US2422516A - Fluid pressure operated circuit breaker - Google Patents

Description

June 17, 1947. B. P. BAKER ET AL 2,422,516

FLUID PRESSURE OPERATED CIRCUIT BREAKER Filed Jar '7, 1944 fnszz/a/z'on 65 WITNESSES: 35 INVENTORS Z Benjamin PBaker anagaer'berz Jh eb.

Patented June 17, 1 947- UNITED .STATES PATENT OFFICE FLUID PRESSURE OPERATED CIRCUIT BREAKER Application January 7, 1944, Serial No. 517,304

2 Claims. 1

The invention relates particularly to circuit breakers of the compressed gas operated type wherein the ircuit breaker is operated to open and to closed position by a double acting fluid motor or piston.

It is very important in the operation of circuit breakers that an opening operation of the circuit breaker should always take precedence over, or predominate over, a closing operation, i. e., the circuit breaker should always open in response to an opening control impulse even though the means which controls closing of the breaker may be in energized or operated condition at the time. For example, if there is a short circuit condition or other abnormal condition on the line at the time the circuit breaker is being closed or reclosed, opening operation of the circuit should occur and predominate over the closing operation, even though the closing control means is in operated or energized condition. Thi has heretofore been acco p s y P oviding a trip-free mechanism between the breaker and its operating means, or, in some case, by providing either a mechanical or electrical interlocking arrangement between the opening and closing control valves for rendering the closing valve actuating means inoperative upon op nin of the circuit breaker opening valve. These prior constructions are more complicated and expensive than is desired.

An object of the present invention is the provision of a circuit breaker with an improved pneumatic operating means for opening and closing the breaker, arranged so that a circuit breaker opening operation will always predominate over a closing operation in the event of conflicting impulses.

Another object of the invention is the provision of a circuit breaker with an improved pneumatic operating means as described in the preceding object, which is of very simple and inexpensive construction, and in which the desired predomination of the opening operation over the closing operation is obtained without the use of any trip-free releasable connection or interlocking arrangement between the opening and closing valves.

In accordance with the invention, the above objects are obtained by providing the circuit breaker with a very simple pneumatic operating system arranged so that the opening force applied to the circuit breaker in response to an opening control impulse is considerably larger than the closing force, consequently opening operation of the circuit breaker will always pre- 2 dominate in the event of conflicting operating or control impulses. More specifically, the fluid operating motor is so constructed that the effective fluid pressure reactive area of that side of the operating piston to which compressed gas is applied for opening the circuit breaker is considerably larger than effective area of the opposite or closing side of the operating piston, so that the piston will always produce a circuit breaker opening operation if compressed gas is admitted to both ends of the operating cylinder.

For a better understanding of the invention, reference may be had to the following detailed description in conjunction with the accompanying drawing in which the single figure is a diagrammatic view of a circuit breaker and operating means constructed in accordance with one preferred embodiment of the invention.

Referring to the drawing, there is illustrated an electric circuit breaker 5 comprising stationary contact means I and a cooperating movable contact member 9. The circuit breaker may be of any suitable construction either of the gasblast or oil-break type. The single pole circuit breaker partially shown in the drawing is of the gas-blast type and except for the particular operating means, it is similar to the circuit breaker disclosed in the copending application of H. M. Wilcox, which issued as Patent No. 2,340,095 on January 25, 1944, assigned to the assignee of the present invention. The circuit breaker is supported on a base or frame (not shown) by a plurality of hollow insulators I 3, l5 and I! on the top of which is secured a housing IQ for the fluid motor 2! which operates the movable contact member 9 to open and closed circuit position. Rising from the housing I9 is a hollow insulator 23 on which is mounted an arc extinuishing structure 25 and a second hollow insulator 2'! on top of the arc extinguishing structure. The upper insulator encloses the stationary contact means I and supports this contact means and the upper terminal of the breaker. The lower terminal 29 of the breaker is e1ectrically connected to the rod-shaped movable contact member 9 through the agency of conducting contact fingers which slidably engage the movable contact member.

The fluid motor for operating the movable contact member 9 to open and closed positions comprises an operating-cylinder 3| and a piston 33 movable therein. The contact rod 9 slidably extends in a fluid tight manner through an opening in the upper end of the cylinder 3| and is mechanically connected directly to the operating piston 33.

A suitable source of fluid under pressure, such as compressed gas or air, for operating the piston and circuit breaker is provided comprising the reserve fluid pressure tank 35 which is connected to the main fluid pressure supply system (not shown). Fluid under pressure such as air is stored and maintained at the desired value in the tank 35 from the main fluid pressure supply.

Opening operation of the circuit breaker is controlled by an opening valve shown schematically at 3?. The valve is normally held in closed by a spring (not shown) and is arranged to be operated to open position by a solenoid 39. When the valve 31 is opened, compressed air is supplied from the tank 35, through pipes 4i and 43, into the upper end of the cylinder 3! and it quickly moves the piston 32- downwardly to th lower end of the cylinder thereby actuating the movable contact member 9 to open circuit position. Opening valve 37 in its open position is adapted to close an exhaust port 55 through which air above the operating piston 33 may escape during closing operation of the circuit breaker.

Closing operation of the circuit breaker is controlled by a closing valve shown schematically at 4'! which is also normally held in closed position by a biasing spring (not shown), and arranged to be opened by a solenoid 49. When the valve 41 is opened, compressed air is supplied from the tank 35, through pipes and 53, into th lower end of the operating cyilnder 3|, whereupon the piston 33 is quickly moved upwardly thereby actuating the movable contact member 9 to closed position in engagement with the stationary contact means. The closing valve 41 in its open position closes an exhaust port 55 through which air below the piston may escape to atmosphere during the opening operation of the circuit break- The arc drawn by the contact member upon each interruption of th circuit is-quickly extinguished by a strong blast of gas under pressure, such as air, directed to the contacts 7-9 within the chamber of the extinguishing structure 25 during the first part of the circuit opening stroke of the breaker. The blast of gas may be supplied from the fluid pressure tank 35, or from some other auxiliary source of pressur gas, and is directed to the circuit breaker contacts through a conduit El and through the passage of the hollow insulator 23 leading to the chamberof the arc extinguishing structtue 25. A blast valve shown schematically at 59 is provided for controlling the blast of gas. Th valve 59 is normally held closed by a biasing spring (not shown) and is arranged to be opened by a solenoid Bl which is energized during the first part of each opening stroke of the breaker.

A suitable electrical control system is provided for controlling operationof the opening valve 3?, the closing valve 47 and the blast valve' 59. The electrical control system illustrated in the drawing, by way of example, and also the pneumatic operating system, have been shown very diagrammatically and in very simple form, omitting a number of known and desirabl automatic features, refinements and details which are unnecessary to an understanding of the invention and which could readily be included by one skilled in art. The control system shown comprises a low-voltage direct-current supply line' 6365, a manual closing switch 6'! and a closing relay 69 of the seal-in type for energizing the closing valve -39 when energized closes seal-incontacts solenoid 49 to eiTect closing operation of the circuit breaker, a release relay H for automatically deenergizing th closing valve solenoid 49 during the final portion of the closing stroke of the breaker, a manual trip control switch 13 and a fault responsive relay T5 for energizing the opening valve solenoid 39 and the blast valve solenoid SI, and a conventional multiple auxiliary switch having adjustable, individual pole, auxiliary switch contacts TI, 19 and 8| operable in accordance with the movement and position of the circuit breaker 5.

Opening operation of the circuit breaker by manual control is initiated by closing the manual trip control switch 13. Closing of this switch completes an energizing circuit for the solenoid 39 of the opening valve 3? from the supply conductor 53 through the coil of solenoid 39, auxiliary switch contacts 19 and conductor 89 to the supply conductor 35. The switch 13 also simultaneously completes an energizing circuit for the solenoid 6| ofthe blast valve 59, through the coil of the solenoid Stand the auxiliaryswitch contacts :1 which are connected in parallel with the solenoid 39 and contacts '19. The solenoid I03 thereby connecting the solenoid coils 39 and [H to the supply conductor-G3 througha conductor Hi5, by passing the control switch-l3 and the contacts of the fault responsive relay. Upon energization, the solenoid 39opens the opening valve til-whereupon compressed air is supplied to the top of theoperating piston 33 to efiect opening operation of the circuit breaker. At a me determined-point in the opening strokeoi the breaker, th auxiliary switch contacts 19 open causing deenergization of the opening valve solenoid 39and thereby allowing thevalve to close and shut on" the flow of operating air. The blast valve solenoid BI is energized simultaneously with the opening valve solenoid so that the blast valve is opened by the time the breaker starts to open, consequently, a blast of gas is directed tothe breaker contacts to quickly extinguish'thearc drawn upon interruption of the circuit. The blast valve closes at a, predetermined point in the opening stroke of the breaker, before the opening valve closes; due to opening of the'auxiliaiy switch'contacts 77 which open and deenergize the blast valve solenoid 6i. These'auxiliary switch contacts 1'. are set so as to keep theblast valve open long enough to insure that the arc will always be extinguished even in case .of a severe short circuit condition in the circuit controlled by the breaker.

The auxiliary switch contacts' '57,"!9 and'8l, which are individually adjustable, form separate poles of a conventional drum type auxiliary switch device which is operated bythe movement and position of the circuit breaker 9, by a suitable insulated connecting linkage shown schematically at [07.

Automatic opening operation of the circuit breaker in response to predetermined abnormal fault conditions such as an overload or short circuit in the circuit controlled by the breaker: 5, is initiated by the-fault responsive relay 15 which is arranged to automatically close its contacts in response to predetermined fault conditions in the circuit controlled by the-breaker. Closing of the fault responsive relay contactscompletes the energizing circuit for the opening valve'solenoid 39 and the blast solenoid El and thereby causes opening operation of the circuit breaker in the same manner as when the trip control switch 13 is closed.

Normal closing operation of the circuit; breaker is initiated by closing the control switch 61. This completes an energizing circuit for the coil of closing relay 69 from the supply conductor 63, through the coil of relay Bil and back contacts 83 of the release relay 1! to the supply conductor 65. Upon energization, the relay 69 picks up and closes its contacts 35 completing the energizing circuit for the closing valve solenoid 49 from the conductor 63, through the contacts 85, coil of solenoid 49, and conductors 81 and 89 to the supply conductor 65. The closing relay 69 also completes a stick circuit to maintain itself energized independently of the control switch 61. This stick circuit extends from the supply conductor 63, through the seal-in contacts 9|, coil of relay 69, and through the back contacts 83 of the release relay 1| to the supply conductor 65. The contacts 9| also prepare an energizing circuit for the coil of the release relay 1|. Energization of the closing valve solenoid 49 causes opening of this valve whereupon compressed air is supplied to the lower side of the operating piston to thereby eifect closing operation of the circuit breaker. Near the end of the closing stroke of the breaker the auxiliary switch 8| closes thereby causing energization of the release relay 11 from the supply conductor 63 through the contacts 9 i coil of release relay 1!, conductor 93, auxiliary switch contacts SI, and conductor 89 to the supply conductor 85. The relay 1| thereupon picks up instantly opening its back contacts 83 and closing its front contact 95. Opening of the contacts 83 deenergizes the closing relay 69 whereupon the closing valve solenoid 49 becomes deenergized and the valve immediately closes. The contacts 95 of the release relay function to maintain the release relay 1! energized if the closing control switch 61 is held closed longer that is necessary to complete the closing operation of the breaker. This prevents pumping of the circuit breaker, because the release relay when kept energized maintains the circuit of the closing relay open until the closing control switch has been opened.

The circuit breaker may be automatically reclosed following a tripping operation, by means of a reclosing relay 99, the contacts lill of which are connected in shunt relation to the closing control switch 61. The reclosing relay can be energized automatically in any conventional manner after the circuit breaker has interrupted the circuit, and when energized this relay initiates closing operation of the circuit breaker in the same manner as when the closing control switch is closed.

As previously pointed out, it is very important that opening operation of the circuit breaker should always take precedence over, or predominate over, a closing operation in the event of conflicting control impulses, i. e., the circuit breaker should always open quickly in response to an opening control impulse even though the closing valve may be in open position at the time. This conflict of control impulse usually occurs during the closing stroke of the breaker when the breaker is being closed or reclosed against a faulted line. In accordance with the present invention, the pneumatic operating means or system is arranged in very simple manner to insure that opening operation of the circuit breaker will always take precedence over, or predominate over, closing operation of the breaker in the event of conflicting control impulses. In the embodiment of the invention illustrated this is accomplished by constructing the fluid operating moto 21 so that the effective fluid pressure reactive area of the side of the operating piston to which the fluid under pressure is applied for opening the circuit breaker is considerably larger than the effective fluid pressure reactive area of the opposite side of the piston to which fluid under pressure is applied for closing the circuit breaker. Referring to the drawing, the operating piston 33 is provided with an elongated follower or projection Ill extending downwardly from the unde side of the piston. This follower, which may be made integral with the piston or as a separate piece connected thereto, slidably extends in a fluid tight manner through an opening in the lower end or the cylinder. The follower may be of solid or hollow construction, and the cross sectional area encompassed thereby is made relatively large, much larger than the cross section of the contact rod 9 connected to the upper side of the piston. Due to the presence and size of the follower III, the effective fluid pressure reactive area of the upper or opening side of the piston 33 is considerably larger than the effective fluid pressure reactive area of the underside of the piston. The difference in effective pressure reactive areas of the opposite sides of the piston is made large enough so that if the fluid under pressure or compressed air is applied to the top or opening side of the piston any time during the closing stroke of the breaker when the closing valve is open, the force applied to the piston to open the breaker will always predominate over the closing force and the piston will be quickly moved downwardly to effect opening operation of the circuit breaker. The circuit breaker will always be opened immediately in response to an opening control impulse even though the closing valve 41 may be open and compressed air applied to the closing side of the piston.

In the embodiment of the invention illustrated, the movable contact member or rod 9 is directly connected to the operating piston so that the piston and contact move in the same direction. This is a desirable construction since it eliminates motion reversing linkages between the piston and the moving contact. The large follower III is added in order to make the effective fluid pressure reactive area of the opening side of the piston considerably larger than the eifective fluid pressure reactive area of the closing side of the piston.

It should be understood that the invention is not limited to the specific details of construction and arrangement thereof herein illustrated and that changes and modifications may occur to one skilled in the art without departing from the essential features of the invention.

We claim as our invention:

1. In an operating system for an electric circuit breaker comprising relatively movable contacts, operating means for moving said contacts to both open and closed circuit positions comprising a single cylinder, a single piston in said cylinder and a rod connected to the movable contact and extending into one end of the cylinder and connected to the piston at one side thereof, a source of fluid under pressure, a tripping valve for controlling flow of fluid under pressure to said one side of said piston for effecting opening of said circuit breaker, a closing valve for controlling flow of fluid under pressure to the opposite side of said piston for effecting closing of said breaker, a follower on said last mentioned opposite side of said piston extending slidably through the :otlier end- :of said; cylinder, said, iolloweri being :of

relativelyi-tlarger cross section than said :contact rodyso that ,thefiuid pressure-reactive area "on the opening side of saidy piston isconsiderably larger thanthe efiectivefluid pressure reactive :area of the closing side oisaid piston whereby Vquick opening operationof the circuit breaker .will occur in response .to opening of said opening valve even thoughsaid closing valve maybe open and full fiuidvpressureapplied to the closing side of thepiston.

2. In an operating system'for anceleotric circuit breaker comprising relatively movable contacts, -operating-n1eanstfor actuating saidlcontacts to open and'to closed circuit positions comprising a cylindena piston in said cylinder having a connecting rod on one side connected to the moving contact, asource of fluid underpressurea trippin valve for controlling flow of 'fiuid under pres- --sure to said one'side'of the piston for efiecting opening of said circuit breaker, aclosing valve for controlling the flow fluid-under pressure to the opposite side of-said-piston-for effecting closing of said circuit breaker, and a follower on said last inentioned'opposite side of said piston slida- 25 bly extending through theend of said cylinder,

,said ifollower; having 131 Leonsiderably 5 larger cross sectional area than said connecting rod-so that ltheceffeotiveifiuid pressure reactivearea of the opening sideoisaid pistonis considerably larger thanthe fluid pressure. reactive area of th 'closinglside of the piston whereby quick opening operation of. the oircuitbreaker will occurinresponse to opening ofgsai'dopening valve even though lsaid closing valve may-Joev openand fluid undercpressure. applied to. the closing side of said piston.

iBENJAMIN P. BAKER. HERBERTJAMES WEBB REFERENCES CITED ,Thefollowing references areof record inthe "file of this'patent:

UNITED STATES PATENTS

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