The 65,000-kv-a. generator of the Niagara Falls power company

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<ul><li><p>The 65,000-Kv-a. Generator of the Niagara Falls Power Company </p><p>By W. J. FOSTER Fellow, . I. . E. </p><p>AND A. E. GLASS Both of the General Electric Co., Schenectady, . Y. </p><p>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 </p><p>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. </p><p>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 . </p><p>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 </p><p>To be -presented at the Spring Convention of the A. I. E. E.t Birmingham, Ala., April 7-11, 1924-</p><p>is low per iodic i ty ; th i rd , i t was designed for t he highest economic efficiency. </p><p>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 . </p><p>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 . </p><p>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 , - R -and load losses. T h e mos t i m p o r t a n t factor in </p><p>3 6 5 </p></li><li><p>3 6 6 FOSTER A N D GLASS: 65,000-KV-A. GENERATORS Journal . I. . E. </p><p>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. </p><p>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 . </p><p>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 </p><p>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 -</p><p>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 </p><p>0 1000 2000 3000 . 4000 5000 6000 AMPERES ARMATURE </p><p>FIG. 2 F I E L D CHARACTERISTIC CURVES A 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 . BBi 80 " " " " 12 ,000 " 65 ,000 k v - a . C C i 80 " " " " * 13 ,200 " 6 8 , 2 5 0 k v - a . </p><p>AMPERES FIELD </p><p>FIG. 1 T H E 6 5 , 0 0 0 K V - A . GENERATOR OF THE NIAGARA FALLS POWER Co. </p><p>Sa tura t ion C u r v e s AOpen Circu i t 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 " " </p><p>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. </p><p>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 . </p><p>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 . </p><p>T h e fact t h a t th is genera tor is, for t h e t ime being, t h e </p><p>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 . </p><p>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 </p></li><li><p>April 1924 FOSTER A N D GLASS: 65,000-KV-A. GENERATORS 367 </p><p>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 machins . </p><p>STATOR </p><p>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 </p><p>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 </p><p>FIG. 3 C R O S S SECTION OF ASSEMBLED GENERATOR </p><p>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 . </p><p>STATOR CORE </p><p>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 </p><p>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. </p><p>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 . </p><p>STATOR W I N D I N G </p><p>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 , </p></li><li><p>368 FOSTER A N D GLASS: 65,000-KV-A. GENERATORS Journal . I. . E. </p><p>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 </p><p>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...</p></li></ul>

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