US1682508A - Motor-control system - Google Patents

Description

Fig.1.

A L HARVEY MOTOR CONTRQ L SYSTEM Filed Sept. 12. 1922 m le w n Aug.28,1928.

Fig.2.

-OOOOO OGO O O O OOOOOO OOOOO OOO O00 000 OO O AlbeM L. Harvey.

A'TTORNEY Patented Au 28, 192a UNITED STATES ALBERT L. mvnr, or wrrxmsnune,

HOUSE nnncrmc a mmmcrome VANIA.

PATENT oar-ice.

PENNSYLVANIA, ASSIGNOR TO. WES TING- COMPANY, A COBPOBATIGN OF PENNSYL- HOTOB-OONTROL SYSTEM.

Application filed September tor at predetermined selective speeds in accordance with the varying service requirements.

I preferably employ a controller of the cam-operated type, similar to that illustrated in the patent to H. D. James, No.1,362,003, assigned to the Westinghouse Electric & Mfg. Company. The controller referred to, however, is manually operated, whereas I provide electro-responsive means for actuating the controller. In my system, a number of selective switches provide means for predetermining the running speed of the main motor, and a time-element relay is so connected as to permit the initial operation of the main motor for any desired period at greatly reduced torque, prior to the starting up of the speedcontrolling means. A low-voltage relay is also provided with a time-limiting device, whereby the motor-starting resistors are reconnected into circuit in case low voltage obtains for such a period as to cause an undesirable reduction in the motor speed. This arrangement protects the motor against over- 7 load upon the sudden return of normal line voltage.

A centrifugally operated switch is providedto disconnect the motor from the line should the speed thereof fall below a desired value.

My invention will be described with reference to the accompanying drawing, in which Fig. 1 is a diagrammatic repraentation of circuits and apparatus embodying my invention, and I Fig. 2 is a table or chart indicating-the sequence of operation of the ma; controller switches. V 4

. Referring to Fig. 1, a three-phase induction motor 1 is connected, b means of a remotelycontrolled circuit-brea er 2, to line conductors -3, 4 and 5. The circuit-breaker 2 is pro- I vided with a closing coil 6 and an opening coil 7 which are respectively controlled by a start button 8 and a stop button 9. I have illus- I trated a centrifugal pump 10 directly con 12, 1922. Serial H0. 587,655.

nectedto the driving motor 1, and, on the same operating shaft 11, is mounted a. speedgoverning switch .12.

Accelerating resistors 13 are connected, in the customary manner,' to the secondary winding of the motor 1. A cam-operated controller 14 having a number of operative positions a to j, inclusive, is provided with a plurality of switches 15 to 26, inclusive, for controlling the resistors 13. The controller 14 is alsoprovided with a plurality of auxiliary I switches 27, 28, 29 and 30, which co-operate with selector switches 31, 32 and 33. Addi-. tional auxiliary switches 34, 35 and 38 are ac-' tuated by the controller 14, as will be described later. The controller 14 is operated by means of a pilot motor 37 having an armature 38, and a field-magnetwinding 39.

A relay 40 controls the operating circuit of the motor 37 A time-element relay 41 is arranged to be opened, by means of the start button 8, to prevent the initial operation of the motor 37, for a purpose to be hereinafter set forth. A low-voltage relay 42 is provided with an operatin coil 43- that is normally ener ized throng the circuit-breaker 2.. This re ay is, therefore, normally its upper position and, in case of low vo slowly returns to its lower or illustrated position. A control relay 45 is operated by means of the start button 8 for closing the circuits of the circuit-breaker 2 and the relay 41. 'As a matter of convenience, an auxiliary circuit, including conductors 4.6 anl 47, is provided for the operating coils of certain of the control switches. v

Assuming the apparatus and various switching devices in their illustrated positions, the system is operated by momentarily pressing the start button 8, thereby closlng relay 45, the operating coil 48. of the relay being connected to conductors 46 and 47 through switch 35 of the controller 14. The closure of relay 45 completes a. circuit forthe in tage, it.

closing coil 6 of the circuit-breaker 2. This vlay 42 icks up and sister sections 13 is open. The low-voltage remaintains its upper position uring normal operation.

. As is well understood, an induction motor operating with a single-phase secondary con-- nection delivers a torque of comparatively low value. The resistor sections 13 are of suitable value to insure gradual starting, which is best adapted to the bperation of a centrifugal ump. The relay 41, initially picked up by means of the start button 8, is released when the start button is released and slowly returns to its lower or illustrated position, whereby a circuit is established for the operating coil 49 of the relay 40. It maybe assumed that selector switch 33 occupies its lower closed position, completing the circuit extending from conductor 46, t roughconductor 50, relay 41, coil 49, switches 27 and 33 v and relay 42, to conductor 47.

The relay 40 closes to'connect the pilot motor 37 to line conductors 46 and 47. The operation of the motor 37 effects the succes- I slve closing of switches 15 to 26, inclusive.

Switch 15 completes the connection of the secondary-resistor circuit of the motor 1, andthe switches 16 to 26, inclusive, gradually shunt the resistors 13, after which t e motor 1 operates at full speed, and the pump 10 delivers its maximum output.

The motor 1 maybe stopped by momentarily pressing the stop button 9, thereby energizing the opening coil 7 of the circuitbreaker 2. When it is desired to reduce the out ut of thapum 10, it may be accomplis ed by means 0 certain of the selector switches, as, for example, by the closure of switch 32 in its lower position and the closure of switch 33 in its u per position. The pilot motor 37 is starte y the closure of relay 40, as previously described, and continues to operate until the opening of relay 40 by means of switch'28 is efiected in osition of controller14, in which posltion switc es 21 and 22 are closed to shunt a major portion of the starting resistors 13.

Similarly, a still lower 0 crating speed is I obtained with selector switc es 32 and 33 in their upper positions and switch 31 in its lower pos1tion. The pilot motor 37, in this case, operatesv until switch 29 is opened in position f of controller 14, in which position switches 19 and 20 are closed, and the succeeding resistor switches remain open, there'- by leaving additional sections of the resistors 13 in circuit with the motor 1.

The minimum selective speed of motor 1 is obtained when selector swltches 31, 32 and 33 occupy their upper closed positions, in which case, the pilot motor operates controller 14 until it occupies position d, in which position, switch 30 1s opened to interrupt the pilot-motor circuit. In this position,- the secondary switches 17 and 18 are closed, the subsequent switches remaining open.

"ing to position e of contro acceleratin aeaaaoe Upon the occurrence of low voltage for lower illustrated osltion. It will be noted that switch 36 is c osed in any of the operating positions a to j, inclusive- The'pilot motor 37 is now started by the closure of relay 40 and continues its operation until controller 14 occupies the off position. The circuit for the operating coil 49 of the relay 40, in this latter instance, extends from conductor 46 through conductor 50, relay 41, coil 49, switch 36 and relay 42, to conductor 47 When. controller 14 attains the 011 position, switch 36 is again opened, thereupon-de-energizing coil 49, opening the relay 40. and stopping the pilot motor 37. Following the operationjust described the-main motor 1 continues to operate at reduced speed. With controller 14 now in its initial starting position, upon a sudden restoration of of the motor 1 falls be ow a predetermined normal volt age the motor or other equipment cannot the low-voltage period, if the speed i desirable value, the switch 12, which is open J during normal operation of the motor, closes to complete a circuit for the o enin coil 7 v of the circuit-breaker 2, exten mg rou h the switch 34. This operation efiects t e opening of the circuit-breaker 2, causing an interruption of the main operating circuit and restoring controller 14 to its initial position. It may be noted that switch 34 is o 11 during a portion of the startin period, w on the speed switch 12 is closed. fter the main motor is'up to the propers eed, corresponder 14, the switch 34 closes to render the switch 12 efl'ecti've.

I have described a system for accelerating and controlling the speed of an induction motor. Any other suitable motor may be likewise controlled, and it is believed that 'm system of control will lend itself to ,a

plications other-than that which I have escribed.

Various changes in detail and arrangement may be made without departing from. .the spirit and scope of the invention, as defined in the accompanying claims. a I claim as-my invention: 1. The combination with an alternatingcurrent motor and a normally open circuited resistor therefor of means for automatica 1y connecting and excluding the resistor in successive steps, and a relay for delaying the initial operation of said means for agy desired perio 2. he combination with an alternatingcurrent motor and an --accelerating resistor of selector switches r therefor, of means for automatically renderto cause said resistor to be re-inserted,

3. The combination with an alternating current motor and-an accelerating resistor therefor, of means for automaticallycontrolling a portion of the motor winding, a relay for initially delaying the operation of said means for any desired period, and a plurality for predetermining the motor speed. i, V

4. The combination with an alternating current motor and an accelerating resistor therefor, of means for automatically excluding the resistor in successive steps, a relay for rendering one ph'ase-windin ineffective for any desired period, a time-e ement low-volt-. age relay effective to cause said winding to be 1 re-inserted, and a plurality of selectorswitches for predeterminin the motor speed.

5. The combination wit an alternatingsaid means for any desired cried, for controllin 'and a time-limit low-voltage relay e ective current motor and remotely controlled starting means therefor, of an accelerating resistor, means for automatically shunting said resistor in successive steps, selective means the shunting means, means for delaying t e functioning of said shunting means, speed-responsive means, for controlling said starting means and remotely controlled means for rendering said speed-responsive means ineflective durin starting.

6. The combination with a main motor and remotely controlled starting means therefor of an accelerating resistor, a motor-operated controller forprogressively shunting the re- 'sistor; selective means for arresting the operation of said controller to limit the main motor speed, a time-relay for controlling said controller, speed responsive means for controlling the startin means, and a switch for rendering the spee responsive means ineffective when starting the main motor.

In testimony whereof, I have hereunto subscribed my name this 19th day of- August,

- ALBERT L. a

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