US1293929A - System of control. - Google Patents

Description

L. G. RILEY.

SYSTEM OF CONTROL.

APPLICATION FILED APR. 2a. 1915.

1,293,929. Patented Feb. 11,1919.

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LYNN G. RILEY, OF WILKINSBUBG, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC. AND MANUFACTURING COMPANY, A CORPORATION OF SYLVAN IA.

SYSTEM OF CONTROL.

Specification of Letters Patent.

Patented Feb. 11, 1919.

Application filed April 23, 1915. Serial No. 233%15.

To all whom it may concern:

Be it known that I, LYNN G. RILEY, a citizen of the United States, and a-resident of Wilkinsburg, in the'county of Allegheny and State of Pennsylvania, have invented a new and usefullmprovement in Systems of Control, of which the following is a specification.

My invention relates to systems of control, and it has'special reference to the automatic-series-parallel control of electric railway vehicle motors and the like.

One of the objects of my invention is to provide a relatively simple and reliable syscharacter for preventing undesirable rushes of current and too sudden acceleration of a vehicle during a predetermined portion of its accelerating period.

Another object of my invention is to provide a simple auxiliary means for use in connection with a line relay device for permitting the operation of certain switches to set up dynamic braking of vehicle motors upon an interruption of supply-circuit volta e.

l tnotherobject of my invention is to provide an improved type of bridging transition from series to parallel relation of the motors, whereby the acceleration during such transition may be effected more rapidly and smoothly than heretofore.

In the prior art, when employing the field-control vehicle motors, it has been customary to simultaneously exclude predetermined portions of the field windings of the respective motors from circuit, thereby causing undesirable rushes of current and too sudden acceleration' of the vehicle. I'- provide automatic means for effecting the change from full to normal field strength of the respective motors successively, thus preventing the undesirable conditions referred to. Moreover, when the supply-circuit voltage has temporarily failed so that the line relay switch has dropped to open the customary circuits, it has been impossible to actuate the motor-controlling switches to set up dynamic braking and retard the movement of the vehicle. My present system provides simple meansto be actuated by the train operator to allow the action of such sistors R1 and R2 and type of system for electric switches in an emergency, whereby the vehicle speed may be controlled, as more fully set forth hereinafter.

In the accompanying drawing, Figure 1 is a diagrammatic view of the main circuits of a system of control embodying my invention; Fig. 2 is a diagrammatic view of the auxiliary governing circuits for the system shown in Fig. 1; Fig.3 is a sequence chart of well known form for indicating the sequence of operation of the various switching devices that are illustrated in Fig. 1; and Fig. 4: is a complete diagrammatic view of one of the switching devices.

Referring to Fig. l of the drawing, the system here shown comprises a pair of suitable supply-circuit conductors respectively marked Trolley and Ground; a plurality of electric motors respectively having armatures A1 and A2 and subdivided field windings F1 and F 2, to permit of field control of the motors; a reversing switch RS, preferably ofthe familiar electrically-colitrolled drum type, for simultaneously reversing the electrical relations of the respective armatures and field windings; a

plurality of motor-controlling switches LS1,

LS2, M2, JR, J, and G of a familiar electrically-controlled type; a mechanically-actuated switching apparatus PK, preferably of the drum type, that is employed in connection with a plurality of accelerating realso for varying the active amounts of thefield windings during acceleration; and another accelerating resistor AR that is adapted to be short-circuited' by the closure of the switches LS1 and LS2. The system is also provided with a limit switch L that is connected in circuit in a manner to be described, and an overload trip switch OT of a familiar type.

' The apparatus PK is adapted to assume a plurality of operative positions 1 to 7, inclusive, and comprises a plurality of alined control drums Dland D2 that are respectively provided with. operating shafts 1 and 2 upon which is mounted a centrally located pinion 3 that is adapted to mesh with a suitable rack member 4. A plurality of suitable pistons 5 and 6 are respectively secured to the ends of the rack member 4 and are disposed to operate within suitable cylinders 7 and 8, respectively. A suitable valve mem'ber'9- is adapted, when actuated,'to admit fluid-pressure from any suitable source (not shown) to the cylinder 7, and a second. valve member 10 is normally adapted to admit fluid pressure to the cylinder 8. The valve members 9 and 10 are also adapted to be electrically controlled, through the agency of suitable coils 11 and 12, respectively, that are connected in the auxiliary system shown in Fig. 2, as hereinafter set forth.

The operation of the apparatus PK may be described as follows: In the position shown in the drawing, with both the magnet coils 11 and 12 denergized, fluid pressure is admitted through the valve member 10 to the cylinder 8 to drums D1 and D2 to the position shown in the drawing, which corresponds to the OE position of the master controller that is illustrated in Fig. 2. To effect movement of the drums D1 and-D2 the magnet coils 11 and 12 are energized, whereuponfluid pressure is admitted through the valvemember 9 to the cylinder 7 and is exhausted from the cylinder 8 through the valve member 10,

thereby rotating the control drums through their successive operative positions. The general arrangement of parts, including the size of the valve openings and the customarily-provided drum star wheel device (not shown), is such. that the apparatus PK is adapted to stop only in its definite positions, 1 to 7, inclusive, as will be understood. To arrest the movement of the drums in any position, it is merely necessary to denergize the magnet coil 12, whereupon the valve opens to admit fluid pressure to the cylinder 8 and to balance the pressure in the cylinder 7, thereby maintaining the control drums D1 and D2 in the desired position until the magnet coil' 12 is again energized. Where the magnet coil 12 is intermittently energized through the agency of the limit switch L in accordance with the value of the accelerating current, as set forth later, the control drums are given a step-by-step movement to gradually exclude from circuit the accelerating resistors R1 and R2 and to subsequently vary the active amounts of the field windings F1 and F2. To return the control drums D1 and D2 to the first position shown in the drawing, it is merely necessary to denergize both magnet coils 11 and 12, whereupon fluid pressure is admitted to the cylinder 8 and is exhausted from the cylinder 7;

The limit switch L is provided with the customary series coil 13 that is here connect ed in series circuit with the armature A2 and is also provided with an auxiliary shuntconnected, difl'erentially-wound coil 14 that is energized in the manner to be described in connection with the system shown in Fig; 2. The usual auxiliary contact members 15 for opening and closing circuits of and without regard to bias the piston 6 and the;

contact segment of the switches M2 the auxiliary governing system are also as-. sociated withthe limit switch. v The general operation of the system, so far as the main circuits of Fig. 1 are concerned the particular auxil iary governing systemthat is illustrated in Fig. 2, may be set forth as follows. Energy is first supplied from the trolley conductor, through the switch LS1, the accelerating resistor AR, the armature A1, suitable contact members of the reversing switch RS, the full field winding F1, control fingers 16 and 17 that are bridged by. contact segment 18 of the control drum D1, other contact members of the reversing switch RS, the accelerating resistor R1, the switch J R, the ac celerating resistor switch RS, the full field winding F2,'controlfingers 19 21 of the control drum D2, again through the reversing switch RS and the actuating coils 13 of the limitswitch L to the negative conductor.

As indicated by the sequence chart of Fig. 3', the switch LS2 is next closed to shortcircuit the accelerating resistor AR and the apparatus PK is then gradually moved, in the step-by-step manner scribed, to gradually short-circuit the resist ors R1 and R2: In-position 2 of the control drums, a contact segment 22 engages control fingers 23 and 24; to short-circuit one section of the resistor R1; in position 3, a contact segment 26 and 27 to exclude a sistor R2ffrom circuit; in positionv 4, control finger 28 engages contact the control drum D1 to complete the shortgircuit of the resistor R1; while, in position 7 ment 25 of the drum D2 to complete the exclusion from circuit of the resistor R2.

The transition of the motors from series to parallel relation is. then effected by the initial closure of the switch J, the quent opening of the switch JR and the concurrent return of the drumsDl and D2 to their initial position 1, and the final closure and G accompanied by the openingof the switch J, as hereinafter set forth in detail, in connection with Fig. 2. The apparatus PK is then actuated through its first five positions, in a manner similar to that already described.

When drums-D1 and position 6, control finger 32 engages contact segment 33 and control finger 16 is disengaged from contact segment 18, whereby a predetermined portion of the field winding F1 is excluded from circuit to produce further acceleration of the corresponding motor, in accordance with familiar practice. As soon as the control drums D1 and D2 occupy their final position 7, a control finger and 20 that are bridged by.

25 bridges control fingers portion ofthe resegment 29 of a control finger 30 engages contact seg-' R2, the armature A2, other contact members of the reversing subse D2 are actuated to 34 engages contact segment 35 of the drum D2, while control finger 19 breaks contact with the contact segment 21 thereof, thereby reducing the full field winding to normal field Winding connection in the other motor, in the same manner as that described I in connection with the field winding F1. It will be observed that the resistors R1 and R2 are gradually excluded from circuit in corresponding successive steps and that the active amounts of the field windings F1 and F2 are also varied successively and controllably in accordance with the value of legends employed, as more fully illustrated in Fig. 4; a master controller MC and a master reverser MB for supplyingenerg'y ward, olf and reverse to the various actuating coils from a suitable source of energy, plurality of train-line conductors TL and a line relay switch LR of a familiar type. The master controller MC is adapted-to assume a plurality of operative ositions, a, b. and 0, respectively correspon ing to initial-series, full-series, and full-parallel relation of the motors, shown being automatic, the controller may be directly thrown to its final position a, as will be understood. The master reverser MR isadapted to assume the customaryforpositions, and is provided with suitable corresponding contact members, as hereinafter described.

The line relay switch LR is shown as provided with an actuating coil 36, the respective ends of which are adapted to,be connected to the supply circuit conductors Trolley and Ground, as indicated in Fig. 2. The switch is adapted to occupy a lower position, when the coil 36 is denergized, for completing certain auxiliary circuits, and an upper position when the coil 36 is energized to complete other auxiliary circuits, as hereinafter more fully set forth.

The shunt coil 14 of the limit switch L is shown .as energized from the battery B I through the master controllers, and a contact segment 37 of the drum D2, and its energizing effect upon the limit switch op-' poses the action of the'series'coil 13 and may be varied in accordance with predetermined conditions by means ofasuitable variable resistor 38. The particular means for varyingthe resistor 38 of this control device, however, forms no essential part of my scrlbed Francis such as a battery B; a

'versing switch RS, conductor 64,

However, the system,

present invention and is fully shown and dein a co-pending application of H. Shepard,Serial No. 785, filed January 6, 1915, and assigned to the Westinghouse Electric and Mfg. Company.

Assuming the master reverser MR to be moved to its forward position and the master controller MC to be actuated to its final running position 0, the automatic operation of the auxiliary control system may be 75 describedas follows: A circuit is first established from one terminal of the battery B through conductor 40, train line conductor 41, conductor 42, control fingers 43 and 44 that are bridged by contact segment 45 of position, conductor 46, control fingers 47 and 48 that are bridged by contact segment 49 of the master controller in its positions a, b and 0, conductors 50 and 51, coiiperating contact members 51 of the overload trip OT, conductor 52, electrical. interlock 53 J- out, conductor 54, interlock M2out, the actuatingcoil of the switch JR, conductors 55 and 56, train-line conductor 57, conductor 58, control fingers 59 and 60that are bridged by contact segment 61 in the forward position of the master reverser MR, and thence to thenegative conducton,

Another circuit is simultaneously established from train-line conductor 41, through conductor 62, contact segment 63 of the recotiperating contact members 64*.of the overload trip OT in its closed position, contact seg ment 65drum1 that is adapted to complete the circuit in question when the apparatus PK occupies its initial position 1, conductor 65, actuating coil of the switch LS1,

conductor 66, coiiperating stationary and movable contact members 67 of the line relay switch LR in its upper position, and thence through conductor 56 to the negative conductor in the :manner already described.

As soon, as the switch LS1 has closed, an interlock LS1in bridges the contact segment 65drum1, thereby insuring the closure-of the switch LS1 throughout the subsequent operation of the system, irrespective of the position of the control drums D1 and D2.

Another circuit is then established from conductor 65 through conductor 68, interlock Jout and'the magnet coil 11 of the apparatus PK to the negative conductor through conductor 66 and the line relay switch contact members 67, as hereinbefore mentioned. A further circuit is established from energized contact segment 69 of the master controller MC in its positions I) andconductor 76, cooperating contact members 15 of the limit switch L, provided the limit switch has. dropped to its lower position, conductor 77, interlock 78-LS2out,' the 6 actuating coil ofthe switch'LS2, interlock LSl-in' and the negative-connected conductor 55. As soon as the switch LS2 has closed to short-circuit the accelerating resistor AR, the energizing circuit for its actuating coil istransferred through interlock 78 and conductor 7 8 to the conductor 68.

The closure of the switchLS2 causes the establishment of another control circuit from conductor 77, as soon as the limit switch L has again dropped to its lower position, through interlock 7 9-LS2-in, conductor 80, interlock Jout, and the magnet coil 12 of the apparatus PK to the negative-connect'ed conductor66. The two magnet coils 11 and 12 of the apparatus PK being thus energized, the control drums D1 and D2 will move forward in a step-by-step manner, in accordance with the position of the limit switch L, to'gradually effect the short-circuiting of the resistors R1 and R2, as hereinbefore described.

After the drums leave position 4, the contact segment 37 of drum D2 breaks the connection between conductors 72 and-73, thus denergizing the magnet coil 12 of the drums, irrespective of the position of the I limit switch L. In this way, the drums are prevented from passing beyond position 5 while the interlock 75 of the switch J R oc-' cupies its in position, or, in other words, while the motors are connected in series relation.

Assoon as the apparatus PK has reached 1 its final resistor-short-circuiting position 5, anothercircuit is established from an energizing contact segment 81 in position 0 of the master controller through control finger 82, conductors'83 and 83 contact segment 84: of the control drum D1 in any of its positions 5 to 7, inclusive, conductor 85, interlock Gout to the actuating coil of the switch J and the negative-connected conductor 55.

As soon as the switch J is closed, the switch JR is opened by reasonof the exclusion from its control circuit of the interlock 53J-out, and the magnet coil 11 of the apparatus PK is simultaneously denergized by control circuit of the corresponding interlock Jout., The magnet coil 12 being deenergized, as already pointed out, the control drums D1 and D2 are returned to their initial position 1 by reason of the concurrent de nergization of the magnet coils 11 and 12, as hereinbefore explained.

Provided the limit switch L occupies its lower position, a circuit is next established from conductor 77, through interlock 6a 79-LS2-in, conductor 86, interlock 87 The closure of the switch M2 closes a holdand R2, while the limit switch L is being position,-the switches M2 and G can be imreason of the exclusion from its naeaeae drum 1,interlock 87 -M2-out, conductor 87 interlock JR-out, the parallel-connected actuating coils of the switches M2 and G, and; conductor 55 to the negative conductor.

ing circuit therefor from conductor 87*, through interlock 87 a and conductor 87 to the conductor 52.

Whereas, in the usual type of bridging series-parallel control, the J switch is closed in accordance with the position of a limit.

switch after the various accelerating resistors havebeen completely short-circuited,

' and the initial short-circuits of the resistors are thereafter removed to render them adapt- '80 able for subsequent service in connectionwith the parallel operation of the motors, and the switches M2 and G are finally brought in to complete the initial parallel connection of the motors,-it will be observed that, in the bridging transition just described, the J switch is closed to substitute for the initial short-circuits of both resistors R1 and R2, irrespective of the limit switch L, as soon as the accelerating resistors have been initially completely short-circuited, and the control drums D1 and D2 are returnedto their initial position 1 to remove the initial short-circuits from the resistors R1 held in its upper position by the flow of current incident to the final short-circuit of the accelerating resistors. Consequently, as soon as the limit switch drops to its lower mediately closed in the manner just recited to directly dispose the motors in initial parallel relation, andthetransition of the motors from-series to parallel relation is accomplished more rapidly than heretofore and with a more continuous and uniform load upon the motors, thereby providing a smooth and more satisfactory operation of the motors during the transition period.

As soon as the switch J has been'opened, by reasonof the exclusion from its control circuit of the interlock Gout upon the closure of the switch'G, and provided the limit switch L occupies its lower position, 1 the energizlng circuit of the actuating coil below, to gradually short-circuit the accelerating resistorsRl and R2, until the posi- 126 tion 5 is reached.

The action of the drums D1 and D2 is somewhat different during parallel motor operatlon from the action during series operation, by reason of the fact that the series 130 so that the limit switch actuating cil 13 of the limit switch L is adapted to receive the current from the armature A2 only. During series operation, the same current traverses both armatures, lifts to temporarily arrest the movement of the drums whenever a section of either the resistor R1 or the resistor R2 is short-circuited. The drums move forward, therefore, one step at a time. On the other hand, during parallel motor operation, the limit switch lifts only when the current traversing the armature A2 exceeds a predetermined value. The drums thus move forward two steps'between stops, as indicated in the sequence chart, inasmuch as the current traversing the armature A1 does not influence the limit switch coil. However, the movement of the drum between stops is not too rapid to permit the active amounts of the field windings F1 and F2 to be varied. successively in drum positions 6 and 7 to thus partially reduce the rush of current, as described in connection with Fig. 1.

In order to further reduce the accelerating current during field-changing conditions, the shunt-connected switch L is rendered inoperative by reason of the contact segment 37 of the drum D2 again breaking the connection between conductors 72 and 7 3 after the-drums leave position 4. In this case, however, the magnet coil 12 of the drums is not deenergized, by reason of the interlock 75 of the switch occupying its in position, as already mentioned.

Since the actuating coils 13 and 14 of the limit switch L are adapted, when energized, to oppositely or difi'erentially influence the switch, it follows that, with the coil 14 excluded from circuit, the effect of the series coil 13 will be strengthened, or, in other words, the limit switch will lift at a relatively low value of accelerating current after the drums D1 and D2 occupy position 5, thereby further preventing undeslrable current peaks during field-changing conditions.

When the control drums D1 and D2 occupy their final operating position 7, the

two motors are disposed in full parallel relation with normal field strength in each motor.

The emergency operation of the line relay switch LR will now be described: If the supply-circuit voltage fails, or if, for any other reason, the switch LR drops to its lower position, the energizing circuits of the various actuating coils that are connected to the conductor 66 are broken at the switch by reason of the interruption of the connection between conductors 66 and 56. If it is desired to operate certain of the motor-controlling switches to effect dynamic braking of the motors under emergency conditions, an auxiliary switching device or 67 of the the negative conductor.

coil 14 of the limit push-button PB, that is preferably located near the master controller, may be actuated by the train operator, may be completed from the actuating coils of the switches to be actuated through condnctor 66, the cooperating contact members line relay switch LR in its new or lower position, conductor 88, train-line conductor 88*, conductor 89, the push-button PB in its operative position, conductor 90, control fingers 91 and 60 that are bridged by the contact segment 61 in the forward position of the master reverser, and thence to Upon the concurrent operation of the push-button PB and the master controller MC, therefore, the actuating coils of the various motor-controlling switches, that are connected to the conductors 66, may be energized and the switches may be operated to set up dynamic braking through the closed "motor circuit, with the line relay switch occupying its lower or emergency position, as will be understood. i

I do not wish to 'be restricted to the specific circuit connections or arrangement of parts herein set forth, as various modifications of my invention may be made without departing from the spirit and scope thereof. I desire, therefore, that only such limitatlons shall be imposed as are indicated in the appended clalms.

I claim as my invention:

' 1. In a system of control, the combination with a plurality of electric motors severally having armatures and field magnet windlngs, of means for connecting said motors in various circuit relations, a plurality of accelerating resistors, a control drum comprising contact means for gradually excluding said resistors from circuit and other contact means for successively varying the active portions of the field winding to effect acceleration of the motors, when the latter are connected in various circuit relations, and means actuated in accordance with the accelerating current for automatically operating said drum from its initial to its final position in a step-by-step manner.

2. In a system of control, the combination with a lurality of electric motors severally havin armatures and subdivided field-magnet w ndings, of means for connecting said motors in series and in parallel relation, a plurality of accelerating resistors, a multi-position control drum, and automatic means governed by the current flowing through the motors for operating said control drum in a forward direction to gradually, exclude the resistors from circuit when the motors are in series relation, for returning the control drum to initial position and for operating the drum again in a forward direction to successively exclude portions of said resistors and portions of whereupon a circuit saidfield windings from circuit when the motors are connected in parallel relation 3. In a system of control, the combination with an electric motor, and a plurality of controlling devices therefor, of a switching device adapted, under normal conditions, to

permit the actuation of a predetermined number of said controlling devices. and adapted, under predetermined conditions, to prevent the actuation of certain controlling devices, and auxiliary means for rendering said switching device again fully operative under other predetermined conditions.

ii. In a system of control, the combination with a supply circuit, an electric motor, and a plurality of controlling devices therefor severally provided with actuating coils, of

- a switching device adapted, in its normal posltion, to permit .energization' of certain actuating coils and adapted to assume a new position to prevent the energization of said certain coils upon an interruption of the supply-circuit voltage, and auxiliary manual -operable means adapted to thereupon permit a reenergization of said certain coils.

5. In a system of control, the combination with a supply circuit, an electric motor, and a plural ty of controlling devices. therefor severally provided with actuating coils, of

an auxiliary source of energy, a relay device adapted, while energized from said supply c1rcu1t, to complete an energizing circuit 1 from said auxiliary source for certain actuating coils and adapted to assume a new position to open the energizing circuit of said certain actuatin ruption of the supp y-circuit voltage, and auxiliary manually-operable switching means 7 for re-completing said last energizing circuits through the new position of said relay device.

' 6. In an automatic series-parallel system of control, the combination with a plurality of electric motors and 'a plurality of ac- 1 subsequent service, means dependent upon celerating resistors, ofmeans for igraduall excluding sald resistors from c1rcu1t to e feet acceleration of said motors to full series relation, a switching device adapted to be thereupon substituted for said resistor-excludlng means to adapt the resistors for predetermined conditions for thereupon directly disposing the motors in parallel relation, with said resistors in the respective motor circuits, and means for again efiecting the exclusion from circuitof said resistors to accelerate the motors to full parallel relation.

of control, the combination with a plurality of electric motors and a plurality of accelerating resistors, of a control drum adapted to be moved through successive positions in accordance with the acceleratinoperative. coils upon an inter 7 In an automatic series-parallel system' ing current to exclude said resistors from circuit to effect acceleration of said motors fecting the operation of said drum to accelerate the motors to full parallel relation.- 8. In a system'of control, the combinat on with an electric motor, of a multi-posltion controlling device adapted to efiect motor acceleration, a. switching device provided with a plurality of actuating coils and adapted, under predetermined conditions, to govern the operation of said controlling device, and means dependent upon the positionof the'controlling device for rendering one of said coilsoperative or inoperative.

9. Ina system of control, the combination with an electric motor, of a multi-position controller adapted to efiect motor acceleration, a limit switch provided with a plurality of actuating coils energized fromdifferent sources and adapted to govern said controller in accordance with accelerating current conditions, and contact means dependent upon the position of theoontroller for rendering 10. In a system of control, the combination with an electric motor, of a multi-positioncontroller adapted to effect motor acceleration, a limit switch providediwith a plurality of difierentially-energized actuating coils and adapted to govern said con-.

troller in accordance with accelerating current conditions, and contact means for rendering one of said coils inoperative in certain controller positions to thereby cause said limit switch to operate at a relatively low current value.

11. In a system of control, the combination with an electric motor having an armature and a sub-divided field magnet winding, of anaccelerating resistor, a multiposition controller adapted to gradually short-circuit said resistor and to subseone of said coils operative or,

quently vary the active amount of said field winding, an auxiliary source ofenergy, a limit switch providedwith a plurality of differentially-disposed actuating coils respectively energized from the motor current and said auxiliary source and adapted to govern the operation of said controller in accordance with accelerating current conditions, and contact means for rendering the auxiliary-source energized coil inoperative when sald resistor is short-circuited,

whereby the motor current during fieldchanging conditions ismaintained at a relatively low average value.

12. In a series-parallel system of control, the combination with a supply circuit, and a plurality of electric motors severally having armatures and subdivided field-magnet windings, of a plurality of accelerating resistors, a multi-position accelerating controller, a plurality of actuating coils therefor, an auxiliary source of energy, a limit switch provided with a pair of difieren- I 'tially-dlsposed actuating coils respectively energized from the motor current and said auxiliary source and adapted to govern the operation of said controller in accordance with accelerating current conditions, means for initially energizing the controller-actuating coils to effect the gradual short-circuit of said resistors with the motors in series relation, means including contact means ,on said controller for effecting the return of the controller to its initial position during transition of the motors toparallel relation,

means for again effecting the short-circuit of said resistors,

and means for then employing said contact means to render the auxiliarysource-energized coil of the limit switch inpredetermined portions of the field windings from circuit, whereby the motor current during field-changing conditions is maintained at 'a relatively low average value. 13. In a system of control, the combination with a supply circuit, a plurality of motors having armature and field rwindings, a plurality of resistors in the circuit of said motors and a drum controller, of means for connecting said motors in series and in parallel relation across the supply circuit, and means governed by the current flowing through the motors for effecting a continuous automatic action, including operating said controller to gradually exclude said resistors from circuit when the motorsare in series relation, effecting transition of the motors, and excluding said resistors and a portion of said field windings when the motors are in parallel relation.

In testimony whereof, I have hereunto subscribed my name this 19th day of April LYNN G. RILEY.

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