US2292095A

US2292095A - Electric circuit breaker

Info

Publication number: US2292095A
Application number: US356469A
Authority: US
Inventors: Thumim Carl
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1940-09-12
Filing date: 1940-09-12
Publication date: 1942-08-04
Anticipated expiration: 1959-08-04
Also published as: GB548520A

Description

Aug. 4, 1942. THUWM 2,292,095

ELECTRIC C IRCUIT BREAKER Filed Sept. 12, 1940 A \uxywmr I: I Inventor: MN

Carl "Th umim,

w? 57 53 by His Attorney.

Patented Aug. 4, 1942 azsaoss OFFICE stacrmo cmcurr nausea Cari Thumim, Yeadon, Pa" assignor to General Electric Company, a corp ration of New York Application September 12, 1940, Serial No. 350,409

(01. zoos2) 5 Claims.

My invention relates to an electric circuit breaker and more particularly to a trip-free fluidactuated operating mechanism therefor constructed so that the means to be actuated, such as the circuit breaker, can be released with respect to the fluid-actuated operating mechanism during the course of the closing stroke and prior to completion thereof.

Heretofore, circuit breaker operating mechanisms of the trip-free type have generally included a collapsible linkage arrangement or the like involving a more or less complicated design of toggles, levers, and latches. Since the tripfree type mechanism is required to be very rapid in action due to the fact that immediate trip-free operation of the circuit breaker is essential when the circuit breaker is closed on a fault current, mechanical arrangements have been preferred heretofore due to the unsatisfactory operation of the known fluid-actuated operating mechanisms. A trip-free fluid-actuated operating mechanism serving as satisfactorily as the comparable me-' chanical arrangements known heretofore would be very desirable in order to avoid the complicated design of toggles, levers, and latches ordinarily required. The demand for a satisfactory trip-free fluid-actuated operating mechanism has increased greatly due to the recent demand for gas-blast circuit breakers wherein fluid-actuated means, such as pneumatic-operating means, are most feasible.

Because of the importance of continuity of service, high-speed reclosing circuit breakers of all types have been developed. Fluid-operated circuit breakers have heretofore presented problems with regard to high speed reclosing analogous to those encountered in trip-free operation, and it would be desirable to provide a fluidactuated operating mechanism which is not only trip-free in operation but which is readily adaptable to high-speed reclosing of the associated circuit breaker.

It is an object of my invention, therefore, to

provide a new and improved trip-free fluid-f actuated operating mechanism that is efflcient, 4

positive, and rapid in operation, rugged and compact in design, and composed of a comparatively few essential operating elements.

It is another object of my invention to provide a fluid-actuated operating mechanism for electric circuit breakers which is not only trip free in operation but which readily lends itself to high-- speed reclosing of the circuit breaker.

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of'this specification.

For a better understanding of my invention,

reference may be had to the accompanying drawinginwhichFimlisapartlydiagrammaflc layout of a trip-free operating mechanism for an electric circuit breaker embodying my invention, while Fig. 2 is an enlarged cross-sectional view of a portion of the apparatus illustrated in Fig. 1.

Referring now to Fig. 1 of the drawing, I have illustrated an electric circuit breaker ll arranged to be operated by a fluid motor I! which is controlled by a valve arrangement, generally indicated at I 2, connected to a suitable source II of fluid under pressure. As will be described in greater detail hereinafter, means including a pair of independent dumping valves I4 and ii are interposed between the fluid motor Ii and the valve arrangement I! so that trip-free operation and high-speed reclosing, if desired, of circuit breaker ill may be obtained.

Although my invention is applicable to any fluid-operated circuit breaker, for the purpose of simplifying the drawing and the description, I have merely illustrated my invention as applied to a single-phase fluid-operated circuit breaker in of the cross gas-blast type comprising a sta-. tionary contact l8 and a movable contact 1! arranged to be operated so as to draw an arc in arc chute i8. Contacts i8 and II are arranged to be connected to suitable line terminals, not shown, by means well understood by those skilled in the art. The fixed contact i6 is provided with spring-pressed contact fingers "a and longer arcing contact fingers l6, while movable contact I! is provided with an arcing tip ii' so that, when the contacts separate, an arc is drawn between arcing tips l6 and l'|'.- Immediately after separation of the contacts, one terminal of the arc is transferred by a blast of fluid, such as air, issuing from conduit i9 which is preferably connected to source i3 through a solenoid-operated valve 20 from contact fingers iBto the arcing plate It", which is preferably provided with a tip of arcresistant metal. The fluid blast issuing from conduit is upon opening of the circuit breaker l0 drives the are drawn into arc chute it against the edges of the plurality of partitions 2i mounted in the arc chute l8 transverse to the arc gap and the ends of which extend close to the path of movement of the arcing tip "f of movable contact". .The circuit breaker i0, illustrated by way of example in order better to describe my trip-free fluid-actuated operating mechanism, is not my invention but is described and claimed in United States Letters Patent 2,284,842, granted June 2, 1942, upon the joint application of David C. Prince, William K. Rankin, and Wilfred F.

Skeats and assigned to the same assignee as the motor I I, which comprises a cylinder 22 in which is reciprocatingly mounted a piston 23 operatively connected to movable contact l1 by means of connecting rod 23. This connecting rod 23 comprises two parts, 23' and 23", joined with one another by a lost-motion connection 25 which, in turn, is arranged to operate a tripping means 26 for releasing latch 21 which holds the circuit breaker III in the closed position. For high-speed opening of circuit breaker I, it is desirable to release some form of energy-storage means to aid the fluid-operated means during the opening operation. Accordingly, I have illustrated an energy-storage means which comprises a spring 23 illustrated in the charged condition when circuit breaker I0 is closed. As illustrated in the drawing, balancing spring 23 just strong enough to balance the weight of the parts of the movable structure is supplied to hold the circuit breaker III in the open position. Latch 21 is provided in order to hold springs 23 and 23' in the charged condition so as to be ready for highspeed opening of circuit breaker I0. As shown, springs 28 and 28' are arranged to be charged or compressed by the fluid motor it during the closing movement of circuit breaker l0, and latch 21 cooperating with member 23 attached to the portion 23' of operating rod 23 restrains the circuit breaker and the springs 23. and 28' in the closed and charged positions, respectively, until upward movement of the piston 23 causes member 33 of the lost-motion connection to engage with tripping means 23, whereby latch 21 is released.

In order to operate piston 23 and, consequently,

also movable contact l1 in response to fluid pressure, source l3 of fluid under pressure, which may for example, be air under pressure, is connected by means of a conduit 3| to a manifold 32 of valve arrangement l2 from which the fluid under pressure may be led to either end of cylinder 22 in accordance with the operation of either a circuit breaker opening valve 33 or a circuit breaker closing valve 33. Opening valve 33 is normally held in the position indicated in Fig. 1, closing the lower end of manifold 32 against the fluid pressure from conduit 3|, by means of a relatively heavy spring 35 acting on a lever 33 associated with opening valve 33. Valve33 is arranged to be operated by opening solenoid 31 which is connected to one end of lever 33. In its opened position, opening valve 33 is adapted to close an escape port 38 in manifold 32 through which fluid may escape under certain conditions as will be described hereinafter.

Similarly, closing valve 33 is normally held in the position indicated in Fig. 1, closing the upper end of manifold 32 against the fluid pressure from conduit 3| by means of a relatively heavy spring 39 acting on lever 30 associated with closing valve 33. Lever 33, however, comprises two parts, namely, 33a and 33b, both mounted on a fixed pivot 30' and, hence, differs from lever 33 associated with opening valve 33 in a manner which will be described in greater detail hereinafter. Closing valve 33 is arranged to be operated by closing solenoid 3|. In its open position, closing valve 33 is adapted to close an escape port 32 through which fluid may escape to atmosphere under certain conditions;

Trip-free operation of circuit breaker I3 is obtained by virtue of dumping valve H. which will be described in detail hereinafter, and the particular construction of lever 30 and its cooperation with lever 33. Accordingly, lever 30 associated with closing valve 33 and closing solenoid 3| is constructed of two parts,"33a and 33b as mentioned above, which are held together as a single lever by means of a latch 33 pivotally mounted on member 33b and adapted to engage with an extension of member 330. A relatively light spring 33 is provided to bias the member 30b in such a direction that latch 33 may engage the extension on member 334. It willbe understood, of course, that suitable spring means will be provided for latch 33 so as normally to tend to rotate it in a coimterclockwise direction to engage with the extension of member 330.

In view of the arrangement just described. lever 33 acts as a unitary member when closing solenoid 3| is energized to open closing '.-a.lve 33 and, hence, to cause closing of circuit breaker Ill. If, however, during the closing operation of the circuit breaker l3, opening solenoid 31 should be energized through any cause, such, for example, as an abnormal current condition on the power circuit associated with circuit breaker l3, opening valve 33 would be operated. In order to obtain rapid closing of closing valve 33 under such conditions and trip-free operation of circuit breaker III, I provide a rod 33 associated with opening lever 33 which is arranged to engage a projection 33' on latch 33, thereby releasing lever 33:: and allowing heavy spring 33 to close valve 33 rapidly even though closing solenoid 3i is still energized and holding lever 33b downwardly against the tension of relatively light spring 33. The operating mechanism thus far describedisdisclosed andclalmedinmycopending application flied jointly with Edward J. Frank and Alexander C. Boiseeau, Serial No. 317,564, on February 6, 1940,.and assigned to the same assignee as the present application.

Without dumping valve l3, however, trip-free operation of circuit breaker l3 would not be obtained to a very satisfactory degree since it is evident that the reversal of piston 23 dm-lng the closing stroke will be delayed by the back pmsure acting thereon. In accordance with my invention, therefore. dumping valve I3 is provided. immediately to reduce this back presme to a very low value, upon the initiation of a trip-free operation. Dumping valve I3 is interposed between closing valve 33 and the large inlet 33 at the upper end of cylinder 22 of fluid motor ll. As best shown inFlg. 2. dumping valve l3 comprises a reciprocating pistonlike valve member 31 movably mounted in a suitable housing. A light spring 33 normally biases dumping valve member 31 against valve seat 33' adjacent the relatively large inlet 33 to cylinder 22. Dual,

ing valve member 31 is provided with 'a suitable opening 33, which is somewhat smaller than inlet 33, at the upper end of cylinder 22, through which fluid under pressure passing through valve 33 and conduit 33 may enter cylinder 22 so as to cause closure of circuit breaker II. The relative size of

openings

33 and 33 is of no consequence as far as my invention is concerned, it being merely necessary that opening 33 is somewhat and preferably considerably larger than opening 33.

Whenever closing valve 33 is opened, fluid under pressure will tightly hold pistonllke dumling valve member 31 against seat 33' causing the dumping valve to remain closed so that the full fluid pressure is urged against piston 23. If during the closing operation of circuit breaker l3, however, opening solenoid 31 were enel'lin by virtue of a fault condition existing on the power lines associated with circuit breaker l3, rod 35 would cause release of lever 33a and immediate closing of closing valve 34 would result as well asopening of escape port 42. Th fluid pressure therefore, tending to hold dumping valve 41 against seat 46' having been released through escape port 42, the back pressure in cylinder 22 upon reversal of piston 23' will cause dumping valve member 4110 move away from seat 46', thereby opening very large escape ports 5| and under pressure, a fluid motor arranged to be connected to said source, means operatively re-- pressure acting in one direction on said motor almost instantaneously reducing the pressure in cylinder 22 so that very high-speed opening and true trip-free operation of circuit breaker It may be obtained without the requirement of complicated toggles, links, and latches used in priorart arrangements.

If it were desired to obtain high-speed reclosing of circuit breaker l after a tripping operation,

means would be required to reduce the back pressure below piston 23 for, otherwise, it would be impossible to reclose with any speed. Accordingly, large inlet 52 at the lower end of cylinder 22 of fluid motor I l is provided with a valve seat 52' cooperating with dumping valve member 53 of dumping valve is which may be identical in all respects with dumping valve I4 described above. v Dumping valve I5 is interposed between large inlet 52 and. conduit 54 leading to opening valve 33. A relatively light spring 55 is provided to hold dumping valve member 53 against valve seat 52' and, as in dumping valve l4, dumping valve member 53 is provided with a suitable opening 56 through which fluid under pressure may be conveyed from opening valve 33 to cylinder 22. When reclosing circuit breaker l0 under high speed, opening valve 33 is closed and escape port 38 is opened so that a relatively small pressure below piston 23 will cause dumping valve member 53 to move away from dumping valve seat 52' and allow the fluid to escape through very large ports 51, thereby rapidly reducing the back pressure against piston 23 so that high-speed reclosure of circuit breaker l0 may be obtained. It will be understood by those skilled in the art that, by properly positioning dumping valves l4 and I5, light springs 48 and 55 may be dispensed with and valve members 41 and 53 may be held against their respective seats 45' and 52' by gravity.

In view of the detailed description included above, the operation of my trip-free fluid-actuated operating mechanism will be obvious to those skilled in the art. high-speed reclosing feature will also be obvious. It will be observed that dumping valves l4 and I5 are entirely independent and, if high-speed reclosing is not desired, dumping valve I5 might be dispensed with under certain conditions. In any event, dumping valves l4 and i5 are of simple, rugged construction and adapted instantly to reduce the back pressure resulting from the rapidreversal of fluid motor ll so that trip-free operation or high-speed reclosing. as the case may be, are obtained.

It will be apparent to those sk ed in the art that my invention is not limited to the particular construction shown but that changes and modiflcations may be made without departing from the spirit and scope of my invention, and I aim in the appended claims to cover all such changes and modifications.

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

1. In a fluid-actuated operating mechanism for an electric circuit breaker, a source or fluid The operation of the so that high-speed reversal thereof may be obtained comprising a valve member operable in response to a relatively small force produced by virtue of the back pressure resulting upon the reversal of said fluid motor.

2. In an operating system for an electric circuit breaker comprising a plurality of relatively movable contacts, a fluid motor for producing relative movement between said contacts, a source of fluid under pressure for operating said motor, means for connecting said source of fluid with said fluid motor for operating said circuit breaker, and means interposed between said fluid motor and said first-mentioned means for substantially instantaneously relieving the-fluid pressure tend-- ing to retard the reversal of said fluid motor either from closing to opening or from opening to closing movements of said circuit breaker.

3. In a fluid-actuated operating mechanism for an electric circuit breaker comprising a plurality of relatively movable contacts, a fluid motor comprising a cylinder and piston for producing relative movement between said contacts, a source of fluid under pressure for operating said motor, means for connecting said source of fluid with said motor for closing said circuit breaker, and means interposed between said fluid motor and said first-mentioned means for rapidly relieving the fluid pressure tending to retard the reversal of' said fluid motor to open said circuit breaker including a valve member operable in response to a relatively small force produced by virtue of the back pressure resulting upon the reversal of said fluid motor for opening a large escape port between said cylinder and atmosphere.

4. In a fluid-actuated operating mechanism for an electric circuit breaker, a source of fluid under pressure, a fluid motor arranged to be connected to said source, means operatively relating said motor to said circuit breaker for closing said sure, a fluid motor for producing relative movement between said contacts arranged to be connected to said source, said fluid motor comprising a cylinder and a piston reciprocally mounted therein, means defining a relatively large opening in either end of said cylinder arranged to be selectively connected to said source of fluid pressure vor to atmosphere, and means including a dumping valve associated with the opening at one end of said cylinder and operable in response to the back pressure acting on said piston upon reversal thereof for substantially instantaneously relieving said back pressure to permit high-speed reversal of said fluid motor.

. CARL THUMIM.