CA1050599A - Ventilation system for dynamoelectric machines - Google Patents

Abstract

VENTILATION SYSTEM FOR DYNAMOELECTRIC MACHINES

ABSTRACT OF THE DISCLOSURE
A ventilation system is provided for dynamo-electric machines such as hydro generators having salient pole rotors and in which the rotor and stator have sepa-rate ventilation systems sealed from the air gap, The stator ventilation system includes radial vent ducts with longitudinal ducts in the stator core extending between adjacent radial vent ducts. The longitudinal ducts are sealed from the air gap and are disposed in the region of the stator windings, preferably extending through the teeth.
Ventilating air flows radially inward through the vent ducts, longitudinally through the longitudinal ducts from one vent duct to the next, and radially outward to the external circuit where it is circulated through coolers, by means of a blower or otherwise.

Description

BACKGE~OI.~D OF THE I~JENTION
The present inventlon rel~tes to a ventllatio~
system for dynamoelectric machines, and more particularly to cooling the stators o~ large machines such as hydro generators.
Hydro or wate~heel generators are vertical machines of large physical size with salien~ pole rotors, snd rotate at relatively low speeds as compared to other types of generators although the peripheral speed of the rotor may be qui.te high because o the large di~meter.

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These machines are cooled by circulation o~ air and two ~ypes o~ cooling systems have conventionally been used.
In one system, the air is circulated by a blower, which may be mounted on the rotor, and is directed to flow axial1y through the spaces between the salient poles of the rotorO The air flow~ axially in the interpolar spaces to cool the field windings and poles and the~ flows radially into ~he air gap and acrvss the air gap to the stator. The stator core has radial vent ducts extending ~hrough it and : lO ~he cooling air crossing the air gap flows through these ducts to cool the stator windings and corea and is d-s-charged at the back o~ ou~er periphery of the oore and , recirculated after flow~ng through eoolersO The other cool~
ing system, which has come into use more recently, uses the rotor spider and rim as a blower to cause the air to flow radially through ~uc~s ln the rotor rim and thus into the in~erpolar spaces ~rom which i~ ~lows radially across the air gap and through the stator core radial vent ducts as ~.
described above. In both of these schemes, therefore~ ~he .
air rotates with the ~otor as it flows into and across the air gap. Fur~hermore, the same air lows in series ~hrough the ro~or and ~e stator co~e, and the mass flow rate of air must be adequate to cool bo~h the rotor and stator su~ficiently to keep the temperature rise within the re qulred llmits. Thus, a lar~e flow of air is necessary and ~he rotation o~ this l~rge mass of air at or near the

-2-, perlpheral speed o~ the rotor results Ln high windage losses .

The present trend in hydro m~chines, especially in tho8e intended or alternative operation as generator~

and as motors in pu~ped storage installa~i~n3, is to m~Lchines of large size and rela~ively high speed. The combination of large ro~or diameter and ~igh speed results in very h~gh peripheral velocities o the rotor which m~

be i~L excess of lS,OOO ~eet per m~nute, or exampleO Wlth the conventional ventila~ion schemes discussed above, the windage loss i~ quite high and becomes a relatively large percentage of the total loss in ~che m~LChine. A reductlon i the w~ntage loss ~ereore can result in a very substan~

: reduction in the total losses, Wit~L a correspondlng increase in efficiency, or a reduction ~n ~Le size o~ t~ ~L^hine : w~th a substant~al saving in cost.

It ha~ been proposed ~o grea~ly reduce ~he wind-age los~ in n~LChlneS 0~ th~s type by separatlng the rotor and s~ator air flows lnto separate ven~ilation s~7stems and ZO sealing off the rotor air ~low ro~ the air gap, as in ~:~

~Cilgore e'c al Patent 3,588~557. Thi8 r28ults in a sub-8tantial reduction ~n the windage 10B~ since most o~ the rotor cooling alr 18 confined to the ro~cor and prevented from reachlng 'che 8ir gap a~ only enou~h air is allowad ~o flow into the alr gap to remave the heat resul'cing rom the pole ace lo~ses. Sepa~a~ion of the rotor and s~ator ~3~

~ 52 ~ ~S~9 air flows also grea~ly reduces the volwme of air required~
In the conventional cooling schemes, the stator cooling air flo~s ~irst through the ro~or and then across the air gap so ~ha~ is heated by the rotor losses before it reaches the stator. In order to obtain the necessary cooling o~ th~ s~ator, therefore~ a relatively large flow - of air is required~ When the stator air flow is separa~ed from the rotor air flow, however, cold air enters the - stator so that the volume of air required for cooling the stator is reduced and the total air flow in the machine ls greatly reduced. Since the stator air flow is largely independent of the rotor air 1ow, and smaller fLow rates of cooler air can be used for cooli.ng the stato~, an . opportunity exis~s for ~ur~her improvemen~ ln cooling by new s~ator ventilation systems.
: SU,M~A~Y OF THE I~VE~TION
; : T~e presçnt invention provides a new and improv-ed ventilatlon system for the stators o~ large sal~ent pole dynamoelectr~c machin2s in which the rotor Qnd ~he stator have separate air flows which are 8ealed o~f from the alr ~ap.
; Since the stator cooling air is no~ supplied by air flow across the ~ir gap, the direction of air flow in the stator core L. reversed, with respec~ ~o conventional 8ystems, and air flows from the coole~s directly to the Btator corç and is introduced through the back, or outside, ' . .

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o~ ~he core to flow radially inwarda The rooling air f~ows inward through radial vent ducts in the s~ator core to the region of the teeth and windings and is there directed to flow axially in longitudinal duc~s in the coxe. These longitudinal ducts are sealed off rom the air gap, so that ~he air does no~ reach the air gap, and it flows ~rom one radial vent duct to the next through ~he longitudinal ducts and then radially outward to the back o ~he core through ~he adjacent vent duct. The longitudinai ducts are disposed within ~he core in the region of the slo~s and stator winding for the maximum cooling effect3 and may com-pxise axial openings or slits in the teeth forming longi-tudinal passages extending between the radial vent ducts.
Cold air thus flows directly from the cooler thro~gh the core to ~he region of the wi~dings and re~urns direc~ly to the blo~er and cooler so that greatly lmproved cooling of the stator is obtained with a smaller vo~ume o~ ai~, The air may be circuLated by a blower o~ an~
de~ired type ~hich may be carried on ~he ro~r ~f the ~0 machine, or which may comprise an external blower or blo~-; er~, and the air ci~culates in a predetermln~d pa~h through khe ~tator, the blower and the necessary coolers. The longitudinal ducts extend from one end to the other of the stator core and communicate with the radial vent duc~s.
The air paths through the longitud~nal ducts, however, extend only ~rom one vent duct to the next, so that the ~5~ .

e 45,852 5~ffl len~th o~ e~ch individual air path in the machine is rela~ively short. For ~his reason, the pressure drop incurred in ~orcing the air through ~he sta~or core is relatively 1~J~ Since ~he total mass ~low of air required ls very much lower ln this system than in convent'onal systems, and since the pressure drop in the system is lower, the total pumpin~ power required to maintain ~he air cir-culation is very much reduced, as compared ~o previous systems, wi~h a subs~an~ial fur~her improvement in efi- :
ciency o~ ~he machine in addition ~o the improvement due to reduc~ion in windage loss and improved cooling.
BRIEF DESCRIPTION OF ~H~ DRAWI~IG5 : The invent~on will be more fully un~ rstood from ~ the ollowing detailed description, taken in connec~ion ~., : wi~h ~he accompanying drawings, in which:
~: Figure 1 is a vertical sectio~al view of a l~rge : dynamoelectric machine embodying the invention, Fig. 2 is a ragmentary plan view of the rotor and stator of the machine of Figo l;
Fig. 3 is an enlarged ver~ical sec~ional view o~
the stator core of the machine, ~ :
Fig. 4 is a fragmentary plan view o-~ a por~ion of the s~ator core;
Fig. 5 is a somewhat diagrammatic perspective view o a portion o the stator core showing the air ~low through the ducts of ~he core; and . .

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~ 5g 9 - -Fig. 6 is a diagrammatic perspective vlew fur-ther illustra~ing the air 10w of Fig. 5 DESCRIPTION OF TME PREFERR~ ~ODT. ~
The invention is shown in the drawings embodied in a large, vertical, hydro machine suitable ~or use as a w~ter~heel driven generator or as a genera~or motor for pumped storage power projects. The machine has a vertical ~hat 10 earrying a rotor member.l2 for cooperation with stator 14 which is supported on a foundation 16 of any sul~
10 able type. The shaft 10 and rotor 12 are supported on a ~-~
thrust bearing (no~ shown) of usua]L type and the overall construction of ~le machine may be of any usual or desired type : The rotor 12 consists of a spider portion 18 moun--ted on the sha~t 10 and which may be of any sul~able or us~l construction. A lam~nated rim 19 ls carried on the spider .
port~on 1~ and sal~ent poles 20 carrylng field wlndLngs 2 are mounted ~n the usual manner on the rim 19. T~e ro~or 12 may be o any suitable construction and i~ cooled by it~
own ventila~ion system separate from tha~ o~ the stator~ the rotor air flou being sealed off from the air g~p between ~he xotor and stator, as d~.scussed above. For the purpose of ; illustration, the rotor 12 ~s sho~m as being of a type dis-closed in the above-mentioned Kilgore et al pa~ent. As ~ho~m ln Fig~ 2, pastitions ~22 extend axially thro~lgh each of the interpola~ space~ and have flanges 23 which engage -7- .
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the adjaoent pole faces ~o seal the interpolar spaces from the air gap. The rotor ls cooled by air flowing through the spider and flo~7i.ng a~ially through the interpolar spaces, as ~ndica~ed by the arrows in Fig. 1, and as more ~ully described in the above-mentioned pa~ent.
The stator 14 comprises a lamina~ed st~tor core - 24 supported between end plates 25 in a frame 26 of any suitable con~truction supported on the foundation 16. The stakor core 24 is of t~e usual laminated construction pro-10 viding spaced radial ven~ ducts, as more fully described : -hereina~er, through which air may ~low radially of the ; core. ~entila~ing air may be circula~ed throug~ tbe machin~
by any desired mea~s ~hich is sho~ as a centrifugal bLower consisting of a plurality o~ blades 27 mounted on the rotor, Air flows ~rom the blower in the paths ind~cated by the axrows and through coolers 28 which may be of usual ~ype, any nPcessary ~mber of such coolers being provided abou~
the circ~mference o ~he machine. The air flo~ing through the coolers i5 directed lnto sultable ducts ~r passage through the stator core 24 and, upon discharge from the stator coxe, is dlrec~ed through the coolers 29 and dis- ~ :
charged for recirculation by the blower and by the rotor 12.
It will b~ understood that any suitable type of blower may be used mounted on the rotor as shown~ or the necessary ~umber o~ ex~.ernally mounted blowers might be used ~o elr~
culate the air ln any de5ired path through coolers and the -8- .

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45,852 1615~)59~9 necessary ducts to and from the stator core.
As shown more particularly in Figs, 3 and 4, the stator core 24 is of lasinated construction and is built up of the usual punchings 30 to form a cylindrical core having a central ~ore t~l~rethrough wlth teeth 31 extending lDngi-tudinally of the ~ore to form slots between them for the recep~lon of stator windings 32. The stator punchings 30 may be of usual ~ype having recesses 33 at the outer pexi-phery ~or reception of building bolts 34 on ~Jhich the core is supported in the ~rame 26, and if desired openings 36 may be provided in the punchings to form axial ducts 37 through ~he core for passage o ventilating air. The stator core 24 is provided w~-th a plurality of ]Longit.ud?:nall~T-sp~ced radial ven~ ducts 3~ extendlng radially through ~he core ~rom the cen~ral bore to the outer periphery. The ~ent duc~s 38 are provided by a~taching spacing ~ingers 39 to certain o the punchings 30 a~ the desired intervals in the ;( core to space the adjacent punchings apart and thus ~orm radial ~uc~s 38.
The spacing ~ingers 39 also serve as air guides, and in the embodiment of the inveneion shown in Fig. ~, ~he ~ingers 39 exten~ radially o~ the punchings and have openings in them indicated at 40 Ehrough which air may flow to the tooth region. The teeth 31 have elongated duct openings or sl~es 41 formed in tlem extending over m~st o~ the radial length of the tooth so that ~hen assembled in the complete _9_ ' ' . ' , .

~iS,~52 , 5~ ~ -core, the slits 41 form longitudinal duc~s. These ducts ext~.nd for the ull axial length of the teeth from one end of the core to ~he other, and thus ~xtend betwe~n adjacent vent ducts 38 ~Jith ~Jhich they are in co~raunica- -tion, Seallng means are also provided to seal the air flow path ~rom the air gap and prevent th~ escape of any appreciab~ amount of air. As shown in Fig. ~, sealing me~ibers 42 may be provided or thls purpose adjacerlt the tips o~ the teeth 31 and across the bottom o-~ the wind~ng slots. The seallng members 42 may be rigid bars recei~ed .
in slots in the adjacent spacing fingers 39 so ~hat the -s ven~ duct 3~ is ef~ect vely sealed off f~om ~he ~ir gap, In operation, ventilating air flows through the core generally as shown ~y the arrows in Fi~6, 3 and 4. In this particular embod ment, alternating cold air ducts 43 ; and warm air duc~s 4~ ar~ provided in th~ area immed~a~ely :`~ ad3acent the back of the sta~or core. Cold air from the coolers 28 is directed into the cold air ducts 43 and flows into alternate vent ducts 38 and radîally inward throug~
the core to the ~ooth region, the spacers 39 acting as , guides to direct the air. The ducts 38 are sealed at the air gap as described above and the air flowing inward is forced to chan~e direction and flow longitudinally into j th~ ducts 41 ~ich ex~e~d through the teeth. The aîr thus flows longitudinally in opposite directions in these duct8 to t~e next adjacent vent duct 38 on each side where 10- , '.

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opposing air streams meet~ The air then again changes direction and flows radially outward through the vent duct to a warm air duct 44 at the back of the core from which it is directed through the coolers 29 and back to the blower.
In the embodiment of the invention just described, the ventilating air flows radially inward through alternate vent ducts 38 and outward through the remaining ducts. This ~; requires the provision of alternating cold air and warm air ducts extending around the outside of the core which may, in some cases9 be undesirable. ~nother arrangement is shown in ~`igs. S and 6 which may result in a simpler arrangement of ductw~rk in many cases. The stator core 24 there shown ~; is essentially the same as that described above. The vent ducts 38 are formed in the same manner by spacers 45 attach-ed to the punchings at intervals and the longitudinal ducts 41 extend through the teeth 31 as previously described. In this embodiment~ the radially inner ends of the vent ducts are sealed by wedge members 46 fitting in the vent ducts between the tooth t-lps and having curved surfaces to facili-tate the change in direction of the air. The usual slot wedges 47 which retain the winding coils are used to seal the slots so that the vent ducts 38 are sealed off from the air gap as before.
In this embodiment of the invention, each vent duct 38 is divided into a plurality of circumferential zones cor-responding in extent to the spaces between ad~acent building bolts 34. These circumferential zones are alternately inlet s~
zones and discharge zones for the coollng air, as indica~ed by the arrows in Fig. 5, which in many cases results in a simpler arrangement of cold air and warm air ducts, although any suitable arrangement of ducts may, of course, be used.
In order to accomplish the desired air flow, the spacers 45 are radial in the tooth portions of the core and are bent to extend at an acute angle to the radial direction through the rest of the oore. The spacers 45 of adjacent vent ducts are inclined in opposite directions with respect to the radial as can be seen in Fig. 5.
; The resulting air flow paths are shown diagram-matically in Fig. 6 in which one flow path is shown by solid arrows and another flow path is shown by dotted arrows, three of the circumferential zones being shown. Thus, air , entering the front or forward duct of Fig. o in the center zone (solid arrows) i5 shifted to the left by the in-clined spacers 45 and flows to the teeth where it enters the , longitudinal ducts 41. The air flows in both directions .~
- through these ducts, the rearward flow being shown. When the air reaches the next adjacent (rearward) vent duct 38 it meets oppositely f-lowing air and both streams flow radially outward into the vent duct. Since the spacers 45 in this duct are oppositely inclined, they shift the air farther to the left and it is discXarged through the left-hand circumferential zone of Fig. 6. The path of air enter-ing the rearward vent duct in the center zone is shown by .'' ,.. ..
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the dotted arrowsO This air flows oppositely to the previously-described air flow and is shifted to the right by the spacers 45 to discharge from the forward vent duct through the right~hand ~one.
It will be seen that in both embodiments of the invention, the stator core and windings are cooled by air flowing in a path which is sealed from the air gap and separate from the rotor cooling air path. Cool air flows radially inward from the back of the core, longitudinally through ducts closely adjacent the windings where the greatest amount of heat is generated, and radially outward to be discharged through the back of the core. The length of each longitudinal duct between adjacent radial ducts is relatively short and air flows through the core in many ` short paths in parallel. This results in a relatively smallpressure drop across the core so that the fan pressure dif-ference required is relatively low. Since the air is cold as it enters the stator core and is required to absorb only the heat generated in the stator, a much smaller volume of aIr is required than was necessary in previous ventilation systems in which the air flowed first through the rotor and then across the air gap into the stator so that the air was first headed by the rotor9 The small volume of air required, together with the relatively low pressure drop across the core ducts~ results in a great reduction in the pumping power required to circulate air through the machine as compared to .

'.:,, conventional cooling systems, with a corresponding increase in efficiency, while the improved cooling permits an in-crease in rating of the machine or a decrease in size.
It will now be apparent that a greatly improved cooling system has been provided for salient pole machines in which separate cooling systems are provided for the stator and rotor. The new stator cooling system disclosed - herein results in a very marked improvement in the stator cooling~ and a reduc~ion in pumping power required~ with a substantial improvement in efficiency. It will be under-stood, of course, that various modifications and embodiments of the invention are possible. The longitudinal ducts may be arranged in any suitable manner within the core where they can be sealed from the air gap and disposed in the immediate region of the winding slots and windings. The external air circuit outside of the stator core may be arranged in any desired or suitable manner to cool and reclrculate the air.

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Claims (12)

What is claimed is:

1. A dynamoelectric machine having a stator member and a rotor member separated by an air gap, said rotor member having salient poles and a ventilation system sealed off from the air gap, said stator member including a cylindrical stator core having a central bore with teeth extending longitudinally of said bore to form slots for stator windings, a plurality of longitudinally-spaced vent ducts extending radially through the core, a plurality of longitudinal ducts in the region of said slots extending between said vent ducts, said longitudinal ducts lying within the core and being sealed from the air gap, and means for causing ventilating air to flow radially in said vent ducts and longitudinally in said longitudinal ducts from one vent duct to the next.

2. A dynamoelectric machine as defined in claim I in which said longitudinal ducts extend through said teeth.

3. A dynamoelectric machine as defined in claim 2 in which said sealing means includes barrier members across each of the vent ducts adjacent the radially inner ends of each tooth and adjacent the bottom of each slot.

4. A dynamoelectric machine as defined in claim 1 in which ventilating air entering the core flows radially inward in a vent duct, longitudinally in said longitudinal ducts to the next adjacent vent duct, and radially outward in said next vent duct.

5. A dynamoelectric machine as defined in claim 4 in which ventilating air flows radially inward in alter-nate vent ducts and radially outward in the remaining vent ducts.

6. A dynamoelectric machine as defined in claim 4 in which each vent duct has circumferentially alternating zones for inward and outward air flow, the air flowing in each of said inward zones flowing longitudinally through a longitudinal duct and to an outward zone of an adjacent vent duct.

7. A dynamoelectric machine as defined in claim 4 including blower means for causing said ventilating air to flow through the stator core and for causing air to flow in a separate path through the rotor member.

8. A dynamoelectric machine as defined in claim 7 including cooler means disposed in the path of said air flowing through the stator core.

9. A stator member for a dynamoelectric machine including a laminated cylindrical stator core having a central bore with teeth extending longitudinally of the bore to form slots for stator windings, certain of the lamina-tions of the core having spacing means thereon to form vent ducts extending radially through the core at spaced intervals, a plurality of longitudinal duct means in the core extending between adjacent vent ducts in the region of said slots, and spacing means being disposed to define flow paths for ventilating air flowing radially in said vent ducts and longitudinally in said longitudinal duct means, and means for preventing flow of air between air ducts and said bore.

10. A stator core as defined in claim 9 in which said longitudinal ducts extend through the teeth from one end of the core to the other, and including barrier means in said vent ducts for effectively sealing the ducts from the bore.

11. A stator core as defined in claim 9 in which said spacing means direct ventilating air to flow radially through said vent ducts and longitudinally through said longitudinal ducts from one vent duct to the next adjacent vent duct.

12. A stator core as defined in claim 9 including a plurality of longitudinal bolts on the outer periphery of the core for supporting the core laminations, said bolts being circumferentially spaced and dividing each vent duct into a plurality of circumferential zones, said spacing means defining flow paths for air entering the core through alternate zones of each vent duct to flow radially inward to said longitudinal ducts, through the longitudinal ducts to the next adjacent vent ducts, and radially outward through alternate zones of said adjacent ducts.