US1814015A - Control system - Google Patents

Description

y 14, 1931;- I c. c. WHITTAKER 1,814,015"

' CONTROL SYSTEM Filed May 27, 1929 Supply OF Compressed Air INVENTOR 7 Charles C.WhittaKer BY I 7 ATTORNEY Patented July 14, 1931 UNITED STATES PATENT OFFICE CHARLES C. WHITTAKER, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR- TO WESTING- HOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYL- VANIA CONTROL SYSTEM Application filed May 27, 1929. Serial No. 368,425.

This invention relates to switching systems suitable for interrupting circuits carrying heavy currents at high voltages.

When it becomes necessary to utilize direct-current electrical apparatus, which consumes or delivers, at high voltages, currents of great magnitude, switching operations become a serious problem. In railway practice, propelling motors of large capacity, which take currents running into thousands of amperes, are required. \Vhen circuits carrying large currents at high voltages are established, it is difficult to interrupt them without causing arcing which will burn the switches.

Heretofore, in controlling the circuits for railway motors, the practice has been to provide accelerating resistors divided into sections and to utilize electro-magnetically operated switches for shunting the resistor sections to effect the acceleration of the motors in a step-by'step manner. In such systems, when it is desired to interrupt the motor circuit, a plurality of the resistorshunting switches may be opened before the line switch, in orderto introduce sufficient resistance into the motor circuit to reduce the current to a safe switchin value. Such practice leads to the installatlon of complicated switching equipments which occupy considerable space on the locomotives and are expensive and hard to keep in efficient working condition.

The object of the invention, generally stated, is to provide a switching system that shall be eflicient in operation and economically manufactured and installed.

A more specific object of the invention is to provide for introducing sufficient resistance into a circuit to reduce the current to a desired value at which switching operations may be performed to interrupt the circuit without excessive arcing.

Other objects of the invention will, in part, be obvious and will, in part, appear hereinafter.

The invention, accordingly, is disclosed in the embodiment thereof shown in the accompanyin drawing and comprises the 5 structural. eatures, combination. of elements and arrangement of parts that will be exemplified in the structure hereinafter set forth and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description, taken in connection with the accompanying drawing in which the single figure is a diagrammatic view of a switching system arranged in accordance with the invention.

In order that the construction and function of the switching system may be readily understood, it is illustrated as it may be applied to control the circuit connections of a motor. In this particular instance, a motor 10 is shown disposed to be connected to a source of power 11 which is illustrated as a trolley conductor.

As shown, acontact segment 12, which may be mounted on any suitable controller, is provided for establishing the necessary control circuits to initiate the operation of the switching system.

In addition to the accelerating resistor controlled by the switching system construoted in accordance with the invention, a main accelerating resistor 13 is provided and connected in series-circuit relation with the motor 10. An electro-magnetic switch 14 is disposed to be actuated to shunt the resistor 13 when the controller is moved to its second position. In this instance, only one step of acceleration. is provided, but it will be readily understood that, in practice. any desired number of steps in the acceleration of the motor may be obtained by increasing the number of accelerating resistors 13.

In this embodiment of the invention, a line switch 15 is provided to establish and interrupt the motor circuit. The line switch illustrated is of the electromagnetic type, but any other suitable type of switch may be utilized.

In order to reduce the motor current and the voltage that may be impressed across the switch 15, when it is opened and thereby prevent violent arcing, a carbon-pile resistor 16 is disposed to be connected in seriescircuit relation with the motor 10. It has been found that carbon-pile resistors, which are small in size, are capable of carrying large currents. Further, in view of the characteristics of a carbon-pile resistor, its internal resistance may be. gradually varied by subjecting it to a changing pressure and it ma beoperated to reduce the voltage that may e impressed on the switch 15, when opened.

The application of pressure to the carbonpile resistor may be effected in any suitable manner and, in this particular instance, an air-operated device is utilized. As shown, a cylinder 17, in which a spring-pressed piston 18 is slidably mounted, is connected, through an electromagnetic valve 19, to a pipe line 20 which leads from any suitable source of supply of compressed air, not shown. The piston is disposed in alignment with the carbon-pile resistor, and pressure may be applied to the latter by means of the plunger 21. In order to protect the carbon-pile resistor from shocks and to apply the pressure evenly, a spring 22. is inter-, posed between the plunger and the base of the resistor.

It will be noted that two contact members 23 and 24 are carried by a rod 25 depending from the piston 18. The lower contact member is adjustably mounted on; the rod 25 and is supported by a spring 26' to permit a predetermined movement relative to the rod.

The function of the different members of the system may be more readily set. forth by a description, of the operation. Assuming that it is desired to establish the motor circuit, the contact segment 12 is actuated to position 1. An actuating circuit for the electromagnetic valve 19 is established which extends from the battery 27', through conductor 28, a pair of contact members" bridged by the contact segment 12-conductor 29, overload trip 30, co-nductoriil, the. actuating coil of the valve 19 and conductor 32, to the battery.

The valve 19 is opened, and compressed air flows into the cylinder 17 to slowly actue ate the piston 18 upwardly and thus, apply pressure to the carbon-pile resistor 16. It will be observed that, as the piston 18 moves upwardly, the contact member 21, disposed on the rod 25, will bridge a pair of contact members to establish an actuating circuit for the line switch 15. v

The line-switch-actuating circuit may be traced from the energized conductor 29, through conductor 33, the contact member 24,conductor 34, the actuating coil of line switch 15 and conductor 32, to the battery. Therefore, the line switch 15 will be operated almost immediately after the piston 18-begins its upward movement, and. a motor circuit will be established which extends from trolley conductor 11, through the conductor 35, the carbon-pile resistor 16, conductor 86, the line switch 15, conductor 37 resistor 13 and the motor 10, to ground at 38.

The resistance of thecarbon-pile resistor 16 is. gradually reduced and the motor accelerated. When the resistance of the. car.- bon-pile resistor 16 is reduced'to a negligible value, it is desirable that it be shunted.

As shown, an electromagnetic switch 39 is provided to shunt the carbon-pile resistor. In order to actuate the switch 39 at the proper time, the contact member 23 is disposed to bridgev a pair of contact. members to establish an energizing circuit. As will be observed, the,- contact member 23 is; so disposed onv the rod 25 that, the: actuating circuit for the. switch 39 is established after the full pressure has been applied to the carbonepile resistor, thereby reducing its. re sistance to a minimum;

The actuating circuit for the switch; 39 may be traced; trom theenergi-zed conductor 31, through the contact. member. 23,. com duetorv 40, actuating; coiL o switch 3.9 and conductor- 32, to the battery, Upon the establishment. of. this. circuit,. the switch; is operated and the carbon-pile; resistor-shunted from the circuit.

Assuming that. thecontact segment 1251s actuated to its, second positiom. an; actuating circuit. for the switch 14% 'm: established. This circuit extends; from the battery.- 27, through conductor 28, the. Contact. mom bers-hridged by the: contact; segment 12- the. actuating coil of the line switch. 14.241111 conductor-32, to the bmttery. The switch 14- is operated. and. the. resistor 1.3. shunted.

The motor circuit; extends from'thetroL ley conductorl-l, through: conductor 35,;the actuating coil: ofr the. overload. relay 30;. switch 39,.line switch; 15,.switch14 and the motor 10, to ground at 38.

Assuming that it is. desired to; interrupt the motor circuit carrying a; heavy" current which, in the case of railway motels, will probably reach; a: value.- of 3.000 on i000." amperes, at. ahigh voltage, the contact segment is actuatedto its off position, and the: switch.- ing operation is: periiormed; without violent arcing.

The actuating circuit for the switch 14 is interrupted, and the switch permitted to open, thereby introducing the; resistor 13 into the motor circuit;

The actuating circuit; forthe: valve 19 is interrupted, and. the supply; of compressed air to the cylinder 17- is shut oft thus gradually exhausting the air from the Atthe beginning of: the downward movement of the piston, the contact member 23 is disengaged from the contactv terminals which. it; bridged, and the. actuating circuit for the switch 39 is interrupted. The switch 39 is actuated to its open position to interrupt the shunt around the carbon-pile resistor 16, causing the latter to carry the full motor current. As the piston 18 moves downwardly, under the biasing action of its spring and the spring 22, the ohmic resistance of the carbon-pile resistor is gradually increased until the resistance in the motor circuit is increased to a value at which switching operations may be successfully performed without subjecting the line switch to excessive arcing.

When the current in the motor circuit is reduced to a desired value, the contact member 24 is disengaged from the contact terminals which it bridged, and the actuating circuit of the line switch 15 is interrupted to permit the switch to open and thus interrupt the motor circuit.

It will be observed that the contact member 23 is disposed in a predetermined position relative to the piston 18 to establish a circuit to shunt the carbon-pile resistor 16 from the motor circuit when its resistance value is reduced to a negligible quantity and to open the shunt circuit and reestablish the motor circuit through the resistor 16 when the contact segment 12 is actuated to its off position, to effect the interruption of the motor circuit. Further, the contact member 24 is disposed to maintain the line switchactuating circuit established to retain the line switch closed until the carbon-pile resistor is connected into the motor circuit, and until the pressure applied to the piston 18 has been reduced to cause a desired increase in the resistance in the motor circuit and a desired decrease in the motor current.

Therefore, I have provided a system which responds to the actuation of a master switch or controller to reduce the motor current and effect switching operations to finally interrupt the motor circuit without excessive arcing. Further, the system involves only a small amount of apparatus which is compact and may be conveniently employed on locomotives and the like.

Since certain changes may be made in the above construction, and different embodiments of the invention may be made without departing from the scope thereof, it is intended that all. matter contained in the above description and shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. In a switching system for controlling the circuit connections between a translating device and a source of power, in combination, a switch disposed to connect the translating device to the source of power to establish a work circuit, a carbon-pile resistor connected in circuit relation with the translating device, means for applying pressure to the carbon pile to vary its resistance, means carried by the pressure-applying means and disposed to control the operation of the line switch in a definite time relation to the operation of the pressure-applying means, the means for controlling the application of pressure to the carbon pile to vary the resistance being disposed, relative to the line-switch actuating means, to provide for the introduction of resistance into the work circuit before the line switch is actuated to interrupt the circuit.

2. In a switching system for controlling the circuit connections between a translating device and a source of power, in combination, a switch disposed to connect the translating device to the source of power, a carbon-pile resistor connected in circuit relation with the translating device, means for applying pressure to the carbon-pile resistor to vary the resistance of the circuitcontrolling means for effecting the operation of the pressure-applying means, and a contact member carried by the pressureapplying means and disposed to control the operation of the switch in a definite time relation to the operation of the pressure-applying means, said contact member and said pressure-applying means being disposed relative to one another to provide for an increase in the resistance offered by the carbon-pile resistor before the line switch is actuated to interrupt the circuit.

3. In a switching system for controlling the circuit connections between a translating device and a source of power, in combination, a switch disposed to connect the translating device to the source of power, a carbon-pile resistor connected in circuit relation with the translating device, means for applying pressure to the carbon-pile resistor to vary the resistance, circuit-controlling means for effecting the operation of the pressure-applying means, a contact member actuated by the pressure-applying means to control the operation of a line switch, said contact member and said pressure-applying means being disposed relative to one another to provide for an increase in the resistance offered by the carbon-pile resistor before the line switch is actuated to interrupt the circuit, a switch disposed to shunt the carbon-pile resistor, and a second contact member actuated by the pressure-applying means to control the operation of said shunting switch.

4. In a switching system for controlling the connections between a source of power and a translating device, in combination, a line switch for establishing and interrupting circuit connections between the translating device and the source of power, a carbon-pile resistor connected between the source of power and the translating device to control the flow of current in the circuit, a switch for shunting the carbon-pile resistor, means for applying pressure to the carbon-pile resistor to vary its ohmic resistance, switching means actuated by the pressure-applying means to effect the operation of the line switch and the shunting 7 switch said switching means carried by the pressure-applying means being disposed to provide for the opening of the shunting switch and the reduction of the pressure applied to the carbon-pile resistor, thereby increasing the resistance of the circuit before the line switch is actuatectf In testimony whereof I have hereunto subscribed my name this 23rd day of May,

CHARLES ,C. WHITTAKER.

Images