Note: Descriptions are shown in the official language in which they were submitted.
1137148
ROTOR CONSTRUCTION FOR
DYNA~IOELECTRIC MACHINES APPARATUS
Background 0f the Invention
The present invention relates to a dynamoelectric machine
and particularly to the construction of a rotor having an integral
cooling means.
Dynamoelectric machines are highly developed devices and
which generally include a fixed stator supporting a suitable field
winding and a rotor carrying an armature winding. A generator for
producing an alternating and particularly three phase alternating
current output may be of a rotating field construction in which a
main salient pole field and small brushless exciter for providing
DC current to the main field are mounted as the rotor within a
stator having a polyphase output winding. In the salient pole system,
the rotor includes a plurality of poles each of which carries a field
winding which is series or parallel connected with the other field
windings. A particularly satisfactory rotor structure is manufactured
and sold by Marathon Electric of Wausau, Wisconsin, in which the rotor
amortisseur winding and coil support is die cast as an integral part
of the rotating field rotor. Thus, the four poles are formed from
one piece laminations with appropriate amortisseur winding and -
clamping openings, and the end rings and amortisseur winding is
integrally formed of a die cast aluminum resulting in high mechanical
integrity and low vibration at operating speeds. The rotor pole
assembly is then heat shrunk and keyed to the support shaft. The
field windings are wound on the poles with suitable pole insulation.
In such generators and like dynamoelectric machines cooling
is required to prevent overheating of the windings which must be
maintained during operatiOn within a maximum safe operating temperature.
Generally, fan means are coupled to the shaft to establish an air
flow through the generatOr and thus over the stator and rotor
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surfaces, particularly the main field winding structure. It is
important that efficient cooling be created, with the air distributed
more or less evenly over the field surface and with minimal recircu-
lation of hot air. Although va-~ious cooling systems have been suggested,
they have generally provided a flow-through pattern relying on a high
volume movement OVer the component parts to establish the effective
- cooling of the winding.
Summary Of The Invention
The present invention is particularly directed to an improved
ventilation system for dynamoelectric machines and particularly for
salient pole generators or synchronous motors and the like. Generally,
in accordance with the teaching of the present invention, the rotor
is formed with an integrated end ring structure having radially
directed air slots or passageways formed by the end ring structure
to effectively cool the internal surfaces of the winding and pole
structure. In the preferred salient pole generator rotor, the winding
is placed on the salient pole to form part of a radial slot, and
thereby defining an internal cooling passageway having an air inlet
- and an outlet adjacent the opposite portions of the winding. Fan
blades are preferably integrally cast to the end rings to promote
the movement of air through the slot and thus, over the internal
surface or backside of the winding and the end faces of the poles.
The fan blades are preferably formed to further function as the
outer coil supports and as heat sinks for cooling of the rotor core
or poles.
In a preferred construction, a separate end ring portion is
cast in alignment with each pole. The end ring portion is formed as
an inverted U-shaped member with an outer amortisseur winding base
portion and a pair of inwardly projecting legs. The Outer base
portion includes integral coil support and fan projections and an
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inner inclined interior wall. With the coil or winding in place,
the pole, end ring legs and coil define an air slot having an inlet
opening at the shaft and an inclined discharge opening at the Outer
end of the winding. The inclined wall minimizes the tendency for
dust to accummulate within the slot.
Applicants have found that the present invention provides
a highly effective and efficient cooling of a dynamoelectric machine
winding and particularly the main field of a salient pole generator.
Description of the Drawin~ Fi~ures
The drawing furnished herewith illustrates a preferred con-
struction of the present invention in which the above advantages
and features are clearly disclosed as well as others which will be
readily understood from the following description.
In the drawing: -
Fig. 1 is an elevational view of a salient pole generator
with parts broken away and sectioned to show certain details of
construction;
Fig. 2 is an enlarged end view of the generator rotor with
parts broken away and sectioned to show the salient pole rotor
structure for illustrating a construction in accordance with the
present invention; and
Fig. 3 is a fragmentary axial section taken generally on
line 3-3 of Fig. 2 through one pole of the generator rotor.
Description Of The Preferred Embodiment
Referring to the drawing and particularly to Fig. 1, an
embodiment of the invention is shown in a salient pole A.C. generator
having an annular stator 1 with suitable feet 2. A salient pole
rotor unit 3 is rotatably mounted within the annular stator 1. The
rotor unit 3 is shown as a single bearing structure having the rotor
shaft 4 journaled in the front stator end bracket 5. An A.C. Exciter 5
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îs secured to the shaft 4 outboard of end bracket 5. A control box
7 is secured to the front end bracket 5 of the stator 1. The box 7
encloses the exciter 6 and provides for a connection of the A.C.
output power in accordance with any well-known construction. The
opposite end of the shaft 4 is provided with a driven input disc
unit 8 which is adapted to be connected directly to a fly wheen or
the like, not shown, for rotating of the rotor 3 within the stator l.
A fan unit 9 is secured to the shaft 4 between the disc unit 8 and
the end of the rotor unit 3 and is located within an S.A E. adaptor
10 secured to the aft end of stator 1. The fan unit 9 provides a
cDnventional æial air flow through the generator.
The present invention is particularly directed to the con-
struction of the salient pole rotor unit 3 and consequently no further
description of the other generator components is given because they
will be readily understood and provided by those skilled in the art.
The salient pole rotor unit 3 is shown as a four pole unit
having four equicircumferentially distributed radial poles 11 with
a field winding 12 similarly wound on each pole. The several poles
11 are shown formed of a stack of one piece laminations of suitable
magnetic material, with die cast end rings, amortisseur winding
and coil supports 13 secured to the opposite end faces of the rotor.
Each pole lamination is similarly constructed with a common
integral central mounting portion 14 having a shaft opening 15.
Each pole 11 projects radially outwardly from one side of the mounting
portion 14 and terminates in an outer winding retaining end member
16. The pole 11 has a width less than that of the mounting portion
14 and end member 16. The outer surface of each end member 16 is
shaped in the usual manner to complement the annular stator 1. The
outer end members 16 and the corners of the mounting portions 14
of the laminations are provided with openings 17 which in the
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lamination stack define axially extending openings. The laminations
with the openings aligned are integrally diecast with the end rings 13.
The end ring 13 may be formed of aluminum which fills the several
openings to form an amortisseur winding as well as to firmly clamp
the laminations in placer The end ring 13 is formed with a common
center 18 and four pole portions l9 being aligned one with each of
the rotor poles 11 to fully support the laminations. The die cast
pole assembly is suitably secured to the shaft 4 as by being heated
and then heat shrunk to the shaft and is further locked thereto as
by a suitable keyed connection 20. This structure provides a rigid
rotating assembly or rotor unit.
The winding or coil 12 is wound on each of the rotor poles
11 of the rotor-pole assembly. Each coil 12 is~ of course, a multiple
turn coil which extends over substantially the complete length of -
the projecting pole portion between the mounting portion 14 and the
outer end face member 16. The end ring 13 is also formed with integral
axially-extended coil retaining projections or supports 21 and 22
secured to the pole portion 19 and aligned with each pole ll.
Relatively short supports 21 are provided adjacent each of tha
- 20 opposite ends of the base 26 and somewhat longer projectlons or
supports 22 are provided therebetween to extend outwardly over the
corresponding end turns of the coil 12. The side turns of each
coil 12 generally lay beneath the end member 16 of each pole 11
and are securely locked in position. Thus under operating conditions
the centrifugal force on the coil 12 tend to move the coil turns
outwardly of the pole 11. Coil supports 21-22 and the outer end
member 16 serve to hold the coil 21 in position.
In accordance with a teaching of the present invention,
each pole portion 19 is specially formed to form a radially directed
-30 air slot 23 which is covered by the winding 12 on that pole. The
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radial length of the slot 23 is slightly greater than the radial
length of the winding 12 to define slot openings 24 and 25 to the
opposite ends of the winding 12.
Thus, the end openings 24 and 25 define an air circulating
path permitting air flow, as shown at 25a, radially through the end
ring member 19 and in the illustrated embodiment directly behind the
winding 12 and the end face lamination of the rotor pole 11. The
inner most opening 24 adjacent to the shaft 4 defines an air inlet
opening while the outer opening 25 adjacent the outer surface of the
winding 12 defines an exit or discharge opening. In the illustrated
embodiment of the invention, coil supports 22 are shaped to form fan
blades which improves air flow through the slot.
More particularly, as illustrated in Fig. 3 the end rings 13
which are integrally cast to the opposite ends of-the laminations
includes the pole portions 19 cast as inwardly opening rectangular
U-shaped members. The pole clamp portion 19 has a width slightly
smaller but generally complementing the end face of pole 11. The
base 26 of portion 19 is formed by the Outer ring which generally
conforms to the end member 16 of the pole 11, and which includes
- the amortisseur winding and the coil supports 21-22. The side arms
27 and 28 of the pole portion 19 extend inwardly from the base 26
to the integral central mounting corners 18 adjacent the central
mounting portion 14 of the rotor laminations.
The inner wall 29 of the outer base 26 is inclined or angled
to extend from the axial outermost face edge axially and radially
inwardly to the end lamination of the pole 11 as shown most clearly
in Fig. 3. The outer edge of inclined wall 29 is located outwardly
of the coil 12 and in the illustrated embodiment extends behind the
coil assembly.
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Each coil 12 is similarly constructed and includes an inner
insulating sheet 30 ~lich is wrapped about the winding pole 11 and
the side arms 27-28 of the pole portions 19. An outer relatively
heavy protective insulating end plate 31 abutts the underside of the
pole member 16 and the coil supports 21 22 of the end ring 13. The
winding 12 is a multiple turn winding which is suitably mechanically
or hand wound about the pole 11 including the integral side arms
27-28. The winding insulation sheet defines a closure wall over the
side arms 27-28 for the radial length of the winding to form the
passageway or slot 23. The slot 23 extends radially inwardly of the
coil 12 between the inner ends of the arms 27-28 common the corners
18 and also outwardly of coil 12 into the base portion 26. This
thus defines the slot extending directly between the interior surface
of the winding and the outer end face lamination of the rotor pole 11.
The coil supports 22 are specially formea to define fan blades
which promote the movement of air radially outwardly throu~h the slots
and thereby establish a highly effective cooling air flow over the
inner face of the winding and the end face of the-pole for effective
cooling of the winding.
During the operation of the generator, a continuous flow of
air is thereby established through each pole cooling slot to maintain a
highly effective and efficient cooling of the field winding. The
improved cooling ensures operation at a higher rated load without
exceeding the operating temperature limit of the windings and the
winding insulation.
The prese~t invention has been particularly used in generators
of 125 kw and larger for the effective cooling of the field winding.
The die cast end support structure with the integrated cooling
passageway is a low cost construction which maintains the necessary
integrity of the rotor structure in such large machines.
11371~8
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Although shown in a preferred construction, various modi-
fications may be made within the teaching of the present invention
which is particularly directed to the shaping of the end rings
adjacent the poles to define cooling passageways. For example,
the discharge opening of the slot may be located completely out-
wardly of the coil, and the air slots may only be provided adjacent
one end of the rotor. The invention may also be applied to other
generator and motor constructions. For example, the rotor may be
formed as segmented rotor lamination or as a consequent pole rotor.
These and other modifications depending on the particular machine
design and the like can be readily provided by those skilled in the
art and no further description thereof is given.
