comprising a pressure-confining casing common to all phases, coacting contacts including a movable bridging member for each phase circuit connection immersed in an insulating liquid within said casing forming two breaks in series, said casing provided with a pressure relief opening opposite an end ofeach liquid directed into said of said tbridging members, said bridgingtacts immersed in said liquid and separable Within said chamber to form arcs in series, said contacts arranged to draw one of said arcs adjacent and transversely of a relief opening in the upper wall of said chamber so that the hydraulic head at said arc is small, the pressure generated within said chamber by another arc projecting a jet of insulating liquid at high velocity across said first-named arc to exhaust through said relief opening.

In Witness whereof I have hereunto set my hand.

WILLIAM E. PAUL.

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