US2749412A

US2749412A - Electric circuit interrupter

Info

Publication number: US2749412A
Application number: US380716A
Authority: US
Inventors: George C Mcbride; Harold N Schneider
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1953-09-17
Filing date: 1953-09-17
Publication date: 1956-06-05
Anticipated expiration: 1973-06-05
Also published as: GB762547A

Description

June 5, 1956 G. c. M BRIDE ETAL ELECTRIC CIRCUIT INTERRUPTER Filed Sept. 17, 1953 w Q W ,/o

. 4 y a .a w a a w J F a a m M 4, Q m a 4 a a a a 5 a w w w M a w M Q a r N M M i 0 M u M 2 W M 9. W I 0 RN: (v 3 n M 2; 2 C 4 v 2 W 2 N 2 v F M a a J 2 m J J Inventors:

L mg i e i m c o M m N Mwd .I rm h or T a H ELECTRIC CIRCUIT INTERRUPTER George C. McBride, Drexel Hill, and Harold N. Schneider, Springfield, Pa, assignors to General Electric Company, a corporation of New York Application September 17, 1953, Serial No. 38%,716

3 Claims. (Cl. 2llll-1 50) This invention relates to electric circuit interrupters for high voltage power circuits and, more particularly, to high speed interrupters of the multiple break type.

The interrupter of the present invention is of the general type shown in Frank Patent No. 2,164,175, assigned to the assignee of the present invention, wherein, for interrupting high voltage power circuits there are provided a plurality of pairs of simultaneously operable interrupting contacts electrically connected in series with a sequentially operable pair of isolating contacts. Although it has been proposed heretofore to use a plurality of conducting rods disposed in parallel spaced relation as the movable interrupting contacts of such amultiple break circuit intrerupter, these conducting rods have in the past been interrelated by complex structure which does not readily lend itself to association with simple and efiicient guide means and stop means for precisely con trolling the movement or the movable contact structure.

An object of this invention is to provide a new and improved movable contact assembly for a circuit interrupter of the multiple break type having parallel spaced-apart movable contacts.

A further object of this invention i to interrelate the spaced-apart parallel contacts of a multiple break circuit interrupter by means of a crosshead which is constructed and arranged so as to readily lend itself to coaction with simple and efficient stop means and guide means for precisely controlling the movement of the contacts.

A further object of this invention is to provide a structurally simple, compact, and sturdy movable contact assembly wherein a common crosshead is utilized as a base for performing the multiple function of supporting the movable interrupter contacts and of supporting the guide means and stop means used to control the movement of the contacts.

Another object of this invention is to provide guide means and stop means coacting in a novel manner with a contact-carrying crosshcad to provide for precisely guided and limited reciprocable motion of said crosshead.

In carrying out our invention in one form, there is provided a multiple break circuit interrupter comprising casing means disposed about a plurality of movable contact rod positioned in parallel spaced-apart relationship. These contact rods are supported from a common reciprocable crosshead which carries elongated tubular guide structure telescopically mating with guide rods supported from the casing means. The tubular guide structure carries an abutment plate which is adapted to engage a yieldable buffer positioned between the bufier plate and the casing means so as to limit separation of the contacts.

The invention will be better understood by considering the following description taken in connection with the accompanying rawing and its scope will be pointed out in the appended claims. 7 Fig. 1 is an elevational View, partly. in cross section, of a circuit interrupter, say of .160 to. 2Q kv., embodying the present invention, certain elements of the guide means nited States Patent and stop means for the movable contacts being broken away for clarity.

Fig. 2 is an elevational view, partly in section taken along the line 22 of Fig. l and illustrating the guide means and stop means for controlling the movement of the interrupter contacts.

Fig. 3 is a view showing a modified form of circuit interrupter.- This view is a cross-sectional view assumed to be taken along a line corresponding to the line 33 of Fig. l.

Fig. 4 shows, diagrammatically, a similar interrupter to that of Fig. l, but having three associated breaks for a higher voltage breaker, on the order say of 330 kv-.

Referring now to the drawing, the interrupting unit 1 shown in Fig. l is adapted to be mounted, along with another similar unit (not shown), inside a relatively large oil-tilled metallic enclosing tank. These two inerrupting units would be electrically connected by a reciprocating blade contact 2, such as shown in greater detail in Fig. l of U. S. Patent 1,548,799 to Hilliard, which is assigned to the same assignee as the present application.

The interrupter unit 1 is supported within the oilfilled tank from an insulating bushing structure 3 having. a conductor stud to which adapter 4 is suitably secured Adapterd is arranged to cooperate with suitable tie bolts (not shown) which structurally in-- in a known manner.

terconnect the interrupter unit 1 and the adapter i.

The interrupter unit comprises an insulating casing 5 enclosing a plurality of pairs 8, 9 of separable interrupt ing contacts which are electrically connected in series. The upper pair 3 or separable contacts comprises a relatively fixed contact assembly 16 and a relatively movable rod-type contact H. The fixed contact assembly it) is preferably of the cluster-type comprising a plurality of' fingers urged radially inwardly by suitable resilient means. In a corresponding manner, the lower pair 9 of contacts. comprises a similar fixed contact assembly 12 and rela-- The pairs of interruptingv contacts 8 and 9 are electrically connected in series by' means of suitable current transfer contacts 14 and the For tively movable contact 13.

transversely-extending contact support casting 15. supporting the movable contacts 11 and 13 and for interrelating them for simultaneous movement so as to draw a plurality of simultaneously occurring arcs, there is provided a common crosshead 16 of conducting material to which the lower rod contact 13 is directly secured and to which the upper rod contact 11 is fixed by means;

of an interconnecting insulating rod 17, preferably of a formed in contact ll.

isolating contacts. From the above description it will be apparent that the electrical circuit through the interrupter is as follows: beginning with adapter 4, current will flow successively through the conductor 20, through the upper interrupting contacts ll ll, through the current transfer contacts 14 and the casting 15, then through the lower interrupting contacts 12, 13, the crosshead 16, the contact button 18, the isolating contact 19, and finally through the switch blade 2 and to the cooperating interrupter (not shown), which is disposed at the opposite end of the switch blade 2. In a known manner, the pairs 8 and 9 of series interrupting contacts are preferably shunted by a high resistance shown schematically at R, so that once the interrupting contacts are separated,.a limited portion of the current flows through the resistance and is sub sequently interrupted by separation of the

isolating contacts

18 and 19, as will appear in greater detail hereinafter.

Adjacent to the serially related interrupting contacts 8 and 9 are a pair of arc-extinguishing

baffle stacks

21 and 22. Bafile stack 21 is formed of a plurality of superposed apertured tbatlle plates 23 which together provide a central interrupting passageway 24 and a plurality of slots 25 radiating therefrom. Baflle stack 21 is generally similar to the baflle stack construction described and claimed in Balentine application Serial No. 337,997, filed February 20, 1953, now Patent No. 2,717,294, dated Sept. 6, 1955, and assigned to the assignee of the present invention, so that when an arc is drawn within the passageway 4 in response to separation of contacts '10 and 7.1, pressure is produced within the oil filled casing and is effective to force a highly concentrated blast of dielectric fluid across the are, through the slots 25, and out the registering exhaust port 26 formed in the adjacent wall of easing 5. This blast action, self-generated as described in the aforesaid Balentine application, in most cases is effective to deionize and extinguish the arc. The lower baflie stack 22 generally corresponds to baffle stack 21 except bafile stack 22 is provided with an opening 27 through which reciprocates the insulating portion of the upper rod contact '11.

On low current operations such as capacitance switching, the low pressure generated by the light current are alone is not always sufiicient to clear the circuit. To overcome this difficulty, there is provided an impulse pump 30, which is effective in response to opening of the breaker to impel a flow of oil transversely across the

bame stacks

21 and 22, e. g., through the slots 31 and '25 in baffle stack 21 and through the slots 31a and a in bafile stack 22. This oil ilow from the pump assures sufiicient blast action to interrupt the circuit in rated time at the low current values and also serves as an eifective scavenging means for the interrupter after high current interruptions.

The pump 3-5 comprises a cylinder 32 suitably secured to the interrupter casing as by a clamping ring and screws 34 at its upper end and by the supporting casting 3'7 with screws 38 at its lower end. The pump cylinder 32 communicates with the battle stacks 21 and 22 through a pair of

passageways

43 and 43a provided by pairs of registering openings formed in casing '5 and cylinder 32. For controlling the flow of fluid through these passageways there are provided check valves 44 and 44a disposed in the passageways 43 and 430, respectively. These check valves 44 and 440 are adapted to cooperate with metallic valve seats 45 and 45a, respectively, each of which is press fitted into a pair of the aforementioned registering openings in the casing 5 and cylinder 32. The valves are free to slide on their centrally disposed spindles 29 and 2% which are supported from the valve seats by suitable spider structure. These valves freely permit fluid how there through from the pump 3% but, when pressure produced by the are drawn by the contacts 11 and 13 predominates, the valves close automatically to protect the pump from objectionable arc-generated back pressures. Reciprocably mounted within the cylinder 32 is an impulse piston 35 which is spring-biased downwardly by a compression spring 36, which is mounted between the fixed supporting cast" g 37 and a stop 39 fixed to the piston rod 4-0. The pi on 35 is provided with suitable normally-closed check valves 4i which permit fluid to flow downwardly therethrough whereby to facilitate lifting of the piston into the c red position of Fig. 1. This charging of the piston is carried out by transmitting the lifting action of the switch blade 2 to the piston rod through a plunger fixed to the switch blade 2 for abuttingly encountering the button of the stop 39. To further aid in moving the piston upwardly into the charge position, there are provided normally-closed check valves 42 which serve as inlet valves permitting the flow of fluid upwardly therethrough as the piston 35 is lifted.

Fixedly mounted at the lower end of the interrupter casing 5 is stationary easing structure comprising a lower housing 46 which has associated therewith contact opening springs 47 and 48 of the compression type, which, respectively, surrounded contact 13, and contact rod 17. Mounted adjacent the upper end of stationary housing 46 is a stationary contact guide plate 51 appropriately secured to the casing 5 as by set screws, as seen in Fig. 2. The opening springs 47 and 48 extend through suitable openings in the lower housing 46 and bear at their upper ends against the plate 51 and at their lower ends against the crosshead 16. it should be apparent from this description that when the switch blade 2 and isolating contacts l9 are moved downwardly at high speed by suitable operating mechanism (not shown) in response to tripping open of the circuit breaker, the opening springs 47 and 48 will cause the crosshead 16 with the contact button 18 to move in follow-up engagement with the isolating contact 19 into the position indicated by dotted lines in Fig. 1, thereby rapidly separating the interrupting contacts 5 and 9, for drawing a pair of series arcs in the

baflle stacks

21 and 22, respectively.

For controlling the movement of the crosshead i5 and the contact rods 11 and 13 carried thereby, there is provided in combination with the crosshead l5 and lower housing 46 a novel association of guide means and stop means. More particularly, carried by the crosshead 16 are a pair of tubular guide rods 52 (Fig. 2) which are suitably secured at their upper ends, as by threading, to an abutment plate 53. This plate has a pair of large openings therein for encircling the springs 47 and 48 as best seen in Fig. l. The lower ends of the tubular guide rods 52 are fixed to the crosshead, preferably by nuts 54-. For cooperating with the abutment plate 53 there is provided an annular stack of resilient butters 55 secured to the bottom Wall of the lower housing '46. These buffers 55 form a yielding or resilient stop for arresting, without excessive shock, the abutment plate 53 as it moves downward'ly under the influence of the opening springs 47, 48 during breaker opening. When this abutment occurs "between the plate and butfers, the contact button 18 is prevented from further movement in follow-up relation to the isolating contact '19, as a result of which further downward movement of the isolating contact 19 produces an isolating break between contacts 1'3 and 19. This continued downward movement of isolating contact 19 initially interrupts the residual current flowing through resistance R after extinction of the arcs at the interrupting contact pairs 8 and 9, and subsequently, acts to establish an isolating gap between

contacts

18 and 19.

The tubular guide rods 52 serve not only .to interconnect the crosshea'd 16 and its stop means 53 but also function to guide the crosshead 16 and the associated contacts 11 and '13 in a manner which is efiective to insure accurate straight-line reciprocation of these parts. The effectiveness of this guiding action is quite important where, as in the present interrupter, the movable contact assembly is of relatively great axial length and where, as in the present interrupter, a contact'carrying crosshead carries contact rods which have different masses. By the present invention all of those forces which tend to cause the reciprocating movable contact assembly to deviate in its movement from a straight line path are etfectively resisted. More particularly, the guide rods 52, by reason of their tubular form, are disposed in smoothly telescoping relation with elongated guide pins 56, which are rigidly fixed to the stationary guide plate 51 and extend downwardly therefrom. The relatively long axial distance over which these cooperating guide parts mate insures a stable and accurate straight line movement of the crosshead '16. Further assurance of accurate straight line motion is pro vided by cylindrical slide bearings 57, which are press fitted into suitable apertures in casing 46 and are disposed in guiding relationship about the tubular guide rods 52. It should be noted that the guide pins 56 extend downwardly to such extent that their lower tips are disposed within the bearings '57, wherein these lower tips are supported with only the slight radial clearances required for permitting sliding movement of the tubular guide rods 52. Because of this particular disposition of the lower tip .of each guide pin within the bearing 57, the guide pin 56 is analogous to a beam having one end fixed and one end supported on fixed structure but guided and free to slide with respect thereto. Since each guide pin 56 would possess the inherent strength of such a beam, it is apparent that the guide pin 56 would constitute a very stable foundation and guiding means about which the whole movable contact assembly slides in accurate reciprocable relationship. As a result, the rod contacts 11 and 13 slide freely in their baffle stacks and mate properly with their respective fixed contact finger clusters and '12, as is desired.

To further insure effective guiding action, the contact rods 13 and 17 are preferably positioned at diametrically opposed locations about a central point on the crosshead 16, and the guide tubes 52 are symmetrically located in 90 relationship to the contact rods 13 and 1'7.

To prevent overtravel of the crosshead 16 and the associated moving contacts when the circuit breaker is operated to closed position, as by lifting the crosshead to the position of Fig. 1, there is provided an overtravel spring 60 mounted on the lower end of the housing 46. This overtravel spring 60 surrounds the opening springs 47, 48 and the guide tubes 52 and is held in operating position by an annular retaining ring 61 which is mounted on an annular plate 62 secured to the housing -46 by suitable bolts 63 surrounded by spacers 64. When the crosshead is lifted to closed position, the projecting portions or lugs 65 of the crosshead are adapted to abut against the retaining ring 61, as a result of which the spring 60 absorbs the excess closing energy and prevents overtravel of the movable contact assembly.

From the above description of the crosshead 16 and its associated structure, it will be apparent that the crosshea'd serves the multiple function of providing a support for the reciprocable contacts '11 and 13 and the isolating contact element 18 and, additionally, of providing a base for the guide means and the stop means which control the reciprocable movement of the contacts 11 and 13. The net result is that there is provided a structurally compact and sturdy movable contact assembly which is effective to produce precisely guided and limited reci-procable movement of the movable contact rods.

Although the operation of the interrupter should be apparent from the above description, it may be briefly summarized as follows: When the circuit breaker is tripped open, the switch blade 2 and the isolating contact 19 are moved downwardly at high speed, as a result of which the crosshead 16 and its associated movable contacts, under the influence of opening springs 47 and 48, move downwardly in follow-up engagement with contact 19. This downward movement of the interrupting contacts ill and 13 simultaneously draws a pair of seriesrelated arcs in the baflle stacks 21 and 22. Extinction of the arcs is aided by fluid impelled across the baflle stacks by the impulse piston 35, which is moved downwardly under the influence of spring 36 coincident with downward movement of the switch blade 2. As the interrupting arcs are being extinguished in the bafile stacks, some slight current is shunted through the high ohmic resistance R until the crosshead 16 and isolating contact element 18 are prevented from further downward movement by the engagement of butter elements 53 and 55. At this time, further downward movement of isolating contact 19 interrupts the residual resistance current and provides an isolating gap between contacts 13 and 119.

The modification of Fig. 3 shows that, as an alternative to Fig. 1, the movable contact rods could be equally spaced from the axis of the pump instead of unequally as shown in Fig. 1. To illustrate this disposition of the contact rods, parts in Fig. 3 corresponding to parts of Fig. l have been given corresponding but primed reference numerals. Thus, contact rods 11' and 18', which are disposed in casing 5', are shown as being equally spaced from the piston rod 40 of pump 30. The exhaust passages 25 of the upper 'batfie stack 23 and the exhaust passage 25a of the lower stack are divergently disposed so as to respectively conduct the arcing products in divergent paths through the upper exhaust port 26' and the lower exhaust port 26a.

While we have shown our invention as applied to a multiple break circuit interrupter having two movable contact rods for the interrupting contacts, the crosshead construction readily lends itself to use with three, or even a greater number, of such rodatype contacts. The number of bafile stacks is preferably increased in accordance with an increase in the number of contact rods, whereby circuit breakers of higher voltage ratings are compounded. Such an arrangement, shown schematically by Fig. 4, preferably would have its three rod contacts arranged within the cylindrical casing in angular relationship, with three telescoping guiding means (not shown) uniformly interspersed therebetween in a manner comparable to that of the above described arrangement. Referring more particularly to Fig. 4, there are shown three pairs 80, 81, '82 of series-related contacts, each including a movable rod contact carried by a crosshead 83, which corresponds to the crosshead 16 of Fig. 1. These movable con-tacts are spaced in 120 angular relationship about the crosshead and are connected in series relationship by

contact support castings

84 and 85. Suitable bafiie stacks, not shown, are mounted adjacent to the pairs of contacts to aid in interrupting the arcs drawn thereat.

While there has been shown and described a particular embodiment of the invention, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention, and that it is intended by the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

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

1. In an electric circuit interrupter comprising casing means enclosing a plurality of pairs of relatively movable contacts, a reciprocable crosshead supporting one contact of each of said pairs of contacts in spaced-apart substantially parallel relationship, a pair of isolating contacts electrically connected in series with said plurality of pairs of contacts, one of said isolating contacts being supported by said crosshead, guide rod structure cooperating with said casing means for assuring straight line motion of said crosshead, said guide rod structure being supported by said crosshead and extending in substantially parallel relationship to the contacts carried by said crosshead, abutment structure mounted on said guide rod structure, and a yieldable buffer interposed between said casing means and said abutment structure so as to limit separation of said relatively movable contacts.

2. An electric circuit interrupter comprising casing means enclosing a plurality of pairs of relatively movable contacts, a reciprocable crosshead supporting one contact of each of said pairs of contacts in spaced-apart sub stantially parallel relationship, a pair of isolating contacts electrically connected in series with said plurality of pairs of contacts, one of said isolating contacts being supported by said crosshead, guide rod structure cooperating with said casing means for assuring straight line motion of said crosshead, said guide rod structure being supported by said crosshead and extending in substantially parallel relationship to the contacts carried by said crosshead, and resilient means mounted exterior to said casing means and arranged to engage said crosshead so as to prevent overtravel of said contacts during closing operation of said interrupter.

3. In an electric circuit interrupter comprising stationary structure mounted adjacent a plurality of pairs of relative movable contacts, a reciprocable crosshead supporting one contact of each of said pairs of contacts in spacedapart substantially parallel relationship, a pair of isolating contacts electrically connected in series with said purality of pairs of contacts, one of said isolating contacts being supported by said crosshead, an elongated guide element supported "from said stationary structure and having its axis fixed with respect to said stationary structure, and a tubular guide rod telescopically mating with said guide element to assure straight line motion or" said crosshead, said tubular guide rod being supported by said crosshead and extending in substantially parallel relationship to the contacts carried by said crosshead.

4. An electric circuit interrupter comprising stationary structure, separable contacts disposed adjacent said stationary structure, a reciprocable crosshead supporting one of said contacts, an elongated guide element supported from said stationary structure and having its axis fixed with respect to said stationary structure, a tubular guide rod supported from said crosshead and telescopically inating with said guide element to assure straight line motion or said crosshead, abutment structure mounted on said tubular guide rod, and a yieldable bufi'er positioned between said stationary structure and said abutment structure and arranged to limit separation of said relatively movable contacts.

5. An electric circuit interrupter comprising stationary structure, separable contacts disposed adjacent said stationary structure, a reciprocable crosshead supporting one of said contacts, an elongated guide element supported from said stationary structure and having its axis fixed with respect to said stationary structure, a tubular guide rod supported from said crosshead and telescopically mating with said guide element to assure straight line motion of said crosshead, abutment structure mounted on said tubular guide rod, a yieldable bufi'er positioned between said stationary structure and said abutment structure and arranged to limit separation of said relatively movable contacts, and a slide bearing rigidly mounted on said stationary structure and disposed in guiding relationship about said tubular guide rod.

6. An electric circuit interrupter comprising stationary structure, separable contacts disposed adjacent said stationary structure, a reciprocable crosshead supporting one of said contacts, an elongated guide element supported from said stationary structure and having its axis fixed with respect to said stationary structure, a tubular guide rod supported from said crosshead and telescopically mating with said guide element to assure straight line motion of said crosshead, and a slide bearing rigidly mounted on said stationary structure and disposed in guiding relationship about said tubular guide rod.

7. An electric circuit interrupter comprising stationary structure, separable contacts disposed adjacent said stationary structure, a reciprocable crosshead supporting one of said contacts, an elongated guide element supported from said stationary structure and having its axis fixed with respect to said stationary structure, a tubular guide rod supported from said crosshead and telescopically mating with said guide element to assure straight line motion of said crosshead, abutment structure mounted on said tubular guide rod, a yieldable buffer positioned between said stationary structure and said abutment structure and arranged to limit separation of said relatively movable contacts, and a slide bearing rigidly mounted on said stationary structure and disposed in guiding relationship about said tubular guide rod, said elongated guide element extending into said slide bearing.

8. An electric circuit interrupter comprising stationary structure, separable contacts disposed adjacent said stationary structure, a reciprocable crosshead supporting one of said contacts, an elongated guide clement supported 'rom said stationary structure and having its axis fixed with respect to said stationary structure, a tubular guide rod supported from said crosshead and telescopically mating With said guide element to assure straight line motion or" said crosshead, and a slide bearing rigidly mounted on said stationary structure and disposed in guiding relationship about said tubular guide rod, said elongated guide element extending into said slide bearing.

References Cited in the file of this patent UNITED STATES PATENTS