Document V3z6yXm6695ey3Bno02m1evrK

'I Today'# power engineer* are wU aware ol iho advantages high power factor (POWCR, fufy 1953. pp Bit. They weft careluliy the pro# and con# ol uaing aynch/onou* motor# i stood ol capacitor*, to role* pi and get an elficlenl motor boor. So, skipping theory and benefit# ol pf improvement. lot tocklo question ol locating and tiling capacitor#. Three location# used widely are: |i) at secondary unit #ul nation# 111 on secondary bu# duel (3) right at motor loo Trick i to put thorn where they do most p*r dollar invested. Locating right at motor# gonorally moan# groatott loves moot but uauolly do# boat fob Tou can eliminate twitching since capacitor* ate connoctod and disconnected with motor Thi# proves an excellent location provided motor# aro larg and oporaio quite steadily. When motor# orn't operating, th capacitor# represent a ubttanliaJ idle invo#tmonl. II your main aim l# to cut utility charge# by Improving pi, central location near incoming lint# I# the beat bet. Thi# g#r roily coat# lea#, but you lose aome ptu# values--increase plant feeder capacity, reduced power tosses. Where induction motor load# ore small, or where targe me tor# operate .intermittently, secondary unit substation* ar< becoming a common (pot loi locating a capacitor bank. The praciical way to determine capacitor site l* by eolculeting rote of return and actual dollar savings tar rar/ou# final pf# In your plant. Sketch above ehowa typical lorm. What's limit? When incremental saving far each copociter kvar added tails to be economically attraciive. Ill rate ol return On capacitor Investment that's important, but final pi Isn't limited to point corresponding to maximum rate of return, h may be worthwhile lo go beyond this point, even though rote ol return it less, if additional system capacity It released. Bate ol return is ollen greator lor small plants because their load# won't lustily the best utility rates. Developing harmonics a# a result of a slieable capacitor in* etallalion is still a matter ol concern, generally unfustiiied. 10 omo engineers. Theoretical calculation# reveal possibilities ol harmonics and resonance, but il plant voltage I# appro*!* mately norma), ft's proctJcofly Impossible to overload a capaci tor by harmonics. Remember, capacitors don't generate hot* monies: sources aro Ironaiorrfter mogneiitlng current, rectifiers, arc luinaeo#. generators. Manual twitching ol cofracttor* It adequate (n meat plont*. Where kvor of capacitor# is greater than (wo*>hlrds ol th* translormer rating, ilgur# on automatic switching. tows euctncM mactici POWf* tlreun tnlonruptlon: capacity Ill _r,ujiJi!jea, heavier IrUerconJ2pm. totyof P,cml Qonorators, Sagermftan tho( \ugaa short occurs vastly greafor ^ent# flpvy Into if. In oxislrng as well as new onos. circuit ^activedevices thus need much Infwropliftff capacity. Lock ai it coW easily couse a plant lbuKk*n- Two ateP wiil keep ^ out ol such trouble: (I) Know fffaUobJd short-circull currents In year pkmt. (2) Be sure breakers hcmdle them. Siprt by getting the incoming fipuw trom your uiilily. From Ibere on. f*P* in determining available short-circuit currents at any point on your difltribuiion system have beehbotiod down to simplg orith- uisii'c Check with your eguipmeni manufacturer -- several have de veloped simplified methods ol ihcd-drcuii calculation. In selecting interruption equip ment, be sure lo allow (or tomor row's needs os well as today's. /}{ 1 0*': ^ 7'------- VCD]:: ; t:,. '"^7................................... ' ' ' . U.' . I':*-:- WoWodi /'* y"/HJ*hpiar?r{;`- '! . j]' ( / 7 J`v J*T-.,'1 -* 5^. *, r -M,)'' 'Tv,bow g#^rMyl(< /.,* " *[f' ,/ 5 risisd*^ 11 r` *?*?* 'p'tl6wr* ivoieVi- VI*-' PP|3:S1? f Adequate circuit-breaker interrupting capacity takes first place flEEESQjQSH Includ* irons- teraer impedance In short-circuit ca)cuiaUons but don't speclly higher than standard a* It may lead to voHago regu lation trouble. Consider using saveral taaOsr trantlormei* in primary sub and tpUtdng secondary but e one mean# of holding down fault currants. ------------- Designed to limit thori-citcuh current#, reactor* have been uced lor years In generator lead# and bus tfos. Now tome maker# ol mo tor #lartere supply built-in reactor# to hold available short-circuit currents to value# that can be solely handled by motor contactor* or circuit breaker#. Properly ap plied, hlgh-lnterrupting-capaclty lute# chop ihort-ctnruft current ofl in first quar ter cycle, before rnaslmum 1# reached. Translormer# and reactor# modulate cur. rent value#,- fuses, tike circuit breakers, interrupt It. But circuit breaker* o!tn affow several cycles before opening. ."` - ^--Ss,<>jraAofcki* (keyt, JA ; \ Lrtuii 6*Vr#ni.' -.` . | , o*tnloW#( , ' . <ub#nt.ejiB< `Hi:-+ .,V'C'47 '' `` <f*owVc</^v#tV /1 , l [c But consider other circuit component, that limit value o/ .hort-clrcuU current. B*lore jur&plng tc reactor# to cut availobi# short.clrcuil cuironu, consider how th*y'i| aHect over-all plant operation. Tor ihitemee, on main leader bus, they must be died to limit current values In all branch#* oil It. may seriously affect oltoge regulation. And a tout! on any branch circuit pulls voltage down equal ly on ail other branches, may cause **toh tej) the under-vo/loge release* to kick out. Power engineer# now Ilk* to put re. actor* In branch circuits, protecting a group ol small breaker*. ach is Inde pendent and tooetot is unaffected by added foods an main bus. Four impe dance value* meet most low-voltage needs In eeccndary circuit*: O.QIO, 0 015, 0.020, 0.025 ohm#. Each Is available to TOOAVS ClfCTktCAt NUCTtCC cover a range ol fault Currents. Since control centers provide for a 800-amp bus, maximuavconiinuous-cunent rating of roaefore lor them need not be more. Look at vollago regulation again be fore applying reactors: How much wjjj voltage change (tom light to full load? How lar will it dip during motor starting? Would larger breaker* be belter? (03 distribution