US1401638A - Motor-control system - Google Patents

Description

F. M. PARKS.

MOTOR CONTROL SYSTEM. APPLICATION mm FEB. 13, 1920.

1,401,638. v Patented Dec. 27, 1921.

WITNESSES: INVENTOR ATTORNEY UNITED STATES PATENT OFFICE,

FRED M. PARKS, OF MUBRYSVILLE, PENNSYLVANIA, ASSIGNOR T WESTINGHOUSE m'zc'rnrc AND MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

MOTOR-CONTROL SYSTEM.

Specification of Letters Patent.

Patented Dec. 27,1921.

Application filed February-13, 1920. Serial No. 358,357;

Motor-Control Systems, of which the following is a specifications I I My invention relates to motor-control systems and it has particular relation to such systems are employed to control the speed and direction of operation of electric motors by changing the degree of excitation and the polarity of a separately excited generator. My invention has, for one of its objects, to provide a simplified system in which the generator field excitation ,is automatically decreased during acceleration and increased" during deceleration of the motor.

Another objection of my inventlon is to provide a control system in which the master switch may be moved quickly from one acceleration or dece eration of the motor. I

extreme running position to the other extreme running position, or to any intermediate position, without danger of injury to the apparatus.

Another object of my invention is to insure the interruption of ally-control circuits when the current traversing the motor circuit increases to-a rohibitive value during Further objects of my invention are set forth in the specification. I f

The single figure of the accom anying drawing is a diagrammatic view 0 "a control system embodying my invent kin.

' The system shownin the drawing comprises a separately excited motor 1, which has a shunt field-magnet winding 2, and a generator '3 which has a shunt field-magnet winding 4. The motor.and generator are connected in closed-circuit relation and are energized from an" exciter which has an armature and a shunt field-magnet wind- I ing 6. A push-button switch 7 whichhas positions respectively designated ,Start and Stop, controls the operation of a.

double-pole switch 9, that serves to connect the exciter to the circuit of-the field-magnet windings 2 and.4. A master switch 8 controls the operation of a pair of double-pole directional switches 10 and 11 which govern the direction of excitation of the field-magnet winding 4, and a' series of accelerating switches 12, 13, 14 and 15 which control the degree of excitation of the field-magnetwinding 4 by successively shunting portions of a resistor 23 from the circuit of the fieldmagnet Winding.

A pair of differential relays 24 and 25 respectively control actuating coils 37 and 38 of auxiliary switches-39 and 40. The differential relays 24 and 25 respectively have series actuating coils 41 and 42 that are energized in accordance with the current traversing .the motor and generator circuits,

and voltage coils 43 and 44 that are energized in accordance with the polarity and degree of excitation of the field-magnet winding 4. Coils 41 and 43 of the relay 24 are. wound to normally assist each other in magnetizing the core member of the relay, while the corresponding coils 42 and 44 of the relay 25 are wound in such manner as to oppose one another when'the motor 1 and the generator 3 operate to perform their normal functions. v

The auxiliary switch 39 controls a circuit for shuntinga portion 45 of an auxiliary resistor 46 from the circuit of the field-magnet winding 4 to decrease the generator excitation. The auxiliary switch 40 controls a circuit which shunts resistors 23 and 46 from the circuit of the field-magnet windhe master switch 8 has a contact segment 26 that may be moved'through a series of 5 positions a, b, 0', d'and' e, which correspond to the respective steps in the forward direc- -tion of operation of the motor 1 and a series of positions a', b, 0', d" and e, which correspond to the reverse direction of opera- 7 tion of the motor. The segment 26 is adapted to successively engage contact fingers 27 to 30, inclusive, when moved through the series of forward positions and to successively engage contact fingers 31 to 34, inelusive, .when moved in the reverse direc-' 'tion, to respectively energize coils 19 to 22, inclusive, of the accelerating switches for controlling resistor 23. Contact fingers 35 and 36 respectively control the energization of coils 17 and-18 of directional switches 10 and 11 when the contact segment 26 is moved to the first'forward operative position to initiate operation of the motor in either the forward or. the reverse direction; I I

A current-limit relay 47, which has a series actuating coil 48, interrupts the associated control circuit when the current traversing the armaturecircuit of the motor and generator exceedsa predetermined value.

A pair of track-limit switches 49 and 50 represent devices for limiting the operation of the motor within predetermined limits and are adapted to interrupt the associated control circuit when the motor reaches a predetermined position in its operation. A lug 51 represents a projection from an elevator car, or a like mechanism that is operated by the motor 1, which engages track-limit switch 49 to interrupt the circuit established thereby when the elevator car travels in one direction, and to actuate the track-limit switch 50 to interrupt the circuit established thereby when the elevator car travels-to its extreme position in the other direction. After the opening of either of the track-limit switches, by the action of the projection 51, the-repassing of the projection closes the switch to reestablish the circuit conditions shown in the drawing.

The control panel 52, which is shown in dotted outline, has a push-button switch 7, a

pair of emergency push-button switches 53 and 54 that are respectively designated Forward and Reverse, and a pair of indlcat- 'ing lights.55 and 56 that are respectively marked thereon. The remaining details of the circuits and the sequence of operation of the several switches will be hereinafter described in connection with the operation of the system.

In order to initiate the operation of the system, the push-button switch 7 is depressed a sufficient degree to complete an energizing circuit which extends from the positive terminal of the exciter 5, through relay 47, track limit switches 'and 49, push button switch 7, and the actuatingcoil 16 of switch 9, to the Red and Green, mounted negative terminal of the exciter armature.'

The above circuit energizes actuating coil 16 to close switch 9 which effects the energizetion of field-magnet winding 2.

In the ofl or illustrated position of the master switch 8, a circuit extends from the positiveside ofthe exciter armature 5, through the switch 9 to contact segment 26 of master switch 8 to positively energize the contact segment.

When the master switch 8 is moved to position a, which corresponds to the first forward operating position, a circuit is completed which extends from the positively energized contact segment 26 of the master switch, through contact finger 35, actuating coils 17 of the directional switch 10, and switch 9, to the negative side of the exciter armature 5. The switch 10 closes to complete the main exciting circuit. This is the nitial operating position for the motor and 1s the stage in normal operation at which the generator voltage is of lowest value.

When the master switch is actuated segment 26 successively engages coacting contact fingers 27 to 30, inclusive, to gradually shunt the resistor 23 from the circuit of the field-magnet winding 4and thus to accelerate the motor 1 by increasing the applied voltage. When the master switch occupies position 6, the motor is normally operating at its maximum speed in the forward direction at the highest normal generator voltage.

If the master switch 8 is moved to position a, which corresponds to the first position for the reverse direction of operation of the motor, contact finger 36 engages the positively energized contact-segment 26 of the master switch 8 to effect the closing of switch 11 by completinga circuit from contact finger 36 through actuating coil 18 to the negative fide of the exciter circuit. If thecontroller seg. ment 26 is actuated through the remaining positions I), 0, d and e, the switches 12, 13, 14 and 15 close to shunt successive portions of the resistor 23 from the circuit of thegener- 'ator field-magnet winding 4. Position 0 When the direction of operation of the motor is reversed, the direction of the current normally traversing the circuit of armatures 1 and 3 is reversed. Since the; coils 41 and 42 are energized by the motor current and the coils 43 and 44 are energized in accordance with the polarity and degree of excitation of field-magnet winding 4, the relative directions of energization of the pairs of coils is the same for both directions of operation of the motor.

Assuming that the master switch 8 occupies an intermediate position, and that the motor current increases to a predetermined maximum value by reason of a sudden increase in load or a sudden movement of the master switch 8, the coils 41 and 43 of relay 24 effect the opening of the relay 24 and the interruption of the energizing circuit for coil 37 to open switch 39.

The switch 39 opens to insert portion 45 of resistor 46 in the circuit of the field-magnet winding 4 to reduce the degree of energization of the generator 3. The relay 24 continues to operate in the manner of a fluttering relay until normal current conditions are established in the motor circuit.

The coils 42 and 44 are so wound as to oppose each other duning normal. operation of the motor and, the relay 25, therefore, re

mains inoperative during such normal opnet winding. When generating conditions prevail in the motor 1, the coils 41 and opposeeachother, and coils 42 and 44 assist each other in vmagnetizing their respective core members. The relay 24 is, therefore, maintained in its closed position during generator operation of the motor 1, whereas the relay 25 closes when the current traversing the motor circuit under the same conditions increases to a predetermined value.

When the current traversing the motor circuit increases sufficiently to close relay 25, a circuit is completed from the positive side of the exciter 5, through relay 25 and actuating coil 38 of the auxiliary switch 40, to the negative side of the. exciter circuit. The closing of switch 40 excludes resistors 46 and 23 from the circuit of the field-magnet winding 4 to increase the generator voltage. Theincreased generator voltage opposes that of the motor 1 and operates to reduce the excessive value of the current that traverses the motor and generator circuit. The relay 25 continues to operate in the manner of afluttering relay until normal current conditions' are again established in the motor circuit.

It will, therefore, be understood that, even though the master switch be moved quickly to the final operating position, the relay 24 operates as a fluttering relay to limit the degree of excitation of the field-magnet winding 4 and to maintain the current traversing the motor circuit between predetermined safe limits during normal motoring operation.

Furthermore, if the motor 1 assumes generating characteristics, and a current of predetermined maximum value traverses the motor armature, the relay 25 operates to increase .the excitation of the field-magnet winding 4 and thereby limit the degree of generation of the motor 1 within predetermined safe limits while the relay 24 is maintained inoperative.

Operation of the elevator car beyond certain points is usually hazardous, and the track limit switches 49 and 50 prevent movement of the car beyond such predetermined points. i

If it is assumed that the elevator car passes track limit switch 49, the switch in terrupts the circuit for actuating coil 16 to effect the opening of switch 9 and thereby deenergize the system.

The auxiliary push-button switches 53 and 54 provide means for returning the elevator to a position of normal operation without disarranging the normal circuit relations of the system.

Normal operation of the system' is reestablished after track limit switch 49 opens by depressing push button 53 to complete a circuit from the positive side of the exciter through overload relay 47, track limit switch 50, push-button switch 53, interlock 60, pushbutton switch 7 and actuating coil 16 to the negative side of the supply circuit. If, during the time that the push button 53 is depressed, the master switch 8 is moved to position a, which corresponds to the first operative position for the reverse direction of operation f the motor 1, a circuit is completed for actuating coil 18 of switch 11in the manner described in connection with the initial operation of the system.

' If, however, the elevator car is operated in an opposite direction a sufficient distance t open track limit switch 50, further operation of the motor 1 is arrested by the interrupter of the energizing circuit of the actuating coil 16. Reestablishment of'the control circuit for operating the car in a forward direction is effected by depressing push-button switch 54 to effect the closing of switch 9 by completing a circuit from the positive side of the exciter circuit, through overload relay 47, interlock 61 that is mechanically operated by switch 11, push-button switch 54, track ,limit switch 49 and push-button switch 7, to the negative side of the control circuit.

It will be noted that each of the track limit switches has a circuit in shunt relation therewith which includes one of the emergency push-button switches 53 and 54 and an interlock that is maintained closed when the corresponding directional switch is open. This arrangement of circuits provides a system in which the operation of the elevator 100 is prevented except in a direction opposite to that obtaining when its motion wasarrested. This insures absolute safety of the system and, even though the wrong push button is depressed, the movement of the car 105 in the wrong direction is prevented by the respective interlocks and 61.

By mounting the main starting switch 7, emergency push-button switches 53 and 54 and indicating lamps 55 and 56 on the auxihary panel 52, a compact panel board is provided which contains all emergency apparatus and the main starting switch and. also, indicates the condition of the circuits through the illumination off'the lamps 55 115 and 56.

Although I have describeda simple and preferred application of my invention, it is capable of various modifications and I desire, therefore, that only such limitations 120 shall be imposed as are indicatedby the spirit and scope of the appended claims.

I claim as my invention:

1. A control system comprising a dynamo-electric machine adapted to operate as 1 a generator;- a field-magnet winding for said dynamo-electric machine, a resistor connected incircuit with said winding, a second dynamo-electric machine connected in circuit with said first machine and nor- 130 traversing said motor circuit exceeds a premally adapted to operate as a motor, a relay responsive to a predetermined value of current traversing the circuit for said second dynamo-electric machine for reduc-.

ing the field excitation of said first dynamoelectric machine, and a second relay adapted to increase the field excitation of said first dynamo-electric machine when said second dynamo-electric machine operates as a generator. v

2. A control system comprising a generator, means for varying and reversing the field-excitation of said generator, a motor connected incircuit with said generator, a relay. for regulating changes in the field excitation of said generator having one coil' energized in accordance with the current traversing said motor circuit and a second coil energized to assist the first coil,-a second relay having a coil energized in accordance with the current traversing said motor circuit, and a second coil wound to oppose said first coil, switching'means controlled by said first relay for decreasing the field excitation of said generator when the current determined value, and switching means controlled by said second relay for increasing the field excitation of said generator when said motor operates as a generator.

3. A control system comprising a separately'excited generator, a motor in circuit with said generator, a master switch for regulating the speed of operation of said rent traversing the motor circuit, and switching means operated by said second relay for inserting resistance in the circuit of the field-magnet winding of'said generator.

4. A control circuit comprising a separately excited generator, a 'motor connected in circuit with said generator, 'a pair of. differential relays each having .a magnetic coil energized in accordance with the excitation of said enerator and a magnetizing coil energized in accordance with the current flowing through said'motor circuit, the coils of one of said relays being-normally adapted to assist each other and the coils of the other ofsaid relays being adapted to normally oppose each other, switching means operated by said first-named relay for increasing the generator excitation, additional switching means operated by said second relay for decreasing the excitation of said generator under predetermined conditions.

5.'A control system comprising a pairoperation of the other dynamo-electric machine, a circuit in shunt relation to said limit switch, interlocks, contained in said shunt circuit and operated by said direc-. tional contactors, and manually operated means for establishing said circuit.

6. .A control system comprising a pairv of dynamo-electric machines, directional contactors for reversmg the d1rection of e citation done of said machlnes, a control circuit for said machines,a limit switch for interruptlng said control circuit during operation of the other of said dynamo-electric machines, a circuit in shunt relation'to said l1m1t swltch, an interlock in said shunt c1rcu1t operated by said directional contacmotor connected in circuit with said generator, a control circuit for said motor, a

- tors, 1 and manually. operated switching 'means for reestablishing said control circuit limit switch actuated bya predetermined operation of said motor for interrupting said control circuit, a circuit in shunt relation to-said limit switch, an interlock actuated by said directional contactors included in said shunt circuit, and manually-operated means for establlshin'g .said shunt circuit through said interlock for restablishing said control circuit, I

8. .A control system comprising a generator, directional contactors for changing the direction of excitation of said generator, a motor connected in circuit with said'generator, a control circuit for said motor, a

panel provided with lights indicating the energization of said control circuit, manually operated means for establishing or interrupting said control circuit mounte on said panel, a. limit switchadapted to interrupt said control circuit when predetermined Op- 1 eration of said motor occurs, a circuit in shunt relation to said limit switch, an interlock actuated by saiddirectional contactors included in said shunt circuit, and manually operated switching means mounted on said panel and adapted to complete said shunt circuit and to circuit. v

In testimony whereof, I have hereunto reestablish "said control Ivy FRED M. PARKS.

subscribed my name this 27th day of J anu I

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