US1901628A - Undervoltage device - Google Patents

Undervoltage device Download PDF

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US1901628A
US1901628A US380859A US38085929A US1901628A US 1901628 A US1901628 A US 1901628A US 380859 A US380859 A US 380859A US 38085929 A US38085929 A US 38085929A US 1901628 A US1901628 A US 1901628A
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circuit
device
energy
electrical
current
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Maurice W Brainard
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CBS Corp
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Westinghouse Electric and Manufacturing Co
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    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02HEMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/24Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to undervoltage or no-voltage
    • H02H3/247Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to undervoltage or no-voltage having timing means

Description

March 1933- M. w. BRAINARD 1,901,628

UNDERVOLTAGE DEVICE Filed July 25. 1929 ATTORNEY Patented Mar. 14, 1933 UNITED STATES PATENT OFFI CE MAURICE W. BRAINABD, OF WILKINSBURG,

noose Emcmc 0; MANUFACTURING VANIA UN DERVOLTAGE DEVICE Application filed July 25,

My invention relates to circuit interrupters and particularly to time-delay tripping devices therefor.

One object of my invention is to provide an undervoltage tripping device of the above designated type with means that shall delay the release'of the device after the voltage of the circuit has been reduced to a predetermined tripping value.

An undervoltage device, as usually employed to trip a circuit interrupter, is provided with a biased tripping mechanism that is controlled by an armature held in engagement by an electromagnet which is energized by current in a circuit associated with the main circuit to be controlled by the circuit interrupter. When the voltage, or the current, in the case of an under-load device, falls to a predetermined value, the holding force of the electromagnet becomes less than the tension in the biased mechanism associated with the armature so that the latter is released to trip the circuit interrupter.

It is often desirable to provide means commonly called time-delay devices, which insure the lapse of a time interval between the instant that the voltage, or current, reaches the aforesaid predetermined value and the instant that the actuation of the tripping mechanism occurs. Such means insures against the tripping of the circuit breaker upon the occurrence of mere momentary surges of current or voltage, it being desirable that such surges, which are relatively frequent but harmless, shall not cause the circuit breaker to open.

In practicing my invention, I make use of the peculiar properties of control-circuits, energized from alternating-current circuits through the intermediary of rectifiers, to

produce time delay of the sort above-described in the operation of alternating-current circuit interrupters.

It is another object of my invention to provide a time interval between the energization and the actuation of a tripping device of the above-described t pe by adjustable means that shall be capable of varying the said interval over a considerable range to 1829. Serial No. 380,859.

meet the requirements of different service conditions.

A further object of my invention is to provide an undervoltage tripping device for an alternating-current circuit with means energized from a source of direct-current energy to retain the device in its active position but to be responsive to th variations in the alternating current to obtain an interval between the time when the voltage or the current reaches a predetermined reduced value and the time when the device is released.

lVith these principles and objects in mind, my invention will best be understood by referring to the following specification and to the drawing wherein;

Figure 1 is a schematic diagram of an undervoltage tripping device that is connected in circuit with other apparatus .in such manner as to embody my invention;

Fig. 2 is a view, similar to Fig. 1, with the exception that a separate source of directcurrent energy is employed.

My invention comprises, in general, a circult interrupter 1 that controls the flowof energy through a main circuit 2, 3. The c rcuit interrupter 1 is held in closed position by a magnetic core 4 that is here shown retained in attracted position by an energized Winding 5 against the bias of a spring 6.

A control circuit 7 8 is connected directly to the main circuit 2, 3 when the voltage of the main circuit is of low value. When the voltage of the main circuit 2, 3 is of a high value, the control circuit 7, 8 is energized through a transformer 9. A rectifier 11 that, preferably, is of a simple commercial type, such as a dry plate contact rectifier of the copper-oxide type, is connected to the circuit 7, 8 as a full-wave rectifier. A relay 12, comprising contacts 13, 14 and 15, is connected in parallel with the rectifier 11 to the control circuit 7, 8. The operating coil of the relay 12 may be connected to the direct-current side of the rectifier 11 if the relay is of the direct-current type.

The rectifier 11 ensures a unidirectional flow of energy through a circuit 16, 17 that is connected to the coil device 4, a reactor 18 being provided in the conductor 16 which is completed by the contacts 13 when the armature of the relay 12 is in the position to which it is actuated by its energized coil.

' closed to their open positions.

e resistor 19 is shunted across the circuit 16, 17, through the contacts 14 of the relay 12 and ahead of the reactor 18, the contacts 14 being separated when the armature of the rela is actuated by its coil.

A resistor 21 is p aced in series with the contacts 15 that are closed, when the relay armature is actuated by its coil, to shunt the resistor across the circuit 16, 17 behind the reactance 18. The resistor 21 is employed to increase the effective energy in the reactor 18 "when normal energy is flowing therethrough and through the winding 5.

A resistor 22 is provided in series with a unidirectional valve 23, that may be a small cop er-oxide rectifier, across the circuit 16, 17 ahead of the reactor 18 to permit current fiow through the reactor 18 and the coil 5 during the time the contacts 13 and 14 are respectively moving from their A variab rectional device 23 prevents a flow of energy in the reverse direction when a normal current is flowing in the circuit 16, 17.

A condenser 24 is placed across the circuit 16, 17 in parallel relation with the conductor containing the resistor 21 and the contacts 15, the utility of which will be pointed out hereinafter.

An impedance or resistor 25 is provided in series with the rectifier 11 to reduce the efiective energy of the circuit 16, 17 to an amount sufiicient to energize the winding 5. The winding 5 may also be connected directly to the alternating-current circuit 7, 8 through the medium of a conductor 26, a resistor 27, conductor 17 and switches 28 and 29. Such auxiliary circuit may be temporarily employed to energize the winding 5 when the rectifier 11 or other apparatus in the circuit 16, 17 become damaged or inoperative. The winding 5 will then be energized directly from the alternating-current source and will release the core 4 when a predetermined condition is present in the circuit 2, 3 without the aforementioned dela A push-button switch 31 may be utilized to ensure remote tripping of the circuit 1nterrupter the instant it is actuated, through the employment of a circuit that will now be described. A resistor 32 is connected in series with the winding 5 and is shunted by contacts 33 of the push-button switch 31, when the latter is in its retracted position.

" A second set of contacts 34 of the pushbutton switch 31 are open when the contacts 33 are closed. The contacts 34 shunt the resistor 32 and the winding 5 from the circuit 16, 17 when the push button is moved 5 of the tripping The unidito open the contacts 33 and to close the contacts 34.

The tripping device 31 was found to be not done by an operator, the present arrangement of short-circuiting .the winding 5 through the resistor 32 ensures instantaneous release of the core'4 and the circuit interrupter, irrespective of the length of time thepush button is retained in circuit-closed position.

A relay 35, having contacts 36, ensures release of the circuit interrupter when abnormal conditions, other than the aforesaid reduction of energy, are present in the main circuit 2, 3. The contacts 36 are connected in parallel with the winding 5 to short circuit the latter from the energy, provided to retain the core 4 in attracted position. Energy to actuate the contacts 36 of the relay 35 is available when an abnormal condition is present in the main circuit 2, 3 and is herein shown connected to a transformer 37 to obtain protection against excessive current conditions.

Fig. -2-disc1oses a system similar to that of Fig. 1, with the exception that the means for converting the alternating current into a direct current is omitted, and a separate source of direct current supply, such as a battery 38, is provided. Operation similar to that of the system shown in Fig. 1 will be obtained, and the other ap aratus therein shown, but not included in ig. 2 may be employed in this system.

The operation of the device will now be described. When the circuit interrupter is moved to closed position, the main circuit 2, 3 is completed, energizing the transformer 9 that, in turn, energizes the control circuit 7, 8. The energy of the latter circuit actuates the relay 12 to closed position, closing contacts 13 and 15 and opening contacts 14. The rectifier 11 is energized, through the resistor 25, from the circuit 7, 8 to rovide a direct-current energy to the circuit 16, 17. The latter circuitis completed by the closure of the contacts 13 through the reactance 18 to energize the winding 5. Through the energization of the winding 5, the core 4 is retained in attracted osition to hold the circuit interrupter in c osed-circuit position against the bias of the spring 6.

In the diagram employed for illustration, the core 4 directly holds the toggle of the circuit interrupter in over-center or latched position. It is to be understood that the core 4 and the winding 5 may be a separate attachment that actuates a tri ger for releasing the circuit interrupter rom latched 7 position instead of thereto, as herein shown.

being directly connected The resistor 21 is inserted across the circuit 16, 17 by the contacts 15 to increase the effective energy flowing through the reactor 18. At the instant the contacts 15 are opened, the entire energy flowing through the reactor 18 is immediately available to provide a kick to the winding 5. The condenser 24 absorbs some of the energy of the aforementioned inductive kick, which is thereafter fed back to the winding 5 to further increase the time interval that elapses before the core 4 is released. The condenser has further utilit in reducing the arci at the contacts 15 when the latter are move to open position at the time energy is flowing through the reactor 18.

When the alternating-current voltage in the circuit 2, 3 drops to a (predetermined value, the relay 12 is release the contacts 13 and 15 are moved to open position, and the contacts 14 are moved to closed sition. During this interval, the ener o the reactor 18 would ordinarily be issipated because of the arcing at the contacts 13. This arcing is prevented by the addition of the conductor containing the unidirectional valve 23 and the resistance 22. ,This result may be obtained by connecting a condenser or a resistor directly across the contacts 13.

When the contacts 14 are closed, a circuit is completed through the variable resistor 13, the reactor 18 and the winding 5 to permit the energy in this closed circuit to slowly dissipate. This energy retains the core 4 1n attracted position for some time after the release of the relay 12. By the adjustment of. the variable resistor 19, the time interval may be increased or diminished. A small amount of resistance will give a longer time delay; a greater amount, a shorter delay.

If, during the time the circuit interru ter is closed, an overload or other predetermlned abnormal condition is present in the circuit 2, 3, the relay 35 will be actuated to close the contacts 36. The contacts 36, when closed, short circuit the winding 5 to obtain the release of the core 4, in a manner heretofore explained. I

In will thus be seen that I have provided an interval of time between the reduction of energy in the main circuit and the time when the circuit is interrupted to prevent the circuit from being interrupted i the said reduction of energy is only of momentary duration. I provide this time interval by allowing the energy stored in a reactor to slowly dissipate through the 'holding coil after the circuit thereto is interrupted. Instantaneous tripping means is provided for the hand tripping device to assure the release of the circuit interrupter when a push-button switch is actuated.

While I have illustrated but a single emseries with the bodiment of my invention, it is to be understood that many changes, additions, subtractions and substitutions may be made therein without departing from the spirit and scope of such invention. Therefore, I do not wish the a pended claims to be limited exceptas may e necessitated by the prior art.

I claim as my invention:

1. The combination with a circuit interrupter for an alternating-current circuit, of a device therefor energized from the said circuit and releasable to trip the circuit interru ter when the voltage of the circuit has ecreased to a predetermined value, means in the circuit of the device to convert the alternating current to a direct current, and means for retaining the direct current for an interval above the drop-out value of the tripping device after the alternating current has decreased to a predetermined lower value.

2. The combination with a circuit interrupter for an alternatin -current circuit, of means for converting the alternating current to a direct current, a device for procuring the release of the said circuit interrupter, said device being held in inoperative position by the said direct current, and means for retaining sufiicient direct current for maintaining the device inoperative for an interval after the said alternating current has decreased to a predetermined value.

3. The combination with a circuit interrupter for an alternating-current circuit, of means for converting the alternating current to a direct current, a device for procuring the release of rupter, said device being held in inoperative position by the said direct current, means for retainin the direct current above the tripping va ue of the device for an interval after the said alternating current has decreased to a predetermined value, and means for regulating the said interval.

he combination with a circuit interrupter for controlling an alternating-current circuit, of means for converting the alternating voltage to a direct voltage, an undervoltage device retained in inoperative position by the said direct voltage, a reactor in series with the undervoltage device, a re- SiStOI, a plurality of contacts and means, actuated when the alternating .volta e has decreased to a predetermined value, or actuating the said contacts to interrupt the direct voltage and to insert the resistor in said reactor and the said undervoltage device.

5. The combination with a device that is released when the retaining electrical energy is decreased below a predetermined value, of an alternating electrical supply circuit controlled thereby, means for converting the alternating electrical energy into the said circuit inter-- unidirectional electrical energy to energize the said device, a circuit for the unidirectional electric energy, a reactor in the umdirectional electrical circuit, aresistor, and means actuated when an electrical characteristic of the alternatin supply circuit has reached a predetermine value to interrupt the unidirectional electrical source of energy and to insert the said resistance in series with the said reactor and the said device, and means for releasing the device, under predetermined conditions when the said energy is above the said predetermlned value.

6. The combination with a device that released when the retainin electrical ener gy is decreased below a pre etermined value, of 'an alternating electrical supply circuit controlled thereby, means for convertm the alternating electrical energy into um irectional electrical energy to energize the said device, a reactor in the unidirectional electrical circuit, a resistor, means actuated when an electrical characteristic of the alternatin'g electrical su ply circuit has reached a predetermined va ue to interrupt the unidirectional electrical source of energy and to insert the said resistor in series with the said reactor and the said device, and means for obtaining the immediate release of the said device when actuated.

7. The combination with an undervoltage tripping device for a circuit interrupter operable on an alternatin -voltage circuit, 0 means for converting t e alternating voltage into direct voltage, an impedance associated with the said means to regulate the value of the direct voltage and a circuit aralleling said converting means and the impedance whereby either alternating or direct voltage may be employed to operate the said device.

. 8. The combination with a device that is released when the retaining electrical energy is decreased below a predetermined value, of an alternating electrical supply circuit controlled thereby, means for converting the alternating electrical energy into unidirectional electrical energy to energize the said device, a circuit for the unidirectional electrical energy, and impedance in the unidirectional electrical circuit, a second impedance, means actuated when .an electrical characteristic of the alternating electrical supply circuit hasreached a predetermined value to interrupt the unidirectional electrical source of energy and to insert the said second impedance in series with the first said impedance and the said device, and a. third impedance shunting the said interrupting means for preventing the circuit to the device from eing opened when the said in terrupting means is actuated.

9. The combination with a device that is released when the retaining electrical energy is decreased below a predetermined e unidirectional '7 has reached a predetermined va ue to interrupt the unidirectional electrical source of energy and to insert the said resistance in series with the said reactor and the said device, and a second resistor shunting the said interrupting means and associated with a unidirectional valve that prevents a current flow when in normal operation but permits such flow when the said contacts are actuated.

10. The combination with a device that is released when the retaining electrical energy is decreased below a predetermined value, of an alternating electrical supply circuit controlled thereby, means for converting the alternating electrical energy into unidirectional electrical energy to energize the said device, a circuit for the unidirectional electrical ener y, a reactor in the unidirectional electrica circuit, a resistor, means actuated when an electrical characteristic of the alternating electrical supply circuit has decreased below a predetermined value to interrupt the unidirectional electrical source of energy and to insert the said resistor in series'with the said reactor and the said device, and a second resistor controlled by the said means to shunt out part of the ener from the reactor to the device when sai electrical characteristic is normal.

11. The combination with a device that is released when the retaining electrical energy is decreased below a predetermined value, of an alternating electrical supply circuit controlled thereby, means for converting the alternating electrical energy into unidirectional electrical energyto energize the said device, a reactor in the unidirectional electrical circuit, a resistor, means actuated when an electrical characteristic of the alternating electrical supply circuit has reached a predetermined value to interrupt the unidirectional electrical source of energy and to insert the said resistor in series wit the said reactor and the said device, a second resistor controlled by the said means to shunt out part of the energy from the reactor to the device when normal energy is present in the circuit, and a condenser in parallel with the said device.

12. The combination with a device that is released when the retaining electrical energy is decreased below a predetermined value, of an alternating electrical supply circuit controlled thereby, a source of direct electrical energy for retaining the said device in inoperative position, a reactor in the direct-energy circuit, a resistor, a relay energized from said supply circuit and actuated when the voltage thereof has decreased to a predetermined value for cutting oil the direct-energy supply and for inserting the said resistor in series with the said reactor and the device to complete a circuit therewith, and a separate means associated with the device to ensure its release when a predetermined current is present in the alternating circuit.

13. The combination with a device that is released when the retaining electrical energy is decreased below a predetermined value, of an alternating electrical su ply circuit controlled thereby, a source of direct electrical energy for retaining the said device in its inactive position, a reactor in the direct-energy circuit, a resistor, a relay energized from said supply circuit and when an electrical characteristic of said supply circuit has reached a predetermined value for cutting off the direct-energy supply and for inserting the said resistor in series with the said reactor and the device to complete a circuit therewith, a second resistor in series with the device, and -a double-throw switch for remote instantaneous tri ing by normally shunting out the last sa1 1 resistor but inserting it in. series with the device when actuated to short circuit the device and the last said resistor from the energy in the circuit that provides the time delay for the release of the said device.

14. In electrical apparatus for controlling the operation of a circuit interrupter for a main circuit, an undervoltage device for causing the operation of said circuit interrupter, an alternating current control circuit responsive to the occurrence of a predetermined electrical condition in said main circuit, a direct current circuit for energizing said undervoltage device, said direct current circuit being responsive to electrlcal conditions in said alternating current circuit to actuate said undervoltage device due to the occurrence of said predetermined electrical condition in said main circuit, and said direct current circuit also having means for storing electricalenergy and releasing it through said undervoltage device and delaying its actuation for a period after the occurrence of said predetermined electrical condition in saidmain circuit.

15. In electrical apparatus for controlling the operation of a circuit interrupter for a main circuit, an alternating current control circuit responsive to said main circuit, a rectifier for supplying direct current fromsaid alternating current circuit, a direct current circuit from said rectifier having a device connected therein for causing the operation of said circuit interrupter due to the occurrence of a predetermined electrical condition in said main circuit, said direct current circuit having inductance therein and providing a closed electrical circuit for the flow of the energy stored therein through said device after the occurrence of said predetermined electrical condition in said main circuit to delay the operation of said circuit interrupter.

16. In electrical apparatus for controlling the operation of a circuit interrupter for an alternating current circuit, a rectifier connected in parallel relation to said alternatin current circuit, a tripping device for said circuit interrupter having an electromagnet which, when energized, maintains said circuit interru ter in closed position, said electro-magnet being energized throu h a direct current circuit from said recti er and havin its ener ization therefrom reduced to t e point w ere said circuit interrupter is released upon a'predetermined decrease in the volta e of sa1d alternating current circuit, said ing inductance therein and providing a closed electrical circuit for the flow of the energy stored therein through said electromagnet for supplying energy to said electromagnet to maintain said clrcuit interrupter closed for a eriod after the supply of energy from sa1d rectifier is not sufiicient to maintain said circuit interrupter closed.

17. In electrical apparatus for controlling the operation of a a main circuit, an alternating current control circuit responsive to said main circuit, a rectifier for supplying direct current from said alternating current circuit, a direct current circuit from said rectifier having a device connected therein for causing the operation of said circuit interrupter due to the occurrence of a predetermined electrical condition in said main circuit, said direct current circuit having inductance therein and roviding a closed electrical circuit for the fl dw of the energy stored therein through said device after the occurrence of said predetermined electrical condition in said main circuit to delay the operation of said circuit interrupter, and means for actuating said device to cause the operation of said circuit interrupter without said delay.

18. In an electrical apparatus for controlling the operation of a circuit interrupter for an alternating current circuit, a rectifier connected in parallel relation to said alternating current circuit, a tripping device for said circuit interrupter having an eIectro-magnet which, when energized, maintains said circuit interrupter in closed position, said electro magnet being energized through a. direct current circuit from said rectifier and having its energization therefrom reduced to the oint where said circuit interrupter is released upon a predetermined 1rect currentcircuit havcircuit interrupter for pos tion,

decrease in the voltage of said alternating current circuit, said dlrect current circuit having inductance therein and providing a closed electrical circuit for the flow of the energy stored therein through said electromagnet for supplying energy to said electromagnet to maintain said circuit interrupter closed for aperiod after the suppl of energy from said rectifier is not su cient to maintain said circuit interrupter closed, and means for causing the operation of said electro-magnet to release said circuit interrupter when a redetermined current flows in said alternating current circuit.

19. In a time delay circuit for a device actuated when the energy supplied thereto is changed to a predetermined value, a reactor in series with the device, a resistor for short circuiting a part of the energy flow through the reactor from the device, a condenser in parallel relation to the said device, a second resistor, and means responsive to a predetermined change in an electrical characteristic of the supply, said means opening the circuit of the first said resistor, inserting said second resistor in series with said reactor, and short circuiting the device through said second resistor, the reactor and the condenser in order to retain the energy of the circuit for an interval to provide a delay between said predetermined change in an electrical characteristic of the supply and the actuation of the device.

20. The combination with a device that is released when the retaining electrical energy is decreased below a predetermined value, of a main electrical supply circuit controlled thereby, a source of direct electrical energyfor retaining the said device in inoperative a reactor in the direct-ener circult, a resistor, and a relay energize from said supply circuit and actuated when an electrical characteristic thereof has decreased to a predetermined value, for cutting off the direct-energy supply and for inserting the said resistor in series with the said reactor and the device to complete a circuit therewith.

21. In electrical apparatus for controlling the operation of a circuit interrupter for a main circuit, an alternating current control circuit responsive to said main circuit, a rectifier for supplying direct current from said alternating current circuit, a direct current circuit from said rectifier having a device connected therein for causing the operation of said circuit interrupter due to the occurrence of a predetermined electrical condition in said main circuit, said direct current circuit having inductance therein through which all of the current from the rectifier flows until the occurrence of said predetermined electrical condition, and said direct current circuit providing a closed electrical circuit for the flow of the energy stored therein through said device after the occurrence of said predetermined electrical condition'in said main circuit to delay the operation of said circuit interrupter.

22. In electrical apparatus for controlling the operation of a circuit interrupter for an alternating current circuit, a rectifier connected in parallel relation to said alternating current circuit, a tripping device for said circuit interrupter having an electromagnet which, when energized, maintains said circuit interrupter in closed position, said electro-ma'gnet eing energized through a direct current circuit from said rectifier and having its ener ization therefrom reduced to thepoint w ere said circuit interrupter is released upon a predetermined decrease in the voltage of said alternating current circuit, said direct current circuit having inductance therein, s'aid inductance being in series with all branches of said direct current circuit through which current from the rectifier may flow until the occurrence of said predetermined decrease in voltage, and said direct current circuit roviding a closed electrical circuit for the ow of the energy stored therein through said electro-magnet for supplying energy to said electro-magnet to maintain said circuit interrupter closed for a period after the supply of energy from said rectifier is not suflicient to maintain said circuit interrupter closed.

In testimony whereof, I have hereunto subscribed my name this 19th day of July MAURICE W. BRAINARD.

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Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2440108A (en) * 1943-05-05 1948-04-20 Gen Electric Overcurrent protective system for a direct-current load circuit
US2447638A (en) * 1943-05-27 1948-08-24 Westinghouse Electric Corp Excitation control system for vapor electric devices
US2453486A (en) * 1945-01-01 1948-11-09 Picker X Ray Corp Waite Mfg Electronic timer
US2481431A (en) * 1943-08-10 1949-09-06 Ward Leonard Electric Co Shockproof electromagnetic relay
US2485727A (en) * 1945-03-07 1949-10-25 Gallina Harold Protective device for automotive electric circuit
US2535872A (en) * 1947-04-25 1950-12-26 American Telephone & Telegraph Signaling system
US2538789A (en) * 1948-09-01 1951-01-23 Ibm Sequence control circuit
US2576574A (en) * 1948-09-29 1951-11-27 Cochran Emilienne Fault indicating system for control circuits
US2586592A (en) * 1949-09-29 1952-02-19 Chambersburg Eng Co Timing system
US2600317A (en) * 1950-03-18 1952-06-10 Westinghouse Electric Corp Stabilized control circuit
US2621236A (en) * 1947-12-13 1952-12-09 Howard F Mason Circuit breaker system
US2676284A (en) * 1950-09-13 1954-04-20 Bendix Aviat Corp Fault protective system
US2707977A (en) * 1953-02-11 1955-05-10 Draper Corp Loom stop motion
US2784353A (en) * 1949-12-29 1957-03-05 Bendix Aviat Corp Generator protecting device
US2874376A (en) * 1954-10-21 1959-02-17 Holmes Electric Protective Com Local alarm circuit for burglar alarm systems
US3018421A (en) * 1959-02-26 1962-01-23 Westinghouse Electric Corp A. c. -d. c. electromagnet

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2440108A (en) * 1943-05-05 1948-04-20 Gen Electric Overcurrent protective system for a direct-current load circuit
US2447638A (en) * 1943-05-27 1948-08-24 Westinghouse Electric Corp Excitation control system for vapor electric devices
US2481431A (en) * 1943-08-10 1949-09-06 Ward Leonard Electric Co Shockproof electromagnetic relay
US2453486A (en) * 1945-01-01 1948-11-09 Picker X Ray Corp Waite Mfg Electronic timer
US2485727A (en) * 1945-03-07 1949-10-25 Gallina Harold Protective device for automotive electric circuit
US2535872A (en) * 1947-04-25 1950-12-26 American Telephone & Telegraph Signaling system
US2621236A (en) * 1947-12-13 1952-12-09 Howard F Mason Circuit breaker system
US2538789A (en) * 1948-09-01 1951-01-23 Ibm Sequence control circuit
US2576574A (en) * 1948-09-29 1951-11-27 Cochran Emilienne Fault indicating system for control circuits
US2586592A (en) * 1949-09-29 1952-02-19 Chambersburg Eng Co Timing system
US2784353A (en) * 1949-12-29 1957-03-05 Bendix Aviat Corp Generator protecting device
US2600317A (en) * 1950-03-18 1952-06-10 Westinghouse Electric Corp Stabilized control circuit
US2676284A (en) * 1950-09-13 1954-04-20 Bendix Aviat Corp Fault protective system
US2707977A (en) * 1953-02-11 1955-05-10 Draper Corp Loom stop motion
US2874376A (en) * 1954-10-21 1959-02-17 Holmes Electric Protective Com Local alarm circuit for burglar alarm systems
US3018421A (en) * 1959-02-26 1962-01-23 Westinghouse Electric Corp A. c. -d. c. electromagnet

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