US1676313A - Automatic reclosing circuit-breaker system - Google Patents

Description

July 10, 1928. I 1,676,313

A. E. ANDERSON AUTOMATIC RECLOSING CIRCUIT BREAKER SYSTEM Filed June 27, 1922 Inventor: Arvid EAnderso'n Hls Attorney.

Patented'July 10, 1928.

UNITED STATES PATENT OFFICE.

aavrn a. nmnason, or scnnr'mc'rany, NEW YORK, assrenoa T GENERAL ELECTRIC Y COMPANY, A coaroaarron or NEW YORK.

AUTOMATIC RECLOSING CIRCUIT-BREAKER SYSTEM.-

Application filed June 27, 1922. Serial No. 571,183.

' I My. invention relates to automatic reclosing circuit breaker systems and particularly ,to such systems in which a circuit breaker is arranged to be closed automatically to connect a source of current to a load circuit in response to the load conditions.

One object of m'y invention is to provide an improved automatic reclosing circuit breaker system of the type referred towhereby changes in the voltage of the source of current to be connected to the load circuit does'not affect the amount-of load resistance required to reclose the circuit breaker. v

Another object of my invention is to provide in an automatic rec-losing circuit breaker system of the type referred to an arrangement whereby the amount of load resistance required to reclose the circuit breaker is automaticall varied in accordance with the number 0 sources of current to be connected to the load circuit by the closing of the circuit breaker.

Another object of my invention is to provide,in an automatic reclosing circuit breaker system in which the number of sources to be connected to the load circuit by the closing of the circuit breaker may be varied an arrangement whereby the opening of the circuit breaker is controlled by the current supplied by each source.

A-further object of my invention is to I provide in an automatic reclosing circuit breaker of' the type referred to an arrange ment' whereb theclosing of the circiut breaker is e ected in response to a predetermined relationship between the voltage acrossythe suppl supplied to the oad circuit when the circuit breaker is open.

My invention will be better understood from t-he'following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims. I

Referring to the accompanying drawing which shows one embodiment of my invention, 1 represents a supply circuit which is arranged to be connected to a. load circuit 2' by means'of a circuit breaker 3 which may be of any suitable ty e. A plurality of sources of current 5 an 6 are arranged to be connected to the supply circuit 1 by any suitable means such as .the circuit breakers 7 and 8, respectively. As shown in the circuit and the current drawing, these circuit breakers 7 and 8 are provided with closing coils 9 and 10 respectrvely which, when energized, maintain the circuit breakers in their closed positions. The circuit of each closing coil may be controlled in any suitable manner asby means of a hand switch 1]. whereby the respective circuit breaker may be opened and closed.

12 and 13 represent overload relays which are associated with the sources 5 and 6, respectively, and are arranged to open the contacts 12 and 13- respectively, whenever the current supplied by the associated source exceeds a predetermined value.

In order to limit the current supplied to the load circuit 2 when the circuit breaker 3 is open, I provide a current limiting device such as a resistor 14 which is arranged to be connected across the terminals of the circuit breaker 3 by means of a, contactor 15. The closing coil 15 of the contactor 15 is connected across the supply circuitl so that whenever the supply circuit 1 is energized the resistor 14 is connected across the terminals of the circuit breaker 3 and therefore is connected in series with the supply and load circuits when the circuit breaker is open.

The circuit breakers 7 and 8- are provided with the auxiliary contacts 16 and 17 re- 86 spectively, which are arranged tobe closed when the respective circuit v breakers are closed; These contacts control the circuit of the coil 18 of a contactor 19 which is arranged to be closed when both of the circuit breakers 7 and 8 are closed. The contactor 19 is arranged to connect another current limiting device, such as a resistor 20 across the terminals of the circuit breaker 3 so that the resultant resistance connected across, the terminals of the circuit breaker 3 is reduced when both of the sources!) and 6 are connected to the supply circuit.

It is evident therefore that the amount of resistance connected in series with the supply circuit and the load circuit when the circuit breaker 3 opens varies'with the number of sources of current connected to the supply circuit. V

The resistors 14 and 20 are selected for intermittent service, and, in order to prevent their overheating when the circuit breaker 3 is open and a very low resistance short circuit is connected to the load circuit, I provide the thermostats 22 and 23 which are placed on or near the resistors so that they are afl'ected by the temperature thereof. The contacts of these thermostats are connected in the circuit of the coil of the contactor 15 so that this contactor opens and disconnects the resistor 14.- from across the terminals of the circuit breaker 3 when the temperature of either one of the resistors exceeds a predetermined value. Since the contacts 24- of the contactor 15 are connected in the circuit of the closing coil 18 of contactor 19 the opening of the contactor 15 also effects the opening of the contactor 19 so that the resistor 20 is also disconnected from across the terminal of the circuit breaker 3. Consequently, the current limiting resistors 14 and 20 are disconnected from in series with the supply circuit and the load circuit until the resistors have cooled and the thermostats 22 and 23 have closed their contact; The circuit breaker 3 is provided with a closing coil 25 which, when energized, maintains the circuit breaker in itsclosed position. When the circuit breaker is closed the coil 25 is connected across thesupply circuit 1 by means of the contacts 13" and 12 of the overload relays 13 and 12, respectively, contacts 27 of an overload relay 27 in the load circuit, the auxiliary contacts 26 of the circuit breaker 3 and contacts 24 of the contactor 15. 4 The overload relay 2'? is arranged. to open its contacts 27 only when the load current exceeds a predetermined value. When the circuit breaker 3 is opened the circuit of the closing 'coil 25 is arranged to be completed by means of the time relay 28 and the reclosing relay 29. The coil of the time relay 28 is arranged to be connected across the supply circuit 1 by means of the auxiliary contacts 30 of the circuit breaker 3 and the contacts 24 of the contactor 15 when the circuit breaker is open. The time relay is arranged in any well known manner so that it does not close its contacts 37 until a predetermined time after its coil is energized.

The reclosing relay 29 is shown as a differential relay comprising two solenoids 32 and 33 -which exert opposing forces on a pivoted member 3a carrying the movable contact 35 which is arranged to engage a stationary contact 36. The solenoid 32 is connected across the terminals of the circuit breaker 3 so that the voltage impressed thereon when the circuit breaker is open is proportional to the voltage dropacross the current limiting device connected in series with'the supply circuit and the load circuit. Therefore the current through the solenoid 32 varies in accordance with the current supplied to the load circuit. The solenoid 33 is arranged to be connected across the supply circuit 1 through the contacts 13', 12 and 27' of the overload relay 13, 12 and 27 respectively, contacts 37 of the time relay 28 and contact 24 of the contactor 15 after the circuit breaker has been open a predetermined time. Therefore the current through this solenoid varies in accordance with the supply voltage. The reclosing relay 29 is normally biasedto its open position by a spring 38.

It is apparent that, when the circuit breaker 3 is open, the voltage across the current limiting device plus the voltage across the load circuit is equal to the supply voltage. Furthermore it is apparent that for a predetermined load resistance, the ratio between the voltage across any portion of the circuit, which includes the supply circuit, the load circuit and the current limiting device, and the voltage across any other portion of the circuit is always the same and independent of the supply voltage provided the load circuit is not supplied with current at some other point. Therefore, by properly designing the solenoids 32 and 33 of the reclosing relay 29 so that the relay closes its contacts 35 and 36 only when the ratio of the currents through the solenoids is greater than a predetermined value, it is apparent that variations in the supply voltage has substantially no effect upon the amount of load registance required to cause the relay 29 to close its contacts. Such relays are wellknown in the art as ratio balance and percentage difierential relays. British Patent 28,868-1911 discloses a particular relayof this type which is especially adapted for use in connection with my invention. Therefore there is no danger of the circuit breaker being closed in response to a value of load resistance below its normal reclosing value in case the supply voltage increases above its normal value or of the circuit breaker being held in its open position until the load resistance increases above its normal reclosing value in case the supply voltage decreases below its predetermined value, as is the case when the reclosing of the circuit breaker is controlled in response to the voltage drop across only one portion of the circuit, such as across the load resistance or the current limiting resistance.

The operation of the arrangement shown in the drawing is as follows: When both of the control switches 11 are closed, the closing coils 9 and 10 of the circuit breakers 7 and 8' energized so that the circuit breakers are closed and the. sources of current 5 and 6 are connected to the supply circuit 1'.. Since the supply circuit is energized the circuit of the closing coil 15' of the contactor 15 is completed through the thermostats 22 and 23 provided the temperatures of the resistors 14 and 20 are below predetermined values, so that the resistor 14 is connected across the terminals of the circompleted so that the resistor is connected across the terminals of the circuit breaker and in parallel with the resistor 14.

When the circular breaker 3 is closed it is held in its closed position by the energization of its closing coil 25, the circuit of which is connected across the supply circuit 1 by means of the contacts 13', 12 and 27' of the overload relays 13, 12, and 27 respectively, closed auxiliary contacts 26 of the circuit breaker 3 and closed contacts 24 of the contactor 15. The circuit breaker 3 in its closed position short circuits the resistors 14 and 20 so that the voltage impressed upon the solenoid 32 of the reclosing relay is substantially zero. Inasmuch as the auxiliary contacts 30 of the circuit breaker 3 are open, the contacts 37 of the time relay 28 are open and the circuit of the solenoid 33 is open. Therefore the spring 38 maintains the reclosing relay in its open position.

As long as the load conditions on the load circuit are normal the contacts 12', 13 and 27 of the overload relays 12, 13 and 27, respectively, remain closed. When, however, anloverload or short circuit occurs on the load circuit the contacts of one or more of these overload relays .are opened so that the circuit of the closing coil 25 of the circuit breaker 3 is opened. The opening of the circuit breaker 3 removes the short circuit from around the parallel connected resistors 14 and 20 so that these resistors now limit the current supplied to the overload or short circuit to a small per cent of its normal full load value. This small current, however, produces a voltage drop across the parallel connecting current limiting resistors 14 and- 20 so that the voltage impressed upon the solenoid 32 which tends to maintain the contacts 35 and 36 separated is substantially equal to the voltage of the supply circuit in case of a very severe short circuit or over load. This small current also allows all of the overload relay or relays to return to their normal positions.

When thecircuit breaker 3 opens it also closes its auztiliary contacts 30 thereby connecting the coil of the time relay 28 across the supply circuit 1 through contact 24 of the contactor 15. After a predetermined time the relay 28 closes its contacts 37 there: by completing the heretofore described circuit for the solenoid 33 across the supply circuit 1. This solenoid 33 opposes the solenoid 32 and tends to closet-he contacts 35 and 36. The solenoid32, however, is designed so that as long as the voltage impressed thereon is greater than a certain per cent of the voltage impressed upon the solenoid 33 the relay maintains its contacts 35 and 36 open.

When the load resistance increases to a predetermined value so that the current supplied to the load circuit decreases below a predetermined value the voltage impressed upon the solenoid 32 decreases to such a value that the force exerted by the solenoid 33 overcomes the force exerted by the solenoid 32 and the spring 38 and the contacts 35 and 36 are closed. When the contacts 35 and 36 are closed, the circuit for the closing coil 25 of the circuit breaker 3 through the contacts 13, 12 and 27 of the overload relays 13, 12 and 27 respectively, contacts 37 of the time relay 28, contacts 35 and 36, coil 25 and contacts 24 of the contactor 15 is completed. The circuit breaker in closing completes the heretofore holding circuit for its coil 25 short circuits the resistors 14 and '20 and the solenoid 32, and opens the circuit of the time relay 28 so that the circuit of the solenoid 33 is open. Consequently, the spring 38 moves the reclosing relayto its open posit-ion.

If either current limiting resistor heats up to a predetermined temperature the thermostat associated therewith opensits contacts, thereby opening the circuit of the coil 15' of the contactor 15. The openingof the contactor 15 disconnects the current limiting resistor 14 from across the'terminals of the circuit breaker 3 and also opens the circuits of the coil 18 of the contactor 19 of the coil of the time relay 28 and of the solenoid 33 so that the rcclosing equipment is rendered inoperative until the resistor or resistors have cooled and the contacts of both of the thermostats are closed. When the contacts of the thermostats are closed, the circuit of the coil 15 is completed and the closing of this contactor completes the circuits of the coil 18 of the contactor 19, of the coil of the time relay 28 and of the solenoid 33 so that the reclosing operation takes place in the manner above described,

The operation of the reclosing equipment is the same as above described when only one of the sources of current shown in the drawing is connected to the supply circuit except that the amount of load resistance required to reclose the circuit breaker is'greater.

Since the normal full load resistance varies with the number of generators connected to the supply circuit it is necessary to change the setting of the reclosing equipment so that it recloses in response to a greater load resistance when only one generator is connected to the supply circuit than when two or more generators are connected to the supply circuit. In order to accomplish this result I vary the resistance connected across the terminals of the circuit breaker in accordance with the number of generators connected to the supply circuit so that the amount of load resistance required to produce a certain current through and therefore a certain voltage drop across the resistance connected across the terminals of the circuit breaker varies with the number of generators connected to the supply circuit,

In the arrangement shown in the drawing, the resistorv 1 is arranged to be connected across the contacts ot the circuit breaker whenever either one of the sources 5 and 6 is connected to'the supply circuit 1, When, however, both or the generators are connected to the supply circuit, the coil 18 ct contactor 19 is energized so that the resistor 20 is connectedin parallel with the resistor 14 and the resultant resistance is decreased. Therefore, the amount of load resistance required to produce the necessary voltage drop to operate the reclosing relay 29 is much greater when only one of the sources shown is connected to the supply circuit than when both sources are connected to the supply circuit.

While I have shown and described one embodiment of my invention, I do not desire to be limited thereto but seek to cover in the appended claims all those modifications which fall within the true spirit {and scope of my invention.

VVhat I claim as new and de 'irc to secure by Letters Patent of the United States, is

1. In an automatic reclosing circuit breakersystem, a supply circuit, a load circuit, a circuit breaker for connecting said. circuits together, closing means for said circuit breaker, means for connectin said circuits together when said circuit breaker is open, and a ratio balance relay operative in response to a predetermined ratio between the voltage of said supply circuit and the current supplied to said load circuit from said supply circuit when said circuit breaker is open to effect the operation of said closing means.

2. In an automatic reclosrngmrcmt breakor system, a variable voltage supplyrcircuit, a

load circuit, a circuit breaker for connecting said circuits together, closing means for said circuit breaker, a current limiting device arranged to be connected inseries with said circuits when said circuit breaker is open, and means operative in response to a predetermined ratio. between the variable supply voltage and the voltage drop across said current limiting device to efi ect the operation of said closing means. 7

3. In an automatic reclosing circuit breaker system, a supply circuit, a load circuit, a circuit breaker for conuecting'said circuits together, closing means for said circuit breaker, means for connecting said circuits together when said circuit breaker is open, and a percentage differential relay for controlling said closing means, said differential relay having two solenoids arranged in opposition to each other, one of said solenoids being arranged to be energized in accordance said solenoids being arranged to, be energized in accordance with the current supcircuits together, closing means for said circuit breaker, means for connectin said circuits together when said circuit breaker is open, and a percentage differential relay having two solenoids arranged in opposition to each other and adapted to effect the operation of said closing, means when the ratio between the currents through the solenoids exceeds a predetermined value, one of said solenoids-being arranged to be energized in accordance with the supply voltage and the other of said solenoids being arranged to be energized in accordance with the current supplied to said load circuit from said supply circuit when the circuit breaker is open.

5, In an automatic reclosing circuit breaker system, a supply circuit, a load circuit, a circuit breaker for connectin said circuits together, closing means for c osing said circuit breaker, a current limiting device arranged to be connected in series with said circuits when said circuit breaker is open, and a percentage differential relay for controlling said closing means, said differential relay having two solenoids arranged to oppose each other, one of said solenoids being arranged to be energized in accordance with the supply circuit voltage and the other of said solenoids being arranged to be energized in accordance with the'current through said current limiting device.

6. 'In an automatic reclosing circuit breaker system, a supply circuit, a load circuit, a circuit breaker for connecting said circuits together, closing means for said circuit breaker, a resistor arranged to be connected in series with said circuits when said circuit breaker is open, a difierential relay for controlling said closing means, said differential relay having two solenoids arranged to oppose each other, one of said solenoids being arranged to be connected,

across said supply circuit independently of said resistor and the other of said solenoids being connected in parallel with said resistor, and means operative after said circuit breaker has been open a predetermined length of time to effect the connection of said first mentioned solenoid to said supply circuit.

' 7. In. an automatic reclosing circuit breaker system, a supply circuit, a load cir cuit, a circuit breaker for connecting said ircuits together, a closing coil for said circuit breaker, a circuit for said closing coil,

with the supply voltage and the other of a differential relay arranged to control the current limiting means.

circuit oi said closing coil comprising two solenoids arranged in opposition, means for connecting one of said solenoids in parallel with said resistor, a time relay adapted to connect the other solenoid across said supply circuit, and a circuit for said time relay arranged to be completed when said circuit breaker opens.

8. In an automatic reclosing circuit breaker system, a load circuit, a supply circuit, a plurality of sources of current, means arranged to be operated to connect said sources to said supply circuit, a circuit breaker arranged to connect said supply circuit to said load circuit, means operative in response to the load resistance of said load circuit to effect the reclosing of said circuit breaker, and means automatically controlled by the operation of said connecting means for said sources to change the setting of said reclosing means so that the amount of load resistance required to reclose said circuit breaker varies in accordance with the number of sources connected to said supply circuit.

9. In an automatic reclosing circuit breaker system, a load circuit, a supply circuit, a plurality of sources of current, means for connecting said sources to said supply circuit, a. circuit breaker adapted to connect said supply circuit to said load circuit, means operative in response to the resistance of said load circuit to effect the closing of said circuit breaker, means for changing the setting of said reclosing means so that the amount of load resistance required to reclose said circuit breaker varies in accordance with the number of sources connected to said supply circuit comprising current limiting means arranged to be connected in series with said supply circuit and said load circuit when said circuit breakeris open, and means operative in response to the connection of a source of current to said supply circuit to vary the resistance of said 10. In an automatic reclosing circuit breaker system, a load circuit, asupply 011- cuit, a plurality of sources of current, a plurality of circuit breakers each being arranged to connect one of said sources of current to said supply circuit, a circuit breaker arranged to connect said supply c rcuit to said load circuit, means operative n. response to a predetermined electrical condition of any one of said sources to effect the opening of said circuit breaker between and load and supply circuits, and means operative in response to the load resistance of said load circuit to effect the reclosing of said circuit breaker.

ranged to connect one of said sources of current to said supply circuit, a circuit breaker arranged to connect said supply circuit to said load circuit, means operative in re sponse toa predetermined electrical condition of any one of said sources to efiect the opening of said circuit breaker between said load and supply circuits, a plurality of resistors, means operative in response to the closing of said plurality of breakers'to ellectthe connection of said resistors in parallelacross the terminals of the circuit breaker between said supply and load circuits, and

rality of circuit breakers each being ar- I ranged to connect one of said sources of current to said supply circuit, means adapted to be operated to efi'ect the opening and closing of said circuit breakers, a circuit breaker arranged to connect said supply circuit to said load circuit, means operative in response to the load resistance of said load circuit to effect the closing of said last mentioned circuit breaker, a current limiting device, means operative in response to the voltage of said supply circuit to effect the connection of said current limiting device in series with said supply circuit and said load circuit when said last mentioned circuit breaker is open, a second current limiting device, and means operative in response to the closing of a certain number of said plurality of circuit breakers to efi'ect the connection of said second current limiting device in parallel with said first mentioned current limiting device.

13. In an automatic reclosing circuit breaker system, a load circuit, a supply circuit, a plurality of sources of current, a plurality of circuit breakers each being arranged to connect one of said sources of current to said supply circuit, means adapted to be operated to efiect the opening and closing of said circuit breakers, a circuit breaker arranged to connect said supply circuit to said load circuit, means operative in response to the load resistance of said load circuit to effect the closing of said last mentionedcircuitbreaker, aresistor, means operative in response to the voltage of said supply circuit to effect the connection of said resistor in series with said supply circuit and said load circuit when said last ,mentioned circuit breaker is open, a second resistor, and means operative to efiect the connection of said second resistor in parallel with said first mentioned resistor when said first resistor connecting means is operated and two of said plurality of, circuit breakers are closed.

14. In an automatic reclosing circuit breaker system, a load circuit, a supply circuit, a plurality of sources of current, a plurality of circuit breakers each being arranged to connect one of said sources of current to said supply circuit, means adapted to be operated to effect the opening and closing of said circuit breakers, a circuit breaker arranged to connect said supply circuit to said load circuit, means operative in responseto the load resistance of said load circuit to effect the reclosing of said last mentioned circuit breaker, a resistor, means operative in response to the voltage of said supply circuit to effect the connection of said resistor in series with said supply circuit and .said

load circuit when said last mentioned circuit breaker is open, a second resistor, means operative to effect the connection of said second resistor in parallel with said first mentioned resistor when said first resistor connecting means is operated and two of said plurality of circuit breakers are closed, and temperature responsive means operative in response to the temperature of said resistors to effect the disconnections of said resistors from their series relationship with said load circuit and said supply circuit.

15. In an automatic reclosing circuit breaker system, a load circuit, a supply circuit, a plurality of sources of current, a plurality of circuit breakers each being arranged to connect one of said sources of current to said supply circuit, means adapted to be operated to eflect the opening and closing of said circuit breakers, a circuit breaker arranged to connect said supply circuit to said load circuit, means adapted to be operated to effect the opening of said 'last mentioned circuit breaker, means operative in response to the load resistance of said load circuit to effect the reclosing oi said last mentioned circuit breaker, a resistor, electromagnetically operated means adapted to effect the connection of said resistor in series with said supply circuit and said load circuit when said last mentionedcircuit breaker is open, a circuit for said electromagnetically operated means connected across said supply circuit, temperature responsive means'operative in response to the temperature of said resistor to effect the opening of the circuit of said electromagnetically operated means. a second resistor a second electromagnetically operated means adapted to effect the connection of said resistor in parallel with said first mentioned resistor, and a circuit for said sec ond electromagnetically operated means adapted to be completed when two of said plurality of circuit'breakers and said first mentioned electromagnetic-ally operated means are closed.

16. In an automatic reclosing circuit emma breaker system, a supply circuit, a load circuit, a clrcuit breaker for connectlng said circuits together, overload: responsive means for eflecting the opening of said circuit breaker comprising a coilconnected so that it is energized in accordance with the supply voltage and an opposing coil connected so that it is energized in accordance with variations in the load connected to the load circuit when the circuit breaker is open.

17. In an automatic reclosing circuit breaker system, a supply circuit, a load circuit, a circuit breaker for connecting said circuits together, overload responsive means for effecting the opening of said circuit breaker, means for limiting the amount of current supplied from said supply circuit to said load circuit when said circuit is open, closing means for said circuit breaker, and means for effecting the operation of said closing means to close said circuit breaker compris ing a ratio balance relay having an actuating winding and a restraining winding connected so as to be energized in accordance with the load connected to the load circuit when the circuit breaker is open.

18. In an automatic reclosing circuit breaker system, a supply circuit, a load circuit, a circuit breaker for connecting said circuits together, overload responsive means for effecting the opening of said circuit breaker", means for limiting the amount of current supplied from said supply circuit to said load circuit when said circuit is open, closing means for said circuit breaker, means for effecting the operation of said (losing means to close said circuit breaker comprising a balance relay having a winding so connected that its energization varies in accordance with the load connected to the load circuit when the circuit breaker is open and an opposing winding adapted to be connected across the supply circuit independently of said current limiting means, and means operative after said circuit breaker has been open a predetermined length of time to effect the connection of said opposing winding across the supply circuit.

19. In an automatic reclosing circuit breaker system, a supply circuit, a load circuit, a circuit breaker for connecting said circuits together, overload responsive means for efl'ecting the opening of said circuit breaker, means for limiting the amount of current supplied from said supply circuit to said load circuit when said circuit is open, closing means for said circuit breaker, and means for efl'ecting the operation of said closing means to close said circuit breaker comprising a ratio balance relay having an when the circuit breaker is open.

'20. in an automatic reclosing circuit breaker system, a supply circuit, a load circuit, a circuit breaker for connecting saidcircuits together, overload responsive means for effecting the opening of said circuit breaker, current limiting means for limiting the amountof current supplied from said supply circuit to the load circuit when the circuit breaker is open. closing means for said circuit breaker, and aratio" balance relay for controlling the operation of said closing means comprising an actuating winding, and a restraining winding connected in parallel with said current limiting means.

21. In an automatic reclosing circuit breaker system, a supply circuit, a load circuit, a circuit breaker for connecting said circuits together, current limiting means arranged to limit the current flowing between said circuits when said circuit breaker is open, a differential relay for controlling the reclosing of said circuit breaker comprising a movable member and two independent electromagnets cooperating with said member to exert opposing forces thereon, one of said electromagnets being connected in a circuit across said supply circuit which is in parallel with said current limiting means and said load circuit, the other electromagnet' being connected in a circuit so that it is energized in accordance with the load connected to said load circuit when said circuit breaker is open, and means operative after said cir cuit breaker. has been open a predetermined length of time for effecting the completion of the circuit of one of said electromagnets.

22. In an automatic reclosing circuit breaker system, a supply circuit, a loadcircuit, a circuit breaker for connecting said circuits together, current limiting means arranged to limit the current flowing between said circuits when said circuit breaker is open, a difierential relay for controlling the reclosing of sald circuit breaker comprising a movable member and two independent electromagnets cooperating with said member to exert opposing forces thereon, one of said electromagnets being connected across said supply circuit independently of said current limiting means, the other electromagnet being connected in a circuitso that it is energized in accordance with the load connected .to said load circuit when said circuitbreaker is open, and time delay means arranged to effect the completion of the circuit of one of said electromagnets after said circuit breaker has been open a predetermined length of time.

In'witness whereof, I have hereunto set my hand this 24th day of June, 1922.

ARVID E. ANDERSON.

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