US3402373A - Control means momentarily operated in response to circuit-breaker opening - Google Patents

Description

Sept. 17, 1968 J. P. WERNER 3,402,373

CONTROL MEANS MOMENTAHILY OPERATED IN RESPONSE To CIRCUITBREAKER OPENING 18, 1966 2 Sheets-Sheet 1 Filed Nov.

OPEN

C/RCU/T BREAKER OPENING IN VENTOR. 10,4 CH/M P/ETER WERNER,

BY 7 W ATTORNEY Sept. 17, 1968 J. P. WERNER 3,402,373

I CONTROL MEANS MOMENTARILY OPERATED IN RESPONSE TO CIRCUIT-BREAKER OPENING Filed Nov. 18, 1966 2 Sheets-Sheet 2 C/RCU/T SHEA/(ER CLOSED IN VEN TOR. J04 cH/M P/ETER WERNER,

BY Rim ATTORNEY United States Patent 3,402,373 CONTROL MEANS MOMENTARILY OPERATED IN RESPONSE TO CIRCUIT-BREAKER OPENING Joachim Pieter Werner, Havertown, Pa., assignor to General Electric Company, a corporation of New York Filed Nov. 18, 1966, Ser. No. 595,422 4 Claims. (Cl. 33524) This invention relates to a control circuit which is responsive to the opening of an electric circuit breaker but is non-responsive t0 circuit-breaker closing.

Some control circuits of this type rely upon a control switch which must be momentarily operated in response to circuit-breaker opening. In the particular application that I am concerned with, the control switch must be maintained in its operated position for a relatively long period, e.g., thirty milliseconds, and then returned to its original position at the end of this period.

There are special mechanisms available for providing the desired momentary actuation of the control switch, but these mechanisms are relatively expensive and are ordinarily usable only with circuit breakers that consume a relatively long period of time in opening. Such mechanisms are not ordinarily usable with circuit breakers, such as vacuum circuit breakers, which complete their opening operation in a very short period, frequently even less than the period over which the control switch must be maintained in its operated position.

An object of the present invention is to provide simple and inexpensive means responsive to circuit-breaker opening for operating such a control switch which is readily usable with circuit breakers that can complete an opening operation in a short period, which may be even less than the period over which the control switch must be maintained in operated position.

In carrying out the invention in one form, I provide a circuit breaker with a mechanically trip-free operating mechanism. This mechanism comprises a trip-free member which is latched in a normal position when the circuit breaker is closed, is unlatched to permit collapse of the trip-free mechanism thus allowing the circuit breaker to open, and is automatically returned to its normal position after circuit-breaker opening to reset the trip-free mechanism. I utilize motion of this trip-free member to control operation of the control switch, operating the control switch in response to movement of the trip-free member out of its normal position and terminating operation of the control switch in response to return of the trip-free member to its normal position.

One application for such a control switch is to provide back-up for the usual cut-off switch present in the closing control circuit of the circuit breaker. In this respect, it is important to deenergize the closing device of a circuit breaker at the end of its closing stroke, and this is customarily done by a bb cutoff switch which opens in response to the circuit breakers reaching its substantially fully closed position. If the circuit breaker should immediately trip open following closing, this bb cut-off switch would quickly close in response to such circuit-breaker opening, allowing insufficient time for the desired deenergization of the circuit breaker closing device. My control switch assures the desired deenergization of the circuit breaker closing device since the control switch responds to such tripping by opening and staying open for a relatively long period. In opening, the control switch acts to cause deenergization of the closing device and to maintain it deenergized until again closed.

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

FIG. 1 is a schematic view of one form of circuit "ice breaker embodying the invention. In FIG. 1 the circuit breaker is shown in its open position.

FIG. 2 illustrates a portion of the circuit breaker of FIG. 1 shortly after it has been tripped to open from its closed position.

FIG. 3 shows a portion of the circuit breaker of FIG. 1 in its closed position.

FIG. 4 illustrates a modified form of the invention.

;Referring now to FIG. 1, the circuit breaker shown therein comprises a set of stationary contacts 12, connected in a power line 14 and a movable bridging contact 16, movable into and out of engagement with said stationary contacts 12. The movable bridging contact 16 is secured to the left-hand end of a reciprocable operating rod 18 of insulating material, which is pivotally connected at its right hand end to a crank 20. This crank 20 is pivotally mounted on a stationary pivot 22. The movable contact 16 is biased toward its open position of FIG. 1 by means of a suitable opening spring 21, shown as a tension spring connected to the crank 20.

For transmitting closing thrust to operating rod 18 and contact 16, there is provided a conventional trip-free linkage L which comprises a pair of toggle links 23 and 24, pivotally joined together at a knee 25. One of the toggle links 24 is pivotally connected by a pivot pin 28 to the upper end of a guide link 29. This guide link 29, which is occasionally referred to herein as a trip-free member, is pivotally supported at its lower end on a fixed fulcrum 30. The pivot pin 28 carries a latch roller 31 which cooperates with a suitable trip-latch 32, which is arranged to be operated in response to predetermined circuit conditions by means of a suitable conventional tripping solenoid 34. In the disclosed embodiment, the coil of this solenoid 34 is shown connected across the secondary 35 of a current transformer inductively coupled to power line 14 so as to cause operation of the solenoid in response to overcurrents in the power line 14. Other conventional tripping schemes could, of course, be used. So long as the trip latch remains in the latched position shown in FIG. 3, toggle 23, 24 is capable of transmitting thrust to movable contact-actuating rod 18. Thus, when the knee 25 is lifted from the position shown in FIG. 1, toggle 23, 24 is extended and drives crank 20 in a clockwise direction about its pivot 22 and rod 18 to the right toward closed position against the bias of opening spring 21.

This lifting of knee 25 is produced by the action of a rotatable main cam cooperating with the usual roller 42 which is mounted at the knee 25. When main cam 4%) is rotated clockwise from its solid line position of FIG. 1 into its dotted line position of FIG. 3 by means soon to be described, it lifts knee 25, thereby extending toggle 23, 24 and closing the breaker. The position occupied by the parts of the linkage L when the breaker is in its fullyclosed position is shown in solid lines in FIG. 3. It will be apparent from FIG. 3 that closing action has resulted in the knee 25 of the toggle being driven slightly past a dead center position, i.e., past a reference line connecting the axes of pivots 28 and 27, so that there is no tendency of toggle 23, 24 to return to its retracted position of FIG. 3 when the application of closing force to roller 42 is discontinued. There is a slight tendency for toggle 23, 24 to collapse upwardly, but this is resisted by a suitable stop 44 co-acting with roller 42.

Tripping open of the circuit breaker is effected by energizing solenoid 34 sufficiently to drive trip-latch 32 clockwise about its stationary pivot 46 against the bias of a suitable reset spring 47. Should latch 32 be tripped when the circuit breaker is closed, or even during the closing stroke, the pivot 28 will be freed by such tripping action, thus no longer serving as a stationary reaction point for the toggle 23, 24. This will render toggle 23,

24 inoperative to transmit thrust to movable contact rod 18, and, as a result, opening spring 21 will be free to drive movable bridging contact 16 into its open position.

The position of the parts shortly after such tripping of latch 32 has occurred is shown in FIG. 2. The latch 32, having been moved off the latch roller 31, is no longer capable of restraining pivot 28 in its fixed position of FIG. 3. This has permitted opening spring 21 to drive crank 20 counterclockwise about its stationary pivot 22, forcing the entire toggle 23, 24 to the right. The roller 42 rolls along the stop 44 until the toggle knee 25 shifts to a position below the reference line connecting pivots 27 and 28, at which time the knee 25 of the toggle is free to move downwardly, allowing toggle 23, 24 to collapse downwardly at the knee toward its dotted line posiion of FIG. 2. Such collapse of toggle 23, 24 allows crank 22 to move further counterclockwise under the influence of opening spring 21, thus allowing for further circuitbreaker opening. A typical final position of the linkage at the end of the opening operation is shown in dotted lines in FIG. 2.

For returning the linkage L to a thrust-transmitting condition after it has been tripped open, a reset spring 49 is provided. This reset spring 49 cooperates with guide link 29 to return the guide link to its latched position of FIG. 1 after tripping has occurred. Thus, in FIG. 1, the linkage L is shown in an open and reset position.

For driving main cam 40 through a closing stroke, i.e., in a clockwise direction from its solid line position of FIG. 1 to its dotted line position of FIG. 3, an electric motor 50 is provided. This motor 50 acts to drive in a clockwise direction a rotatable shaft 54 to which main cam 40 is secured. When main cam 40 enters its dotted line position of FIG. 3 and thus completes a breaker closing operation; motor 50 is deenergized by means of a bb cutoff switch 60 (FIG. 1). This bb cutoff switch 60 is in series with the motor and opens in response to completion of a closing stroke to interrupt the motor-energizing circuit. The cam 40 will coast into its solid line position of FIG. 3 after such deenergization.

The electric control for motor 50 comprises a reclosing relay 100 that is arranged to close its contacts 85 when energized. If the circuit breaker is open, as shown in FIG. 1, closing of contacts 85 completes an energizing circuit through the motor that extends from the negative terminal 86 of the control voltage source, the contacts 85 of the reclosing relay, then through motor 50 and normallyclosed cutoff switch 60 to the positive terminal 88 of the control voltage source.

Completion of this energizing circuit causes motor 50 to drive main cam 40 clockwise from its solid line position of FIG. 1 toward its dotted line position of FIG. 3. Coincidental with this operation, an auxiliary reclosing relay 107 is energized to pick up seal-in contacts 108, completing a seal-in circuit around contacts 85 of the reclosing relay. Thus, when reclosing relay 100 drops out (as soon to be described), motor 50 remains energized through seal-in contacts 108. When the motor drives the main cam 40 into its dotted line position of FIG. 3, cut-ofi? switch 60 opens, thereby normally deenergizing the motor 50, as described hereinabove.

For establishing an energizing circuit for the reclosing relay 100, there is provided a closing control switch 110 that is operable either manually or by suitable means capable of producing automatic reclosing of the main circuit breaker. This closing control switch 110 is connected in a circuit 111 that extends from the positive terminal of the control voltage source, through the closing control switch 110, an anti-pump device 112, a "b switch 114 sensitive to position of the breaker, and the coil of reclosing relay 100 to the negative terminal of the control voltage source. When the closing control switch 110 is closed, it completes this energizing circuit 111, thereby picking up reclosing relay 100 and initiating motor operation. Motor 50 begins the breaker-closing operation and as the breaker approaches closed position, the [2 switch 114 opens, interrupting this operation-initiating circuit 111 and dropping out reclosing relay 100. The motor operation continues, however, because the seal-in circuit through the contacts 108 of the auxiliary reclosing relay are closed. When motor 50 has substantially completely closed the breaker, cut-off switch 60 opens to deenergize the motor, as previously described.

The anti-pump device 112 serves to prevent inadvertent repetitive closing operations shouldclosing control switch 110 be held closed when the breaker trips open upon being closed on a fault. This device 112 serves to maintain the closure-initiating circuit 111 open after it has produced one circuit-breaker closing, so long as the closing control switch 110 is held closed. This anti-pump device 112 may be of any suitable conventional form, such as, for example, that shown in U.S. Patent 2,381,336, Coggeshall, assigned to the assignee of the present invention.

If the circuit breaker should be closed while there is a fault present on power line 14, a so-called trip-free operation will occur. That is, tripping device 34 will immediately trip latch 32, allowing linkage L to collapse, thereby permitting opening spring 21 to open the circuit breaker, as described hereinabove. When the circuit breaker enters its fully closed position during such a closing operation, bb cut-off switch 60 will open, but it will immediately reclose in response to the immediatelyfollowing circuit-breaker opening. It was found in prior designs of this mechanism that during certain of these trip-free operations, the bb cut-off switch 60 did not stay open long enough to permit the auxiliary reclosing relay 107 to drop out and interrupt the motor circuit by opening its contacts 108. As a result, the motor stayed energized and undesirably attempted another closing operation.

To assure that the auxiliary reclosing relay 107 will drop out in response to a circuit-breaker closing operation, even if it is immediately followed by opening, I provide a control switch in series with the operating coil of the auxiliary reclosing relay 107 and in shunt with motor 50. This control switch 120 is operated by motion of the guide link 29, which may be thought of as a trip-free member. Should the guide link 29 stay in its normal position of FIGS. 1 and 3, the control switch 120 will remain closed. But should the trip latch 32 be tripped, the control switch 120 will open and will be held open until the guide link 29 is reset. More specifically, if the trip latch 32 is tripped, guide link 29 will move from its normal position of FIG. 3 through its solid line position of FIG. 2 into its dotted line position, thereafter returning to its normal position of FIG. 1. While the guide link 29 is out of its normal position, the spring 121 on the control switch 120 will open the control switch 120 and will maintain it open until the guide link 29 returns to its normal position, reclosing the control switch 120 against the bias of spring 121.

A relatively long period of time is required for guide link 29 to reset following a tripping operation. In one embodiment of the invention, the circuit breaker can move its contacts from a fully-closed position to a fully-open position in 20 milliseconds following tripping of latch 32, but approximately 35 milliseconds is required for guide link 29 to reset following latch-tripping. Thus, when the circuit breaker is tripped immediately following a closing operation, control switch 120 opens and stays open for approximately 35 milliseconds. This results in the energizing circuit for auxiliary reclosing relay 107 being interrupted for approximately 35 milliseconds, thereby providing an ample opportunity for auxiliary reclosing relay 107 to drop out and interrupt the motor-energizing circuit with its contact 108.

It will be seen that the control switch 120 effectively backs up the bb cut-off switch 60, which normally effects deenergization of the motor 50 at the end of a closing stroke. Even though a trip-free operation might result in this cut-oil switch 60 staying open for too short a period to drop out the auxiliary reclosing relay 107, the auxiliary relay will nevertheless be dropped out as desired since the auxiliary switch 120 will remain open for approximately 35 milliseconds. This affords an ample opportunity for drop-out of the auxiliary reclosing relay 107 thus assuring against unwanted continued energization of the motor 50. Upon reset of guide link 29, auxiliary switch 120 recloses to restore the system to the position of FIG. 1.

It is significant that the auxiliary switch 120 is located in shunt with motor 50. In this location, switch 120, upon opening, acts to prevent auxiliary reclosing relay 107 from being maintained in its energized position by current supplied from motor 50 acting as a generator after its deenergization at the end of a closing operation. Had the auxiliary reclosing relay 107 been permitted to remain in its energized position while the auxiliary switch 120 was open, the motor could be re-energized upon reclosing of the auxiliary switch when guide link 29 resets (assuming a trip-free operation).

There are other types of control schemes that rely upon a control switch that must be momentarily operated in response to circuit-breaker opening and must remain in its operated position for a relatively long period, resetting at the end of this period. Special mechanisms are available for providing the desired momentary operation of such control switches but these mechanisms are relatively expensive and are usable only with circuit breakers that consume a relatively long time period in opening.

By operating such control switches ofi the guide link 29, I can provide the desired momentary operation of the control switch without such expensive mechanisms and even though the circuit breaker can open in a very short time. As already mentioned hereinabove, in one typical circuit breaker, the resetting operation of guide link 29 requires 35 milliseconds as compared to the 20 milliseconds needed for opening of the circuit breaker. A control switch operated off the guide link of such a breaker can thus be held in its operated position for almost 35 milliseconds, despite the 20-millisecond opening time of the breaker.

FIG. 4 shows a normally-open control switch 120a that closes in response to tripping of the circuit breaker and remains closed until the guide link 29 is reset as above described. Such a control switch can be used, for example, to initiate the reclosing of another circuit breaker which requires a momentary signal of a relatively long duration to operate properly.

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

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

1. An electric circuit breaker comprising:

(a) a first contact,

(b) a second contact movable into and out of engagement with said first contact,

(c) motive means for supplying closing force for driving said second contact into engagement with said first contact,

(d) a mechanically trip-free mechanism through which closing force is transmitted from said motive means to said second contact,

(e) said mechanism comprising a trip-free member which when held in a normal position renders said mechanism capable of transmitting closing force to said second contact but which when released renders said mechanism incapable of transmitting closing force to said second contact, and means for automatically resetting said trip-free member to said normal position after release thereof,

(f) main cut-oil means responsive to closing of said circuit breaker for interrupting energization of said motive means when said second contact reaches a substantially fully-closed position,

(g) and auxiliary cut-01f means responsive to the position of said trip-free member for preventing continued energization of said motive means while said trip-free member is out of its normal position,

(h) said auxiliary cut-off means comprising a control switch and means for operating said control switch from a non-operated to an operated position when said trip-free member moves out of its normal position and for resetting said control switch to its nonoperated position in response to reset of said tripfree member to its normal position.

2. The circuit breaker of claim 1 in which: said auxiliary cut-off means comprises an auxiliary reclosing relay having contacts in series with said motor for controlling energization of said motor and a coil connected in shunt with said motor for causing said relay contacts to close when said coil is energized, means for opening said relay contacts when said coil is deenergized to prevent further energization of said motor, said control switch being connected in series with said coil and being arranged to open when in its operated position.

3. The circuit breaker of claim 2 in which said control switch is connected in shunt with said motor.

4. Electrical apparatus comprising:

(a) a circuit breaker comprising:

(i) a first contact,

(ii) a second contact movable into and out of engagement with said first contact,

'(iii) motive means for supplying closing force for driving said second contact into engagement with said first contact,

(iv) a mechanically trip-free mechanism through which closing force is transmitted from said motive means to said second contact,

(v) said mechanism comprising a trip-free member which when held in a normal position renders said mechanism capable of transmitting closing force to said second contact but which when released renders said mechanism incapable of transmitting closing force to said second contact, and means for automatically resetting said trip-free member to said normal position after release thereof,

(b) a control circuit operable in response to opening of said circuit breaker but non-responsive to closing of said circuit breaker, said control circuit comprising a normally-open control switch, said control circuit being of such a nature that its normal operation requires that said control switch be momentarily closed for a relatively long period compared to the period consumed by circuit breaker opening,

(0) and means responsive to the position of said tripfree member for closing said control switch when said trip-free member moves out of its normal position and for reopening said control switch in response to reset of said trip-free member into its normal position.

References Cited UNITED STATES PATENTS 2,034,145 3/1936 Linde 335-76 3,113,191 12/1963 Frank 33573 BERNARD A. GILHEANY, Primary Examiner.

R. COHRS, Assistant Examiner.

Claims (1)

1. AN ELECTRIC CIRCUIT BREAKER COMPRISING: (A) A FIRST CONTACT, (B) A SECOND CONTACT MOVABLE INTO AND OUT OF ENGAGEMENT WITH SAID FIRST CONTACT, (C) MOTIVE MEANS FOR SUPPLYING CLOSING FORCE FOR DRIVING SAID SECOND CONTACT INTO ENGAGEMENT WITH SAID FIRST CONTACT, (D) A MECHANICALLY TRIP-FREE MECHANISM THROUGH WHICH CLOSING FORCE IS TRANSMITTED FROM SAID MOTIVE MEANS TO SAID SECOND CONTACT, (E) SAID MECHANISM COMPRISING A TRIP-FREE MEMBER WHICH WHEN HELD IN A NORMAL POSITION RENDERS SAID MECHANISM CAPABLE OF TRANSMITTING CLOSING FORCE TO SAID SECOND CONTACT BUT WHICH WHEN RELEASED RENDERS SAID MECHANISM INCAPABLE OF TRANSMITTING CLOSING FORCE TO SAID SECOND CONTACT, AND MEANS FOR AUTOMATICALLY RESETTING SAID TRIP-FREE MEMBER TO SAID NORMAL POSITION AFTER RELEASE THEREOF, (F) MAIN CUT-OFF MEANS RESPONSIVE TO CLOSING OF SAID CIRCUIT BREAKER FOR INTERRUPTING ENERGIZATION OF SAID MOTIVE MEANS WHEN SAID SECOND CONTACT REACHES A SUBSTANTIALLY FULLY-CLOSED POSITION, (G) AND AUXILLIARY CUT-OFF MEANS RESPONSIVE TO THE POSITION OF SAID TRIP-FREE MEMBER FOR PREVENTING CONTINUED ENERHIZATION OF SAID MOTIVE MEANS WHILE SAID TRIP-FREE MEMBER IS OUT OF ITS NORMAL POSITION,

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