The 65,000-Kv-a. Generator of the Niagara Falls Power Company

By W. J. FOSTER Fellow, Α. I. Ε. E.

AND A. E. GLASS Both of the General Electric Co., Schenectady, Ν. Y.

AT the close of t h e 19th cen tu ry a no t ab l e even t occurred a t N iaga ra Fa l l s ,—the deve lopment of a p lan t for t h e ut i l iza t ion electrically of N i a g a r a

power. Then , as now, N iaga ra Fal ls was recognized as the finest wa te r power in t he world, a c a t a r a c t of great height, fed from, t h e five G r e a t Lakes , cons t i t u t ing a water s torage w i thou t a r ival . I t was in keeping with t he s i tuat ion t h a t t h e first p l a n t was developed with m a m m o t h un i t s , m u c h larger t h a n had been dreamed of u p t o t h a t t ime . T h e y were 5000 horse power each, or, t r ans la ted in to electrical t e rms , 3750 kw., eleven of these un i t s unde r one roof.

Almost exact ly twenty-five years la ter a genera tor with nominal r a t i ng of 65,000 kv-a . or one capable of 50 per cent greater o u t p u t t h a n t h e en t i re row of un i t s in the original power house, was p u t in to service. Th i s la tes t generator is t h e p r o d u c t of t h e experience gained dur ing t h e in tervening years , I t is three-phase , instead of two-phase ; i t is 12,000 vol ts , ins tead of 2200; i t is 80 per cent power factor, ins tead of un i ty -power factor; i t has high in ternal reac tance , ins tead of low; it has losses a t full-rated load equal t o approx imate ly 2 per cent of i ts ou tpu t , whereas t h e original h a d from 7 per cent t o 8 per cen t ; i t is of t he ' ' c o n v e n t i o n a l / ' internal-revolving field type , whereas t h e original h a d its field revolving outs ide of t h e a r m a t u r e ; i t suppor t s on i ts s ta tor , b y means of t h r u s t bear ing m o u n t e d a t the top , t h e ent i re weight of i t s own ro tor and t h e runner of t h e tu rb ine , whereas t he original had i t s revolving p a r t suppor ted from an oil-pressure s t ep bear ing located u n d e r n e a t h ; i t is located so close t o t h e tu rb ine t h a t i t h a s no lower guide bear ing of i t s own, whereas t h e original was some 150 ft. above t h e t u r b i n e with several guide bear ings in te rvening; i t is equipped with brakes t o br ing i t t o res t quickly, whereas t h e original had no means provided for br inging i t t o res t , except t he shu t t i ng off of t h e wa te r t o t h e t u rb ine ; i t contains approximate ly twen ty - th ree pounds of m a ­terial per kv-a. o u t p u t , whereas t h e original conta ined nearly fifty pounds .

Although t h e q u a n t i t y of mater ia l in th is large generator is less t h a n a half t h a t of t h e original per kv-a., i t is ve ry large a s compared wi th a modern 60-cycle generator of large capac i ty a t t h e higher speeds t h a t are now common in hydraul ic deve lopments . There a re th ree reasons for th is genera tor hav ing such great weight as one and one-half million pounds of mater ia l ; first, t h e fact t h a t i t is low speed; second, i t

To be -presented at the Spring Convention of the A. I. E. E.t

Birmingham, Ala., April 7-11, 1924-

is low per iodic i ty ; th i rd , i t was designed for t he highest economic efficiency.

Regard ing t h e effect of ro t a t i ve speed on weight, i t m a y be said, t h a t for t h e same electrical character is t ics t h e lower t h e per ipheral speed, t h e grea ter t h e weight of magne t i c mate r ia l and copper, and t h a t t h e lower r o t a t i v e speed a lways requires a lower per ipheral speed to ob ta in t h e proper a d j u s t m e n t be tween t h e mater ia l t h a t m u s t be used for mechanical s t ruc tu re and t h a t which m u s t be used for t h e electrical pa r t s . In t h e case of th i s generator , t h e per ipheral speed is only 8200 ft. per minu te , whereas m a n y 50 and 60-cycle hy­draul ic genera tors t h a t have been bui l t a t speeds from 200 t o 600 rev . per min . h a v e per ipheral speeds of 12,000 ft. per min. , or h igher ,—some of t h e m as high as 15,000 ft. per min .

W i t h regard t o t h e effect of per iodici ty on q u a n t i t y of ma t e r i a l ; a s suming same o u t p u t , same character ­istics, s ame ro t a t i ve speed and same per ipheral velo­ci ty , t h e to t a l magne t i c flux in t h e a i rgap m u s t be the same a t all periodicit ies, b u t t h e lower periodici ty mach ine has fewer poles a n d t h e flux l inked th rough a r m a t u r e from pole t o pole is in inverse ra t io t o the per iodic i ty , a 25-cycle mach ine hav ing 2.4 t imes t h a t of a 60-cycle; hence, a cross section of a r m a t u r e core t h a t m a n y t imes grea ter m u s t be provided. For­mer ly , t h e lower per iodici ty pe rmi t t ed of higher mag­net ic densi t ies in t ee th and core of a r m a t u r e , b u t silicon steels h a v e been developed wi th such high quali t ies in t h e m a t t e r of hysteresis losses t h a t t h e lower periodic­i t y no longer has a n y a d v a n t a g e in th is respect . All periodicities u p to 60 cycles are worked a t as high s a tu r a t i on as permeabi l i ty allows. Again, t h e smaller n u m b e r of poles in t h e 25-cycle machine requires a m u c h grea ter radial d e p t h of pole for hea t dissipation reasons , a n d grea t ly increased cross section of t h e copper on t h e pole. For these reasons, t h e to ta l q u a n t i t y of magne t i c mate r ia l in t h e poles and the to t a l a m o u n t of copper in t h e field-winding are greater t h a n in t h e corresponding 60-cycle genera tor .

W i t h reference t o increase in mater ia l t h a t was in t ro­duced in order t o o b t a i n t h e h ighes t economic efficiency, i t m a y be said, t h a t a s far as t e m p e r a t u r e s were con­cerned, t h e a m o u n t of copper in b o t h a r m a t u r e and field could have been reduced a t least 20 per cent , and t h e a m o u n t of magne t i c mate r ia l as m u c h as 10 per cent . In order t o ob ta in ext remely high efficiency, \t was necessary t o reduce several or all of t h e var ious Kinds of losses, windage, hysteresis and eddy current , Γ- R -and load losses. T h e mos t i m p o r t a n t factor in

3 6 5

3 6 6 FOSTER A N D GLASS: 65,000-KV-A. GENERATORS Journal Α. I. Ε. E.

t h e windage losses is per iphera l speed; hence, i t is generally bes t t o select smaller d iameter , a l though i t resul ts in increased magne t i c mate r ia l and copper . Lower hysteresis a n d eddy losses m a y be obta ined b y working a t lower densi t ies; consequent ly , g rea te r a m o u n t of mater ia l m u s t be used in t h e magne t i c p a r t s . Lower I 2 R losses can be ob ta ined b y increasing t h e q u a n t i t y of copper . Load losses can be k e p t lower b y conservat ive design in t h e m a t t e r of a r m a t u r e reac­t ion, b u t t h e size of t h e mach ine is increased b y reason of t h e lower a r m a t u r e react ion.

T h e electrical character is t ics of th i s genera tor a re in accord wi th w h a t is regarded a s bes t for power-pro­ducing purposes in large sys tems . T h e ampere t u r n s a t no load, 12,000 vol ts , a re a lmos t ident ical ly t h e same as required for r a t ed cur ren t on short-circui t .

T h e calculated a r m a t u r e reac tance is 26 per cent . Unusua l features in t h e electrical design are t h e

low po in t on sa tu ra t i on curve a t r a t ed vol tage, m a d e necessary b y t h e r equ i remen t of opera t ing cont inuously a t 13,200 vol ts , 68,250 kv-a . 80 per cent power factor, and t h e ve ry low-current densit ies a t which copper is working, approx imate ly 1300 a m -

largest ever bui l t , would in itself be sufficient justifica­t ion for describing it , b u t in addi t ion , i t conta ins a few features t h a t a re ent i rely new, as far as t h e wri ters of th i s pape r know. M a n y large vert ical hydraul ic un i t s h a v e a l ready been bui l t , due to t he ever increasing de­m a n d for power and to t h e greater simplicity and econ­o m y in power houses a n d auxil iary a p p a r a t u s t h u s ob ta ined . T h e pr incipal p a r t s of such large genera tors m a y be s t a t ed as s t a to r f rame; s t a to r core; s t a to r winding; shaft ; ro to r spider; poles; field coils; uppe r

0 1000 2000 3000 . 4000 5000 6000 AMPERES ARMATURE

FIG. 2 — F I E L D CHARACTERISTIC CURVES A—Α ι 100 per c e n t P o w e r F a c t o r 12 ,000 V o l t s 65 ,000 k v - a . B—Bi 80 " " " " 12 ,000 " 65 ,000 k v - a . C — C i 80 " " " " * 13 ,200 " 6 8 , 2 5 0 k v - a .

AMPERES FIELD

FIG. 1 — T H E 6 5 , 0 0 0 K V - A . GENERATOR OF THE NIAGARA FALLS POWER Co.

Sa tura t ion C u r v e s A—Open Circu i t Β—Full L o a d Current 100 per c e n t P o w e r F a c t o r C — " " " 8 0 " D— " " " zero " "

peres per square inch in a r m a t u r e and 1100 in field, in order t o ob ta in t h e ve ry high efficiency.

Fig . 1 conta ins Curves of no load, 100 per cent a n d 80 per cent power factor full-load sa tu ra t ion .

Fig . 2 shows Curves of Field Charac ter i s t ics for th ree condit ions, viz., 100 per cent power factor, 65,000 kv-a. , 12,000 vo l t s ; 80 per cen t power factor, 65,000 kv-a. , 12,000 vol ts and 80 per cent power factor, 68,250 kv-a. , 13,200 vol t s .

T h e fact t h a t th is genera tor is, for t h e t ime being, t h e

bear ings ' spider; bear ings ; oiling sys tem; collector r ings . The re are numerous detai l p a r t s in connection wi th every one of these major p a r t s t h a t are of ext reme impor t ance a n d w o r t h y of descript ion. Before t ak ing u p t h e major p a r t s in order, we call a t t en t i on to Fig. 3, which shows t h e general a r r angemen t of t h e generator , t h e s t a to r suppor ted b y a cont inuous base r ing, t h r u s t bear ing car ry ing t h e to t a l weight of t h e generator and water-wheel r o t a t i n g elements , including wate r t h ru s t , m o u n t e d on t h e uppe r bear ing bracke t . This b racke t also carries t h e genera tor guide bear ing. T h e water -wheel guide bear ing is located direct ly above the tu rb ine runner . T h e p rox imi ty of genera tor ro tor t o t u r b i n e runne r e l iminates a th i rd , or middle guide bear ing, which is often placed immedia te ly u n d e r n e a t h t h e genera tor .

T h e novel features in th is genera tor are shown in Fig. 3 , in t h e placing of an exci ta t ion genera tor with r a t i ng 650-kv-a., t h e s t a t iona ry p a r t suspended from t h e upper bear ings ' b racke t and t h e revolving p a r t m o u n t e d on t h e a r m s of t he revolving spider of ma in genera tor . T h e collector slip r ings for supplying excit­ing cur ren t t o th is small generator , as also those for ma in generator , are shown moun ted immedia te ly above t h e t h r u s t bear ing. A t t h e ext reme top is moun ted a speed l imit ing device. These p a r t s are protec ted b y a housing of pleasing design. This new generator ha s t h e same lines as t h e 32,500 kv-a . generators , installed in t h e same s ta t ion a b o u t th ree years ago and designed in accordance wi th t h e ideas of t h e engineers of t h e N iaga ra Fal ls Power Company . Fig. 4 shows the close agreement in outl ines of t h e two generators , t h e one exact ly double t h e o ther in capaci ty , and gives a t

April 1924 FOSTER A N D GLASS: 65,000-KV-A. GENERATORS 367

t he same t i m e a clear idea of t h e re la t ive space above floor, requi red b y t h e respect ive machinés .

STATOR

The cas t iron s t a to r frame is m a d e in four sections, for purposes of cast ing, machin ing , handl ing in t h e factory, t r anspor t ing and erect ing a t power house. Each section measured 22 ft. across t h e arc and 10 ft. in height . T h e sections a re keyed, doweled and p u t together wi th sufficient bol t s t o w i t h s t a n d m a x i m u m short-circuit s t ra ins . Similarly, t h e comple te s t a to r frame is r igidly doweled a n d bol ted t o t h e base r ing . The final ad jus tmen t s for a l ignment a re m a d e b y m e a n s of adjust ing screws in t h e base r ing. A t t h e t o p of t h e

r u n n i n g t h e en t i re length of t h e core and located be­tween core a n d s t a t o r f rame. B y c lamping t h e core wi th t h r o u g h bol t s in th i s manne r , t h e s t a to r f rame is relieved from s t ra ins which m i g h t exist if t h e c lamping flanges were a t t a c h e d b y bol t s screwed in to t h e s ta tor f rame, as is c u s t o m a r y in smaller machines . Shims are provided u n d e r n e a t h c lamping flanges, in order t h a t a n y looseness of core m a y be t a k e n up , in case such looseness should ever develop. T h e core wasVas-sembled a t t h e power house as a comple te circle so t h a t t h e l amina t ions are s taggered everywhere and the re are no jo in t s in t h e core, which are somet imes responsible for noise, due t o v ib ra t ions of t h e edges of t h e lamina­t ions immedia te ly a t t h e jo in t e

FIG. 3 — C R O S S SECTION OF ASSEMBLED GENERATOR

s ta tor frame is a project ing flange for t h e a t t a c h m e n t of vent i la t ion housing t h a t su r rounds t h e mach ine , for t he purpose of car ry ing a w a y t h e w a r m air .

STATOR CORE

The laminat ions of core a re assembled on keys a t t ached to s t a to r frame r ibs b y screws. T h e core is bui l t u p in numerous sections separa ted from one ano ther b y " I " b e a m space blocks, so a s t o p rov ide vent i la t ing duc t s . T h e core, b y reason of i t s immense size, is c lamped toge ther b y ex t r a h e a v y cast-steel clamping flanges a t t o p and b o t t o m wi th large bo l t s

A special device for assembling and pressing the core was m a d e for th i s pa r t i cu la r instal la t ion and is shown in F ig . 5.

T h e lamina t ions a re of t h e bes t g rade of silicon steel, of same th ickness a n d wi th every sheet enamelled on b o t h sides, in same m a n n e r a n d wi th s a m e ca re as for cores of t h e larges t a n d m o s t i m p o r t a n t 60-cycle genera tors .

STATOR W I N D I N G

T h e a r m a t u r e winding consists of 360 coils, th ree t u r n s each of r ec tangu la r wire, 36 s t r ands in mult iple ,

368 FOSTER A N D GLASS: 65,000-KV-A. GENERATORS Journal Α. I. Ε. E.

spann ing 70 per cent of t h e pole a rc . T h e n u m b e r of coils per pole is fractional, 12 6 / 7 , t o e l iminate higher harmonics . T h e coils are connected u p in four circuits per phase . All connect ions from coil t o coil in t h e var ious phase bel ts , as well a s t h e pole connect ions and t h e phase leads a t beginning and endings, a re m a d e a t t h e t o p of t he machine . B o t h ends of all phase windings a re carried t o t h e busses outs ide frame for

T h e insula t ion of such large coils ha s been developed wi th cer ta in desirable character is t ics in view, such as t h e e l iminat ion of all pocke ts for air, or o ther gases, t o avoid in te rna l corona and t h e in t roduc t ion of sufficient flexibility t o pe rmi t bend ing or yielding when coils a re being assembled in deep radial slots or being removed in case repai rs a re ever m a d e .

A cer ta in a m o u n t of hea t should be applied before

FIG. 4—SUPERIMPOSED OUTLINES OF 3 2 , 5 0 0 K V - A . AND 6 5 , 0 0 0 KV-A. GENERATORS OF NIAGARA FALLS POWER CO.

connect ing in t he differential relay protec t ion a p p a r a t u s .

T h e weight of one insulated coil is ltf6 lb . T h e weight of t h e completely insula ted and connected winding is approx imate ly 70,000 lb . T h e windings a t heads of mach ine a re laced back t o insula ted suppor t ing bands wi th blocking be tween t h e coils, while t h e end connect ions a re a r ranged in a n e a t a n d sys temat ic m a n n e r and similarly blocked. See Fig. 6.

T h e insula t ion on t u rn s , as also t h e external insula­t ion, consis ts of mica, p u t on in t h e form of t a p e wi th a specially developed varn ish as s t icker . T h e coils were subjected to v a c u u m t r e a t m e n t and moulded t o size a t different s tages of t h e process. A cross section th rough t h e slot, Fig . 7, gives a clear idea of t h e com­posit ion of t h e conduc tor and t h e re la t ive th ickness of t h e insulat ion. p I G > 5—STATOR CORE ASSEMBLING AND PRESSING DEVICE

April 1 9 2 4 F O S T E R A N D G L A S S : 6 5 , 0 0 0 - K V - A . G E N E R A T O R S 3 6 9

r im b y two nickel steel shr ink keys extending across t h e full b r e a d t h of r im. T h e half hubs are rabbe ted and fastened toge ther b y numerous large nickel-steel shrink bol ts . T w o shaft keys, d iametr ical ly opposi te and ex tending ent i re length of h u b , p reven t ro tor tu rn ing on shaft agains t t o rque . R o t o r h u b a t lower end rests u p o n a shoulder or project ion of t he shaft and a t upper end is held in place and kep t from lifting, when brakes a re applied t o r im unde rnea th , by means of a circular spli t r ing key set in to shaft and bol ted to h u b . This mult iple-wheel t y p e of ro to r spider, wi th circum-

FIG. 7 — C R O S S SECTION OF STATOR COILS IN

SLOT

coils are assembled, as also when t ak ing coils o u t of slots. For t he winding of a r m a t u r e of t h e N iaga ra generator in the power house a special hea t ing oven was made—Fig . 8.

ROTOR S P I D E R

As a rule, less t ime is required t o design t h e revolving field of a high-speed large-capaci ty genera tor t h a n a low speed generator , for t h e reason t h a t a l amina ted or p la te center wi th dovetai led a n d keyed-on poles is invariably found to be t he proper const ruct ion for t h e

small-diameter, high-speed rotor . However , for a 107 rev. per min.-generator of large capac i ty , several a l ternat ives present themselves , requir ing much s t u d y to decide which is best . R o t o r spider m a y have laminated or p la te r im, or i t m a y be m a d e of steel castings th roughou t or of steel and iron, and in var ious ways. Poles m a y be dovetai led or bol ted, e tc .

T h e ro tor spider of t h e 65,000-kv-a. genera tor is cast steel th roughout , m a d e u p of five sections or wheels, every wheel conta in ing two ident ical cas t ings , half wheels—Fig. 9—fastened toge ther a t each jo in t of t he

ferential spaces a t t h e r im between adjacent wheels, insures a supply of air for removing hea t from field coils. T h e a r m s of t he t op and b o t t o m wheels are pa r t l y covered wi th steel p la tes to reduce windage losses and increases t he flow of air th rough the r im.

T o m a k e sure t h a t all cast ings had the proper physical proper t ies , four tes t coupous were cast on t he r im of every half wheel. Tes t pieces were cu t from these coupons, t u rned to s t anda rd size and pulled in t h e mechanica l l abora tory . T h e resul ts of the tes ts on t he forty samples from t h e ten cast ings t h a t were

3 7 0 F O S T E R A N D G L A S S : 6 5 , 0 0 0 - K V - A . G E N E R A T O R S Journal Α . I. Ε . E .

used in t h e ro to r of t h e first genera tor , were wi th in t h e pole, two in parallel , or four bolts per section of ro tor l imit of t h e con t r ac t specifications.

P O L E S AND F I E L D COILS

T h e pole laminat ions are }/g in- th ick sheet steel, c lamped between heavy cast-steel end p la tes and securely held by large th rough bolts , ins tead of t h e

FIG. 8 — O V E N FOR HEATING ARMATURE COILS WHEN ASSEMBLING

FIG. 9 — R O T O R U N D E R CONSTRUCTION

usual r ivets . Two nickel-steel keys, runn ing t h e ent i re length of pole, including end pla tes , a re set in to pole body and t a p p e d t o receive t h e bolts a t t a ch ing pole to r im.

A novel feature of th is design is t h e me thod of fastening pole pieces to ro to r spider. Ins tead of t h e usual dovetai l , keyed t y p e of pole, t w e n t y nickel-steel t a p bol ts pe r pole a re provided, t e n t h e length of t he

r im, m a k i n g a to ta l of five hundred and s ixty holes drilled radia l ly t h rough t h e ro to r r im. I t was t hough t t h a t ro to r r im cast ing could be t t e r be ' 'explored' ' for shr ink holes and checks, by drilling these radial holes as agains t t h e dovetai l slot, which does no t cu t t h e r im radial ly . Incidenta l ly , n o t one shr ink hole or check was discovered when drilling t h e five h u n d r e d and sixty holes in all t e n sections.

F I E L D COILS

Field coils a re wound wi th copper s t r ap 0.43 in. by 2.625 in. in cross section, which is p robab ly t h e heaviest s t r ap t h a t has ever been used in field coils. I t re­quired from t en to twelve reels of copper for each coil, hence, a b o u t eleven brazings on an average per coil. T h e o rd inary machines for winding copper s t r ap on edge could n o t be used. Fo r tuna t e ly , a m u c h heavier machine , used for forming field coils of t h e largest s t eam tu rb ine generators , was avai lable, a l though cer­t a in modifications were necessary. After forming coil, a special hea t ing and c lamping device was used to mould in to shape for assembly on poles. T h e weight of copper in each coil is 2800 lb .

R o t o r coil suppor t ing brackets , insulated from coils a re provided be tween each pa i r of poles, to p reven t bulging of coils due to side t h rus t . On account of t h e size a n d weight of each pole, a special lifting device was m a d e for lifting t h e pole in to a vert ical posit ion when assembling. See Fig . 9. T h e revolving field, is gua ran teed t o w i th s t and a r u n a w a y overspeed or speed t e s t of 214 rev . pe r min. , or twice normal , a n d such a t e s t was m a d e in t h e fac tory on each section of ro to r spider and witnessed by cus tomers ' representa­t ives . Special poles, each represent ing t h e weight of t h a t p a r t of pole over ro to r spider section, were m a d e u p of lamina t ions and end p la tes a n d a t t a ched to each section of ro to r spider. Lamina t ions , end pla tes a n d pole piece bol ts , used in mak ing tes t , were af terwards used in t h e assembly of t h e complete pole. All five sect ions of ro to r spider passed double speed t e s t successfully.

U P P E R BEARING BRACKET

T h e upper bear ing bracket , on which res ts t he t h r u s t bear ing car ry ing an es t imated load of 1,200,000 lb . is of t h e cen t ra l -hub and separa te -a rm t y p e . T h e cent ra l h u b is a cylindrical steel casting, to which t en radia l a r m s of cas t steel a re rabbe ted , doweled and bol ted, t h e whole when bol ted toge ther hav ing a beveled t u r n lip a t t h e ends of a rm, fitting accura te ly in to t h e s t a to r frame for perfect mechanical a l ignment of b r acke t w i th s t a to r frame, and securely fastened t o t h e frame b y large steel bol ts . Bracke t and bol ts are insulated from s ta to r frame to p reven t " p i t t i n g " of t h e guide bear ing, due to s t r ay cur rents . T h e calculated deflection of 0.055 in. checks ve ry closely wi th ac tua l deflection of 0.063 in., obta ined after generator was

April 1924

FIG. 10^-BASE RING (OUTER) AND BRAKE SUPPORT (INNER)

stead of having s t ra igh t seat fit, as is usual in th i s t y p e of generator .

T h r u s t bear ing is of t h e usua l Kingsbury t ype , wi th water-cooling coils, provided for cooling t h e oil in t h e bearing housing. Th i s bear ing is designed t o ca r ry a max imum load of 1,250,000.1b.

B A S E R I N G AND B R A K E SUPPORT

Another unusua l fea ture of design is t h e segregat ion of the base ring, suppor t ing t h e s t a to r from t h e b rake -suppor t ing r ing. See Fig . 10. B o t h r ings a re cas t in four sections each, bol ted toge ther and separa te ly grouted directly in to t h e foundat ion . T h e b r a k e sup­por t ing r ing designed to t a k e t o t a l weight of revolving elements, when jacks a re applied u n d e r ro to r r im t o relieve weight on t h r u s t bear ing, besides suppor t ing t he brakes when used for shu t t i ng down. T h e base ring is provided wi th convenient man-holes for inspect ion of s ta tor winding a t b o t t o m of generator .

COLLECTOR R I N G S AND CONNECTIONS

At the upper end of t h e shaft a h e a v y cast- i ron support ing shell is bolted for t h e two pa i rs of collector rings, those of ma in genera tor and those of exci ta t ion generator . T h e electrical connect ions be tween r ings and fields are m a d e b y means of r ec tangu la r copper str ips runn ing down from rings t h rough a hole in shaft to a poin t above h u b of ro tor , where t h e y are joined to cables runn ing along a r m s of ro to r spider t o

371

FIG. 11—DIAGRAMMATIC P L A N OF PIPING

lifting of ro to r t o t a k e weight ent i re ly off t h r u s t bearing (when oil a t a pressure of 1400 lb . pe r sq. in. is used) . F o r jack ing u p , oil a t pressure of 1400 lb . pe r sq. in. is supplied by a Watson-St i l lman h a n d p u m p . This opera t ion requires only a shor t t ime , and is ve ry effect­ive as aga ins t t h e more laborious m e t h o d of backing off t h e bol ts on t h e t h r u s t bear ing t o relieve t h e load on bear ing, when inspect ing or disassembling un i t .

FOSTER A N D GLASS: 65,000-KV-A. GENERATOR

field t e rmina l s . All collector connect ions can be m a d e or b roken inside t h e suppor t ing shell. T h e collector r ings t h u s m o u n t e d wi th suppor t ing shell, can be easily removed a n d replaced. T h e shell also suppor ts t h e speed-l imit ing device, a t t h e t o p of which a t acho­me te r m a y b e placed for t ak ing readings of speed, if requi red .

OILING SYSTEM

Fig. 11 shows d i ag rammat i c a r r angemen t of t h e com­ple te p ip ing for each genera tor . A feature of design in th i s a r r angemen t is t h a t genera tor m a y be supplied direct ly from s ta t ion sys tem, or b y separa te motor-dr iven oil p u m p , ac t ing independen t of t h e s ta t ion sys tem. A n o t h e r fea ture is t h e use of t h e same piping for t w o purposes , t h e appl icat ion of t h e brakes to rotor r im t o s h u t down (when compressed air from s ta t ion sys tem a t a pressure of 150 t o 200 lb . is used) and the

installed. Covers a re provided be tween a r m s a n d are par t ia l ly perforated, t o allow cooling air t o be t a k e n in a t top of generator . Two h a n d holes a re provided in outer por t ion of each cover for t h e inspect ion of s ta to r winding and connect ions a t a n y po in t . A plat^ form, suppor ted from bear ing b racke t for inspect ion of t h r u s t bearing, is provided, and a s ta i rway leads t o th i s platform from upper floor of power s ta t ion .

G U I D E AND T H R U S T B E A R I N G

T h e upper guide bear ing is centra l ly suppor ted , in-

372 FOSTER A N D GLASS: 65,000-KV-A. GENERATOR Journal Α. I. Ε. E.

EXCITATION GENERATORS A-c. generators , bo th s t eam and hydrau l ic dr iven, have

of la te been frequent ly provided wi th direct-connected exciters. In t h e case of t h e ver t ical un i t s , t h e exciter is regular ly moun ted immedia te ly above t h e t h r u s t bear ing a t t h e top of t h e un i t . In several of t h e largest and best known hydraul ic p l an t s exci ta t ion has been provided b y individual motor -dr iven exciters, t h e motors being dr iven from a house genera tor or from the s ta t ion sys tem. As far as t he wr i te rs know, th i s sys tem of motor-dr iven exciters was first in t roduced m a n y years ago in to t h e p l an t of t h e Ontar io W a t e r & Power Co., Canad ian Niaga ra Falls , a t t h e suggestion of M r . J . A. Johnson, who is now t h e electrical engi­neer of t h e Niaga ra Fal ls Power Co. Hence , i t should no t be considered s t range t h a t a new idea has been incorpora ted in th is new 65,000 kv-a . genera tor b y M r . Johnson . A direct-connected a l t e rna to r is used b o t h for t h e purpose of dr iving t h e motor -genera tor set t h a t supplies excitat ion, and also for supplying power t o motor-dr iven auxiliaries.

Outs ide of t he usual m o u n t i n g of th is genera tor , t h e s t a to r being suppor ted or " h u n g " from t h e bear ing bracke t a rms and t h e ro to r bol ted direct ly to. t he ro to r a rms , no unusua l problems of design are invloved.

WORKMANSHIP AND INSTALLATION As a general rule, smaller genera tors of th i s t ype are

completely assembled in t h e factory before sh ipment , t o see t h a t all p a r t s fit t oge the r proper ly , and runn ing tes t s a re m a d e t o de te rmine if genera tor comes wi thin guaran tees . Outs ide of assembling t h e ro to r spider sections, w i t h o u t shaft , and t h e fitting of one or two pole pieces t o de te rmine if pole piece bolt-holes lined up with holes in ro tor spider and t h e assembly of s ta i r ­way and gallery to bear ing bracke t , no a t t e m p t was m a d e to assemble th i s genera tor . N o t w i t h s t a n d i n g the fact t h a t bear ing b racke t m u s t fit s t a to r frame accurately , t h a t all bol t holes m u s t line u p wi th cor­responding holes in connect ing pa r t s , t h a t ro to r spider keyways m u s t line u p accura te ly wi th shaft keyways , and all w i thou t being fitted together , when genera tor was finally assembled in power house for t he first t ime, so accura te ly was all mach ine work done t h a t , t o use the words of t he erect ing engineer, "all p a r t s fitted perfectly and no t even one bol t had to be changed to make the assembly comple te . "

WEIGHTS Stator Frame, Laminations, Windings, Flanges, etc. 470,000 lb. Stator Base Ring 52,500 " Brake Supporting Ring 56,500 " Upper Bearing Bracket 119,150 " Complete Rotor with Shaft 783,110 " Shaft 59,432 " One Rotor Pole & Winding 10,900 " Miscellaneous 32,540 " Complete Total Weight of Main Generator 1,513,800 "

"Excitation 24,592 " "Unit 1,538,392 "

The W R2 is 65,000,000—figures easy to remember in con­nection with a 65,000 kv-a. generator that has excitation auxil­iary of 650 kv-a.

AUSTRIAN RAILWAY ELECTRIFICATION

Among t h e var ious p lans to subs t i tu t e electricity for coal in Aus t r ia , since Aus t r i a is dependent on foreign sources for three-four ths of i ts coal supply, t he de­ve lopment of wa te r power for the electrification of ra i lways is impor t an t . T h e coal needed for all s team-opera ted ra i lways in Aus t r ia is es t imated a t 4,700,000 met r ic tons per year (when oper­a t ing a t full capaci ty) and th is a m o u n t s to a b o u t one-fourth of t h e to ta l coal requ i rements of t he count ry . Over one-half of the a m o u n t of coal con­sumed b y the rai lways can be saved b y the util i­zat ion of electric power, much of which is ye t to be developed.

In view of the present s t a tu s of work the fol­lowing deve lopments m a y be an t ic ipa ted for the nex t two years , according to a s t a t emen t of the electrification division of t he Aus t r i an Federal Rail­ways .

Opera t ion of t h e Innsbruck-Landeck section of the Innsbruck-Telfs line was commenced in Ju ly , 1923, and a t r ia l run was successfully m a d e on the Telfs-Landeck section in December last . T h e Rue tz power p l an t is sufficient for present purposes, b u t extension of operat ions t o Bludenz m u s t depend on the complet ion of t h e Spullersee p lan t . Commence­m e n t of electrical operat ion on t h e line Sta inach-I rdn ing-Bad Ischl of t he Sa lzkammergut lines is expected in the ear ly p a r t of 1924. B y the end of 1924 electrical opera t ion of all Sa lzkammergut lines is looked for.

Commencemen t of operat ion on the line Innsbruck-Bludenz after complet ion of t h e Spullersee p l an t is t o t a k e place in 1925, b u t some of t h e t r a ins are to be r u n b y s t eam.

T h e cost of the ent i re first por t ion of the bui lding p rog ram a m o u n t s to a b o u t 130,000,000 crowns ($26,-000,000) as based on the es t imates of t he 1920 law au­thor iz ing the electrification. Since t h a t t ime, t h e basis of calculat ion has changed to such an extent , owing to t he approach of p roduc t ion and bui lding costs to the world pa r i ty , t h a t t he sum required m u s t be increased b y a b o u t one- third. T h e to ta l costs are equal ly dis­t r ibu ted be tween the Arlberg line and the Salzkam­mergu t lines on the one hand , and the T a u e r n rai lway and the s t re tch from Salzburg to Woergl on the other .

Upon complet ion of the contempla ted building act ivi t ies , 270 ki lometers of Aust r ian federal rail­way lines (excluding pr iva te lines operated by the Government ) will be electrified b y the com­mencemen t of 1925. Par t i a l electrical operat ion will resul t in a considerable economy of coal, as t he saving for 1924 alone is es t imated a t 25,000,000,000 crowns, or $360,000. F u r t h e r progress of the work will depend on the financing of the building p rogram.