US2420888A - Oil circuit interrupter - Google Patents

Description

May 20, 1947. w. M. LEEDS I OIL CIRCUIT INTERRUPTER Filed April 2, 1943 2 Sheets-$heet l fig. 1.

WETNESSES: I

INVENTOR IA/Z'UZ/Zmp M [4660 5.

BY 9\/ o ATM y 0, 1947. w. M. LEEDS 2,420,888

OIL CIRCUIT INTERRUPTER Filed April 2, 1945 2 Sheets-$heet 2 III WITNESSES: 2 1 INVENTOR 18 f5 16' MHZ/7P0; M Leeds.

Patented May 20, 1947 OIL CIRCUIT INTERRUPTER Winthrop M. Leeds, Wilkinsburg, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application April 2, 1943, Serial No. 481,529

6 Claims.

This invention relates to circuit interrupters in general and, more particularly, to circuit interrupters of the type which effect are extinction by a flow of are extinguishing fluid.

More specifically, it is an object of my invention to provide an improved circuit interrupter in which a movable contact cooperates with a relatively stationary contact to establish an arc. I associate a fluid moving means with the stationary contact to assist in low current interruption, and I charge the fluid moving means by movement of the movable contact.

Another object is to provide an annular piston movable relative to a stationary contact in a circuit interrupter and to charge the piston during the closing operation by the closing movement of the movable contact.

My invention is especially suitable for use in circuit breakers of the type which draw both a pressure generating arc and an interrupting arc, and which direct fluid under pressure from the pressure generating arc toward the interrupting arc to effect the latters extinction. I have found that high speed oil circuit interrupters using a series connected pressure generating arc to provide the energy for driving oil into the main interrupting break need a mechanically driven piston to supply the necessary oil fiow during the interruption of low currents when the self generated pressure produced at the pressure generating arc is inadequate for high speed interrupting action.

I have found it desirable to associate an auxiliary spring driven piston with the intermediate contact because this type of construction results in the most advantages from the point of view of compactness in design and close proximity of the oil driving piston to the are being interrupted.

' A distinct advantage of my invention is the fact that the intermediate or relatively stationary contact need not travel at least the distance of the piston travel, and consequently, the arcing gap opened by the main moving contact is not shortened by motion of the intermediate or stationary contact moving with the piston. In my invention I permit movement of the piston relative to the intermediate or stationary contact. Consequently, the main interrupting gap is not shortened and high speed operation is facilitated.

My invention has peculiar advantages as applied to circuit interrupters having an interrupting time from the tripping of the operating mechanism to the time of arc extinction of only three cycles. In such fast circuit interrupters it is particularly desirable that the main contact gap is not shortened because of movement of the intermediate or relatively stationary contact with the piston.

Another object of my invention is to provide a passage through the intermediate or stationary contact of an interrupter which cooperates with an annular piston which I dispose in surrounding relation with respect to the intermediate or stationary contact. Preferably the piston itself has an orifice which cooperates with the passages through the stationary contact to facilitate are extinction.

Another object of my invention is to provide an improved circuit interrupter of the type which draws at least two arcs in series, and to provide an improved intermediate contact construction which facilitates ready removal and inspection of the intermediate contact.

Another object is to provide an improved circuit interrupter of the type drawing both a pressure generating arc and an interrupting arc with improved venting means for cooling the intermediate contact.

Another object is to provide an improved circuit interrupter of such construction that operation of the breaker without load serves to flush out the arcing chamber.

Another object is to provide an improved circuit interrupter in which a pair of contacts cooperate to establish an are. I dispose piston means in surrounding relation with one of the contacts and movable relative thereto, and I charge the piston means by the closing movement of the other cooperable contact.

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

Figure 1 is an elevational view, partially in section, of a circuit interrupter embodying my invention and shown in the closed circuit position;

Fig. 2 is an enlarged vertical section of one of the arc extinguishing units shown in Fig. l, the unit being shown in the closed circuit position;

Fig. 3 is a View similar to Fig. 2 but showing the disposition of the several parts during a circuit opening operation;

Fig. 4 is a fragmentary enlarged vertical sectional view taken on the line IV-IV of Fig. 2;

Fig. 5 is an inverted plan view in section taken on the line VV of Fig. 2; and

Fig. 6 is a plan view in cross-section taken on the line VI-VI of Fig. 2.

Referring to the drawings, and more particu- 3 larly to Fig. 1, the reference numeral I 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 l are insulating bushings 5 which enclose terminal studs 5. Threadedly secured on the terminal studs 6 and clamped thereto are contact feet 1, which support are extinguishing units generally designated by the reference numeral 8.

Referring more particularly to Fig. 2 it Will be observed that the arc extinguishing unit 8 comprises a top dome casting 9 which forms a pressure generating chamber generally designated by the reference numeral 10. Disposed within the pressure generating chamber I is a pressure generating contact II pivotally mounted at I2 and cooperable with a relatively stationary or intermediate contact I3 to draw a pressure generating are designated by the reference numeral 14 in Fig. 3.

Also cooperable with the intermediate or stationary contact I3 is a movable contact I constituting the opposed outer ends of a conducting cross-bar I5. Referring to Fig. 3 it will be noted that the movable contact I5 cooperates with the relatively stationary contact I3 to draw an interrupting are designated by the reference numeral I? in Fig. 3. The are extinguishing unit 8 comprises a plurality of suitably shaped insulating plates secured in position by insulating tie rods IS. The upper insulating plate 45 has a cylindrical bore therein for slidably receiving the stationary contact it. Contact I3 is provided with a flanged upper portion which engages the plate 45 and thereby positions the contact with respect to the plate when the contact structure is in the open circuit position. The insulating plates form two vertical flow passages generally designated by the reference numeral I9, which communicate at their upper end with the pressure generating chamber I8, and which communicate at their lower end with a plurality of inlet passages designated by the reference numeral 28 and shown more clearly in Figs. 2 and 6. The arc extinguishing fluid, in this instance oil, which is forced downwardly from the pressure generating chamher It through the vertical flow passages I9 and through the inlet passage 20 strikes the interrupting are I; and passes through orifices 23 in insulating orifice plates 23a to exhaust through exhaust passages designated by the reference numeral 2! and shown more clearly in Figs. 4 and 6.

The pressure generating contact II is actuated by an insulating operating rod 24 which is guided in an aperture 25 provided in the bottom metallic plate 26 of the arc extinguishing unit 8. A compression spring 2'! is disposed between the bottom plate 28 and a head 28 integrally formed with the operating rod 24. Consequently, the compression spring 21 biases the operating rod 24 in a downward direction as viewed in Fig. 2. Integrally formed with the operating rod 24 is a flange 29 which serves as a lower seat for a compression spring 38. The upper end of the compression spring 38 abuts against a washer 3| which is slidable on the operating rod 24. The washer 31 engages in abutting relation two actuating arms 32, only one of which is shown. The actuating arms 32 serve to externally actuate the pressure generating contact II about the pivot 2. The actuating arms 32 are formed with relatively wide apertures 33, through which extends a pin 34 rigidly secured to and movable with the operating rod 24.

A flexible conducting strap 36 is secured by a screw to one of the actuating arms 32 and at its other end to the top dome casting 9. Consequently, the pivot I2 does not need to carry the breaker current. The conducting cross-bar I5 is reciprocally actuated in a vertical direction, as viewed in Fig. 1, by an insulating operating rod 22, In the closed circuit position of the interrupter as shown in Figs. 1, 2 and 4 the electrical circuit therethrough comprises the lefthand terminal stud 6, left-hand contact foot T, top dome casting 9, conducting strap 36, actuating arm 32, pressure generating contact I I, relatively stationary or intermediate contact I3, lower movable contact I5, conducting cross-bar I6, through the right-hand arc extinguishing unit 8 in a simila-r manner to the right-hand terminal stud 5.

When it is desired to open the electrical circuit passing through the interrupter, or in response to overload conditions existing in the circuit con-- trolled by the interrupter, suitable mechanism, not shown, is actuated to cause downward movement of the insulating operating rod 22. The downward movement of the insulating operating rod 22 causes downward movement of the movable contact I5. Since the compression spring 21 biases the operating rod 24 in a downward direction, the operating rod 24 will follow the downward movement of the conducting cross-bar IE to cause a clockwise rotation of the pressure generating COYltfiCt II about the pivot I2. The movable contact I5 separates from the stationary contact I3 at substantially the same time that the pressure generating contact II separates from the stationary contact I3 to result in a substantially simultaneous drawing of both a pressure generating arc I4 and an interrupting are I "I, as shown more clearly in Fig. 3.

If the current through the interrupter is high, the pressure formed at the pressure generating arc I4 will correspondingly be high. If, however, the current being interrupted is low the pressure formed at the pressure generating arc I4 will also be low, and it will, therefore, be dinicult to provide the requisite amount of fluid under the desired pressure to flow through the vertical flow passages I9, through the inlet passages 28 and toward the interrupting are I! to effect the latters extinction.

To assist in the interruption of low currents through the arc extinguishing unit 8, I provide an annular piston member 4I substantially surrounding the intermediate or stationary contact I3 and shown more clearly in Figs. 2, 4 and 5. The piston member 4! has an aperture 42 formed therein which accommodates movement of the piston 4I relative to the stationary contact I3. The aperture 42 provided in the piston 4| contains an annular recess 43, the purpose for which will appear more clearly hereinafter.

A compression spring 44 biases the piston II in a downward direction, having as its lower seat the piston 4| and havin as its upper seat the top insulating plate 45 of the arc extinguishing unit 8. It will be observed that a passage 41 is provided in the stationary contact I 3 which communicates with a transversely extending passage 48 also formed in the intermediate contact I3. The region back of the piston 4|, generally designated by the reference numeral 49, communicates through the vents 50 (see Figs. 4 and 5) to the region exterior of the arc extinguishing unit 8.

During the interruption of low currents through the interrupter, when the pressure created at the pressure generating arc I4 is low, the compression spring 44 will force the piston 4| downwardly to drive the oil in the region below the piston 4| downward and through the exhaust passages 2|. Also some of the oil displaced in the region 5| by the downward movement of the piston 4| will move upward through the aperture 42 provided in the piston 4| and through the passage 41, passage 48 to the vents 59 (see Fig. 4) Thus the passages 41 and 48 also serve as a by-pass around the piston 4| to provide greater freedom of action.

Consequently, the construction which I disclose is operable not only to force oil downward through the exhaust passages 2|, but is also operable to drive oil upward through the aperture 42 and through the stationary contact I3 itself. The annular recess 43 provided in the piston 4| serves to increase the turbulence during the downward movement of the piston 4| thereby enhancing arc extinction, and also increases the insulation surface of the aperture 42 to minimize the possibility of insulation breakdown through the aperture 42 due to carbonization of the insulation surfaces.

It will be observed that during the closing operation that the movable contact |5 charges or raises the piston 4| to substantially the fully charged position before the movable contact l5 causes final closed circuit contact engagement, thereby placing the piston in readiness to force fiuid toward the interrupting arc during a, subsequent opening operation even if such operation is required immediately upon closing the interrupter on a fault or a heavy overload. Consequently, durin the opening operation the piston 4| can move downwardly independently of the stationary contact l3 at a speed solely dependent on its driving spring 44 and the resistance to the fiow of the oil displaced from the region 5|.

Strictly speaking, any downward movement of the intermediate contact [3 would tend to shorten the main gap and hence defeat one of the purposes of the invention, that is, to rapidly form the pressure and interrupting gaps, this being a fast three-cycle breaker. However, it is necessary to permit a slight upward movement of the intermediate contact I3 to enable the compression sprin 36 to furnish the contact pressure not only between the intermediate contact [3 and the movable contact l5, but also between the intermediate contact l3 and the pressure generating contact II.

t is apparent that, should the intermediate contact l3 be fixedly held in a fixed position, with the construction shown, two compression springs would be required for furnishing the proper contact pressure between the contacts I5, and the intermediate contact |3. But with the construction utilized, by permitting the slight upward movement of the intermediate contact l3, a single compression spring 30 suifices to provide contact pressure between the several contacts. It will be observed that the travel of the intermediate contact is is so slight as to inappreciably shorten the main interrupting gap during the opening operation. This construction, therefore, does not permit the main contact gap to be shortened by movement of the stationary contact it with the piston 4|. The result is a constantly rapidly increasing contact gap separation not only for the pressure enerating are H, but also for the main interrupting are H. Thus the use of this construction is particularly desirable in fast three cycle breakers, where the contact gap must be increased very rapidly to prevent reignition of the extinguished are after a current zero.

It will be noted that the passage 41 provided in the stationary contact |3 together with the transversely extending passage 48 permits a ventilation of the intermediate or stationary contact l3 in the closed circuit position of the interrupter. This is especially desirable when the interrupter is carrying heavy load currents continuously for at this time the intermediate or stationary contact I3 is the hottest part of the interrupter. facilitate ventilation of the intermediate contact I3 but relieve back-pressure on the piston 4| to allow free operation of the iston 4| both during opening and also during the closing operations.

I provide a removable inspection plate 39 covering an opening in the top dome casting 9 to permit an operator to view the interior of the pressure generating chamber l0 and inspect the contacts without disassembling the arc extinguishing unit 8. This has an additional advantage because with the construction shown the intermediate or stationary contact i3 may be removed from the unit 8 through the opening covered by the inspection plate 39 without disassembling any of the parts of the arc extinguishing unit 8.

I also provide a check valve 31 which closes apertures 38 formed in the top dome casting 9 during conditions of high pressure within the pressure generating chamber l0. Consequently, after a circuit opening operation accumulated gas within the pressure generating chamber l0 may escape out through the apertures 38 upon a lowering of the check valve 31. The check valve 3? also cooperates with the piston 4| to result in a complete flushing of the unit 8 during an opera tion of the interrupter when the interrupter is not carrying current. This results since on the closing stroke the moving contact l5 has only a slight clearance through the orifices 23 thus eliectively closing the vents 2|, and oil is drawn in only through the check valve 31 by the suction action caused by the upward movement of the piston 4!. It will be noted that as the moving contact l5 raises the piston 4| the moving contact i5 also effectively closes the passage 41 in the intermediate contact |3. Thus with the passage 41 and vents 2| effectively closed, the only entrance for the oil is through the apertures 33 associated with the check valve 31.-

During the opening operation, with no load current passing through the interrupter, the piston 4| will move downward to result in a closing of the check valve 31 and a forcing of oil through the exhaust passages 2| and the vents 50 to result in a flushing of the arc extinguishing 'unit 8.

In the particular embodiment of my invention shown in the drawings the intermediate or sta-- tionary contact I3 is moved slightly upward by the movable contact I5 in the closed circuit position of the interrupter as clearly shown in Fig. 2. Consequently, the compression spring 35 provides the requisite contact pressure not only between the pressure generating contact l and the intermediate or stationary contact |3. but also between the intermediate contact l3 and the lower movable contact l5. During the opening operation the movable contact |5 and the oper ating rod 24 initially move down together, thus resulting in the intermediate contact l3 follow-- ing .the initial downward movement of the movable contact l5. Meanwhile the compression spring 30 maintains the pressure generating con- Also the vents 50 not only serve to.

tact H in abutting engagement with the intermediate contact I 3 until the pin 34 strikes the bottom of the apertures 33. When this occurs, the actuating arms 32 are positively driven downward by the pin 34, and substantially at this same time the movable contact l5 separates from the intermediate contact l3. Consequently, the pressure generating arc l4 and the interrupting are H are both formed substantially simultaneously. This provides a very fast rate of contact separation which is necessary for three cycle breakers.

The following table indicates the marked improvement on arcing time as a result of using a piston as compared with interrupting without use of a piston. All of the data was taken on a 33 kv. circuit with a normal frequency of 60 cycles and using only one unit 8 electrically connected in the circuit, the second unit 8 being shunted It will be apparent from an examination of the above table that the performance of the interrupter was greatly improved by using a piston associated with the stationary or intermediate contact 13.

Certain features of the oil passages, inlet passages and exhaust passages together with certain features of the contact pressure mechanism herein described is disclosed and broadly claimed in a patent application by Leon H. Ludwig, Benjamin P. Baker and Winthrop M. Leeds, Serial No. 465,244, filed November 11, 1942, entitled Circuit interrupters and assigned to the assignee of the instant application.

It will be apparent from the above disclosure that I have provided a novel piston arrangement especially suitable for high speed breakers which require rapid contact separation. If the arcing current is high, the pressure created at the pressure generating are 14 will correspondingly be high and the piston 4i may be prevented by the high pressure from moving downward. In this event, however, a piston would not be necessary to obtain rapid arc extinction because of the high pressure already provided at the pressure generating arc I4. If, however, the arcing current is low, the piston M will move downward to cooperate with the pressure generating arc 14 to effect rapid extinction of the interrupting are 11. During low currents the flow from the piston will tend to predominate over the now created by the pressure generating arc. It will be apparent that with the piston construction disclosed the lower part or" the piston 4| may be used as an orifice with a portion of the oil flowing through the orifice 42, through the intermediate contact [3 itself to exhaust through the vents 50.

Although I have shown and described a particular 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 by those skilled in the art without departing from the spirit and scope of the appended claims.

I claim as my invention:

1. In a circuit interrupter, a pressure-generating contact cooperable with a relatively stationary contact to establish a pressure-generating are, a movable contact arranged to make abutting engagement with the stationary contact in the closed circuit position and separable therefrom during circuit opening to establish an interrupting arc, a piston member substantially surrounding the relatively stationary contact and movable relative to said stationary contact, spring means biasing the piston member in a direction to move fluid under pressure toward said interrupting arc to facilitate arc extinction, said movable contact having a shoulder portion which engages the piston member during the closing stroke to charge the same against the biasing action exerted by the spring means before the movable contact strikes the stationary contact in abutting engagement, and passage means provided in the relatively stationary contact for causing a flow oi fluid from the forward to the back side of said piston to facilitate piston movement during the opening operation and extinction of the interrupting arc, said passage means also providing a vent for the circulation therethrough of fluid when said interrupter is in the closed position for cooling said stationary contact.

2. In a circuit interrupter of the fiuid immersed type, contact means including a substantially stationary intermediate contact for establishing a pressure generating arc and an interrupting arc, said arcs each having a terminal on opposite ends of said intermediate contact, said pressure generating are causing a how of fluid against said interrupting arc to assist in extinguishing the latter, an annular piston surrounding said intermediate contact and mounted for relative movement with respect to said contact, resilient means for biasing said piston in a direction to cause an additional flow of fluid against said interrupting are, means permitting the movement 01": said annular piston beyond the interrupting arc terminal end of said intermediate contact during an opening operation to cause said piston to envelope a portion of said interrupting arc and assist in extinguishing the same, and means intercoimecting said contact means and said piston during a closing movement of said contact means whereby said contact means moves said piston against the biasing action of said resilient means to substantially charge the latter prior to the final closing movement of said contact means.

3. A circuit interrupter of the fluid immersed type comprising a relatively stationary contact member having a pair of arcing tips thereon, a movable contact cooperable with one of said arcing tips to establish a pressure generating arc, a second movable contact cooperable with the other of said arcing tips to establish an interrupting arc, means for simultaneously operating said first and said second movable contacts to substantially simultaneously establish said pressure generating and said interrupting arcs, said pressure generating are causing fluid under pressure to be moved towards said interrupting arc to assist in extinguishing the latter, a hollow piston surrounding said stationary contact and arranged for reciprocating movement with respect to said stationary contact, spring means for moving said piston in a direction to force fluid under pressure toward said interrupting arc in response to an opening movement of said movable contacts, guide means for said piston arranged to arrest motion of said piston at a point beyond the interrupting arcing tip of said contact member, said piston during the circuit opening operation restricting the arcing space adjacent the arcing tip of said contact member to assist in extinguishing said interrupting arc, and means associated with said second movable contact for engaging said piston during a closing movement of said movable contacts to move said piston in the opposite direction and substantially charge said spring before said movable contacts make final engagement with their respective arcing tips.

4. In a circuit interrupter of the liquid immersed type, means defining a pressure chamber, means defining an interrupting chamber adjacent to said pressure chamber, a relatively stationary contact extending between said chambers, a movable contact operable in said pressure chamber and arranged to coact with said stationary contact to establish a pressure generating arc, a second movable contact operable in said interrupting chamber and arranged to coact with said stationary contact to establish an interrupting arc, means for simultaneously operating said movable contacts to open circuit position to establish said arcs, passage defining means for di recting liquid under pressure from said pressure chamber toward said interrupting arc, a piston slidably disposed about said stationary contact and movable relative to said stationary contact, a spring for moving said piston in a direction to force an additional quantity of liquid toward said interrupting arc, said piston having an inner annular recess for increasing the fluid turbulence adjacent the end of said stationary contact during a circuit opening operation to assist extinguishing said interrupting arc, and means arresting movement of said piston at a point beyond the end of said stationary contact during the opening movement of said movable contacts, said piston and said second movable contact having mutually engageable surfaces adapted to be brought together during movement of said movable contacts to closed position to move said piston against said spring to substantially fully charge the same prior to the final closing movement of said movable contacts.

5. A circuit interrupter of the liquid immersed type comprising means defining a pressure chamber, a cylinder having a closed end adjacent to said pressure chamber, the other end of said cylinder being substantially open, a stationary contact extending from said pressure chamber into said cylinder through the closed end thereof, a movable pressure generating contact in said pressure generating chamber arranged to coact with said stationary contact for establishing a pressure generating arc, an interrupting contact movable through the open end of said cylinder and cooperable with said stationary contact for establishing an interrupting arc, means defining liquid flow passages leading from said pressure chamber to said interrupting arc whereby the pressure created by said pressure generating arc forces liquid into engagement with said interrupting arc to assist in extinguishing the latter, an annular piston within said cylinder slidably disposed about said stationary contact and movable relative to said stationary contact, a spring arranged between the closed end of said cylinder and said piston for moving said piston in accordance with an opening movement of said interrupting contact toward the open end of said cylinder to force an additional quantity of liquid into the region of said interrupting arc, stop means adjacent the open end of said cylinder for arresting motion of said annular piston at a point beyond the end of said stationary contact to provide when thus positioned a restricted arcing space adjacent said stationary contact, means venting the closed end of said cylinder exteriorly of said pressure chamber, and passage means through said stationary contact providing a by-pass around said piston to facilitate piston movement, said passage means communicating with said venting means to enhance liquid flow through said stationary contact during a circuit opening operation to assist in extinguishing said interrupting arc and for cooling the stationary contact when the interrupter is in the closed position.

6. In a circuit interrupter, an arc extinguishing unit comprising a housing forming a pressure generating chamber and having an access opening therein, covering means releasably secured to said housing for normally closing said opening, means defining an interrupting chamber disposed below said pressure chamber, a normally stationary rod-like contact extending between said chambers, a movable contact operable in said pressure chamber and arranged to coact with the upper end of said stationary contact to establish a pressure generating break, a second movable contact operable in said interrupting chamber and arranged to coact with the lower end of said stationary contact to establish an interrupting break, support means between said chambers having a cylindrical bore therein for slidably receiving said stationary contact, and means coacting with said support means whereby said stationary contact is held against movement in a downward direction beyond a predetermined point, said stationary contact being freely slidable out of said cylindrical bore and being removable through said pressure chamber and through said access opening when said first movable contact is in the open position whereby said stationary contact can be removed without disassembling the unit.

WINTHROP M. LEEDS.

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

UNITED STATES PATENTS Number Name Date 1,760,529 Schwennker May 27, 1930 2,061,301 Duffing Nov. 17, 1936 2,147,497 Prince et a1 Feb. 14, 1939 2,235,901 Ronnberg Mar. 25, 1941 2,292,547 Sadler Aug. 11, 1942 1,918,151 Turnpenny et a1. July 11, 1933 2,273,545 Von Valkenburg Feb. 1'7, 1942 1,892,098 Ross Dec. 27, 1932 287,532 Goddard Oct. 30, 1883 2,095,441 Howe Oct. 12, 1937 2,145,706 Brann Jan. 31, 1939 2,372,589 Leeds et a1 Mar. 27, 1945

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