US1708886A - Automatic circuit-controlling device - Google Patents

Description

A i-1'19, 1929. .1. A. JACKSON 1,708,886

' I I AUTOMATIC CIRCUIT CONTROLLING DEVICE Filed Aug. 26, 1925 Inventor-z James A. Jackson, by M12 His Attorney Patented Apr. 9, 1929.

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JAMES A. JACKSON, OF SCI-IENEO TADY, NEW YORK, ASSIGEJOP, T0 GENERAL ELECTRIC COMPANY, A CORPORATION 05' NEVI 1 03K.

AUTOI'IIATIC CIRCUIT-CONTROLLING DEVICE.

Application filed August 26, 1925. Serial No. 52,662.

This invention relates to automatic controlling devices for electric circuits adapted to be energized troma plurality of sources 'ofditlering voltages, andit has for its object the provision oif automatic electroresponsive switch mechanism for disconnecting the controlled circuit from a high voltage source and connectingthe circuit to a lower voltage source when the current in the circuit exceeds a certain value and for automatically reconnecting the circuit to the higher voltage source when the current decreases below the predetermined value.

Although of general application to power circuits, motor circuits, and the like, the invention is particularly advantageous when applied to control the energization of the train power conductors f in an automatic electric railway system of the type described and claimed in the co-pending patent application of Robert H. McLain, No. 751,228, filed November 21, 1924, and assigned to the assignee of my present invention. In the McLain type of automatic railway electric system the cars are driven by alternating current motors and are arranged to be operated upon a main track which is normally energized from an alternating on rent source of relatively high constant frequency without operators or motormen thereon.

hen applied to such an automatic, electric railway system, my present invention provides an automatic circuit controlling device capable of restarting trains. of motor driven cars which may be stopped on the main track upon failure of the source normally energizing the same without excessively overloading the source or excessively overheating the driving motors of the cars. This is accomplished in accordance with my invention entirely automatically by means of switch mechanism arranged to transfer the energization of the train conductors from the high voltage source to a low voltage source when the starting and accelerating current of the stalled trains oi? cars onceeds a certain value, and to reconnect the train conductors to the high voltage source after the motor starting current has decreased to the normal running value.

In the accompanying drawing the inven tion is illustrated as applied to such an autovniatic electric railwa system in order to explain the principles thereof, although it will be understood that the invention may be used in other connections. The single figure of the drawing diagrammatically shows a preferred form of automatic electroresponsive switch mechanism for transferring the energization of the train power conductors in an electricrailway system between a high voltage source and a low voltage source responsively to the current in the train conductors.

In the drawing the train power conductors comprising the track T and the trolley T are arranged to receive power from the high voltage alternating current supply line L through the. transformer 10, having a primary winding 11 and a tapped secondary winding 12. One terminal of the secondary winding .12 is permanently connected to the track T The electromagnetic switch 13 controls the connection of the high voltage terminal 14 of the secondary winding 12 to the trolley wire T while the electromag netic switch15 controls the connection of the intermediate low voltage tap or terminal 16 of the secondary winding 12 to the trolley wire T Eachof the electromagnetic switches 13 and 15 is biased to the open position. The electroresponsive relay 17 is provided with a normally closed contact 18 and a normally open contact. 19 for controlling the energization of the operating windings of the respective electromagnetic switches 13 and 15. v

The relay 17 is provided with a pair of windings 21 and 22, theformerof which is connected in the circuit through which the trolley wire T is energized from the high voltage terminal 1a of the secondary winding 12, while'the latter is connected in the circuitthrough which the trolley wire T is energized from the low voltage tap .16 of the secondary winding 12.

When the supply lines L are energized and trains of cars are operating upon the track T under normaloperating conditions relay 17 is in the position in which it is shown and the operating winding of electrolnagnetic'switch 13 is energized through the normally closed relay contact 18. Thus the electromagnetic switch 13 is closed to connect the trolley wire Cl to the high volt-- age terminal 14 oi. the secondary winding 12. The normal operating current supplied to the driving motors of the cars from the high voltage terminal 14 through the winding 21 of relay 17 is insufficient to operate the relay from the position in which it is shown.

In case of failure of the source supplying power to the supply lines L the driving motors of the cars operating upon. the track T are deenergized and hence the cars slow down and come to rest. Also the operating winding of electromagnetic switch 13 is deenergized and the switch operates to the open position. Upon the return of power to the supply lines L the electromagnetic switch 13 is reenergized and reconnects the trolley wire T to the high voltage terminal 14 of the secondary winding 12 to apply full voltage to the driving motors of the stalled train of cars. Under these conditions the starting current of the motor increases to abnormally high values, for example, from 300 to 400% of normal running current. The excessive value of current through the operating winding 21 of relay 17 serves to operate the relay to open the contact 18 and close the contact 19. Upon the resulting deenergization of the electromagnetic switch 13, the switch opens in accordance with its bias. Upon the closure of contact 19 the operating winding of electromagnetic switch 15 is energized through a circuit extending from the terminal of secondary winding 12 connected to track T through the contact 19, the operating winding of switch 15, and the operating winding 21 of relay 17, to the high voltage terminal 14 of the secondary winding 12. Switch 15 at once closes and connects the trolley wire T to the low volttage tap 16 of the secondary winding 12 through the operating winding 22 of relay 17. The reduced voltage now applied to the driving motors of the cars upon track T maintains the starting and accelerating current within sate operating limits, for example, 200% of normal running current. The driving motors gradually accelerate the cars to normal running speed. During this interval the current taken by the motors from the low voltage tap 16 gradually decreases. lV hen the current in the train conductors T and T decreases bQlOv' a certain value, for example, 125% normal running value, the operating winding 22 of relay 17 is insufiiciently energized to maintain the contact 19 in the closed position. Upon the resulting opening of contact 19, electromagnetic switch 15 is deenergized and opens to disconnect the trolley wire T. from the low voltage tap 16. At the same time the contact 18 reestablishes the energizing circuit for electromagnetic switch 13. This switch then closes to reconnect the trolley T to the high voltage terminal 14 of the secondary winding 12 for normal running operation of the cars.

Thus it will be seen that by means oi my invention the train conductors T, and T are normally energized from the high voltage terminal 14 as long as the current in the control circuit is below a predetermined value, while the energization of the track conductors T and T is shifted from the high voltage 14 to the low voltage tap 16 and maintained connected to the latter as long as the current of the track conductors exceeds a certain value.

While I have described the invention in connection with a power circuit for electric railways adapted to be energized from a high and a low voltage source, the invention may be applied with equal advantage to the control of other circuits.

lVhat I claim as new and desire to secure by Letters Patent of the United States is 1. An automatic controlling device for electric circuits adapted to be energized from a high voltage source and from a low voltage source comprising electrically operated switch mechanism for separately connecting the controlled circuit to each source, an electroresponsive relay having a pair of operating windings, each connected under the control of said switch mechanism to be energized responsively to the current supplied to the circuit from a corresponding one of said sources and arranged to be operated to one position when the current in the controlled circuit is below a predetermined value and to a second position when the current in the circuit is above said predetermined value, and connections controlled by said relay in said one position for effecting operation of said switch mechanism to connect the controlled circuit to the high voltage source and .in said second position for ellecting operation of said switch mechanism to connect the controlled circuit to the low voltage source.

2. The combination of an electric circuit, a transformer having a high voltage and a low voltage terminal for supplying power to said circuit, a separately operable electromagnetic switch for connecting each of the said terminals to the circuit, and an electroresponsive relay having a pair of operating windings, one connected under the control of one of said switches to be energized by the current supplied to said circuit from the high voltage terminal of the transformer and the other connected under the control of the other of said switches to be energized by the current supplied to said circuit from the lowvoltage terminal of the transformer, said relay being biased to one position when the current supplied to the circuit from either terminal of the transformer is below a predetermined value and arranged to operate to a second position When the current supplied to the circuit exceeds said Value, and connections controlled by said relay in said one position for normally energizing the first electromagnetic switch to connect the electric circuit to the high Voltage ter- Ininal and in said second position to energize said second contactor to connect the electric circuit to the low Voltage terminal.

In Witness whereof I have hereunto set my hand this 25th day of August, 1925.

JAMES A. JACKSON.

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