US2381336A - Control of electric switches - Google Patents

Description

Aug 7, 1945. T. R. COGGESHALL. 3 9

CONTROL OF ELECTRIC SWITCHES Filed Nov. 29, 1945 Fig. I.

His Attorney.

Patented Aug. 7, 1945 CONTROL OF ELECTRIC SWITCHES Thellwell R. Coggeshall, Bala Cynwyd, Pa., assignor to General Electric Company, a corporation of New York Application November 29, 1943, Serial No. 512,179

11 Claims.

My invention relates to improvements in the. control of electric switches and more particularly circuit breakers, and especially circuit breakers whose operating mechanisms are fluid pressure actuated and are not inherently tripfree.

Some fluid pressure actuated circuit breaker operating mechanisms are not trip-free as long as the fluid pressure actuating means is energized. This is more or less immaterial provided the circuit controlled by the circuit breaker In accordance with my invention, I provide, for

' a fluid pressure actuated circuit breaker, an imis normal at the time the closing operation is performed. In usual operation, however, the circuit breaker is opened in response to a fault. In order to restore service, it is important that the circuit breaker be reclosed as quickly as possible. Usually, at least two reclosures are attempted. Obviously, in order to avoid damage to the circuit breaker and connected apparatus, the circuit breaker, must be free to open whenever it is closed on a faulty circuit. It is, therefore, necessary that the fluid pressure operated proved trip-free and pump-free control arrangement embodying a valve operating means and control therefor for quickly deenergizing the fluid pressure actuating means when the circuit breaker is closed and regardless of the condition of the circuit at the time of closure of the circuit breaker. Further in accordance with my invention, I provide, for a fluid pressure actuated circuit breaker, an improved control arrangement whereby successive reclosures of the circuit breaker on a faulty circuit cannot be accomplished by the operator without premeditated action on his part after each reclosure.

My invention will be better understood from the following description when considered in cononly one closure of the circuit breaker. In other means either in response to the mere closing ofthe circuit breaker while thecircut is normal or in response toabnormal circuit conditions at the time the circuit breaker isclosed. A further object of my invention is to provide an improved circuit breaker control arrangement embodying a minimum number of auxiliary relays and the like o as to expedite the deenergizihg action of the fluid pressure actuating means. these and other objects of my'invention will appear in more detail hereinafter.

appended claims.

In the accompanying sheet of drawings, Fig.

'l'diagrammatically illustrates a switch control arrangement embodying my invention and Fig. 2 diagrammatically illustrates modification of a part of the embodiment of my invention shown in Fig. 1.

In Fig. 1 of the accompanying-sheet oi drawings, I have illustrated an embodiment of my invention in a control arrangement for an electric switch such as a circuit breaker l whose operating mechanism 2 is fluid pressure actuated to close the circuit breaker. The circuit breaker l is schematically illustrated as a three-pole switch which is biased to the circuit open position by suitable means indicated as a, spring 3. Also, the circuit breaker is illustrated as arranged to control a circuit comprising conductors 4, 5 and 6. As shown in elevation; the operating mechanism 2 is :of the roller toggle type disclosed and claimed in a copending application of Nelson H. Westervelt, Serial No. 512,185, filed concurrently herewith and assigned to the assignee of the present application. This operating mechanism comprises an operating lever I and an operating crank 8. The lever I is mounted on the stationary pivot 9 and pivotally connected at It to, a, circuit breaker operating rod ll, indicated schematically in part by the dash-dot line H. For actuating the lever 'l clockwise to close they circuit breaker l, the operating crank 8 is mounted on a stationary pivot l3 and provided at its free end with a'roller ll mounted on a pin I5. The roller ll engages the roller l6 mounted on a pin I! in the end of the operating lever I opposite itsattachment to the operating rod I l. t

For holding the operating mechanism 2 in the switch closed position illustrated, there is provided a prop or latch iI which. as shown, is mounted on a stationary pivot II, and, for reduction of friction load is arranged to engage a second roller mounted on the pin II and similar to the roller II. It will be obvious that the operating mechanism described is free to collapse upon a predetermined counterclockwise movement of the prop II and thereby to allow the opening of the circuit breaker provided there is no support or force against the roller II to hold it in the illustrated position when the prop II is moved out of holding engagement with its mociated roller.

For actuating the prop II in the'tripping direction counterclockwise .as illustrated, suitable electromagnetic means comprising a winding II is provided. As shown, the tripping winding 2| is arranged to be energized in response to the operation of a protective relay 2| or a tripping control switch 22. The protective relay II is illustrated simply as. an overcurrent relay connected to be energized from a current transformer II in the circuit conductor 4. It will be understood, ot course, that any number or relays may be employed in accordance with the art of circuit protection. Also as shown, the circuit of the winding II, which includes conductors II and II, may also include the contacts II of a cir cuit breaker a auxiliary switch which is closed when the circuit breaker is closed and open when the circuit breaker is open.

For actuating the operating mechanism I to close the circuit breaker I. I provide fluid pressure actuated means comprising a cylinder 11 within which is slidably mounted a piston II carrying a piston rod 29. This rod, on its upstroke under the admission of fluid under pressure beneath the piston II, engages the roller II whereby to move the crank I clockwise until the parts of the operating mechanism 2 are positioned as shown in the drawing with the circuit breaker I closed. The prop II, unless its winding II is energized, drops in under its associated roller to hold the circuit breaker closed after the piston rod It returns to its lower position. While any suitable fluid may be provided to raise the piston II, it is usual to use air under the desired pressure in a receiver or tank Ill from which the air is supplied to the cylinder 21 through control valve means II embodying my invention. On the upstroke oi the piston II,

suitable energy storing means, such as springs II, are compressed to eilect the down or return stroke of the piston II to the lower position dump valve II, the air under pressure opens an admission valve II mounted in the head of the dump valve 33 to uncover ports therein for the admission of air to the cylinder 21. The admission valve II is biased to the closed position by a spring 31 which becomes so compressed that when air is subsequently exhausted from the space II, the valve II quickly closes the ports in the dump valve II, which then more eliectively moves to uncover the ports IL In accordance with my invention, the control valve means II is electromagnetically actuated, and, as shown, it is or the pilot diilerential type embodying a pilot valve II and a main valve means such as a piston valve II. Also. as shown, it includes an exhaust valve II for release oi air to atmosphere from behind the dump valve II and from the delivery portion ll oi the valve body. For pressure equalization on the inlet side oi the valve II, the main valve II is provided with a bleed hole '42. The pilot valve II seats on the upper side oi! the main valve II, where it is maintained .closed by the entrapped pressure above it. This pilot valve is raised against the bias of suitable energy storing or valve closing means, such as a kick-oil spring II.

For opening the pilot valve II, I provide electromagnetic means comprising an armature II, a magnetic housing II, a pole piece comprising magnetic elements II, I1 and II, and a valve opening winding II. As illustrated, the electromagnetic means is of the plunger and solenoid type with the armature II suitably connected to the valve II as by a rod II. In'order to hold 85 the armature II in the attracted position after shown. This downstroke operation follows the cutting oi! oi the air supply by the control valve Ii so that the ,air in the cylinder 21 can be quickly exhausted to atmosphere through the medium of a dump valve II which uncovers an exhaust port II. This dump valve is disclosed.

and claimed in my copending application, Serial No. 512,180, flied concurrently herewith and assigned to the assignee of the present application.

In order to avoid pressure above the piston It on the upstroke and also to have it return freely under the bias of the springs II. the cylinder II through the valve Ii to the back or the dump valve II. This valve II moves to the left against the bias of a spri g Iland closes the exhaust "port I. coincidentally with the closing of the it is moved to this position, the pole piece magnetic element 4] is, in accordance with my invention, of permanently magnetic material, examples of which are well known to the art. Thus. it may be of the permanently magnetic alloy type known as Alnico. The prevailing pressure above the valve II in consequence oi the bleed hole I2 keeps this valve closed. However, when the pilot valve II is opened in response to the attraction oi the armature II, this pressure is exhausted to the low pressure space Ii and to the atmosphere through exhaust ports II of the exhaust valve II. The excess of pressure is therefore shifted from above the main valve II to below it so that it is lifted against the bias of a spring II which tends to-move the armature II to the unattracted position. Simultaneously with the opening of the main valve II, the exhaust valve 40, which is held open by the main valve 39 pressing on the hollow stem II of the valve I0 against the bias of a spring II, is permitted to close and thus seal the outlet or delivery portion II o! the control valve II against loss to atmosphere. The hollow stem II oi! the exhaust valve II is provided with one or more equalizing exhaust ports II and an uplift piston II.

For closing the circuit breaker i, I provide, in accordance with my invention, a closing control circuit for the valve opening winding II. As shown, this circuit includes a closing control switch II, the contacts." of a minimum pressure switch II which opens when the pressure in the tank II falls'below a predetermined minimum value, a conductor II, b auxiliary switch contacts II oi the circuit breaker l, a conductor II, the contacts I! or a short time delay circuit opening relay II whose winding'II is energized upon closure of the closing control switch II, a conductor II, the valve opening winding II,

and a conductor 88. The opening of the circuit breaker closing control circuit by the slightly delayed contacts 62 of the relay 83 insures a positive opening of the control valve 3| in response to the energization of its winding 48 and also prevents reclosure of the circuit breaker as long as the control switch 56 is kept closed. In other words, with a single closure of the control switch 58, only one closure of the circuit breakerfl can be effected.

In accordance with my invention, I provide means for quickly returning the piston 28 to the down position shown because the circuit breaker mechanism 2, although of itself inherently triptree, cannot move to the open circuit position as long as air pressure below the piston 28 keeps the piston rod 29 pressing against roller I4 with enough force to maintain the mechanism 2 with its parts positioned as shown in the drawing. For this purpose, I provide means for effecting the closure of the valve means 3| to cut off the pressure supply at the end of the piston stroke when the circuit breaker is fully closed. As shown, this means comprises a valve closing winding 61 so wound and connected to be energized that its polarity is opposite to the polarity of the opening winding 49 and is such as to neutralize the holding flux of the permanent magnet 47 whereby to release the plunger 44 for the valve closing movement. In order to insure the energization of the valve closing winding 61 at the proper moment, the circuit of this winding is controlled by a limit switch 68 which is actuated to the closed position in response to the movement of the piston 28 so as to close its contacts 69 in the circuit of the winding 61 when the breaker is fully closed. As shown, the circuit of the valve closing winding 61 includes the contacts 69 of the cutoff or limit switch 68, the conductor 10, and the valve closing winding 61.

Also in accordance with my invention, in order to insure a'fast or earlier opening of the circuit breaker I when it is closed during an abnormal circuit condition, I provide means for substantially simultaneously tripping the circuit breaker and effecting the closing of the valve means 3|. As shown, this means comprises a valve closing winding H which is independent of the winding 51 and which is wound and connected to be energized to have a polarity such as to neutralize the magnetic holding effect of the permanent magnet 41 whereby to release the plunger 44 to close the valve 3| and the trip circuit comprising the tripping winding of the circuit breaker mechanism. The circuit for the closing winding Assuming the parts as positioned in the drawing, then when closure of the contacts of the relay 2| or the control switch 22 is effected, the circuit of the trip coil 20 is energized to move the latch |8 to the releasing position. The circuit breaker I is then opened by the bias of the spring 3. The circuit breaker is, of course, free to open without opposition from the piston 28 which returned to its lower position at the end of the preceding closing operation. At the same time that the trip coil 20 is energized, the valve closing winding H is also energized, but since the valve 39 is already closed, nothing happens at this time in consequence of this energization.

Upon the opening of the circuit breaker, the a auxiliary switch contacts 26 are opened and the -b auxiliary switch contacts 60 are closed. When it is desired to close the circuit breaker, the control switch 38 is closed, and if the pressure in the tank 30 is suiiicient to maintain the low pressure interlock switch contacts 51 closed, then the circuit of the opening winding 49 is completed and will be maintained until the short time delay circuit opening relay 63 opens its contacts 82. Upon energization of the valve opening winding 49, the armature 44 is moved to the attracted position. During this movement it opens the pilot valve 38 and thereby exhausts pressure to air by way of the outlet portion 4| and the ports 40 of the valve 3| and thus effects the opening oi the main valve 38 and the closing of the exhaust valve 40. Admission of air under pressure back of the dump valve 33 seats this valve against the bias of the spring 35 whereupon its associated admission valve 36 is opened against the bias of its spring 31. This admits air under pressure below the piston 28, which is thus caused to travel upward against the bias of the spring 32 to engage the roller l4 and the crank 8 and thereby turn this crank and the operating lever l1 clockwise until the prop latch I8 is free to fall under the roller and maintain the circuit breaker I in the closed position.

As soon as the piston 28 reaches the end of its upstroke with the breaker fully closed, the limit switch 68 closes its contacts 69 thereby completing the circuit of the valve closing or neutralizing winding 61. With the neutralization of the holding effect of the permanent magnet 41, the plunger armature 44 is rapidly actuated under the bias of springs 43 and 5| to the unattracted position to effect the closing of the pilot valve 38 and the main valve 39 whereby to shut off the supply of air to the cylinder 21. At the same time, the exhaust valve 40 is opened and the pressure back of the-dump valve 33 relieved so that this valve can open under the bias of its spring 35 to dump the air in the cylinder through exhaust port 34. With the quick release of the piston rod 29 from its holding position under the roller M, the circuit breaker operating mechanism is restored to its inherently trip-free condition.

If the breaker is closed on a faulty circuit, the operation of a protective relay, such as the overcurrent relay 2|, or other tripping means, such as the switch 22, is immediately effective to cause the opening of the circuit breaker. In fact, if during the closing operation, current above the pick-up value of the relay 2| flows in the circuit 4, 5, 6 upon the initial touching of the circuit breaker contacts before the operating mechanism is fully latched, the completion of the circuit of the neutralizing closing winding H by the closing of the contacts of the relay 2| is effective to cause the closing of the valve means 3| somewhat in advance of the operation of the limit switch which controls the closing winding 61'. It will accordingly be clear that the circuit breaker operating mechanism is maintained in its inherently trip-free operating condition except for the brief time necessary to effect the closing of the valve means 3| while the piston rod 29 is in contact with the roller I 4 in its upper or closing position. Moreover, since the trippng or closing action of the valve means 3| is efiected without the action of auxiliary relays, the closing time of this valve means is very short.

In automatic. station applications, and also when the control switch 56 is of the stay-put type, it may be desirable to have the energization of the short time delay relay 63 controlled independently of the minimum pressure switch II, as shown, for example, in Fig. 2. In this figure, the energizing circuit of the relay 8! includes the control switch 86 and a conductor 59' without passing through the contacts 51 of the minimum pressure switch 58. With this arrangement, it will be clear that if the control switch It is closed when the minimum pressure switch it is open, the relay will be energized to open its contacts 62 and will remain energized with these contacts open as lon as the control switch II is left closed. Then, if the control switch 56 is closed and left closed while the minimum pressure switch is open, mere subsequent return of pressure cannot effect a closing operation of the circuit breaker, which might happen at an inadvertent time to cause damage or even loss of life to operating personnel.

While I have shown and described my invention in considerable detail, I do not desire to be limited to the exact arrangements shown, but seek to cover in the appended claims all those modifications that fall within the true spirit and scope of my invention.

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

1. In a control arrangement for an electric switch provided with fluid pressure actuated closing means arranged to be energized through electromagnetically actuated valve means from a source of fluid under pressure, a control circuit for eflecting the opening of said valve means, a control switch in said circuit, means connected to be energized upon closure of said control switch for opening said control circuit a predetermined time thereafter, magnetic means for holding said valve means open, electromagnetic means for neutralizing the effect of said holding means, and means for effecting the energization of said neutralizing means during the closing of said electric switch.

2. In a control arrangement for an electric switch provided with means for holding the switch closed and also with a fluid pressure actuated closing means arranged to be energized through electromagnetically' actuated valve means from a source of fluid under pressure, a control circuit for effecting the opening of said valve means, a control switch in said circuit, means connected to be energized upon closure of said control switch for opening said control circuit a predetermined time thereafter, magnetic means for holding said valve means open, electromagnetic means for neutralizing the effect of said valve holding means, means dependent on the completion of the action of the fluid pressure actuated means for effecting the energizetion of said neutralizing means, and means for substantially simultaneously effecting the energization of said neutralizing means and the release of said switch holding means.

8. In a control arrangement for an electric switch provided with means for holding the switch closed and also with a fluid pressure actuated closing means arranged to be energized from a source of fluid under pressure, means Ior controlling the flow or fluid from said source to said actuated means and from said actuated means comprising an electromagnetically actuated valve provided with an armature movable to the attracted position to open the valve, energizing winding means for effecting movement of the armature to the attracted position, magnetic means for holding the armature in the attracted position, winding means for neutralizing the holding effect of said magnetic means, a control switch, a control circuit including said control switch and said energizing winding means, a time delay circuit opening relay having its contacts in said control circuit and an actuating winding connected to be energized upon closure of the control switch, and means dependent on the completion of the action of the fluid pressure actuated means for effecting the energization of said neutralizing winding means.

4. In a control arrangement for an electric switch provided with means for holding the switch closed and also with a fluid pressure actuated closing means arranged to be energized from a source of fluid under'pressure, means for controlling the flow of fluid from said source to said actuated means and from said actuated means comprising an electromagnetically actuated valve provided with an armature movable to the attracted position to open the valve, energizing winding means for effecting movement of the armature to the attracted position, magnetic means for holding the armature in the at tracted position, winding means for neutralizing the holding effect of said magnetic means, a control switch, a control circuit including said control switch and said energizing winding means, a time delay circuit opening relay having its contacts in said control circuit and an actuating winding connected to be energized upon closure oi. the control switch, means dependent on the completion of the action of the fluid pressure actuated means for effecting the energization of said neutralizing winding means, and means for substantially simultaneously effecting the energization of said neutralizing winding means and the release of said switch holding means.

5. In trip-tree and pump-free control arrangement for an electric circuit breaker provided with pneumatically actuated closing means arranged to be energized from a source of air under pressure, means for controlling the flow of air from said source to said actuated means and from the actuated means to atmosphere comprising an eletromagnetically actuated valve provided with an armature movable to the attracted position to open the valve, a valve opening winding operative when energized to effect movement of the armature to the attracted position, a permanent magnet for holding the armature in the attracted position, a valve closing winding operative when energized to neutralize the holding effect of said permanent magnet, a control switch, a control circuit including said control switch and said valve opening winding, a time delay circuit opening relay having its contacts in said control circuit and an actuating winding connected to be energized upon closure of the control switch, and means dependent on the completion of the action of the pneumatically actuated means for effecting the energization of said valve closing winding.

6. In trip-free and pump-free control arrangement for an electric circuit breaker provided with fluid pressure actuated closing means arranged to be energized from a source of fluid under pressure, means for controlling the flow of fluid from said source to said actuated means and from said actuated means comprising an electromagnetically actuated valve provided with an armature movable to the attracted position to open the valve, a winding operative when energized to effect movement of the armature to the attracted position, magnetic means for holding the armature in the attracted position, winding means operative when energized to neutralize the holding effect of said magnetic means, a control switch, a control circuit including said control switch and said operating winding, a time delay circuit opening relay having its contacts in said control circuit and an actuating winding connected to be energized upon closure of the control switch, means dependent on the completion of the action of the fluid pressure actuated means for effecting the energization of said winding means, and means for substantially simultaneously tripping the circuit breaker and effecting the energization of said winding means.

7. In trip-free and pump-free control arrangement for an electric circuit breaker provided with pneumatically actuated closing means arranged to be energized from a source of air under pressure, means for controlling the flow of air from said source to said actuated means and from the actuated means to atmosphere comprising an electromagnetically actuated valve provided with an armature movable to the attracted position to open the valveya valve opening winding operative when energized to effect movement of the armature to the attracted position, a permanent magnet for holding the ar-.

mature in the attracted position, valve closing winding means operative when energized to neutralize the holding efiect of said permanent magnet, a control switch, a control circuit including said control switch and said valve opening windin a time delay circuit opening relay having its contacts in said control circuit and an actuating winding connected to be energized upon closure of the control switch, means dependent on the completion of the action of the pneumatically actuated means for efieoting the energization of said valve closing winding means, and means for substantially simultaneously tripping the circuit breaker and efiecting the energization of said valve closing winding means.

8. In a control arrangement for an electric switch provided with fluid pressure actuated closing means arranged to be energized from a source of fluid under pressure, valve means comprising a member movable in one direction to a predetermined position to control the flow of fluid from said source to said actuated means and in the opposite direction from said position to control the flow of fluid from said actuated means, means for eii'ecting the movement of said member in said one direction to said predetermined position, means tending to move said member in the opposite direction, means for holding said member in said predetermined position'against the effect of said motion tending means; and means for neutralizing the efiect of said holding means during the closing operation of said electric switch.

9. In a control arrangement for an'electric switch provided with means tor holding the switch closed and also with fluid pressure actuated closing means arranged to be energized from a source of fluid under pressure, valve means comprising a member movable in one direction to a predetermined position to control the flow of fluid from said source to said actuated means and in the opp site direction from said position to control the flow of fluid from said actuated means, means for effecting the movement of said member in said one direction to said predetermined position, means tending to move said member in the opposite direction, means for holding said member in said predetermined position against the efiect of said motion tending means, means for neutralizing the effect of said holding means during the closing operation of said electric switch, and means for substantially simultaneously neutralizing the efiect of said member holding means and the release of said switch holding means.

10. In a control arrangement for an electric switch provided with fluid pressure actuated closing means arranged to be energized from, a source of fluid under pressure, electromagnetically actuated valve means comprising an armature movable to the attracted position to control the flow of fluid from said source to said fluid pressure actuated means and to the unattracted position to control the flow of fluid from said fluid pressure actuated means, a control circuit for effecting the energization of said electromagnetically actuated valve means to move said armature to the attracted position, a control switch in said control circuit, means connected to be energized upon closure of said control switch for subsequently opening said control circuit, means tending to move the armature to the unattracted position, magnetic means for holding the arma ture in the attracted position after the opening of the control circuit, magnetic means for neutralizing the efiect of said holding means, and means for effecting the energization of said neutralizing means during the closing of said electric switch.

11. In a control arrangement for an electric switch provided with fluid pressure actuated closing means arranged to be energized through electromagnetically actuated valve means from a source of.fluid under pressure; a control circuit for efiecting the opening or said valve means, a control switch in said circuit, means connected to be energized upon closure of said control switch for opening said control circuit at predetermined time thereafter, magnetic means for holding said valve means open, electromagnetic means for neutralizing the effect of said holding means, and means for effecting the energization of said neutralizing means within the region of the closed position of said fluid pressure actuated closing means.

THEILWELL R. COGGESHAIL.

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