US3622724A

US3622724A - Vacuum-type circuit interrupter having contacts with improved arc-revolving means

Info

Publication number: US3622724A
Application number: US13429A
Authority: US
Inventors: Joseph C Sofianek
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1970-02-24
Filing date: 1970-02-24
Publication date: 1971-11-23
Anticipated expiration: 1988-11-23
Also published as: JPS5411506B1; CA919750A; JPS461975A

Abstract

Discloses a vacuum-type circuit interrupter in which the contacts are constructed to revolve any arc located between the contacts. Each contact is a disc-shaped member divided into a plurality of circumferentially spaced segments, each comprising a radially extending body portion and a leg portion at the radially outer end of the body portion extending periphery of the discshaped member. Each leg portion is provided with an arc-running extension that extends peripherally of the disc-shaped member and overlaps the adjacent segment on the side of the adjacent segment facing the other contact.

Description

United States Patent [72] Inventor Joseph C. Sofianek Broomall, Pa. [21 1 Appl. No. 13,429 [22] Filed Feb. 24, 1970 [45] Patented Nov. 23, 1971 [73] Assignee General Electric Company 54] VACUUM-TYPE CIRCUIT INTERRUPTER HAVING CONTACTS WITH IMPROVED ARC-REVOLVING MEANS 13 Claims, 3 Drawing Figs.

[52] U.S.Cl 200/144B [51] Int. Cl ..I-I01h 33/66 [50] Field of Search 200/148 B, 147

[5 6] References Cited UNITED STATES PATENTS 3,089,936 5/1963 Smith,.lr. 200/147 RX 3,185,797 5/1965 Porter ZOO/144B 3,225,167 12/1965 Greenwood 200/ l 44 B 3,462,572 8/1969 Sofianek 200/144 B 3,522,399 7/1970 Crouch 200/144 B FOREIGN PATENTS 1,113,837 5/1968 Great Britain ZOO/144 B Primary Examiner-Robert S. Macon Attorneys-J. Wesley Haubner, William Freedman, Frank L.

Neuhauser, Oscar B. Waddell and Joseph B Forman ABSTRACT: Discloses a vacuum-type circuit interrupter in which the contacts are constructed to revolve any are located between the contacts. Each contact is a disc-shaped member divided into a plurality of circumferentially spaced segments, each comprising a radially extending body portion and a leg portion at the radially outer end of the body portion extending periphery of the disc-shaped member. Each leg portion is provided with an arc-running extension that extends peripherally of the disc-shaped member and overlaps the adjacent segment on the side ofthe adjacent segment facing the other contact.

PATENTEIJunv 23 19H INVENTOR JOSEPH CSOF/ANE/r,

film ATTORNEY BACKGROUND This invention relates to a vacuum-type circuit interrupter and, more particularly, to contact structure for such an interrupter that is capable of interrupting very high currents for a small diameter of contact.

The invention is concerned with the general type of contact structure shown and claimed in U.S. Pat. No. 2,949,520- Schneider assigned to the assignee of the present invention. The contact structure of the Schneider patent comprises a disc-shaped member having a plurality of slots therein that define between adjacent pairs of slots a plurality of radially extending segments that extend circumferentially of the disc at the disc periphery. The slots produce an arc-revolving efiect that forces an arc having its terminal on the segments to revolve about the central axis of the disc. Centrally of the disc member there is a contact-making region where arcs are initiated during such an interrupting operation. Such an arc is magnetically driven radially outward off of the contact-making region; and, as it approaches the outer periphery of the disc member, it is revolved by the arc-revolving action produced by the slots of the disc member.

The amount of arc-revolving force that will be developed on an arc located near the outer periphery of the disc-shaped contact varies directly with the effective length of these segments, considered circumferentially of the disc. The diameter of the disc-shaped contact can be increased to increase the effective circumferential length of the segments, but typically there are other design considerations that limit the maximum permissible diameter of the disc-shaped contacts.

SUMMARY An object of my invention is to construct the contact in such a manner that segments of increased effective circumferentially extending lengths can be provided in a contact of limited diameter.

Another object is to achieve this increased effective segment length without detracting from the ability of the contact to cause rapid movement of the arc radially outward off of its arc-initiation region.

Still another object is to limit to a relatively low value the magnetic force urging the arc radially outward while it is being revolved. By so limiting this radially outward force, I can improve the effectiveness of the arc-revolving means and can reduce the extent to which the arc vaporizes the surrounding metal shield.

In carrying out the invention in one form, I provide, within a highly evacuated envelope, a pair of electrodes defining an arcing gap therebetween. One of the electrodes comprises a disc-shaped member comprising a plurality of circumferentially spaced segments. Each segment includes a radially extending body portion and a leg portion at the radially outer end of the body portion extending peripherally of the discshaped member. Each of the peripherally extending leg portions extends from its body portion in the same angular direction and has an arc-running extension joined to the leg portion near the distal end of the leg portion and extending in overlapping relationship with respect to the adjacent segment on the side thereof facing the arcing gap. Means is provided for forcing most of the current flowing into any extension on which an arc is located to flow through the disc-shaped member via the particular segment to which said extension is joined at the distal end ofthe segments leg portion.

BRIEF DESCRIPTION OF DRAWINGS For a better understanding of the invention. reference may be had to the following description taken in conjunction with the accompanying drawing, wherein:

FIG. I is a sectional view through a vacuum-type circuit interrupter embodying one form of the invention.

FIG. 2 is a sectional view taken along the line 2-2 of FIG. 1.

FIG. 3 is a sectional view taken along the line 3-3 of FIG. 2.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT Referring now to FIG. I, there is shown a vacuum-type circuit interrupter comprising a sealed envelope l0 evacuated to a pressure of 10" Torr or lower. This envelope comprises a tubular casing 11 of insulating material and a pair of

end caps

12 and 13 joined to opposite ends of the casing 11 by suitable vacuum-tight seals 14.

Located within envelope 10 is a pair of relatively movable contacts, or electrodes, 17 and 18, shown by the solid lines of FIG. 1 in their disengaged or open position. The right-hand contact 17 is a stationary contact suitably attached to conductive rod 17a, which at its right-hand end is united to the end cap 12. The left-hand contact 18 is a movable contact attached to a conductive operating rod 18a, which is suitably mounted for horizontal movement. Movement of the contact 18 to the right from its solid line position to its dotted line position engages the contacts and thus closes the interrupter, whereas return movement in a left-hand direction separates the contacts and opens the interrupter.

When the contacts are separated to open the interrupter, an

electric arc is established therebetween across an arcing gap 19, as will soon be described in more detail. This are vaporizes some of the contact material and projects the vapors radially outward. For condensing the vapors and protecting insulating casing 11 therefrom, a suitable metal shield 15 of tubular form is provided. This shield surrounds the arcing gap 19 and is supported on the insulating casing 11, where it is maintained at a potential substantially midway that of the two contacts when the interrupter is opened.

The operating rod projects freely through an opening in the left-hand end cap 13, and a flexible metal bellows 20 pro vides a seal about rod 180 to allow for horizontal movement of the rod without impairing the vacuum inside envelope I0. As

shown in FIG. 1, the bellows is secured in sealed relationship at its respective opposite ends tooperating rod 18a and end cap 13. A metal shield 20a of cup-shaped form is provided about the bellows 20 to protect it from arcing products.

Each of the contacts, or electrodes, 17 and 18 comprises a centrally located contact-making button 25 suitably brazed along a surface 26 to the remainder of the contact. Each of the contact-making buttons 25 is provided on its front face with a centrally located recess 27 so that contact between the buttons occurs on an annular contact-making area 28 when the contacts are in their dotted-line engaged position of FIG. I. These annular contact-making regions 28 are of such a diameter that current flowing through the closed contacts follows a radially outwardly bowing loop-shaped path L, as is indicated by the dot-dash line of FIG. 1. The magnetic effect of current flowing through this loop-shaped path L tends in a well-known manner to lengthen the loop. As a result, when the contacts are separated to form an arc between areas 28, the magnetic effect of the current through the loop will impel the arc radially outward.

As the terminals of the arch move radially outward toward the outer periphery of the

contacts

17 and 18, the arc is subjected to a circumferentially acting magnetic force that revolves the are about the central longitudinal axis of the contacts. The manner in which this circumferentially acting magnetic force is developed will be explained as the description of the contact structure proceeds. Since the

contacts

17 and 18 are substantially identical, only one of them, contact 17, will be described in detail.

It is to be understood that interruption of the circuit is effected by preventing the are from reigniting immediately following a natural current zero. Revolving the are at high speed on the contacts reduces the amount of metal vaporized, and

this facilitates recovery of dielectric strength at a current zero, thereby facilitating circuit interruption.

Contact 17 comprises a disc-shaped member having a generally circular outer periphery and a solid central portion 31. As viewed in FIG. 2, the disc-shaped member 30 contains a plurality of circumferentially spaced slots 29 with enlargements 290 at their radially inner ends. These slots 29 divide the disc into a plurality of circumferentially spaced segments, or fingers, 32, each of a generally L-shaped configuration. Each I..-shaped segment comprises a body portion 33 extending radially outward from the central portion 31 of the disc and a leg portion at the radially outer end of the body portion 33 extending circumferentially of the disc-shaped member. Each of the circumferentially extending leg portions 35 extends from its associated body portion 33 in the same angular direction, terminating just short of the body portion of the immediately adjacent segment.

As viewed in FIGS. 2 and 3, each of the segments 32 is provided with an arc-running extension 37 of its peripherally extending leg portion 35. Each extension 37 is joined by brazing at 39 to its associated segment 32 at the distal end of the peripherally extending leg portion 35 of the associated segment. The extension 37 of any given segment extends peripherally of the disc member 30 in overlapping relationship with respect to the immediately adjacent segment on the side of the adjacent segment facing the arcing gap 19. The extensions 37, taken together, form an arc-running ring that is subdivided by circumferentially spaced discontinuities 38 between adjacent extensions.

For supporting the extension 37 of a given leg portion 35 in spaced relationship to the immediately adjacent segment that the extension overlaps, I rely upon a spacer 40 disposed between the extension 37 and the immediately adjacent segment. Each of the extensions 37 and each of the segments 52 of a low-resistivity metal such as copper, but the spacer 40 is of a much higher resistivity metal such as stainless steel. Accordingly, if an are such as shown at 41 in FIG. 3 is located on one of the extensions, most of the current flowing to the are through the contact structure is forced to follow a path 43 through the segment to which the extension is attached at 39. Very little of current can flow to the are through the overlapped segment since any current flowing through the overlapped segment can reach the are only through the high-resistivity spacer 40. By forcing the major portion of the current to follow a path such as 43, which extends in the region of the arc for a relatively long distance circumferentially of the electrode, a relatively high circumferentially acting magnetic force can be developed on the arc.

Each spacer 40 has its opposite ends located in aligned recesses 45 formed in associated extension 37 and segment 32 overlapped by the extension. The ends of the spacer are suitably brazed to the adjacent walls of the surrounding recess to securely hold these parts together. In order to increase the resistance of the spacers 40 so as to reduce the amount of current passing therethrough, the spacers are provided with a restricted neck portion centrally thereof. The ends of the spacer are of relatively large diameter to provide sufficient area for adequate brazing.

As pointed out hereinabove, the amount of arc-revolving magnetic force that is developed on the arc depends upon the circumferentially extending length of the segments. By providing the extensions 37, I am, in effect, adding to the length of each segment by an amount equal to the length of each extension. By virtue of the overlapping relationship of the extension with respect to the next adjacent segment, this increased segment length is obtained without necessitating any large increase in the diameter of the contact.

Obtaining this increased segment length without an appreciable increase in the diameter of the contact is most advantageous for a number of different reasons. First of all, the larger the contact diameter, the larger must be the diameters of the surrounding tubular shield 15 and the surrounding insulating casing 11. These increases in diameter add to the cost of the interrupter and also preclude the interrupter from being used in certain limited-space applications. Secondly, the greater the radial distance between the outer tips of the contact segments and the central axis of the contact, the greater will be the tendency of the segments to bend when the contacts are subjected to sharp impacts, as would result, for example, when the contact-making regions 28 strike each other at the end of a closing stroke. By keeping the contact diameters small, I can keep this radial distance small and thus reduce this tendency of the segments to bend.

My studies indicate that it is desirable to limit to a relatively low level the radially outwardly-acting magnetic force on the are when it is on the arc-running

portion

37, 37 of the contact. One reason for this is that as this radially outward force increases, it tends to cause the arc to increasingly bow, thus lengthening it. Such lengthening of the arc appears to reduce the effectiveness of the magnetic arc-revolving action. The increased bowing of the arc also is undesirable in that it brings the arc column into closer proximity with the surrounding shield, thus causing increased melting and vaporization of the shield by the arc.

I am able to limit the radially outward magnetic force on the arc, first of all, because the contact diameter is kept quite small, considering the relatively great effective length of the extended segments, or fingers, 35, 37. Generally speaking, the radially outward force is directly dependent on contact diameter, and the small diameter thus helps to limit the radially outward force. Another factor that helps to limit the radially outward-acting magnetic force on the arc is that when the arc is on the arc-running

portion

37, 37 of the contact, I prevent it from entering a position where it is circumferentially aligned with the radially outwardly extending portion of the current path leading through the contact to the arc terminal. In this regard, note FIG. 2 where an are 41 is shown positioned on one of the extensions 37, and the current path to the arc is indicated at 43. It will be noted that the radially outward-extending portion 43a of this path 43 is circumferentially displaced from the arc. By keeping this radially outward-extending portion 43a circumferentially displaced from the arc location, there is a less pronounced radially outward bowing loop in the current path in the immediate region of the arc and thus less radially outward force on the arc. Since each of the extensions 37 is circumferentially displaced from the radially outwardly extending portion of the current path through which it is supplied and since the arc is kept on these extensions 37, I am able to prevent the are from circumferentially aligning with the radially outwardly extending current path through which it is supplied and thus am able to limit the radially outward force on the arc. A structural feature related to this circumferential displacement of the extensions 37 and the radially outwardly extending portion of the current path is that each extension 37 extends peripherally of the disc-shaped member 30 past the radially extending body portion 33 of the segment overlapped by said extension.

It is important that the arc terminal be maintained on the arc-running extensions 37 after it has been driven radially outward off the contact-making portion 28 of the contact. The arc terminal should not be permitted to attach to the outer periphery of segments 32 since there are points on this outer periphery where an arc terminal would be subjected to little or no arc-revolving force. For preventing the arc terminal from attaching to the outer periphery of segments 32, each of the arc-running extensions 37 is provided with a peripheral lip 52 (FIG. I) that extends away from the arcing gap 19 and bridges the space 53 between the extension 37 and the segment 32 that it overlaps. These lips 52 taken together form a circular flange which substantially surrounds the disc member 30 in radially spaced relationship to its outer periphery. This

circular flange

52, 52, in effect, hides the space 53 and the outer periphery of the segments 32 from the arc and keeps any arc terminal, even one on the outer periphery of the arc-running extension 37, from attaching to the outer periphery of segments 32 or from finding its way into space 53. The lips 52, it

is to be noted, are kept spaced from the outer periphery of the overlapped segments 32, thus preventing current from flowing thereto via any segment 32 overlapped by a given extension.

Although 1 limit to a low level the radially outward force on the are when it is near the outer periphery of the contact, I still wish to provide a sufficiently strong magnetic force to rapidly drive the arc radially outward off of the arc-initiation region 28 once it is initiated. To this end, I make the contact-making button 25 as large as practical so that the contact-making area 28 has as large a diameter as possible, thus accentuating the radially outward bowin current path L. The contact-making button can be of an unusually large diameter in my contact design since no appreciable intervening structure is required between the arc-initiation region 28 and the region (37) where the arc-revolving means is fully effective. As soon as the arc moves off of the arc-initiation region 28, it is on the arcrunning extensions 37, where the full circumferentially acting magnetic force is developed. To further accentuate the radially outward bow in the loop-shaped current path L, l space the contact-making button 25 from the remainder of the contact in the region behind its contact-making area 28. Support for the button in this region is provided by a ring 57 of high-resistivity stainless steel through which little current can find its way. Ring 57 is brazed on its opposite faces to the contactmaking button 25 and the segments 32 of the disc member 30. To prevent the contact-making button 25 from providing a short circuiting current path directly between the arc-running extensions 37, I provide a small space 59 between the outer periphery of the button 25 and the inner periphery of the extensions 37.

While 1 have shown and described a particular embodiment of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from my invention in its broader aspects; and I, therefore, intend herein to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What 1 claim as new and desire to secure by letters Patent of the United States is:

1. In a vacuum-type circuit interrupter comprising a highly evacuated envelope and a pair of electrodes within said envelope defining an arcing gap therebetween, one of said electrodes comprising:

a. a disc-shaped member of conductive material comprising a plurality of circumferentially spaced segments,

b. each segment including a radially extending body portion and a leg portion at the radially outer end of said body portion extending peripherally of said disc-shaped member, each of said peripherally extending leg portions extending from its associated body portion in the same angular direction,

. arc-running extensions of said peripherally extending leg portions extending peripherally of said disc-shaped member, each of said extensions being joined to its associated segment near the distal end of the peripherally extending leg portion of said associated segment and extending in overlapping relationship with respect to the adjacent segment adjacent said distal end on the side of said adjacent segment facing said arcing gap,

d. and means for forcing most of the current flowing into any extension on which an arc is located to flow through the disc-shaped member via the particular segment to which said extension is joined at the distal end of the segment's leg portion.

2. The structure of claim 1 in which each of said extensions extends peripherally of said disc-shaped member past the radially extending body portion of the segment overlapped by said extension.

3. The structure of claim 1 in which each of said extensions is supported on the segment overlapped thereby by means comprising a spacer interposed between said extension and said overlapped segment, said spacer being of a material that has a higher resistivity than the material of said segment and said extension.

4. The circuit interrupter of claim I in which each of said segments is of a generally L-shaped configuration, as viewed from said arcing gap.

5. The structure of claim 1 in further combination with:

5 a. means for initiating an are at a location radially inwardly of said peripherally extending extensions,

b. and means for propelling said are radially outwardly onto said extensions.

6. The structure of claim 1 in further combination with:

a. means for initiating an are at a location radially inwardly of said peripherally extending extensions-comprising a contact-making button having a generally annular contact-making portion supported on the body portions of said segments,

said extensions comprising means for causing the major current path through said contact-making button via said contact-making portion to extend in a radially outward direction.

7. The electrode structure of claim 1 in which said peripherally extending extensions form a generally annular arc-running ring subdivided by circumferentially spaced discontinuities between said extensions, said discontinuities being located at points circumferentially spaced from the body portions of said segments, each extension extending peripherally of said disc member past the body portion of the segment overlapped by said extension.

8. The structure of claim 1 in which:

a. said peripherally extending extensions form a generally annular arc-running ring subdivided by circumferentially spaced discontinuities between said extensions, and

b. said extensions each have a peripheral lip extending axially of said electrode away from the arcing gap in a position radially spaced from the outer periphery of the segment overlapped by said extension,

c. said lips collectively forming a generally annular flange substantially surrounding the outer periphery of said discshaped member and radially spaced therefrom.

9. The structure of claim 1 in which:

a. said peripherally extending extensions form a generally annular arc-running ring subdivided by circumferentially spaced discontinuities between said extensions,

b. a generally annular contact-making button is provided radially inwardly of said annular arc-running ring on which arcs are initiated,

c. and means is provided for preventing a low resistance conductive path from being formed through said button between said arc-running extensions.

10. The structure of claim 9 in which the means for preventing said low-resistance path from being formed comprises a space between the outer periphery of said contact-making button and the inner periphery of said arc-running ring.

ll. The structure of claim 1 in which:

a. said peripherally extending extensions fon'n a generally annular arc-running ring subdivided by circumferentially spaced discontinuities between said extensions, and

b. the body portion of any segment through which the major portion of the current flows to an are on any extension is circumferentially displaced from said extension.

12. The structure of claim 1 in which:

b. and the major current path through said electrode struc b. and means for propelling said are radially outwardly onto

Claims

1. In a vacuum-type circuit interrupter comprising a highly evacuated envelope and a pair of electrodes within said envelope defining an arcing gap therebetween, one of said electrodes comprising: a. a disc-shaped member of conductive material comprising a plurality of circumferentially spaced segments, b. each segment including a radially extending body portion and a leg portion at the radially outer end of said body portion extending peripherally of said disc-shaped member, each of said peripherally extending leg portions extending from its associated body portion in the same angular direction, c. arc-running extensions of said peripherally extending leg portions extending peripherally of said disc-shaped member, each of said extensions being joined to its associated segment near the distal end of the peripherally extending leg portion of said associated segment and extending in overlapping relationship with respect to the adjacent segment adjacent said distal end on the side of said adjacent segment facing said arcing gap, d. and means for forcing most of the current flowing into any extension on which an arc is located to flow through the discshaped member via the particular segment to which said extension is joined at the distal end of the segment''s leg portion.

4. The circuit interrupter of claim 1 in which each of said segments is of a generally L-shaped configuration, as viewed from said arcing gap.

5. The structure of claim 1 in further combination with: a. means for initiating an arc at a location radially inwardly of said peripherally extending extensions, b. and means for propelling said arc radially outwardly onto said extensions.

6. The structure of claim 1 in further combination with: a. means for initiating an arc at a location radially inwardly of said peripherally extending extensions comprising a contact-making button having a generally annular contact-making portion supported on the body portions of said segments, b. and means for propelling said arc radially outwardly onto said extensions comprising means for causing the major current path through said contact-making button via said contact-making portion to extend in a radially outward direction.

8. The structure of claim 1 in which: a. said peripherally extending extensions form a generally annular arc-running ring subdivided by circumferentially spaced discontinuities between said extensions, and b. said extensions each have a peripheral lip extending axially of said electrode away from the arcing gap in a position radially spaced from the outer periphery of the segment overlapped by said extension, c. said lips collectively forming a generally annular flange substantially surrounding the outer periphery of said disc-shaped member and radially spaced therefrom.

9. The structure of claim 1 in which: a. said peripherally extending extensions form a generally annular arc-running riNg subdivided by circumferentially spaced discontinuities between said extensions, b. a generally annular contact-making button is provided radially inwardly of said annular arc-running ring on which arcs are initiated, c. and means is provided for preventing a low resistance conductive path from being formed through said button between said arc-running extensions.

11. The structure of claim 1 in which: a. said peripherally extending extensions form a generally annular arc-running ring subdivided by circumferentially spaced discontinuities between said extensions, and b. the body portion of any segment through which the major portion of the current flows to an arc on any extension is circumferentially displaced from said extension.

12. The structure of claim 1 in which: a. said peripherally extending extensions form a generally annular arc-running ring subdivided by circumferentially spaced discontinuities between said extensions, b. and the major current path through said electrode structure to an arc at any location on said annular arc-running ring extends radially outward through said electrode structure at a location which is maintained circumferentially displaced from said arc.

13. The structure of claim 3 in which at least one of said spacers has a neck portion of reduced cross-sectional area between its ends for increasing the resistance of said spacer without decreasing the area available at the ends of the spacer for bonding the spacer to juxtaposed electrode structure.