OPERATING MECHANISM FOR VACUUM CIRCUIT BREAKER INCLUDING CONTACT PRESSURE SPRINGS
United States Patent 3728508
A circuit breaker contains a pair of series-connected vacuum interrupter units which are coaxial with one another and spaced from one another. An operating mechanism is disposed between the vacuum interrupters, and is operated by an operating linkage moving along a line perpendicular to the axes of the vacuum interrupters. The operating linkage includes a toggle-type mechanism between the bottles which is expanded and contracted by the movement of the operating rod in order to operate the vacuum interrupter contacts simultaneously. A pair of conductive links used to connect the interrupters in series are used as parallelogram links for the operating toggle mechanism links. Contact loading springs are placed mechanically between the ends of the toggle links and the vacuum interrupter bottles. The contact spring forces are adjustable by the use of shims between the preloading springs and their spring carriers.
US Patent References:
High-voltage electric circuit breaker
Casey et al. - December 1968 - 3418439
Quick-make-and-break safety switch
Griswold - June 1930 - 1764401
GAS-BLAST CIRCUIT INTERRUPTER
Leeds - March 1969 - 3433913
VACUUM-TYPE CIRCUIT BREAKER WITH FORCE-SUPPLEMENTING MEANS FOR INCREASING CURRENT-CARRYING ABILITIES
Sharp et al. - August 1971 - 3597556
High-voltage electric circuit breaker
Casey et al. - December 1968 - 3418439
Quick-make-and-break safety switch
Griswold - June 1930 - 1764401
GAS-BLAST CIRCUIT INTERRUPTER
Leeds - March 1969 - 3433913
VACUUM-TYPE CIRCUIT BREAKER WITH FORCE-SUPPLEMENTING MEANS FOR INCREASING CURRENT-CARRYING ABILITIES
Sharp et al. - August 1971 - 3597556
Application Number:
05/192029
Publication Date:
04/17/1973
Filing Date:
10/26/1971
View Patent Images:
Export Citation:
Assignee:
I-T-E Imperial Corporation (Philadelphia, PA)
Primary Class:
Other Classes:
200/82B, 200/288, 218/4
International Classes:
H01H3/46; H01H33/666; H01H33/14; H01H3/32; H01H33/66; H01H33/04; H01H3/00
Field of Search:
200/144R,153S,153V,153G,153H,82R,82A,82B,144B
Primary Examiner:
Scott J. R.
Claims:
The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows
1. An operating mechanism for first and second vacuum interrupters; said first and second vacuum interrupters each including generally cylindrical housings having axially disposed and axially movable contact terminal members extending from one end surface thereof; and means for supporting said first and second vacuum interrupters in spaced coaxial relation with said one end surfaces facing one another; said operating mechanism comprising, in combination:
2. The operating mechanism of claim 1 which further includes a guide means having an elongated slot extending parallel to the direction of movement of said shaft; said operating shaft and said first and second toggle link means having a common pivot pin extending therefrom and disposed within said elongated slot for movement therein.
3. The operating mechanism of claim 1 which further includes first and second spring bracket means connected to said contact terminal members of said first and second vacuum interrupters respectively, and wherein said spring biasing means includes compression springs disposed between said first and second spring bracket means and said first and second pivotal means.
4. The operating mechanism of claim 3 wherein said first and second pivotal means connected to said first and second spring bracket means respectively, includes lost motion means whereby the toggle formed by said first and second toggle link means can collapse for a given distance from their fully extended position before said contact terminal members are directly mechanically engaged by impact force from said operating shaft.
5. The operating mechanism of claim 4 which further includes position adjustment shim means disposed between said first and second spring bracket means and said contact terminal members of said first and second vacuum interrupters respectively.
6. The operating mechanism of claim 1 which further includes accelerating spring means connected to said operating shaft for biasing said operating shaft toward an interrupter opening position; and time-delay dashpot means connected to said accelerating spring means for damping the opening movement of said first and second toggle link means as they reach the end of their movement to a collapsed position.
1. An operating mechanism for first and second vacuum interrupters; said first and second vacuum interrupters each including generally cylindrical housings having axially disposed and axially movable contact terminal members extending from one end surface thereof; and means for supporting said first and second vacuum interrupters in spaced coaxial relation with said one end surfaces facing one another; said operating mechanism comprising, in combination:
2. The operating mechanism of claim 1 which further includes a guide means having an elongated slot extending parallel to the direction of movement of said shaft; said operating shaft and said first and second toggle link means having a common pivot pin extending therefrom and disposed within said elongated slot for movement therein.
3. The operating mechanism of claim 1 which further includes first and second spring bracket means connected to said contact terminal members of said first and second vacuum interrupters respectively, and wherein said spring biasing means includes compression springs disposed between said first and second spring bracket means and said first and second pivotal means.
4. The operating mechanism of claim 3 wherein said first and second pivotal means connected to said first and second spring bracket means respectively, includes lost motion means whereby the toggle formed by said first and second toggle link means can collapse for a given distance from their fully extended position before said contact terminal members are directly mechanically engaged by impact force from said operating shaft.
5. The operating mechanism of claim 4 which further includes position adjustment shim means disposed between said first and second spring bracket means and said contact terminal members of said first and second vacuum interrupters respectively.
6. The operating mechanism of claim 1 which further includes accelerating spring means connected to said operating shaft for biasing said operating shaft toward an interrupter opening position; and time-delay dashpot means connected to said accelerating spring means for damping the opening movement of said first and second toggle link means as they reach the end of their movement to a collapsed position.
Description:
RELATED APPLICATIONS
This application is related to copending application Ser. No. 192,073, filed Oct. 26, 1971, entitled Low Profile Circuit Breaker With Staggered Terminals, in the name of Thomas F. Brandt, Jr., et al. assigned to the assignee of the present invention.
BACKGROUND OF THE INVENTION
This invention relates to an operating mechanism for vacuum circuit breakers, and more specifically relates to a novel spring toggle arrangement for simultaneously operating the movable contacts of two vacuum interrupters which are axially spaced from one another and which are disposed coaxially.
In order to use vacuum interrupters for medium high voltage circuit breakers, for example, circuit breakers rated at 34.5 kilovolts or 38 kilovolts, it is necessary to provide two presently available vacuum interrupters in series with one another. That is, an economical single vacuum interrupter bottle which can operate at these medium voltages is not available. These two vacuum interrupter units may conveniently be located coaxially with respect to one another and spaced from one another so that an operating mechanism can be positioned between the vacuum bottles. By placing the operating mechanism between the vacuum bottles, the contact pressures present in each interrupter when closed will be arranged to oppose one another.
Arrangements of this type are generally disclosed in U.S. Pat. No. 3,597,556 to Sharp, where the operating mechanism of that patent is disposed between two spaced vacuum bottles, but where, however, the mechanism is arranged to cause the contacts in the interrupter to have a wiping action.
BRIEF SUMMARY OF THE INVENTION
The principle of the present invention is to provide a novel and modified operating mechanism for two spaced vacuum interrupters which are connected in series such that contact biasing forces are provided in a direction parallel to the axis of the bottles, with a toggle mechanism automatically preloading the contacts at the time the contacts touch. The mechanism is further provided such that when the contact erosion reaches its half-life, the spring force will be equal to the recommended momentary contact loading force. The toggle mechanism is further arranged so that it cooperates with current-carrying linkages which connect the two interrupters in series with one another and which by-pass current around the operating mechanism.
More specifically, and in accordance with the invention, novel contact loading springs are provided for the operating mechanism of a pair of vacuum interrupters which are so arranged that they will hold the interrupter contacts closed against the magnetic forces generated by large momentary fault currents.
The mechanism also provides compensation for contact erosion of the contacts within the interrupter bottles. Thus, the contact loading springs are preloaded to about 75 percent of their required force for full momentary rating at the position where the contacts of the vacuum interrupters meet. As the toggle is further operated, the force on the contacts due to the springs builds up to a maximum of about 112.5 percent when the toggle is in its fully extended position. As the contacts erode due to interruption duty, this maximum force will gradually decrease. At the point where the contacts have reached their half-life (0.0625 inch erosion for a typical commercially available vacuum interrupter), the maximum spring force will be equal to the recommended momentary contact loading.
The contact spring carriage can, at this point, be adjusted by loading shims between the springs and the contact spring carriage to restore the desired contact spring force.
It will be noted that the use of a toggle linkage for operating the contacts permits the circuit breaker operating mechanism to be reduced in size as compared to an arrangement in which the contacts are operated in tandem, since the forces required from the operating mechanism to hold the contacts closed are reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 schematically illustrates portions of the mechanism used in accordance with the present invention.
FIG. 2 schematically illustrates the toggle mechanism of FIG. 1 with the mechanism components shown in their open position.
FIG. 3 is similar to FIG. 2, but shows the toggle components in their contact closed position.
FIG. 4 shows a cross-sectional view of a novel arrangement for the opening spring of the operating mechanism of FIG. 1.
FIG. 5 is a plan view, partially in cross-section, of one detailed embodiment of the invention.
FIG. 6 is a cross-sectional view of FIG. 5, taken across the section line 6 -- 6 in FIG. 5.
FIG. 7 is a perspective view, partially exploded, illustrating the toggle operating mechanism of FIGS. 5 and 6.
DETAILED DESCRIPTION OF THE DRAWINGS
Referring first to FIGS. 1, 2 and 3, there is schematically illustrated a circuit breaker mounted on a truck 10 which can be racked between various positions in a conventional manner, where the truck 10 carries a main operating mechanism 11 which moves a shaft 12 with vertical motion which is transmitted to a toggle linkage 13. The toggle linkage 13 is then connected at one end to shaft 14 and at its other end to shaft 15, where the shafts 14 and 15 are, in turn, connected to the movable contacts of vacuum interrupters 16 and 17 respectively. Each of vacuum interrupters 16 and 17 and the toggle mechanism 13 are mounted on truck 10 through the insulator posts 18 and 19.
Interrupters 16 and 17 then have outer terminals 20 and 21 respectively, where terminal 20 is connected to a primary disconnect contact 22, while terminal 21 is connected to a conductor bar 23. The conductor bar 23 is then, in turn, connected to a suitably supported primary disconnect contact 24.
It will be understood that FIG. 1 schematically illustrates only a single pole of a circuit breaker which, conventionally, would be a multi-pole unit.
The vacuum interrupters 16 and 17 are so arranged that when the operating shaft 12 is in the upper position shown in FIGS. 1 and 2, the ends of toggle links 30 and 31 will be moved to their collapsed position, so that the members 14 and 15 will be retracted relative to vacuum interrupters 16 and 17 respectively, and the vacuum interrupter contacts will be open. In order to close the vacuum interrupter contacts, shaft 12 is moved downwardly by the mechanism 11, which will be later described, so that links 30 and 31 spread away from one another in order to move members 14 and 15 toward their respective interrupters 16 and 17, thereby to close the vacuum interrupter contacts of each interrupter 16 and 17.
FIG. 3 shows the toggle links 30 and 31 in their contact closed position after having moved through the closing stroke indicated in FIG. 2. In one embodiment of the invention, where the vacuum interrupters 16 and 17 are of the type manufactured by the General Electric Company as their type No. PV-03G, this total closing stroke will be 0.75 inch for each vacuum interrupter.
In order to insure an approximate linear motion for members 14 and 15, connected to toggle links 30 and 31, guide links 32 and 33 are pivotally mounted to the lower ends of links 30 and 31 respectively, and are further pivotally supported from the upper stationary mounting structure 34. The pin 35 which connects links 30 and 31 is further guided in a suitable guide slot 36 to insure that the center of the toggle formed by links 30 and 31 moves only vertically and in the direction of movement of shaft 12.
As shown in FIGS. 2 and 3, and as will be described more fully hereinafter, the support member 34 may also be a conductive member which is electrically connected to pivot links 40 and 41, which are, in turn, electrically connected to the terminals of interrupters 16 and 17, connecting the members 14 and 15 respectively.
In accordance with an important feature of the invention, a contact loading spring, schematically illustrated in FIGS. 1 and 2 as spring 42, is connected between the end of shaft 12 and the shaft pin 35 of the toggle, including links 30 and 31. This will then provide the desired contact loading by forces exerted through pivot pin 35 when the contacts are in their closed position.
The operating mechanism 11 of FIG. 1 includes a jackshaft 50 which has a crank 51 extending therefrom for each pole of the breaker. Shaft 51, shown in FIG. 1, is connected to the bottom of shaft 12 and is further connected to an opening spring mechanism 52, which will be shown in more detail in connection with FIG. 4. When the interrupters are in their closed position (FIG. 3), the mechanism 11 is latched against motion due to opening spring 52 by the latch system including latch 53, crank 54 which rotates about fixed pivot 55, and link 56 connected to crank 51. Thus, in the closed position, the right hand end of crank 54 will be latched under latch 53. In order to open the breaker, latch 53 is removed so that crank 54 can rotate counterclockwise about shaft 55, thereby allowing opening spring 52 to move the shaft 12 upwardly from the position of FIG. 3 to the position of FIG. 2.
A closing spring 60 is provided to close the breaker contacts and the closing spring 60 is provided with an output shaft 61 pivotally mounted on rotatable latch plate 62, which has a latching detent which can be latched by the latch 63. Plate 62 is then provided with a camming surface 62a which cams against a roller 64 at the left-hand end of crank arm 54. Thus, when the latch 63 is moved to an unlatched position, as by the operation of a closing coil, the plate 62 is rotated due to the expanding action of closing spring 60 so that cam surface 62a, acting against roller 64, rapidly rotates crank 54 around shaft 55, thereby rotating crank 51 clockwise to move shaft 12 downwardly. Note that at the end of this operation, latch 53 reseats itself against the roller 54a at the right-hand end of crank 54.
The downward movement of shaft 12 causes the downward motion of pin 35, and thus the closing of the contacts, as shown in FIG. 3. Note that in moving to this fully expanded toggle position, that the spring 42 (FIGS. 1 and 2) will compress, thereby to place a spring loading force on the closed contacts. Thus, even though the contacts may erode, there will be sufficient force remaining in the precompression of the spring 42 to create the necessary contact pressure for the contacts within the interrupters 16 and 17. Moreover, this force may be easily adjusted, for example, by loading shims between the spring and its carrier, or in the case of FIG. 2, by threading the nut 65 downwardly on shaft 12, thereby to move spring containing washer 66 toward shoulder 67, which contains the lower end of spring 42.
One important feature of the present invention is in the construction of the opening spring 52, which provides a buffering dashpot to absorb the excess energy during the opening operation of the interrupters. Thus, in FIG. 4, the crank arm 51 connected to shaft 12, rotates counterclockwise in order to open the breaker. The opening springs shown as concentric springs 70 and 71 are contained within opening spring housing 72, which contains a movable plate on piston 73 which is secured to a link 74, which is connected to shaft 12 and crank arm 51. In addition, the link 74 is further connected to a shaft 75 having an enlarged head 76, which moves within a cavity 77 of the spring housing. Thus, during the opening operation, shaft 12 can move rapidly under the expanded force of springs 70 and 71, until the piston 73 passes port 78, at which time the increase in pressure on the right-hand surface of piston 73 is raised, thereby providing a strong restraining action against the continued opening movement of shaft 12. At the same time, the movement of enlarged head 76 into the chamber 77 exerts a controlled restraining force against too rapid movement of shaft 12 in the opening direction.
FIGS. 5, 6 and 7 illustrate one specific embodiment of one pole of a 34.5 kilovolt circuit breaker which uses the toggle mechanism of the present invention.
The overall breaker is best seen from FIG. 5, which shows support molding structures 100 and 101, which serve to support vacuum interrupter bottles 102 and 103 respectively. A terminal bushing 104, having a primary disconnect contact 105 at the end thereof, is connected to the fixed contact terminal of vacuum bottle 102.
An electrical conductor bar 106 is connected to the fixed contact terminal of vacuum bottle 103, and the conductor bar 106 is appropriately connected to a suitably supported bushing 107, having the second primary disconnect contact 108 at the end thereof. Note that the primary disconnect contacts 105 and 108 are not disposed above one another, but are staggered in position in order to permit a low profile for the breaker. That is, a given dielectric spacing is obtained between terminals 105 and 108, where this spacing is not a complete vertical spacing, as was the case in the prior art. Consequently, the breaker can be mounted in an outdoor cubicle having a height less than about 6 feet, which can conveniently be shielded or hidden by common shrubbery to produce an unimposing appearance for the substation using the switchgear.
Thus, the overall breaker will have a shorter profile than it would have had if the breaker terminals were disposed above one another in the conventional manner. This is the subject matter of the invention claimed in copending application Ser. No. 192,073.
FIGS. 5 and 6 also show the operating shaft 110 which corresponds to the operating shaft 12 of FIGS. 1 to 4, where the operating shaft 110 moves in the direction of arrow 111 to open the contacts of vacuum interrupters 102 and 103, and moves in the direction of arrow 112 to close the interrupter contacts.
The operating mechanism for operating the interrupters 102 and 103 is driven from shaft 110 and is generally supported and sub-assembled on the conductive block 120 (FIGS. 5 and 7). The block 120 is, in turn, secured on a top cover plate 121 by bolts 122 and 123 in FIG. 5, which thread into the top of conductive member 120. The cover plate is not shown fully in detail, but is made sufficiently wide to cover the top of the operating mechanism.
The top cover 121 is then connected to suitable side plates 124 and 125, which are, in turn, connected to the support moldings 100 and 101, and are disposed adjacent the vacuum interrupter bottles 102 and 103.
A generally L-shaped slide guide plate 126 has a flange at its upper end bolted to the top cover 121 by the bolts 127 and 128 (FIG. 5). Guide plate 126 then has an elongated guide opening 129 therein (FIGS. 5 and 7) which opening receives and guides the motion of pivot shaft 130.
The upper end of a shaft portion 131 (FIGS. 5 and 6) which is adjustably connected to the main operating shaft 112, has a cylindrical bushing 132 connected to the end thereof which slidably receives the pivot pin or shaft 130. The pivot pin 130 is then connected to the toggle link pairs 133-134 and 135-136 respectively. These toggle link pairs correspond generally to the toggle links 31 and 30 respectively in FIGS. 1 to 4. Note that these links are separated from one another by the bushing 132 on the pin 130, and further note in FIG. 6, that these links may be bent to accommodate themselves to a relatively small volume.
The opposite ends of links 133 and 134 are then pivotally connected to toggle links 137 and 138 through the pin 139, while the outer ends of links 135 and 136 are similarly connected to toggle links 140 and 141, which are carried on pin 142. The upper end of the pairs of links 137 and 138 are pivotally connected to the conductive support 120 by the pin 143 (FIGS. 5 and 7), while the upper ends of links 140 and 141 are pivotally connected to support 120 by the pin 144.
Each of pins 139 and 142 are surrounded by bushing members which have extensions 150-151 and 152-153 extending therefrom. These extensions are spring guide pins which respectively receive contact pressure springs 154 to 157 respectively. The opposite ends of contact pressure springs 154 and 155 then bear against a spring carrier plate 158 and, similarly, springs 156 and 157 press against a spring carrier plate 159. The spring carrier plates 158 and 159 then receive contact clamps 160 and 161 which clamp onto the movable contact terminals 162 and 163 respectively of vacuum interrupters 103 and 102 respectively, Note that the clamps 160 and 161 are conventional split member clamps which are tightened on the cylindrical contact terminals 162 and 163 respectively by tightening the clamping bolts. The spring carriers 158 and 159 are then firmly secured to the terminals 162 and 163 respectively, by the bolts 170 and 171 respectively, which extend through the center of the spring carriers 158 and 159 respectively, and into the ends of terminals 162 and 163 respectively.
The upper ends of clamp members 160 and 161 then have extending tongues 175 and 176, which tongues contain openings which receive suitable pins such as pins 180 and 181, which are used to form an electrical connection permitting mechanical rotation between the clamps 160 and 161 and the electrical connecting links 190-191 and 192-193. The upper ends of links 190 to 193 are also in rotatable pressure contact with the main conductive support body 120 by a suitable pressure connection which includes shafts 194 and 195 respectively (FIGS. 5 and 7). Thus, the links 190 and 191 form an electrical connection from the terminal 162 of vacuum interrupter 103 to the conductive support 120. The links 192 and 193 then continue this electrical connection from the body 120 to the terminal 163 of interrupter 102.
It should be noted that links 190-193 take all of the electrical conducting duty involved in the series connection of interrupters 102 and 103, and remove the need for electrical conduction through portions of the main operating mechanism. It will further be noted that these links also act to force movement of members 162 and 163 of interrupters 103 and 102 respectively to be constrained to a straight line so that pure butt contacting action is obtained within the vacuum interrupter units.
It will finally be observed that there is intentional free play between the end cap nuts 200-201 and 202-203, which are secured to the ends of posts 150-153 respectively, and serve as a stop for the movement of the spring brackets 158 and 159. As will be seen more fully hereinafter, this intentional free play improves the operation of the unit during opening, since it permits the application of an impact force to the closed contacts.
The operating mechanism of FIGS. 5, 6 and 7 is shown with the interrupter contacts in their closed position. It will be noted that the forces of springs 154 through 157 (which serve the purpose of spring 42 in FIGS. 1, 2 and 3) press the spring carriers 158 and 159 outwardly and away from one another, thereby to press the movable contact terminals 162 and 163 of interrupters 103 and 102 respectively toward their contact engaged position. Note further that the contact biasing force is axially directed in the same direction in which the contacts would normally move. It will also be seen that the breaker can be held in its closed position through the toggle mechanism with the application of relatively small forces to the shaft 110.
The operating mechanism is so adjusted that when the toggle is in its fully extended position, as shown in FIGS. 5 and 6, the force on the contacts is about 112.5 percent of the rated force. Thus, when the contacts erode due to interruption, so that the spring carriers 158 and 159 will be further apart when the breaker contacts are closed, the reduction in spring force will be to the 100 percent figure after the contacts have eroded by their half-life, which would conventionally be about 0.0625 inch. This force can then be easily adjusted by the location of shims in the toggle mechanism. Thus, in FIGS. 5 and 6, there are shown shims 210 and 211 disposed between spring carriers 158 and 159 and the terminal members 162 and 163 respectively.
It is important to note that the use of these shims does not affect the stroke of the operating mechanism, but merely change the end position of the movable contacts.
In order to open the interrupter, shaft 110 moves upwardly in the direction of arrow 111, with the shaft being guided for linear movement by the guide slot 129, which receives pin 130. The upward movement of pin 130 causes toggle links 133-134 and 135-136 to move inwardly. Once they have reached a given position, the nuts 200 to 203 on the spring guide pins 150-153 respectively, strike their respective spring carriers 158 and 159. This impact force is then applied to the contacts of interrupters 102 and 103 in order to break any welds that may have been formed between these contacts, and the continued movement of pin 130 upwardly causes the continued relative inward movement of the interrupter contacts, moving them to their disengaged positions.
During this movement, guide links 137 and 138, and 140-141 move respectively clockwise and counterclockwise, and similarly, the links 190-191 and 192-193 execute the same movement. Thus, these various pairs of links form two parallelograms causing the brackets 160 and 161 to move generally linearly, without rotation. Thus, good straight-line action is obtained for the movement of the movable contacts of interrupters 102 and 103. Note further that this novel action is obtained by incorporating the links 190-193, which are used primarily to form the electrical conducting path through the series connected interrupters, in the mechanical toggle mechanism.
In order to reclose the interrupters, the operating shaft 110 is moved downwardly in the direction of arrow 112 and the toggle mechanism responds accordingly by extending between the pins 139 and 142. The mechanism is so adjusted that at the instant the contacts touch, the contact loading springs are preloaded to about 75 percent of the required force for full momentary rating. As the toggle is further operated, this force on the contacts builds up to its predescribed maximum of 112.5 percent when the toggle has been fully extended.
Although there has been described a preferred embodiment of this novel invention, many variations and modifications will now be apparent to those skilled in the art. Therefore, this invention is to be limited, not by the specific disclosure herein, but only by the appended claims.
This application is related to copending application Ser. No. 192,073, filed Oct. 26, 1971, entitled Low Profile Circuit Breaker With Staggered Terminals, in the name of Thomas F. Brandt, Jr., et al. assigned to the assignee of the present invention.
BACKGROUND OF THE INVENTION
This invention relates to an operating mechanism for vacuum circuit breakers, and more specifically relates to a novel spring toggle arrangement for simultaneously operating the movable contacts of two vacuum interrupters which are axially spaced from one another and which are disposed coaxially.
In order to use vacuum interrupters for medium high voltage circuit breakers, for example, circuit breakers rated at 34.5 kilovolts or 38 kilovolts, it is necessary to provide two presently available vacuum interrupters in series with one another. That is, an economical single vacuum interrupter bottle which can operate at these medium voltages is not available. These two vacuum interrupter units may conveniently be located coaxially with respect to one another and spaced from one another so that an operating mechanism can be positioned between the vacuum bottles. By placing the operating mechanism between the vacuum bottles, the contact pressures present in each interrupter when closed will be arranged to oppose one another.
Arrangements of this type are generally disclosed in U.S. Pat. No. 3,597,556 to Sharp, where the operating mechanism of that patent is disposed between two spaced vacuum bottles, but where, however, the mechanism is arranged to cause the contacts in the interrupter to have a wiping action.
BRIEF SUMMARY OF THE INVENTION
The principle of the present invention is to provide a novel and modified operating mechanism for two spaced vacuum interrupters which are connected in series such that contact biasing forces are provided in a direction parallel to the axis of the bottles, with a toggle mechanism automatically preloading the contacts at the time the contacts touch. The mechanism is further provided such that when the contact erosion reaches its half-life, the spring force will be equal to the recommended momentary contact loading force. The toggle mechanism is further arranged so that it cooperates with current-carrying linkages which connect the two interrupters in series with one another and which by-pass current around the operating mechanism.
More specifically, and in accordance with the invention, novel contact loading springs are provided for the operating mechanism of a pair of vacuum interrupters which are so arranged that they will hold the interrupter contacts closed against the magnetic forces generated by large momentary fault currents.
The mechanism also provides compensation for contact erosion of the contacts within the interrupter bottles. Thus, the contact loading springs are preloaded to about 75 percent of their required force for full momentary rating at the position where the contacts of the vacuum interrupters meet. As the toggle is further operated, the force on the contacts due to the springs builds up to a maximum of about 112.5 percent when the toggle is in its fully extended position. As the contacts erode due to interruption duty, this maximum force will gradually decrease. At the point where the contacts have reached their half-life (0.0625 inch erosion for a typical commercially available vacuum interrupter), the maximum spring force will be equal to the recommended momentary contact loading.
The contact spring carriage can, at this point, be adjusted by loading shims between the springs and the contact spring carriage to restore the desired contact spring force.
It will be noted that the use of a toggle linkage for operating the contacts permits the circuit breaker operating mechanism to be reduced in size as compared to an arrangement in which the contacts are operated in tandem, since the forces required from the operating mechanism to hold the contacts closed are reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 schematically illustrates portions of the mechanism used in accordance with the present invention.
FIG. 2 schematically illustrates the toggle mechanism of FIG. 1 with the mechanism components shown in their open position.
FIG. 3 is similar to FIG. 2, but shows the toggle components in their contact closed position.
FIG. 4 shows a cross-sectional view of a novel arrangement for the opening spring of the operating mechanism of FIG. 1.
FIG. 5 is a plan view, partially in cross-section, of one detailed embodiment of the invention.
FIG. 6 is a cross-sectional view of FIG. 5, taken across the section line 6 -- 6 in FIG. 5.
FIG. 7 is a perspective view, partially exploded, illustrating the toggle operating mechanism of FIGS. 5 and 6.
DETAILED DESCRIPTION OF THE DRAWINGS
Referring first to FIGS. 1, 2 and 3, there is schematically illustrated a circuit breaker mounted on a truck 10 which can be racked between various positions in a conventional manner, where the truck 10 carries a main operating mechanism 11 which moves a shaft 12 with vertical motion which is transmitted to a toggle linkage 13. The toggle linkage 13 is then connected at one end to shaft 14 and at its other end to shaft 15, where the shafts 14 and 15 are, in turn, connected to the movable contacts of vacuum interrupters 16 and 17 respectively. Each of vacuum interrupters 16 and 17 and the toggle mechanism 13 are mounted on truck 10 through the insulator posts 18 and 19.
Interrupters 16 and 17 then have outer terminals 20 and 21 respectively, where terminal 20 is connected to a primary disconnect contact 22, while terminal 21 is connected to a conductor bar 23. The conductor bar 23 is then, in turn, connected to a suitably supported primary disconnect contact 24.
It will be understood that FIG. 1 schematically illustrates only a single pole of a circuit breaker which, conventionally, would be a multi-pole unit.
The vacuum interrupters 16 and 17 are so arranged that when the operating shaft 12 is in the upper position shown in FIGS. 1 and 2, the ends of toggle links 30 and 31 will be moved to their collapsed position, so that the members 14 and 15 will be retracted relative to vacuum interrupters 16 and 17 respectively, and the vacuum interrupter contacts will be open. In order to close the vacuum interrupter contacts, shaft 12 is moved downwardly by the mechanism 11, which will be later described, so that links 30 and 31 spread away from one another in order to move members 14 and 15 toward their respective interrupters 16 and 17, thereby to close the vacuum interrupter contacts of each interrupter 16 and 17.
FIG. 3 shows the toggle links 30 and 31 in their contact closed position after having moved through the closing stroke indicated in FIG. 2. In one embodiment of the invention, where the vacuum interrupters 16 and 17 are of the type manufactured by the General Electric Company as their type No. PV-03G, this total closing stroke will be 0.75 inch for each vacuum interrupter.
In order to insure an approximate linear motion for members 14 and 15, connected to toggle links 30 and 31, guide links 32 and 33 are pivotally mounted to the lower ends of links 30 and 31 respectively, and are further pivotally supported from the upper stationary mounting structure 34. The pin 35 which connects links 30 and 31 is further guided in a suitable guide slot 36 to insure that the center of the toggle formed by links 30 and 31 moves only vertically and in the direction of movement of shaft 12.
As shown in FIGS. 2 and 3, and as will be described more fully hereinafter, the support member 34 may also be a conductive member which is electrically connected to pivot links 40 and 41, which are, in turn, electrically connected to the terminals of interrupters 16 and 17, connecting the members 14 and 15 respectively.
In accordance with an important feature of the invention, a contact loading spring, schematically illustrated in FIGS. 1 and 2 as spring 42, is connected between the end of shaft 12 and the shaft pin 35 of the toggle, including links 30 and 31. This will then provide the desired contact loading by forces exerted through pivot pin 35 when the contacts are in their closed position.
The operating mechanism 11 of FIG. 1 includes a jackshaft 50 which has a crank 51 extending therefrom for each pole of the breaker. Shaft 51, shown in FIG. 1, is connected to the bottom of shaft 12 and is further connected to an opening spring mechanism 52, which will be shown in more detail in connection with FIG. 4. When the interrupters are in their closed position (FIG. 3), the mechanism 11 is latched against motion due to opening spring 52 by the latch system including latch 53, crank 54 which rotates about fixed pivot 55, and link 56 connected to crank 51. Thus, in the closed position, the right hand end of crank 54 will be latched under latch 53. In order to open the breaker, latch 53 is removed so that crank 54 can rotate counterclockwise about shaft 55, thereby allowing opening spring 52 to move the shaft 12 upwardly from the position of FIG. 3 to the position of FIG. 2.
A closing spring 60 is provided to close the breaker contacts and the closing spring 60 is provided with an output shaft 61 pivotally mounted on rotatable latch plate 62, which has a latching detent which can be latched by the latch 63. Plate 62 is then provided with a camming surface 62a which cams against a roller 64 at the left-hand end of crank arm 54. Thus, when the latch 63 is moved to an unlatched position, as by the operation of a closing coil, the plate 62 is rotated due to the expanding action of closing spring 60 so that cam surface 62a, acting against roller 64, rapidly rotates crank 54 around shaft 55, thereby rotating crank 51 clockwise to move shaft 12 downwardly. Note that at the end of this operation, latch 53 reseats itself against the roller 54a at the right-hand end of crank 54.
The downward movement of shaft 12 causes the downward motion of pin 35, and thus the closing of the contacts, as shown in FIG. 3. Note that in moving to this fully expanded toggle position, that the spring 42 (FIGS. 1 and 2) will compress, thereby to place a spring loading force on the closed contacts. Thus, even though the contacts may erode, there will be sufficient force remaining in the precompression of the spring 42 to create the necessary contact pressure for the contacts within the interrupters 16 and 17. Moreover, this force may be easily adjusted, for example, by loading shims between the spring and its carrier, or in the case of FIG. 2, by threading the nut 65 downwardly on shaft 12, thereby to move spring containing washer 66 toward shoulder 67, which contains the lower end of spring 42.
One important feature of the present invention is in the construction of the opening spring 52, which provides a buffering dashpot to absorb the excess energy during the opening operation of the interrupters. Thus, in FIG. 4, the crank arm 51 connected to shaft 12, rotates counterclockwise in order to open the breaker. The opening springs shown as concentric springs 70 and 71 are contained within opening spring housing 72, which contains a movable plate on piston 73 which is secured to a link 74, which is connected to shaft 12 and crank arm 51. In addition, the link 74 is further connected to a shaft 75 having an enlarged head 76, which moves within a cavity 77 of the spring housing. Thus, during the opening operation, shaft 12 can move rapidly under the expanded force of springs 70 and 71, until the piston 73 passes port 78, at which time the increase in pressure on the right-hand surface of piston 73 is raised, thereby providing a strong restraining action against the continued opening movement of shaft 12. At the same time, the movement of enlarged head 76 into the chamber 77 exerts a controlled restraining force against too rapid movement of shaft 12 in the opening direction.
FIGS. 5, 6 and 7 illustrate one specific embodiment of one pole of a 34.5 kilovolt circuit breaker which uses the toggle mechanism of the present invention.
The overall breaker is best seen from FIG. 5, which shows support molding structures 100 and 101, which serve to support vacuum interrupter bottles 102 and 103 respectively. A terminal bushing 104, having a primary disconnect contact 105 at the end thereof, is connected to the fixed contact terminal of vacuum bottle 102.
An electrical conductor bar 106 is connected to the fixed contact terminal of vacuum bottle 103, and the conductor bar 106 is appropriately connected to a suitably supported bushing 107, having the second primary disconnect contact 108 at the end thereof. Note that the primary disconnect contacts 105 and 108 are not disposed above one another, but are staggered in position in order to permit a low profile for the breaker. That is, a given dielectric spacing is obtained between terminals 105 and 108, where this spacing is not a complete vertical spacing, as was the case in the prior art. Consequently, the breaker can be mounted in an outdoor cubicle having a height less than about 6 feet, which can conveniently be shielded or hidden by common shrubbery to produce an unimposing appearance for the substation using the switchgear.
Thus, the overall breaker will have a shorter profile than it would have had if the breaker terminals were disposed above one another in the conventional manner. This is the subject matter of the invention claimed in copending application Ser. No. 192,073.
FIGS. 5 and 6 also show the operating shaft 110 which corresponds to the operating shaft 12 of FIGS. 1 to 4, where the operating shaft 110 moves in the direction of arrow 111 to open the contacts of vacuum interrupters 102 and 103, and moves in the direction of arrow 112 to close the interrupter contacts.
The operating mechanism for operating the interrupters 102 and 103 is driven from shaft 110 and is generally supported and sub-assembled on the conductive block 120 (FIGS. 5 and 7). The block 120 is, in turn, secured on a top cover plate 121 by bolts 122 and 123 in FIG. 5, which thread into the top of conductive member 120. The cover plate is not shown fully in detail, but is made sufficiently wide to cover the top of the operating mechanism.
The top cover 121 is then connected to suitable side plates 124 and 125, which are, in turn, connected to the support moldings 100 and 101, and are disposed adjacent the vacuum interrupter bottles 102 and 103.
A generally L-shaped slide guide plate 126 has a flange at its upper end bolted to the top cover 121 by the bolts 127 and 128 (FIG. 5). Guide plate 126 then has an elongated guide opening 129 therein (FIGS. 5 and 7) which opening receives and guides the motion of pivot shaft 130.
The upper end of a shaft portion 131 (FIGS. 5 and 6) which is adjustably connected to the main operating shaft 112, has a cylindrical bushing 132 connected to the end thereof which slidably receives the pivot pin or shaft 130. The pivot pin 130 is then connected to the toggle link pairs 133-134 and 135-136 respectively. These toggle link pairs correspond generally to the toggle links 31 and 30 respectively in FIGS. 1 to 4. Note that these links are separated from one another by the bushing 132 on the pin 130, and further note in FIG. 6, that these links may be bent to accommodate themselves to a relatively small volume.
The opposite ends of links 133 and 134 are then pivotally connected to toggle links 137 and 138 through the pin 139, while the outer ends of links 135 and 136 are similarly connected to toggle links 140 and 141, which are carried on pin 142. The upper end of the pairs of links 137 and 138 are pivotally connected to the conductive support 120 by the pin 143 (FIGS. 5 and 7), while the upper ends of links 140 and 141 are pivotally connected to support 120 by the pin 144.
Each of pins 139 and 142 are surrounded by bushing members which have extensions 150-151 and 152-153 extending therefrom. These extensions are spring guide pins which respectively receive contact pressure springs 154 to 157 respectively. The opposite ends of contact pressure springs 154 and 155 then bear against a spring carrier plate 158 and, similarly, springs 156 and 157 press against a spring carrier plate 159. The spring carrier plates 158 and 159 then receive contact clamps 160 and 161 which clamp onto the movable contact terminals 162 and 163 respectively of vacuum interrupters 103 and 102 respectively, Note that the clamps 160 and 161 are conventional split member clamps which are tightened on the cylindrical contact terminals 162 and 163 respectively by tightening the clamping bolts. The spring carriers 158 and 159 are then firmly secured to the terminals 162 and 163 respectively, by the bolts 170 and 171 respectively, which extend through the center of the spring carriers 158 and 159 respectively, and into the ends of terminals 162 and 163 respectively.
The upper ends of clamp members 160 and 161 then have extending tongues 175 and 176, which tongues contain openings which receive suitable pins such as pins 180 and 181, which are used to form an electrical connection permitting mechanical rotation between the clamps 160 and 161 and the electrical connecting links 190-191 and 192-193. The upper ends of links 190 to 193 are also in rotatable pressure contact with the main conductive support body 120 by a suitable pressure connection which includes shafts 194 and 195 respectively (FIGS. 5 and 7). Thus, the links 190 and 191 form an electrical connection from the terminal 162 of vacuum interrupter 103 to the conductive support 120. The links 192 and 193 then continue this electrical connection from the body 120 to the terminal 163 of interrupter 102.
It should be noted that links 190-193 take all of the electrical conducting duty involved in the series connection of interrupters 102 and 103, and remove the need for electrical conduction through portions of the main operating mechanism. It will further be noted that these links also act to force movement of members 162 and 163 of interrupters 103 and 102 respectively to be constrained to a straight line so that pure butt contacting action is obtained within the vacuum interrupter units.
It will finally be observed that there is intentional free play between the end cap nuts 200-201 and 202-203, which are secured to the ends of posts 150-153 respectively, and serve as a stop for the movement of the spring brackets 158 and 159. As will be seen more fully hereinafter, this intentional free play improves the operation of the unit during opening, since it permits the application of an impact force to the closed contacts.
The operating mechanism of FIGS. 5, 6 and 7 is shown with the interrupter contacts in their closed position. It will be noted that the forces of springs 154 through 157 (which serve the purpose of spring 42 in FIGS. 1, 2 and 3) press the spring carriers 158 and 159 outwardly and away from one another, thereby to press the movable contact terminals 162 and 163 of interrupters 103 and 102 respectively toward their contact engaged position. Note further that the contact biasing force is axially directed in the same direction in which the contacts would normally move. It will also be seen that the breaker can be held in its closed position through the toggle mechanism with the application of relatively small forces to the shaft 110.
The operating mechanism is so adjusted that when the toggle is in its fully extended position, as shown in FIGS. 5 and 6, the force on the contacts is about 112.5 percent of the rated force. Thus, when the contacts erode due to interruption, so that the spring carriers 158 and 159 will be further apart when the breaker contacts are closed, the reduction in spring force will be to the 100 percent figure after the contacts have eroded by their half-life, which would conventionally be about 0.0625 inch. This force can then be easily adjusted by the location of shims in the toggle mechanism. Thus, in FIGS. 5 and 6, there are shown shims 210 and 211 disposed between spring carriers 158 and 159 and the terminal members 162 and 163 respectively.
It is important to note that the use of these shims does not affect the stroke of the operating mechanism, but merely change the end position of the movable contacts.
In order to open the interrupter, shaft 110 moves upwardly in the direction of arrow 111, with the shaft being guided for linear movement by the guide slot 129, which receives pin 130. The upward movement of pin 130 causes toggle links 133-134 and 135-136 to move inwardly. Once they have reached a given position, the nuts 200 to 203 on the spring guide pins 150-153 respectively, strike their respective spring carriers 158 and 159. This impact force is then applied to the contacts of interrupters 102 and 103 in order to break any welds that may have been formed between these contacts, and the continued movement of pin 130 upwardly causes the continued relative inward movement of the interrupter contacts, moving them to their disengaged positions.
During this movement, guide links 137 and 138, and 140-141 move respectively clockwise and counterclockwise, and similarly, the links 190-191 and 192-193 execute the same movement. Thus, these various pairs of links form two parallelograms causing the brackets 160 and 161 to move generally linearly, without rotation. Thus, good straight-line action is obtained for the movement of the movable contacts of interrupters 102 and 103. Note further that this novel action is obtained by incorporating the links 190-193, which are used primarily to form the electrical conducting path through the series connected interrupters, in the mechanical toggle mechanism.
In order to reclose the interrupters, the operating shaft 110 is moved downwardly in the direction of arrow 112 and the toggle mechanism responds accordingly by extending between the pins 139 and 142. The mechanism is so adjusted that at the instant the contacts touch, the contact loading springs are preloaded to about 75 percent of the required force for full momentary rating. As the toggle is further operated, this force on the contacts builds up to its predescribed maximum of 112.5 percent when the toggle has been fully extended.
Although there has been described a preferred embodiment of this novel invention, many variations and modifications will now be apparent to those skilled in the art. Therefore, this invention is to be limited, not by the specific disclosure herein, but only by the appended claims.