US1323273A - System of control - Google Patents

Description

.uonnukmEob F. G. HICKLING.

SYSTEM OF CONTROL.

APPLICATHJN FILED DEC.8. 191s. RENEWED APR. 22. 1919.

Patented Dec. 2, 1919.

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fr? 6W9 -5 ATTORNEY F. G. HICKLING.

SYSTEM OF CONTROL.

APPLICATION FILED DEM. 1915. RENEWED APR. 22. 1919.

Patented Dec. 2,1919.

2 SHEETS-SHEET 2 INVENTOR fiede/YZ/f fi/M/My R556 Fob s QQQM Q90 WITNESSES to 35.50 um s vk 'AT'TORNEY UNITED STATES PATENT OFFICE.

FREDERICK G. I-IICKLING, OF WILKINSBURG, PENNSYLVANIA, ASSIGNOR TO \VEST- INGHOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

SYSTEM OF. CONTROL.

Application filed December 8, 1915, Serial No. 65,775.

railway motors and the like that are adapted for operation from supply circuits of materially different voltages, such as 5000 and 600 volts direct-current, respectively.

One of the objects of my invention is to provide a system of the above-indicated character which shall berelatively simple and inexpensive in construction, and which shall effectively and reliably permit of the use of a plurality of direct-current motors in connection with a supply circuit of relatively high volta 'e, such as 5000 volts, which may be employed during the interurban portion of a run and in connection with a relatively low voltage, such as 600 volts, which must be used when the vehicle is operating in cities and towns.

Another object of my invention is to provide, in a system of the class under consideration, a plurality of governing switches tor the motors that are adapted to withstand high-voltage operation, another governing switch that is adapted to withstand only low-voltage operation and that is connected in series relation with certain high-voltage switches under predetermined conditions, and interlocking means for preventing the closureof a certain high-voltage switch before the closure of the low-voltage switch, whereby the impression of a relatively high voltage across the terminals of the low voltage switch is effectively prevented.

A. further object of ny invention is to provide, in systems of the type in question, a plurality of high-voltage switches and a low-voltage switch, as recited above, and interlocking means for preventing the opening of the low-voltage switch before the opening of a supply-circuit-connecting switch, whereby the low-voltage switch never breaks a high-voltage circuit.

Still another object of my invention is to provide, in connection. with a system of he ahovein .licated character, a multi-posi- Specification of Letters Patent.

Patented Dec. 2, 1919.

Renewed April 22, 1919. Serial No. 291,950.

tion master controller for controlling the various switches, neans for elfecting the opening of a supply-circuit-co1mecting switch upon relatively slight backward movement of the controller from any operative position, and means for preventing the subsequent operation of the system until the master controller is returned to its initial position.

In the accompanying drawings, Figure 1 is a diagrammatic view of the main circuits of a system of control embodying my invention; Fig. 2 and Fig. 3 are diagrammatic views of certain pieces of control apparatus that are employed in connection with the auxiliary governing system which is illustrated in Fig. 4 and which is adapted to govern the various motor-controlling switches that are shown in Fig. 1 in accordance with the one or the other of the sequence charts that are illustrated in Fig. 5 and Fig. 6, dependent upon service conditions; and Fig. 7 is a detail, diagrammatic view of a complete motor-controlling switch.

Referring to Fig. 1, the system shown comprises a plurality of supply circuits of materially different voltages having positive supply-circuit conductors marked 5000 v. T. and 600 v. T, standing for 5000- volt trolley and 600volt trolley, respectively, which may be separated from each other in any suitable manner, as by a section insulator S1; at common negative return circuit iarked Ground; a plurality of electric motors of the twin-armature type respectively comprising pairs of armatures Ala and A17), A26, and A26, A364 and A32), and Add and Ado, commutating field-magnet windings C1, C2, C3 and Cd and main field wind-- ings F1, F2, F8 and F4; a reversing switch RS, preferably of a familiar electricallycontrolled type, for reversing the electrical relations of the pairs of main field windings F1 and F2, and F3 and Fat with re spect to the corresponding armatures and commutating field windings; an accele ating resistor AR with which is suitably associated a plurality of resistor short-circuiting switches R1 to R5, inclusive; a plurality of motor-controlling switches LS1, LS2, LS3, M1, P1, P2, S1, S2, and G; a plurality of field-regulating resistors Flt-l and FR-2 for the respective pairs of motors, and a plurality of switches 1 and 3, which are associated with the resistor FBI, and 2 and t which are connected to the resistor FRQ, for varying the excitation of the corresponding field windings during 600 volt operation of the motors, as more fully set forth later; a plurality of motor changeover switches SWVl to SWV4, inclusive; an overload trip OT of a suitable high-voltage type for effecting an opening of the motor circuit under overload conditions; and a set of auxiliary circuits AC that are interposed between the motors and the negative supply-circuit conductor Ground.

The motor change-over switches SW1 to SW4 are adapted to occupy the solid-line position for 5000-volt operation, and the dotted-line position for GOO-volt operation, whereby the adjacent sets of twin armatures are disposed in series and parallel relation, respectively. The preferred switch construction is fully set forth in my copending application, Serial No. 65,776, filed Dec. 8, 1915.

The auxiliary circuits AC are shown as comprising, in general, a storage battery, marked Battery, which is adapted to be connected in parallel-circuit relation, upon th closure of a switch B, to a set of regulating counter-electromotive force cells marked C. E. M. F. cells, whereby the battery, which may be employed for energizing the actuating coils of the various switches or for any other purpose, is connected in series relation with the main-motor circuit and is adapted to be properly charged; and a motor for driving a compressor which may be employed for furnishing air to the braking system or for any other purpose, as will be understood. The auxiliary system just described forms no material part of my present invention, and is fully shown and described in a co-pending application of N. W. Storer, Serial No. 781,742, filed July 29, 1913, and assigned to the Westinghouse Electric & Manufac turing Company.

It should be observed that the switches S2, G, B and 1 t 4, inclusive, are shown as being of a single-break type and are adapted to withstand only low-voltage operation, that is to say, they are not constructed to permit of the impression of a relatively high voltage upon their terminals during either the closing or the opening of their circuits; while the remaining motorcontrolling switches are illustrated as being of the double-break type and are thus adapted to withstand high-voltage operation. Consequently, it is necessary to provide means for preventing the impression of a dangerously high voltage upon any of the lowvoltage switches, even though a low-voltage switch is connected in series relation with a number of the high-voltage switches during a certain portion of the accelerating period.

Such preventive means will be fully described in connection with the auxiliary governing system of Fig. 4.

Reference may now be had to Fig. 4 which illustrates, in addition to the actuating coils of the various motor-controllin switches and the battery for energing the coils, a plurality of electrical interlocks that are associated with, and adapted to be actuated b the various switches in accordance wit the familiar construction that is illustrated in Fig. 7 a plurality of other contact members that are associated with either the control change-over switch CCh that is illustrated in Fig. 2 or with the control cutout switch CO that is shown in Fig. 3; a master controller MC that is adapted to occupy a plurality of positions a to It, inclusive; a master reverser MB of a well-known type; actuating coils f and 1'', corresponding to forward and reverse operation of the main-circuit reversing switch RS; and a plurality of train-line conductors TL for adapting the system for multiple unit control, in accordance with familiar practice.

The control change-over switch CCh that is shown in Fig. 2 is adapted to occupy two positions, respectively marked 5000v. and GOO-v. for manipulating certain of the control circuits of Fig. 2 in accordance with the supply circuit that is employed at the time.

The control-circuit cutout switch ()0 that is illustrated in Fig. 3 is adapted to occupy four positions respectively marked All out, All in, A1 and A3 out, and A2 and A4 out, for suitably arranging the auxiliary governing circuits when certain of the motors are excluded from circuit by reason of damage thereto, as will be understood.

The master controller MO is provided with a structure of the slip-segment type, for a purpose to be hereinafter set forth. which comprises a suitable annular band 6 of insulating material that makes frictional engagement with the body of the master controller and upon which is disposed a contact member 5 that has a width corresponding to two notches of the controller. The annular band 6 is here shown as provided with a plurality of lugs or projections 7 and 8 that are disposed a distance apart that also corresponds to two notches, and a stationary pin or arm 9 is suitably associated with the frame (not shown) of the controller. The slip-segment in question forms no part of my present invention except as it performs a certain function in connection therewith. The preferred structure is fully shown and described in a co-pending application of N. WV. Storer, Serial No. 774,394, filed June 18, 1913, and assigned to the Westinghouse Electric & Manufacturing Company.

The mechanical operation of the slip-seg ment may be briefly set forth as follows: l/Vhen the master controller is actuated from its off position through its initial operative position, the annular band 6 moves with the controller until the projection 8 strikes the pin 9, and the contact member 5 engages cer tain control fingers to complete the circuits of the actuating coils of certain switches, as hereinafter more fully described, and such engagement is maintained throughout the forward operation of the master controller. However, upon a predetermined backward movement of the controller from any operative position, the annular band 6 moves with the master controller for a distance corresponcling to two notches, when the projection 7 of the band 6 strikes the pin 9 to prevent further movement of the slip-segment the engagement of the contact member 5 with the corresponding control fingers being broken at this time.

Assuming that it is desired to effect acceleration of the motors from the 5000 -volt trolley, the operation of the system may be set forth as follows: Upon movement of the master controller to its initial operative position a, a circuit is first established from the positive terminal 13-}- of the battery, through conductor 10, control fingers a, and 10?), which are bridged by contact segment 11, conductor 12, which is connected to a control finger 13, that is employed on other circuits to be described, conductor 14, trainline conductor 15 and conductor 16 to a common positively-energized conductor 17, whence one circuit is continued through conductor 18, cooperating contact members 19 of the overload trip OT in its lower position, conductor 20, interlock R2out, conductor 21 and a plurality of parallel-coimected circuits, respectively comprising actuating coils of the switches LS1, LS2 and LS3 and the actuating coil of the switch M1, together with a contact member 21aCOAll in, or A2 and A4: out, whence circuit is completed through a common conductor 22, contact member 23 of the main-circuit reversingswitch BS in its forward position, conductor 24:, train-line conductor 25, conductor 26, contact segment 27 of the master reversing switch MB in its forward position, conductor 28, control fingers 29 and 30, which are bridged by the contact member 5 of the slipesegmcnt, and conductors 32 and 33 to the negative terminal B- of the battery.

Upon the closure of the switch LS1, a

V holding interlock LS1-in bridges the abovementioned interlock R2-out, thereby maintaining the supply circuit connecting switches closed during the remaining for ward ope *ation of the master controller.

' A further circuit is established at this time from contact segment 341 of the master controller which engages the control finger 13,

through control finger 35, conductor 36, train-line conductor 37, conductor 38, the actuating coil of the switch R1 and conductors 39, 40 and ll, train line conductors 42, and conductor 4-3 to the negative conduc tor 33.

Still another circuit is established in the first position of the master controller from the positively energized conductor 10, tl rough conductor 16, train-line conductor 4C7 conductor 48, contact member l9- CC7L0O0O v., contact member -00-- All in, interlocks P1out and P2out, the actuating coil of the switch S2, conductor 51 and interlock LS1-in, to the negative conductor 40. At this time, the several motors are connected in series-circuit relation, but the circuit is open at the higlrvoltage switch S1. As soon as the low-voltage switch S2 is closed, so that no voltage of a relatively high value can be impressed across its terminals, a circuit is completed from the abovementioned interlock P2out, through conductor 52, interlock S2in, the actuating coil of the switch S1, conductors 53 and 54:, auxiliary contact members 55 of the over load trip OT, and conductor 56 to the negatively-energized conductor 22.

The switch B of the auxiliary circuits AC is also closed by the completion of a circuit from interlock 50CO All in, through conductor 5'7, the actuating coil of the switch B, interlock LS2--in and conductor 58, which is connected to the negative conductor 4L0.

To efi'ect further acceleration of the motors, the master controller may be moved to its second position b, whereupon the contact segment 34 engages control finger 59, whence circuit is completed through conductor 60, train-line conductor 61, conductor 62, contact member 63CCh-5000 v., the actuating coil of the switch R2 and corn ductor 6a to the negative conductor 40, thereby shortrircuiting a predetermined portion of the accelerating resistor AR.

In position 0, a circuit is established from the contact segment 3d of the master controller, through control finger 65, conductor 66, train-line conductor 67, conductor 68, the actuating coil of the switch R3, and the conductor 69 to the negative conductor 40. The switch R1 is opened by reason of the disengagement of control finger 35 and contact segment 34.

In position (Z, control finger 72 engages contact segment 34, whence circuit is completed through conductor 71, train-line conductor 72, conductor 73, the actuating coil of the switch R4 and conductor 7 4 to the negative conductor 40.

Upon actuation of the master controller to its position 0, the contact segment 3 engages control finger 75, from which point circuit. is completed through conductor 76,

train-line conductor 77, conductor 78, the actuating coil of the switch R5 and-conductor 79 to the negative conductor i(). The switch Rt is open at tuibstantially the same time.

In position f, the switches R1 and Rat are again closed, whereby the entire accelerating resistor AB is short-circuited and the motors are connected in full-series relation.

To ettlect shunting transition of the pairs oi. motors, the master controller is actuated toward its initial parallel position whereupon the resistor-short-circuiting switches R1, R4 and R5 are first opened, and the switch P2 is closed by reason of the com pletion of a circuit from contact segment 34 through control finger 80, conductor 81, train-line conductor 82, conductors 83, 8st, 85 and 86, contact member 87-CO All-in, or A2 and A 1 out, the actuating coil of the switch. P2, and conductor 88 to conductor 3L1, which is connected to the negative battery termihial, as already traced.

Inasmuch as the switches S1, S2 and P2 are thus simultaneously closed, the pairs of armatures AZaand A2?) and A la and A47) are connected in a temporary closed circuit. Upon the closure of the switch P2, however, the switches S1 and S2 are quickly opened by reason of the exclusion from their governing circuit of the interlock P2out.

A control circuit is next established from the conductor 84, through conductor 8!), contact member 90CO'All in, or A1 and A3 out, conductors 91 and'92, interlock S2- out, the actuating coil of the switch G, conductor 93, and interlock LS2-in to the negative conductor 40.

The transition of the motors thus completed, with the exception of the closure of the high-voltage switch P1, which is eifeeted as soon as the low-voltage switch G is closed,

by reason of the establishment of a circuit from conductor 91, through conductor 9-1, interlock G-in, the actuating coil of the switch P1, interlock S1out and conductor 5st, which is connected to the negative side of the battery circuit.

It should be noted that, in the case just recited, the low-voltage switch G is eon nected in series relation with the l1iglivoltage switches P1, LS1, LS2, and LS3, but the switch G is closed before the switch P1 can possibly close, thus preventing the impression of an unsuitably high voltage across the terminals of the low-voltage switch G.

Upon the closure of the switch P1. the conductors 16 and 8. are connected by a circuit comprising conductor 95, interlock P1.in and conductor 96. However, the completion ot this circuit efiects no changes in the control system at the present time, but is employed to prevent the low-voltage switch G from opening the liigl1\'oltage c'. cuit when the conductor 88 is dciineu zed upon backward movcmen t of the master con- 1':-roller from position g. Thus, the switch (i cannot open until the high-voltage switch LS2 has opened, as hereinafter fully expl a ined.

To efi'ect'further acceleration of the parallel-connected pairs of motors, the master controller may be moved successively through its positions It to 7i, inclusive, whereupon the switch 1H closed, the switch R5 is closed, and the switch R4: is opened, the switch R1 is closed, and the switch R4- is closed, by the engagement of the contact segment 31 of the master controller with the corresponding control fingers, whereby the accelerating resistor AB is suitably excluded from circuit, and the motors are finally disposed in full-parallel relation.

Assuming that the master controller is actuated backwardly from its final operative position 2'1 the governing circuits of the switches R4 and R1 are open, thus disposing a certain portion of the resistor Ali in circuit. When the master controller has been moved back beyond its position 2', however, contact segment 5 becomes disengaged from the control fingers 29 and 30 by reason of the mechanical engagement of the projection 7 ot the annular band (i and the pin 9, as hereinbetore explained, and, consei' uently, the actuating circuits of the line switches LS1, LS2 and LS3, as well as the actuating circuits of the other high-voltage switches, are interrupted. In this way, prior to the opening of the motor circuit by the line switches, a certain amount of resistance is included in circuit with the motors for reducing the voltage of the current supplied thereto as fully set forth in a co-pending application of K. A. Simmon, Serial No. 54,310, filed October 6. 1015, patented Nov. 12, 1918, So. 1,284,798 and assigned to the W estinghouse Electric & Manufacturing Company, to ,vhich reference may be made for any further description. However, it should be observed that. by reason of the inclusion of the interlocks LSlin and LS2in in the energizing eir cuits of the actuating coils of the switches S2 and G, respectively, these low-voltage switches are prevented from opening until after the high-voltage line switches have opened.

It will thus be seen that I have provided a motor-controlling system that is adapted to employ a plurality of supply circuits of materially different voltages, a plurality of switches that are adapted to open and close relatively high-voltage circuits, and a pair of switches that are adapted to Withstand only low-voltage operation and which are respectively connected in series relation with a plurality of high-voltage switches during series acceleration and parallel acceleration of the motors. However, by the provision of the interlocking means already described, I absolutely prevent the closure of one of the series-related high-voltage switches before the closure of the corresponding low-voltage switch, and I also prevent the opening of the high-voltage circuit by a low-voltage switch.

huioreover, when the line switches have been opened. by the backward movement of the master cont-roller, as already described. or by the actuation of the overload trip OT to its open position, whereby the energizing circuits of the line-switch actuating coils are deenergized, in accordance with familiar practice the system cannot be further operated-until the master controller has been returned to its initial operative position a to allow the disengagement of control finger 59 and contact segment 34, thus effecting the opening of the switch R2, whereupon the energizing circuit of the line-switch actuating coils may be completed from conductor 20 through interlock R2out and conductor 21, as already set forth.

Assuming that the electric railway vehicle is running through a city or other thickly populated district where the use of a relatively low operating voltage is necessary, so

that the motor-control system is energized from the low-voltage trolley, 600 v. T, the control change-over switch {10b is first actuated to its position marked 600 v., and the motorchange-over switches SlVl to SlVL are moved to the dotted line positions, whereupon the master controller MC may be actuated to its initial operative position a and the following circuits are established: switches LS1, LS2, LS3 and M1 are closed by the completion of a circuit from conductor 20, through interlock 1out, contact mem ber 31CC7L6OO v., conductor 21, and thence, as already traced in connection with 5000-volt operation, the switch R1 is closed, as hereinloefore set forth and in addi tion, a circuit is completed from the positive supply-circuit conductor 17, through conductor 97, contact member 98CC7L600 v., the actuating coil of the switch R 1 and conductor 74 to the negative conductor40.

Another circuit is simultaneously established from contact member 98, through con ductor 99, contact member 100CC7z-600 v., the actuating coil of switch R2 and conductor 64 to the negative conductor 40.

Another circuit is completed from the positive conductor 16, through conductor 101, contact member 102 CCh-600 v., 0011-.

ductors 103 and 85, and thence through the actuating coil ofthe switch P2 as previouslydescribed. The actuating coils of the switches G and P1 are also energized in that order from the conductor 89, which is connected to conductor 103, in accordancewith the circuits already traced in connection with 5000-volt operation.

Inasmuch as the switches R1, R2 and El are all closed, the accelerating resistor AB is completely short-circuite ;l and the closure of the switches P1, P2 and G disposes the pairs of motors in parallel relation. Thus, the initial circuit connection of the motors to the GOO-volt supply circuit corresponds to full-parallel relation.

If the master controller is moved to its position b, a circuit is established from conductor 62, which is connected to control finger 59, through contact member 1O4CC72 600 v. and the parallel-connected actuating coils of the switches 1 and 2 to the negative conductor 40.

In position 0, which is the final position that is employed during GOO-volt operation, a circuit is established from conductor 68, which is connected to control finger 65, through contact member 105CG7L600 v. and the parallel-connected actuating coils of the switches 3 and 4 to the negative conductor 40.

It will be observed that further acceleration of the motors after connection to the GOO-volt trolley is accomplished by the use of a field-control scheme. The closure of the switches 1 and 2 serves to connect the resistors Fill and PR2 in parallel relation to the circuits. comprising the field windings C1, C2, F1 and F2, and C3, C4, F3 and. F4, respectively, the resistance value of the resistors FRl and FRQ being selected to effect the impression of a voltage upon the field-winding circuits that is lower by a predetermined amount than the voltage originally impressed upon the field-winding circuits. The subsequr t closure of the switches 3 and 4- serves to short-circuit portions of the resistors FR-l and FR2, respectively, whereby the voltage of each fieldwinding circuit is correspondingly and materially reduced, and a further increase of operating speed is effected, in accordance with familiar principles.

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

I claim as my invention:

1. In a system of control, the combination with a plurality of supply-circuits of a relatively high and a. relatively low voltage, respectively, of an electric motor, a plurality of governing switches therefor adapted for ircuitclosing and open ng under either voltage condition, plurality of other gov; crning switches adapted for circuit-closing and opening only under low-voltage condition, and means for insuring theclosure of a low-voltage switch before the closure of a certain high-voltage switch.

2. In a system of control, the combination with a plurality of supply-circuits of a relatively high and a relatively low voltage, respectively, of an electric motor, a plurality of governing switches therefor adapted to withstand high-voltage operation, a overning switch adapted to withstand on y lowvoltage operation, and means for preventing the closure of a certain high-voltage switc before the closure of said low-voltage switch.

3. In a system of control, the combination with a plurality of supply circuits of a rela tively high and a relatively low voltage, respectively, of an electric motor, a plurality of governing switches therefor adapted to withstand high-voltage operation, a governing switch adapted to withstand only lowvoltage operation, means for connecting said low-voltage switch in series relation with certain of said high-voltage switches under predetermined conditions, and means for preventing the impression of unsuitably high voltages upon said low-voltage switch.

i. In a system of control, the combination with a plurality of supply-circuits of a relatively high and a relatively low voltage, respectively, of an electric motor, a plurality of governing switches therefor adapted to withstand high-voltage operation, a governing switch adapted to withstand only lowvoltage operation, means for connecting said low-voltage switch in series relation with certain of said high-voltage switches during a predetermined portion of the accelerating period, and means for insuring the closure of said low-voltage switch before the closure of all the series-related high-voltage switches.

5. In a system of control, the combination with a plurality of supply-circuits of a relatively high and a relatively low voltage, re-

spectively, of an electric motor, a plurality of governing switches therefor adapted to withstand high-voltage operation, a goving switch adapted to withstand only lowvoltage operation, means for connecting said low-voltage switch in series relation with certain of said hi gh-voltage switches during a predetermined portion of the accelerating period, and means dependent upon the prior closure of said low-voltage switch for per- 3 mitting the closure of a certain high-voltage switch.

6. In a system of control, the combination with a plurality of supply circuits of a relatively high and a relatively low voltage, respectively, of a plurality of electric motors, a plurality of governing switches therefor adapted to withstand high-voltage operation, a pair of governing switches adapted to withstand only low-voltage operation, means for connecting one of said 10 voltage switches in series relation with certain of said high-voltage switches during series acceleration of the motors, means for connecting the other low-voltage switch in series relation with certain of said highvoltage'switches during parallel acceleration of the motors, and plural means for insuring the closure of the one or the other low-voltage switch before the closure of all the corresponding seriesrelated switches.

7. In a system of control, the combination with a plurality of sup ly circuits of a relatively high and a relatively low voltage, respectively, of a plurality of electric motors, a plurality of governing switches therefor adapted to withstand high-voltage operation, a pair of governing switches adapted to withstand only low-voltage operation, means for connecting one of said low-voltage switches in series relation with certain of said high-voltage switches durin acceleration of the motors, means or connecting the other low-voltage switch in series relation with certain of said high-voltage switches during parallel acceleration of the motors, and interlocking means associated with the respective low-voltage switches for preventing the closure of certain corresponding seriesrelated high-voltage Switches before the closure of the one or the other lowvoltage switch.

8. In a system of control, the combination with a plurality of sup ly-circuits of a relatively high and a relatively low voltage, re spectively, of an electric motor, a plurality of governing switches therefor adapted to withstand high-voltage operation, a govern ing switch adapted to withstand only lowvoltage operation, and means for preventing the opening of said low-voltage switch before the opening of a certain high-voltage switch.

9. In a system of control, the combination with a plurality of supply-circuits of a relatively high and a relatively low voltage, respectively, of an electric motor, a plurality of governing switches therefor adapted to withstand high-voltage operation, a governing switch adapted to withstand only lowvoltage operation, means for connecting said low-voltage switch in series relation with certain of said high-voltage switches under predetermined conditions, and means for insuring the opening of a certain high-voltage switch before the opening of said low-volt age switch.

10. In a system of control, the combination with a plurality of supply-circuits of a relatively high and a relatively low voltage, respectively, of an electric motor, a plurality of governing switches therefor adapted to withstand high-voltage operation, a governing switch adapted to withstand only lowvoltage operation, means for connecting said low-voltage switch in series relation with series certain of said high-voltage switches during a predetermined portion of the accelerating period, and means dependent upon the prior pening of a certain series-related highvoltage switch for permitting the opening of said low-voltage switch.

11. In a system of control, the combination with a plurality of supply-circuits of a relatively high and a relatively low voltage, respectively, of an electric motor, a plurality of governing switches therefor adapted to withstand higlrvoltage operation, a governing switch adapted to withstand only lowvoltage operation, means for preventing the closure of a certain high-voltage switch before the closure of said low-voltage switch, and means for preventing the opening of said low-voltage switch before the opening of another high-voltage switch. I

12. In a system of control, the combination w'th a plurality of supply-circuits of a relatively high and a relatively low voltage, respectively, of an electric motor, a plurality of governing switches therefor adapted to withstand hi glrvoltage operation, a governing switch adapted to withstand only lowvoltage operation, means for connecting said low-voltage switch in series relation with certain of said high-voltage switches under predetermined conditions, means for insuring the closure ofsaid low-voltage switch before the closure of all the seriesrelated high-voltage switches, and means for insuring the opening of at least one of said highvoltage switches before the opening of said low-voltage switch.

13. In a system of control, the combination with a plurality of supply-circuits of a relatively high and a relatively low voltage, respectively, of an electric motor, a plurality of governing switches therefor adapted to withstand high-voltage operation, a governing switch adapted to withstand only low-voltage operation, means for connecting said low-voltage switch in series relation with certain of said high-voltage switches during a predetermined portion of the accelerating period, means dependent upon the prior closure of said low-voltage switch for permitting the closure of a certain seriesrelated high-voltage switch, and means dependent upon the prior opening of another series-related high-voltage switch for permitting the opening of said low-voltage switch.

14. In a system of control, the combination with a. plurality of supply-circuits of a relatively high and a relatively low-voltage, respectively, of a plurality of electric motors, a plurality of governing switches therefor adapted to withstand high-voltage operation, a pair of governing switches adapted to withstand only low-voltage operation, means for connecting one of said low-voltage switches in series relation with certain of said high-voltage switches during series acceleration of the motors, means for con necting the other low-voltage switch in series relation with certain of said high-voltage switches during parallel acceleration of the motors, interlocking means associated with the respective low-voltage switches for preventing the closure of certain corresponding seriesre1ated high-volta e switches before the closure of the one or the other low-voltage switch, and interlocking means associated with other high-voltage switches for preventing the opening of said low-voltage switches prior to the opening of said last high-voltage switches.

15. In a system of control, the combination with an electric motor, of a plurality of electrically-operated governing switches therefor, a multi-position master controller for controlling said switches, means for effecting the simultaneous opening of certain switches upon relatively slight backward movement of said controller from any operative position, and means for preventing the subsequent closure of the switches until the controller is returned to a predetermined position.

16. In a system of control, the combination ith a supply-circuit, an electric motor, and an accelerating resistor, of a plurality of motoroverning switches, a multi-position master controller for controlling said switches, means for effecting the opening of a supply-circuit-connecting switch upon relatively slight backward movement of said controller from any operative position, and means comprising one of said resistor switches for preventing the subsequent operation of the system until the controller is returned to its initial position and the entire accelerating resistor is included in the motor circuit.

17. In a system of control, the combination with a supply circuit, an electric motor, and an accelerating resistor, of a plurality of resistor-short-circuiting switches, a plurality of other motor-governing switches, a multi-position master controller for controlling said switches, interlocking means for closing the actuating circuit of a supplycircuit-connecting switch when all of said resist-onshort-circuiting switches are open, means for efi'ecting the opening of said sup ply-circuit-connecting switch upon rela tively slight backward movement of said controller from any operative position, and means for preventing the subsequent operation of the system until the controller is returned to its initial position to energize said actuating circuit through said interlocking means.

18. In a system of control, the combination with an electric motor, a plurality of switches for overning the operation of the motor, and a controller for governing the operation of said switches, of means for effecting the opening of certain switches upon turned to a predetermined position.

relatively slight backward movement of said In testimony whereof, I have hereunto 10 controller from any operative position, and subscribed my name this 30th day of means comprising an auxiliary switch for Nov. 1915.

preventing the subsequent closure of the FREDERICK G. HICKLING.

various switches until the controller is re-

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