US1915961A - System of motor control - Google Patents

Description

June 27, 1933. SUK-SDORF v 1,915,961

SYSTEM OF MOTOR CONTROL Filed July 17. 1951 Inventor: Alfred Suksdorf,

H is Attorney.

Patented June 27, 1933 A UNITED STATES PATENT oFFICE'J 1 ALFRED S'UKSDORE, OF SCHENEC'IADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK Application filed Ji11y 17,

'My invention relates to systems of motor control, and more particularly to such systems wherein a device is positively operated by a motor to a limit of operation.

Although the invention is not necessarily limited thereto, it is particularly applicable to the control oi an electric motor for operating a valve. When a motor operated valve is opened in a high pressure steam line, it is extremely desirable to have a control system which will accomplish the quic reclosing of the valve.v For instance, if a pipe should burst as the valve is being opened, the necessity of the speedy reclosing of the valve is obvious, Therefore, an object of my invention is the provision of a simple and reliable control system giving at all times complete control of an electric motor operating a device such as a valve between predetermined limits. 1 V

In carryingout my invention in one form, I provide a single control means, such as a push button, together with direction con trolling switches arranged so that the operation of the single control means results in the motor when operating in one direction being plugged to standstill; and started up in the reverse direction, whereby a valve which is being opened may speedily be closed. In order to. reduce the torque of the motor as the valve reaches its full closed position, a limit switch is arranged to be operated by the valve as it nears its closed position, thereby introducing in series with the motor a torque and speed reducing resistor. The seating of the valve stalls the motor to standstill and a time switch is provided to deenergize the motor shortly after it has been stalled. 1

For a more complete understanding of my invent-ion, reference should now be had to the drawing, the single figure of which shows a simplified diagram of a system of motor control.

1 Referring to the drawing, I have shown my invention in one form as applied to the control of a motor 10 which is connected to operate a valve 11, illustrated in its closed position and comprising a gate 12 seated in,

a pipe 13. The motor is connected to the 1931. Serial No. 551,470.

gate through gears 14 and 15, the latter of which is provided with a threaded bore cooperating with a threaded rod '16 secured to the gate l2. It will be understood that the gear 15 is restrained from vertical movement so that when it is rotated in one direction or the other the valve is either opened or closed. The motor 10 is shown of the direct I current type, provided with the usual commutating field 17 and a series field 18, and it may be connected to suitable direct current supply lines 19 and 20 by electromagnetically operated direction controlling switches 21 and 22. A shunt field 23 for the motor is connected during operation directly across the supply lines 19 and 20.

Briefly stated, the directional switches 21 and 22 are controlled to initiate the starting their closed positions, are also provided and arranged to be opened respectively when the valve nears its open and closed positions, whereby the motor is automatically stopped at the limits of travel of the valve.

In stopping the'motor as the valveqll is closed, the limit switch 28 operates to open a switch 29 whereby a stalling resistance 30 is connected in the armature circuit of the motor, and to initiate the opening of a time switch or relay 31, which has a time interval sufficient to disconnect the motor shortly after it has closedthe valve and stalled.

In the operation of my invention, in order to open'the valve 11, the normally open push button 26 is closed, establishing an energizing circuit to close the direction switch 22, which circuit may be traced fromthe supply line 19 through the push button switches 24, 25 and 26, conductor 32, the operating coil 33 of the switch 22 and the limit switch 27, to the other supply line 20. A holding circuit is also established for the operating coil 33, which may be traced from the supply line 19, push button switches 24 and 25, conductor 34, the switch 35 which is operated with the switch 22, coil 33,. limit switch 27 to the other supply line 20. The closing of the switch 22 established the motor circuit which may be traced from the supply line 19 by conductor 34', the upper contact of switch 22, through the armature of motor 10, the commutating,

field 17, and thence by conductor 36, the lower contact of the switch 22, the series field 18, by conductor 37, the switch 38 which is operated with the switch 22 to the other supply line 20. The motor now starts in a direction to move the valve 11 tofull open position. As

the valve nears its open position, the limit switch 27 is opened by the, upper end of the screw threaded member 16 striking a pivoted arm of the limit switch 27, whereby the circuit of the operating coil 33 of the switch'22 is opened and the switch 22 immediately opens to deenergize the motor.

If it is now desired to close the valve from its full open position, the push button 25 is depressed, establishing a circuit to close the switch 21 from the supply line 19, the stop button 24, the push button 25, by conductor 39, through the operating coil 41 of switch 21 to the other supply line 20. The closing of switch 21 establishes connection for the motor,

-which may be traced from the supply line 19 by conductor 34,the upper contact of the switch 21, the commutating'field 17, through the armature of the motor and thence by conductor 40, resistor 30, to the lower contact of switch 21,.series field 18, conductor 37, the switch 42 which is operated with the switch '21, and to the other supply line 20. The depressing of the push button 25 also establi-shesa second circuit immediately closing the time switch 31, which circuit may be tracedjfrom the supply line 19, the stop but ton 24, the push button 25, by conductor 43, to the operating coil '45 of the time switch 31,

to the other supply line 20. A holding circuit for the operating coil 41 of the switch 21 is thereby established, which circuit may be traced from the supply line 19, the stop button 24, by conductor 44, time switch 31, operating coil 41 of switch 21 to the other supply line 20; His to be observed that the closing of the switch 21 closes a switch 46 actuated therewith, which switch closes the circuit of the operating coil 47 of the switch 29, and this circuit may be'traced from supply line 19, the stop button 24, by conductor 44,

through switch 46, the operating coil 47 of switch 29, conductor 48 to the limit switch 28 and to the other supply line 20. The limit switch 28, of course, is closed since under the conditions assumed the valve is in full open position and the connections are made to close the valve.

andcompletes a shunt circuit around the The switch 29 thereupon closes slow-down and torque reducing resistor 30 whereupon the motor 10 rotates at full speed to close the valve. The closing otswitch49 operated with the switch 29 establishes a holding circuit for the operating coil 45 of the time switch 31, which may be traced from supply line 19, the stop button 24, conductor 44, switch 49, the operating coil 45 to the other supply line 20. p

' As the valve nears the closed position it opens the limit switch 28, which breaks the holding circuit of the coil 47 whereupon the switch 29 opens inserting the resistor 30 in the motorcircuit. The resistor 30 serves to reduce the torque of the motor to about 25% valve at'greatly reduced torque and stalling to standstill. Inasmuch as the holding circuit full load torque, the motor then seating the for coil 45 of the time switch 31 is also broken I by the switch 49 opening with the switch 29,

the time switch 31 opens a predetermined time after its energizing circuit has been broken, thus breaking the holding circuit to the operating coil 41 of the switch 21 which immediately opens deenergizing the motor. Under the conditions assumed it is to be observed that the valve 11 has been positively operated to both its full open and full closed positions.

By my invention, -pr ovision is made for" an emergency and the system responds for the emergency when the single push button 25' is depressed. The motor is thereby plugged to a standstill and is started up in the reverse direction to close the valve either ing of the push button 25 opens theswitch.

22 by breaking the holding circuit of the operating coil 33 of'the switch 22,-since this holding circuit is normally energized through push button 25; The operating coil 41 of switch 21 is simultaneously energized closing this switch and establishing the motor I 9 connections for reverse operation for closing the valve. As is well understood in the art,

the establishment of these connections quickl y plugs the motor 10 to standstill, after which in accordance with my invention the motor immediately starts in the reverse direction to close the valve 11. 1

WVhether or not the motor rotates at full speed and full torque depends on the position oit'v the threaded rod 16 of the valve 11 and limit switch 28 when push button 25 was depressed. If the valve has not opened sufliciently to permit the closing of limit switch 28, the operating coil 47 of switch 29 may not be energized. The resistor 30 is effective to limit the motor torque protecting the valve from being cracked by the gate 12 being driven by the full torque of the motor into closed position.

When the motor 10 has opened the valve 11 sufliciently to permit the limit switch 28 to close and the push button 25 is then depressed to plug the motor to standstill and start it up in the reverse direction, the circuit to the operating coil 47 of switch 29 is energized from the supply line 19, push button 24, conductor 44, switch 46, coil 47, the limit switch 28 and to the supply line 20. The motor now rotates at full speed and full torque to close the valve since a short circuit has been com pleted around the resistor 30. The torque of the motor 11 is again reduced, however, as the valve 10 nears its closed position by the threaded rod 16 of the valve 11 opening the limit switch 28 and the consequent opening of switch 29 and the reinsertion of resistor 30 in the motor circuit. Thus it will be observed that the valve 11 is protected at all times inasmuch as it is always closed at approximately the same speed and the same motor torque whether from full open position or from any intermediate position.

While I have shown a particular embodiment of my invention, it will be understood, of course, that I do not wish to be limited thereto since many modifications may be made, and I, therefore, contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In a motor control system, the combination with a device movable between predetermined limits, ofa motor for operating said device, switching means for controlling the energization of said motor for each direction of operation, a push button for operating said switching means to deenergize said motor when it is operating in a predetermined direction and to energize said motor for reverse operation, a time delay relay for maintaining a holding circuit for said switching means when it has been operated for one direction of rotation, a holding-circuit for said time delay relay, limit switch means for breaking said holding circuit of said relay whereby said time delay relay opens a predetermined time after said limit switch has been operated to break the holding circuit of said switching means thereby deenergizs ing motor.

2. In combination, a device movable between predetermined limits, a driving motor therefor, a direction switch for controlling the energization of said motor for one direction of rotation, a time opening relay for establishing a holding circuit for said direction'switch, a single control means for energizlng said directlon switch and said time opening relay, a torque reducing resistor normally connected in circuit with said motor, switching means for short circuiting said resistor, contacts arranged to be'closed with said switching means, a normally closed limit switch arranged to be opened by said device asit approaches one of said limits, connections formaintainingthe energization of said direction switch when said contacts close and for deenergizing said switching means when said limit switch is opened, said connection including said contacts operated with said switching means which contacts control the energization of said time opening relay.

'3. In combination, a device movable between predetermined limits, a driving motor therefor, a direction switch for controlling the energization of said motor for one direction of rotation, a torque reducing resistor connected in said motor circuit, switching means for short circuiting said resistor, a single control means for energizing said direc tion switch and said switching means, a time ing device responsive to the operation of said switching means for maintaining a holding circuit for saiddirection switch, a limit switch arranged to be opened by said device as it approaches one of its limits for deenergizing said switching means whereby said device is driven to one of its limits of operation under reduced torque and after a time delay the said motor is deenergized.

4. In a motor control system, the combination with a device movable between predetermined limits, direction switches for controlling energization of said motor for each direction of operation, a torque reducing resistor, connections for connecting said resistor in circuitwith said motor only when one of said direction switches is closed, a single control means for operating one of said direction switches to deenerglze said motor when it is operating 1n a predetermined direction and to energize said other direction switch for reverse operation, timing means responsive to the operation of said single control means for establishing a holding circult for said direction switch, switching means responsive to the operation of said dihand.

ALFRED SUKSDORF.

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