US2535702A - Electric circuit interrupter - Google Patents

Description

Dec. 26, 1950 w. F. sKEATs ETAL 2,535,702

ELECTRIC CIRCUIT INTERRUPTER Filed Sept. 21, 1949 Inventors: Wilfred T2. Skeats, Thellwell F?. Coggeshall,

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Patented Dec. 26, 1950 ELECTRIC CRCUIT INTERRUPTER Wilfred F. Skeats, Lansdowne, and Thellwell R.

Qoggeshall, Bala Cynwyd, Pa., assignors to General Electric Company, a corporation of New York .Application September 21, 1949, Serial No. 116,986

(Cl. 20D- 150) 4 Claims.

Our invention relates to electric circuit interrupters for power circuits, and more particularly to high speed electric circuit breakers of the liquid blast type for opening an alternating current power circuit within a few cycles.

In the operation of high speed circuit breakers of the aforesaid type, the main problem is to create an arc-interrupting liquid blast in as short a time as possible after the tripping impulse has initiated separation of the breaker contact structure. In a well known form of oil blast breaker the separation of the relatively movable contact structure in response to the tripping impulse results progressively in two arcs in series, the i'lrst of which is utilized as a pressure-generating arc for driving arc-extinguishing liduid through the other arc. Accordingly, in this form of circuit breaker, although the interrupting action is positive and very reliable. the interrupting blast is not made eiTective until the second arc has been drawn. This is a particularly important consideration where an interrupting time of but a few cycles is specified for the breaker since, in addition to the time lost due to the inertia of the moving parts, the interrupting time is further lengthened by the time required for the movable contact structure to move through the distance necessary for drawing of the second arc. In another well known form of oil blast breaker, the

separation of the relatively movable contact A structure in response to the tripping impulse results in the simultaneous creation of two electric arcs in series, the first of which is a pressuregenerating arc and the second of which is an interrupting arc. However. each of the gaps for these two arcs are equally large, whereas the pressure-generating arc gap need not be as large as the interrupting arc gap and the additional unnecessary travel of the moving parts recuired to produce this additional unneeded pressuregenerating arc gap distance increases the breaker interruption time unnecessarily, A pressuregenerating arc gap which is larger than necessary for interruption also creates an unnecessarily high pressure with resulting expense and diiliculties in providing an arcing chamber to withstand such pressure.

In this type of breaker it is also necessary that the movable contact structure be separated in' This isolating distance is con-- An object of our invention is, therefore, the provision of an improved high speed electric circuit interrupter of the liquid blast type which is effective to cause an arc-interrupting licuid blast immediately upon initial separation of the relatively movable contact structure and prior to the isolating operation. More specifically, a further 4object is the provision of an improved high speed series-breaker oil circuit breaker of the explosion chamber type wherein the arc-interrupting blast is created and applied immediately upon initial circuit-opening movement and separation of the contact structure. and wherein the fixed and movable arcing contacts are isolated within the interrupter casing substantially independently of and subsequent to the circuit-interrupting operation. A further object of our invention is the provision ci a circuit breaker of the above type wherein both pressure-generating and interrupting arcs are drawn simultaneously but in which the moving contact structure produces a pressuregeneating arc gap which is smaller than the circuit-interrupting arc gap.

In accordance with a preferred embodiment of our invention the contact structure is arranged to form a pair of arcing gaps in series including a pressure-generating gap and an interrupting gap, and is disposed within an interrupting chamber immersed in oil having exhaust ports adjacent and immediately opposite the interrupting gap. The gaps or breaks are formed by action of the contacts under the influence of a main movable contact member dis-posed exteriorly of the interrupting chamber. Upon initial contact separation, arc pressure formed at the pressuregenerating gap in the interrupting chamber drives oil through the interrupting are adjacent the chamber exhaust ports and the circuit is thus interrupted at the interrupting gap. Further limited separation of the contacts within the interrupting chamber takes place and is followed by separation of the main movable contact member away from the arcing contact structure in the interrupting chamber, so that an isolatingr break eXteriorlv 0f the interrupting chamber is formed thereby. In the circuit-closing operation the movable contact member is raised in the oil to rst close the isolating gap and then force the arcing contacts within the interrupting chamber into engagement. The arcing contact structure within the interrupting chamber is arranged to provide an interrupting gap larger than the pressure-generating gap.

Our invention will be more fully set forth the following description referring to the accompanying drawing, and the features of novelty which characterize our invention will be pointed out with particularity in the claims annexed to and forming a part of this speciiication.

Referring to the drawing, the single figure thereof is an elevational view, partly in section, of a circuit interrupter showing only .one `of a pair of arcilla structures embodying the present invention.

The drawing illustrates an oil circuit breaker oi the type wherein a pair of fixed arcing structures, one of which is indica-ted at l, are interconnected by a bridging member 2 in the closed circuit position. The bridging member 2 is op erated vertically by a lift-rod 3 -for .opening and closing the breaker. The arcing structure l comprises essentially a pressure-comming chamber which is formed, in the present instance, by a cylindrical insulating casing member l. composed of a mechanically-strong insulating material such as a paper-lled phenolic resin. The chamn ber so formed is substantially closed `at its opposite ends and is immersed in a .suitable insulating and .arc-extinguishing Vliquidsuch as oil.

For the purpose of forming .a pair .ci breaks in series within the chamber, arcing contact structure mounted for limited movement is .disposed therein .comprising .contact bridging mem.- ber t. This .contact member is mounted on an insulating operating rod E eri-gages xed contacts i rand il suitably iixediy mounted within the insulating casing d. Operating rod t is, in turn. telescoped into and .carried within .operating tube ifi. tod-s, tube it. and the parts appended thereto, and movable therewith, ein elusive of contact member 5. will her after be referred to .collectively as the opera ing carriage. Contact is electrically connected through conductor 9, an end cap 2d, and a exible conductor i@ Vto a butt contact member H (mounted at the lower end of tube l) which is adapted to be engaged the isolating contact element l2 of the bridging member 2.

The circuit throuffh the breaker in the closed circuit position, beginning with the fixed ter-- minal structure generally indicated at i3, coinprises a conductor lll interconnecting the terminal `structure and the Contact l, pivoted contact 5, and contact S, conductor 9 end cap 2d, iiexible conductor is, contact ll, contact l2, and bridging member 2. Conductor 9, which extends along the inner wall of casing il, is suitably insulated from the interior of the chamber by an insulating strip I5 in order to localize one terminal of the pressure-generating arc at the Contact .8. The operative carriage comprising the tube le, rod and movable con-tact e are normally biased to the open-circuit position by a spring Il. The breaker is hel-d in the closedcircuit position by the bridging member 2 which engages the lower end of tube i6 through the butt contact-s il and l2 so as to urge the ol?- erating carriage upwardly into cont-aetemaking engagement against the bias of spring il.

Referring more particularly to the specific structure employed, the nxed terminal structure at i3 comprises an adapter it which is'connected d end of the casing. The pivoted bridging contact member 5 and the insulating rod d have limited travel rela-tive to operating tube i5, the limits being defined by a stop bushing 2d thread ed on the upper end of tube It and an ternal shoulder 2i within the bore o1" tube i denition oi movement is accomplished by the cooperation of these parts with an integral flange 22 on rod 6. Rod s and pivoted contact member 5 are normally biased upwardly with respect to tube I5 by a spring a3. This resilient connect? is for the purpose of providing sunicient c tact pressure and wipe at the contacts and in order to prevent excessive shock during the circuitclosing operation The lower part of the casing i is substantially closed by the operating tube i@ and an end cap 2d which is suitably secured to a ring 25 by means of cap screws as at 250,. Ring 2s is secured in cylindrical member d by circumierentiallyspaced cap screws (not shown) which extend radially Vinwardly through holes in cylindrical member l into threaded holes in ring 25. A hollow metallic tubular member V22E is threaded into the inner periphery oi `end cap and proides at its lower edge 23 a lower bearing for tube it and .substantially .sealing the lower portion of the casing. An upper bearing is provided by the rounded inner lip portion of end cap 2li and Downward movement of operating carriage it is limited by the lower periphery 2S 0i bushing 2d as it meets a buffer plate 2a which rests on the upper surface of .end cap 2d. Thus, as .bridging ,member 2 and isolating contact l2 move downward ,as the .circuit breaker opens, the lower limit of downward ,movement of tube i@ is reached, contact i i stops, and isolating contacts il and l2 are thereafter separated by continued movement oi contact it.

For the purpose of yutilizing the .are pressure generated within the .chamber immediately upon initial separation of the contacts, there are provided expulsion .or exhaust ports in the chamber walls immediately adjacent to the contacts adapted to carry the interrupting arc, so that the are pressure created Within the chamber at the pressure-generating arcing contacts is eective to drive oil into the path of the interrupting arc and through the ports to thereby interrupt the circuit at this point. In the present arrangement a pair of diverging ports 3S for splitting the arc at two points are located adjacent and immediately opposite the break between the con tacts 5 and l so that arc-.generated oil vapor pressure within the casing tends to drive two jets .ci oil transversely across the arc at said break. The lports within the chamber vare faced with suitable arc-resisting insulating material indicated at 3l. Accordingly, the arc pressure lgenerated at the breaks between contacts and 3 is effective to drive oil from within the are chamber into the path of the interrupting arc and through the expulsion ports above described for interrupting the circuit.

Pivoted bridging contact member 5 is connected to insulating rod 6 through a pivot 32 and a slotted hole 33 in rod 6. This slotted connection permits a .certain limited vamount of relative movement between contact' and rod 6, the purpose of which will be described below. However, since .the relative movement is limited, as the operating carriage descends, if there is a slight weld at either contacts l or 8 which holdscontact member 5 in the closed position, the operat ing rod 6 atY the upper end of slot 33 hits pin 32 and Contact member 5 is moved positively downward by impact action.

Contact member 5 is provided with an additional pivot pin 34 adjacent to iixed contact 8. This pin protrudes on both the iront and back faces of contact 5 and engages slanted guide slots 35 provided in plates 3-5 of insulating material which are fastened to the sides oi casing 4. There are two plates S, one in front and one in back of contact 5, but only the back one is shown in the drawing. It will be seen that because of the configuration of this sot, contact 5 as it descends, is gradually guided and tilted downwardly to the left, the left end descending more rapidly than the right. In the extreme open position, contact 5 is oriented as shown by the dotted lines wherein it is restrained from further downward movement by the guide pin 3d in slots 35 and the pin 32 in slot S3 of the operating rod 6. In this position, the operating carriage has descended completely, with surface 28 of bushing 25 against the buffer 29.

In operation, contact member 5 begins its downward opening movement at both ends at substantially the same time, forming an arc gap y at both contacts l and 8 at substantially the same time. However, because of the faster descent of the left end of contact member 5, the interrupting gap between contacts 5 and l increases more rapidly tl: an the pressure-generating gap between contacts 5 and 8. This is desired, since the gap for the pressure-generating arc shouid not be as long as the gap for the interrupting arc. Other- Wise, damagingly high arc-generated oil vapor pressures may occur in the casing. Thus, an optimum gap is obtained for both the interrupting arc and the pressure-generating arc with a minimum of travel of the moving parts with the result that mechanical inertia forces are minimized.

Different relative and variable speeds of movement of tbe ends of the contact member 5 may be achieved by changing the angle and shape of the slots 35. An angle nearer to the horizontal would increase the diierence in relative speeds, While a steeper angle would correspondingly decrease the difference. And an arcuate shape, for example, would cause the relative speeds to change at different rates at various stations in the descent of contact member 5.

In our invention as described above we have provided a very simple mechanical arrangement whereby different relative speeds of movement and travel distances are provided for the interrupting and pressure-generating breaks respectively of an interrupter. Moreover, these breaks are positioned advantageously near opposite walls of a common enclosing casing so that tbe widest separation distance between these breaks is afforded within a Pasing of given internal diameter. Accordingly, with the new pivotal arcing contact structure of our invention. we provide a more simple. eiiicient, dependable, and less expensive circuit interrupter of the series-break liquid-blast type than heretofore known.

It should be understood that our invention is not limited to the speciiic details of construction and arrangement thereof herein illustrated, and that changes and modiiications may occur to one skilled in the art without departing from the spirit thereof.

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

1. An electric circuit interrupter comprising an arc-extinguishing liquid, an insulating casing forming a pressure-confining chamber immersed in said liquid, a container for said liquid, relatively movable contact structure mounted within said chamber adapted to separate in said liquid to form a pressure-generating break and an interrupting break in series in the circuit, said structure including a movable bridging contact member and fixed coacting contacts, said casing having an exhaust port adjacent to said interrupting break and arranged to exhaust an arcgenerated vapor pressure within said chamber to cause arc-extinguishing liquid to interrupt the arc at said interrupting break, operating means for imparting a translational movement to said contact member and guide means for imparting a positive rotational movement to said contact member which is in connection with, and in denite relation to, said translational movement whereby said interrupting break increases faster than said pressure-generating break.

2. An electric circuit interrupter comprising an arc-extinguishing liquid, an insulating casing forming a pressure-confining chamber immersed in said liquid, a container for said liquid, relatively movable contact structure mounted within said chamber adapted to separate in said liquid to form a pressure-generating break and an interrupting break in series in the circuit and including a pivoted contact member and xed coacting contacts, said casing having an exhaust port adjacent to said interrupting break, an 0perating carriage for moving said pivoted contact member, said contact member including a pivotal connection to said operating carriage and a pivotal connection to said casing, said pivotal connection to said operating carriage including a slot aligned in a direction parallel to the direction of movement of said operating carriage, and said pivotal connection to said casing including a slot aligned at an angle to the movement of said operating carriage and thereby adapted to induce a positive progressive rotational movement in addition to the usual translational movement of said contact member as said circuit interrupter opens such that said interrupting break is longer than said pressure-generating break.

3. An electric circuit interrupter comprising an arc-extinguishing liquid, an insnlating casing forming a pressure-confining chamber immersed in said liquid, a container for said liquid, relativeiy movable contact structure mounted within said chamber adapted to separate in said liquid to form a pressure-generating break and an interrupting break in series in the circuit and including a pivoted contact member and fixed coacting contacts, said casing having exhaust ports adiacent said interrupting break, an operating carriage for moving said pivoted contact member including positive means for effecting opening movement of said contact member and a reslient connection from said carriage to said contact member for assuring an adequate contact pressure, said contact member including a pivotal connection to said operating carriage and a pivotal connection to said casing, said pivotal connection to said operating carriage including a slot aligned in a direction paralel to the direction of movement of said operating carriage, and said pivotal connection to said casing including a slot aligned at an angle to the movement of said operating carriage and thereby adapted to cause said contact member to pronessively assume an angle wth respect to said xed contacts, as said circuit interrnpter opens, which is different from the contact member angle when the interrupter is in the closed position such that said interrupting break is longer than said pressure-generating break.

4. An electric circuit interrupter of the uid blast type comprising an arc-extinguishing liquid, an insulating casing forming a Apressure-comining chamber immersed in said liquid, a container for said liquid, relatively movable contact structure mounted Within said chamber adaptedfor separation to form a pair of series breaks in the interrupting circuit, an expulsion port through said casing wall arranged adjacent to at least one of said breaks, said contact structure including a rockable bridging contact for producing one of said breaks at either end thereof, operating means for moving said bridging contact into and out of contact-making engagement, a pivotal connection between said bridging Contact and said operating means, and cam means associated IISA with said bridging `contact for controlling the degree and rate of rocking thereof during a crcuit opening operation whereby to produce dissimilar breaks in said interrupting circuit.

WILFRED F. SKEATS. THELLWELL R. COGGESHALL.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS

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