United States Patent (19)
`Dymond et al.
`
`73) Assignee:
`
`(54) SALIENT POLE ROTOR FOR A
`DYNAMOELECTRIC MACHINE
`75) Inventors: James H. Dymond, Peterborough;
`Nick N. Saidi, Ajax; John M. Young,
`Omemee, all of Canada
`General Electric Canada Inc.,
`Mississauga, Canada
`(21) Appl. No.: 650,540
`22 Filed:
`Feb. 5, 1991
`(30)
`Foreign Application Priority Data
`Feb. 22, 1990 CA) Canada ................................. 200670
`51
`Int. Cl................................................ HO2K 1/24
`52 U.S. C. ...................................... 310/269; 310/58;
`310/60 R; 310/91; 310/194
`58 Field of Search ................... 310/269, 261,58, 59,
`310/61, 62, 63, 64, 65, 60 R, 60 A, 91, 42, 254,
`218, 52, 208, 194
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`894,015 7/1908 Kishi ................................... 310/269
`896,323 8/1908 Reist .................................... 310/269
`928,037 7/1909 Frost ................................... 310/269
`1,030,041 6/1912 Williamson ......................... 310/269
`2,899,573 8/1959 Wesolowski ...
`310/269 U X
`3,590,301 6/1971 Woydt ................................. 30/269
`3,739,212 6/1973 Koelbel et al. ..................... 310/194
`3,846,651 1 1/1974 Mishra .................................. 310/61
`4,383,191 5/1983 Mazuyama.
`... 310/59
`4,467,229 8/1984 Ogita ......
`... 310/64
`5,036,238 7/1991 Tajima ................................ 310/269
`
`
`
`HHHHH
`US005086246A
`Patent Number:
`5,086,246
`11
`45) Date of Patent:
`Feb. 4, 1992
`
`FOREIGN PATENT DOCUMENTS
`909844. 9/1972 Canada .
`118 118 /985 Canada .
`19453. 10/1985 Canada .
`0.063530 5/1980 Japan ................................... 310/269
`0.063540 5/1980 Japan ................................... 310/269
`2066585 2/1981 United Kingdom ................ 310/269
`Primary Examiner-R. Skudy
`(57)
`ABSTRACT
`A dynamoelectric machine has a stator with a stator
`core and a plurality of spaced apart radially extending
`ventilation ducts. A rotor mounted for rotation within
`the stator has a shaft with a plurality of salient poles.
`Each salient pole has a winding on it and each pole with
`its winding constitutes a pole member. Adjacent pole
`members define between them an interpolar space.
`Cooling air enters each interpolar space from each end
`when the machine is operating, moves generally axially
`as portions of the air change direction to move radially
`outwards through the air gap separating the rotor and
`stator and then through the ventilation ducts. The air
`flow, in a radial outward direction, tends to be less at
`the ends of the rotor and through the ventilation ducts
`adjacent the ends of the stator. The invention places a
`baffle at each end of each interpolar space. The baffle is
`in a generally radial plane and has an outward edge
`adjacent the outer limit of the interpolar space as de
`fined by the tips of the poles, and an inward edge spaced
`from the bottom of the interpolar space. The baffle
`improves the air flow radially outwards adjacent the
`ends of the rotor and the stator.
`
`6 Claims, 3 Drawing Sheets
`
`Page 1 of 7
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`U.S. Patent
`U.S. Patent
`
`Feb. 4, 1992
`Feb. 4, 1992
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`Sheet 1 of 3
`Sheet 1 of 3
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`5,086,246
`5,086,246
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`2a
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`s SS
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`a Dm
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`ML
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`1
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`FG.
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`ed
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`s: e.
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`2.
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`e
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`Page 2 of 7
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`Page 2 of 7
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`U.S. Patent
`U.S. Patent
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`Feb. 4, 1992
`Feb. 4, 1992
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`Sheet 2 of 3
`Sheet 2 of 3
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`5,086,246
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`5,086,246
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`IN
`III)
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`io
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`FIG. 4B,
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`28C
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`J
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`,
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`FIG.4A,
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`Page 3 of 7
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`Page 3 of 7
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`U.S. Patent
`
`Feb. 4, 1992
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`Sheet 3 of 3
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`5,086,246
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`3.
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`50
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`DRIVE END
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`CORE POST ON
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`FG,5A.
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`51
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`CORE POSITON
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`FG,5B.
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`52
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`CORE POST ON
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`FIG.5C.
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`Vo
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`F. G.7A.
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`FG,6A.
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`FG.6B,
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`V
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`V
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`Vo
`Wol
`FG.7B. F.G.7C.
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`Page 4 of 7
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`

`1.
`
`SALENT POLE ROTOR FOR A
`DYNAMOELECTRIC MACHINE
`
`5
`
`O
`
`BACKGROUND OF THE INVENTION
`This invention relates to a salient pole rotor for a
`dynamoelectric machine, and in particular it relates to a
`rotor having a baffle arrangement to improve the air
`flow distribution.
`In a dynamoelectric machine having a rotor with
`salient poles, it is desirable to have not only the temper
`atures axially along the rotor as uniform or even as
`possible, but also to have the temperatures axially along
`the stator as even as possible. In a machine with no
`rotor fan, the circulation of the cooling gas (which will
`be referred to hereinafter as air) is pumped or driven by
`the rotating rotor across the air gap and through venti
`lation gaps or ducts in the stator core. The temperatures
`of the stator core, measured axially along the core, tend
`to be higher at the ends of the core. This is usually
`20
`because the static pressure of the circulating air at the
`ducts adjacent the ends of the stator core tends to be
`lower. It is, of course, the higher temperatures that must
`limit the operation of the machine, and it is desirable
`that the higher temperatures be reduced.
`SUMMARY OF THE INVENTION
`The present invention provides a baffle arrangement
`which tends to increase the static pressure adjacent to
`the ends of a salient pole dynamoelectric machine, and
`30
`consequently increase the flow of cooling air in the
`portions of the machine adjacent the ends.
`It is therefore an object of the invention to provide
`for a dynamoelectric machine, a salient pole rotor hav
`ing a baffle arrangement for increasing the static pres
`35
`sure of the cooling air as it leaves the end portions of the
`rotor and enters cooling ducts adjacent to the ends of
`the stator.
`It is another object of the invention to provide a
`baffle for a salient pole rotor where the baffle extends in
`a substantially radial plane between adjacent pole mem
`bers at the ends thereof and having a radially outward
`edge adjacent the periphery of the rotor and an inward
`edge spaced from the bases of the adjacent pole mem
`bers.
`45
`In accordance with one form of the invention there is
`provided a dynamoelectric machine having a salient
`pole rotor with an axially extending shaft mounted for
`rotation within a stator, the rotor having no ventilation
`fan associated therewith, the rotor and the stator defin
`50
`ing therebetween an air gap, the stator having a stator
`core with stator windings thereon, the stator having a
`plurality of spaced apart, ventilation ducts extending
`radially from the air gap to an exhaust region, the dyna
`moelectric machine being cooled by a cooling gas cir
`55
`culated through the rotor and stator, the rotor compris
`ing a plurality of axially extending, spaced apart poles,
`mounted on the shaft, each pole having a base where it
`mounts to the shaft and a pole tip radially outwards of
`the base and defining a periphery of rotation, a winding
`60
`on each pole, each pole and respective winding thereon
`forming a pole member, adjacent pole members defin
`ing therebetween an interpolar space, at least one coil
`bracket in each interpolar space, each coil bracket hav
`ing a central portion with extending arm portions,
`65
`means for fastening each coil bracket to the shaft at the
`central portion thereof, the respective arm portions
`'engaging the surface of the adjacent windings of adja
`
`15
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`25
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`5,086,246
`2
`cent pole members for aiding in securing the windings, .
`a baffle at each end of each interpolar space, each of the
`baffles being in a substantially radial plane and extend
`ing between adjacent pole members with a radially
`outward edge adjacent the periphery of rotation and an
`inward edge spaced outwardly from the bases of the
`adjacent pole members, with rotation of the rotor the
`baffles tending to increase at each end of the rotor the
`static pressure of the cooling gas within the machine in
`the air gap adjacent the ends of the rotor thereby im
`proving the flow of the cooling gas radially outwards
`through the air gap and the stator ventilation ducts
`adjacent the ends of the stator.
`BRIEF DESCRIPTION OF THE DRAWINGS
`The invention will be described with reference to the
`accompanying drawings, in which
`FIG. 1 is a partial isometric view of a salient pole
`rotor according to one form of the invention,
`FIG. 2 is a partial sectional side view of a dynamo
`electric machine having a rotor similar to that of FIG.
`1,
`FIGS. 3A and 3B are end views of a salient pole rotor
`each showing a different form of baffle on the rotor,
`FIGS. 4A and 4B are cross sectional views of two
`forms of baffle according to the invention,
`FIGS. 5A, 5B and 5C are graphs useful in explaining
`the invention,
`FIGS. 6A and 6B are air velocity diagrams useful in
`the description, and
`FIGS. 7A, 7B and 7C are vector diagrams useful in
`the description.
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`Referring first to FIG. 1, there is shown an isometric
`view of one end of a salient pole rotor 12 having a shaft
`10 and a rim 11. Four salient poles 14 are mounted to
`rim 11. Each pole 14 has a base 15 and a pole tip 16.
`Also, each pole has a winding 17, as shown. The turn
`portions or end portions of the winding 17 have been
`omitted for ease of drawing. Each pole 14 with its re
`spective winding 17 forms a pole member 18. The re
`gion or space between adjacent pole members 18 may
`be referred to as an interpolar space 24, and in each
`interpolar space 24 there is at least one coil bracket 19.
`Each coil bracket 19 has a central portion 20 and ex
`tending arms 21 and 22 which extend in opposite direc
`tions. A bolt 23 through the central portion 20 secures
`the coil bracket 19 to the rim 11. The arms 21 and 22
`engage the surface of the respective windings 17 of the
`adjacent ones of pole members 18 to assist in holding the
`windings or coils in place against forces caused by rota
`tion. As will be discussed hereinafter, there may be a
`plurality of spaced apart coil brackets 19 in each inter
`polar space 24 and the central portion 20 may have
`different thicknesses, that is, the outer surface of the
`central portions may be at different radial distances
`from the axis of rotation.
`At each end of rotor 12 in each interpolar space 24
`there is a baffle 25 which lies in a substantially radial
`plane. Baffle 25 is also shown, for example, in FIG. 3A.
`Referring for the moment to FIG. 3A, there is shown
`an end view of a rotor 12, again with the ends of wind
`ings 17 omitted. The rotor 12, when rotating, defines
`with the pole tips 16 a periphery of rotation 26, indi
`cated by a broken line. Each baffle 25 extends between
`
`Page 5 of 7
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`O
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`5,086,246
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`4.
`adjacent ones of pole members 18 and has an outer edge
`located in each interpolar space, and no baffle 25
`27 which is adjacent the periphery of rotation 26 and an
`(FIGS. 1, 2, 3A and 3B, for example). The air flow
`inner edge 28 spaced outwardly of the bases 15 of the
`tends to be greater in the central region where the air
`adjacent ones of pole members 18. Thus, the baffles 25
`flow from each end meets. This is increased to some
`extend across the radially outward portion of the end of 5
`extent by the coil bracket which tends to act as a fan
`each interpolar space 24 but do not extend across the
`blade.
`inner portion. The outward edge 27 of each baffle may
`FIG. 5B has a line 51 representing air flow through
`be straight as shown in FIG. 3A or curved as shown in
`ventilation ducts at different axial positions where the
`rotor has five coil brackets in each interpolar space,
`FIG. 3B.
`Referring for the moment to FIG. 3B, there is shown
`spaced along the rotor. Because each coil bracket acts
`somewhat as a fan blade, the air flow is slightly greater
`an end view of a rotor 12, similar to that of FIG. 3A, but
`with a baffle 25A that has a different configuration. The
`in the region of each coil bracket. In fact, suitable plac
`baffle 25A has a straight inner edge 28, but has an outer
`ing of the coil brackets where the air flow is a little less
`edge 27A which is curved and generally follows the
`tends to distribute the flow as desired. In addition, the
`periphery of rotation 26. Thus, the outer edge of each
`change in air flow contributed by a coil bracket can be
`baffle (in a radial direction) may be straight, curved or
`altered to some extent by changing the thickness of the
`a combination of straight and curved. In each instance
`central portion 20 (FIG. 1) of the coil bracket. The
`the outer edge of the baffles is adjacent the periphery of
`effect of the coil brackets can be determined by experi
`rotation.
`ment.
`Referring to FIGS. 4A and 4B, there is shown in 20
`In FIG. 5C the line 52 represents air flow in the venti
`FIG. 4A a cross-sectional view of baffle 25, and there is
`lation ducts of a machine similar to the machine where
`the air flow is represented by FIG. 5B, but with a rotor
`shown in FIG. 4B a cross-sectional view of an alternate
`form of a baffle 25C. Baffle 25C has at least an inner
`12 which has baffles 25 on the rotor as described in
`edge 28C that is curved on the outer surface in an axial
`connection with FIGS. 1, 2, 3A and 3B, for example.
`direction inward to improve the air or gas flow into the
`The air flow in the ventilation ducts 37 (FIG. 2) which
`interpolar spaces. The baffles 25C may be said to form
`are adjacent the ends of the stator has been increased.
`a bell-mouth at the end of the rotor. The baffle 25C, as
`The addition of the baffles of the invention does not
`shown, has both inner and outer edges curved.
`make the air flow in the end ventilation ducts equal to
`Referring now to FIG. 2, there is shown a sectional
`the air flow through the ducts in the central part of the
`side view of a dynamoelectric machine having a rotor
`stator, but it does increase it.
`12 as described, for example, in connection with FIGS.
`In one example, a dynamoelectric machine model
`1, 3A, 3B, 4A and 4.B. The winding 17 is shown on pole
`with a salient pole rotor according to FIGS. 1 and 2 was
`14 between pole collars 30 and 31. One coil bracket 19
`rotated at 450 rpm and the static pressure was measured,
`is shown midway between the ends of pole member 18.
`in inches of water, at the two end ventilation ducts and
`A baffle 25 is shown at each end of pole member 18.
`at several intermediate ventilation ducts (at two radial
`35
`Stator 33 has a stator core 34 with a winding 35 hav
`positions in each measured duct). Without baffles in
`ing end turns 36. The stator core 34 has a plurality of
`stalled, the static pressure at the end opposite the drive
`radially extending, axially spaced, ventilation ducts 37.
`end was 0.10 inches of water and at the drive end was
`A stator frame 40 includes stator core support plates 38,
`0.12 inches of water. With baffles according to the in
`stator core flanges 41, stator core bars 42, and space 40
`vention installed at both ends of each interpolar space,
`blocks 43. Bearing bracket assemblies 44, represented
`the static pressure measured at the end opposite the
`schematically, include bearings for supporting shaft 10
`drive end was 0.45 inches of water, and at the drive end
`to provide for rotational movement of the rotor. Stator
`was 0.54 inches of water. The static pressure at the
`structures of this form are known.
`intermediate points had also increased. As the static
`When the machine is operating, the flow of cooling 45
`pressure is a determining factor in air flow, other things
`air (or other cooling gas) is indicated by arrows 45. The
`being the same, the baffles would result in an increase in
`air flow is indicated by arrows 45 for only one half of
`air flow through the end ducts. Thus, the increased air
`flow not only improves the cooling of the rotor, but
`the machine; the air flow is the same for the other half.
`The air is introduced from a passageway 39, indicated
`improves the cooling of the end regions of the stator.
`by broken lines, normally from atmosphere, although
`It is believed that the following description explains
`the passageway 39 could be connected to receive recir
`how the baffles improve the air flow and the cooling of
`culated air as is known.
`the rotor and of the end regions of the stator. In a salient
`There are frequently axially extending air passages in
`pole rotor, the pole members themselves tend to move
`rim 11 as is indicated by broken line 46 representing air
`air radially outwards. The coil brackets tend to increase
`flow through such a passage and through openings in
`the outward flow in the region where they are mounted.
`rim 11 into the interpolar spaces to improve the cooling
`Thus, the air flows into the interpolar spaces from each
`of the inner parts of windings 17. The air flow passes
`end and changes direction to flow radially outwards
`from the interpolar spaces radially outwards through
`through the air gap and the stator ventilation ducts. The
`air gap 47 between the periphery of pole members 18
`axial air velocity tends to be greater at the bottom of
`each interpolar space, and a typical air velocity profile
`and the stator core 34, and then through ventilation
`ducts 37 into exhaust region 48 which is open to atmo
`for the rotor interpolar area is shown in FIG. 6A. In
`sphere.
`reality, there tends to be some back flow or reverse
`Referring now to FIGS. 5A, 5B and 5C, there are
`flow, as shown by the air velocity profile of FIG. 6B.
`shown graphs of air flow against axial positions along a
`The air entering the interpolar area is acted upon by
`stator core giving relative air flow through the ventila
`several forces, mainly centrifugal force and coriolis
`force. The interaction of the centrifugal force, F, repre
`tion ducts 37 (FIG. 2). In FIG. 5A, a line 50 indicates air
`flow through the ventilation ducts in a machine with a
`sented by the equation Faro and the coriolis force,
`salient pole rotor having one coil bracket, centrally
`Fc represented by the equation FaVaco determine the
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`5,086,246
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`arm portions of said coil bracket engaging adjacent
`flow direction. In the above equations, r is the radius
`from the axis, a) is the angular velocity, and V is the
`surfaces of the windings of adjacent pole members
`for aiding in securing said windings,
`axial velocity of the air.
`At the shaft the axial velocity, Va., is very high and it
`abaffle at each end of each said interpolar space, each
`decreases in magnitude when moved radially outwards,
`of said baffles being in a substantially radial plane
`reducing to zero and then reversing as shown in FIG.
`and extending between adjacent ones of said pole
`6B. The tangential velocity of the air, V, is low near the
`members, each said baffle having a radially out
`shaft and increases when moved radially outwards.
`ward edge adjacent said periphery of rotation and
`Therefore, the typical velocity vectors at the shaft are
`an inward edge spaced outwardly from said bases
`as shown in FIG. 7A and at the air gap are as shown in
`of adjacent ones of said pole members,
`FIG. 7B. V represents the relative resultant velocity.
`with rotation of said rotor said baffles tending to
`By placing a baffle at the end of the interpolar space
`increase at each end of said rotor static pressure of
`adjacent to the air gap, Va is reduced and the flow
`said cooling gas within said machine in said air gap
`becomes substantially radial as shown in FIG. 7C.
`adjacent the ends of said stator, thereby improving
`Hence the air is directed almost radially outwards into
`flow of said cooling gas radially outwards through
`the first few ventilation ducts in the stator. The baffles
`said air gap and said ventilation ducts adjacent the
`also tend to increase the radial and tangential velocity
`ends of said stator.
`components because the baffles are a rotating surface.
`2. A dynamoelectric machine as defined in claim 1 in
`This combination or interaction tends to increase the air
`which said outward edge of each said baffle is straight.
`flow in the end regions of the rotor and of the stator.
`20
`3. A dynamoelectric machine as defined in claim 1 in
`It is believed the preceding description adequately
`which said radially outward edge of each said baffle is
`explains the invention.
`curved generally to follow said periphery of rotation.
`What we claim as new and desire to secure by Letters
`4. A dynamoelectric machine as defined in any of
`Patent of the United States is:
`claims 1, 2 or 3 in which said inward edge of each said
`1. A dynamoelectric machine having a salient pole
`25
`baffle is straight.
`rotor with an axially extending shaft mounted for rota
`5. A salient pole rotor for a dynamoelectric machine
`tion within a stator, the rotor having no fan associated
`having no ventilation fan associated therewith, compris
`therewith, the rotor and stator defining therebetween
`1ng
`an air gap, the stator having a stator core with stator
`a shaft having a longitudinal axis,
`windings thereon, and a plurality of spaced apart venti
`30
`a plurality of poles mounted on said shaft and extend
`lation ducts located between axially opposing ends of
`ing axially, each said pole having a pole tip at a
`the stator and extending radially from the air gap to an
`distance from said longitudinal axis, said pole tips
`exhaust region, said dynamoelectric machine being
`defining a periphery of rotation,
`cooled by a cooling gas circulated through said rotor
`a winding on each said pole, each said pole and said
`and said stator, said rotor comprising
`winding thereon forming a pole member, adjacent
`a plurality of axially extending, spaced apart poles,
`ones of said pole members defining therebetween
`mounted on said shaft, each pole having a base
`an interpolar space, and
`where it mounts to said shaft and a pole tip radially
`a generally wedge-shaped baffle for improving air
`outward of said base and defining a periphery of
`flow in the machine at each end of each said inter
`rotation,
`40
`polar space, each said baffle extending between
`a winding on each said pole, each said pole and re
`adjacent pole members across the interpolar space
`spective winding thereon forming a pole member,
`and having a radially outward edge adjacent said
`adjacent pole members defining therebetween an
`interpolar space,
`periphery of rotation and an inward edge spaced
`radially outward from a bottom of the shaft.
`at least one coil bracket in each interpolar space, each
`45
`said coil bracket having a central portion with
`6. A salient pole rotor as defined in claim 5 in which
`extending arm portions,
`said inward edge of each said baffle has an axially ex
`tending curve forming a bell mouth configuration.
`means for fastening each said coil bracket to said shaft
`at the central portion of said bracket, respective
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