US2620382A - Automatic reclosing circuit breaker - Google Patents

Description

Dec. 2, 1952 VAN RYAN 2,620,382

AUTOMATIC RECLOSING CIRCUIT BREAKER Filed Feb. 2, 1951 ANTHONY VAN RYAN hive-Y Patented Dec. 2, 1952 AUTOMATIC RECLOSING CIRCUIT BREAKER Anthony van Ryan, South Milwaukee, Wis., assignor to McGraw Electric Company, Milwaukee, Wis., a corporation of Delaware Application February 2, 1951, Serial No. 209,004

6 Claims.

This invention relates to electrical circuit breakers, and particularly pertains to circuit breakers of the reclosing type.

The dvantages of using reclosing circuit breakers have become increasingly apparent, especially with reference to the power distribution field. It is well-known that a greater percentage of line faults are of a temporary nature requiring only momentary line current interruption for the clearing of these faults. 'Io require a re-fusing operation after each occurrence of a fault of a temporary nature would impose a needless burden on utilities.

Various protective devices have been invented to automatically provide current interruption on the occurrence of a line fault. In general, these devices have incorporated integrating devices for actuating contact lockout mechanisms after a predetermined number of reclosing operations where the fault is of an enduring nature. In the past, reclosing circuit breakers were designed to open on occurrence of loads in excess of predetermined values and reclose a predetermined number of times determined by the operations of these integrating mechanisms, permanently opening the main line contacts after a predetermined number of these reclosing operations. Reclosure of the main line contacts under load conditions, and especially under heavy overload, imposed a severe duty on equipment and particularly the arcing contacts. In addition, reclosure under load subjected the power line and line equipment to possible serious damage.

It is therefore a primary object of this invention to provide a reclosing circuit breaker for either D. C. or A. 0. operation which opens the circuit on occurrence of a load in excess of a predetermined value, closing the contacts of an auxiliary circuit after time delay thereby permitting the flow of a limited amount of current at line potential to determine whether the condition of overload is still in existence; and to either reclose the main line contacts or retain them in open position, opening the auxiliary circuit contacts as well, depending upon the magnitude of the load resistance or impedance.

It is a specific object of this invention to provide a reclosing circuit breaker which automatically determines the existence of a permanent line fault without the necessity of subjecting the protected equipment to continued re-application of power current and without the requirement of integrating or counting devices, and which is provided with an auxiliary probing circuit including a current limiting impedance and normally open auxiliary contacts actuated by operation of normally closed main contacts which are designed to be opened under either temporary or permanent line fault conditions, the auxiliary circuit also including lockout means for opening all contacts under certain fault conditions.

Further objects are to provide a, circuit breaker having the above enumerated characteristics in which a delayed action means is provided for the closure of the main contacts during which period the auxiliary circuit contacts are closed to test or probe the circuit, the auxiliary circuit contacts also being retarded toward closure by a time delay means to provide time for any arcing conditions to clear.

In the single diagrammed drawing of the novel circuit breaker, reference character I refers to the main movable contact adapted to cooperate with stationary contacts 2, and arranged in one side of the power line 3, 4. The load lines are illustrated by the reference characters 6 and 1.

The movable contact I is normally in electrical engagement with the stationary contacts 2 to complete the electrical power circuit to the load. Power is supplied through a series connected main circuit interrupting solenoid coil 8 which operates the armature 9 to disengage the contacts I and 2 on the occurrence of predetermined overload conditions. The armature 9 is attached to one end of an extension or rod 10, the opposite end of the rod being pivotally fastened to a rocker arm II. A tension spring l2 may be used to bias the contacts toward closed position, although it is conceivable that gravitational forces acting on the combined mass of the contact I and armature 9 may be utilized for this purpose.

An auxiliary movable contact is indicated by the reference character I5, and is adapted to cooperate with stationary contacts Hi. The normally open auxiliary movable contact I5 is positioned to be actuated by the operation of the main solenoid rmature 9 through the rocker arm H. A time delay means, freely movable in an upward direction and designated generally at ll, is provided to delay closure of the main contacts I and 2 after opening under overload. An auxiliary time delay, also freely movable upwardly and designated generally at 18, is provided for the auxiliary movable contact l5, retarding closure of the auxiliary contacts I5 and [6 as will be hereinafter described. Both time delays I! and It! may be conveniently in the form of dashpots as shown, or any of a number of well-known devices.

A lost-motion, resilient device is provided for the auxiliary contact in any of many wellknown forms, and may be in the form diagrammed, wherein energy may be stored in a compression spring [9. This potential energy is introduced from the rocker arm H to a pin pivotally attached thereto. A flange 2| on the pin 2!] acts as a stop for the spring 19. The opposite end of the spring l9 rests on the dashpot plunger 22 of the auxiliary time delay l8. A supporting sleeve 23, attached to the plunger 22, receives the pin 20. The sleeve 23 is provided with a slotted portion 24 receiving the cars 25 of pin 20.

An extension or rod 26 is attached to the plunger 22 and supports the auxiliary movable contact [5. Stops 2! and 28 are provided for the rods 26 and ID, respectively, for a purpose hereinafter described.

A lockout solenoid winding 30 is in series connection with the auxiliary circuit designated by the reference character 31. A current limiting resistance, or impedance, 32 is provided for the auxiliary circuit 3|, which may be separate or as an integral part of the solenoid winding 30.

The lockout solenoid winding actuates an armature 33 in a downward direction under certain predet rmined conditions to be described. The armature 33 may be pivotally attached to an L-shaped cam 34, which also acts as a stop for the lockout lever arm 35 normally preventing lockout. A tension spring 36 is preferably provided to bias the cam. towards stop position, further counterclockwise movement being prevented by a stop 31. The spring 36 may also be attached at the opposite end to the lever arm 35 to bias the armtoward clockwise movement. It will be apparent that resilient means may be individually provided for both the arm 35 and cam 3411f so desired.

A lever 38 is preferably provided for manual setting after lockout as will be described below.

The finger may be inte ral with the lever 38, as shown, or with the arm 35 aslong as counterclockwise movement of the manual operating lever 38 will cause the lever arm 35 to move in the same direction after the finger 4-2 is contacted. It will be obvious that a certain degree of lost-motion is desirable to permit the various parts 34, 35, and 38 to operate without restriction. This may he provided :by slidably positioning the lever 38 on the free end of the rod 40, as shown.

It is to be noted that in the drawing no attempt has been made to indicate the insulation for the various portions of the mechanism, suitable insulation of course being provided in all cases in accordance with the usual practice. Further, it is to be noted that no guide means has been shown as any suitable type of guide means could be employed for the several movable members.

The operation of the device is as follows:

Assuming that the parts are in normal operating position as shown in the drawing, it will be apparent that when a load condition in excess of a predetermined value occurs, the main solenoid coil 8 will be energized and actuate the magnetic armature 9, causing the normally closed main contacts I and 2 to be disengaged and the power circuit to the load broken. At the same instant, the extension or rod ID will cause the rocker arm ii to rotate in a counter-clockwise direction,

which rotational motion will be transmitted to the pin 20.

Reclosure of the main contacts 1 and 2 is retarded by the time delay means I! in order that the probing or testing operation may be fully performed prior to re-engagement of the line contacts. An additional time delay means I8 is provided for the auxiliary contacts 5 and I6, preventing the auxiliary contacts from closing until contacts I and 2 have been fully separated for a period of time. Such time delay will permit all contact arcing to clear and further insure closure of the auxiliary circuit contacts after interruption of :the main circuit. Since the armature 9 operates the rocker arm ll immediately on the occurrence of an overload, this energy must be stored, enduring until the contacts [5 and i6 have been closed. This is accomplished by means of a spring l9 which is compressed by the counterclockwise movement of the rocker arm H as transmitted to the pin 20.

On engagement of the contacts I5 and t6, the auxiliary circuit 3| is connected with the load through line 6. As shown, the auxiliary circuit comprises a solenoid winding 30 and a resistance or impedance 32. It will be apparent that this impedance may be an integral part of the solenoid winding (not shown). It will also be apparent that other lockout operating devices such as bimetallic elementsmay be substituted for the auxiliary solenoid winding 30. In an A. C. breaker, this may be in the form of a transformer (not shown) containing a natural impedance in its windings and operating a motor or some other device responsive to current flow in the secondary circuit of such transformer.

Line faults causing an increased current in the lines 3 and 4 will accordingly reduce the impedance across the load lines 6 and I. If the combined impedance of the fault and the auxiliary resistance 32 is of a value permitting an increased current to flow in circuit 3| greater than a predetermined Value, the armature 33 will he pulled downwardly causing the L-shaped cam 34 to rotate clockwise, thus permitting the'spring auxiliary contacts 15 and I6 and holding the main contacts I and 2 in open position.

If the combined impedance value of the fault and the auxiliary resistance 32 is of a value in excess of that required to permit a current flow of sufficient magnitude to pull the armature 33 downward, thus indicating that the fault has disappeared, the main contacts I and 2 will be closed after a time delay obtained through the means 11 and the circuit will be reenergized, restoring the switch to the position shown in the drawing.

Necessarily, the combined impedance of the winding 30 and the impedance 32 must be of such value that when added to the maximum load impedance value for minimum trip current of the main circuit interrupter coil 8, minimum trip current will flow through the lockout coil 33.

In order to restore the device to operating condition after lockout, it may be reset with the aid of the manual operating lever 38. The lever 38 is rotated in a counter -clockwise direction about the pin 33 until the finger 42 contacts the lever arm 35 causing the lever arm to rotate in a counter-clockwise manner against the tensional p l f th spring 36, This spring will cause the L-shaped cam 34 to return to normal position resting against the stop 31 with the lever arm 35 resting thereon. This will then permit the main movable contact; I to return to normally closed position with the aid of the tension spring I2 as shown in the diagram. Since the lookout lever arm 35 has caused the auxiliary contacts [5 and IE to be moved upwardly, they will remain disengaged in normal fashion after resetting operations are completed.

The expression impedance is intended to be broadly construed to cover any form of electrical resistance, whether in the form of the pure resistance of Direct Current circuits or as impedance comprising resistance, inductance and capacitance components of Alternating Current circuits.

From the foregoing description, it will be apparent that a novel reclosing circuit breaker has been provided that acts as a true circuit probing device and which will determine the overload condition of the load circuit by means of an auxiliary current limiting circuit during the initial opening of the main line contacts and either permit the main contacts to reclose or retain them in open position depending upon the magnitude of the load impedance.

I claim:

1. In an electrical circuit breaker, main switch means biased toward closed position and arranged to connect a supply circuit with a load circuit, condition responsive means in series connection with said main switch means for opening said switch means responsive to current of a predetermined value flowing through said load circuit, an auxiliary circuit including normally open auxiliary switch means arranged for ccnnecting said auxiliary circuit with said load circuit subsequent to opening of said main switch means, and an impedance controlled trip mechanism in series connection with said auxiliary circuit and a lockout mechanism actuated by said trip mechanism and arranged to lock open said auxiliary switch means and said main switch means responsive to current of a predetermined value flowing through said impedance controlled trip mechanism.

2. In an electrical circuit breaker, main switch means biased toward closed position and arranged to connect a supply circuit with a load circuit, condition responsive means including a first magnetic coil in series connection with said main switch means and an armature for opening said main switch means responsive to current of a predetermined value flowing through said coil, time delay means for delaying the closing of said main switch means; an auxiliary circuit comprising a current limiting impedance, normally open auxiliary switch means arranged for connecting said auxiliary circuit with said load circuit subsequent to the opening of said main switch means, auxiliary condition responsive means including a second magnetic coil in series connectionwith said auxiliary circuit, an armature and a lockout mechanism arranged to lock open said auxiliary switch means and said main switch means responsive to current flow through said second magnetic coil above a predetermined value.

3. In an electrical circuit breaker, main switch means biased toward closed position and arranged to connect a supply circuit with a load circuit, condition responsive means including a magnet coil in series connection with said main switch means and an armature for opening said main switch means responsive to current of a pedeter'mined value flowing through said coil, main switch time delay means for delaying the closing of said switch means, an auxiliary circuit comprising a current limiting impedance, normally-open auxiliary switch means, an auxiliary time delay means operatively associated with said auxiliary switch means and arranged to delay electrical connection of said auxiliary circuit with said load circuit subsequent to the opening of said main switch means, and an auxiliary condition responsive mechanism including a lockout mechanism arranged to lock open said auxiliary switch means and said main switch means responsive to current flow through said auxiliary circuit above a predetermined value.

4. In an electrical circuit breaker including a main switch means biased toward closed position, overload responsive means including a coil in series connection with said main switch means and an armature for opening the switch means when the current controlled by the circuit breaker exceeds a predetermined value, time delay means operatively associated with said switch means to delay closure of said switch means; an auxiliary circuit comprising a current limiting impedance, auxiliary switch means operatively associated with said main switch means, delayed action means for closing said auxiliary switch means subsequent to opening of said main switch means and prior to reclosure of the main switch means, and current responsive means; a lockout mechanism, said current responsive means cooperating with said lockout mechanism to lock open said auxiliary switch means and said main switch means responsive to current flow of a predetermined value in said auxiliary circuit; and manual operating means operatively associated with said lockout mechanism to permit resetting of said main switch means to normally closed position, said manually operating means arranged for moving said lock-out mechanism to lock out position independent of load conditions.

5. In an electrical circuit breaker including a main switch means biased toward closed position for connecting a power circuit with a load circuit, condition responsive means including an operating coil in series connection with said main switch means, said condition responsive means arranged to open the switch means responsive to a predetermined value of the current controlled by the circuit breaker, time delay means retarding reclosure of said main switch means; an auxiliary circuit comprising a current limiting impedance, auxiliary condition responsive means, and normally open auxiliary switch means arranged for connecting said auxiliary circuit with said load circuit, said auxiliary switch means mechanically operatively associated with said main switch means and arranged to be closed at a period of time following the opening of said main switch means, said auxiliary switch means being further arranged to be normally opened on closure of said main switch means; a lookout mechanism operatively associated with said auxiliary condition responsive means and arranged to lock open said auxiliary switch means and said main switch means responsive to current of a predetermined value flowing through said auxiliary circuit.

6. In an electrical circuit breaker, main switch means biased toward closure and arranged to con nect a supply circuit with a load circuit, current responsive means in series connection with said main switch means for opening said switch means responsive to current of a predetermined value flowing through said load circuit, an auxiliary circuit including normally open auxiliary switch 2,820,882 7 8 means arranged for connecting said auxiliary cir- REFERENCES CITED cult with-said load circuit subsequent to opening Th f u f of d operation of said main switch, and an impedance file i s gi fi erences ale moor m the controlled. trip mechanism in series connection with said auxiliary circuit arranged to lock open 5 UNITED STATES PATENTS saidmain switch means and said auxiliary switch Number Name Date means responsive to current flown! a predeter- 1,693,328 Anderson Nov. 27, 1928 mined value through said controlled 1,796,817 Walty Mal-.17, 1931 trip mechanism; 2,528,194 V-an Ryan Oct. 31, 1950 A Van Ryan et a1 24,

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