US1684267A - Motor controller - Google Patents

Description

Sept. 11, 1928.

w. s. H. HAMILTON v MOTOR CONTROLLER Filed Dec. 10, 1925 7 Sheets-Sheet l G t w m N d ow 8m mw mv mm NWI mum QN mum NN fix lnJenbQf- \X/illiar-n SH. Hamilton, y "f U a o Hi s Attorney.

Sept. 11, 1928. 1,684,267

w. s. H. HAMILTON I MOTOR CONTROLLER I Filed Dec. 10, 1925 7 Sheets-Sheet 2 Pig. 2.

Inventor- 2 William SHHamilton, M by His Attorney.

w. s. l-|. HAMILTON MOTOR CONTROLLER Sept. 11, 1928. I M 1,684,267

Filed Dec. 10, 1925 7 Sheets-Sheet 3 Fig. 3.

CONTACTORS RES CONTACTORS SEH. PAR.

l'i SER. PAR.

Inventor 1 William S.H.Hami|oon,

by His Attorney.

Sept. 11, 1928.

w. s. H. HAMILTON- MOTOR CONTROLLER Filed Dec. 10, 1925 7 Sheets-Sheet 4 Inventor; lliam H. Hamilton, by M JY;

His Attorney.

Sept. 11, 1928. 1,684,267 W. S. H. HAMILTON MOTOR CONTROLLERv Filed Dec. 10, 1925 '7 Sheets-Sheet 5 Fig.7

T I Rll-Rn E5 F6 Inventor: William S. H. Hamilton,

His Attonngy Sept. 11, 1928.

. 1,684,267 w. .s. H. HAMILTON MOTOR CONTROLLER Filed Dec. 10, 1925 4 7 Sheets-Sheet 6 Fcgn.

Inve ntdr'z William S. H. Hamilton,

H is Attorn y Sept. 11, 1928. 1,684,267

' I W. S. H. HAMILTON MOTOR CONTROLLER Filed Dec. 10, 1925 "(ShQGtS-Sheet 7 Inventor: \A/iHiam S. H. Hamilton,

- 'Hig Attorney I Patented Sept. 11, 1928.

UNITED STATES PATENT orrice.

: WILLIAM S. H. HAMILTON, OF SCHENECTADY, NEW YORK, ASSIGNOR T0 GENERAL ELECTRIC COMPANY, A CORPORATION OF YORK. u

MOTOR CONTROLLER.

Application filed December 10, 1925. Serial No. 74,576.

This invention relates to the control of electric motors, and it relates more particularly to selective control systems suitable for use on electric locomotives or the like, where a plurality of driving motors are operated in various relations such as series, serles parallel, and parallel during motoring and regenerative braking. 0

The general object 01": the inventlon is to provide an improved arrangement of control apparatus and circuits for controlling the 1nterconnection of the motors in the various operating relations, as well as the connection of the motors to a power source, and the torque and speed of the motors in each relation during both motoring and braking operation.

\Vhile not limited thereto, a control system arranged in accordance with the present invention is particularly advantageous in controlling a three-speed, heavy traction electric locomotivev By means of the present 1nvention, the several driving motors of the locomotive may be connected either'in se ries relation for operation at relatively low speeds, in series-parallel groups for operation over an intermediate speed range or in parallel group: for high speed operation, depending upon the particular range of speed at which it is desired to operate the locomotive. Furthe more, as the service conditions vary, a transition of the motors either from a lower speed combination to a higher speed combination or from a higher speed combination to a lower speed combination readily may be accomplished without in terrupting the continuity of the motor driving torque at any time. This is particularly advantageous when the electric locomotive is handling a train on a grade, Where con tinuity of the motoring effect is essential to satisfactory operation. Otherwise the slack in the train may be bunched and then pulled out with suiiicient force to break the couplers it the motoring efiect is varied sudd tinuity oi motoring operation is interrupted during transition from one speed combination to diiierent speed combination.

Briefly, in carrying this feature of the present invention into eilect in a preferred form, the interconnection of the motorsin the various relations is controlled e..ly as necessarily occurs when the'con-.

through the agency of a pair of separately operable controllers, one for selecting the speed combination and the other for regulating the torque and consequently the speed of the motors in each of the speed combinations. lVithdirect current, serieswound driving motors, the speed controller is arranged to be operated progressively through a series of positions tocontrol the resistors in the motor circuits so as to remove or insert the resistance in a series of steps to increase or decrease the motor torque and speed while op erating in each speed combination. The pair of controllers are arranged to cooperate in controlling suitable power actuated motor switches so that the particular speed combination in which the motors are to operate may be pro-selected by operation of the selective controller, and then actually established upon a predetermined operation of the other controller to regulate the operating torque and speed of the motors in each combination to proper values. In this manner, the interconnection and driving torque of the motors may be changed at will so as to either accelerate or decelerate the locomotive smoothly and gradually even under the most severe operating conditions. Regenerative braking and reversing of the motors in each speed combination are under the control of additional separately operable controllers.

Control of the torque-and speed of the motors in the series, the series-parallel, and a the parallel speed combinations (as preselected by operation of the selective controller) is accomplished by operating the speed controller through'the same series of positions. However, it is necessary for satis factory and etficient control of the locomotive that the resulting variation in the motor torque occur in substantially equal increments upon operation of the speed controller between corresponding positions with the motors connected in eaclrrelat-ion. This is accomplished in accordance with my invention by so organizing the resistor control arrangement that different amounts of, the resistance are removed or inserted in the motor circuit at the same positions or" the speed controller depending upon the particular relation in which the motors are operating. Thus the proper amount of resistance is ins rted in or removed from the motor circuit upon operation of the speed controller through the same series of positions to cause the motor torque to vary in substantially equal increments in each speed relation.

In general, a locomotive motor control ys em em ody g. my n n o has e.. 01' lowing advantageous features; I

1. The motors can be accelerated successively through the series relation, the. series'-' parallel relation, and the full parallel relation, as well as deceler'ated through the sew eral relations in reverse order without breaking the continuity of motoring torque at any time. v g V 2-. The motoring torque can be varied in substantially equal. increments-in each operatifng relation or themotors.

SJThe motors can be connected initially in either the parallel or the series-parallel relation without oassin throu h a lower i a: a COPHlEHHZLElOIl;

4. Likewise, the motor circuit can' be in corrupted in either the parallel or the seriesparallel relation without passing through a lower combination.

5; The desired operating relation of the motors May be preselected at any time with the motors either at rest, coasting, or operating in any other combination by operating the selective controller,- and the transition into the selected relation and the accceleration or decelerationof the motors in each relation is accomplished upon proper operation of the main speed controller.

A preferred form of the invention maybe carried into effect in a control system for a three-speed, six-motor, electric locomotive as illustrated in the accompanying drawings.

Fig.1 is a: simplified schematic diagram of the driving motor circuits and the main con- .trol switches therefor.

2. is a similar circuit diagramshowing thearrangement ot the controlling switch mechanism: more in" detail.

Fig. 3 is ajchart indicating the sequence in which the various switchesshown in Figs. 1 and 2 are operated to produce the various motoring. braking, and transition connections of the motors.

4; a diagram showing. the control circuits for the several electrically controlled switches indicated in Figs. 1 and 2, together Fig. 9 is a schematic diagram showing the connect ons for initiatmg parallel motoring operation .from' rest. 7

' Fig. 10 is a schematic diagram showing theconnections for series parallel motoring operation following operation in other relat n -p.

Fig. 11 is a schematic diagram showing the. connections for full series regenerative braking operation- Fig.---1 2- lSfliSCllOlHLlllC diagram showing the connections for series parallel regenerative lira-king operation.

'Fig; 13' is a schematic diagram showing regenerative Maia motor circuits and switches.

As schematically shown in Fig. 1, the arinatures A A A .A- A together with the corresponding series field windings F F F F F F of the six'locomotive driving motors are arranged to receive power from the trolley T. through the circuit interrupter CB during motoring operation and return power. thereto when the motors are over-excited by meansxof. the excitergenerator E to produce. regenerative braking operation; The current in the motor circuit during both motoring and braking operation. is regulated by the several groups of resistors R to R R to R and R to R which respectively are underthe control. oi? the switches 11 to 17, 21 to 25, and 31 to The interconnection of the driving motors in series relation for low speed operation, we-llas in series-parallel relation with three motor. in each: of two parallel? connected groups for intermediate speed operation, and

in serieaparallel relation with two motors in each oi" three parallel connected groups for high speed operation, is controlled by the line switches 1 to 10 and the cooperating series-parallel switches 41 to 58 as will be described more fully hereinafter.-

The interconnection of the driving motors in the several speed relations just described is old and wclLkn'own, and for convenience will be termed simply series relation, seriesparallel relation, and parallel rcla tionl'respectively. 1

The line switches 1 to 10, and also the resistance controlling switches 11 to 17, 21 to 25, 31 00 preferably are of the electromagnetic con'tactor type, as indicated by an circles in the drawings and shown more in detai-l in Fig. 2. The cooperatin series parallelswitches 41- to 58 may be actuated lot llil

the resistors are associated.

by cams which. are operated by means of an electrically controlled pneumatic motor. Preferably the pneumatically operated cam contactors 41 to 58 constitute an electrically controlled meumatica-ll" actuated seriesparallel switch of the form illustrated and described in Patent No. 1,267,817, issued to R. Stearns and myself, although other forms of series-parallel switching apparatus may be employed, if desired. It will be observed that the series- parallel switches 44, 46, and 52 control ashort circuitraround the resistors R R and E respectively, so as toinsert these resistors in the circuit during certain transitions. i In accordance with modern practice th field windings of the driving motors are shunted to produce maximum'speed opera tion during series, series-parallel and parallel motoring operation. For this purpose the switches 71, 72 are arranged to control the shunting resistors R and R for the field windings and F and the switches 73 and 74, 75 and 76; and 77 and 78; for the field windings F F F and respec tively. As indicated in the drawing, the several shunting resistors R R R may be of the inductive type in order to compensate for the inductance of the respective motor field windings with which The shunting switches 71 to 78 preferably areof the electromagnetic contactor type similar to the line and resistancev controlling contactors previously described.

The switches 61 to 64 indicated in the drawing as open squares establish ground connections for the motors through the resistors R R R R respectively during regenerative braking operation and the switches 65, 67, 69 and 70, also indicated as squares in the drawing, are employed in cstablishingthe regenerative braking connections. The several braking switches preferably are of the cam type and are operated by a suitable electrically controlled pneumatic engine in a manner similar to the operation of the pneumatic cam operated series-parallel switch previously mentioned.

Fig. 2 shows more in detail the preferred construction and circuit connections of the various electromagnetic and cam actuated controlling switching apparatus schematicah ly indicated in Fig. 1 and no further detailed description thereof is deemed necessary as it will be apparent to those skilled in the art that switches of other types and forms may be employed if desired. A reversing switch indicated as Rev. SW. is provided for reversing the direction of current flow through the motor field windings in order to reverse the direction of rotation of the driving motorsf 'The reversing switch is preferably of the drum type with stationary fingers cooperat ing with movable contact segments which are moved by I! Pneumatic' motor under the control of the electromagnetic valves 80 and 81 indicated in Fig. 2. 7 of the magnet valves 80 and 81 serves to street operation of the reversing switch to the forward and reverse positions respectively. l p I Consideration of the chart in Fig. 3, showing the sequence in which thevariouscon-. trol switches are'closed during operation of the motors in the several relations may be deferred until the operation of the control system is set forth.

Control circuits and switches.

Referring now to Fig. 4 which diagrammatically illustrates the manually operated master controllers, together with the control circuits for the electrically controlled motor switches shown in Figs. 1 and 2, it willv be seen that the reversing controller Rev. C. 18 arranged to control the energization of the magnet valve windings 8.0 and 81of-the pneumatically actuated reversing: switch, Rev. Sun, so as to' operate the same to the forward and the reverse positions respectively. I j

The selective controller, Sol. 0, is provided with suitable segments for controlling the energization of the double coil operating Separate onergization I windings 82 and 83 of theseries-parallel switch, S. P. Sun, in order to operate the latter to either the series position-indicated as s, the'series-parallel position indicated ass. 2., or the parallel position indicated as p in the drawing. pneumatic-engine which actuates the operating cams of the series parallel contactors 41 to 58 are provided with double coil operating windings merely for the purpose of simplifying the control circuits, and cnergizatioir of either of the windings 82 serves to cause operation of the series-parallel switch in the parallel to series direction, while en- 'erg'izationof either winding 83 causes operation in the series to parallel direction. In order to stop the series parallel switch in the intermediate series-parallel position a winding 82 and a winding 83 are simul taneously energized, thus balancing the'opposing actuating piston-s ofthe pneumatic engine. i

The main controller M. C. is provided with suitably spaced segments for SIICCOS sively controlling the energizing circuits of ion. The magnet valves of the r the electroma netic resistance contactors 11 to 17, 21 to 20, and 31 to 35, previously described in connection with Figs. 1 and 2, and of which onlythe'op'erating windings are shown diagrammaticall in Fig. and identified-by the same numerals as the corresponding contactors. The arrangement of the electrical interlocking segments whereby the main controller cooperates with the selective controller in controlling the seriesparallel switch tocflcct transition of the motors during acceleration and deceleration of the locomotivexwill be best understood from the description of the operation of the control system given hereafter.

The braking control Br. C. is arranged'to control the energization of the operating windings 84 and 85 of the braking switch Br. Sw., and also the operating winding 86 of the electromagnetic switch which controls the energizingcircuit for the shunt fieldwindingof. the exciter generator E shown in Figs. 1 and 2 and indicated in Fig. 4

, as EX. S. F. The win-dings 8e and 85 control the'magnet valves of the pneumatic'engine which operates the cam contacts 6l-7O of.

the braking switch from the motoring to the series, series-parallel rand parallel brak ing positions and from the braking to the motoring position respectively.

'VVith my improved control 1 system, 1 the mechanical interlocking required for insurproper operation of the several controllers'is reduced to a minimum. For single end control the only mechanical inter,-

' locking is between the reversing controller and the maincontroller. In accordance with stanclard'p ractice, these controllers are interlocked so as to prevent operation of the reversing controller when the main controller is, in any position except the off position. If double'endv control is desired, the

. braking. controller may be mechanically in terlocked with the main controller to prevent operationof: the reversing controller to the as? position unless the braking controller is in the normal or motoring position.

It: will be observed that several of the electromagnetic line and resistance controll ng. contactors are providedwith auxiliary interlocking contacts, which are shown in Fig. t'm proximity to the operating wind;- ings of'the contactors and are identified in with the subscript a, b, 0, etc.

1 parallel switch and also the braking switch are providedtwith a plurality of auxiliary electrical interlocking segments as will be apparent from the drawing. The purpose and arrangement of these interlockingsegments willbe apparent from the operation of the system; The interlocking relays R1 lcr Sel. C. and the main controllerM, (1 in cai'isingoperation of the control. system: to

effect transition of the motor connections in almanner which also, will be described more fullyhereinafter .in connection with the operation'of the system. Each of the relays R,

and R, are of the electromagnetic type and the relay contacts are biased to the positions in" which they are shown.

The main line circuit breaker QB; through ated the closed position by the resetting mit manual tripping of the circuit breaker electromagnet 88 which is'controlled by the push button P. Preferably the circuit breaker C. B. is biased to'the open position and is held in the closed position under the control of .a. holding winding 87 which may be energized through a circuit including the contacts of suitable overload relays indicated in the drawing G. L.1, 2, 3, and also the contacts of an overvoltage relay indicated as O. V. The switch 79 also maybe included inthe circuit of the holding winding 87 and conveniently located with respect to the locomotive operator in order to per- C. B. whenever desired.

I Series operation.

Ordinarily it is desirable to start the locomotive with the driving motors connected in the series relation n order more easily to control the motor current and torque in accelerating a train. The'manipu lation of the master controllersfshown in Fig. 4 and the response of the electrlc switches controlled thereby in effecting. an acceleration of the locomotive with the motors in the series connection and in the forward direction is as follows: The circuitbreaker GB is closed by operating the push button PB. The

V the drawing by. the number of the contactor The seriesand cooperate with the, sclective'controlnet valve windingc80 of the motor reversing.

switch pneumatic engine, the circuit extendingfrom a suitable source ofsupply indicated as in Fig.4, through the main controller M. O., the reversing controller Rev. C. and'the winding 80 to' ground. If not already therein/the. pneumatic engine controlled by winding80 at onceoperates the reversing switch to the forward position to connect the motor-field windings in the proper relation for forward rotation. Also incasev the series parallel switchpS. P. Sw;,

' is in the series-parallel or the parallel position, the righthand operating winding 82 is energized from the source through the reversing controller, the selective controller,

theconductor 101, the left-hand winding 82, V

the conductor 102, and 'the'auxilia'ry contact 22 of the electromagnetic contactor 22 to ground. This effectsv operation of the seriesparallel switch to close the contactors 41, 48,

50, 53,55-and 58 as indicatedforthe first step of series motoring in-the sequence chart which the motors receive current from the trolley a shown in Figs. 1 and2 is opershown in Fig. 3 and thereby interconnect the motors in: the series relation.

. Operation of the main controller into the I first posit-ion p'1 also energizes the operating windings of theelectromagnetic line contactors ll,-6,-

and 8.

With. the; arena breaker C. B. in the closed position, the resulting closure of the line contactors connects the driving motors to the trolley in the series relation, and the motors at once start to drive the locomotive in the forward direction at the minimum speed.

The power circuit for the series operating relation of the motors is shown schematically in Fig. 7 and may be traced in Fig. 1 from the trolley T through the circuit breaker C. 13., the line contactor 1, the resistors R,,R,,, the line contactor 7 the resistors R R the line contactor 8, the

resistors R -Ji the line contactor 6, the

armatures A,-A,, the-contactor 41, armature A contactor 48, armatures Ai -A contactor 50, armatureA field F contactor 53, fields F and F contactors 55 and 70, field F contactor 58, field F and F and through ,the contactorfi? to ground.

To accelerate the locomotive, the main controller M. C. is advanced notch by notch from the first position. During this advancement ot the main controller, the energizing circuits for the several resistance contactors 11 to 85 are established in a predetermined sequence so as to close the same at the respective controller positions 2 to 16 as indicated in the sequence chart in Fig. 3. The various energizing circuits for the operating windings of the resistance contactors are shown in Fig.4, and will be apparent to those skilled in the art without detailed description. Advancement of the main controller M. C. to the operating positions p17 and 7918 establishes energizing circuits tor the field shunting contactors 71 to 7 8 as indicated in the sequence chart.

If desired motoring operation may be started with the motors connected directly in the series-parallel or the parallel speed combination without passing through a lower speed combination.

Series-parallel operation.

Thus in case the selective controller is operated to the series-parallel positlon indicated as S. P. with the main controller in the off position or before the main controller M. C. is advanced beyond the first notch, the interconnection of the motors iirthe series-parallel relation as shown in Fig. 8 is immediately accomplished. Under these conditions the operation of the selective C0111 troller into the series-parallel position energizes the left hand magnet valve winding energization of winding 83 causes movement of the series-parallel switch toward the an 'iliary contacts with which the seriesparallel switch is provided. A slight tur ther advance of the series-parallel switch completes the energizing circuit for the right hand magnet valve winding 82 extending from the selective switch Sci. 0. through the conduct-or 103, the right-hand winding 82, and the ground segment 201. WVith the windings of both magnet valves 82 and 83 energized, the operating pistons of the pneumatic engine are balanced, thereby stopping the advance of the series-parallel. switch substantially in the series-parallel position. Referring to the sequence chart under the heading Starting from. rest in parallel, it will be observed that the seriesseries parallel contactors 41, 45, 46, 48, 49,. 5.0, 53,

55, 56,,and 58 are operated to establish the series parallel motoring connections with all 01 the resistance in the circuit to limit the motor current. As indicated schematically in F ig.j8, the motors noware connectedin parallel groups, each containing three motors, the motors A A and A with their respecth'e field windings F F and F receiving current from the trolley T through the, circuit breaker C. B. contactor 2,v the resistances R,,R contactor 8, the resistances R -R contactor 6, armatures A and A contactor 41, armature A contactors 45 and 46, field F contactor 58, fields ll and F contactor 67 to ground. The motors A A and A receive current through the contactor 1, resistors R,,R contactor 4, contactor 49, armatures A, and A contactor 50, armature A,, field F contactor 53, fields F and F contactors 55 and 70, field F contactors 57 and 67, to ground. Contactor 10 also is closed connecting resistors R, R in multiple with resistors R R, and B -R which are in series with each other. resistors are so proportioned that with all of the resistors in the motor circuit,.as Shown safe value even when the series parallel motoring connections-are established with the motors at rest.

Advancement of the main controller M. 0. through the successive operating positions 122 to p18 causes operation of the resistance contactors 1135, and also the field shunting contactors 7178, to short circuit the corresponding resistances R K, and accelerate the motors in substantially the same manner as described in the full series acceleration of the locomotive. However, it may be noted at this point. that in a series-parallel accel eration of the motors certain of the resist- The l 1 I a I n l in Fig. 8, the current 1S limited to a suitable r ance controlling contactors, such as contactors 14, 15, 21 and 25 are ener ized at different notches onthe main controller than during a series acceleration. This variation in the sequence in which the resistance contactors are closed is accomplished through the agency of the auxiliary segments on the series-parallel switch and enables the motor torque to bevaried in substantially equal increments in each speed relation as will be explained more fully hereinafter.

Parallel operation.

If the motoring operation is started the parallel speed combination, as maybe desired with the locomotive en 'a relatively steep down grade or coasting, this is accomplished with the main controller M. C. 1n

either'the off or the first notch by moving the selective controller into the parallel posi tion shown as p. 'The' selective controller in position pestablishes a :circuit extending through the conductor 105, the right hand magnet valve winding 83, the conductorilOG,

and the auxiliary contact 31.1 on contactor 31.

lVith the series-parallel switch in either the series or the series-parallel position, the pneumatic' motor immediately starts operaton to the full parallel position. position is approached, the energizing circuit of the right hand magnet valve winding 83 is transferred tothe ground segment 201 in the same manner as previously described. The resultingparallel motoring connections are shown schematically'in Fig. 9 with all of the current limiting resistance in the motor circuit In this "case the full resistance limits the current to a sale value'even though the parallel connections are established with the motors'at rest. This again permits 0})- cra't'o'n oi the main controller M. C. to remove the resistance from the motor circuit-s and shuntthe'motor lield windings as inthe' series or' series-parallel acceleration. In

this case the resistance contactors again are closed in a sli htly diii'erent sequenceupon fco . and contactors 57 and '67 to round.

the'operation olthe main controller M. C. through the same notches in 'order to vary the motor torque in substantially equal in crements in the parallel operating relation of the motors.

In the parallel speed combination the motors areoperated in three parallel groups, each composed of two'motors. The motors A and A Fig. 1, receive current through the contactor 3, the resistor R -R con- 'tactor 6, armatures A and Agcontactors 43 and l'hsthe field windings F F and the contactor67 to ground. The'second paral lel motor circuit extends through the contactor '2, resistances E -R contactor 5, contactor 42, armature A contact'or 47, armature A field F conta'ctor 54, field F The third parallel motor circuit extends through As this contactor 1, resistors R R contactor 4,

contactor 49, armatures A and A contac- I tors 51 and 52, fields F and F and contactors 5'6 and 67 to ground. Contactors 9 and 10 are also closed connecting resistors R R R ,R. and R ,R in multiple with each other.

Transition control.

It should be noted 'that with the main controller in either the oil position or the first not-ch, the interconnection of the motors in either the series, series-parallel or the parallel relation, is accomplished by the seriesparal lel switch immediately upon the operation'of the selective controller to the corre-' binat-ions. This is due to the fact that with V the regulating resistanceremoved from the circuits, the large variation in motor torque occurring upon the change in the interconnection of the motor imposes severe jolts or shocks upon the locomotive and train, which obv lously'are harmful to the equipment and I hence undesirable.

In accordance with the present invention,

the transition of the 'motor connections between the several speed combinations is automatically controlled so that the transition is accomplished only when the resulting change in motor torque is of limited value. In order properly to control the transition of the motors duringacceleration through the series and series-parallel to the parallel.

speed combination, the electroresponsive relay R shown in Fig. 4 is arranged to cooperate with the selective-controller and the nain c'oi'itroller in such a manner that while the selective controller may be operated to a higher speed combination position with the main controller M. C. in any one of its operative POSltlOIlS, nevertheless the actual transition into the speed combination selected is not made until the main controller MLC. has been operated to insert a suitable amount of resistance in the motor circuits.

Likewise, in transition during decelera- 'tion from the high speed parallel combination through the series parallel to the low speed series combination. the electroresponsive relay R shown in Fig. 4 insures that theitransi-t'ion as preselected by operation of the selective controller is made only when the proper amount of resistance has beeninserted into the motor circuits. Consequently the acceleration or deceleration of the locomotive is smooth and gradual, and there is no appreciable'shock imposed upon the locomotive or the train during the transition of the motor connections.

Trrmsitz'onseries t0 series-prtrallel.

A typical acceleration of the motors from the series speed combination, through the series-parallel speed combination, to the parallel speed combination is as follows:-

Let us assume that a considerable portion of the resistance in the circuit with the motors in the series speed combination has been removed by operation of the main controller M. C. to one of its higher speed positions such as, for example p16, and that it is now desired to change the motors into the series-parallel speed combination to permit higher speed operation. The selective controller Sci. 0. may be operated to the seriesparallel position immediately. The motors, however, continue to operate in the series relation with the resistance removed from the circuit. V

V] hen the selective controller is operated to the series-parallel position an energizing circuit for the relay R is established eX- tending through the conductor 108, the seg ment 202 of the series parallel switch, seg ment 203 of the braking switch, and thence through the operating winding of the relay it, to ,ground. The relay R, at once closes its contacts and completes the circuit through which the electro- magnetic contactors 2, 17, 25 and 35 are maintained energized even though the main controller is operated from the notch p16 towards the off position. The maintaining circuit for cont actor 2 may be traced from the main segment of the controller M. C. through the conductor 107, the contact R contact 2,, segment 219 in series-parallel switch, to the operating winding of electromagnetic switch 2. The maintaining circuit for the other contactors extends from the main segmentof the controller M. 0. through the conductor 107, the contact R the auxiliary contacts 35 thence through the operating wind 'ings'l'f, 35, and through contact 35 and operating winding 25, in parallel circuits to the conductor 108, segment 204: of: the main controller to ground. The main controller M. C. then is moved from the running position 7216 to the position 295 without disturbing in any way the full series operation of the driving motors.

As soon as the main controller M. C. reaches position p5, the maintaining circuit for the electromagnetic switches 17, 35 and 25 is interrupted, since the contact segment 204 of the controller M. C. leaves the stationary contact cooperating therewith as the main controller passes from position 726 to position 795. This causes the insertion of suitable portions of the resisto rs R lt since the series parallel connections are established with the motors already in operation. Due to the energization of the winding 83, the series-parallel switch operates to shift the motor connections from the series to series-parallel relation. At the same time, the left-hand magnet valve winding 83 is energized through a circuit extending from the selective controller Sel. C. through the conductor 103, the left-hand magnet valve winding 88, the segment 200, theconductor 109, auxiliary contact 2 of the contactor 2, segment 206 of the braking switch, conductor 110, thence through segment 205 of the main controller to ground.

Due to the fact tl at the resistors are inserted in the respective .motor circuits as sition is completed, and there is'no appreciable jar or jolt imposed upon the locomotive by the transition.

The motors are accelerated in the seriesparallel relation by operation of the main controller M. C. to remove the resistances irom the motor circuits in an obvious man ner.

Transition, series-parallel to parallel.

If the acceleration of the locomotive is to be continued with the motors in the paral-' lel speed combination, the selectivecontroller Sel. C. may be operated to the parallel position P at any time during the acceleration of the motors in the series-parallel relation. In the parallel position P, the selective controller again establishes an energizing circuitth-rough the relay 1%,. The relay circuit now extends through the conductor 105, the segment 207 of the series-parallel switch, the segment 203 of the braking switch, thence through'the winding of the relay R, to ground. The relay B, at once closes its contacts preparatory to re-establishing and maintaining a circuit for the operating windings of the electromagnetic contactors 3, 17,25, and 35 when the latter is closed by operation of the main controller to position;

p16. In this way the resistance in the motor circuit is maintained short circuited while the main controller M. C. is returned to the position p5 to effect the transition into the parallel speed combination of the'motors.

This maintaining circuit for the resistance control contactors 17, 25, and 35 is interrupted the motor circuit before the transition of the 'motors into the parallel relation tanes place.

quently the several groups of resistances which were maintained shortcircuited by the contacts 17, 25, and 35 are reinserted 111 However, the resistance con-trolling contactors 21, 22 and 31 remain closed to short circuit the corresponding resistors. Nhen the main controller reaches the position p5 the right hand magnet valve winding 83 is energized through a circuit including the selective controller Sel. (l, the conductor 105, the right-hand magnet valve winding 83, the

contact segment 208 of the series-parallel switch, the auxiliary contact 3, of the contact 3, the segment 206 oi the braking switch, conductor 110, and thence through the segment 205, to ground. The series-parallel switch is at once operated to interconnect the motors in the parallel relation.

The several groups of resistances are removed from the motor circuits upon operation of the main controller M. C. in the manner previously described-to cause operation of the motors at maximum speed in'the parallel relation.

The motor circuitmay be interrupted while the motors are connected in either the series or parallel relation sin'rily by opera-' tion of the controller M. C. to the oti position, thereby interrupting the energizing circuit of all the electromagnetic contactors which control the motor circuits. Thus it will be seen that no transition of the motors 'in stopping is necessary.

Tramsitioa, parallel to. serz'eapcmllel.

However, should the service conditions under which the motors are operated vary so that it becomes desirable vto transfer from the parallel speed combination to the seriesparallel combination, as for example in ascending a heavy grade. This r adily may be accomplished without interrupting the continuity of .the motoring effort. The relay R cooperates with the selective controller and the main controller in effecting the tram sition without any such changes in the motor current and torque as would impose undue shocks or. strains upon the equipment.

Thus with the motors operating in the ara'ljlels )eed combination theselective conmoved out again to notch 914 which is the notch in which the transition takes place.

The main controller M. C. is then operated to successively deenergize certain ofthe electromagnetic resistance .controiling contactors 1135 in the reverse order from that in which they are energized as shown in the sequence chart, thus inserting resistance in the motor circuits to decelerate the locomotive;

The operating winding of relay R is energized through a circuit extending from the selective controlled through the conductor 103, the segment 209 01 the series-parallel switch, conductor 111, the auxiliary contact 28 which is closed when the contactor 23 opens, and the winding of relay B to ground. The resultin operation of relay R interrupts .the energizing circuit for the electroresponsive.contactors 11, 12, 13, 15, l6, 17, 23, 24, 25, 32, 33, 34L, and 35 by opening the connection for the operating windings of the several respective contactors. Thus, upon the advancement of the main control ler M. C. from the notch p6, no change in the motor circuit occurs until notch. 19-14 is reached. a

In the notch p14 of the main controller the contact segment 210,,togetherwith the sta-' tionary contact cooperating therewith, completes the energizing circuit for the magnet valve winding 82 to effect operation of the series-parallel switch from the parallel position to. the series parallel position. The

circuit may be traced trom the series-parallel segment of the selective controller through the conductor 103, the right-hand magnet valve winding 82, the interlocking segment 211 of the series-parallel switch, the contact R which is closed when the relay R ;is energized, the segment-212 of the brakin switch, and thence through the cor ltact segment .210 ofthe main controller to ground. During the resulting operation of the. series-parallel switch to the seriesparallel position, the energizing circuit of the right handmagnet valve winding 82 transferred from the segment 21.1 to: the grounded segment 201 and iilie';l6ftl.1l1ld magnet valve winding 83 also is automatically energized through the conductor 103 and the ground segment 201 of the seriesparallel switch to balance the pistons of the operating pneumatic engine, thereby stopping the series-parallel switch in the seriespara llel ,position.

At substantially the same time the energizing circuit of the relay R is interrupted by the disengagementot' contact segment 209 from the stationary contacts cooperating therewith. The relay R at once returns to the position in which it is shown in Fig. 4%, and thereby reestablishesthe energizing circuits for the electromagnetic contactors ll, 1 2, 13 23,724, 32-, .33 and 3e,

which were maintained deenergized during the movement of the main controller M. C. fromposition ptltoposition p14. The resulting operation of these electromagnetic contactors isto remove a large share of the resistances from the motor circuitsas soon as the transition of the motors from the parallel speed combination to the series-parallel speed combination is completed, and 'conse quently the motor current'and torque are not varied materially.

Theprecise manner olaccomplishing the transition of the motor connections from the parallel relation to the series parallel operating relation without interrupting the continuity of the motor driving torque is indicated in the portion of the sequence chart of Fig. 3' under the heading of Turning off. This chart shows the exact sequence in which the various circuit controlling switches indicated in Fig 1 are operated to shift the motor con nection while maintaining at least a portion of the motor connected in'the supply lines at all timesduring the transition period." The principal steps involved in th s transition are indicated schematically in Figs. 14;, 15, 16 and 17. F ig. ,14. shows the motors connected for operation in the parallel relation with the transition resistor R and R short circuited. I The severalrzrougs of mctor torque and speed controlling resistors 111 R1,77 R21 B'25 and a1 :i5 a are short circuited to permit full high speed operation. I Upon the manipulation of the'main controller MC and the selector controller SELC to affect the transition from the parallel operating relation to the series parallel operat ing relation in the manner described above, the initial change in the motor connections 'as shown in l 'ig. iseti'ected. In this step It will be noted that the several groups of torque and speed resistors are reinserted in the motor circuits. In addition, the transi-v tion resistors R -R are inserted respecti'vely inseries with the motor armatures A A and Ar s Also the motor arma- The transition is completed by disconnectingoneend of the transition resistors R and'R from the c1rcu1t,thereby inserting the corresponding motors A and A, in the However, the remaining circuit. Thus it will be seen that the con tinuityi of the driving torque motors f A.A and AsA is maintained throughout the entire transition. l

It may be noted that the transition is intentionally made on notch p14 of the controllcr so that a portion of the accelerating resistance will be left in the'motor. circuits after the transition is completed. This is one of the novel features of the control and the reasons for doing this will be more fully.

disclosed hereinafter. Briefly the resistance which is leftin the motor circuits acts as a cushioning resistance and reduces any tendency of the current in the motor circuits to increase which otherwise might take place shouldthe trolley voltage be increased due to the transitionon the locomotive.

Thev locomotive is now operating in. notch p14 of the series-parallel combination of the motors. If it is desired to -operate in the full series-parallel running position the controller maybe moved to notches 7016, 17

or 18 in the usual manner for accelerating the locomotive. r

If it is desired to decelerate the locomotive, the main controller M. C. is moved'progressively from position p14 'toward the off position. i V 7 Transition, series-parallel t0 series, If, in the meantime, the operator has decidedto continue the'deceleratlon of the locomotive through the series speed combination of" the motors, the selective controller Sol. 0. is moved to posit'on S; Under this condition, when the main controller reaches position 796, substantially the same sequence of operation as previously described V in the transition from parallel to series parallel. is repeated. The relay R5 isen- .ergized through a circuit extending front the series contact segment or the selective controller, the conductor 101, the series parallel switch interlocking segment 220, conductor 111, the aunlllary contact 23 thence through the winding of the relay R to ground; As previously described, the

relay R maintains the energizing circuit of the resistance controllingcontacto- rs 11, 12, 1.3, 15,16, 17, 23, 24-. 25, 33, 34. and 35 open while the main controllerM. C. is advanced from'position 296 to position 1214. In the latter position, the main controller segment.

210 establishes an energizing circuit for the left-hand magnet valve winding 82 to operate the series-parallel switch from the series-parallelposition to the series position.

hiscircuit extends from the series segment of the selective switch which is energized from the source through the conductor 101, left-hand magnet yalve "winding 82, the series-parallel switch interlocking seg-. ment- 21'3, theauxiliary contact '3; of the elect romagnet line contactor f3, contactR of the relay R the braking switch seginent 212, thence through the main controller segment 210 to ground. As the seriesparallel switch operates to the series posi- 'tion,theenergizing circuit of the left-hand celeratingresistance is short circuitcdwhen these cont-actors close and the locomotive is operating in notch 7914 with the motors, in

the series combination. v Should it be desired to operate the locomotive in the full series runningpositionsthe main controller may {be 'nioved out to notches p16, 17 or '18 in the usual manner for accelerating the locomotive. Should it be desired to decelerate the locomotive still further the main controller M. C. may be returned from position 14 toposition 191 to deenergize the contactors 11 to 35, thereby inserting; all the resistances in the motor circuits to obtain minimum'speed operation in the series connection.

It should begnoted that the motor circuit may be interrupted to stop the locomotive at any time during decelerating operationwith the motors connected in either the par.-

allel, the series-parallel, or the series relation, simply by returning the main controller M. C. to the off position. This may be done irrespective of previous operation of the selective controller, since all of the electromagnetic contactor circuits are interrupted with the maintontroller in the ofi position. v i

From the toregoingit will be evident that i the control system embodying the'present invention permits theinterconnection of the motors to be changed from either a lower I Consequently ,the speed of the locomotive spced combination to'hi'gher speed combinations, or from a higher speed combination.

to, lower speed combinations in a manner.

which insures a gradual and smooth. acceleration' or deceleration of the locomotive.

may be varied at will to conform with the service conditions encountered without danger of biniching the slack in the trains as would occur incase the motor circuit were interruptedduring transition of the motors between the various speed combik nations. Furthermore, by not short circuit- 'ing all the accelerating resistance after a transition from a higher speed:- toa lower speedlcombination of the -motors is completed .a novel feature is introduced which is an improvementv over the present method of making such transitions.

V Regenerating banking operation;

The braking operation of the motors is under the joint control of the selective con? troller Sel. C., the main controller M. (3., and the braking controller Br. C'.,-and the reversing controller of course determines the direction of operation. It will beobserved that tliebraking controller is provided with suitable segments for controlling the exciter field resistance Ex. F. R. and alsofor con; trolling the operation of the 'exci-terfield switch 86, as well as the magnet valve windings 8 1 and of the braking switch Br. .S'w. be initiated in the following manner. Assuming that the motors are operating in the full series relation (M. C. in notch p16), the

main controller M. C. is returned to thefirst position, thereby deenergizing the several groups of electromagnetic resistance controlling contactors, including the contactor 31.

The braking controller Br. C. then maybe operated into any (meet the braking posi- Re renerative brakin 0 eration ma tions b b depending upon the estimated value of field excitation required in the part cular service conditions under which the locomotive is operated. Assume that the braking controller is moved into the braking position b As the braking controller passes through position b the operating winding of the exciter field switch 86, to-

gether with the magnet valve-windings 84' and .85 of the braking switch, are energized in parallel through a circuit extending from the source through the main segment of the main controller M. (l, the conductor 112, auxiliary contact 31 of the resistance controlling contractor 31, and thence in paral lel circuits through the magnet, valve windinjgs 84; the segment 215' of the series-parallel switch, the magnet valve winding 85, the segment 214 of the braking switch; and through the auxiliary contact (1B of the circuit breaker, the operating. winding of field SWltCllBG to the conductor 113, which is grounded through the 2 segment 216 of the braking controllen This results in the energization of the exciter shuntfield indi- Ill) cat-ed as EX. S. F. through the circuit exis of the type which is biased to admit air to thepneumatic engine when the windings are deenergized, Consequently the braking switch pneumatic engine functions to move the braking switch into the intermediate series and series-parallel position. As the intermediate position is reached, the pneuinatic valve winding is deenergized by the disengagement of the segment 214 from the stationary contacts operatingtherewith, thus balancing the pistons of. the pneumatic engine, thereby stopping and maintaining the braking switch in the intermediate position. \Vith the motors operating in the series relation; movement of 'the braking switch into the intermediate position closes the. cam contactors 62, 63, 65,.and 69 and opens cam contactor 70to thereby connect exciter E to the motor circuits and est-ablish ground connections between the motor armatures and their respective field windingsto permit over-excitation :of the lat ter from the cxciter generator E; The rcsulting series regenerative braking'connections arepshown schematically-in Fig. 11.

Due to the fact that all the resistance is inserted in the motor circuits when the main controller M. C. is returned to position 791,

the current of the circuit is limited to a small value. Preferably the braking con.- troller Br. C. isset at such a position that the shunt field winding of the eXciter generator E is overeXcited only a slight amount. consequently, the overexcitation of the motoi' field windings is of such value that the motors continue to receive current from the trolley T. The main controller then is advanced from the position pl to position p16 to remove the resistance fl'OliliillG motor circuit and byproperly timing this operation it may be performed-when the motor current input from the line is substantially zeroin amount. The braking controller then may be operated to increase the over excitation of the motor field windings to 1 cause the motors to return current to the trolley T, and thereby produce a regenerative braking action of the desired value.

Regenerative braking'with the motors in the series relation, as shown in Fig. 11, is ordinarily employed atslow speeds of the locomotive; In case jloraking at higher speeds is desired. the motors'areinterconnected, in the series-parallelor the parallel speed relation. *As it"is undesirable to effect transition or the motors from one speed combination into different speed. comb-ina tions while the motor field windings are overexcited due to the fact that some of the motors necessarily are short circuited 'during the transition, it is necessary to hold or retard the train by means of the customary form of airbrake equipment, and interrupt the motor circuit-duringthe transition from one speedconibinationto a ditlerent speed combination in regenerative braking operation.

Thus, with the motors in the series brak-' ing relation as previously described, the

change into the series-parallel braking i'elation, assliown in Fig. 12, is accomplished by returning the braking controller Br. C. to the normal or motoring posit on M, shuts switch. to the intermediate. series-parallel position in the manner just described.

iFor parallel bralnngoperation, as shown ting off the main controller, moving the selective controller into the series-parallel iii Fig. 13, substantially the same inanipu lation of thecontrols is required, except that the selective controlleris moved into the'parallel position. i

Variation in resistance contractor sequence,

The variation in the sequence in which certain of the resistance control .contactors are closed upon operation of the main. controller through the same. series of "positions, depending upon the particular speed relation in which themotors are operating, has

been previously noted. -The manner in which this is accomplished will be apparent from a careful inspection oft-he control circuits illustrated in 4. For exampl it will be seen that the operating winding of the resistance controlling contactor 21. is

energized in position. 1930f the. main controller when the series parallel switch. S, l?.

The circuit Sw. is in the series position .9. may be traced from the supply source-t through the main controller, the conductor 114, the. auxiliary. contact segment 217 01 the series-parallel switch and thence through the operat ng winding of c'ontactor 21 to ground. this case, indicated in the sequence chart,- only. the energizing circuit for contactor 21. is closed upon the. operationof the main controller to its third notch.

WVhen the series-parallel switch is opera ated to theseries-parallelposition, contactoi" 21"is energized on the second. notch-(7:72) of the main controller M..G., and'at the same time resistance controlling contactor 31 also is energized. In this case thecircuit extends V trom the main controller M. G. .throughthe conductor 115-,andythence to the operating winding of contactor 31 and the operating winding of contactor 21in parallel circuit to ground, the circuit of the contactor 21 extending through the central portion of auxiliary contact segment 21?.

W'ith the resistors R and'lt properly pro portioiied, the. variation in the motor torque resulting from the simultaneous operation of the two contactors in the series-parallel operating relation of the motors produces a variationin the mot-or torque which is sub stantially equal to the variation produced at the same notch of the main controller in the full series'operating' relation of the motors.

In the parallel combination of the motors the resistance contactor 21 is closed upon operation of the main controller M. C. to a still. different position, namely, position [75, and the closure of contactorQl occurs simul-v taneous-ly with the closure of contactor 22.

In the parallel of the motors the energizing circuit for contactor 21 extends from the main controller through the conductor 116,

the auxiliary contact segments 218 and 217' of the seres parallel switch and theoperating winding of contactor 21 to ground, the winding being"energized inparallel circuit varied in each operating relation of the m0:-

' that after-the transition has been completed,

tors'in substantially equal increments,.thereby insuring a smooth acceleration and deceleration'of the locomotive in all connections of the, motors.

Special provision to prevent ercessz're ourrent during transitions from a higher speed combination of the motors to a, lower 7 speed one.

It should be noted that the transitions from parallel to series-parallel, and from series-parallel to series, are made onnotch pl l ot' the main controller. This insures there is still a certain amount of resistance lett n serieswith the motors. From a practical operating standpoint, this is a marked improvement over the usual: form of control,

in which the resistanceis entirely short circuitedas soon as they transition is completed since witha large size locomotive, especially those intended? for freight service, the current input to the locomotvc is often a. very large percentage of the total load on the two I substations next adjacent to-the locomotive a-nd tram. The current nnput is naturally larger with the locomotive. operating ina higher speed connection of the motors than in a lower speed connection. -Under' these conditions if a'transition ismade from a higher Speed connection of the motors'to' a lower one, the current input to: the; l'ocoino' tive is greatly decreased. (On a six motor,

' macaw three. speed locomotive li -SP decreases the current to offormer value and S'p-S to Reduction of this current input causes the voltage to rise at the locomotive if it is any great distance from the substation, agd this amount of rise is often oonsidera le.

If the accelerating resistors are entirely short circuited immediately after a transition under these conditions the current in put per motor' will be increased considerably beyond :that which would occur with a transition at. normal voltage and may cause a shock to the locomotive and train. By

leaving a. portion ofthe accelerating'resistors connected in the motor circuits during' and after the transition has taken PINE, anyincrease in the motor current which may occur due to increase in line voltage due to the transition is effectively checked.

While this same result may be obtained in the well known progressive controller form of control by moving the controller into one of the lower speed resistance notches before the series-parallel switch has a chance to throw, there is nothing in the control which requires vthe operator to do it. Nor is it so easy to accomplishv this result as. with this selective type offcontrol.

Uonstrwoflon oftke operating hzmdleof 7 main controller.

In order to enable the main controllerto be conveniently handled by the operator in performing the previously described controlling operations, it is desirable although not absolutel necessary to provide the arrangement o the operative handleshown in F'gs. 5 and 6.; In addition to the ordinary latch engaging witha notched dial ring, having each notch corresponding tofone of the-positions 1 to 18 of the main controller which it is. the usual practice to provide on locomotive controllers although not illustra-ted, the three'stops S1, 8-2, and 3-3 are provided as shown in Figs. 5 and 6. V

Stopv S-l preferably is located on top of the dial ring while stops S-2 and S-3 are located on the opposite side.

The handle 300, Fig. 6, is provided with a latch 301 which is held by .a spring. 307 so that one face of this latch 304 normally bears against the top side of the dial ring 302' while the other face 303 of theil'atch 301 is held byspring 307 clear ofthe lower face of the dial ring 302. I

Stop- SI1 is arranged to engage with face i 304 of latch 301 when the handle 300 is moved .to the postition corresponding to notch 7516 of the main controller-(Fig. 4).

This indicates to the locomotive operator that the controller. has been brought into the full field running position. In order togo' beyond notch p16 into'the reduced or shunted field running positions p17 and 1218 it is necessary for the operator to press the button 305 in the'end of the handle 300 which brings'tlie rod 308 intoengagement with latch 301 compressing spring 806 and raising" face 303 .into engagement with the lower side of the dial ring 302 andraising. face -1 out of engagement with the stop S 1, thus permitting movement ot'th'e handle into notches p17 and 2918. This construction is old and welllrnown' in the art. g

When transitions going from a lower speed combination of motorsto a higher speed one are to be made it is necessary first to bring the controller into the notch plfi'andthen to move it to notch p5. The stop, S 2 is so located asto engage with face 303 of latch 30]v when the" handle .300 is" moved backinto notch p5 providingbutton 305 is pressed in raising face 3030f latch 301 into engagement with the under side of the dial ring. As the steps p15 to 290 inclusive produce no change in the locomotive torque during this operation'it is intended that. the operator shall press the button 305 in the liandleonvnotch p10 and hold it in, moving the controller rapidly toward the off position. Engagement of thehandle with stop 8-2 will indicate when thecontrollerreaches the notch 225011 which the transition to a hi'g ierspeed combination of the motors takes place Similarlystop S3 is arranged to engage with face 303 of latch 301' when handle 300 is brought into notch p14. This enables the button 305 to be depressed, held depressed and the" controller handle moved rapidly from notch 796 to notch plwhen making transitions from a higher speed combination ot the motors to a lower speed one.

The use of stops S-2 and 3-8 greatly facilitate the manipulation of the controller during transitions.

WVhat I claim as new and desire to secure by Letters Patent of the'Unite'd States, is,'--

l. The combination with a pliiralityot electric motors adapted for operation in a plurality of speed relations, of means for controlling the speed relation in which'the motors are to operate, and independently operable means forcontrolling the operat-' ing speeds of the motors and arranged to cooperate with said first'ineans for controlling the interconnection of the motors in a lowerspeed relation without interrupting the continuity. of motor torque when the motors are operating in a higher speed relation.

2. The combination with a plurality of electric motors, of switch mechanism for interconnecting the. motors for 'operation'in each of a plurality of speed relations, separately operable switchmechanism tor varying the speed of the motors in each of said relations, and means cooperatingwith said separately operable switch mechanism for to those skilled causing operation of the "first switch mechanism tocliange the interconnection of'the motors to a lower speed relation without interrupting the continu ty of moto'r'torque upon a predetermined "operation of said separately operable switch mechanism when the motors are operating in a higher speed relation. f v 3. The combination with a plurality of electricn'iotors, of switch mechanism for interconnecting the motors for operation in each of a plurality of speed relations, sepf arately operable switch mechanism having a plurality of o era'tive positions for vary ing the speed of the motors ineach of said relations, and means depending upon operation of said speed controlling switch inech-c ing in a higher speed relationf 4. The combination with a plurality of electric motors adapted tobe interconnected for operation in each of a pluralityof speed" relations, ot means'for selecting. the speed relation in which the motors are to be operated, independently operable means for controlling the speed of the motors in each of said speed relations, and switch mechanism arranged to beijointly controlled by said means to changefthe interconnectionot the motors to each other speed relationwhen the anisin into at least two of said operative positions for causing operation of tlielsaid' motors are operating in eachot said speed ity of the motor torque.

relations withoutinterrupting the contin'i 5. The combination with a plurality of electric motors, of electrically controlled switch'mechanism for interconnecting the motors for operation in a plurality of speed" relations a selective controller tlieretor, an

independently operable speed controller tor i 'aryin o the speed of the motors in each ot" said relations, and connections arranged upon operation of the selective controllerto be controlled by said speedcontroller' when the motors are operating in higher speed relationtlirough which the electrically controlled switch mechanism is operated to change the interconnection oi"- the motors'to a lower speed relation without, interrupting its the continuity of motor torque upon a pre determined p ation of said speed eon troller; p V 6, Th combination with a plurality -f electric motors, of power actuated switch; mechanism for interconnecting the motors in each of a plurality of speed relations, a controller forvarying the speed ofthe mo tors in. each of said-relations, and "an inde pendently -operable controller 7 arranged to cooperate with said speed controller' during operation of the motors in'each one of said

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