POWER FACTOR INVESTIGATION AND RECOMMENDED REMEDIES aC Meni Ma AIRY e TA Bb RAYNER Pan maa \ VAL apa) THEME Cony Me, eRe Oe ore REET En Meter ee os a ee COD, ae a2 fee Sel en ae POWER FACTOR INVESTIGATION aND REQOMMBUDED REMEDIES af OLDS MOTOK WOES A RELOR? oUBHMITTED FO TEE FACULTY OF Ts MICHIGAS AGRICULTURAL COLLEGE BY Ro Le Hayner We Le tylie 0. W. Gugtateon Le PF. Keeley Candidates for Degree of . Heohelor of Soleoe. June, 1982 THEStS Vo Die Naor vase rye. CON fi ead + 2.) ee] Zege Introduction GP OP GD GF OF OP OP GN OD Ot OF OF oe Oa & OF Ge an SP OD G2 UD On om OD oe Ow on an o> an as 1 Gauses of roor rower Factor GD OP GD GP EP OD FOED OD En OD OF Gs a oD GD CO ome en 6 Effects of Poor Power Faotor q--nnceenweweumeenceee 10 Remedies for Poor Power Factor The Statia Condensers qnnnnn we ww meow wenn en meeoe ne 17 Phe Synchronous Notor ---<<------ wonreeemamcncee 2) fhe Phase Advanocer 62-22 an Go 42 OP On On O OP En GP OP On aD See Se Se Seen ae 25 Remotoring \ pe enn Sew aw mena ee CO C8 Ge SF OH BOSS OSE Os BEE 27 Advantages of rower Pactor Correction -«--«-------- 29 fhe Power Factor Correction Problem at the Olds Motor Works. Deaoription of the Plant q<<---qcnnnsnnnnenenwee Sh Prevailing Power Factor Oonditions oWnnnncn----- 36 Cause of Power Factor Oonditions in Motor Plant and Axle Plant «ncnnweeeeeennoeeenne 86 Requirements for Power Factor correotion wcnnnne £2 Recommended Remedies Plan I Hemotoring -W-nwewewnmwe nomenon mmmncecee 45 Plan IX Static Condensers q- a — Toga ee ees ian Up a) ae) 7) seat teeataaees Sates ta eel past AA LL Are CaneeaES Aas Viet STpecee: Sass secacd ieee geagel essteizas iE : | | ieee pa aan es ; | sirgsts | | ji Gdeassuses Seamesacan sanesmunnd eos, Sagassessussusas onebr ae se } } ; . . gsgessaeees2udec) a) (2: 122 intocatozg tousestead setatttces chizectest ssestehees Caeeeeeatl Hee | TD) 77) 7a VOL eee yesere ’ SSS SRS SSS Saee San line as in Mig. 1. How if a certain amount of inductance isa introduced into the olrouit, the current will lag a certain amount behind the voltage as in Pig. 4. This current vector can be divided into two components, one in phase with the voltage and the other at right angles to it. . Now the power is equal to the voltage times the oomponent of the ourrent in phase with it. The horisontal component in the figure is called the real current aga it is a masure Of real power. The vertical component produces no power and is therefore often called the wattlesas current. However, this term wattless current ie somewhat misleading because this ourrent flowing through a wire will produce heat and consume power. It is now more oommn to speak of it as the reactive currmt. An ameter reads the veotor gum of the real current and reactive current. If the angle of leg is lmown, it can be seen, by the geometry of the figure, that the real or inphase current is equal to the total current times the cosine of the angle of lag,(f). Sow since power is equal to wits times the inphase current, it met (by substitution) be equal to volts times totel current times the cosine §. But we have said that power ie equal to volt-anmperes times power fsotor. Therefore, power factor must be equal to cosine §. This now become our new definition for power factor. a \ie will now take up the factors which determine the angle of lag or lead. let us consider again Fig. 4, but draw it es in Fig. 56 The voltage is here divided into ite two components, one in phase with the current and the other at right angles to it. The inphase oon- ponent is the voltage drop ecross the resistance or Ir ani the quadrature component is the voltage drop ecoross the reactance or Ix. The hypotenuse or Is drop is equal to the impressed E.li.F. If eaoh side of the triangle is divided by I, we have simkler trisngle with sides rr, x, and s, known as the imedence triangle. Now fromthe geometry of the figure, the angle of lag or lead is equal to aro tanx/r. In othe words the angle of lag depends upon the relative values of resistance and reactance. fhe term reactance (x) oan be divided into two classes, inductive reactance and comensive reactance. Mat hemtlioally, inductive reactance in ohms ie equal to 281, where f is the frequency and L is the inductance in henryse Sinoe frequency is constant — in all cOmerois) work, this can be dropped from oon- sideration. The next question is whet constitutes induotancee ‘When ever eae current is flowing through a oiroult, a magnetic field is established around the wire. If the cirouit is in the form of a o0il, a grest many of these lines of force will cut the oclirouit iteelf. Now if the current varies these lines of foroe will vary ond an E.i.¥. will be set up on the otrouit which, according to Lens'sa Law will oppose the originnl Eel, This mgnetio property of the cirouit is called inductance and the opposition to the fiow of current due to this mognetio property of the oirmit ia called reactance. | Condenaive reoctance is just opposite in effect to inductive reactance. This makes it Valuable for power factor correotion, and it will be taken up in detail in o later chapter unéer pover fxeotor oorrection. CAUSES OF POOR POWER Factor. The power factor of a airouit depends upon the nature of the load as before stated. In a circuit composed of incandescent lamps the power factor is praotioally unity because the load is made up alast entirely of pure resistence. But when considerable infuotive apparatis is present in the circuit the power factor is less than unit y. While induotenoe is the ossee of low power factor, the mepitude of its effeot depends upon the ratio between it and the resistance since the phase angle is equal to the aro tangont X/k. Singe inductance is, to a certain degree the cause of poor power factor, to looate the cause of poor power factor means the discovery of the eources of inductance or ocsapacitance in the ocirouit. The imiustion motor offers a distinot problem which is taken up in later discussions. The various sources of induotance in alternating ourrent cironits are induction motors, transformrs, ero lemps and accessory apparatus, reactance coils and even transmission lines. Of these, the induotion motor and the transformer are by far the most important and the rest will be dzopped from this Qiscusaion. The importance of these pieces cf apparatus ia mgnified when one considers the extent to which they are used in industrial establishments. Reference to the performance ourves of the induotion motor, which may be seen in any standard text on Kleotrioal Engineering or in amther part of this thesis, will serve to impress the reader with the serious effects of the lightly louded induction motor on power factor. The transforner offers e cimiler problem but the effect is not so far reaching as in the case of the induation motor. In the following paragraphs an amalytio treatment will be mde in an attempt to explain the effeot of inductanoe and light loeding upon power factor. As before stated, the o.rrent drawn by an indus ti ve oirouit ig oomposed of two conponents "power" and"reactive” current as shown in Pig. 4 The reactive component of the current is the "exoiting” of “magnetising" current. Ite magnitude is governed large- ly by the dimensions and the mtecrial of the induction motor and the transformer. For mtors of lerge pole pitok, the mgnetising current my be as low as £5% of normal full load current, but for mohines having a large numer of poles of emalli pitoh it my. be as high as 60% to 70% of the normal full losd current. Heferring to Hig. 6 the full load current is represented by OB and its magnitude ia the same regardless of ite phase position. ‘Then if the reactive ourrent is, sey 80%, of full load current, Sin @ = aB/OB = .8 OB/OB = .80. Then the power factor is Cos 6 or .60. It is seen that the power factor ia always nearer unity at full load, for any given reactive oomponent, because then the reaotive component is the smellest in comparison. However, it is extremely common to find meohines loaded far below normal, and herein lies one of the greatest causes of low power feotor. ‘then a machine is lightiy loaded the power component of the current is very amall and tho reactive memnetising cormponent is just as great as at full loed.e Hence the current veotor OB (Pig. 6) takes the powition OB' (Fig. 7) in which 0° becomes necessarily greater than 0 and the power factor oorrospomingly less since power factor equale the Cosine @. This is the explanation of the low power feotor at light loads as is shown by the performance curves of induction motors. iith various degrees of loading the transformer performs in a manner similar to the imiuction motor but modern transformers are so designed as to draw a amall mgnetizsing ouxrrent and for this reason the effect upon the power factor is moh less. The evil a@f lightly loaded clectrical spparatue ig now known to be very vrevelant in electrically operated plants. This is due lsrgely to the fact that the power rating of mohines installed for certain purposes is inverisbly lerger than required. The installer of the apparatus is desirous of putting in e mohine that will carry the greatest possible load thet my be put upon it. ticre is the error, for such practice means the ignoring of the fact that ony mtor can stand an overlouwd for a short period end a reocone able overload for o oonsiderable period of tine. For instance, a typioal induction motor will osarry a 300% load momentarily, £53 ovorlonad for 2 hours and 8% over~ load intermittently. Honoe the folly of overmotoring, especially in view of the effect on power factor. Overmotoring is often also due to changes mde in the use of equipment fron tine to tine, where a mohine fornerly used to do work requiring 5 horse- power and motored for this work is changed to 40 work requiring but 1 horsepower no chance being made in the motor instnlintion. The effect of such progedure on power factor is evident. These ore the primery causes of low pover factor which sre now causing central stations to base their oharges for power upon EVA or apparent power instend of upon EW or real power. 10 BFYEC?S OF 200K POVER Factor. Low power factor results in many undesirable things. In general they are listed below;- Inoreased losses in; - (1) Exoiters, (2) Generator Fields, (3) Generator armatures, (4) Distributing Lines, (5) Transforners, (6) Losses due to lower efficienoy on scoount of unbalancing of equipment, (7) In consumers’ distributing system. Heduced capacity of:- (6) Generators, (9) Distributing Lines, (10) Pransformrse, (11) Customers distributing systems, Other effeats: - (18) Heduotion of effective capacity of entire investment, (13) Poor voltege reguilsetion, (14) Increased mintenance due to over-heating. But the economic aspect of the problem is by far the greatest, for every evil of low power factor is ultimtely an economic proposition. The power fuctor prevailing in a plant determines to little extent the li size of conductors, syitohes, end like equipuent necessary. Oonsequently the investment in euch equipmont is dopondent to som extent on the power factor. ‘hus the economic inmortonoe of the problem is dlearly brought out. ‘he undesirabllity of low power faotor, from an economic viewpoint, is caused almost entlrely by the fact timt the design of all eleotric equipment ie not on a KW or “powar" besie but rather on a KVA besis. “he reuson for this is that the heating of the conductors in any equipment places a limit upon the allowable current. This mxiuum curront mitiplied by the rated voltage gives the KVA capacity. But the actrv.al pover, at any givon power factor equals the KVA multiplied by the power fuctoi'e Hence, low pover factor cmses a pro portion- ally iow capacity. This is clearly shown by the ourve (Mg. 8) whioh shows the relation between KVA and KW for various values of pover feator from 0 to 100% The reduced capacity of induction motors operating at low power fnotor is clearly shown by the curves (Pigs. 9-13). The motors to rhich these ourves apply are among those used at the Olds Plante The reduction of capacity is not confined to motors alone bvt affects the capacity of all equipment. Fromthis it my be sem that low power factor menns @ needlesaly high inttial investment in equipment. ss tees ace. coasts GE tg SE Y ~LNAINOAMOP? FAILOVIS ah P ) jaws eansse | / : : yA 6) de ae paar Yo oe a menhecel ae weR FAG antl | ec yi alana : ae | ! : ssameese’ 4 { ea bese! Siaeee: } ’ : t ae ’ ‘ nas } | : pene es SSe wee feet ——— paeahs +o” g eaeEee ——— ESE awe G58> Oe oe ou FEE SURES + = » ro bnes bas be etre aes oS, mel 25 baadeo oe SS eee ee : = td err —_~ ms awewes | : es sf : ' ; : rs, q fon Og OU 40 ‘ a al he) ee has) oe Y, D _—— EE a { : : ) . BSeeats trpeties.' 185 / a3 thepes peas, rss | bee ; a fe / / / | are | | | | ine S beer dk ae ; | —— \ aS a Seca restaeet ihe Ps | | | | | : . aeGuseaauescnactel “i SGRS: oe aeates coanesoses! 2 See eaae 4 ae re Ve : He a a | | | ianee | | NG etniN : : i tasazeverd fenseontes Fe-feestcd Bascal SErets BEd Baha SEES | | | i | ig i | Bea Ls } } ; | ' : / Hg ans. aes} ME" un le ae He ape ie | f nes Byes § ie +tS0 i. ; rs i / | : ; Haire -taltitns tt eedts- | | i | Hf | fei Hate fetta | | Ae ae | | | | ee aurea PN st L ean ; aoe HuetaErveMEstEET | ) | | RSestssces 2 ice hata: i 4} besenet Seeedsadcdectennsr | Bre: Rit dua LEE LEN yi 6) SQ Sait Pi 3 Pi ae PL LOe) 40 30 v4 20 68 vr ope be oe g he PE Re Yak Ae sUsSe ey EU AOSE ote ae eerre 22k ssebareuses —< Gueeeege* SscuEEEn— lag sas oem. ei an Ue ave. 2° yeragege. sbastsre ue ® s ae ce ree* PESTSs FUSES OES. ne 1z But the economic aspect does not end here. As has been mentioned, there is a growing tendenoy on the part of central stations to insist upon the inolusion of a power factor penalty alause in the custom re oOmract. The following schedule shows the relation betwem cost amd power factor for values of power factor from 30 to 100%, ascoording to the practioe of the City of Lansing. The miltipliers listed are applied to the kilowatt hours recorded em the oc.stomer is charged the remiting rate for the product. Hote that 60% ie rated as normal power factor and a bonus is allowed for power used at a power factor in excess of 80%. a power factor of less than 60% results in a miltiplier of greater than 1 being used and consequently a higher oost is peid for the power. At 100% power factor the miltiplier is .935 while at 90% 1% ie 1.622. Thus a power factor of 50% mans a penalty of 74% of the lowest possible cost of power being paid. The effect of this on the operating cost is obvious. Operating efficienay is also seriously affected by low power factor. This is because all losses are either the same or greater at lower factor than they are at high power factor. The copper loss, for instance, varies inversely as the square of the power factor as ghown by the following development: 13 Let I = Value of power component of current, Re resistance of the cirouit Cos 0 = power factor. Then the total or line ourremt (in single phase air cuit 8) wore Copper loss « cx )* Re 1° RR (cop @ ) Cos of Thus the copper loss varies inversely as the equare of the power factor. Among the prinoipal evils of low power factor are excessive heating and poor voltage reguistion. Taking up the first, it ise due, in the case of the motor, to the effort of the motor to develop just as mach power unier heavy loed as it would with high power factor. In so doing the motor draws an excessive totel current in order that the useful or “power" component will be sufficient to do the work. Total current equsis useful onurrent. For example, if full normal power were developed by an induction motor operating at 50% power factor the total ourrent would equal meetuh current ® or twice the useful current. Hence the heating effect would be fou tines as great as at unity power factor since heating varies as the square of the ourrent. Poor regulation at low power factor is due to the abnormally high IR drop which is caweéd by the 14 higher current flowing for the same capacity and also by the increased reactance drop. The diagram (Fig. 14), shows the effect of low power factor upon reguiation. OA shows the position of the val tage veotor at practically unity power factor and 0A' the position at about 70% power factor. OB is the effective voltage on the mtor and is taken at 100%. Veotor OA shows the voltage vector under the first oontitions. OA' is the vector representing the im- pressed voltage umer the second conéitions at whieh @ power faotor of about 70% prevails. Sy ewinging tae voltage veotors back to OX (the reference axis), it is seen that the lower the power factor the greater will be the impressed voltage required to give a ocertein im- pressed voltage, and therefore the poorer will be the reguintion. fnese effects are the principal ones encounter- ed in power faotor investigations and are the ones which will be improved by the installation of corrective apparatus. ; - ee eT enamel ; ween eee eere. fer. a Fears 25 Power Factor Oorreotion which may be applied to any power user having a demand of 50 KW or more. Bffective _ June 2, 21922, Multiplier Constant 09530 - Multiplier Constant 220970 o Average ower Faotor 1OQ awn manne Average Power Faotor 68 OO ORe Oe @ OO @ 99 96 97 96 95 04 93 92 91, 90 69 68 87 8&6 65 64 83 82 81 Ges 62 om Ge C268 ap 68 @GQqr@e Bee @ee GS 62 On a 08 @ ae GOs CP ad G9 oe GD COED GS GD Gb GD am Gb 62 on 6D @@ Gb G2 GD G2 On GD 2 DD o 9356 e 9382 e 9408 a 9434 « 9460 e 9490 e 9620 e 9650 e 9680 «9610 e 9646 «9688 e9718 o 9764 «9790 e 9832 09874 o 9916 «9958 64 635 62 61 60 59 58 57 56 55 54 53 52 51 5O 49 48 47 46 Oe 2 Dee ee Dl OO ae SHS OO DWODOOee 2D Coan > & Can & & GP 63 OO ee OO OO OGG oom OO Se oO eee ee an Ow eee CD an > on Oa OY 2 Oe Snowe = @@ GD on Gn 6 Oo a Oh a POO Oe one wee ee Glen Gn > an @ & @ & Bee @2e Oe ww 1.1062 1.1154 1.1246 121536 1.1450 -~ 1016388 11646 101754 121862 201970 = 122096 1.2222 1.23548 12474 12600 - 122746 1.2892 1.038 1.2184 7B nanennnnne 1.0106 43 --------- 97 annnnnnwe 1.0156 42 ---.----- 76 mnnnnu--- 1.0208 41 ------ a 16 an-~n=- -- 1.0260 - 40 oo--~~--- 74 mnnnnnnne 1.0824 a YB ancnnenne 1.0388 BB wcnncnnne 7B mnaannee= 1.0482 BY onee--ane JI annnnneae 1.0516 BE ennnnnenn 70 Om 62 G0 on EP CD E> aD aD 1.0880 @ 35 2 Oe ene Mee 69 ©> Ob an a0 a2 on SP On 1.0658 34 Se On eeeere 66 D Oden Ov om on 02 Cee 1.0898 SL Oe Mae eam SO @eean Gp Gp G2-Gs Gt ao @ 1.5850 - 1.3496 1.5666 1.5854 1.4008 124170 - 124362 1.4554 104746 1.4938 1.619 ~ 1.5348 1.5566 1.5784 26002 1.6220 - 16 Power factor shall man the average power factor maintained by the customer during the month or period of time for which the electric energy is measured and shall be determined by the reactive component meter method and shall equal kilowatt hours (KWH) dGivided by the square root of the sum of the equares of kilowatt hours (KWH) end reactive kilovolt amphere hours (RKVAH). The Multiplier oonstant corresponding to the power factor for the month as determined by the above method shall be applied to the actual measured monthly consumption of electric energy. The produot so obtained shall be known es billed electrio energy enf shall be the basis Dr computing and rendering customers bill in acoordance.with reguler rate schedule. Approved by the Boerd February 87, 1922. Osoar Ee Bulkeley, Supt. 17 THE SSACIC COMULMERR. The atatio condenser draws a current that is practically 90° ahead of the voltage. For this reason it is important in the oorrection of low power fectors due to lagging currents. A condenser is oomposed of two or more oon- ductors separated by a dieleotric. Commrcially, the condenser unit is composed of a large number of couples of metal foil with paper iaminations as ea dielectric. The couples are treated under vacuum to withdraw all moisture, imersed in ofl, and the container then hermetically sealed to prevent possible absorption of moisture fromthe air. For higher voltages mica is used as a dielectric. A conienser introduces a reactance into the oirouit whish is opposite in effect to imiuctive re- actance. It is onlled confensive reactance. Mathematically the reactance in ohms is equal to 1/2 fC, where £ is the frequency in oyoles per second and C is the capacity in feradsa. ivhere no resistance is present, the amunt of current flowing through the condenser is imiicated by the equation: Ie B7ZCB Where I = current in amperes B= voltage on the condenser. 1s Then the volt~-amperes it is capable of handling is given vy the formula: Volt-mperes @ BI =e 8 £0 K.Veao e202 2 20 x From this: uo KeWede x 20° BTL we This shows that the capacity reqhired for @ given correction is inversely proportional to the square of the voltage. From this it can de seen that 4t is desirable to have the voltage as high as possinple. The General Sleotric Company manufactures a condenser suitavle for 82300 volts. It is devigned to etand a muh higher voltace in order to allow for a liberal factor of safety. How it would not pay to put such a condenser as this across a low voltage line such as a 440 volt cirouit. In this case the voltage impressed on it would pe only 1/5 of what it could stand and the corrective effect would be only 1/25 of that which could be optained. for this reason an auto transformer is used to step up the voltage to the rated voltage of the condenser. The losses in a static condenser are very emall. The loss due to lenkage, in a well made con- denser, shou@d be an infinitesimal quantity. There is en apprecianle loss due to dielectric hysteresis which seldom exceeds one half of one percent of the K.V.A. rating. There is also some sopper loss in the leads to the condenser. When a transformer is used there is another loss introduced amounting to 1% or 8%. The total loss therefore varies from one half of one percent to two and one half percent. The static condenser has no moving parts and therefore requires little or no attention. It ia not as flexible as the aynchronous coftenser out 4% ie well adapted to installations that are permanentiy fixed. THE SYNCHRCNOUS MOTOR. A synchronous motor is similar to an alternator. Oonsider two alternators connected in parallel to the same bus bare with equal field exoitations and running in synchroniem carrying equal loads. In the series cirouit between the alternators no cross-current is flowing ané the voltage vectors are 180° apart. Now if the power supply is cut off from one alternator, its voltage will lag a certain angle vehind the other alternator. This will cause a eross-current So flow in the loop circuit which transmits power to the first machine and it runs as a motor. Like an alternitor, the aynchronous motor may either have a revolving field or a revolving armature. Also, like an alternator, it must have e souroe of direct current to excite its field. The synchronous motor without auxiliary windings has no starting torque. It could be brought up to speed by another motor and synchronised into the line like an alternator. However, it is more common to start a synchroncus motor from the alternating current side by use of an auxiliary winding. This winding consists of imbedding conductors in the face of the poles which converte the machine into a squirrel cage induction motor. It is also necessary to cut down the voltage by means of an auto-transformer for the starting period. As the machine comes up to speed it automatically falls into synchronian and full voltage may then be applied. The squirrel cage winding is automatically out out as it would be custing no lines of force at exactly synchronous speed. In this discussion, we are especially con- cerned about the power factor characteristics of the synchronous motor. We will first take up a general explanation and then a vector analysis. The value of the armature current depends partly upon the losé on the motor, out also largely upon the value of the exoiting current. The watt component of the current is determined by the load on the motor, and the wattlesas component by the value of the direct current excitation, so that the power factor depends vary largely upon the excitation. Suppose the motor is running without a load. The watt component of the ourrent is practically constant and relatively omall. Under these conditions the power factor depends entirely upon the value of excitation. Neglecting the losses which ococur in the machine, when the exoitation is such that the #.M.¥. indused by the main flux in the aymeture winding is exactly equal to the applied voltage, the machine would teke no current. Actually, with this excitation, the armature takes a very small current at unity power factor. For all values of excitation less than the above, the power factor will be less than unity and rapidly approaching sero as excitation diminishes. This is due to the fact that the machine is not sufficiently excited with direct current, and the extra excitation necessary for establishment of an induced 8.M.?%. to balance the applied voltage must be provided by the alternating current supply. The current taken from the mains, being chiefly a magnetizing current, lags greatly pehind the voltage. IZ, on the other hand, the excitation is inoreasea dveyond the value corresponiing to unity power factor, the machine is over-exoited and tends to raise the voltage of the system by sending a current into the mains lagging by 90°. In this case the motor draws a leading current depending upon the amount of over-excitation. Having explained the power factor character is- tice in general terms we will now take up a vector analysis. Oonsidering two cases, one in which the field is under-exsited and the other where it is over-exoited. fhe vector Mg represents the voltage of the generator. (Figs. 15 - 16). The vector Mm represents the counter voltage of the motor which lage a certain angle (B) behind the 160° point depénding upon the oad. ‘The numerical velue of Bm is determined by the excitation of the field. We are taking up two | 1% se epeets eon ae ert oo 2 e. * é ape te cases, one where im is less than Mg and the other where ts is greater than Mg. The voltage tending to send current through the closed loop, sonsisting of the armature of the generator and the armature of the motor and line, will be the vector sum of the two voltages Kg and ie ané it may be represented by vector e which is found by cempleting the parallelo- gren. The current in the loop will lag a certain angle a behind thie resultant voltage due to the inductance of the ciraquit. Referring again to the figures, if the voltage im is emall it will cause the current I to fall behind the voltage Mg and if the voltage Mm is lerge it will cause the current to fall ahead of the impressed voltage Mg. AS the angle a is fixed, thas we see that the power factor of the current Grawn by a synohronous motor is determined by field excitation. fhe synchronous motor has a somewhat limited industrial aypplisation. It cannot be used profitaniy: (1) On emall loads under 100 #.P. (2) On intermittent loads involvi frequent starting and atopping, (3) Where variable speed or adjustable speed is demanded, (4) Where it is necessary to start up under load, 24 Synchronous motors are used extensively (1) Air Compressors, (2) Line shafts, (3) Motor generator sete, (4) Centrifugal pumps. The synchronous motor is frequently over exeited and allowed to run without a load. In this ease, it is salleé a synchronous condenser because it draws a current leading by nearly 90° and it can gherefore be used in power fuctor correction. The sychronous condenser need not be built as rigidly as the syndhronous motor as it does not carry a mechanioal 10ad. TiS PHASES ADVANCER, Another method of correcting for poor power factor has found a limited application in Buyopean countries. This is known as the phase advancer. In the Srat part of the discussion it was stated that poor power factor conditions were largely aue to lightly loaded induction motors which draw a large magn otising current. Under the discussion of the synchrohous motor we pojnted out that the wagnetisation could either be supplied by the direct current field or from the current in the armature. In the same way in an induetion motor, the magnetisation may either be supplied through the static winding at line frequency or through the rotor winding at a very low frequency. fhe phase advancer ie an exeiter which is used 20 supply current at a very low frequency to the rotor of an induction motor. When this ourrent has the proper phase relationship it will supply the magnetizs- ation. Then little or no magnetizing current will be @drawn from the line and the current will have nearly 100% power factor. his method is not useful in our problem because it necessitates getting away from the ideal simplisity of the squirrel cage induction motor. The 26 phase advancer method of power factor aorresction would require that all motors be of the wound rotor type. In addition to this it would require a separate excitor for each machine. In view of theuve facts we will drop this method from the disocuasion. 87 grrr T R RG. A remedy which is of ten employed to correct low power factor is a thorough remotoring of the plant. by referring to the load-power factor curves contained herein it is seen that an underloaded induction motor ie a menace to good power factor. When a email Gapacity motor carries a load of mbt one-half normal the power factor ip in the neighborhood of 65%, while at full load the value of the power factor is increased to 85%. It is obvious that the selection of the proper sise of motor for each particulor machine woul: reault in a higher power factor. In planta where the loads on the motors fluctuate in value, it is somewhat Gifficult to say what capacity motors should be chosen to drive the various machines. If a heavy intermittent load is demanded of a motor, it is safe to asiume that the motor will operate without destructive heating at 50% over- load. In choosing a moter, then, to drive a machine where a heavy load comes on only at intervals, the engineer is justified in choosing one considerandly egnaller. In this way the low power factor due to underloaded induction motors may be inproved. In vremotoring it is well to keep in mind that for group drives of coneiderable sise asynchronous motors may pe mate use of, If the fields are over-excited 29 the motors are causei to draw a leading current therepy materially irproving the plant power factor. A® a rule, however, Synchronous motores are nore expensive than induction motors, and the difficulties encountered in their operation limit their use in industrial plants. Romotoring a plant has some features which renders ite application as a oure for poor power factor of doubtful value. In the first place there ere few concerns which are likely to go to the expense of ramoving a large number of motores, dischrding then and purchasing others to take their places. alse the time required to make such changes would require, in many Gases, a complete shutdown of the plant. Suoh procedure would not be countenanced by plant officials. Where changes in preceont installations are made or where new machines are being put in, sconsider- able care should be taken to see that a motor of proper size is inatalled. If this is done it not only causes a decrease in original cost but also results in an inorensed efficiency and a better power factor. ADVANTAGHS OF POWER PACTOR CORRECTI OZ. When industrial plants purchase their own power there are a mumber of adventages to be gained by mintaining a reasonably high power factor. The advantages all have a bearing on the cost of power or on the satisfactoxy operation of the motors. The first advantage is that of better regulation in distribution systems the importance of which is very evident. As this has bem mentioned be- fore it wl not be dwelt upon. Another advantege which my be mentioned is that of inoreased KW capacity with high power factor. The effect my be seen graphically by referring to the ourve, (Pig. 17). An advantage of no small importance is that with « high value of power factor a moh smaller conductor my be used for supplying a given KW iocad than when poor power fector prevails sseuming equal line losses. ‘he curve accompanying (Pig. &) shows the effect of powrr factor on the sise of aonductor required, The biggest advantage, however, Of maintaining high power factor involve the power factor penalty olauses which have been, of late, inoluded in power contracte. A clause of this kind, which is operative in the City of Lansing, has bem discussed previously. ea 2 re - loved VP Aw ed J S Lo o SJ ak, : Famers Taare © 7pe lee) MET, CAA dae EAM eR bee Pde fe ale lee PAL the pegalty imposed by this clause when compared with the cost of installation and maintenance of static condensers shows very clearly that an inéustrial plant is well repaid for installing correotive apparatua. Pig. 19 shows the effect graphically. These curves were drawn from data calculated on the basig of original cost plus upkeep, interest on investment, and depreciation as cOmared with the cost of power per KW per year unéer the penalty clause. From this the net saving per KW per year is obtained. Details of these ocalonulations are given in the following peges using several different values of power factor as the initial value. Ae 710. Py as Pea ne CORREC gi (Ack OR une ue Seneneae §OS ro: (AA a tee Le Net Saving mDore RESULTING FROM PF. LECTED petacsas nozens seus menaeae LE, 51 Ge ower Zaaotor: Condenser: Or eoost : Ann st at; gorrected to: reyuired : of static ; 6&4 per K.V.A. ; : per X.i- ;:Condenser at : (Int.upkeep & ; eng eeereereeereneer bane : rk Vv Gepreciat } $ $ : $ 75% : 85048 ; 15.60 ; 3.40 3 $ : : $ ; 60 ¢ 2200906 ; 16.10 $ 4.08 $ 3 $ $ $ 65 3 10804) 3 47.76 5 42456 3 s 3 3 3 90 s 1-B4791 : 19.95 : 4.98 $ 3 3 ; 3 96 ¢ 2.40869 ; £2.48 $ 5.61 $ $ $ | 3 3 200i 2278805; 8795 ss Bower Yacotor: Saving $ Vv Or 3 es saving 3 correctad to: per hour ; i year $ per KV t w ‘ $2000 hrs» OS POST 3 g $ 3 3 75% s 200468 ; 14.04 : 20.64 $ $ : 3 3 80 : 20068: 15.60 3 11.87 : $ 3 3 z 65 s .OOB86GB ; 16.86 ; 12.41 $ 5 : ; t 90 s ,00898 ; 17-94 ; 12.96 $ : $ 3 3 95 s 200628 ; 16,84 3 15.23 : 3 $ 3 3 100 g 200684 ; 19,62 3 12.68 corrected to: required : of static § ; per KeVeAce 3 per KE. W. ; condenses at : (Int. oe ves 0s taUBY 7.25 8: Bl 3 80 430; 6208 sD seh 85 ; omles : | (OC: 8.85; 90 5 684985 5 15.60 5e39 95 : 1.00508; 16.05 4.02 ae ee ee a ee coriected toi per boar | igen; vperae™ 784 200235 : 6.90 : 5.09 e0 00886 : asa ° 6.14 85 : .O08R8 9.86 6 6.99 90 ; 200864: 20,98 7.58 96 400894 11.82 , 7.82 2.00 } 20043 12.60 7.26 L G FAO‘ POLER FO C S OF STATIC CONDENCIRS G BASED ON THE PENAL®Y CLAUSE HOW 2C4 CITY OF Power Yaotor; Condenser; U COBt 3 eost at: corrected to; required ; static per X.VeAe 2 : per K.We : Condenser at ;: (Int. upkeep &; to : 216 per KVeAe eciat ion $ $ $ $ 75% ¢ eSB 3; £.215 $ e555 3 g 3 3 $ 60 : e20600 ; 4.75 $ LeolS $ 2 $ : $ 68 : 5988 3 6.89 $ 1.59 3 : $ 3 $ 90 5 e 62584 3 6.61 $ 2216 3 $ 3 3 2 95 s e69252 ; 121,09 3 2.76 $ : 3 $ $ 00 4 01998 66 4.08 3 Ower Factor; 3 Baving for ¥e t saving 3 correobed to: per hour : 2 year per KW : 3 $ $ $ 75% 3: 200064 3; 1.98 3 65 3 z : 4 £ 80 s: 200119 & 3.87 $ £.88 ; : 3 3 s 8s : 0901.58 $ 4.74 3 $.15 : : t $ 3 90 s 00194 ; 4.83 $ 8.67 ; $ 3 $ : 96 >; 9090224 ; 6.72 $ 3.96 3 2 : : : 300 : 200285 7.50 3 32h ¢ This plant, engaged exolusively in the manufacture of automebiles, is one of the largest purchasers of electrical energy in the city of Lansing. It in oompletely eleatrified having more than 1200 motors aggregating approximately 6000 horse- power. Im addition to this it is equipped with electric ovens for enamel drying, electric welders, am an Cleotro-plating shop. Power is delivered to the plant by a four wire, three phase, sixty aycle tramemission line operating at four thousand volts. The company owns its own trans- formers end pays for the energy delivered at a point near the plant on the high tension side. ‘fhe four thousend volt line ia used for the outdoor primary distribution to the transformer banks located in the various sections of the plant. Yor power purposes the voltage is stepped dom to 440 wits end distributed by several circuits from the switchboard room to the mohine panel locations. The lighting oirouite are supplied by separate transformers at 110 volts. fhe totel transformer capacity at the present time is about 9050 ZVA divided as follows:- Motor power~-<<----= 6100 KVA Rnameling ovens --- 8500 Welderg «nnnen- wnmee 100 Lighting ----------_].850 fotal -------- -- 9050 KVA Machine requirements in the past have been auch that the individual drive predominates although a portion of the mohines in the mtor plant are group driven. Sxoessive use of the individual drive has gesulted in an extremely large number of motors of mall eise (6 HP and under). Since these are all of the squirrel cage induction type the result has been a serious reduction in power factor. The design of the distribugion circuits, both primary and secondary, has bee so liberal that even under the present conditions the system has not been loaded in excess of ite KVA capecity. In fact, about the only major oriticiam which may be mde of the plant distributing system is the absence of any mans of shifting the load; at present carried by two banks of transformers, +0 a aingle bank during the season of light load. In other words the system lacks flexibility. In order to ascertain the exact power factor peevailing in the various sections of the plant during various portions of the day, a graphic power factor meter was made wee of. Graphic pewer faster resdings, oovering at least three consecutive operating days, were taken on each of the transformer banke. Typical portions of the curves obtained ere found amng the following pages. Fron these curves the everage, minimum an@ maximum power fector for each bank was obtainel, the remlts being tabulated below: 1, 00ATLOZ MAK EY MA, PF AY: 2F Bldg. #26 80% 70% 77% moter Plent (west) 56 40 47 Moter Plant (east) 58 40 45 Btores K 80 70 70 AXLe Pigt 65 . 47 5S Mnameling Plant 99 99 99 Yrom an inspection of the above data it is at once apparent that the necessity for power facter correction is especially urgent in the case of both the | east and west banks of the motor plant and of the axle piant. The earrection of the poor power factor existing 37 in the moter ami axie plants becomes of even greater importance when we consider that the load on the bank at the enameling plant with a power factor of 994 will be greatly reduced in the near future and will thus still further lower the plant power factor. In addition, the bulk of the energy consumption, foliow- ing the reduction in the enameling plent load, will be in the moter ané axle plants, Peale 5 er ih nace pocad nA gh pol egal AVL TI o b&b -7 Pa hs = 4 of few Bi mae 08 Bo) 2 mee ES men Pk 2s >) FN ee Le PCy Mek a a ae ee | LNYUIJ MOLOL/ MNO ASTM QUOI \ VOLS YIM ITHAIVES Pehl Co maga Tp SGA U TA YAV Wes & 7 \--- 2267 APL ok a me he ae) Me Aad 4 2 ae a | EL Awe BOM el Me PL MLL hP S67 AULT WS BT a Mee Ai lan lt MN eh Mi A a de) O26) = ST AWLS “LI & 7 LN IS FIX se Ke SS me ko Se): 2 ae oe me) Eh) ey 226/ AML Lig | SWVWIAC IAI TaN eA” DHOOIY WOLIVS YIM DixavIy POW C ND MOTOR ZLANT ABD AXIZ PLANT. The poor power factor in these plants is partiy due to the liberal we of individual infivetion moter drive. Although @ portion of the machines ere group /driven the great majority have individual drives. Lightly loafed motors er over-motoring is the greatest evil. The degree to which over-motoring has been carried ean perhaps best be shown by the data on the following page. This Gata is reproduced from @ sheet taken at randen from the graphio wattmeter readings recorded on infividual mohines in the mtor plent. This sheet my be taken as representative of the csnditions existing throughout the plant es the average condition show: by this sheet is practically en avevyage for the entire plant. fhe average loed my de taken as @.5% or lese than half of the rated load. From an examination of the representative power facter ourves of typical motors, Piga. 9 - 18 ineluded in this group, the reason for this poor power factor becomes obvious. A large yroportion of the mtors here are under 10 H.P. and small motors inherently have a poorer power factor than larger motors of the same type. In addition they are usually selected with leas care from an engineering standpoint than are the larger ones. Usually, the person responsible for specifying the sise of the motor adds a few H.P. to be on the safe side. This results in more trouble in the smaller sises then in the larger ones. Another point whioh has probably hed considerable effect in the present over-motoring is the utilisation of motors and mohines for work differing in character from that for which they were originally selected. In fact over-motoring was not so serious an evil at least from the Company’s standpoint, until the power factor penalty clause in the purchase of power became operative. Underloaded transformers might also be con- eidered as an aid in produoing the low power factor now prevailing but their effeot is so slight in com- parison with the effect of the induction motors that it may be disregarded. Grinder GB. G.E. G.3. G.H.8. G.8. GE. G.8. G3. G.B. WHE. W.H.8. Gok. GR. GR. GR. G.B. GK. GB. 1/8 awswnere ares sds @ ~ 9 > aver. mmx. Aver. Max. .P x. 1200 2 S 868 4.026 1800 2.50 Be7B BBB Be 1200 1085 8.5 01067586 BE 1200 1.85 85 16675 3.36 1200 6e85 12.56 8.88 16.78 1200 85s SC 1200 «e7E 07K 8035 0 BS 1200 2.5 6685 3.85 8.88 2.800 25 =e RE BEKO BBE 1260 «s-:1085 0 8B 16675) 8 BB 1160 1626 1.5 1.675 28.02 1200 1.85 1.87 1.675 8.82 1800 8 8 67 67 1200 1.85 1.87 1.678 252 1800 068 10856 6865 1.675 1200 5 68 67 .846 1200 1085 1067 1.675 2861 1200 065 = 68 BAB (KS 41 Wake OF Wotor ated Motor “Aver. hx. AVex« a Drill Gu §8 1200 68 1.25 .645 1.676 Mill G.B- 1800 8 065 =o 67 0645 Lathe 3. 58 1140 Bo5 Ce. 3036 607 Dria2 GE 22/8 1200 1.57 5. 1.88365 6.7 Tepper 0K. od 1200 063 65 645 866 Miller G.e. 71/8 1200 6.25 10. 688 184 Drild Hobart & +| 18200 063 1. G45 1.36 Drili: GB. i 1200 0ST) =o BY 96 496 Drill: 0.8. 71/2 1200 025 025 856 0355 Miller GE. 1/2 1200 1085 1.87 1.675 28.22 Lathe Qk 71/28 1800 1.25 £5 1.675 8.35 Lathe QE. 71/2 1800 95 81.57 1.2465 2812 Lathe GE. 71/8 1800 1.85 1.87 1.675 28.61 Lathe GE. 28 1800 1.85 1.67 1.675 861 Drill QE 8 1200 oS 068 4.025 845 Drill GE. 1:2/8 1200 65 67 1845 1.27 Drill G.B. 1/2 1800 25 25 885 #£.385 Lathe GB 8 1200 065 1.86 .665 1.675 Lathe G.E. 8 1200 05 le. 067 1-34 Grinder G.E. 10 1200 £5 5. 585 206. Refore prescribing remedies to be applied to the various seotions of the works it would be well to review the conditions as they now are. The prevail- ing oonéitions in regard to load and power factor of the various transformer banks are listed below; 100A 70M COMMROTED LOAD PRESENT PF. tor Piant S000 HP. 45% Axle Plant 1600 65 Stores KX 2200 77 Bldg. $26 260 77 Bnameling ovens oo 99 Yrom the above figures it is evident that there in no need for correcting the power factor at the enamdling ovens, both on sogount of the high power factor now existing but aleo because in a short time the use of electrically heated ovens will be disoontinued,. The power factor at Stores K and at Building #26 is also compsrgtively high and sinoe the proportion of the total load carried by these transformers is relatively small no correction will be attempted at these points. Our attention will then be confined to the correotion needed at only the motor plant and the axie plent. An investigation of the operating conditions revealed that the average load factor at these points ie .400. For this reason we will further limit our problem to the condition set forth below. LOOATION COMMECTED LOAD ACTUAL AOTUAL YRESENT KVA REQD. _ . LOAD H.P, FACTOR LOAD HP LOAD KW PF FOR OORREO?. Motor Plant 3000 0% 2200 900 45% 1500 Axle Plant 1600 of 640 480 55% 600 LOCATION MOTOR PLAST = AK. PLAN? Connected Load HP 5000 1600 Load Faotor of 04 Actual Load HP 1200 640 Actual Load KV 900 480 Present PF 45% 55% KVA required for Correct ion 1500 600 Zhe above correction is based on a correction of the power factor, to 95%, this having been found by sotual analysis to be the most economical correction to make. The detaiis of this analysis have been previously disoussed. Curves in Fig. 19 illustrate this anslysia. At this point it would be well to discuss the general method of determining the amount of corrective capacity required for any system The method depends on the trigonometric existing between the real power and the reactive power which has been discussed previousiy. From Vig. 80 can be obtained the correction necessary for various Values of power factor and power. The data necessary for plotting these curves was Ccaloulated by making use of the trigonometrio relsetions mationed above. The problem now resolves itself into one of supplying the necessary oorrective KVA in the amounts specified. The means of accomplishing this will be taken up in the following articles. 45 It is evident fromthe preceeding discussion that the underloaded induction motor is the chief cause for the low power factor existing in the plant. "9 correct this condition the first remedy which oomes to mind is to effect a rearrangemnt of motors eo that each moter is carrying approximately fall load. There are som Objections to this plan and some of them will be disoussed in the following paragraphs. fo Giaconnect the motors which are now driving the individual machines or groups and to substitute motores Which have nearer the required capacity would be a Very expensive undertaking. However, considerable rearranging could be done with good remilts. For instance, if a certain mohine driven by a five horse power motor was found to require but three horse power and a three horse power motor was available from another overmtored maohine, the three horse power mtor could be installed to drive the first mochine. It is recomonded thet in instances where new installations are made ané where changer are necessary in the location of machine in the future that care be taken to see that a motor of proper sise be installed. STATIC OO ° The static condenser is now in use in a large number of plante in this country and hes received moh favorable coment. Yor low voltage work the unit confienser is designed for a working voltage up to about 600 volts and is controlled by an o11 switch provided with a no- voltage coil end overload release. It is also, fitted with auxiliary contacts which discharge the condenser through resistances when the awitoh is in the off position. For higher voltages either unit condensers designed for the voltage or a number of lower voltage condensers may be used. In the general Giacuasion it was show that the capacity varied directly es the frequenty and as the square of the impressed voltage. For this reason the logical place to use these condensers would be on the high.side of the transformer banks using the commercial 2900 volt condenser star connected. This would obviate the necessity of using auto transformering with the condensers and would simplify the installation. The proper place to apply corrective devices is at the load since this increases the K.W. capecity of the secamiaxry distribution system. However, in this case the liberal design of the secondary cirouits renders 47 this unnecessary at the present tine. This will reduce the initial cost of the static condenser installation end render possible the grouping of the condensers in a single apartment with a consequent gaving of valuable floor /space in the plant. From a comparison of Curves 1 ané 4 of the Price Curve sheet, the saving in the initial invesat#ent can be determined. Since economic considerations alone ehould | govern the choice of methods to be employed in correoct- ing the power factor it would be well to make an approximation of the initial cost and upkeep of the necessary condenser capacity for both the motor plant ané axle plant. Yrom previous discussion, the amount of reactive KVA neceasary for raising the power factor in the motor plant from its present value of 45 toa future value of 96 is about 1500 KVA and for the axle plent is about 600 KVA. From the price curve for static condensers the original oost for the motor plant using five three hunired XVA mite would be about $17,500 or using the General Electric Oompeny price list about $23,600, although the former would probably be more nearly oorrect at this ti me. In a aimiler manner the initial cost for the axle plant (using two three hunired units) would be $6,900 ant $9,950 respectively. The total oost would be $24,200 and $55,750. fe sirels tiated: cos REE cle NAB AME Re? Lhe LLL LL / ; iA AE) (ha In mking changes in the future it would be well to bear in mind that synchronow motors cen be obtained which are afapted for use on group drives ana line shafte. Ye would not, however, reoomnend that this method be employed except in cases where it is necessary to maxe changes. The ost of synchronous motors in smell sises (less than 100 HP) isa very high end it is moh better to concentrate ell the correction in one large machine. The statements, under the static condenser pian, regarding the amount of correstion required, apply equally well to the synohronous machine. The amount of correction to be made is about 2100 EVA. If a synohronous oonienser is to be used we recomued thet one mohine of £100 KVA capacity be installed. The reasons for using dDut one machine for the entire plant Sres 1. The cost per KVA is less in the larger machine, 2. The losses decrease with the sise of the machines 3S. The attendance am maintenance required ere reduced to a mininns with one m ohinee 4. Foundations for one large machine less costly than for two smaller mochines, 49 &. Less floor mpece required. The initial cost of a synohroncu condenser of £2100 KVA computed on the basis of $12 per KVA (see price curve) will be $25,800. This price does not inalude the cost of foundations, Milding and other auclliaries. ? Tea Ly eae ay A ee ae hd fe | L509 COMPARISON OF STATIC AD BYNCHRCHOUS CONDENSERS. As we heve shown there are two methods of supplying a leading current, namely, the statie condenser and the synchronous conienser, and we will now compare the tw. First cost ~- The first cost of statia condensers is moh lower than the synchronous con- denser in emell sises up to 500 K.V.A. Above this the gynohronous aOndenser is the cheaper. Refer to Curve NOe Bae Losses - The losses in a static condenser vary from 1/2% to 1% depending on whether it is necessary to uge an auto-transformer. In the synchronous machine the losses range from 4% in the 600 K.V.A. sise to 18% in the 50 E.v.A. condenser. Floor space - The synchronous condenser requires lesa floor apace especially in larger sises. Flexibility - The synohronow condenser is very Miexible, as the power factor my be varied at will by a field theostat. The statio condenser can be varied by constructing it in steps of BD or 6 K.V.A. and cufting in ani out steps as occasion demands. Attendance ~ Ho attendance is required with the static condenser. Heating ~- There is lower temperature rise in the 61 static condenser. The General Electrica static condenser is designed for a 10° rise. Maintenance - Since the static éendenser has no moving parts, no lubrication is needed andi the depreciation ia moh less than the synchronous mechine. fhe choice between the two depends lergely upon the comiitions in the plant. 52 After a oareful consideration of all the elements involved in this problem, it is our opinion that the Dllowing suggested remedy best fits the situation: - Character of Correotive Apparatua;- Statio oondensers of £2300 volt, 3 phase star oonnscted,. Size and location of Units:- Seven ~ three - hundred XFVA units. Five of these units to be connected to the circuit near the east bank of transformers of the litor Plant, ané the remaining two units to be installed on the roof of the axie plant alcse to the axle plant transformer bank. Sumnary of reason underlying the ehoice of this plan:- Firat;- Remedy is imediately effective, Beooné:- (uickness, ease and ainmplicity of } inatallation, Third:- Initial cost lower than other plan, (See approximate prices plen II) Yourth:~ Maintenance ani repairs lower than by any other plan, Pifth:- Does not require special foundations or ooctupy Valuable floor space. or | le Bsterline-Angus Gravhio Waettieter, pe Serial Ho. 6506 ‘Type MS Phase All Wire All Volte 100 ~ 200 - 500 atts 1000 - 2000 - 5000 Movement "A" 100 VY 2721 ohms. Movement "5" 100 V 28684 ohms. Katerline-Angus Graphic Power Factor Meter EA Berial No. 8109 §? ~, te ue ~~ ws 2 po ps 1200 1200 i800 1800 1600 1200 1200 1200 1200 1200 12090 1200 1200 750 1800 1200 1800 1200 2200 1700 1200 IEE KT712 KT712 KT713 kT xT KT KTD2 KP202 KT7 52 KT751 KT712 KT712 KT73l special KT7141 KT7 52 KT713 KT730 KT731 KT762 KT762 KT751 KT761 KT732 KT732 KT732 KT 750 KT 732 KT750 KT712 KTS12 KT731 KT712 KT752 KT731 K?731 KT731 KT73S1 KT762 KT7652 KT762 £T312 ET160 ET731 KT752 ET160 ET180 K?761 KT7651 KT761 ——e-- T. 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Mr tt mt BOD Se FE 1/4 ~~ ~, wt £ 6 SSarreRACORsh s = 6 liyers Myers 1200 1200 1200 1200 1750 1780 1200 2200 1200 680 2600 2xEE KT7®D XTS12 KT3S12 KT762 ET7&O0 KT713 KT128 ET765 KT122 X¥TTS ¥T711 XK TFRES Special KT160 KT761 ¥T7S1 K T3028 KTS12 x EK ETTIUS KT713 KT732 CCL ETAL LD OR sTili? 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