CA1119225A - Rotor laminae assembly for a cast rotor dynamoelectric machine - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A rotor assembly for a dynamoelectric machine is characterized by incorporating three different sets of rotor laminations each of which is provided with punched apertures that respectively form conductor slots arcuately spaced around the periphery of the laminae, a plurality of axial coolant passage-ways extending through the assembly near its inner diameter, a plurality of arcuately spaced radial ducts at axial intervals along the rotor, and vent passageways connecting the radial ducts to the axial coolant passageways to enable cooling air to be forced through the coolant passageways and the vent apertures into the radial ducts and thence into the air gap of the machine when the rotor is assembled in operating position. The rotor of the invention is particularly characterized by incorporating radial cooling ducts that extend between each adjacent pair of conductor slots from the periphery of the rotor to points substantially below the bottoms of the conductor slots in the rotor laminae. All of the laminae are stacked in aligned position and compressed to form tight seals therebetween that prevent molten metal from flowing out of the conductors slots into the interstices between the respective laminations of the assembly during rotor casting operation.

Description

9~25 ¦ 21-GM-284 l l ..
ROTOR L~MINAE AS SEMBLY FOR A
CAST ROTOR DYNAMOELECTRIC MACHINE

. Back round of the Invention g The ~nvention relates to rotor laminae assemblies for cast rotors used in the manufacture of dynamoelectrlc machines and m~re particularly it relates to ~uch a rotor having radial cooling ducts connected tD axial coolant passageways through the rotor asse~bly in a manner that enables rotor conductors to be cast in conductor slots of the assembly without impairing the cooling ducts or axial coolant passageways. Ihe invention also makes it possible to cast the conductors of a rotor assembly ~ithout requiring the use of spacer pins,or spot welded collar sub-assemblies, separately inserted into the laminae assembly of the rotor during a casting ; operation to prevent the flow of ca~ting metal from the conductor 910ts into cooling ducts of the assembly.
Prior to the present invention lt was common practice to cast conductors in,laminated rotor assemblies for dynam~lectric machines by utilizing variousi types o~ ~ipacersi to prevent lten mRtal from entering the roto~ a~r ducts during the oasting operation. For example, U.S. Patent No. 2,368,296 diisolosie~ a method of ~orming radial ventilating passages in a cast rotor in which . , ..,...

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~ 21-GM-284 ring-shaped spacers are inserted between groups of laminations during the casting operation. After such a castin~ operation the rotor assembly is further I treated to melt or dissolve,the temporary spacers ~o S ¦ they are easily rem~ved from the rotor. In that patent ¦ * e use of tin alloy, plaster or clay with a dissolvable bindex is su~gested for the ring-shaped spacers. The same inventor discloses in U.S. Patent No. 2,368,295 the use t of cardboard or similar combustible material to form spacers in a rotor lamination during a casting operation.
Similarly, in V.S. Patent No. 2,607,968 there is described a method for casting dynam~electric machine rotors with air ducts whlch are formed by spacers made of reinforced plaster material between the lamination sections of the ~ rotor during a casting operation. Following the casting procedure, the plaster m~terial i8 di~integrated by oontacting it with water to wash the spacers from the air ducts.
Although the u~e of such dissolvable or frangible spacex materials i8 well-known, it is more commDn ~; practice in the manufacture of relatively large dynamo-ele~tric machine rotors to place a plurality o~ removable ~ steel pins, or spot welded collar sub-assemblies, between ; section~ of the rotor laminatlons to form the desired cooling ducts in the rotors. The u~e of such a reusable ~pacer procedure i~ shown, for example, in U.S. Patent No. 2,504,824.

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While the utilization of metal pins to ~orm air ducts in cast rotor~ ha~ become a preferred practice in the manufacture of dynamL~electric machines, relative to the use of frangible or dissolvable spacing memkers to form th~ cooling ducts, it ha~ long been recognized that this method inherently has several disadvantages.
In practicing this method it is necessary to utilize a relatively large number of individually placed steel pins to foxm the cooling ducts in a given r~tor. Typically, the number of such pins will be around 1,000 for a medium size rotor, i.e., a mttor about 3 feet in length and 2 ft. in diameter. Since these pins must be ¦
¦ individually positioned ln the rotor as its lamination assemktly i~ built up prior to a castiny operation, and since the pins must subsequently be individually extracted from between the laminations following the casting operation, the labor cost involved in this method is substantial.
In addition to the installation and remDval of the pins, care must be taken to carefully clean the pins between each use to asRure their close preci~ion fit in subsequent casting operationF. so that molten metal does not flow .etween them and the adjacent rcttor laminations. M~reover, the noxmal u~e and handling of ~uch pins ltnevitably results j ~n mechanical abu~e and wear that necass~tates frequent replacement of the pin3. Of course, ~uch replacement costi are a substantial manufacturing expense that it ¦¦ w~u1d be desi~le to ~void, i~ poRsible .
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¦ Well before the development and commercialization ¦¦ of such rem~vable ring or pin t~chniques for casting j conductors in laminated roto~s, it wa~ known to fabricate I laminated rotors of a series of di~ferently punched S ¦ laminae arranged to form axial coolant passageways ¦ connected to radial coolant ducts by venting channels.
An example of several early configurations of that type of ventilating arrangement in a wound rotor structure is shown in U.S. Patent No~ 890,577 which issued on June 9, 1908~ However, since such early rotor cooling arrangements were not suitable for use in manufacturing cast conductor rotors, due to the fact that they would allow m~lten conductor metal to enter the coolant passageways therein, it remains common practice ~o manufacture rotors having lS ca3t conductors by the aforementioned movable spacer-pin methods .
:` In m~re recent times, as shown in U.S. Patent ~o. 3,684,906, which issued on August 15, 1972 to one o~ the applicants named herein, a relatively ~mall castable rotor for refrigerant compres~or motors was disclosed in which a plurality of ~ets of differently oonfigured rotor lamina~ wer~ arranged to form bortuous : paths through the rotor ~rom arcuately spaced axial rofrigerhnt-carrying passageways, th~ough intermediate vent pas~agaways, to arcuately dispo~ed-radial ducts.
Such small refrigerant compressor mobors are distinguished from the pres t lnventlon by r-qu- rlng the u~e of r.~dlal _4_ lll9Z2~i j coolant ductis in two different set~ of laminations ¦ ~o that the radial ducts in either such set do not . extend the full depth of the ~djacent oonductor 810ts.
Furthermore, the ~low-restripting nature of the small, tortuous ducts used to carry refrigerant through such rotors are not suitable or use a~ coolant passageways for larger air-cooled rotors in which large volumes of air must be ved through the rotor ducts with little pre~sure 109s.

Objects of the Invention Accordingly, it i8 a primary object of the present invention to provide a rotor laminae assembl~ for a dynamoelectric machine having cast rotor conductors and spaced radial cooling ducts connected to axial coolant pa~sageways, by ad~oining apertures in a plurality of differently shaped laminaer in an as~embly that i~ more economical to manufacture and efficient to operate than those heretofore known.
Another object of the inVention is to provide a la~ina~ed rotor ai~sembly having cast conductors in combination with radial oooling ducts that are ormed tD extend past the entire radial depth of each ad~acent cDnduc~or slot and on into the central venting pa~sageway ¦ Fo~i~ oi ~he ~embly~

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!1l lll9Z25 ¦ Yet another object of the invention i9 to provide a ¦ cast-rotor laminae assembly,for a dynamoeloctric machine ¦ having three sets of differePtly oonfigured rotor lamina-¦ tions arranged in recurring,patterns to provide arcuately and axially spaced coolant ducts extending from the periphery ~f the rotor past the entire length of the conductor slots into overlapping relationship with venting ;
apertures in adjacent laminae, which in turn are. in communication with axial coolant passageways ormed through the main rotor laminations.
A further object of the invention is to provide a cast-rotor assembly having an efficient cooling system that re9ults in the rotor having added heat storage ¢apacity which increases the stalled time capability of ~ 15 the rotor.
- Additional objects and advantages of the invention ', will be apparent from the description of it presented below ;
considered in con~unction w~th the accompanying drawings.
.. .' Sumnary o the Invention In one preferred embodiment ~ rotor laminae assembly having cast condu~tors is provided with a plurality of spaced radial oooling ducts that extend from the periphery of the rotor to points well below the bo~tons of adjacent cDnductor slots. ~rhe c~oling duct~ axe formed by punching

2~ a fir~t set o~ rotDr laminae ln a predetermined pattern that includes coolant slo~ punchings, as well as conductor ,. ' i 'i , ~ ., ,, 1.

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l l 1 slot~i and aperture5 that form part of the axial cooling ¦l air passageways through the assembly. A differently configured set of vent lamin~ae are punched to form ~ conductor slots therein and,a plurality of arcuately ~ spaced vent apertures that are arranged to be positioned in overlapping r~lationship with both the axial coolant passageways in the first set of laminae of the assembly and with the inner portion of predetermined cooling ducts.
These two sets of laminae are arranged in recurring patterns with a third set of main rotor laminae that are punched to form a plurality of conductor slots and a plurality of apertures that form axial cooling air ; passageways through the assemhly. m e laminae are all B stacked with their respective conductor slots in alignment, and compressed together in fluid ~c relationship so that nPlten metal cannot flow between adjacent lamina ~rom the conductor slots into adjacent cooling ducts.
Electrical conductors are cast in each of the conductor slots and a pair of integrally cast annuli are formed around the outer portions of the two end-m~st laminae to interconnect all of the conductor bars in a well-known manner. After the conductox bars and end annuli have been forme~ on the rotor laminae assembly, the outer perip~eral surface of the cooling duct laminae are machined away to open the outer ends of the cooling ducts. m us, I cooling air can be forced through the axial cooling ¦ pas~ageways in the main rotor laminae into the large vent ! `

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¦ apertures of the intermediate laminae and sent, with ¦¦ very little pressure drop, into the radial cooling ducts and out of the rotor into an~adjacent gap, between it I and a-stator, when the rotor is press fit or otherwise S ! supported on a suitable shaf~t and mo~nted for rotation within such a stator in a manner well-known in the art.

Brief Descri tion of the Drawing _P

FIGURE 1 is a side elevation, partly in cross-section, illustrating the upper half of a dynamoelectric machine ha~ing a cast-rotor and laminae assembly constructed pursuant to the present invention.
FIGURE lA is an enlarged, fragmentary, side elevation of part of the machine shown in Figure 1 illustrating the details o~ one group of three different types of laminations used to form the cooling passageways and ducts of the invention.
FIGURE 2 is a top plan view of a fragment of a main ~otor lamination for the laminae a~sembly shown in Figure 1.
FIGURE 3 i~ a top plan view of a ~enting lamina for the laminae a~sembly shown in Figure 1.
FIGURE 4 is a top plan view of a fragment of a cooling duct lamination for the ro~or laminae assembly of F~gure 1.
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. '', ¦ FIGURE 5 is a top plan view of a fragment of a ¦ cooling duct lamination that can be used instead of the laminae of Figure 4 in maki~g the rotor assembly of Figure 1.

De~cription of the Preferred Embodiment To facilitate a clear under~tanding of the present invention a rotor laminae assembly 1 constructed pursuant to the teaching of the invention is illustrated in Figure 1, mounted in an otherwise conventional dynamoelectric machine for rotation relative to a stator 2 and housing 3 thereof. The stator 2 is wound with a conventional winding 4 while the rotor 1 i8 provided with a plurality of cast conductors arranged in arcuately spaced axial I -conductor slots adjacent the peripheral surface there~f in a manner that will be mDre fully described below.
These axial conductors of the rotor 1 are interconnected at the opposite ends thereof b~ a pair of cast annuli 5 and 6, seen in cross-section in Figure 1, A ~uitable steel ~haft 7 is press fit or otherwise nDunted in fixed relation-ship within the laminae assembly of rotor 1 and is mDunted for xotation on a pair of rolling element (or slidinq element) bearing assemblie~ 8 and 9I which in turn are mDunted in a conventional mænner in suitable hubs 8a and 9a in the housing 3. Also mounted on the shaft 7 are a pair of fans 10 and 11 that fo~ce air over the end windings.
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¦ 21-GM-284 . , ', ¦ Air passes through opening~ in these fans inbo the I opposite end~ of a plurality of axial coolant ¦ pas3ageways one of which i8 ,designated by the numeral 12 ! in E'igure 1, as sh~wn by the arrows enterin~ the ¦ pas~ageway 12. These fans may be mounted in any conventional manner such as by the mDunting bolt~ lOa and lla shown in Figure 1 or by being press fit on the shaft 7. Alternatively, suitable fans may be integrally cast with the annuli 5 and 6, as is well-known.
In alternati~e forms of such machine~ fan~ are cast integral with the rotor end rings or annuli S and 6 to project axially outward therefrom~ In such an alternative ~an arran8ement as well as in the arrangement shown in Figure 1, the oooling air pre~sure head which draws the air into the ducts (12, etc.) i8 produced by centrifugal force in the radial ducts of the rotor.
As will be more fully explained below, an advantage of the in~ention is that the radial duct~ are longer than the cast rotor l:ars, ~o produce a greater head pressure and ind~ce more air flow to improve cooling of the rot~r and stator.
Before describ~ng the uni~ue features o~ the rotor l~mi~ae a~sembly 1 in gre~ter de~ail with xeference to ¦¦ Flgur~ t 3 criptlon wlll b,3 glven o~ the Al~ ting~l:hlng ' -10-. ,, , ' ' ' . I

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l~i9Z25 21-GM-284 features of the three different sets of laminae used in the assembly, as they are illustrated, respectively, in Figures 2, 3 and 4. Considering first the main rotor lamina 13 shown in Figure 2, it will be seen that this lamina is formed with apertures that respectively define a plurality of conductor slots 14, 14a, 14b, etc. that are arcuately spaced adjacent the periphery of the lamina.
Other apertures in the lamina 13 form a plurality of coolant-receiving passages 15, that are arcuately spaced around the inner portion of lamina 13 between the inner ends of the conductor slots 14, 14a, etc. and the inner diameter 13a of the annular lamina 13.
It will be understood that in the rotor laminae assembly 1 shown in Figure 1 there will be a plurality of the substantially flat, annular main rotor laminae ; substantially identical to the lamina 13 shown in Figure 2, arranged in the novel manner of the invention which will be more fully described below. In addition to the conductor slot apertures and the axial coolant-passageway-defining apertures formed in the main rotor laminae, each of these laminae, such as the lamina 13, is provided with a slot 16 punched in its inner diameter edge 13a to provide a means for quickly aligning respective sets of the laminae when they are stacked preparatory to having conductors cast in the conductor slots 14-14b, et cetera.
In Figure 3 there is shown a fragment of a substan-tially flat, annular vent lamina 17 that is provided with B

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apertures arranged pursuant to the invention to define respectively a plurality of conductor slots 14', 14a', 14b', etc. which, it will be understood, are substantially identical in configuration to the conductor slots 14-14b, etc~
in the main rotor laminae such as the lamina 13 shown in Figure 2. These conductor slots 14'-14b' are also arcuately spaced adjacent the periphery of the lamina 17 with spacings matching those of the conductor slots in the main rotor laminae 13. Each of the vent laminae, such as the lamina 17, is also provided with a plurality of vent apertures 18, arcuately spaced between the inner ends of the conductor slots 14'-14b', etc.
and the inner diameter 17a of the lamina. Pursuant to the present invention each of the vent apertures 18 is formed with a radial dimension, such as that designated by the arrow 18' in Figure 3, substantially greater than the maximum radial dimension, such as that designated by the arrow 15' in Figure 2, of the coolant passageway 15 in lamina 13. Accordingly, when one of the main rotor lamina 13 is positioned adjacent one of the vent lamina 17 it will be appreciated that a substantial portion of each vent aperture 18, etc. overlaps the aligned coolant passageway apertures 15 of the main rotor lamina. The purpose of this overlapping arrange-ment will be discussed below relative to the low pressure drop movement of cooling air through the laminae assembly of the invention when the rotor is operated.

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i 21 GM-284 ~, i It will be noted that ~he vent la3mina 17 also is ~-¦¦ provided with an aligning s~ot 19. Th~s ~lot i8 used , ~n the same manner a~ the 810t 16 in main rotor lamina 13, Il to align the vent laminae 17 (and its counterparts? when 3 S 1¦ they are stacked for a casting operation. Again, it j ~- J
I should be noted that each of the other vent laminae used ~:
i in rotor assembly 1 of the invention ~ 8 substantially identical to the vent lamina 17 shown in Figure.3.
¦ Finally, the laminae assembly 1 include~ a plur~lity i!", of substantially flat, annular duct laminae such as the lamina 20 ~hown in fragmentary vi~w in Figure 4. Each duct I lamina, such as the lamina 20, is punched to fonm apertures ¦ therein that define respectively a plurality of conductor ,~
¦ 810ts 14", 14a", 14b", etc. which are substantially I identical in 5hape to the conductor slots formed re~pectively in the main rotor lamlna 13 and the vent lamina 17 described above with referen-e to Figures 2 and 3. Slot 14", 14a", 14b" nay be di~erent in size I ``
and/or shape from slots 14, 14a and 14b, and 14', 14a' and 14b' for the purpose o increasing the width of coolant duct slots 22, 22a and 22b, or the wldth of the lamination that separates ~he conducbor 810t3 (14N) from the duct ,~
slots (~2, etc.),or for the purpose o~ standardization , ~ and com~ionalit~ between dif~erent electrical dssigns, i.e., ~ 810t shape~ and number of slots. As ~n th08e ca~es, i ~l Ij -13~

~1~92Z5 21-GM-284 the conductor slots 14"-14b", etc. are arcuately spaced adjacent the periphery of the lamina 20.
In addition to the conductor slots, a plurality of coolant passageways 21 are arcuately spaced between the inner ends of the conductor slots 14"-14b", etc.
and the inner diameter 20a of the lamina 20. It will be appreciated that the conductor slots and coolant passageways in the lamina 20 are arranged for substantial alignment with the like apertures in the main rotor laminae such as lamina 13 shown in Figure 2. While the coolant slots 22, 22a, 22b, etc. are shown as rectangles in Figure 4, the slots can be made to have other shapes.
One improved configuration of coolant duct is shown, for example, in Figure 5 wherein coolant slots 22A, 22B, 22C are provided with flared openings at their respective outer ends. The advantages of this laminae configuration are reduction in air duct noise and improved machining of the rotor surface when the periphery is removed to open the coolant ducts.
It will be noted that conductor slots 14A, 14B
and 14C, etc. in the lamination of Figure 5 differ in form from the conductor slots 14", 14a" and 14b" shown in Figure 4, in order to further illustrate the flexibility of the invention. Likewise the coolant passage 21A shown in the alternative form of punching 20A in Figure 5, differs in outline from the functionally related passageways 21 in punching 20 shown in Figure 4.

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Returning now to a description of the invention in the embodiment thereof using the configuration of laminae shown in Figures 2, 3 and 4, it will be seen that each of the duct laminae, like lamina 20, is also provided with a plurality of punched, or otherwise machined coolant duct slots 22, 22a, 22b, etc. that each extend, respectively, from the periphery of the lamina to a point, such as the poin~s 22', 22a', 22b', shown in Figure 4, located between the inner ends of the conductor slots and the outer extent of the adjacent coolant passageways 21. For example, as seen in Figure 4, the innermost points of the duct slots 22-22b terminate at the points 22'-22b' adjacent the outer extent 21a' of the edge of axial coolant passageways21.
It will also be seen by reference to Figure 4 that these points 22'-22b', etc. are radially positioned between the outer extent 21a' (for example" of the respective coolant passageways 21 and the outer extent (18a' seen in Figure 3) of the adjacent vent apertures such as vent apertures 18 shown in the vent duct 17 illustrated in Figure 3, when such a vent lamina is disposed adjacent a duct lamina 20 in the laminae assembly of the invention. Thus, the inner end of virtually every duct slot 22-22b, etc. is placed in overlapping relationship with an adjacent vent apertures 18 and each vent apertures 18 . .,, ,~

lll9;~Z5 ~ 21-GM-284 B 1 i~ po~itioned in overlapping relat.ivnship with a coolant 1 passaqeway 15-~g~ in adjacent main rotor laminae, such as I the lamina 15 ~hown in Figur~ 2.
i Finally, the coolant duct lamina 20 shown in S 1~ Figure 4 and each of the substantially identical j a~qociated coolant duct laminae in asse~bly 1 are each ` provided with an alignment notch 23 formed in ~he inner diameter thereof for aligning these laminae for a ', ¦ castLng operation in the manner descrik.ed above with j reference to the other laminae of the assembly 1.
, It ~hould also be under~tood that various conventional i materials may be used to ~orm the respective laminae used in making the laminated rotor assem~ly of the invention.
I In this eimbodiment o$ the invention a ~uitable conventional I magnetic steel i8 u3ed to form each of the laminae, as is I well-known in the p~ior art. It should be understood, j thou~h, that while conventional magnetlc stteels are used ror each l.~mination, the different types o~ laminae may ,.
¦ (and in the pre~errbd embodiment do) u~e different types I of steei. For ~xample, laminations 13 and 17 in this ¦ eimbodiment are made of silicon steel with inc.rganic ¦ coa~ings, for performance~ while lamina 20 was made of non-coated steel to opt~mize processting.
ll To complete i~he rotor laminae a'89~mbly 1 of the ji invention in the ~orm illustrated in Figure 1, the preselected plurality of mBln rotor la~inae 13, vent la~,inae, 17, and duct laminae 20 are arranged in ad~acent li ` t ,. . . . . .

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l9Z~5 groups and aligned with each other to place their reepective conductor ~lot~ in ~ub~tantial alignment.
j Such groupings of the main rptor laminae are designated ¦ clearly in the enlarged view of Figure lA by the numeral 13', a group of vent laminae adjacent thereto i~ designated in Figure lA by the numeral 17', and a group of duct laminae are de~ignated in Figure lA by the numeral 20'. Of courqe, such groupings are repeated along the assembly 1, a~ shown in Fi~ure 1. With these respective ~ets of laminae th w arranged and the associated alignment slots 16, 19 and 23 therein positioned to align the respective conductor slots as desired, the laminae assembly i8 compre~ed together to form liquid tight ~eals between adjacent laminae 80 that molten metal cannot escape-from the conductor slots inbo the adjacent cooling ducts or ven~ passageways ~he cast conductors and integrally cast annuli 5 and 6 that join the conductors !
together at the opposite end~ thereof are effective, when cooled and hardened, to hold the rotor laminae assembly 1 together. Pursuant to the present invention each o the duct laminaa, such as lamina 20, ~8 formed 80 that one of the coolant ducts, such as duct 22f, i8 positioned between each adjacent pair of conduct~r slots, such as the pair of conductor slots l~ 14an shown in Figure 4. ' Thi~ intimate relatlon~hip between the c~olant duota and the conductor ~lot~ i8 further m~ximized ¦ pursuant bo the invention by maintaining the ~pacing .
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be~ween the sides of each duct slot and the conductor , slots clo3est thereto in the range of .030 to .100 inches.
i Thu~ the entire depth o e~ch conductor 810t iS
j positioned in optimNm heat ~xchange relationship with S the adjacent coolant ducts. Furtherm~re, pursuant to the invention, each of the coolant duct slots 22-22b, QtC. (or 22A-22C, etc. in Figure 5) i9 formed to be ¦ approximately 100 percent deeper in a radial direction ¦ than the conductor slotet adjacent to them. This relation-¦ ship i~ effective to assure a high volume flow of coolina ¦ air through the ~enting aperturect in adjacent ventîng lamina, such as lamina 17, inbo the cooling ducts.
Also, pre~s~re loss in the cooling air is minimized in the preferred embodiment of the invention being described by making the area of each vent aperture 18-18b, etc.
about twice as large a~t the coolant passageway apertures 21-21b, etc. with which they cooperate.
Each of the coolant duct stlots 22-22b, etc. are 3 also ~ormed to extend radially outward beyond the conductor slots ad~acent thereto by at least .02 inches.
Thi8 relative arrangement of the duct slots with the conductor slots makes it pos~lble to easily machine the ¦ peripherAl surface 20b o~ the duct laminae 20 to open I the outer end~ of the ducts 22-22b, ètc. afber conductors are cast in the conductor slotst, there~y tD ~nable air bD
flow through the laminae as~embly in the manner expla~ned above. It will be understood that during such a conductor t ii . -18- .
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21-GM~284 ¦ casting operation the ends of the a~ial passagewayR 15- j ¦ 15b, etc. in the outermost main rotor laminae 13 will be ¦ su~tably shielded in a convent~onal manner to prevent I molten ca~ting metal from e~tering the passageways S I through the outer laminae. t Those skllled in the art will recognize that various combination~ of the three sets of laminae described above may be as~embled to make differçnt forns of cooling passageways and cooling ducts through a rotor laminae assembly pursuant to the invention. However, as shown in Figure 1 of the drawing in the preferred embodiment of the invention~substantially equal numbers of vent laminae 17 and duct laminae 20 are arranged in cooperating sets with a group of duct laminae disposed ad~acent a group of vent laminae at preselected axialIy spaced intervals between larger groups of main rotor laminae 13 a3 dQ~ignated i~ Figure lA by the respective ¦¦ numerals 13', 17' and 20'. IhiB arrangement enables a large volum~ of cooling air to be forced through the ~0 rotor with a de~irably small loss of pressure. Thus, as shown by the arrows in Figure 1, cooling air is forced by rotation o~ the shaft 7, and result~nt centrifugal force in duct~ 22, 22a and 22b, etc. mDunted thereon, to move axlally through the p~s~ageway 12 defined by the apertures 15-15b~ etc.~ 18-18b etc., and ducts 21-21b et¢., respectively, in the main rotor laminae 13', th~ vent lam~nae 17' and the duct laminae 20'. As can be seen, the air flows from the axi~l passageway 12 and lts I! `
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1 :1119ZZ5 ., arcuately spaced counterpart~ into the vent passagew~ays ¦t formed by the vent apertures l8-l8b, etc. in the venting i laminae 17 and thence into ~ e c~oolant ducts, the inner I¦ ends of whlch overlap the vent apertureR
,~ It will be recognized that substantially all of thQ cooling ducts 22-22b, etc. have their inner ends overlapping an a~ociated ventinS aperture 18-18b etc.
in an ad~,acent venting lamina 17, due to the depth and I close spacing of the ducts in the duct laminae 20.
¦ However, it can also be seen that one or two o~ the ¦ cooling ducts in each duct lamina will not be in overlapping relationship with a venting aperture in the embodiment oi' the invention described herein.
¦ In the event that the cooling requirements for a given rotor laminae assembly are such that each oooling duct 22-22b etc. must receive cooling air from one of the Yenting apertures 18-18b to avoid the formation of eYen one or two hot spot~ on the rc,tor, the aligning ~lot 19 in the v~nt~ng laminae 17 may be arranged such that alternate vent lamina can be reversed or turned over as they are sta~kad in a~6embled pc,sition.
m~8 ~rrangement will cause ea~h of the cooling ducts to b~ pc,~itioned in overlapping relationship with one I of the ~enting apertures ~o that eac~ cooling duct ! recei~es coolant from the axial passageways in the main ¦ rotor laminae. Howe~er, it has been fDund that for m~st ¦ commercial applications the preferred embodiment o~ the ! `
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.~ !! 1119Z25 ', i ~ 21-GM-284 ~ invention provides adequate cooling ~or the rotox and ¦! its a~sociated stator.
.¦¦ Other modification9 and~ alternative forms of the ¦ invention will be apparent to those skilled in the art ¦ from the descript~on of it presented herein; acoordingly, j it is our intention to encompas~ within the ficope of the following ciaim~ the true spirit and limits of the invention.

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Claims (8)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
1. A rotor laminae assembly for a dynamoelectric machine having cast axial conductors and radial ventilating ducts extending between said conductors at axially spaced intervals, characterized by the improvement comprising:
a.) a plurality of substantially flat, annular main rotor laminae each formed with apertures therein to define, respectively, a plurality of conductor slots arcuately spaced adjacent to the periphery of the laminae and a plurality of coolant passageways arcuately spaced between the inner ends of said conductor slots and the inner diameter of the laminae, b.) a plurality of substantially flat, annular vent laminae each provided with apertures that define, respectively, a plurality of conductor slots arcuately spaced adjacent to the periphery of the laminae and a plurality of vent apertures arcuately spaced between the inner ends of said conductor slots and the inner diameter of the laminae, each of said vent apertures being formed with a radial dimension substantially greater than the maximum radial dimension of the coolant passageway formed in said main laminae, c.) a plurality of substantially flat, annular duct laminae each provided with apertures that define, respectively, a plurality of conductor slots arcuately spaced adjacent to the periphery of the laminae, a plurality of coolant passageways arcuately spaced between the inner ends of the conductor slots and the inner diameter of the
1. Claim 1 Cont'd (c) laminae, and a plurality of coolant duct slots extending from the periphery of the laminae to a point between the inner ends of the conductor slots and the outer extent of the coolant passa-geways, said point being radially positioned between said outer extent of the coolant pass-ageways and the outer extent of the vent apertures in adjacent vent laminae thereby to place the inner end of each duct slot in overlapping relation-ship with an adjacent vent aperture and to position each vent aperture in overlapping relationship with a coolant passageway in adjacent main rotor laminae, d.) said plurality of main rotor laminae, vent laminae and duct laminae being aligned with each other to place the conductor slots in alignment, and a plurality of electrical con-ductors cast, respectively, in each of said conductor slots and joined together at the opposite ends thereof, respectively, by a pair of cast annuli disposed with said conductors, said cast con-ductors being effective to hold the rotor laminae assembly together.
2. 2. An invention as defined in claim 1 wherein each duct lamina is formed with one of said coolant duct slots between each adjacent pair of conductor slots, the spacing between the sides of each duct slots and the closest con-ductor slot being in the range of.030 to .100 inches.
3. 3. An invention as defined in claim 2 wherein each coolant duct slot is formed to be approximately 100 percent deeper, in a radial direction, than the conductor slots adjacent thereto.
4. 4. An invention as defined in claim 3 wherein said vent laminae and duct laminae are arranged in cooperating sets of about equal axial length, each set comprising a group of duct laminae disposed adjacent a group of vent laminae at axially spaced intervals between larger groups of main rotor laminae.
5. 5. An invention as defined in claim 1 wherein all of said laminae are positioned sufficiently close together to prevent molten metal from flowing between them from the conductor slots.
6. 6. An invention as defined in claim 3 wherein said coolant duct slots extend radially outward beyond the conductor slots by at least .02 inches.
7. 7. An invention as defined in claim 5 in combination with a steel shaft force-fitted within the inner diameter of all of the annular laminae to support them for rotation on said shaft.
   
   8. A rotor laminae assembly for a dynamoelectric machine having cast axial conductors and radial ventilation ducts extending between said conductors at axially spaced intervals, wherein the improvement comprises:
   a) a plurality of main rotor laminae having arcuately spaced conductor slots and coolant passageways, b) a plurality of vent laminae having arcuately spaced conductor slots and vent apertures, c) a plurality of duct laminae having arcuately spaced conductor slots, vent passageways and coolant duct slots, each of said coolant duct slots being flared outward at both the leading and trialing edges of the outer end thereof,
8. Claim 8 continued:
   d) the conductor slots in all of said laminae being in substantial alignment, and a plurality of cast conductors positioned, respectively in each of said conductor slots to hold the assembly together.