SYNCHRONIZING OF ALTERNATORS

RICHARD A BROOKS

HARRY C . GARDNER

THESIS

FOR THE

DEGREE OF BACHELOR OF SC IENCE

ELECTRICAL ENGINEERD IG

COLLEGE OF ENGINEERING

UNIVERSITY OF ILLINO IS

PRESENTED J UNE. 1907

UNIVERSHW’

CH3 1LLINO IS

May 28 , 190'7

THI S I S TO CERTIFYTHAT THETHE S I S PREPARED UNDE R MY SUPERVI S ION BY

RICHARDABNER BROOKS and HARRY CLIFTON GARDNER

ENT ITLED SYNCHRONIZING OFALTERNATORS

I S APPROVED BY ME AS FULFILLING THI S PART OF THE RE#UI REM ENTS FOR THE DEGREE

BACHELOR OF SC IENCE IN ELE CTRI CAL ENGINEERING

HEAD OF DEPARTM ENT OF ELECTRI CAL ENGINEERING

1016565

T i t l e .

f 2 . I N T R O DU C T I O N

5 . T H E O R Y O F S Y N C H R O N I Z I N G

9 . M E T H O D O F S Y N C H R O N I Z I N G o

15 . T HE N E W M E T H O D O F S Y N C H R O N I Z I N G

K

2

4

5 . A DV A N T A G E S O F T HE C O I L

I N T R O D U C T I O N

The dext eri ty requi red for succ e s sfully connec t ing in par-

al l e l two synchronous machine s and the apprehens i on that i s fe l t

by the op erator le s t di sas t er re sul t from the s l ight e s t inaccur-

acy of manipulati on sugg es t ed a s tudy of the method s of synchron-

i z ing in the hope of dimini shing the hazard invo lved .

The exp eriment s conduct ed by Me s srs . Morgan Brooks and

Milton K . Akers c l early demonstrat ed the pract i cabi l i ty of us -

ing a corel e s s induc tanc e in th e synchroni z ing of smal l uni t s .

El ec tri cal engine ers throughout the country que s ti oned the ap-

pli cabi li ty of thi s method in connect i on wi th larg er uni t s , and

as a re sult i t was d ec i d ed to make some inve s t igat i ons along thi s

l ine wi th the machine s in the power plant of the Univers i ty of

I l lino i s .

T H E O R Y O F S Y N C H R O N I Z T N G.

I f two like alt ernator s having the s ame wave form are

running wi th thei r el ec tromo ti ve forc e wave s in. uni son and are

generat ing the same vo l tage they may be mad e to op erat e in parall-

s l .Thi s i s due to the revers ibi l i ty of the

abi li ty of e i ther to op erat e as a synchronous motor in the same

di rect i on of ro tat ion i f i t s dri ving power b e removed . A s ingl e

phas e alt ernator can b e synchroni z ed and op erat ed succ e s s ful ly

in parall el wi th one phas e of a quart er phas e o r of a thre e phas e

alternator . Provid ed the differenc e in speed ,voltage ,and phas e

po s i t i on of the two machine s are no t exc es sive , th ey wi l l fal l ih -

to s t ep and continue to run toge ther s at i sfac tori ly . I t wi l l b e

f ound 5however that there wi ll b e more or l e s s synchroni z ing curr-

ent which wi l l vary great ly according to the condi t i ons exi s ting

at the time when the machinesare connec t ed . Thi s synchroni z ing

current flowing between the machine s i s nec e s sary to ho ld them

togeth er; and re sult s from three di s t inct cau s e s

( 1 ) A differenc e in wave shape of the two al t ernators .

( 2 ) A pul sat i on during each revo luti on of the prime movers of the

a l ternators .

( 3 ) JA differenc e in the value s of el ectromot i ve forc e .

The firs t troubl e i s u sual ly smal l and mani fe s t s i ts elf

only in the cas e of larg e uni t s .Th e be s t known examp l e of thi s

troub l e i s that whi ch the Chi cago Edi son Company exp eri enc ed due

to thi rd harmoni c s in the wave form .

The s econd troubl e i s the mo s t s eri ou s of al l . I t s ac tion

may b e s e en by referenc e to the fo l lowing figure s .

F I G U R E # 1 .

_5_

In Figure #l the e l ec tromo ti ve forc es of th e two al t ernat -

ors are repre s ent ed by th e vec tor s They are drawn s i d e by

s ide , but in real i ty are supp erp o s ed on each o ther , s inc e thei r

suppo s ed e l ec tromoti ve forc e s are exac t ly in phas e . Thus the poin ts

2 , 4 , and the po int 1 are at the same pot enti al and no current flows

between the two alt ernators . If the prime mover of one , however ,

during a revolut i on , , lags b ehind or get s ahead of the other , the

two el ec tromot ive forc e s , ins t ead of b eing exac t ly supp erpo s ed on

each other , swing apart , and are repre s ent ed as shown in Fi gure #8 .

Under thes e condi t ions the po int s 2 , 4 , are no long er at the same

po t ent i al,but have a di fferenc e of po t ent i al b etween them whi ch

ac t s through the imp edanc e of the two al t ernators in seri es, creat—

ing thereby , a current equal to the vol tage divided by thi s

impedance . In completing the diagram Figure #9 , app ears as ‘ l-éa

s inc e all vectors mus t go to a common cent er as at l in thi s cas e .

Therefore the free el ectromotive forc e act ing through the two im-

ped ances as s tat ed , i s shown by the vector l—4a . The current re—

sulting from thi s el ectromot i ve forc e lag s b ehind i t a larg e amount,

s ince the reactanc e ohms of the c i rcui t are much great er than the

r es i s tanc e ohms ; or in Other word s , the c i rcui t of the two arma-

ture s in s eri e s i s an induc tive c i rcui t . Thu s the current flowing

from thi s el ec tromo t ive forc e l-ia i s repre s ent ed by the vec tor

An examinati on of the po s i t i on of the vector shows that i t i s

wel l in phas e wi th the vectors and or , in o ther word s ,

the current i s energy current ; and thu s the cro s s current of two

al t ernators whi ch swing apart in phas e somewhat , b ecau s e of i rreg-

ulari ty in rotat i on of thei r prime mover s i s an energy'

curren t

t ending to pull them tog ether again .

The re lati on shown in the di agram in whi ch the curr-

ent betwe en th e two alt ernators i s equal to the vo l tage di vid -

ed by the impedanc e o f the c i rcui t i s not true for machine s be ing

thrown together . The actual momentary or phas ing current whi ch

flows i s much great er than the vector di fferenc e of the elec tromo t -

ive forc e s would s e em to indi cat e . Thi s i s du e to the fac t that the

i ron in the armature has no t had time to b ecome magneti z ed and to

react against the current whi ch flows becau s e of thi s vec tor di ff-

erenc e .Th i s momentary rush of current i s governed by the re s i s tanc e .

and non-i ron inductanc e of the armatures .Th i s induc tanc e should b e

cons id ered non-i ron or pure induc tanc e s inc e the induc tanc e of the

iron i s prac t i cal ly z ero . The fac t that the ironhas z ero induc tanc e

g ive s ri s e to a condi t i on whi ch i s prac ti cal ly a short ci rcui t , and

a larg e rush of current ensue s , wi th only a smal l vec tor di fferenc e .

I t might s e em at fi rs t that the i ron should have an ins tantaneou s

reactanc e s inc e i t i s capabl e of b ecoming magnet i z ed very qui ckly ,

and al t ernators have b een bui l t for frequenci e s as high as 133 cy-

c les .However , the magneti z ing of i ron i s very much l ike vibrating

a tuning f ork .Af t er the vibrati ons have been s tart ed the fork may

eas i ly be kept in moti on . So i t i s wi th the iron .Th e i ron has what

may b e cal l ed a magneti c inerti a whi ch prevent s i t from becoming

magnet i zed qui ckly enough to reac t and offer an apprec iabl e reac t-

anc e .

Henc e two kind s of cro s s currents may exi s t in paral l el

operat ion of alt ernators ; fi rs t , current s transferring power bet

tween machine s due to phas e di sp lac ement b etween th eir_el ec tromo t -

ive forc e s and , second ; wat t l e s s current s transferring magnet i za—

t i on b etween th e j machines due to a di fference of thei r induc ed

e l ec tromoti ve forc e s ;

https://www.forgottenbooks.com/join

c—R—

plac ement in phas e re sul t s in a very large di fferenc e of ins tan

taneous e l ec tromot i ve forc e of the machine and a very large syn-

chromi z ing current flows whi ch overdo e s the work , acc el erating the

lagging machine too great a d egree .Th i s ins tant ly d i splac e s the

phas e in th e oppo s i t e directi on and another synchroni zing current

i s g enerat ed to re s tore condi ti ons , whi ch al s o overdo e s i t s work .

Thi s di ffi culty i s apt to increas e rather than to dimini sh , and

when machine s do thi s they are s aid to b e pumping or hunting , and

and the synchroni z ing current s frequent ly b ecome so s evere that i t

i s nec e s s ary to s eparat e the two machines .W hen the wave i s o f the

smooth s ine vari ety such as obtains wi th di s tribut ed windings , a

s l ight di sp lac ement in phas e only re sul t s in a smal l synchroni z ing

current b eing generat ed , and the two armature s are brought back in

to phas e wi thout overtravelling .

Under normal condi ti ons the synchroni z ing current i s

pract i cal ly watt l e s s , the only addi ti onal lo s s b eing s l ightly add-

i t i onal copp er lo s s e s , and the fri c ti onal lo s s due to s l ight ly al-

t ering the sp e ed of the mach ine .Th e synchroni z ing current can be

measured when the alt ernators are supplying l oad by p lacing an am-

met er betwe en them in one s ide of the line . The method of making

thi s measurement i s shown in Figure #6 .

F I G U R E

Inductanc e . Ammet er .

M F T H O D O F S Y N C H R O N I Z I N G

Wh en two machine s are to b e swi tched tog ether on the same

busbars they mus t be in s t ep and equal and s imi lar in vo l tage , fo r

to swi tch them together under any o ther ci rcums tanc e s would mean a

short c i rcui t on account of the immens e current s whi ch the mach-

ine s wi ll exchange b etwe en thems elve s . In order to d et ermine wheth —

er or not two mach ines . are in s t ep , vari ou s devi c e s are re sort ed to ,

th emo st common i s that known as the synchroni z ing lamp .Th e machines

whi ch are to b e synchroni z ed tog e ther are connec t ed in s eri e s wi th

a lampbank int erpo s ed , the vol tag e of the lampbank being equal to

the sum of the vol tage s of the two machine s . As the machine s re-

vo lve going into and coming out of phase , , these lamp s fli cker from

a maximum to a minimum . When the lamp i s dark the machine s are in

phas e ; when the lamp i s bright th e

’

mach ines are in oppo s i t i on .

When the lamp fli ckers rapi dly the machines are of di fferent f re-

quenc i es , that i s to say one i s revo lving fas t er than the oth er .Th e

sp eeding machine should b e retarded and the lagging machine should

b e acc el erat ed . When thi s i s prop erly done i t wi l l b e no ted that

the fl i ckering of the synchroni z ing lamp b ecome s l e s s and less—

f re-

quent , and that i t change s more and more s lowly from dark to bright .

I t i s only when the lamp i s dark,and the time Whi ch i t has requi red

t o reach the dark condi ti on from the las t condi t i on of bri lli ancy

i s from one to three second s ( the larg er the machine the longer the

interval should b e ) b efore i t i s safe to throw them together . I f

they are not in exac t s t ep , connecting them tog etherw i l l

caus e

the machine s to exchange synchroni z ing current s and bring them into

s t ep ; thi s in large machine s means the sudden change of sp eed of

many tons of metal and thi s requi re s G reat power . Two machine s

could be ins tantaneous ly in abso lut e s t ep and equal in vo l tag e

and y et one could be traveling ahead of th e o ther . Swi tching them

tog ether und er such condi ti ons would nec ess iat e the exchanging of

suffi c i ent synchroni zing current to transfer the exc e s s momentum

of one machine to the o ther , and would b e very likely to be an ex -

co e s ive current . Equal angular veloc i t i e s of the armatures wi th ref-

erenc e to the pol e pi ec e s i s very nec e s sary , that i s to say , a gi v-

en point on each armature mus t pas s the same number of po l e s p er

s econd . Thi s i s real ly of great er importanc e than that the machine s

should b e exac t ly in phas e , although the latt er i s al so important .

The method of synchroni z ing when the lamp become s dark i s cal l ed

synchroni z ing dark . In high vol tag e machine s , of cours e , a lamp can—

not be employed wi thout the int ervent ion o f one or two transform-

ers . When u s ing two transformers i t b ecome s impo s s ibl e to connec t

the transformers s o that when the machine s are in phas e the trans -

formers shal l be as s i s ting each o ther in supplying voltage to the

lamp , and maximum bri l l i ancy of the lamp wi l l then corre spond to

agreement in phas e of the machine s . Thi s latt er method i s cal l ed

synchroni z ing bright and i s g eneral ly preferred b ecau s e i t i s found

to b e eas i er to det ermine when a lamp i s at full bri l l i ancy than

when i t i s ab so lut ely currentles s , for i t may b e carrying qui t e a

sub stanti al current wi thout redd ening the fi lament . The lamp may

even be dark wi th a cons iderabl e differenc e in vol tag e . For ins t -

ano e ,s 110 vol t lamp i s dark wi th a pre s sure of twenty to twenty-

five volt s . Furthermore , the fi lament mihgt break at the cruc ial

moment and the lamp would b e dark when i t shoukd be bright . The

re sult of throwing the machine s t og ether under such condi t i ons had

b ett er be surmi s ed than det ermined by exp eriment .

https://www.forgottenbooks.com/join

at i on of synchroni z ing can be carri ed out much more qui ckly and

wi th more c ertainty than where lamp s or vo l t-met er s are us ed .

I t might be wel l to s tat e , ere we l eave thi s sub j ect,

that the incoming machine should be running fas t er than the one on

the bus s e s i f i t i s to r un as a g enerator from the moment of syn-

chronizing . As the load i s gradually p lac ed on the machine the latt-

er wi ll tend to s low down in sp eed ,and wi llnot then take i t s prop—

er proport i on o f the load ,provid ed that the machine s were running

sameat th e

Aspeed at the moment o f synchroni zing . The t endency of the

incoming machine to s low down i s not so very great and hence that

machine need not be rotat ing at a much . high er rat e of sp eed . The

synchroni z ing swi tch . sheuld b e c lo s ed as the e l ectromo tive f orce

vector of the incoming machine i s approaching synchroni sm , so as to

avo id undue s trains on the machi ne s already on the line . I t has

4; b een found that i f the incoming machine i s thrown in parall el aft er

i t s el ectromo t ive forc e vector has pas s ed that of the machine s al-

ready on the line,that undue stre s s e s and strains are p lac ed upon

the machine s already carrying the load .

-13 -

T H E N E W M E T H O D O F S Y N C H R O N I Z I N G

The ski ll required to threw two al t ernators in parall el at

jus t the right ins tant and the dang er to large machine s i f the op -

erator throws them tog ether s l ight ly out of phas e sugg e s t ed thi s

s tudy of the method s of synchroni z ing .Th e probl em i s to reduc e the

phas ing current and s ti l l retain suffi c i ent synchroni z ing power . A s

has b e en previ ous ly s tat ed , the synchroni zing power of the current

d epends upon the lagging of the current due to the armature ind-

uctanc e . Pure re s i s tanc e was fi rs t ins ert ed be tween the two mach —

ine s in the laboratory wi th the re sul t that the synchroni z ing power

of the two current s was d ecreas ed due to the d ecreas ed angl e of lag .

The re s i stanc e was then removed and capaci ty ins ert ed wi th the resb

ul t that the el ec tromoti ve forc e vec tors as sum ed and maintained an

approximat ely 180 degree

relat ion . Inductanc e wi th i ron—core was

then tri ed wi th indi fferent re sul t s . If suffi c i ent inductanc e was

u s ed to cut down the rush of current to a s afe valu e , the synchro -

ni zing power of the current was too vweak . An air-core was then

tri ed and when ad ju s ted to the prop er value , the re sul t s were al l

that could be de s ired . The corel e s s induc tanc e act ed instantaneou s-

ly , gave the des ired lagging current effec t , and prevented the im-

pul sive rush of phas ing current . I t was in thgigxperiment s conduc t —

ed by hessrs . Brook s and Akers that a value of inductance whi ch

would give half the full load current at the great e s t vector di ff-

erenc e s eemed the be st to u s e . The uni t s u s ed in the s e exp eriment s

foundwere 7 K. v. machine s . I t wasA

that wi th one machine on the bus4

bera, the other could b e thrown in parall el at stand sti ll ( exci tat -

i on being approximat e ) and upon reaching synchronou s sp eed the ma-

_14_

chine would fal l into s t ep . The induc tanc e ac t ed much l ike a spring

whi ch would pul l the machine s into s t ep and ho ld th em there . Aft er

i t had been u s ed succ e s sful ly on the smal l uni t s in the laboratory ,

i t was d ec ided to make a coi l for the larger uni t s in the Univers-

i ty power plant . A coi l was de s igned for the 75 K . W . machine . The

ful l load current of thi s machine for one phas e i s amperes . In

ord er to obtain the be s t result s bo th as regard s regulat ion and

amount of current , the induc tanc e as previ ous ly s tat ed , was made

such that one half the full load current flowed under the wor s t con

d i ti ons . Henc e the imp edanc e was equal to BB#/8 5 . 3 or ohms .

The inductanc e mus t therefore b e very nearly the same , for i f the

re s i s tanc e be large the effect i s that of a cored inductance .Th e

formula f or a cyl indri cal coi l of wi re of radiu s r , of l ength l ,

and having n turns of wire i s L 4' u8r2 n2/ i in whi ch

L Inductanc e ; r radius of coi l in c entimet er s ; 1 l ength o f

coi l in c ent imet er s . Thi s formula i s , however , only approximat e for

short , thi ck coi l s , and could not b e re l i ed upon in thi s exp eriment .

From the formula i t wi l l b e s e en that where r i s larg e compared

wi th l the induc tanc e wi ll be large . To obtain the maximum induc t ~

anc e wi th the minimum l ength of wi re i t was d ec i ded to make the

coi l in the shap e of a pancake gthat i s , the di amet er should be very

large compared wi th the l ength . Al so from some preliminary experi-

ment s i t was proved that the induc tanc e vari ed wi th the square o f

the number of turn s . A form 1 inche s long and 7 feet in di am-

et er was made and wound wi th 97 turns of #8 wire . Thi s wi re was

double co tton covered , and as a further prot ec ti on a s trip of high

t ens i on insulat ioh was plac ed be twe en each layer . Thi s co i l when

t e st ed out gave the following re sul t s

https://www.forgottenbooks.com/join

-16-

The coi l was connec t ed on the p lant betwe en the 12 0 K. W. and the

45 K . v. machine s as shown in Figure fi4 ~ The re sul t s ob tained ex-

ceed ed our great e s t expectati ons . The condi t i ons exi s ting at the

t ime were as follows #— 12 0 K. W . machine on the bus s e s carrying

ful l lead ; one phas e of the 45 K. W . machine was then thrown in par

al l el wi th one phas e of the 120 K. W . machine at the po int when

the lamp indi cat ed that the two machine s were in synchroni sm .Th e

phas e ang l e at whi ch . th ey were thrown tog ether was then increas ed

by a small increment each time unti l the machine s were finally

thrown together at a phas e ang l e of 18 0 d egrees ,Th e current whi ch

might be exp ected at thi s , th e worst , condi ti on i s BB#/7 . 98 or 110

amp eres .The ac tual phas ing current whi ch flowed was 40 amp eres . Th i s

current was a great amount l e s s than. had be en exp ec t ed , and was s o

small that the parall el ing of the two machines did no t caus e the

s light e s t fli ckering of the lamp s on the sy st em . Thi s co i l was con-

sid ered too large , and ano ther form was made whi ch was 1 inche s

long and 2 feet in diamet er . The wire was th en. unwound from the

larger form and rewound upon the small er one .Thi s gave a co i l of 17

layer s of 10 turns each . making a total of 170 turns . The imp edanc e

of thi s coi l was ohms . Thi s was con s idered too large and so

2 layers were taken off l eaving a to tal of 150 turns . The re sult s

obtained from the t e s t of thi s coi l are as follows #-

( See table s on next page )

value

Hean=6l . 9 Mean# 9 . 8 9 Mean= .02 55 Henrys .

Figure

Vol t Machine .

Ammet er .

Coil .

45 K . W. , 440 Vol t 1 Machine .

Synchroni z ing

Swi tch .

https://www.forgottenbooks.com/join

O

Thi s coi l was then connec t ed on the plant under the fol lowing

condi ti ons

12 0 K . W . on the bus -bars , heavi ly loaded ; 45 K. W-

coming in ; synchroni zing to be done dark .

The swi tch was clo sed‘

and the machine s came into synchroni sm . I t

was found impo s sibl e to thro t tl e the small er to such an ext ent as

to s ecure a synchronous sp e ed , and as a re sul t the f hunting of the

two machine s could b e readi ly ob s erved by the defl ec ti ons of the

ammet er needl e . A ci rculating current whi ch vari ed in value from

10 to 110 flowed between the two machine s . I t was found that in

breaking the cirmui t a large arc was oft en drawn out . By watching

the ammet er i t was found that no arc re sult ed if the swi tch were

thrown when the needl e began to swing back towards O.Th e circui t“was

then made and broken rep eat edly , no at t enti on being pai d to the time

of synchroni z ing . The machine s came into s t ep wi th the same eas e

that was ob s erved when they were synchroni z ed prop erly .Th e phas ing

current obs erved ,vari ed anywhere from 10 to 110 amp ere s , depending

upon the vector di fferenc e of the el ec tromo t i ve force s . I t was

thought that data might be taken Whi ch would gi ve a curve betwe en

vector di fferenc e s and phas ing current ,but owing to the bal l i s ti c

effect s of the ins trument s, no accurat e re sult s could be obtained .

However ,a curve was drawn for the co i l showing the re lati ons o f E

and I u s ing the value s of I as abs ci s sas . Thi s curve i s a s traight

l ine showing a cons tant relati on . Reference to the data wi ll show

almo s t simi lar re lat ions for I and Z, and for I and L.

( For the curve of E and I , , s e e the next pag e )

on the preceding page plo tt ed from the above s et of

https://www.forgottenbooks.com/join

The s econd advantage of thi s coi l i s th e low co s t as compared

wi th the to tal co s t of the p lant equipment . Referenc e wi l l here be

again made to the co i l u s ed in thi s exp eriment . The to tal amount

of wi re us ed wa s 2 7# whi ch at 40 c ent s a pound would gi ve a to tal

co s t of In wel l eq uipp ed factori e s the co i l could be turn

ed out at a pri c e differing but li t tl e from the above figure s , and

40 c ent s per pound would cover the cos t of the f orm ,construct ion ,

etc . , being the to tal co s t ready to connec t in on the plant .

.Aasuming that the co st of the alt ernators i s $ 20 p er K . W . and tha t

165 K . W . were u s ed in the experiment ( one 12 0K. W . and one 45 K.W )

the to tal co st of the uni t s would b e 85500 . I t may ea s i ly be s een

that the co s t of the co i l would b e . 52 of one 7? or about of

1% of the co s t of the al t ernators .

The thi rd advantage i s the insuranc e agains t lo sse s due to in-

acfiuracy in synchronizing . The insurance thu s afforded i s much

cheap er than can b e obtained from any casual i ty company . The ind-

notamo s has the advantag e that i t prevent s acci dent s rather than

s ett l e s for damage already done and the cons equent delay and worry .

There iis alse a gain. in time in synchroni zing . Thi s i s qui t e an ad-

vantage , especially in the p eak of the load , or when the load come s

on. very quickly ,and the machine s mus t be go tt en on the line as qui ck

ly as po s s ibl e . The incoming machine may b e put on the sys t em at

onc e even though i t i s a li t tl e out of phase ,and by means of thi s

induc tanc e the machine wi l l very qui ckly come into s t ep wi th the

one on. the line .The induc tanc e may be out out by means of a short

c i rcui ting swi tch , Thus , thi s method afford s a means o f p i cking up

the load much. more rapidly than could be att empt ed by any other

method . But to return to the t echni cal s i de of the sub j ec t . I t i s

no t int ended that wi th large uni t s , th e synchroni z ing shal l be done

‘wi th one machine at a s tand s ti l l as was done wi th ' the smal l mach—

ine s in the laboratory ,nor that the synchroni z ing shal l be done

carel e s s ly and the swi tch c lo s ed at any time . I t i s int ended how-

ever , to do away wi th the great danger of s light inac curac i e s and

thus the att endant i s in bett er shap e to do the work . Knowing that

the co i l wi ll take care of even fai rly large errors which he may

make in the time of c lo s ing the swi tch , the att endant can s et about

hi s work wi th l e s s nervousne s s and wi l l undoubt edly s core a high-

er perc entage of succ e s sful att empt s at synchroni z ing than wi th-

out the cmil .