US2769067A - Circuit interrupter - Google Patents

Description

Oct. 30, 1956 P. BAKER 2,769,067

CIRCUIT INTERRUPTER Filed Nov. 29, 1952 2 Sheet-sSheeL l WITNESSES: IINVENTOR diyl ahg. Benjamin P.Boker.

Oct; 30, 1956 B. P. BAKER 2,769,067

CIRCUIT INTERRUPTER Filed NOV. 29, 1952 2 Sheets-Sheet 2 Fig.3

INVENTOR Benjamin P. Baker.

United States Patent-' CIRCUIT INTERRUPTER Application November 29, 1952, Serial No. 323,246

8 Claims. (11. 200-150 This invention relates to circuit interrupters, in general, and, more particularly, to arc-extinguishing structures therefor.

In interrupters for interrupting relatively high-voltage circuits, a certain main-contact separation distance and a certain pressure-generating-contact separation distance are required for reliable operation over the entire current range. It has been found that for low and medium values of current, a long pressure-generating arc is required with a relatively short interrupting gap. However, when the current reaches extremely high values, the voltsper-inch of interrupting capacity in the interrupting gap has been found to decrease, thus requiring a longer maincontact separation. Moreover, at these higher values of current, the pressure generated becomes excessive, and the long pressure are becomes a hazard. In the very high voltage range above 230 kv. where complicated multiinterrupters in series are sometimes used, it is desirable to find some simpler mechanical means to obtain greater contact separations in the short time allotted to interrupting period.

It is a general object of my invention to solve the foregoing problem, and I propose improving the interrupting performance of a circuit interrupter throughout the entire current range, even at the very high voltages, by associating a piston with the intermediate contact, which will automatically shorten the pressure-generating gap at the higher current values during high current interruptions, and will automatically, at the same time, increase the interrupting gap, thereby allowing a greater voltage to be interrupted at this interrupting gap.

A more specific object is to provide an improved circuit interrupter of the type having pressure-generating, intermediate and interrupting contacts in which a piston, spring-biased toward the interrupting gap, is associated with the intermediate contact, so that during the interrupting of high values of current, the pressure gap will be shortened while the interrupting gap will be automatically lengthened.

A further object is to provide a liquid-break circuit interrupter of the multi-orifice type in which the intermediate contact is piston-controlled, so that during high currents a greater number of orifices will be utilized for the interrupting operation, whereas the pressure-generating gap will be shortened to prevent the attainment of excessive pressures.

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

Figure l is a side elevational view, partially in vertical section, and partially fragmentary, of a circuit interrupter embodying my invention and shown in the closed circuit position;

. Fig. 2 is an enlarged fragmentary vertical sectional view through the left-hand arc-extinguishing unit of the interrupter illustrated in Fig. l, the contact structure being shown in the closed-circuit position;

Fig. 3 is a view similar to that shown in Fig. 2, but

depicting the state of affairs during relatively low-currentinterruption;

Fig. 4 is a view similar to that of Figs. 2 and 3 but indicating the position of the several parts during a high-' current interruption, when the intermediate contact has been raised by piston action; and

Figs. 5-7 are sectional views taken along, respectively, V-V, Vl-Vl and VII-VII of Fig. 2, looking in the direction of the arrows.

Referring to the drawings, and more particularly to Fig. 1 thereof, the reference character 1 designates a tank filled to the level 2 with a suitable arc-extinguishing fluid 3, in this instance circuit-breaker oil.

Depending from the cover 4 of the tank 1 are a pair of terminal bushings 5, 6, to the lower ends of which are respectively appended arc-extinguishing units, generally designated by the reference characters 7, 8. Electrically interconnecting the extinguishing units 7, 8 in the closed-circuit position, as shown in Fig. l, is a conducting bridging member 9, vertically actuated in a reciprocal manner by an insulating lift rod 10. The lift rod 10 is actuated by a suitable mechanism, which forms no part of my invention.

Referring more particularly to Fig. 2 of the drawings, it will be observed that a contact foot 12, clamped to the lower end of the terminal bushing 5, supports a topdome casting 13, which provides a pressure-generating chamber, generally designated by the reference character 14.

Pivotally mounted within the pressure chamber 14 is a rotatable pressure-generating contact 16, pivotally mounted at 17, and having a pair of externally-actuated arms 18, only one of which is shown in Fig. 2. An insulating operating rod 20 has a pin 21 passing therethrough, at the upper end thereof, the outer ends of the pin 21 passing through enlarged apertures 22 provided at the extremities of the actuating arms 18. Rigidly fixed to the rod 20 is a spring seat 23, serving as a lower seat for a contact compression spring 24, the upper end of which bears against a washer 25 slidable upon the upper end of the rod 20.

The lower end of the rod 20 is spring-biased downwardly in an opening direction by a compression spring 26, which is disposed between a head 27 and the lower plate 28 of the unit 7. The cross-bar, or bridging member 9, strikes the head 27 and raises the rod 20 during the closing operation, thereby rotating the pressure-generating contact 16 in a counterclockwise direction about the pivot point 17.

The extremities of the cross-bar 9 extend upwardly, as shown, to form a pair of movable interrupting contacts 29. The interrupting contacts 29 make conducting engagement with an intermediate contact 30, the upper end of which is engaged by the contact portion 31 of the rotatable pressure-generating contact 16.

Thus, in the closed-circuit position of the interrupter, as shown by the full lines in Figs. 1 and 2, the circuit therethrough includes the terminal stud extending through the terminal bushing 5, adapter 12, flexible strap 32, pressure-generating contact 16, intermediate contact 30, and lower movable interrupting contact 29. The circuit then extends through the conducting cross-bar 9, and through the right-hand extinguishing unit 8 in an identical manner, to the right-hand terminal stud, not shown, extending upwardly interiorly within the right-hand terminal bushing 6.

During the opening operation, suitable means not shown, causes downward opening motion of the insulating lift rod 10 and the conducting bridging member 9. This causes separation between the interrupting and intermediate contacts 29, 30 and also permits the compression spring 26 to move the rod 20 downwardly, first taking up the contact compression by expansion of the spring 24, until the pin 21 strikes the lower sides of the apertures 22 in arms 18, and thereafter eltects opening rotative clockwise motion-of the pressure-generating contact 16 upwardly away from the intermediate contact 30 to establish a pressure-generating arc 34, more clearly shown in Figs. 3 and 4 of the drawings.

The interrupting are 35, shown in Figs. 3 and 4, is established between the intermediate contact 31? and the lower movable interrupting contact 29. It is established within an interrupting chamber 36 composed of a plu rality of orifice sections 37. Each orifice section 37 includes at least one plate 38 (Fig. having a cut-out portion 39 forming a pair of inlet passages 40. Thus oil may pass downwardly through the two vertical-flow passages 41 from the pressure-generating chamber I14 and pass inwardly through the two or more inlet passages 40 toward the interrupting are 35. The oil may then pass through orifices 42 provided by a plurality of orifice plates 43, and then pass out of the interrupting units 7, 8 through diametrically-opposed venting passages 44, more clearly shown in Fig. 6 of the drawings. The two venting passages 44 are provided by the lateral separation between a pair of cooperating half-plates 45 spaced apart, and disposed upon insulating tie-rods 46 which extend through all of the other plates.

From the foregoing, it will be apparent that each orifice section 37 includes at least one inletplate 38, two orifice plates 43 and a venting plate 47, the latter including two of the half-plates 45.

Interruption of the interrupting arc 35 soon follows, and the cross-arm 9 moves downwardly to the dotted line position 48 of Fig. 1, withdrawing the two movable interrupting contacts 29 out of the arc-extinguishing units 7, 8, and introducing two isolating gaps into the circuit.

During the closing operation, the cross-bar 9 raises and strikes the head 27 or" the operating rod 29, moving the same upwardly to thereby efiect closing rotative motion of the pressure-generating contact 16 so that the latter strikes the intermediate contact at substantially the same time that the interrupting contact 29 strikes the same, the compression of the compression spring 24 providing the requisite contact pressure between the several contacts.

Slidably surrounding the intermediate contact 30 is an apertured plate-like piston member 49 movable within a piston chamber 50. The upper end of the piston chamber St) is vented out of the unit 7 by vents 54 shown in Fig. 7 of the drawings. Thus, substantially tank pressure exists at all times on the non-working side of the piston 49.

A compression spring 51 has its lower seat upon the piston 49, and has its upper seat against the insulating plate 52. Disposed on diametrically-opposite sides of the intermediate contact 30 is a pair of actuating lugs 53, the lower ends of which are engaged by the piston 49, when it is moved upwardly under predetermined pressure conditions within the interrupting chamber 36. The upper ends of the actuating lugs 53 form stops for up ward motion the intermediate contact 36, striking the plate 52, thereby limiting the upward travel of the contact 3%, as shown in Fig. 4 of the drawings.

Fig. 2 shows the closed-circuit position of the interrupter with the piston 49 in its lower static position, being biased to this position by the compression spring 51. Fig. 3 shows the position of the several parts during low-current interruption. During such low-current interruption, the pressure generated by the interrupting are is inadequate to cause raising of the piston 49 and intermediate contact 3%) against the biasing action exerted by the compression spring 51. It will be noted that the length M of the pressure-generating are 34 is relatively long, whereas the length s of the interrupting arc is relatively short. However, for such low-current interruptiom-it is desirable to have a long pressuregenerating arc, for the pressure generated at said are 34 is, in part, a function of the length of the pressuregenerating arc. In other words, the longer the pressure-generating arc the more oil length is contacted by the arc, and the greater amount of gasification will take place. Interruption of the interrupting are 35 soon takes place, interruption taking place more easily in the case of a low-current arc than a high-current are by virtue of less amperage in the arc column.

Fig. 4 shot s the state of afliairs at the same moment of the opening stroke as was shown in Fig. 3. However, Fig. 4 indicates the interruption of a highwcurrent arc in which the pressure generated within the interrupting chamber 36 is sufficient to cause raising of the piston 49 and hence the intermediate contact 30 to the position shown, at which the upper ends of the actuating lugs 53 strike the plate 52, thereby halting the upward movement of the same. It will be obvious that this excessive pressure created within the interrupting chamber 36 under high-current conditions is actually the combination of the twopressures created at the arcs 34, 35, each of which in itself would be adequate to effect raising of the piston 49. It will be noted that the length m" of the pressure-generating are 34 is much less than the length M of the pressure-generating are 34 in the low-current interruption state shown in Fig. 3. Also,.it will be noted that the length S of the interrupting are 35 is greater than the length s of the interrupting are 35 in Fig. 3, the latter, of course, indicating the lowcurrent interrupting case.

Consequently, in Fig. 4, indicating the high-currentinterrupting case, the length of the interrupting are 35 has been increased, whereas the length of the pressure-generating are 34 has automatically been reduced. This is a desirable state of atfairs for it prevents the attainment of excessive pressure within the pressuregenerating chamber 14, and at the same time increases the length of the interrupting are 35, thereby subjecting the latter to a greater length of interrupting influence within more multiorifice sections 37, as indicated in Fig. 4.

Not only is the interrupting are 35 subjected to the interrupting action of more orifices, but also this are is very rapidly drawn, since contact 29 moves down as contact 30 moves up.

Multi-orifice interrupters for 230 kv. breakers generally require about 4 /2" of main contact separation and 3" of pressure-generating contact separation for reliable operation over the entire current range. The 3" of pressure gap is easily obtained, but the 4 /2 of main contact separation is about the maximum that can be obtained in three cycles after energizing the tripping device.

Tests on the multi-orifice interrupter indicate that for low and medium values of current, a long pressure are is required with relatively few interrupting orifices. When the current reaches extremely high values, the volts-perorifice decrease, thus requiring a longer main contact separation. However, at higher values of current the pressure generated becomes excessive and the long pressure are becomes a hazard. The automatic reduction in pressure generating gap achieved by my invention acts to relieve these excessive pressures. The interrupting problem is even more difficult in circuit breakers rated above 230 kv. where either complicated multi-interrupters in series are required or some mechanical means must be found for obtaining greater contact separation in three cycles. In my invention I propose using normal breaker speeds and operating means to obtain 4 /2" to 5" of main contact separation and 3" to 3 /2" of pressure gap. These values are obtainable in three cycles and are satisfactory for low and medium values of current at 345 kv. For higher values of current, I propose increasing the main gap approximately 2 /2 and at the same time decreasing the pressure gap the same amount. This is accomplished by using a floating intermediate contact, which is spring biased toward. the main gap. The spring seat on the contact forms a piston which has its lower side exposed to grid pressure and its upper sideto tank pressure. At low values. of current theintermediate contact remains at its lower position, giving sufiicient interrupting gap and a long pressure gap. At high values of current the long pressure gap is formed initially, which produces a'rapid rise in pressure. In response to this pressure, the intermediate contact is forced up, which results in (1) reduced pressure gap, (2) increased interrupting gap, (3) increased number of orifices, inlets and vents, (4) pro duction of some volume under the contact and piston for venting into. These four effects create favorable condition for high current interruption at high voltage and decrease the bursting pressure on the interrupter ports.

Although particular gap lengths and voltages have been specified above, it is to be clearly understood that they were mentioned by way of illustration, and not by way of limitation.

From the foregoing, it will be apparent that I have provided an improved interrupter in which the lengths of the pressure-generating and interrupting arcs are automatically controlled in accordance with the magnitude of the current being interrupted. During high-current interruption, the pressure-generating arc is reduced in length, whereas the interrupting arc is increased in length. During low-current interruption, the pressure-generating arc has a relatively greater length than in the case of highcurrent interruption, and the interrupting arc has a shorter length than in the case of high-current interruption. Because of the less amperage being interrupted, fewer interrupting sections 37 are needed in the interrupting chamber 36 than in the case of high-current interruption.

Although I have shown and described a specific structure, it is to be clearly understood that the same was 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.

I claim as my invention:

1. A circuit interrupter of the fluid-blast type including contact structure separable to establish a pressure-generating arc and a serially-related interrupting are, said contact structure including a movable pressure-generating contact, an intermediate contact and a movable interrupting contact, the pressure-generating contact and the interrupting contact moving in substantially opposite directions away from the intermediate contact to establish said two arcs, and piston means acting upon the intermediate contact responsive to the pressure adjacent the interrupting arc to cause a movement of the intermediate contact toward the pressure-generating contact and hence a shortening of the pressure-generating arc and a consequent lengthening of the interrupting arc during high-current interrupting conditions.

2. A circuit interrupter of the fluid-blast type includable to establish a pressure-generating arc, the intermediate contact and a movable interrupting contact, the pressure-generating and intermediate contacts being cooperable to establish a pressure-generating arc, the intermediate and movable interrupting contacts being cooperable to establish a serially-related interrupting arc, piston means associated with the intermediate contact, means biasing the piston means in the direction of movement of the movable interrupting contact, and actuating means movable with the intermediate contact and engaged by said piston means during the interruption of relatively high current to cause movement of the intermediate contact in the direction of motion of the pressure-generating contact.

3. A circuit interrupter of the liquid-break type includ ing an arc-extinguishing unit immersed in an arc-extinguishing liquid, contact structure operable to establish a pressure-generating arc and a serially related interrupting are, said contact structure including a movable pressure-generating contact, an intermediate contact and a movable interrupting contact, piston means associated with the intermediate contact and responsive to the pressure generated adjacent the interrupting arc, a plurality of interrupting sections spaced along the line of movement of the movable interrupting contact, and the piston means causing motion of the intermediate contact to automatically effect shortening of the pressure-generating arc, lengthening of the interrupting arc, and the application to the interrupting arc of a greater number of interrupting sections than in the case of a low-current interruption.

4. A circuit interrupter of the liquid-break type including an arc-extinguishing unit immersed in an arcextinguishing liquid, contact structure including a movable pressure-generating contact, an intermediate contact, and a movable interrupting contact, piston means associated with the intermediate contact, means biasing said piston means in the direction of motion of the movable interrupting contact, actuating means movable with the intermediate contact and engaged by said piston means to cause movement of the intermediate contact in the direction of motion of the pressure-generating contact during high current interrupting conditions, and a plurality of multi-orifice interrupting sections disposed along the line of motion of the movable interrupting contact.

5. A circuit interrupter of the liquid-break type including an arc-extinguishing unit immersed in an arc-extinguishing liquid, contact structure including movable pressure-generating and interrupting contacts separable in opposite directions away from an intermediate contact, a ring-shaped plate-like piston member loosely surrounding the intermediate contact, spring means biasing the piston member in the direction of movement of the movable interrupting contact, one or more lug portions associated with the intermediate contact and engaged by said piston member during high current interrupting conditions to cause shortening of the pressure-generating arc and automatic lengthening of the interrupting arc.

6. A circuit interrupter of the fluid-blast type including contact structure separable to establish a pressure-generating arc and a serially-related interrupting arc, said contact structure including a movable pressure-generating contact, an intermediate contact and a movable interrupting contact, a plurality of interrupting sections, the intermediate and interrupting contacts meeting in the closed-circuit position of the interrupter at a point intermediate the ends of the plurality of interrupting sections, and piston means associated with the intermediate contact and responsive to the pressure adjacent the interrupting arc to cause a shortening of the pressure-generating arc and a fast lengthening of the interrupting are along the interrupting sections during high-current interrupting conditions.

7. A circuit interrupter of the fluid-blast type including contact structure separable to establish a pressure-generating arc and a serially-related interrupting arc, said contact structure including a movable pressure-generating contact, an intermediate contact and a movable interrupting contact, a plurality of multi-orifice sections, the intermediate and interrupting contacts meeting in the closed circuit position of the interrupter at a point intermediate the ends of the plurality of multi-orifice sections, and piston means associated with the intermediate contact and responsive to the pressure adjacent the interrupting arc to cause a shortening of the pressure-generating arc and a rapid lengthening of the interrupting are through the multi-orifice interrupting sections during high-current interrupting conditions.

8. An arc extinguishing unit immersed in liquid and including a plurality of multi-orfice interrupting sections, a pair of separable contacts meeting in the closed circuit position at a point intermediate the ends of the multiorifice interrupting sections, means for moving one of the contacts to the open-circuit position through at least some of the multi-orifice interrupting sections, and means responsive to the pressure generated at the are established 7 between the ::contacts for moving .the vother of the. contactsaway from said one contact to cause rapid lengthening: of y the arc. through said multi-oriflce interrupting sections,

References Cited ;in the file of this patent UNITED STATES'PATENTS Ludwig et a1. Aug. .27, 1946 -8 ';Baker et a1 ...Dec.' 17, 1946 Leeds May'20, 1947 Strom 'Aug."2,.1949

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