* Pree oe nor Peete er taal ST od ested 3 era tes Cag era APE ISS ATEAES pre eT EY re Pease teet My heer PTR a UBRARY Michigan State University PLACE IN RETURN BOX to remove this checkout from your record. TO AVOID FINES return on or before date due. MAY BE RECALLED with earlier due date if requested. DATE DUE DATE DUE DATE DUE 6/01 c/CIRC/DateDue.p65-p. 15 woe cnadlysis of Lesctrie.l nhenome:s: Pegia Lubtc~ttved to tha SO. culty of AIT TP oc : “arm ‘oT “AV. "eye 4 LO? VB o.ts .G2tad dade... j OD 4 ale oi Je ‘(Wes Es) lie ve LWADe ‘le de .ULPtZe 5 se a, « ca a8 foley yt qa aD eS NGLuG&btes LOY whe oisree Of ~ono2Lor Oxf . GL3MSGCe NANG 9 LY oL e HESS [37 25 TH> Introduction Inthe classroom we heve Studied gertuin theoretical and Mmathematic.il aspects of electsicsul phenomenize It is the furvose of this tresis to illustrate in eae more tucgible Mannsr the Sine unenomena by oscillogruns, suoplemeated With omulyses ard exmluinations. shis tyse of analysis is of importcence bescuss it .fforis 2 physic .1sconee tion of Wwiset oceurs in « phenome ena, wrioh oveurrexce would other. + ie vet lowsht of ond overlooxed. 713 method is more interesting nd nore cortein in , “* wee - ro . .* / _ ww * - _ 7” trad oF tealysis and umntrenstlicnl n~- its results ther tk ny 4 » Eoiution.e It is more interestines tion the m.therutiecal solution for one is vorking with concoreto things, cond it is more certain in its resuits bee.use it rictures whet actuully tu.kes plsc?, whergas «ut the completion of a inctbremaetic.L solution one has «& result which my not precessurily exoclain tre intrieusies .v hinde -@ hove teken oscillocre:s of tricnslent shenomer.: in circuits of knowa in order to vwarify the analytic. 1 and muthenstiecsl anezlysise 2 have taxzen curves of flux distribution in vzrious maciines in tus iaborutory in orser to esuiy the voltese veves with the vossibility of correctin: undésirable h: rnonicgBe In the workinz out of tris thesis we ive encountered many interesting problems und while they my not be entirely new, tueir epplic. tion ic, nevertnsiess, imrortact. 104040 iiborutory ypurutus e ihe upp.ratus with which the osciliopriu:is were tuken wuS Of the leoture taole type of bucdell ‘soillogrzph with wniceh the were w.3 thrown fron « revolvins mirror onto a soreen, out this &.@ benn trznnsforned by vessers ycokoff and tie.sley into a photorr. phic outfit in which the ray of fignt wae thrown Yron the vioreting nirror uirectly vpon ze rotating drum curryine motion pictursy file « slottad shutter duiliins unesr the ection of cruivity aiLoweda Lignt to nass fro: the are laeup to tne vibratins wirrors for only the short invervel of tise (epppenin.tels One-tenoun secon'p th:t it took the vevoelvines drum to rotwte only o2uve, so th:t the pictura woule not be repe.bec.e, ind Shutter , which wes Of Sheoteiron, bes ea rubber ourper ut the ootbou, anu at Lirst aitficulty wos encovutered Pron tne snoubcor rebounsins cnu pussice Licht 9 the iiis. fur tha cecoiu tine, eit cy proper -2;cstecent tric Wat O11: in tere s3 our osecillogreaus vere ior the si0st pert to bs of tho traohbsSient phononen. in wich ¢@ Wandte. a continuous pleture fron the beginuing to the om of tra Jil, it weS necesvary to ars Vine picture SGeart ut one chu. OF tue Tass: Or next vo «here jb Wak Vedee@u in the emu. vodoen © rrieu the PLiln. oo by pans OF ae PObvetine Gorvrocy co: ie CUucO. OF Lhe drum spindle evd orm gpnetie trip for tice oruiter, the enubryer vis otarted ou ibs £13 abt tlie bene tise that the en. of tre Tibi passed : ot ses } se foo CUReh ba we DON» Lhe Obst de. Se Yrunsient Phenomens.e on electric system through which energy flows has , at u. Gertant point,a potential e and current i. If the conditions of the circuit are changed, the potential ond currebt at the poit under consideration will notlonger be e and i, but will assume new Vultes after the system has reached its new position of .e.uilibrium. ‘lthough the chenge which disturbes the ecuilibriun of the circuit may be instanteous, . definite length of time is required, by the wvates to adjust itself to the new conditions. If, therefore, these new conditions re uire that at tne point under consideration the voltxge be 9] au: the currant i, , these Velues are not obtiined at the instant the chinge is inde, but after sone time h:s elapsed. uring this tine the voltage und current asumme transitory values, wi.ich start from e and i Loni end with ejand ij e These transitory values of the voltage aif current can be divided into two components. ne comoonent is a, and iy, thut is to suy, the Zinal, falues required by the now edmditions, and wndeh oamad net be reached ins tambendous]y, . ‘he second con- ponent constitutes the transient terminal voltage and current. “or instance, if we upply to an incuctive circuit suddenly a constiot electrbuotive force, the ourrent grows from zero to its fin:1 value , i « ccording to figure one. "ihe tr-nsient" in this case is the current i, shown in figure one. .he presence of tr:nsiont phens enue, when u systen passes fro: on position of esuilibriun to sunotner, is not a psculisarit; of the elevcuvris system, but ovcures in other for:s of ener:y. {In an electric syste: energy is penerally formed in two forms, eleotron.-netic ani electrost:tic. .he electrom.gnetic ce*. ¢nis te energy is 14k .nd the electrost:tiso energy is m@ans th.t when e uni i ura chungod the energy sbored in the s;ste -: ust ulso chungee Such chunse of stored energy can not huppen instuntuneously, because an instantaneously chunge of stored energy necessitates infinite supply of power. A definite length of time is then necessary to bring xbout the variations in the Stored energyes. ence the transient. oinee the static enersy Gun be stored up in two different rorus, the electric traunsieuts can be of two kinds, single- energy transients and double enerry transients. na single energy trinsient only one form of energy is variec, und a sinrie energy transient therefore, consists bnly in the increuse or decrease of one form of enerry.e. ihe trunsient shown in fig l. . is u Single energy transient, beceuse in that case the mur7netic enervy of the circuit wus chunged from zero to ‘1% and the citcuit was ussumed to have zero cupu.city, therefore no electro- static energy wus stored up in ite Double energy trunsients consis in u variation of both forms of energy, or in a transformation from one form of energy into the other. she transient which truns- forms energy from electro:ugnetic into electrostatic, or vice vers., it is un oscill:.tion. -urinus this process, hovever, enersy Losces oveur it the circuit Or uround the cirouit, so that fenerelly the origisel anount of enesr«y of the oscillution decreases und disuppears. In u pure oscillition, e. i, where no losses occur, at « certain insteunt all the energy is electroenursnetic und equal to 2.48, i; Little luter «li the energy is electro-stutic ani equal to ive”. ince the cirouit does not dissipate energy, }ui% is ejual to iCe2, und therefore = iV, of is in the nature of -n impedunce, because multiplied by a current, it givea a volti.ce. qs 4 Gilled"the nuturul impedance of u oirouit”. this natural impedance is of great impobstance in the study of trunsient phen- Oonenie .0 far uS we know thut it represents the ratio between t:ie volti:re und the current of the oscillation. ihe freyuencpy, ff, ut which the energy is transformed fron me.onetio to electric, und vice vers:, is 1 » when both the inducterce L and the capactty © ure concentrated. “his meuns that during the time 2fVLC a complete cycle of the oscill:tion occurs. 0 thit, if ve start at the instant when the voltuge is m.ximum und the currnet zero, the voltare wili uguin be maxinun und in the g:me direction und the current will .giin be zero. ufter . tine 2ypuc. Jcince the electroemiurnetic energy i8 equal to nae the chinge in this energy in a smull intervul of time at will be a(,bi*), or de,,~.idi.e -ikewise for the electro-siatio energy, the Ch:nce de, = Cede, if the current does dissip:xte energy, 283 ull cirouits ao, the energy last us heat is equil to i°..6 Se -e —-- 6. Iv the convensSer 15 Guarged, and the energy is stored us elecbroest.tic energy, and tnen the condenser is discharged Guru VAS Pesibvance and inductszuce, the cuer py is trarsformed AutO neat eucresy aod electro-nurnetic ener ye Lherefore, in tne interval of time dt, Cede Sidi pivHét =06 vincge tha current i is equal to the quiiutity of electricity . dq sot in notion in the time dt, we hsve i= end Siice aq =Ce we Auve dq =Cae era - Cde aria. 1 =f =— ~at ~ at co t2t finelly the equation may ba written 3 + ude —:) L@utling a equal a, sis /ousavioa bagoues e(e* + =~ ja 3) = » the colmae : . oe R= 1 _. If the valves of 4 gre real, tnat 18, if Ble ~ Ta =? or KR“) < =, the equations of e and i are not periodic functions of time. wut is tre velues of 4 are inapinary, i.3e, if R*( 45, the equations of e and i are periodic and exponential Functions of time, and are therefore damped oscillations of frequency and decrement, the expregsions of which are: Pec; 1\/ 2 3 Frequency or Tce Logeritnmic decrement e » & 4fL lf, hovever, nee <= the ecuation is just not seriocic, or Gritically dirced, and it the cirerit oontsins constants of these relztive Viiues, upon disc ureving the cordenser, the current reecies & 1: uxillm Value in one cirection ent then cecrys Te to zero witnout reversing direction. ino condenser in discherring uses up its evergy in heat Less «nd in building up the magnetic field. .t toe time thet tie current reacnes « Ruximum tio nesmetic Pieid ia «ct ite nenwcun, and the condenser voltsps is zero. The current tisn continics in the Sai.e direotion due to the collapse of the szgentic field, ana the energy stored up in this ficld is totally consumed as heat onerpfy. Yasrefores there is no energy left to ociores the conionsor; gousequently no reversal of currente os Ute 45 @ wevitication of thie alelytieaL oliu sovnematsorl t4: agnivnia, we have sat up series Clrenitys of known gonstarts, anid taoea py moans of the osecillosvrana, iuve revoricd the tronsient in eae” chic > te PROSa CLrsuitS "480 acvanezeu LM biuree@ E2iGbe UNE O01 Conetart resiste:d2 and e@nowgity, and ul Vabrrisng 2duclbarGe; batO? Qid Locietecce, wii vi Vurlaevle another of eonste:t resis 1.3 _ eencecity; and the third, of Go.stand Loo Gees Uc Uupucity, end of Verinble resistaceee, inclvwded iz: tae Lesw Gov Was é- ty > 8 4 + - yg A 1 tg Circuit in wiiehn R wes of Sven valve taat Ke ae, Ward. Gilg theoreticelly, is the critical gaure The following are the oscwellograms of the first set, in which the inductance wes changed while the capaeity and resistence wers kept constuntse Jelov exch priat is given the dats for thus evrve, Showirm: the constants thet were in tne sircuit and tne results, bot. computed snd measurede At tne end of the set is siven = Gurve showixg how the frequency 2nd decrene2nt vary with a cnange in indauctancee All oseilloggams show a 60-cycle timimg wave. : Pires Be R 14.2 onms. CG 96)90 god 3 Py 35 farais. tT 02096 ® 24. henrys e Sonputed S21 Computed 04.1126 Frequency Decremant Measured 5°23 heasured 06125 - Fig. Be R 14e2 ohms. CG 0.009 »~0135 ,35 faradSe jy 020435 henrySe Computed 203.45 Computed 02457 Hrequency Decrement Measured 211.9 Measured 02456 = De Ohms. G Computed Fre :uency veasured Fige 4. 0.090,013,35 furads. L Qel274 henryse 121.26 Computed 04.632 121.0 Measured 0.684 CGouputed frequency i8aS3ursa R 14.2 ohms. C Computed frequency Measured 0.000,013,55 farads. LD QOe227 henryse 915 vomputsdi Oe710 Decrement 91.0 Ne 0.701 we 4L3Uure” BP bh i. <4 e 6 © 0.000 ,013,55 faradse i Oe4il henryse 67 07 34 Computed O.775 65400 Measured O6.631 10. Fige Te R 14.62 ohms. C 0.000,015,55 fureds. LeO1l henrys. vomputed 45,28 Computed Ow 850 Frequency Dec. enenti measured 44000 Measured Oe«70) Site Be R 146c¢ ohms. G 0.050,015,55 farsds. &L 1,574 henryse Conuoubed 54665 Sonpused 04.873 Fre yuency vecrenent Measured 308 Heasurai 0.831 It appears tnat tne computes .nd meusured values do not check very closely is some gases, but this is due to the f.ict that it is very hard +) n22Ssura agourutely tha deprenent when the amplitude is small, and tne pr sence of the small vibrations makes the mevusnurenent of tas Prequeuoy a difficult iatiere Nowever, tna measured and corputed values are neur enoush to verify toe luvs es cot forth 14 the explanatory subject mattere ee a») DU Artgenes snsseneet -sheccetP . Eseasses © ssntaes © esetaee | -INDUC TANCE IN HENWRYS Biged This curve shows the vari.tion of the frequency and ¢ decrement of the oscillatory dischsrze ourrent in oeirecvits containing resistance, capacity, anu iuductaence in series, When the bosistance and capacity ure kept constané, und the inductzace is varisd. Following is tho seaond set of oscillograms, in which the cupacity was chanced while the resistance and induct nee ward kept sconstunt. 12. Figs 106 R 14.2 ohms. C Q.000,013,355 faruds. L 0.0455 henryse Comouted 208245 Computer 00457 Fre ,ueney vecren6ut Measured 211.9 Measured 02456 Dig. ike R 14,2 onts, C Q0.00.,015,39 farzis. Lb 0.0435 henrySe Computed 1:37.23 Conrouted 0.4173 Frequency Decrement wecsured 192.0 Measured 046 Pige 12. R 14.2 obms. C Q.6000,017,46 farads. L 0.0435 henryse Conputed 150,59 vomputed Qe«40b Frequency Doeoremarnt heasure. 180.00 Measured 04385 MIU WU SOCOSS DOCa aa Pige 13. R 14.2 ohms. C 0.000,020.652 farads. L 0.0435 henrys. Computed 166.63 Computed 0.375 Frequency Decrement lieasured 170.00 Measured 0.353 I ahs ten, Th Ph rn) A Ven na NEN lanes vataer etre te ttt ereeet Tee ye Stee tere te et eee nereeys Be ake Go VV A NAV VUNAAANA AAS AAA SANA ant Fige 14. R 14.2 ohms. C 0.000,023,715 farads. L 0.0435 henrys. Computed 154.42 Computed 0.547 Pre juency Decrement Measured 154.1 Measured 0.575 Fige 15. R 16.2 ohms. C 0,.000,026,772 furads. lL 0.04455 henrys. Computed 145.0 Computed 0.525 Frequency Decrement Measured 168.1 Measured 0.515 Fige 16.6 these curves show the variation of the frequency and decrement of the oscillatory discharge current in circuits containing resistance, inductance, and capacity in serics, when the resistance and inductance are kept constant and the Capacity is varied. e Following is the third set of oscillograms, in which the resistance was changed while tne inductance and capucity were kept constunte Fige 17. R 14e2 ohns. C 0.0 .0,013,55 farads. L 0.0455 henrys, Computed 208445 Computed 0.457 Frequensy becrement Measured 21149 Measured 0.456 Fige 18. R 20 ohms. C Q.000,013,35 farads. L 0.0435 henrys. Computed 20542 Computed 0.327 Fre juency Decrenent Measured 203.0. iMeasured 02325 Fige 19. 2 60 ohms. C Q,.000,0135,35 farads. L 6.0435 henryse Computed 2877.5 Computed 0.0206 Frequency Decrement Measured 175.0 Measured ? (very small) Lée Fige 20. R 114 ohns. C 0.090,013,35 farads. L 0.0445 henryse his oscillogram represents the critical case where 2 41, R “Ge Since the inductance and capacity were constant for this set of osciliograms, 2 wus computed from the equation just given, and the computed resistance was placed in the circuit. Theoretically, this was the critical case, and the oscillogram verified this. ee a7 >a ZA ie} bigve al Saows un: variution o¢ bo CeO gurney «0a d2crenent or ti.2 OSell wctorf dissciir-e current in eireuits cont.inins resict nee, i:cusct nee, .rd epee ty in series, when the inductence .1a @ pueity are cept constunt, una tre roesist.nee is viurie..« .he curve coes not ineluce tse critical cuse, for unuer that concition, there is no frejvuency, sinc: there is sourrent in one direction only. it Seem: « nurent from these gurves th:.t if the resist. nce in such a4 cireuit “ere zero, there would be a definite fre. venecy, «nd the decrement “ould be unitye in other “ordas, tre current wouli oseil.ute bucsr 4 forth in the circuit «at « definite rue, with no decre.se in strength from cyuele to cycle. it is i possible, nowever, to obiuind such a circuit, for uny Circuit weutever nas sore resiviince and the [2 Losses must be supplied. In the ocoili:tory disch.rg3s, these were Supelied oy tno initicl charce of clectro-statie enerrsy in tn» condenser, uc:d in the cribic.l cuse, this churfs wes expences durins tre Pirst flow of current in one direction. o2::8 ulso explains tre possibility of sniinteinine an altern:tins current from x direct current source by supplying, duriig .ltern ite hilf-cyeles, enou-h energy fron toe direct current seurce io ° Overcono the Iv Losses curine vne.t ayeleae 13. Ye Sinidanoutel principle upon wnisch the present day electric gererator is beset is that in a conducter euttine magnetic lines of force, =n @emefe is induced which is orooortional at every instant to the rate at which these LLNOS ere Gat &8 exeresseecd vy the equation e= of. Dre +9 the ineroeset hysteresis end eddy current losses An treuSTornerg, Tenere.lIrs, wat Odi eloetrical avperetus at ineressec frequencias, tue voleuro adulicd to this class of annaratus snowld ve free From userwonics, via Lusrofore te. sim in che desien of pre: erebors 15 LO roduc: a pure Slug wivo of vertineL volt ree In tne aiuwlysis of Yiux discribvtion aloos ve. ecrGastorpe ohel ota taru whieh the Qo Gtors move, bh) 5 COi.a Vint Gere ure variations li. pha four Gdensitye ( iue to this «ave form, a voltage induced by « periodis flux \ nas a frequency double that of tne flux, as seen from the @jvation, e oe e As a tooth emerges from a pole-rersion, there is 2 Vari.tion in tne reluctance tetivvesn tne pole and the tooth, and conse :uently, a chunse in the flux. some of tne flux which at one instant passes tapougnhn « certain tooth will, a& the tooth proceeds, Snuo back to the suceeedins tooth, outting ucross the inductor in the intervenins slot. ie have seen thit the flux wave is flat at the points of meximum and mininun reluctancé, and therefore the flux snaprnins across the slot will be of this form, ard henoe the volt:.ge induced has a frequency double that of the flux, or double the number of teeth. There is fringing of tne flux in tne space between the poles, and the sune double-frequency voltages indueed in this region, edaed to the inertia of tne occillogr: ph ribbbn, INaintuins the amplitude of the vibration as shovnm on the oscillogram for this regione there are 16 cycles of the lower frequency harmonic, end 16 cycles of the higher frequency harmonic, in each cycle of the main wave, or eight cycles of each &urmonic per pole. Sight cycles of the hirher frequency harmonic represent 4 teeth, and eight cycles of the lower harmonic represent 8 teeth, or a totsl of 12 teeth per pole, which is exactly the number of teeth per pole bn the machine from which the oscillogrem was tasen, the sachire beins 6-pole, snd having 72 teeth. It can be ssen from Fige 22 thet tho flux is the stronge- est at the center of the pole, but this represents no-lo d conditions. ‘inen « losd is epplied to the machi-e, either mechanica: loxd when used as a motor, or electricel load when used aS a generi.tor, there is a certain amount of cross- nagnetization and demarsnetiz.tion which distorts the field- flux, « @ weakens ite If the machine is pperating as « motor, the flux is crowded to the leading pole-tip, and for a sener:.tor, toe Plux is crowded to the trailing pole-tip. Fige 256 fhis oseillogram shows evidence of distortion as it can be seen that the lower frequency harmonics are longer on one side of the pole thin the other, ad the aovble frequency harmonics show up due to the fuct that there is a change in fluxedernsity between.tne two sides of the pole-fxace. Below is a seb of oscillogrems showing the distortion effects of different loads on the flux distribution of 2 2300~- volt alicrnstor, with constint source of excitatione RD WW a a ‘a aT Tr oO; i ig e ov6 Forty ampere, unity power factor, load. Excitation unchungede Sixty empere, unity power factor load. ixcitation unchanged. or aOe BFige B76 Kkighty ampere, unity power factor load. Excitation unchanged. It is seen that as te los.4 incroaasos, the voltere is decreased as shown by the emplitude of the main wave, snd tre flux is distorted, as shown by the shave of the main wive, and tha lover end hirher fre werey h-rronicse Following is © similsr set of oscilloerems taken from a rotary convertore It esn be Secon from the oscillorcrems that the flux is crowled to one tin of the role due to the fact that the eire-gan is narrower on that side, and when a load is c--.ied, the flux is shifted ot the center of the pole d3 shown by ficures 20 end 21. ‘The hicher freauency harmonic, however, is poreser:t because no matter how the pole-fuce end teeth are oroportioned, fringing czn not he prevented. PLife 25e Separately excited as ceneratore Fait . . ru on ” ‘ Pi 7 9 Be Saye aie Fige 296 Running idle as direct current motor. Fige 306 Running as direct current motor, drawing 15 amperes. Fig. 3l. Rumning ss direct current motor, drawing 20 ampereSe The harmonics as shown in figure 29 and are not present in> figure 28 are due to the effects of the armature current; there being no current flowing when figure 28 was takene Miscellansous Transients AS an auxiliary study a few simple phenomena have been investigated. The ordinary door=bell is a common-place thing but the flow of current thru it it interesting. It consists of coils wound on an iron core and an armature which completes the magnetic circuit, and whieh carries the vibrating clapper and a circuiteinterrupting device. When the circuit is closed thru a direct current source the current starts to flow, but due to the inductance of the coils wound upon the iron core, it does not reach its maximun value at once but increases gradually, building up the flux in the iron core ai the same time. Soon after the current reaches its maximum value the arvature is drawn by the magnets, svurikine the bell and interrupting the electrical circuit. Iz it were not for the inductance of the coils the current would cease instantly, but the inductance tends to projong the current and an are is established across the breaker points for a very small but a measureable length of time. after tuo circuit is brocen the coils lose their magnetism and the elarper flies back to its original position, egain closing the electrigsul circuit and the cycle i8 repeatede Pice See Ge Figure 32 shows the current thro gh an ordinary doore bell. ‘ime is toward the right. It is evident that the growth of the ourrent is gradual, arriving at a constant maximum veluee ‘hen the circuit is broken and the ourrent drops to zero, ‘The high frequency harmonic shown on the oscillogram is due to the natural vibration of the oscillograpR ribbon, as is seen from the fact that it continually decreases in amplitudes Fige 55-6 The above oscillogram siows the current through the same door-bell with a condense#® connecte’ across the breaker roints. The building up cf the current is very similar to thet shown in figure 32, but when the current is broken, instead of an are resulting from the energy stored in the coil, this energy is absorbed by the condensers The stored energy in the condenser causes a reverse current to flow through the inductance, resistance, and the counter emf. of the source, the combined impedence of which brings the current to sero. fhe absenee of ripples is due to the fact that there is no abrupt chance in eurrent value and hence the oscillograph ribbons have no tendency to vibratee wi @ Anotner Gom .rasively simnie piece of a.nsaratus wnich is used in the electrical industry is the magnetic circuit- breaker. It is connected inssries with the live, and its puroose is to protect apparatus by allowing only a certain amount of current to flow. It consists of one or more series turns of wire s0 interlinked with the magnetic ourcuit that the armature will operate ut different values of flux density corresponding bo different values of currente The armature has a time lag depending on the air-gap, being greater for s creater air-g: pe ‘nere is also a time element connected with th openines cf the circuitebreecker contacts which is due to the inertia of the moving perts, Far a short inter- val of time efter the circuit sterts to open, there is an »reo Maintained until t e resistence of this gap becomes s0 gre::t that the current ceases to flow. wuring this intervel the current dies down from its m-ximum valve to zeroe It was the purrose of this investirution to messure the time element of a circuit-breaker in the lstoratory.e ihe Gid’cuit was erranged so thet when the shutter of the oscillogre::h opened, u relay olosed t:e Girouit through tue eircuit-brenker and throu:n tho load whigéh drew enough current to trip the circuit-breaker. Pige Ba. eet for 25 amperes, 120 Ve deGe Supplye his é#etl Loreen represents the current from the time the relay closed until after the current ceased, due to the opening of the circnuit-breaker. The high frequency harmonics is due to ribbon vibration caused by the large initial deflection. From A to B the flux is built up nnd the armature is drawn up Glosing the magnetic circuit end releasins the circuitebreakere From B to C represeats the deesy of current from the time the circuit-breaker opens until the are is extinguishede From the sixty cycle timing wave it is seen that it takes about oneetwent;fourtn of a second. Wice Bde Same circuit-breaker, same setting, 220 Ve GeGe Supplye From this cseillogram it is evident that there was more current flowing because the initial deflection wes “wut @ greuter 2.d the tine of biildins us tie fiux les., us snown by the distance iB. It is als) evident tuat it taxes lonrer to extinguish the arc as snown by the distance 20; this hbeing due to the nishner volt:::e. But the total tine taken for the breaker to open is pr:otically the same for both casese There are many other interesting studies whieh could bea made by means of the oscillorra:h, but which, duo to Licurcieient time, were unacle to he incluaed in this reporte It would be worth while, 1° conection with rotating Muvshinery, to teke oscilloprwams of tne Simultaneous ourrents ie tne field, era in the armature, of eitner u direct or en alternating mucnins durins snort-circuite It would also we justructive in this connection to record the change of field fu.ux by windins a few turns of wire around the pole aiid eiuectia: its terminals to one ritoon of the oseillogrevnh, to rojle taza other ricvon could ve connected go as to record the —_ so Ure-vizcuit current, or the field current, Synenronous motors, while hunting, would afford znother sourcge ov” studye wome synchronous motors ere equipped with Comping rings mounted upon the poles. ‘Yhese prevent excessive nunbineg enu @arry consideravle current. Ly means of ths oscidlosraypn, the current in such a ring mizht ve recorded cimultaneously with tne armature currente This weuld show vue exact relation between the huntin: and tix damping effeot. 57 04D MA