Letters Patent of the United States, is: The -conihination, with an alternating -current indtictioii moior ad:ipted to drive iii(I to I)e di-iven bv an active load, of s,%vitch for e@tablishing'power conneeTo tions for the motor, a resistor arranged to be coiinect6d iii circuit with t-he motor for varying the operating speed thereof, and means I-esponsive t o the speed of the motor for autoi-natically establishin(y a shoi-t circuit 75 aboiit said resistoi, upon@ a change from 'motorin(, operation to. brakin- operation of said mot"'or. n 2. The combination witli an alternating current induction inotor adapted to drive 80 and be driven by "an active load, of switell mechanism for establishing power connee'tions for the motor, a speed controuing resistor connected in the secondary citcuit of the motoi-, independently operable switch 8r) inechanism for controlling a short circuit around the said resistor to vary the speed of the 'Motor, and autoniatic inean@ responsive to the speed of the motor and arranged to effect, operation of said iiidependently op- 90 erable switch mechanism to establisli a sl-iort circuit about said resistor when the operation of said motor changes from motoring to braking opel-atioil thereof. 3. The coinbination with an alternating 95 current induction motor adapted to drive aiid be driven by an active load,-of a resistor connected in the secondary circuit of the motor for controlling the subsynchronous operat-ino, sp@ed thereof, and switeli mecha- 100 nism responsive to the speed of the motor arranged to establish a short eireiiit about Said resisl-lor upon a chaTiLre froiii motoring operation to braking operat@ion of said motor. 4. The combination with @n electric motor, 105 of reversing switch mechanism for controllino, the condection of the motor to a source of supply, tnd means for controlling said reversiner switch mechanism includin(y a, controller having an off and a plurality of op- 110 erative positions and arranged to effect op-@ eration of the reversing switch mecbanism to connect the motor for operation in one clirection wlien the controller is Yrioved to a predetermined operative position from the 115 off position and to connect tl-ie motor for operation in the opposite direction when the controller is inoved to said predetern-iined operat-Lve position from another operative position. 120 5. The combination with an eleetric motor, Of reversing svviteli mechanism for controllino, the power coniiections of the iiiotor, and me@ins for controlling slid switch inechanisiii includin(r t controller havino, a plui-ality of 125 oper,.ttive positioiis ancl arranged to e@fect operation of the reversina switch mechtnisill to establisli and rna intain PoNNer connections for operation of the motor in one (lirection when the controller is moved through an 130

interi-nediate operative positioii froni oiie oper,itive position to a second operative p(sition and to es'L-ablisli reverse power coiineetions for the motor wlien the conti-oller is retui-ned from said secodd I)osition to said intermecliate opeiative position. 6. The coinbination witli an el(,,cti-ic iiiotor of i-evei-sinswitch iiiech,,tnisiii foi- conZ, trollin(r the poivet connee'@ioiis of the iiiotor 10 an(I mearis foi- codti,olliii- sai(-l i-evei-sliig switch mechanism incluclin- ,t controller liaviii(- ,in off an(I t pltii-,tlity of opei,.ttive posittoiis and at-rai)-eci to eff(,ct. opei-,ition of the switch ineclia-iiism to estat)llsh t, 15 poiver connectioiis foi- ol)ei@ation of the motot- in one dii@ectioii wlien the conti-oller is nioN,e(I -I'rojii tlle off po.sition to ari opei,,,ttlve posi 'tion iTit(,,i,iiie(liate two otber ol)ei-ative 't posi -ioii,,, an(I to iiia'ntain saicl powei- coii20 nections establislied wlille the coiiti-olle, is ,idv. tneecl to one of @,:tid other opei,,itive 1)ositioiis and to cqtablisli and mainttin i-ei,orse powei('OnDC'ct.]oDs for the iiiotoi, wheii the coiti-ellet. i.,@ i@etiii-iie(I tlirou(,,Ii siid lii25 t(-,i,medi,,i'e po,@ition fi-oii-i said oiie of@ opc@i-ativ(@ positions to the otlier of said ol)ei@,itive positions. 7. The, coryibinatioii of an electi-ic motor adapted to,(IriN-e and I)e driven I)y an a(,-tive lo,,'.(I, of clecti-oi-esponsive i,evei,sin(y ;wltcb iiiecbanisni foi- conti-ollin,,, the poivei, coni-@ections of the iyiotor, aiid meiii@,, l'oicoiiti-olliiag sai(I i-eierciing switch mechaiiisin iiielti(iiii,, a eonti-oll.ei- litving an off pOSitiOn 35 @in(I t I)Iurality of opei-ative positions and to eiffect opoi-at@lon of the reversill(y SIA-iteli mc(-Iianisiii to establish powei- confoi, opoi-ation of the, iiiotoi- to cli,ive @li(@ lo@i(I in one i,ipoii niovcnieiit of 40 the (,onti-oller froiii the off position to L pi -e(1c,t(@i-ir.ined operitln,e position and to establish t@everse power coiinections to oppose the toi,qtie of the motor to the torque of an ovei-li.itiling load upon the rettirn of the coi,- 45 ti-ollei- from anothei, posifion to sai.d pre(letei-mined operative position. 8. Tlle combination of an altetnatin- etirinduction motor a-ltpted to driv-e and I)e di-iven by ,tn active load, of a iesistor 150 @(-oniiected in the 1,@CCODclary eireiiit of the iiiotor l'or controll'ii,r the operatin(- spee(!tlieroof, electrorespoiisive switch irieclianism for controllina botl-i the power coiinectiods oi, the motor and tlio sai(i speed re,,riilatin(y 55 i,(,@4istoi, 'aii(I iiieai)s foi- e(-,ntrolllii(,,- iteli iiieebanisrr. a coiltroller ii,t@,@ii)g an off position and"a plui-ality of (,pc@i-,itive positiotis a,,-i@an@r(,,d to effect opet-- .,.tion (-,f the S,-Licl electrore,@ponsive switeli (;O 111(@(11,11lisill to 0.@@tLblisil ower p toi- opei-atioji of the iiiotor iAItli ,,,,,,Id tot- iii circuit tlici-e@N-ith to drin,e the load in o,.i(@ dii-ection upoii iiiovei-nent of tli(, (,onti-o!!(@tfl,(lil the ofT 1)(,,sition to a r,5 poqitioti tiid to establisli i-e1,708,887 verse power connections with said i-esistoiin the niotor eireiiit upon the return of the coiiti-ollei, froni another opei,,ttii,e position to said pi-(,@detei-iiiined operatix,e p(- sition. 9. The conibination of an altei-iiatiii(y etir- 7o reiit incltictioil iiiotor adaptecl to (It,lvc, ali(i to be driven by an active loa(l, of- a i,esistol@ coniiected in the secondti@y of tli(,@ niotor foi, controllin- the opei-atli)(,, spee(I t@ tlicieof, i@lecti-oi@esponsive switcli iiiecliiiiisiii 7,5 foicojitiolliii(r the po@i,or conneetiotis of the n,,o'cor aii(-l ilic said speed i-esistoi-, aijd ii-ieaii,,3 for conti,olliii(,, s,,Ii(l switeli me(@llinisiii incluclin(@- a coiiti-ollei, liii7in(-r ait tD off positioii and a plurality of ol)ei--,Itil,e so posil,ions and ai-i-aii(@ed to effect opol-@iti(ii In of the sii(I switcli meeliinisiyi to establisli powei, coiiiiection,3 for ol)ei-atioii of the iiio1 toi@ witli Stl(l I-esistol- ill C'I-Ctlit tllel.("Avitli to di-ii-c the load in ofic clirectioil iipoii iiion,es5 iiiciit of the controller fi-oiii tli(,, off position to t pi-e(letei-mined opei-ative position intei@iiie(liale t@N@o otlier opei-ative positioiis an(I to riiiii)tlajji s,,Li(I poiver Colillections estabI'slied tiiid i-emove said resistor from the go iiiotoi@ (-ii-cuit wlicn tlle controller is adi-.i,iieed to oiie )f sai(I otlici- operative position,,, to establisli i-evei'se power coiinections :I'ot- the itiotoi- witli said i-esistor in cit-cult tliei-(@iiitli tipon the retut-n of the 95 (!oiiti-ollei- to s,lil'(1 intet-iiae(.Iiate position aii(i to iiiiiiit@iiii sti(i i-evei-se power coiinections establislic(l aiid i-eiilone sild i-esistor froni tilo IDOtOl' Cil'CLIlt Wllen the conti-oller is (pei-ateci to the otlier a,' said opei-ative 100 positions. 10. In an clei-ator or lioistin- motor conti.-ol sy,,;teiii, the combiri,,ttion with an electric iiiot-oi- adapted to di,ive aiid be driven by tii active loacl, of clecti@oi,esponsive - switch 105 iyiechaiiisin for controllin(,, the poiver coniiections of the motor, and means for controlling said switch niechanisin comprisina controllei, htvin- an 'Off position, a plurality of hoistin- positions and a plurality of 110 lowerin@,;) r@ositions arranged to e:ffect opera,- tion of said switch mechanism to establish power connections foi- operation of the i)iotor in the lowerin- directioil when the controller is operated from the off position 115 to a pi-edetermined lowering position and to establish power connections for operation of the motoi- iii the hoisting dii-ection upon the i-eturn of (-lie coiitroller from another opera'@iN-c, pos'l-L@loi) to s,,ticl pi-cdetei-iiiiiied position, 120 II. Iii ,iii elevator oi- hoistin(, con[rol syst(@na, tiie coiiibiiiation with an - a'lDtern,,tting ill(luet.'on inotoi@, of a res,stor connecte(I in tl)e second@try cii-etilt tliereof for coiitl,oll the ol)ei-atlii,, sl)oed of the motol-, 1 5 tn 0 electroi-esl)onsive siviteli niechtriism fGr conti-olliji@,n, tlio powei-,coiinectiolis of t'@ic mot,r ATI(I tl-ic saicl i,-esistor,,aiid ineans for coiisiill switch iliecliaiiisin COMI)I.isjn(- a coilti-oller litviii-, aii off position interine'- 130

1,708,887 diate a plurality of hoisting positions and a plurality of lowering positions and arranged to establish power connectiong to operate the motor in the lowering direction with said :i resistor in circuit therewith upon operation of the controller from the off position to a lowerinoposition intermediate two other lowering positioiis and to maintai,n said connections established and to remove- said- re10 sistor from the motor eir6di-C Li-p n operation of tliecontroller t6 one of said other lower- ing positions, and to establish reverse power coniiections to the motor with sa:id resistor in eireiiit therewith -Lipon the return of the 15 controller to said intermediate position and to iiiaintain said reverse power connections established and remove said resistor from the motor circuit -Lipon operation to the other of said lowerino, positions. current motoi- ad,,ipted to drive and t6 be driven by an active load, of a controller havai ott position and at least one operative "ig ition ,)OS for controlli-n(r the operati'on of 25 saicl niotor, -a resistor connected in, circuit @vith said motor at all subsynclii-onous speeds thereof with sai(-l coiltroller in said operative I)osition, and means responsive to the speed of said in(?tor for short cireiiiting said re30 sistor wben said mo.tor is driien by the lotd above synchionous speed. 13. The combination with an alternatin(r current motor adapted to drive and to be driven by an active load, of a controller having an off position and at least one operative 35 position for controlling the operation of the motor, a resistor connected in circuit with said motor' for all subsynchi-onous speeds thereof when said contr(311er is illoved from off position to said operative position and 40 mearis responsive to the speed R the motor for short eircuiting said resistor when the motor i.s driven above synchronous speed by the load. 14. The con-ibination with an alternatinc, 45 current niotor adapted to drive and to ]@,e driven by an active load, a resistor connected in circuit with said motor and electroresponSi-ve switch mechanism for controllina said resistors, a motor controller havina @n off 50 position Ind a plurality of idperative positions and arranged when moved from off ti-if Ligal speed responsive device cooperating with said controller'w hen operated to said one of s,,ti(I operative positions for operating said switch meellanism to short circuit said 60 resistor when the inotor is driven by, the load a;bove synelironou s speed. In witness whereof, I have hereunto set my hand this 20th d,@y of Novembe r, 1925. J A M E S A . J A C K S O N . 20 12. The combiiiation with an alternating . position to ona of sa@d operative positions to prevent opei-ation of said savitch mechanism to short circuit said resistors for subsyn- 55 chronoiis speeds of sa'id motor, and a cen-

l @ 7 0 8 2 8 8 7 Patentid Apt. 9, 1929. UNITED STATES PATENT OFFICE. ;TAXES A. JACKSON,, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COXPANY, A CORPORATION OF NEW YORK. SYSTEX OF MOTOR CONTROL. Applicatioit filed Nov ember 21, IM. Serial No. 70,617. This innontion i,elates to tlic, control of electi-ic motors, I-,ai.- ticiil,,trly alteriiating cui-i-ent induction iiiotors tliat,afe eiiiployed in lioi-,ting, eleva'-or or otlier similar service -,iii(.1 the improvement,., pron,i(locl I)y the invention enibletbe motor to be controlled so .is to operate the load in either direetioii, a,@ well as to ret-,ird or. stop tlle descent of aii ovc@i-liaulin(I lo,,t(I in t safe, efficie'nt 10 aiicl advadta-eoiis inannet. Ill hoist, elevatoi-, oi- otlier service the cii,i-,,in- niotor may be (Ii,ivcii ],)), t desconding oiovei@li-,tulin(, loti(I it is Iiio-lll)r desii-able -froiii the stan(II)oiiit of effic'ent and 15 satisfactoi-y opel@ation to utilize the driving iiiotor as miieli as I)ossible in i-c@tarding ,tnd ,-Ioivin, (, down t.lie load in orclet to i-elieve tlie. (Iiii.y on the fi-iction 1.)rakes. @ll'itli an alteinat.',ii(, cui,i,ei).t cti,ivii)g inotor of the slip 20 i,ing iii(lu(..tion tyl)e it has! beeii coi-iiii-ionpr-.tctice to slow down the descend.ing loa(l I)y plti,r,,in(- oi- i-eversin(r the iiiotor power eoiinectl()ns with resistant-ce in the s(,coiidai-y circuit ,@o that the motor (.,xctts aii. ,tctive 25 toi-que in the lioistin- dii-eetioii aii(I in op1)()sltioii to the tot,qtie pi-o(Iticod by the deI;cendin,,- or ovei@liauliiig load. Ilowever, if I the 1(),);(l is started from rest, the actiial iiioveinent of the load obviously -vvill del)eiid til),)ii the i-elttive values of tiie I.oad toi-qiie ,in(I the lioistin(,r toi,qtte oT the motor. Wlicii the load torqtip- I)i(@(loiiiiii,.ites, the iiiotoi- toi-qiie serves to -slow (lowi the deseeiit of the load but when the iiiotor torqu(, 35 I)re(lominates the load is (Triveii iii the lioistiii(y (lir(-,ction. li.i or(ler to ,tvoid confusioii to the oper@ttor, iiayiiiil)i,oved motor conti-ol syster.1 is qrl,.tll(:ed to connect the motor so ts to ex40 ert a positive torqtie in t,lie lowei-iiig direetioii when the iiiotor i,,, iiiititlly connected to the po-,ver sotii-ce, on the loweril,til- siclo- of tlic, controller and therel)y iiisiii-(,@ th,,tt the moveiiient of the load always occitrs in the down45 Nv,,ird dii-ection. Preferably the initial lowerili(r coiineotions of the iiiotor ate such that the torqtie, of the rhotor is siifficl.elltl3, low to preven . t univindiii(y tli(@ ]lo t c-,tblc ftster tliaii the load des,,!enci-I. is 50 O@ll,li@i-wise,-undesirtble and danreToLis slaclr is introduced into the cables. FiLitiliermore, the slow acceleration of the descenclin(y load facilitat es joggin(y of the motor to lower the load a s@light amount. Whe n an alternatid(y clirl-(,Int electric mo- 55 tor of the slip rin(v induction type is employe d, the accelerating torque of the motor varies with the ainount of resistance in the, @econdary circuit and in all cases 'tlit-omatical ly terminates when synchronous 00 speed is reached. In case an overbauling lotd drives the motor, above synchronous - ,peed, the motor then automati@,ally exerts ,t brali@ing effect ,is an asynchronous genera or the v,.tlite of which -,tlso is dependent 65 lip the value of the resistance in the seeondary circuit of the m@tor. I-lence, while it is desirable,to start the motor in tl-ie lowcient resistance eving direction with suffi in the secondi,i-y circuit of tlle motor, to 70 limit the rate of acceleration of the. deseending load, the same value ofresistance ii-i the secondary circuit limits the, braking action of the motor, and consequently, periiiits the overhauling load to clrive the mo- 75 tor at an excess:ive and dingel-ous speed. One of the principal objects of the present invention is to pi-ovide a control ariian(,eiiient wherel)y a I - 4riviiig iiiotor of -the above character inaay be connected initially so to operate, the load in th(, lowering direction at slow speed and subsequently connected either at the will of the operator or autom atically to re(yenei-atively bi,,tke the load to a s,,-i'fe spee.d-in ea-,e tl@e load over- 85 htitls the motor. The control arrangement then permits the motor connections to I)e revers ed so as to oppo-,e the torque of the iiiotor to the toi,que, of the overhaulin(, load in order to tliei-ebv slow down and stop go the descent of the l@ad. Otl -ier objects of the invention will be appai-ent fi-om the desci-ipti.on of the embodi-. inent of tlie, invention illustrated in the aecompa nyi:n,,y drawin(r in wliich the, sinly e 95 rli sclieiii showing the figl're ttic di,,t(@i-ain iiiventio--,i tpplied to a contil@ol system for ann, tl@ern,,tti. - eiirrent lioist'ng motor of the slip rinc, t.ype. A.s il.fiisirated in. the drawin(y, the three 104) liase. altei.-iiqtili(y ciii@i-ent motor 10 has tbe p slip rin-,s 11' conne6ted to the secondary or rotor win(lih(rs, tnd wliile not shown in the drawing, it will be understood that the motor

2 1,708,887 is connected throiigii stiitable gearing to drive the windiiig or hoisting drun-i of ,t li,oist or elevator. Power is stipplied to the iiiiai@ pr ), windings of th@e niotor froin the slipply lines 12, tlii-oii--li the electroma,-n(,,tic lin(@, snviteli LS and oiie of the i.e-,,@ersiii,- colitactoi-.,3 HC oi- LC, the (-oiiti.(@toi, H.C beinf(@los,,,d wli(,@ii the iiiotoi, 10 iF,, opcrating in the boistiiig dii-ectioti aii(I the coiitictor LC 10 bein(,, closed in@lieii tlie, inotoi- is operatin(,, ill the lowei-@ln(, (Tirectioii. Aii electioina"netic brake 13 of any stiitiible form is provided for holdin- the iiiotoi- -tt rest when the prirtiary ivin(lings tliei,eof ire deener15 (Yized.. A centrifug@il sl)ee(I-i.-esponsive eircuitcontrolling device 14 is suitably geared to the motor sli,.i.ft and is arran-ed to cooperate, in controllin,,- the inotor in a inanner which will be more fully set foi-th in 20 connection -%vi,th the operation of the i-notor. The torqtie, an(I conse(liiently the speed, of the motor is controllecl I)y ii-ieans of the several resistors RI, R2, R@l, l@4, Aviiieb ire conne(!te(i to the seconclary or rotor wind25 ings of the iiiotoi- tbi-oii-ii the slip rin(-Ys 11, and are under the coiitrol of the (,Iect,- oD-ia-netic coiitactors 15, 16,, 17, 18, respectiv@ly. The operation of the line switch, the re30 versin(r contactors HC and LC, aiid -,tlso the resigrance controllin- contactoi-s 15, 16, 17 IS are under the control of ,t ininually operable master contr6llt,.r C wbieli is operable from the off position in whicii it is 35 Shown thro-Li(yli either the several hoistinr positions a, b, c. d or through tli(, IoNiei-in-.t positions e, f, g @t In orcler to insitre smootli and ,radii,,tl acceleration of the loa(-l durin(y botli the lioistin(y and the lowerind,O opera@Pion, the current limit relays CLRI, CLR@; have windin,---s 19 an(I 20 energized in accordance -,vith, the ' motor current tliroitgh the ciirreiit transformer 21 -wben the iiiotor is opei,ating in both the lioist45 in- and the lowerin- direction, ,ind, are n co@Tlected to cool)ei-ate with the controlleiC in controllin- the 7-ospoiise of tlle ance contactors when the motor eiii-rent exceeds a suitable operitino- i7,,iliie. 50 The reliy R and the ceiitrifugal switch 14 cooperate witli the iiiain controller C.to automatically retar(I an onrerb@,tuling lotd in a iiianiier wbich will be better Lin(lerstood from a (@onsiderttion of the operation 55 of the conti-ol system iiliieli is is follows: To start and accelerate motor 10 in the lioisting dii-ection, the control disconnecting @witcli DS is closed and the controller C is opei-ated into the flrst, lioilstin- position, in60 dicated in the drawing as a. This establishes an energizing eireiiit for tlle relay R wliieh be traced f roii-i 'uhe middle supply line m. 'y through the discoiine,@ting snvitch, the segments 22 -and 23 of the controller C, the 65 winding of the relay R, thence tbrough the coiidiictor 24a and the disconnectin(nr switeli to the ul)per stipply Iiiie. Witli the line s@N@itcli LS aiid the i vei-sin(, contactors RC 'e in their b; n ivhich. and LC ased po,@itions i tliev ai,e'sliowii, the i,(,silltlil(,, closLit-(,, of the 70 (,oit@icts (,ornpletes a liolclino- (-ii-eiiit for (]IC ol)ci,atiiio- of the i-elay tlit@(Ligli tli,(, coiit,,ict 24 aiicl the cotiti-ollorse,viiiei)t 25, tiid at the sitiiie ',iiii(, e-,tiblislies aii ein(,i,,-Yiz . ii)- eireiiit foi- the (-ontactoi- ITC 75 (,Xtelldin(@ fi-oni the iiii(Idlo stil)ply line tlii-oti@li tlic@ disconiiectiii(, savitcli, tl-io contact seginents 22 tincl 25, relav contact 26, the intei-locl@l'n,-- contact 27 on the lowe],ID(T coiitactoi, 1,C, interlocl@ino- coiitict 28 on so the lioistiii(, contactor I-TC, tlience, tlirougli the int(@i@locl@ing contlet 29 on the lille switeli LS and the ol)ei-atin(Y Avin@til)- of the con&, zn tactor TIC, to the conductoi- 24a whieb i,-, connected by the disconnecting swit(-Ii DS 85 to the Lipper gilpply line. The contactor I-IC .it once closes to m,-,ike connectioils for opei-atin(y the motor IO.in the hoistinclirection -Nvlieii tlie, line sivitch LS is closed. Aliolclin(,- eircilit for the operatin(y -,viiidin" of the cont@ictor HC is coiiipleted throLi(,Ii the interlocl@idcontact 30 -",bon tlie, contactor closes. At the same tin-ie qn enei,-izin- cii,etiit, for the operttinc, windiiig of the lire s-,Iiteb is esttblislied by the cont,,ict 28, the cii@ciiit exteiidin(T fi-om the iniddle slipply line, tbi-oii(rh the disconne,,ti-Qg switeli DS, the se(ri-ileiits 22 an(-l 25, relay contact 2C), tl)e lo-,-vei-in- contactor, interlockincr contact 27 the lioist,in2: c ontactoi,, 10( intei-I.o,-kiiig contict 28, the c@ol)(Ilictol, 31, tbenee t of the Iiiie Iii 6i-igli the iii-ndiii" s-%vi'@-ch an(I th(@ conductoi- 24,1 to the upper sul)ply line The restiltin-' closui-e of the I;nc switeb I C,5 dompletes the connectioli of tl)e motor 10 to the stil)l)ly lines 12 for ol)el-ation in the hoisting direction witli all of file re@istors RI, R2, R3, R4 in the seco@-idai,y eiretiit, the electroma-netic I)ral@e 13 beln,- i-eleased to iio tn permit the motor to operate at ii-iiniiiluiii speed. To tecelera'Le the motor 10, the conti-oller C is operited into position b to establigli qn' ener(liz,@n(, circuit -'Lor the operatid(r 115 win(lin- of-,--the tresistance controllincon-i,,ty be traced oiii the tactor wliieh ii fr ' niid(lie supply line through the (lisconnectin,, switeli, il)e se("nients 22, 25, the conti-ollel. C, i-eliy coiltact 26, auxiliai-y cont,,i(,t,, 120 27, 28 of the contactors LC, HC respectively, condii(-tor 31, conti,oller se(,'Mellts 32, 33 condii(,tot-. 34, the win(ll'ng of contictor 1.5. the aiixiliary contict 35. with whicli the resistance cont,,tctol. is pi-ovided, tlic, windiii- 12@) 36 of the current limit i-elay CLRI, thence 'throucph the conductor 24@l and tl-ie (lisconnectin- s-witch to tli(, iil)l)cr siipply line. l@ The re'sistane(@ of tli,,@ (-tii-rent limit relay ii7inding 36 is sucli that the energization of 130

1,708,887 3 the operating winding of cont,actor 15 is insuffleient to opei-ate the contactor to the closed position. Hoivever, the energization of winding 36 is sufficient to oper-,ite the arm 37 ouf of encrtiement with the pltinger cont-@ zn trolled by the winding 19 and operatively connecte(I with the contact 38 of the current limit relay. Conseqiiently, the conttet 38 is maintained in the 61)en I)osition as long lo as the enei-(,ization of winding 19 froiii the curi-ent ti-ansfornier 21 is above a predetermined value. After fhe motor 10 has accelerated to the inininitim speed and the current supplied to 1 5the n@otor throtigh the pi-imary of the ciirrent transforiiier 21 has decreased to the norn-ial operating value, the energizatioli of winding 19 is correspondin-ly reduced to a sufficient value to permit the contact 38 to 20 drop to the closed position. This short eircuits the winding 36 and thereby increases the energization of the operating windin(v of contactor 15 sufficient to operate the con'7-' tactor to the closed position and sliort eir25 ciiit the i-esistors R. It -%vill be seen tliai tl-ie auxiliary contact 35 completes a, holdirir eircuit for the operating windin(v of the contactor 15 which is entirely independent of the ciirrent limit relay CLRI. Upon the removal of the resistors Rl- f-rom the secondary of the motor 10 the latter aecelerates to a hi(,rher speed. If the controller noin, is operated into position c, tl-ie i-esistance cont-,Lctor 16 is energizecl thi-o-Lioll 35 the controller se(rment 39 ivitli the i-,,ind'ng t@ 1 40 of current limit relay -CLR2 in series tlie@ewith, the circuit incltidin- t-,he idterlockin-- contact 41 of resistance contactor 15. The el-irrent limit relay CLR2 functions to prevent response of the resistance contactor 16 tintil the motot clirrent decreases to the normal opei-ating value in ex,,letly the m .@ame ,inner as just described in conucetion with the cui-rent limit rel,,ty CLPv,'. Closure 45 of i-esistance cont,,Lctor 16 est@Lblishes a holdiiig (@ircuit for the olderatiincy winclin- thereof tliroucrh the atixiliat-y contact, 42 .ind tls6 2 to sbort circuits the resistors R furtber ae(,-elei-ate the motor 10. 1)0 Ul)on opei-,,ttion of the controller C into i)ositioii (1, for ftill spee(I noriiial hoistin(I I (Pel".Itioll of niotor 10, the resistance cont.ictor 17 is first closed iinder the control of the etiri-ent limit rel,,iy CLRI ivlien the motor @1) 5 ctiri@ent deere,,.ses to the proper valtie @,ti-id then the resistance contactor 18 is clo-,ed iinder the control of the current limit relay CLR 2 iii a sii-nilai- manner to successively sliort e'i-eiilt the resistors R3, R4 and tlierebv I)i-ing the iiiotoi- -iip to fi ill speed in th e lioistin,y dii-eetion. lioistin- oper,,ttioji of the lll()toi- is sto ped and the eleetroiii,.trp iietic I)r@uke 13 is i-e,,il)l)lied by i-ettti,nin(r the eojitroller C to the ofF posit' ion. Where the valtie of the overhatiling load driven by the motor 10 varies between wide limits, as where the motor is otei,ating a hoist where the load ma3 rom rated lo,,id to an ciilpty bucket, it is n6cessary tlltt c the inotor be al-iajicred iiot only to ol)erit 70 zn the@ licyht load in the loweriiig directioil, or ele@trically bi-ake a heavy load, but also to stop the aescoiit of the load in order to lesseii the (luty on tlic@ ele . ti-oma(,rnetic brake. Siiiec the alternatin(r ciii-i-lent di-iving motor 75 of the slip. riil,,, in(itiction type ilitistrated is cap@i ble of retarding the loa(l only when either the motor is drivell by the loa(l above synchr oiious speed or the power coniiections O-L the motor are reversed or " plu-'Yed " to 8o oppos e the drivin- tot-(Itie of the motor a-ainst the torque exerted by the descenclilil(@-id, the proper v,,tlue of the i-etardin g effeet of the motor obvious.ly ivill depend upon' the value of the overhaulii-i(r load. Flirther- 85 rnore, in order to facilitate j'ogging or di@opping the lioist biicket a relatively short distance, it is desirible that the operation of the motor to drive tlle bii"ket iii the lowei-ing (lirection s.tart at the lowest possible speed, f)o as otherwise the niotor may drive the hoisting drurn more rtpidly than the bucket falls where the acceleration 6f the bucket is retarded by the friction of giiide sheaves and other mechanical parts. Otherwise -,t sltck ()5 is introdiieed ii-ito the hoistin- rope which will prevent accui-acy in the control, as well as cause undesirabl-- ind dangei-ous whil)-' ping of the hoist ropes. With the control systeiii illtistrated in the (itawing, tlie.,,,e uii- loo desirable resiilts are avoided aii(I the descent of the load at all tiiiies is iidder icctii-,,ite confrol and the lowei@iii(,@ speed i,@ atitoinatically mtintained within safe limits. Tllc@ coilti-ol is on- 105 arran(,ed so that the niotoi- always is c ' nected initially to accelei-ate the loa(i in the downward direction at a sloi-,T rate pi-epai-at!l el tory to brtkin(@, the load by re,,tilative action O'L the motor to maiiitlin, tlle speed of the olerliaulin(,, descend@Iiig loa(l witliin saf@-, ii@j opei@atitig Iii-nits. Fii-ially th(-, I)ower (oniiections of the motor are reversed to retard the descent of the loa(l pi-lor to applyin- the electromagnetic brake to stop the loa(:!. The operation iii haii(Ilijig the descent of ii5 the ovei@haulinload is as folloivs: The controller C is operated fi,oii-i the off positioii througli successive loivei-ing poqitioii,, it, iiit( the position c. No conti-ol eirellits ai-e establislied in I)ositioiis 7i,, g. III POSitiOll C 120 i,n enei-(-Yizin(,r eire(itt for the operitin(r in!,), of the lowerin,,- cont,,ictor LC is establislied fi-om the iiii(l(lle siil)ply lirie the se(,ments 4,5 and 46, the auxiliary conta,t 47 of the reli@, the iiitei-lockiii(, coii- i 2:5 tact 30 of coiitacto,,- Ilk", the (@'ontict 48 of the lowerin," cont@-icto!,, flie aiixili-,Ili-y (-olltti(,t 49 of the line snvitch, theiiee thiou(rh the ol)ei-atinc@, %-vindiiig of the lowerilly coii@ta(@tor, n -1 tlle condtictor 24@, and the disconnectili(, 130

4 1,708,887 switch DS to i,lic iipper stipply line. Upon i-esponse of the lowei-in- contactor LC to (-onnect the iyiotor 10 foioperatin- in the IoNi-ei,iii(rdii-e(,tioii, a liolding eirciiit is esttbli.,@lic,(] bv coiitzi(@t 27 iiid an ciier(riziiig (!11.- (-ttit to tlie, wiiidiii(, of the Iiiie is by the (@oiitact 48, (,acli the 1.(@liy coiiti(-t@ 4i- iiid t lie iii(ei-lo(-],@ill(r (,olita(!t 30 of the liolstiiitr io (,oiit:i(,toi- I.IC,. It c@liould bc noted that t,icliltc@i-lo(@li-,iiig b(@tween the line conta(,-tor LS, ili@, lioi,,;tlii(,,- contictor I-IC, aiid the IoNvei,iii(r (oiitactc)t- 1,C effectively iii,,@iires a(,,,tiiist iinpi@(I)el. opei-ation in cise ani, coiitictor 1 5 sticks oi- " fi-eezes " closed. The Iiiie -w;tqli ,it once opei-ates to coinplete the lowei-in(,, .0 I)oii,ei.- coiiiiectioiis I' i- motor 10 ivith all of tlle I,CS'Stol@,. I Itl@ It'-" R:I, rt4 connected in tlte sc@('011(iiii-@, ei,@-Cilit of tll(l niotor to stat-t op20 et-,itioii tliei,eof at -i-iiniinijm speect. In t,li(I loivel-iii(,- i)ositioii c, the i-esistan(,e controlling coiit,ic',oi-s ii,e niaiiitaiiied deenei-gize(I as loii(r Ls tli(, iiiotor 10 operates -at the iiiiniiiiiiiii IToivever, in c@ase the load, 2,'-) Ii@tel' tlie, i-eleise of the electroiiiagiietic bi-,tke, sliotil(I teiid to ovei-liaitl the inotor ;iii(I di-ive the ,ai-ne above syiiclii-onoiis sl)ee(l, the i-etii@din(, action of the motoiwitli 'tit of tlle resistoi-s RI', R2, R'@l, R-1 in tlle see30 oiidii-y cii-(-u;t is sli,yht. The iiiaxjiltim retai-(:Iiiioeffect is obtt,ined only wben all. of the secoii('tai@y resistors ai-c shoi-t -eii-ctiited. Ileiiee, in oi-dei- to pi-eveiit the oveiliiiilin(r lo:i(i fi-oni (lt-lviii@, the motor 10 at (@x(,essii,e :35 the centrifti-,,i,l switeli-14 i,,, ai@i,an-ed to close wlieti the iiiotor 4peo(l exceeds the s.yii(-Iii-onoiis vilue. ITp(l, 111(@ closllrc of the speo(I-rc@sl)onsive 14 theresi-@tance coiitactor 15 is ener40 ('iZ(,'(l tIll.oll(,.Ii a circuit includin(@ the seg4,,), 46, t,he contact of tlle, speed-respon,@ive swit(-Ii 14, the windii)g of contactor 15, l I t, ilic, atix'l';ti@v cojitact 3r), tl)e ivindin(y 36 of 'ji' it i-el@ty CLR', ,ts well as the tllc clii-i.(@lit ii-i ,1,5 -,on(iii(.-toi- 24,1. The clostire of the resistance coiit,ictor 15 is controlle(I by the cuirent Iiiiiit i-elav iii siibstantially the same maiiner as I-)i-o;,ioii,@ly clescribed. The current limit rel,i), ivi-n(lin(@- 19 is ener(,ized from the etirreiit 21 in order to prevent too i@al)i(I ,tcc,c@le,i-atioii- of tlle overliauling load in the loivering direction, After tl)e coiitactoi- 15 closes the closiire of tll(, reiiiiiniii,, xesistance 16, 17, 18 follows in - sequen( I e i@in(li(@i, tlic, iltei-iiite (@oiiti-ol of the ciirrent, IiiiiiiCLI-1,2 'III(] CLRI iii @l to tli,,It I)I-CN7ioi.isly desr.,i-ib(-,d as the cii-ciiit for the i-emaining contactors are e.,@t,il)lislied tlti-oti(ril cotiditetor 34 and the @;(,@,ytiients @')O, 51@ 52 iespectivetv. In this ii-@tv t-,11(" speecl[-i@esl)onsiire @ivitch 14 serves to ,Ilt@oill'itic,ill -onti-ol the i-esistance contactol-s @') I,,, to @I)ort eireiiit the secondary resistaii(-,o of tilic motor ivlien the inotor speed 65 ex,-e(,(I,, tli(-, s37iiebioiious value ivliile the motor is opei-atid- oil the initi,,Il lowerin@,r T)oint e. With the secondai-y r--sistor slaort cii.,cuited the ieta,i@diiif- action of the inotor at supersyiiebi-oiioiis spee(I is inei-eased siifficient'ty to 1)1..evoiit the load from driving the inotor at 70 iii 01' (Iin(,erotis spe6d. In ca,@(@ the lo@i(i slaotild riot oi,ei-liaiil tlioiiiotoioi- flie power connections for operatin(r the motoi- tit low speed ii-i the lowei-in(, (Iii-e(,tioii ai,e not continued foi@ a sttffieieiit time to I)ei-i-nit tli(, oN,erha-,iliii" load to drive the inotoiabove s.),iieliroiiotis sl)eed, tlio spee(I-i-esl)oiisive device 14 Nvlll Dot opei-ate to i-einon-c t-lie resistaiice fi-oiti thesei2on(lary cli-eiiit of the niotor. TJiider these condi- so tion.,4, (.@oiiti-ollor C inav be operated into tlle exti-(,iiie position f ir@ oi@dei- to coil-iplete t cii-eiiit iii sliiint %vitli the contacts of the @,pee(I-i-esl)onsive device 14 tlirouffh the coiiti-ollei- s(@(riuents 53 and 50. Thus, in posi- 85 tion f the controller establishes cii-eti'lts tlii-otil(rli wllich all of the resistance contact-oi-s 15, 16, 17, 18 ai-e enei,(Pize(i to close iinder the iltei-nate conti,ol of tile ciii-i-eiit limit i-elavs CT,RL incl CLR2, aiid tliet,ebv ol)ej.-,,ite 90 the iiiotoi- 10 at iiiaxiiniiiii sl)eed in the loin,- ei-in(r (Iii@ection Nvitli all of the secondarv re@7, sistoi@s short cii,eiiited. If, no-,i,, it slioiild be clesli-ed to tl)e dec;ceiit of the load the controller C is re- ')5 t(irned to position e and the conti-ol zi,i-ran(re,- inent is siieli that the resistors ,Li-e reiiiserte(I in the 'secondai-y cii-ciiit of the, motor in(I the I)ower connections of the motor are reversed to ol2pose the toi@qtie of the motor to I(O the toi;qtie of the ovel@li,iiilin- load. This is t-I dtic to the fact that iii I)OSition @ the relay R is enei--ized tlii,oi](111 the eircitit extendiiifroiii the middle powei- condtictor tbroii,@li the conti-oller set@ments 45 and 54, the wind- 105 ing of relay R, tbence throii(rh the condtictoi- 24a to the iipper supply Iiiie. Tlle openin(r of tlle relay contact 47 doe-, not interi.-ti@pt the energizin- circii e-I it for the ol-)cj,atiii(y wincling of tlle lo@-,,el-iii(r contactor 1,C cqn(i the lin@ snviteli LS cliie to tl-ie fact that the contact 47 is shunted by the eireiiit exten(lin(, tliroii(rh t,lic coiiti-oller se-ii-ieiit 55. 117lien the co-'nti,oller is returiiecl to position e, a holcliii(r eireiiit foi- the operating ivin(Iiii(- of 115 the i,elay R is coinl)leted tlirou(,,Ii the (@oiiti@oller serfia-lents 56 and the contact 24 of th(,, relay. At the same -time, the retul-n of the conti-oller C to the position e intei-rtipts the onei-(,izin- eireiiit for the loii,ei,ing contactor I"( T,C aiid the line switeli LS clu(,, to tli(,, fact that the shunt cii-eiiit arou-nd the relay contact 47 thi-oijgh the controller se-iiieiit 55 is brokeii. This resiilts in the openin(r of tli(, lo-@vei@ing contaotor and also the line sivitell. 12,-, Tlieretij)on the opoi-,itiji(r windinc, of tlie, lioistin(r contactor HC i,,@ enoi,(,izecl tliroii(-,Il the cii-eiiit exten(lin- tili@oti-li the nil(](Ile t-I t-I siipply Iiiie, the controllei,, se@rin(,nt,,4 45 ail(] 56, relay @ontact 26, ivith the relay in the

1,708,887 energizea positio.n, the contaet 27 with the loweriiig coritact in the open @6sition, the contact 28 with the lioisting contactor in the OP@n position, the contact 29 with the line switeli in tl-.e open positioii, tlience throu(,!Ii the operating wiiidiii- of the hoisting @ontactor 'and the conductor 24a, to,ilie upper su ply line. The li istiiig coiitactor iniiiied,,@ "i es the operatin(r tte,y closes an(I ener(, z tn 10 wndn(r Of the @Iiiie sii@itch in tlil, manner p@,eviously doseribed ,i:iicl tipon closure of the latter tlic, i-notor 10 is coiinected to the sup'ply line 12 to oppose the a(@ti-@e torqtte of the iiiotoi-, witb tli(@ resistors R', R2, U3, P,4, 1,5 in s(@con(lary eirettit,' to tlie@, tor(liie of thedeseeiiding load. With the motor driveii by@ tlic@ load at a speed well above the syn clironotis valtie, the torque of the inotor'with all of the i-esistors in secondary circuit is of suf - 20 ficient vallie to predoininate over the torqiie of the load.- Coiisequently, tlie speed of descent of tlle load is decreased. As the speed deci-eases coiitroller C, is operated into position g to estiblish an eiier-izin(, cii,cuit t, t5 25 tlil-ough the sec),lneiit 53a of the operating Nvindiii- of iesistor contactor 15. The latter closes under tlig, control of the etirrent liniit relay CLRI and removes the resistor RI fi-oiii the secondtry eireiilt of the iiiotor 30 the@eby inereaslii,,,, the vtllie of tlle torque exei-tect by the rnotor at the reduced speed thereof. The speed of tli6 descending load is Itirther decreased. In orde@ to slop tiie load controllet C is 35 returiie(I to the positi,on 76 iii whicli the resistor contactor 16 is energized throligh a circuit establislied by the coiitroller se(- ment 51-1 and ftinctions to i-eiiiove the resistors R2 from the seconclary eircuit. of the liiotor. 40 Preferably, the i-esistors are so proportion6d that the remaining resistors R3, l@l, in the secondary circuit of the niotor cause the motor to exert a iriaxiiaaulii op@osing torqtie to the load as the speed of the deseendino@5 load and, consequently the motor speed, approaches zero. As the iiiaxiiiitirn opposing torque of the motor bi-ings the desecndiiig load to res'c. the controller C is iiiovecl to the off posil@-ion, thus deenei-(Ylzliig the liolst50 ing contactor HC and the line switch LS to interrupt the inotor eireti't and set the eleetrom@),o-notic bral@e 13. From the, T-oregoing it -v@,,Ill be seeii that a control system embo(lyin(r my ilivention per5.5 mits the iiiotor to drive the load iii botli the hoistin(y and the loiverin(y direction, and also insures aiitomitically that the niotor is iiot' driven at an excessive speed by an overhtuling descencling load. Furthei-moro, the con60 trol arran(yen-ient permits tlie. torque of the motor to be opposed to the torque of the descending load and to be suitably i,,q,i,ied to brin@ the load to rest from any operating spee 65 wiiat I claini as neiv and desire to secure by