C. D. KNIGHT. LING DEVICE FOR ELECTRIC MOTORS. APPLICATION FILED FEB. 21, 1907.

CONTROL 2 SHEETS-SHEET 1.

Patented Aug. 10,

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G. D. KNIGHT. GONTROLLING DEVICE FOR ELECTRIC MOTORS,

APPLICATION FILED PEB.21,19Q7.

Patented Aug. 10, 1909.

M'inesses:

UNITED srnrns rnrnur onnrcn.

CHARLES D. KNIGHT. 01-" SCUENJZCTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A (IORIORATIOX OF NEW YORK.

CONTROLLING DEVICEFOR ELECTRIC MOTORS.

Specification of Letters Patent.

Patented Aug. 10, 1909.

To 1/11 Whom it may concern:

Be it known that 1, CHARLES l). KNIGHT, a

citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Controlling Devices for Electric Motors, of which the following is a specification.

This invention relates to means for controlling electric motor circuits and has for its object the provision of a device whereby an electric motor may be started and brought up to running speed in areliable, safe and efficient manner.

Myinventionrelates more specifically to the starting of alternating current motors of the induction type.

[n the starting of induction motors of the slipring type it is essential that the secondary circuit be closed through the necessary resistance before'the closing of the primary circuit. it is also desirable that means he -provided for cutting the resistance out of the "secondary circuitin a convenient manner. In carrying outmy invention therefore 1 provide in connection with automatic means for cuttingthe resistance out of the secondary circuit, electrical connections whereby the primary circuit cannot be closed until the secondary circuit is closed through the entire resistance, and whereby the automatic mechanism begins to cut resistance out of the secondary-circuit as soon as'the primary circuit is closed.

ln the accompanying drawings, in which I have shown my invention embodied in two different forms, Figure 1. is a view of my'device controlling a three-phase induction motor, and Fig; 2 is a similar View of a modified i'orm of iny invention, in which contactors are used for automatically cutting out the resistance from the secondary circuit, controlling the same type of motor.

Referring to Big. 1 of the drawings, P is the primary and S is the secondary of an induction motor of the slip ring type, and 1, 2 and 3 aret-he three-phase mains from which the motor is operated. The primary circuit is closed'by means OfSOlGllOld switches 4 4: having cores 5 5, respectively, theformer for o crating the motor in one direction of rota' tion and the latter for reversing it. Connect- -.edi n series with the windings of the secondcry a e ee e ces 7 an 8 cont ed the three resistances.

,9 is operated by a solenoiddO acting upon a core 11 connected to the element Qby a rod 12. To the lower end oi'the rod is connected a dash-pot 13, the barrel of which is pivoted to the under side of arm 9 while the piston 14 is pivoted at 15. 'The arm 9 is normally down in the position shown, having a bias to this osition by virtue of its weight or by any 0t or desired agency. The'dashpot is designed to permit the arm 9 to move upward freely but operates to retard it upon its return. When t e arm 9 is down the resistances 6, 7 and 8 are short-circuited while, 5 when it is in the upper position, the resistances are all in circuit.

The two solenoid switches 4 and 4, which control the primary circuit, are identical in construction and operation and consist simply of soleno ds, each having a core carry ng three'bridging contacts 16, 17 and 18, and 16, 17 and 18, respectively. When the solenoids are energized, these contacts are raised and bridge the corresponding contacts to close the three phases of the primary circuit. Bridging contacts 18 andlS', when in their lower position, complete the circuit of the solenoid 10, and when moved up, break the same. The contacts are held in the raised position by means of latches l9 pivoted at 20 arranged to engage extensions 21 of the cores 5 5 of the solenoids to latch the same in a raised position. The latches are; held in by means of solenoids 22 which are connected in ,circuit so as to be'energized upon the closing of the main switch and act a ainst thetension of their springs 21 to hol the latches in an operative position. The circuits of solen oids land 4 are completed through contacts 23 and23', which are bridged b means of contacts 24 and 24 on the arm, w en the latter isin its raised osition. A switch 25 is arran ed to close the circuit through either one o the solenoids l 0r 4', depending upon the direction of rotation desired.

The arrangement of circuits and mode of operation is as follows: When the switch 25 is closed on the contact stud 26, current will ba k toline at main At the same the solenoid 22 is energized between the mains 1 and 3 from conductor 27 to conductor 32. The solenoid being energized, the controlling arm 9 is raised until it reaches the upper position where the circuits of the solenoids 4 and 4 are closed by the contacts 24 and 24 bridging contacts 23 and 23. In this position all of the resistances 6, 7 and 8' are in the secondary circuit. As soon as the cont-acts 23 are bridged, the solenoid 4 is energized, current passing therethrough as follows: from conductor 27 through solenoid 4, conductor 33, contacts 23 and conductor 31, back to line at main 2. The solenoid being energized, it closes the three phases of the primary circuit at contacts 16, 17 and 18. The lattercontact as it rises opens the circuit of the solenoid 1O whereupon the core 11 is released. The arm 9 thereupon drops and is retarded by the dash-pot 13. As the arm drops, the motor speeds up and when the lowest position is reached the motor is running at full speed. If the switch arm is moved on to the stud 34, the direction of ro- .tation of the motor will be reversed but the operation will be the same. .Current will then pass from switch through conductor- 35, bridge 18, conductor, 36, solenoid 10, thence back to line as before through conductor 28. 'The solenoid 4 is energized from conductor to conductor 37, contacts 23 and conductor 31, back to line at main 2. In order to stop the motor quickly as is sometimes desired, especially where the motor is used to operate a hoist or an elevator,-I provide a brake 38 controlled by solenoid 39. As soon as the primary circuit is closed, the solenoid 39 is energized and the brake withdrawn from the mot-or. Upon failure of voltage, solenoids 22 are decnergized to openthe primary circuit.

In Fig. 2 I have shown a similar arrange ment, the only difference being that instead of using a single controlling element operating to vary the secondary resistance, I provide aseries of contactors, each one of which as it operates cuts out a section of resistance.

When the switch 25 is closed the solenoid 4 is immediately energized. from main 3 ductor 42. This operates as before to close the three phases of the primary circuit, all of the resistances 6, 7 and 8 being in the meantime in the secondary circuit. In this case the circuit of the solenoid 4 is opened by the opening of switch 41 after the primary cir* cuits are closed. When the lower contact 18 closesjits circuit the solenoid 43 of the first contactor is energized as follows: from main 1 through conductor 44, bridging contact 18, conductor '45, solenoid 43, conductor 46, bridging contact 47 and back to line at main .3 through conductor 48. This solenoid "pulls up one eontactor to cut out one section tact 47.

of resistance, and at the same time closes a circuit through bridging contact 49 of solenoid 50. This solenoid in turn operat'es its contactor to cut out another section of resistance, and at the same time by means of its bridging contact 51 closes the circuit of the next succeeding solenoid and so on. When the last solenoid 52 is reached, the resistance is short-circuited and the circuits of all of the other solenoids are opened at con- The contactor of solenoid 52 is held in a raised position by latch mechanism 53, such as is described in connection with Fig. fl The arrangement shown in Fig. 2 may be used where the currents are hear and the operation will be substantially the same as that described with reference to Fig. 1. H I have shown my invention in connection with a particular form of motor, i. e., a threephase induction motor of the slip-ring type, but it should be understood that my invention is not limited to this particular applica tion except in so far as it is limited to the claims annexed hereto.

. hat I claim as new and desire to secure by Letters Patent of'the United States, is,- 1. The combination with an alternating current motor, of means for controllingthe same comprising an electromagnetic switch for varying the resistance in the secondary circuit and an electromagnetic switch arranged to be automatically energized to close the primary circuit when the resistance varying switch is moved to a predetermined position.

2. The combination with. an; alternating resistance is included.

The combination with an alternatingcurrent motor, of means for controlling the same comprising an electrically controllerl switch for closing the primary circuit, an impedance for the secondary circuit, and arary- 1ng mechanism thcrcl'or arranged to control the circuit oi said switch.

4. The combination with an alternating current motor, of means for controlling the same in opposite directions of rotation comprising electromagnetic primary circuit closlng switches one for each direction, an impedance for the secondary circuit, and elec tromagnetic means arranged to control the circuit of said switches for including said pedance in the secondary circuit.

5. The combination with an alternating current motor, of means for controlling the same comprising an electromagnetic switch for closing the primary circuit, an impedance for the secondary circuit, and ai automatswitch for the p current motor,

ically operated varying mechanism therefor arranged to control the circuit of the primary circuit-closer. I

6: The combination with an same comprising an electrically controlled for the secondarycircuit, electromagnetic varying mechanism therefor controlled by said switch, and connections whereby said varyingimechanism controls the circuit of the switch;

7. The combination with current motor, of means for same in opposite directions electromagnetic switch for an alternating controlling the comprising. an varying the resistance in the secondary circuit and electromagnetic switches, one for each direction of rotation, arranged to be automatically energized to close the primary circuit when the resistance varying switch is moved to a predetermined position. i

8. The combination with an alternating sista'nce normally excluded from the secondary circuit, electromagnetic switches one for each direction of rotation for including the resistance in said circuit and an electromagneticswitch arranged to be automatically energized to close the circuit when said resistance is excluded.

9. The combination with an. alternating current motor, of means for controlling the same comprising automatic means for closing the primary circuit, a variable impedance for the secondary circuit, a controlling element therefor having a bias toward the low-impedance position, an electromagnetic device for moving said element to a high-impedance position, and means controlled by the rimary circuit-closer for deenergizing the e cotromagnetic device to release-the controlling element.

10. The combination with an alternating current motor, of means for controlling the same comprising an electromagnetic switch for the primary circuit, a variable impedance for the secondary circuit, a controlling element therefor having a bias toward the low impedance position, vice for moving said element to a high-impedance position, and connections whereby the circuit of the primary circuit is closed when said element reaches a predetermined position.

alternating current motor, of means for controlling the rimary circuit, an impedance of means for controlling thesame in opposite directions comprising a rean electromagnetic decurrent motor, of means for 11 The combinationwith an alternating current motor, of means for controlling the same comprising an electromagnetic switch for the primary circuit, a variable impe-' dance for the secondary circuit, a controlling element therefor having a bias toward the low-impedance position, an electromagnetic device the circuit of which is controlled by said switch for moving said element .to ,a high-impedance position, and connections whereby the circuit of the primary switch is closed when said element reaches a predeter primary switch is, closed when said elementreaches the latter position.

13. The combination with an alternating current motor, of means for controlling the same in o posite directions of rotation comprising e ectrically-controlled switches for the primary circuit one for each direction, an

impedance'for the secondary circuit, electromagnetic varying means therefor controlled by either of said switches, and connections whereby said varyingmechanism controls the circuits of the switches.

14. The combinationwith an alternating controlling the same 1n opposite directions of rotation comprising electromagnetic switches one for each direction, a variable impedance for the secondary circuit, a controlling clement therefor having a bias toward a minimum impedance position, an electromagnetic device the circuit of which is controlled by eitherof said switches for moving said element to a maximum impedance position, and connections whereby the circuits of the primary-switches are closed when said element reaches'the latter position.

In witness whereof, l have hereunto set my hand this 19th day of February, 1907 CHARLES D1 KNIGHT.- Witnesses:

BENJAMIN B. HULL, HELEN ORFORD.