US3594524A

US3594524A - Vacuum-type electric circuit breaker

Info

Publication number: US3594524A
Application number: US9618A
Authority: US
Inventors: Milton Louis Heintz
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1970-02-09
Filing date: 1970-02-09
Publication date: 1971-07-20
Anticipated expiration: 1988-07-20

Abstract

A vacuum-type circuit breaker comprising a grounded metal tank having a tubular body portion and a top cover. Within the tank, there is a horizontally extending metal base plate at ground potential suspended from the cover by vertical rods. Attached to the baseplate are upwardly extending post-type insulators carrying at their upper ends horizontally extending vacuum interrupters. High-voltage bushings extend through the cover and are electrically connected to the interrupters by flexible conductors that prevent mechanical forces from being transmitted between the interrupters and the bushings. A closing device is mounted on the baseplate at the movable contact end of the interrupters and is connected to the interrupters by an insulating linkage for transmitting closing force thereto.

Description

United States Patent 1/1967 Flurscheim et al.

3,300,609 ZOO/145 3,303,309 2/1967 Flurscheim et a]. 200/144 B 3,527,91 l 9/l970 Sharp 200/144 B ABSTRACT: A vacuum-type circuit breaker comprising a grounded metal tank having a tubular body portion and a top cover. Within the tank, there is a horizontally extending metal base plate at ground potential suspended from the cover by vertical rods. Attached to the baseplate are upwardly extending post-type insulators carrying at their upper ends horizontally extending vacuum interrupters. High-voltage bushings extend through the cover and are electrically connected to the interrupters by flexible conductors that prevent mechanical forces from being transmitted between the interrupters and the bushings. A closing device is mounted on the baseplate at the movable contact end of the interrupter-s and is connected to the interrupters by an insulating linkage for transmitting closing force thereto.

:PATENTED mo I97! IN VE/VTOR. MILTON LHE/NTZ, BY ,atmm

ATTORNEY VACUUM-TYPE ELECTRIC CIRCUIT BREAKER This invention relates to an electric circuit breaker of the vacuum type and, more particularly, relates to a circuit breaker of this type that readily lends itself to underground applications.

Because underground circuit breakers are typically located in a small vault that provides no significant working space around the usual enclosure of the breaker, such breakers should be so constructed that their working parts Cl) can be easily removed through the top of the enclosure; (2) can be readily inspected, repaired, and adjusted while removed; and (3) can be returned to the enclosure in a condition which requires no further adjustments while within the enclosure. Moreover, such circuit breakers should be highly compact to enable them to fit into a vault of restricted size. Additionally, they should be usable with typical high-voltage bushings for underground duty that have less mechanical strength than comparable standard bushings.

An object of my invention is to provide a vacuum type circuit breaker suitable for underground applications and capable of meeting the various requirements set forth in the immediately preceding paragraph.

Another object is to provide a vacuum type circuit breaker of this type in which the high-voltage bushings can be removed and replaced without affecting the mounting of the vacuum interrupters or their operating mechanism.

In carrying out the invention in one form, I provide a grounded metal tank comprising a tubular body portion and a cover mounted on the upper end of said body portion. Within the tank there is provided a metal base plate at ground potential which extends generally horizontally. A plurality of vertically extending support rods are secured at opposite ends to said cover and said base plate for suspending the base plate from the cover. A plurality of post-type insulators are attached to the base plate and extend upwardly therefrom. Three vacuum type circuit interrupters of a conventional design are provided, each having a housing mounted on said post-type insulators at the upper ends thereof with the longitudinal axes of said housings extending generally horizontally. High-voltage bushings extend through the cover, each comprising a conductor for carrying current to or from one of the interrupters. Flexible conductors electrically connect said bushing conductors to said interrupters and have sufficient flexibility to prevent significant mechanical forces from being transmitted therethrough between the interrupters and the bushings. A closing device is mounted on the base plate adjacent the movable contact end of the interrupters and a linkage partially of insulating material connects the closing device and the interrupters for transmitting closing force to the contact rods of the interrupters.

For a better understanding of the invention, reference may be had to the following description taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a side elevational view partly in section and partly schematic showing a circuit breaker embodying one form of the invention.

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

Referring now to FIG. 1, there is shown a metal tank having a tubular body portion 11 and a metal cover 12 mounted on the top end of the body portion and bolted thereto by a flanged and gasketed joint 13 comprising bolts 94. Suspended from the cover 12 is a metal base plate 14 on which the main working parts of the circuit breaker are mounted. For suspending the base plate 14 from the cover, I provide a plurality of support rods 16, attached at their lower ends to the base plate 14 and at their upper ends to the cover 12.

The tank body 11, the tank cover 12, and the metal base plate 14 are all at ground potential. Some of the support rods 16 are metal, and this electrically ties the base plate 14 to the cover.

Mounted on the base plate 14 are three vacuum type circuit interrupters 19 of a conventional design, such as shown, for example, in U.S. Pat. No. 3,l63,735 to Miller, assigned to the assignee of the present invention. Each of these interrupters comprises a highly evacuated tubular housing 20 primarily of insulating material having its longitudinal axis extending generally parallel to the base plate 14, i.e., horizontally. The ends of the housing are closed off by

metal end plates

21 and 22 sealed thereto. Within the sealed housing are a pair of relatively

movable contacts

23 and 24. One of the contacts 24 is a stationary contact supported on a conductive stationary contact rod 24a extending in sealed relationship through end plate 22. The other contact 23 is a movable contact supported on a movable conductive contact rod 23a extending through the other end plate 21. Flexible metallic bellows 26 provides a seal about the movable contact rod.

For mounting the interrupters on the base plate, six spacedapart insulating rods, or posts, 30, two for each interrupter, are provided. Each of these insulating posts is attached at its lower end to the base plate 14 and at its upper end to a bracket 32 that in turn is secured to one of the interrupter end plates. These posts 30 are preferably made of wood impregnated with a suitable resin. Each post has metal end fittings 34 at its opposite ends that are suitably attached to the adjacent bracket or the support, as the case may be.

For operating the three interrupters into their closed position shown, I provide a suitable stored-energy closing device 36. Since this closing device 36 may be of any suitable conventional form, for example, of the type shown in U.S. Pat. No.

2,667,076 to Favre, I have shown it in block form only. The closing device is mounted on the base plate 14 at its left-hand end, as viewed in FIG. 1.

For charging the closing device and for causing it thereafter to discharge to perform a closing operation, a rotatable control shaft 39 extending vertically from the cover 12 to closing device 36 is provided. This shaft 39 is joumaled in the cover 12 and also in a stationary part of the closing device. When the shaft is rotated, e.g., by a handle 40 fixed to its upper end, it drives a worm 41 at its lower end which operates to charge the closing device and thereafter to initiate a closing operation.

For transmitting closing energy from the closing device 36 to the interrupters, I provide a rotatably mounted operating shaft 37 which is joumaled in brackets 40 secured to base plate 14. Keyed to this shaft 37 is a crank 42 that is coupled to the closing device at its left-hand end and is adapted to be operated by the closing device 36. When the closing device operates, it drives crank 42 in a clockwise direction from its dotted line position of FIG. 1 into its solid-line position, thereby rotating operating shaft 37 in a clockwise direction.

Coupled to operating shaft 37 are three additional cranks 44, one for each interrupter. These cranks 44, which are respectively aligned with the three interrupters, have their outer ends connected to the contact rods 23a of the interrupters through insulating linkages 45. Each linkage 45 comprises an operating rod 47 of insulating material, the lower end of which is pivotally connected at 48 to crank 44 and the upper end of which is pivotally connected at 49 to a guide link 50. Guide link 50 is pivotally mounted on a stationary pivot 51 carried by bracket 32.

Between the upper pivot pin 49 and the movable contact rod 23a there is a wipe mechanism 55 of conventional form, through which closing force is transmitted to the movable contact rod 23a. A wipe mechanism of this design is described in greater detail and claimed in the aforesaid Miller U.S. Pat. No. 3,163,735. In general, this wipe mechanism comprises an intermediate link 56 of rod form, one end of which is pivotally connected at 58 to the contact rod 23a and the other end of which is pivotally connected with lost motion to the operating rod 47. The connection to the operating rod 47 is through the previously described pivot 49. This pivot 49 has a transversely extending hole therethrough which slidably receives the intermediate rod 56 to permit motion of pivot 49 along the length of rod 56. Disposed between pivot 49 and the other end of the intermediate rod '56 is a compression spring 59 encircling the intermediate rod. This compression spring 59 tends to urge pivot 49 against a stop 60 fixed to the intermediate rod 56.

When the operating rod 47 is driven upwardly toward its solid line position of FIG. 1 to initiate circuit breaker closing,

driving forces are transmitted through the compression spring 59 to force movable contact rod 23a to the right, thereby mov ing contact 23 into engagement with contact 24. Following this engagement, operating rod 47 continues moving upwardly, forcing pivot 49 to slide along the intermediate rod 56, compressing spring 59, and opening a space between pivot 49 and stop 60. This overtravel action during which the spring 59 is compressed serves primarily to provide contact wipe. More specifically, this action assures that the

contacts

23, 24 are firmly driven into engagement and held in engagement with a predetermined amount of force despite loss of contact material through wear and arc erosion and without blocking the contacts of the other interrupters from engaging should the contacts of one of the interrupters engage ahead of the contacts of the other interrupters.

For insuring substantially straight line motion of contact rod 23a during the above-described closing operation, another guide link 62 is pivotally connected by pivot 58 at one end to the contact rod and at. its opposite end is pivoted on to the pin 51. In addition, aslide bearing (not shown) is provided about the contact rod 230 and is suitably fixed to end plate 21.

Contact opening is effected by driving the operating rod 47 downwardly from its solid-line position of FIG. 1. During initial movement of the operating rod 47 in this downward opening direction, no opening force is applied to the movable contact rod since the pivot 49is merely sliding along the intermediate rod 56 without driving the intermediate rod. This lost motion continues until pivot 49 strikes stop 60. When this occurs, an abrupt opening force is applied to the movable contact rod 23a, and it separates contact 23 at high speed from contact 24 to produce interruption of the circuit.

For supplying force for an opening operation, an opening spring 65 is provided. This opening spring is a compression spring that is interposed between the right-hand end of crank 42 and the baseplate 14. When crank 42 is driven in a clockwise direction during closing, it compresses spring 65. At the end of the closing operation, a trip latch 67 moves into place behind a roller.70 on the crank 42 to hold the crank in its fully closed position, Trip latch 67 is a movable latch member that is pivotally supported by stationary pivot 68 and is biased in a clockwise direction about 68 by a reset spring 69. When the circuit breaker is closed, latch 67 acting through roller 70 holds the opening spring compressed, thus holding the

contacts

23, 24 in engagement. When latch 67 is pivoted in a counterclockwise direction from its position of FIG. 1, crank 42 is released and opening spring 65 is free to expand to drive crank 42 counterclockwise into its dotted line open position. Such movement of crank 42 drives operating rods 47 downwardly to produce opening of the interrupters, as above described.

For controlling the trip latch 67, a vertically extending trip control rod 74 of insulating material is provided. At its lower end, this trip control rod 74 is pivotally connected to an arm integral with trip latch 67. At its upper end, the trip control rod extends through an opening in the cover 12, where it is suitably attached to a tripping solenoid (not shown). The tripping solenoid is controlled by a trip control circuit (not shown) disposed in a compartment 76 mounted atop the cover 12. A suitable guide is attached to the cover 12 for guiding the trip control rod 74 in its longitudinal movement. When the trip control rod is lifted it pivots the latch member 67 counterclockwise about pivot 68, thereby initiating an opening operation, as previously described.

For carrying current to and from each interrupter, I provide a pair'of spaced-apart high-voltage bushings 80 extending vertically through the cover 12. Each of these bushings comprises a centrally located conductive stud 82, a shell 83 of insulating resin surrounding the stud 82 and bonded thereto, and a metal length. Flange 84 is attached to the cover 12 by a suitable joint that provides a seal between the flange and the cover.

The lower end of the left-hand stud 82 is electrically connected to the movable contact rod 23a by flexible conductive braid 86. This braid permits the movable contact rod to be operated through its opening and closing strokes without transmitting any force to the left-hand bushing. Another flexible conductive braid 88 electrically connects stationary contact rod 24a to the lower end of the stud 82 of theright-hand bushing. The flexibility of these

braids

86 and 88 assures that none of the operating force received by the interrupter will be transmitted to the bushings.

When it is desired to gain access to any of the internal parts of the circuit breaker, the bolts at 94 are removed and the cover 12 is lifted oi? the tank body 1 1. Since all of the internal structure of the circuit breaker is attached to the cover 12, this structure lifts out of the tank body when the cover is lifted. All of the internal parts are then accessible for inspection, repair, or adjustment. After any desired repairs or adjustments are made, the cover is returned to the tank body, carrying with it the internal part of the circuit breaker. As the cover is lowered on to the tank body, the internal parts beneath it are lowered ,into their position of FIG. 1.

it is to be noted that only the cover had to be detached from the tank body as a prerequisite to removing the internal parts. It was unnecessary to detach any of the control rods or other mechanical control elements inasmuch as all of these control elements enter the tank interior through the cover and are not otherwise connected to the tank. Thus, when the cover is lifted, these parts are removed coincidentally with the cover. It is to be noted that all the interrupters and the entire operating mechanism are mounted on the common base plate 14. This enables these parts on the base plate to be positioned and adjusted with respect to each other while outside the tank 10 without necessitating any further adjustments after being returned to the tank. Because of the self-contained nature of the operating mechanism and its attachment to the same base 14 as used for the interrupters, there is no need to rely upon any additional operating mechanism or a separate base which might require adjustments of the interrupters, relative to such separate base.

Another advantage of mounting the self-contained operating mechanism and the interrupters on a common base, such as 14, is that this feature in combination with the

flexible braids

86, 88 assures that none of the operating forces are imparted to the support rods 16 or to the tank 10 or to the bushings 80. All operating forces received by the interrupters are transmitted through insulators 30 to the common base 14. The flexible braids 86 and 88 assure that these forces will not be transmitted to the bushings 80. Because none of the operating forces are transmitted to the support rods (16), these can be relatively slender, reducing their costs and the amount of space consumed thereby. Because none of the mechanical operating forces are imparted to the bushings 80, these bushings can be of a lighter weight, less expensive design than would otherwise be required.

As was previously pointed out, the base plate 14 and the tank body 11 are at ground potential. When the circuit breaker is energized, each of the interrupters 19 is at a high potential, as is the wipe mechanism 55 at one end of each interrupter. However, the remainder of the operating mechanism, which is mounted directly on grounded base plate 14, is at ground potential. The insulating character of the operating rod 47 and the supports 30 provides electrical isolation between the high potential parts and the grounded portion of the operating mechanism. Since the base plate and most of the operating mechanism are at ground potential,

there is no problem of insulating these parts from the tank 10.

This enables these parts to be brought as close as desired to the tank walls without introducing any electrical breakdown problems. Obviating the need for large clearances between the tank on one hand the base plate and the main portion of the operating mechanism on the other hand contributes significantly to the compactness of the circuit breaker. Of course, the interrupters l9 and the wipe mechanism 55, which are at high potential, must be adequately spaced from the grounded tank; but there is much more space available around these parts which can be relied upon for the desired clearances. To render this clearance space more effective in suppressing electrical breakdowns, the tank 10 is preferably filled with a suitable insulating fluid, such as oil 96 or sulfur hexafluoride. When a gas, such as sulfur hexafluoride, is used, it completely fills the space in tank.

It is to be noted that the closing device 36 and most of the operating mechanism are located at the movable contact end of the interrupters. This makes it possible to simplify the linkage interconnecting these parts to the interrupters and thus further contributes to the compactness of the design. While the trip control rod 74 is located intermediate the ends of the interrupters, this relationship is accommodated by making the trip control rod 74 of an insulating material.

While I 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 I claim as new and desire to secure by Letters Patent of the United States:

1. A vacuum-type electric circuit breaker comprising:

a. a grounded metal tank comprising a tubular body portion and a cover mounted on the upper end of said body portion,

b. a metal base plate at ground potential located within said tank and extending generally horizontally,

. a plurality of support rods extending generally vertically and secured at opposite ends to said cover and said base plate for suspending said base plate from said cover,

. a plurality of post-type insulators attached to said base plate and extending upwardly therefrom,

e. three vacuum-type circuit interrupters, each comprising a tubular insulating housing, relatively movable first and second contacts within said housing, and a contact rod supporting said second contact and extending through one end of said housing,

. means for mounting said tubular housings on said posttype insulators at the upper ends thereof with the longitudinal axes of said housings extending generally horizontally,

g. high voltage bushings extending through said cover, each comprising a conductor for carrying current to or from one of said interrupters,

h. flexible conductors for electrically connecting said bushing conductors to said interrupters and having sufficient flexibility to prevent significant mechanical forces from being transmitted therethrough between said interrupters and said bushings,

i. a closing device mounted on said base plate adjacent the movable contact end of said interrupters,

j. and a linkage partially of insulating material connecting said closing device and said contact rods for transmitting closing force to said contact rods.

2. The vacuum-type circuit breaker of claim 1 in combination with a. means for controlling said closing means comprising a rod extending vertically between said cover and said closing means,

b. means mounted atop said cover for operating said rod,

c. means for opening said circuit breaker comprising a latch mounted on said base plate and releasable to permit opening of the circuit breaker,

d. and means extending between said cover and said latch for imparting latch-releasing force to said latch.

3. The vacuum-type circuit breaker of claim 1 in which all of the structure of said circuit breaker within said tank is sup-,

ported from said cover and is carried by said cover through the top of said tank when said cover is lifted off the tank body.

4. The vacuum-type circuit breaker of claim 1 in combination with:

a. trip-controlling means disposed in a compartment located on the upper side of said cover between said high voltage bushings,

b. means for opening said circuit breaker comprising a latch mounted on said base plate, and releasable to permit opening of the circuit breaker, and

c. elongated control structure extending vertically between said trip-controlling means and said latch.

5. The vacuum-type circuit breaker of claim 1 in which said flexible conductors and said mounting of the closing device and the interrupters on a common base plate allows operating force to be transmitted from said closing device to said interrupters without imposing substantial mechanical load on said bushings or said support rods.

Claims

1. A vacuum-type electric circuit breaker comprising: a. a grounded metal tank comprising a tubular body portion and a cover mounted on the upper end of said body portion, b. a metal base plate at ground potential located within said tank and extending generally horizontally, c. a plurality of support rods extending generally vertically and secured at opposite ends to said cover and said base plate for suspending said base plate from said cover, d. a plurality of post-type insulators attached to said base plate and extending upwardly therefrom, e. three vacuum-type circuit interrupters, each comprising a tubular insulating housing, relatively movable first and second contacts within said housing, and a contact rod supporting said second contact and extending through one end of said housing, f. means for mounting said tubular housings on said post-type insulators at the upper ends thereof with the longitudinal axes of said housings extending generally horizontally, g. high voltage bushings extending through said cover, each comprising a conductor for carrying current to or from one of said interrupters, h. flexible conductors for electrically connecting said bushing conductors to said interrupters and having sufficient flexibility to prevent significant mechanical forces from being transmitted therethrough between said interrupters and said bushings, i. a closing device mounted on said base plate adjacent the movable contact end of said interrupters, j. and a linkage partially of insulating material connecting said closing device and said contact rods for transmitting closing force to said contact rods.

2. The vacuum-type circuit breaker of claim 1 in combination with a. means for controlling said closing means comprising a rod extending vertically between said cover and said closing means, b. means mounted atop said cover for operating said rod, c. means for opening said circuit breaker comprising a latch mounted on said base plate and releasable to permit opening of the circuit breaker, d. and means extending between said cover and said latch for imparting latch-releasing force to said latch.

3. The vacuum-type circuit breaker of claim 1 in which all of the structure of said circuit breaker within said tank is supported from said cover and is carried by said cover through the top of said tank when said cover is lifted off the tank body.

4. The vacuum-type circuit breaker of claim 1 in combination with: a. trip-controlling means disposed in a compartment located on the upper side of said cover between said high voltage bushings, b. means for opening said circuit breaker comprising a latch mounted on said base plate, and releasable to permit opening of the circuit breaker, and c. elongated control structure extending vertically between said trip-controlling means and said latch.