U.S. patent number RE28,478 [Application Number 05/370,349] was granted by the patent office on 1975-07-08 for winding support system for a dynamoelectric machine.
This patent grant is currently assigned to General Electric Company. Invention is credited to John J. Bahn, Almy D. Coggeshall, Richard T. Maher, John B. Waldbillig.
United States Patent |
RE28,478 |
Bahn , et al. |
July 8, 1975 |
Winding support system for a dynamoelectric machine
Abstract
.Iadd.An improved insulating support system for the conducting
members of the stator of a dynamoelectric machine. Inner and outer
radially spaced support members are secured together with tension
members passing among the armature bars so that the entire group of
end turns is held as a rigid structure. Conformable pads are used
between the bars and the support members to completely support the
bars. The support framework is mounted in special brackets to be
axially slidable with respect to the stator casing. .Iaddend.
Inventors: |
Bahn; John J. (Schenectady,
NY), Coggeshall; Almy D. (Schenectady, NY), Maher;
Richard T. (Wilton, NY), Waldbillig; John B.
(Schenectady, NY) |
Assignee: |
General Electric Company
(Schenectady, NY)
|
Family
ID: |
26710156 |
Appl.
No.: |
05/370,349 |
Filed: |
June 15, 1973 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
033808 |
Jun 3, 1960 |
03089048 |
May 7, 1963 |
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Current U.S.
Class: |
310/260; 310/231;
310/269; 310/270 |
Current CPC
Class: |
H02K
3/505 (20130101); H02K 2203/09 (20130101) |
Current International
Class: |
H02K
3/50 (20060101); H02k 003/46 () |
Field of
Search: |
;310/194,230,231,235,260,264,270 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1,127,805 |
|
Dec 1956 |
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FR |
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1,193,411 |
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Apr 1959 |
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FR |
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436,568 |
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Nov 1922 |
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DT |
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Other References
New Large Short Circuit Testing Generators, by C. E. Kilbourne,
AIEE paper, No. 52-221, Oct. 1952, pp. 829-836..
|
Primary Examiner: Budd; Mark O.
Attorney, Agent or Firm: Ahern; John F. Mitchell; James
W.
Claims
What we claim as new and desire to secure by Letters Patent of the
United States is:
1. A winding support system comprising a stator having a group of
transversely spaced insulated conducting members, .Iadd.extending
beyond respective ends of said stator and diverging radially
outwardly from the axis of said stator thereat, .Iaddend.framework
means constrictable in a direction transverse to said
.Iadd.radially diverging .Iaddend.conducting members comprising
first and second substantially parallel .Iadd.axially disposed
.Iaddend.support members disposed on either side of said group of
conducting members, .Iadd.crossing said conducting members at an
angle, .Iaddend.said first support members being supported by said
stator and said second support members each being movable relative
to one another, first means connected between said first and second
support members for constricting the framework, and a plurality of
conformable pads of thermosetting material disposed between
adjacent conducting members and between outer conducting members
and the support members, whereby the framework means can be
constricted with the first means and the conformable pads cured to
hold the conducting members in ridigly spaced relationship.
2. A stator end winding support comprising a stator having at least
one row of circumferentially spaced armature bars projecting beyond
the stator end .Iadd.and diverging radially outwardly thereat
.Iaddend.said armature bars being subject to thermal expansion and
contraction in an axial direction, constrictable framework means
including a plurality of first and second support members lying
radially inward and outward of and crossing said armature bars at
an angle, said first support members being movable with respect to
one another, a plurality of conformable pads of thermosetting
material disposed at the intersections of the inner and outer
support members with the armature bars, means connected between
said first and second support members to constrict the framework
about the armature bars, whereby the thermosetting conformable pads
can be depressed to conform to the bars, and means supporting said
framework from the stator for substantially unrestrained axial
movement therewith, whereby the projecting armature bars are held
in a rigid cage which is axially slidable to compensate for thermal
expansion and contraction of the armature bars with respect to the
stator.
3. A stator end winding support comprising a stator having at least
one row of circumferentially spaced armature bars projecting beyond
the stator end and .[.skewed .]. .Iadd.diverging radially outwardly
thereat .Iaddend.with respect to the stator axis, said armature
bars being subject to thermal expansion and contraction in an axial
direction, a plurality of circumferentially spaced first support
members projecting from the stator coplanar with the stator axis
and crossing said armature bars at an angle, a plurality of
circumferentially spaced second support members disposed on the
other side of the armature bars from said first support members and
substantially radially aligned with the first support members,
tension means connecting the inner and outer support members with
one another for rigidly supporting the intersecting armature bars
therebetween, and second means supporting at least the first
support members from the stator for substantially unrestrained
axial movement therewith, whereby the projecting armature bars are
held in a rigid framework which is axially slidable to compensate
for thermal expansion and contraction of the armature bars with
respect to the stator.
4. A stator end winding support comprising a stator having at least
one row of circumferentially spaced armature bars projecting beyond
the stator end and .[.skewed .]. .Iadd.diverging radially outwardly
thereat .Iaddend.with respect to the stator axis, said armature
bars being subject to thermal expansion and contraction in an axial
direction, a plurality of circumferentially spaced first support
members projecting from the stator coplanar with the stator axis
and crossing said armature bars at an angle, a plurality of
circumferentially spaced second support members disposed on the
other side of the armature bars from said first support members and
substantially radially aligned with the first support members, a
first group of conformable thermosetting pads disposed between the
first support members and the armature bars, a second group of
conformable thermosetting pads disposed between the second support
members and the armature bars, adjustable tension means securing
the inner and outer support members together for constricting the
support members to depress the thermosetting pads against the
armature bars where they cross the first and second support
members, and means supporting at least the first support members
from the stator for substantially unrestrained axial movement
therewith, whereby the projecting armature bars are held in a rigid
framework which is axially slidable to compensate for thermal
expansion and contraction of the armature bars with respect to the
stator.
5. A stator end winding support comprising a stator having
circumferentially spaced longitudinal winding slots therein, a
circumferential row of bottom armature bars .Iadd.having slot-lying
portions .Iaddend.disposed in said slots .[.and .]. .Iadd., said
bottom armature bars .Iaddend.projecting beyond the stator end .[.,
said bottom bars each being displaced.]. .Iadd.and each extending
.Iaddend.circumferentially from the slot and diverging radially
from the stator axis, a circumferential row of top armature bars
.Iadd.having slot-lying portions .Iaddend.disposed in said slots
.[.and .]. .Iadd., said top armature bars .Iaddend.projecting
beyond the stator end .[., said top bars being displaced .].
.Iadd.and each extending .Iaddend.circumferentially in an opposite
sense from the bottom bars and diverging radially from the stator
axis, a plurality of circumferentially spaced first support members
projecting from the stator substantially coplanar with the stator
axis and defining surfaces diverging radially therefrom and
uniformly spaced from one row of armature bars, a plurality of
circumferentially spaced second support members projecting from the
stator coplanar with the stator axis on the opposite side of the
bars from the first support members and radially aligned with said
first support members, said second support members defining
surfaces diverging radially from the stator axis and uniformly
spaced from the other row of armature bars, circumferential
separating means disposed between the top and bottom bars, a first
group of conformable pads disposed in the spaces between the first
support members and the bars, a second group of conformable pads
disposed in the space between the second support members and the
bars, adjustable tension means securing the first and second
support members together for squeezing the pads against the
armature bars, and support bracket means connected between said
first support members and the stator, to allow axial movement of
the first support members with respect to the stator, whereby the
projecting armature bars are held in a rigid framework which is
axially slidable to compensate for thermal expansion and
contraction of the armature bars with respect to the stator.
6. The combination according to claim 5 wherein the brackets each
comprise a stationary member secured to the stator including a
bifurcated flanged portion axially enclosing a part of a first
support member, pin means passing through holes defined by the
first support member and the bifurcated flange and axially slidable
within said flange holes, and friction reducing pads supporting the
pin means for axial movement in the flange.
7. The combination according to claim 5 wherein circumferential
hoop members are secured to said circumferentially spaced first
support members to provide lateral support therefor, and
conformable pads are disposed between said hoop members and the
armature bars adjacent said first support members.
8. The combination according to claim 5 wherein a plurality of
arcuate baffle segments are disposed on said support members
radially inward from said top armature bars in circumferential
alignment, whereby said baffle segments together define a baffle
ring radially inward from the end turns.
9. For use on a dynamoelectric machine stator having a
circumferential structural member supporting the end turns of the
stator winding, the combination of a plurality of axially spaced
collecting rings electrically connected to said end turns, first
stationary means restraining said collecting rings in an axial
direction, a plurality of rigid spacer means interposed between
said collecting rings, second means movable in an axial direction
relative to one another and with respect to said first means and
transversely to the collecting rings, a plurality of conformable
thermosetting pads disposed between the collecting rings and said
spacer means, and third adjustable means causing the second means
to move toward the first stationary means constricting the
thermosetting pads to hold the collecting rings in a rigid
framework.
Description
This invention relates to an improved insulating support system for
the conducting members of the stator of a dynamoelecric machine and
more particularly it relates to an integral end turn support
framework for a large generator which is free to move axially as
the stator windings expand and contract thermally.
The end turns of a dynamoelectric machine stator are the projecting
portions of the armature bars which extend outwardly from
longitudinal stator slots. The end turns are necessary in order to
reverse the direction of the armature bar and to circumferentially
displace the end of the bar so that it can enter a slot almost
180.degree. from the slot from which it emerged. The end turns must
also diverge radially from the stator axis in order that they will
not obstruct the rotor of the dynamoelectric machine which is
turning in the stator bore. Consequently, the stator end turns
assume a rather complicated configuration in that they are skewed
with respect to the stator axis and lie generally tangentially
about a frusto-conical surface of revolution concentric with the
stator axis. When there are two separate armature bars in each
slot, these being known as "top" (radially inner) and "bottom"
(radially outer) bars, one practice is to bend the top bars so that
they lie tangentially in one direction about this frusto-conical
surface and to bend the bottom bars in the opposite tangential
direction about the surface of revolution. The matter is further
complicated by the fact that, although the top and bottom bars are
closely adjacent at the location where they emerge from the slot,
they must spread radially with respect to one another as they move
away from the stator so that space will be afforded for a series
loop connecting a top bar to a bottom bar.
With this background in mind, it will be appreciated that there are
many difficulties in devising a suitable structure for supporting
the insulated armature bars in the end turn region. The problem has
become more acute with the advent of more rigid thermosetting
insulation for the armature bars, which do not yield as freely to
conform to the support structure as the older types of insulation,
for instance the commonly used asphalt insulation.
The magnitudes of the various forces exerted on the armature bars,
both in the slot region of the stator and in the end turn region
are substantial. Various magnetic forces will act upon the armature
bars of a large turbo-generator, for example during unbalanced load
or "short circuit" conditions. In addition, substantial heat is
generated by the passage of electric current through the armature
bars and, even though effective gas or liquid cooling of the bars
is provided, the thermal expansion and contraction of the bars with
respect to the stator slots containing them will tend to move the
end turns apart in an axial direction with respect to the
longitudinal center of the stator.
One support method which has been used extensively to give the
strength, yet the yieldability, required of an end winding support
system has been to lash the projecting armature bars to a series of
circumferential support "hoops." With this method, each bar is
individually tied to each loop with a strong flexible cord, such as
glass cord impregnated with a resin such as varnish. In a typical
construction, there may be around fifty top bars and fifty bottom
bars to be lashed to four circumferential hoops at either end of
the stator, or on the order of 800 separate ties to be made. It
will be appreciated that this is a tedious and time-consuming
procedure.
In addition to separately securing the armature bars to a support
structure with the foregoing method, they must be separated and
secured with respect to one another. One method for accomplishing
this is to use small rigid spacer blocks separately lashed to each
armature bar. The bars are then tied together, compressing the
blocks between bars. Another method is to use a rope member of
fiberglass passing around a group of bars with the spacer blocks in
alignment.
In U.S. Patent 2,994,735 issued on August 1, 1961 to Walter L.
Marshall and Almy D. Coggeshall and assigned to the assignee of the
present application, a type of "conformable" spacer block is
disclosed as a substitute for a rigid separately lashed block.
Another "conformable" spacer block is disclosed in U.S. Patent
2,980,757 issued April 18, 1961, to Almy D. Coggeshall and Harold
R. Shirk and assigned to the assignee of the present
application.
This slow and expensive method for literally "sewing" the support
system together has naturally led to a search for a better
arrangement. Two of the greatest problems to be overcome were as
follows:
First, there is a slight variation both in bar cross-section and in
bar configuration which is unavoidable in manufacture, especially
in the end turn portions which must follow the complicated involute
configuration described above.
Secondly, a support structure which rigidly fixes the end turns to
the stator itself restricts the thermal expansion and contraction
of the armature bars in the slots.
Accordingly, one object of the present invention is to provide an
improved end winding support system which holds the end turns in a
rigid framework yet which allows thermal movement of the
framework.
Another object is to provide a conforming framework which adjusts
itself to irregularities of conducting members while locating them
with respect to one another.
Another object is to disclose a special axially slidable support
bracket suitable for permitting axial movement of an end turn
supporting framework with respect to the stator itself.
Another object is to provide an improved mounting for a segmental
baffle plate restricting the flow of coolant to the "air gap.
The subject matter which is regarded as the invention is
particularly pointed out and distinctly claimed in the concluding
portion of the specification. The invention, however, both as to
organization and method of practice, together with further objects
and advantages thereof, may best be understood by reference to the
following description taken in connection with the accompanying
drawing in which:
FIG. 1 is a perspective fragmental view showing the lower part of
one end of the stator, illustrating the disposition of the armature
bars with respect to the stator;
FIG. 2 is a horizontal elevation, partly in section, showing the
support system at one end of the generator stator; and
FIG. 3 is an exploded detail view of the support bracket which
holds the framework for axial movement.
Generally stated, the invention is practiced by providing inner and
outer radially spaced support members secured together with tension
members passing among the armature bars so that the entire group of
end turns is held as a rigid structure. "Conformable" pads are used
between the bars and the support members to completely support the
bars. The support framework is mounted in special brackets to be
axially slidable with respect to the stator casing so that thermal
"breathing" can take place. The inner support members serve as a
mounting structure for a segmented "air gap" baffle.
Referring now to FIG. 1 of the drawing, a perspective view is shown
of a portion of a stator 1 which includes a circumferential flange
ring seen at 2. The rotor (not shown) turns in bore 3 shown near
the top of FIG. 1. As will be familiar to those skilled in the art,
the main structural members of the stator including the flange ring
2 and other support members (not shown) enclose and support a large
number of slotted core laminations defining the stator central bore
3 and through which pass the slot-lying portions of top armature
bars 4 and bottom armature bars 5. Top bars 4 bend both
circumferentially and radially as they come out of the slot and
continue in an involute curve as shown at 4a in FIG. 1. Similarly
bottom bars 5 also diverge radially but in an opposite
circumferential sense as seen at 5a. Thus these portions 4a and 5a
are both "skewed" with respect to the stator axis, as will be plain
from the perspective view in FIG. 1. A clearer understanding may be
had by reference to the horizontal elevation of FIG. 2. There the
bar portions 4a, 5a have been rotated into the plane of the
drawing, although it is understood that actually they run in
opposite circumferential directions as well. Portions 4a, 5a are
bent in an involute-type configuration so as to lie tangentially to
a frusto-conical surface of revolution taken about the stator axis.
FIG. 2 also shows a portion of the generator rotor 6 which rotates
in bore 3 of the stator.
A top bar on one side of the stator circumference is connected with
a bottom bar approximately diametrically opposite, this connection
being made with a "series loop" 8. It will be understood that
series loop 8 is rotated into the plane of the drawing in FIG. 2 in
order to show the proper spacing of the members in a radial
direction and that it does not actually connect the portions 4a and
5a emerging from the same slot.
At intervals about the stator circumference, power is withdrawn
from the armature windings through flexible leads 9 passing to
circumferential collecting rings one of which is shown at 9a.
Collecting rings 9a, in turn, are connected to the high voltage
outlet terminals (not shown).
The support structure holding collecting rings 9a in position is
shown generally at 10. Several such collecting ring support
structures 10 are circumferentially spaced about the stator outside
of the end turns and are attached to circumferential flange 2 by
bolting or welding to radial webs 2a preferably made integral with
the circumferential flange 2.
The collecting ring support structure is supported by means of a
flange member 10a, the under side of which is bolted to an axially
extending lower member 10b. An upper angle piece shown generally at
10c has a short leg 10d abutting the face of member 10a to prevent
its movement toward the stator and a long leg 10e passing over the
collecting rings 9a and substantially parallel with lower member
10b. The long leg 10e is supported in a sliding support 10f by
means of a hole 10g receiving the end of long leg 10e. Sliding
support 10f is free to move transversely to collecting rings 9a by
virtue of its lower side being mounted to slide in a groove 10h in
lower member 10b. The sliding support 10f also has a lower flange
10i which supports the first collecting ring 9a.
A spacer block 10j is disposed between the innermost collecting
ring and short leg 10d. Thus it will be apparent that if support
block 10f is moved toward the stator, all of the collecting rings
9a will be constricted between support 10f and spacer 10j.
Interposed between each collecting ring 9a is an angle piece 10m,
the lower leg of which supports the outside of the collecting ring.
Between each collecting ring and the long leg of angle pieces 10m
are disposed pads of conformable material 10n. These are preferably
composed of insulating material and should be resilient or pliable
in order to conform to irregularities of the collecting rings. Pads
10n are preferably composed of thermosetting material so that the
resin may be cured after the collecting ring framework has been
constricted about the collecting rings. An additional pad of
conformable material 10p is disposed between the tops of the
collecting rings and upper member 10c.
The means for constricting the support so as to cause pads 10n, 10p
to conform are comprised of a beveled washer 10q held by a diagonal
bolt 10r passing through sliding support 10f as shown. Thus when
bolt 10r is tightened, the component of force produced transverse
to the collecting rings will cause sliding support 10f to move
toward spacer 10j, causing pads 10n, 10p to conform to the shape of
the rings.
Turning now to the support system for the armature end windings,
the top bar extending portions 4a and the bottom bar extending
portions 5a are held by inner support members 11 and outer support
members 12. These inner and outer support members 11, 12 are
circumferentially spaced about the stator bore and extend generally
axially and radially outward therefrom. Thus members 11, 12 are
disposed substantially coplanar with the stator axis. In the
embodiment shown, there is a pair of support members 11, 12 for
each three stator slots. Inner support members 11 define support
surfaces 11a which lie parallel to the frusto-conical surface of
revolution, i.e. each surface 11a of an inner support member 11
diverges as the element of a cone from the stator axis while the
bar portions 4a cross it diagonally. Similarly, the outer support
members 12 define support surfaces 12a which also diverge as
elements of a cone from the stator axis while bar portions 5a cross
it diagonally. Surfaces 11a, 12a are not exactly parallel but must
diverge radially from one another slightly so as to allow for the
fact that the radial spacing between top and bottom bars near the
slot, as shown at 13, is less than the radial spacing between top
and bottom bars at the series loop, as shown at 14.
Inner and outer support members 11, 12 are preferably constructed
of high strength insulating material. A suitable material for this
use is "Permali," which is the trade name of a laminate constructed
of thin wood veneers bound with a synthetic thermosetting resin and
sold by Permali, Inc.
Surfaces 11a, 12a of support members 11, 12 are furnished with
longitudinal grooves 11b, 12b respectively. The grooves may vary in
depth as indicated at 11c, 12c to form a lock or key as will be
amplified at a later point. Disposed in grooves 11b, 12b and
extending above surfaces 11a, 12a are elongated pads of
thermosetting resin 15. These are placed in the grooves during
assembly in an uncured or pliable state and several suitable
compositions are commercially available, such as the thermosetting
resin sold under the trade name "Glaskyd 1901" by Perrysburg
Laboratories. This material has the ability to cure to a rock-like
hardness at an elevated temperature and possesses both good
compressive strength and good insulating qualities.
Inner and outer support members 11, 12 are securely fastened to one
another by tension members illustrated by a bolt 16 and a special
insulating tension member 17. Member 17 may be manufactured as
disclosed in U.S. Patent 3,024,302, issued on March 6, 1962, to
Almy D. Coggeshall and further reference will not be made to it
herein, except to note that it consists of a glass rope 17a
impregnated with thermosetting resin and secured to T-shaped
adjustable bolts 17b.
The bolt 16 may be considered to represent any suitable tensioning
means, but as shown here comprises a steel rod 16a threaded at one
end into a bracket 12d secured to outer support 12 and secured at
the other end to inner support member 11 in a recess 11d cut
therein. It will be apparent that bolt 16 and the insulating member
17 may be drawn up to increase the tension between support members
11, 12 pulling them toward one another and thus compressing the
pads of thermosetting material 15. In other words, the support
members 11 are forced radially outward and the support members 12
are forced radially inward. It will be re-emphasized at this point,
as more clearly illustrated in FIG. 1, that several extending
portions 4a, 5a cross a pad 15 diagonally and, since the pads are
pliable or "conformable," the bars will depress them at the point
where each armature bar crosses a support member.
In order to provide a radial separator between portions 4a, 5a of
the armature bars, spacers 18, 19, 20 of a suitable rigid
insulating material are employed and are interposed between
portions 4a, 5a. These take the compressive load between portions
4a, 5a applied by tension members 16, 17. Arcuate spacer 19 is of a
greater thickness than arcuate spacer 18 in order to provide for
the radial divergence of the top bars with respect to the bottom
bars. Radial spacers 20, aligned with support members 11, 12 may
also be employed. These spacers 18, 19, 20 may be pads of
thermosetting material as described previously or may be of other
suitable insulating material.
In order to provide additional circumferential or lateral support
for the spaced outer support members 12, rigid insulating hoops 21
are employed which are secured to support members 12 by suitable
means such as pins 21a. Hoops 21 each have a circumferential groove
21b in which are placed additional pads of thermosetting resin 22,
which may also be of the Glaskyd 1901 composition. Pad 22 is also
in its uncured, pliable state during assembly.
All of the conforming pads 10n, 10p, 15, 18, 19, 20 and 22
mentioned herein may be enclosed in pre-stretched rubber sleeves to
add to their conforming properties as more particularly described
in the aforementioned U.S. Patent 2,994,735, which is assigned to
the assignee of the present application.
The hoops 21 are all preferably high strength rigid insulating
members. A suitable material for their construction is fibrous
glass bonded with a thermosetting polyester resin molded to the
cross-sections shown and cured.
The foregoing inner and outer support members 11, 12, tension
members 16, 17, spacers 18, 19, 20 and hoops 21 together constitute
a support framework or "cage" which can be constricted about the
bars to hold the end turn portions firmly in position. The
framework, as it is constricted, conforms to irregularities in the
bars by virtue of the "uncured" or pliable thermosetting pads,
although resilient pads might also be employed. When the framework
is tightly secured about the end turns, it may be considered
substantially rigid.
In order to permit this rigid framework to move axially with
thermal expansion and contraction of the slot-lying portions of the
armature bars, special support brackets 25 are used to secure the
outer support members 12 to stator flange 2. Reference to FIGS. 2
and 3 of the drawing will show that the bracket comprises a base 26
secured to flange 2 by suitable means such as bolts 27. Base 26
supports a bifurcated portion consisting of extending parallel
flanges 28, which each define a rectangular recess 28a. Outer
support member 12 is held between extending flanges 28 by means of
a special pin 29. The central portion 29a of pin 29 is cylindrical
and fits with close clearance in a cylindrical recess 12c of the
support member 12. The two ends 29b of pin 29 have a rectangular
cross-section and extend into recesses 28a of flanges 28 on either
side of the support member.
Friction-reducing bearing pads 30 are arranged in recess 28a above
and below the pin end portions 29b so that portion 29b fits snugly
between them, while allowing the pin to slide in an axial
direction. Bearing pads 30 serve to reduce the sliding friction and
a suitable material for pads 30 is a "self-lubricating" Teflon
substance sold as "Chemloy 770-07-19" by Crane Packing Company.
Cover plates 31 complete the bracket and prevent the pads 30 from
coming out of the recesses 28a and also force the sides of the pads
30 against the outer support member 12 to provide a damping or
"snubbing" action.
It will, of course, be noted that the axial length of recess 28a is
greater than the corresponding axial dimension of rectangular
portion 29b of the pin. This difference in dimension allows the
pin, carrying with it support member 12, to slide to and from the
generator flange 2 in an axial direction. Thus brackets 25,
supporting the members 12 by pins 29, constitute means supporting
the framework for axial movement with respect to the stator. Two
such support brackets 25 are used to secure each outer support
member 12. The purpose of the cylindrical portion of the pin 29 is
to allow the brackets 25 to rotate on members 12 to compensate for
any slight misalignment of the brackets or for variations in the
large circumferential mounting flange 2.
The inner support members 11 serve as a means for supporting the
"air gap" baffle 32. The air gap baffle is used to restrict the
flow of cooling gas between the end turns and a retaining ring 6a
forming a portion of the rotor. Previous constructions have
necessitated attaching the air gap baffle to the stationary stator
structure inasmuch as the end turn support structure was composed
primarily of lashing and serve no means for supporting the air gap
baffle. With the improved end turn support system described, the
air gap baffle 32 is constructed in arcuate segments which are
attached to radially inner support members 11 by means of bolts 33.
Arcuate members 32 together form a ring about the rotor defining
clearances with the rotor retaining ring 6a to restrict the flow of
coolant. It will be observed that baffle plate 32 moves axially
along with the end winding support system when the windings expand
and contract thermally. Since the outer surface of retaining ring
6a is cylindrical, such axial movement does not affect the
clearance space between baffle 32 and retaining ring 6a.
The method of assembly and operation of the improved end winding
support system will now be described. The support brackets 25 may
be attached to outer support member 12 as a sub-assembly by
aligning the holes 12c between the flanges 28 and inserting the
pins 29 through recess 28a. The cylindrical portion 29a of the pins
is small enough to pass through recess 28a before the pads 30 are
inserted. The pads 30 are then inserted and cover plates 31 are
attached. The width of pads 30 is slightly greater than the
thickness of flanges 28. Thus cover plates 31 force bearing pads 30
inward slightly beyond the inner surface of flanges 28 so that the
edges of the bearing pads also serve to prevent rubbing of the
outer support member 12 against the inner surfaces of flanges 28 as
the support member moves.
For one method of assembly the brackets 25 holding support members
12 are then individually bolted to flange 2. The rings 21 are then
put in place using pins 21a and thermosetting pads 15, 22 inserted
in their respective grooves.
In an alternate method of assembly, the entire outer cage
comprising support members 12, brackets 25, rings 21, etc., may be
pre-assembled in a large jig and then the jig moved to the end of
the generator stator. Here the bearing brackets 25 are bolted to
flange 2 with bolts 27.
The bottom bars 5 are inserted and held in place temporarily, after
which the top bars 4 are inserted, separating them with rings 18,
19, 20. As the assembly proceeds, the inner support members 11 are
aligned radially with and secured to the outer support members 12.
The tension members consisting here of bolt 16 and insulating
member 17 are attached and drawn up snugly, depressing the
conformable pads 15, 22 where the armature bars cross the supports.
The foregoing procedure is carried out until the entire cage or
framework has been assembled on both ends of the stator. Additional
tightening of the tension members may then be required to
completely remove any looseness as the conformable pads 15, 22
adjust for any misalignment or irregularities. Likewise, the
cylindrical central portions 29a of pins 29 allow angular
adjustment due to irregularities in flange 2. For most
installations, variously disposed compression blocks or separators
(not shown) may be required to provide desired separation between
bars. A very effective block is a "conformable" block such as
described in the aforementioned U.S. Patent 2,980,757. Rigid blocks
may also be employed, however, which may be separately lashed to
the bars or held in place by a single lashing passing around a
group of bars.
After all of the tension members 16, 17 have been taken up snugly,
the entire stator is placed in a curing oven and the temperature is
raised to cure the thermosetting resin in pads 15, 17, 18, 19, 20,
22. Upon completion of the curing cycle, the resin is cured to a
rock-like hardness, with permanent indentations where the armature
bars intersect with the support members. This results in a
"conformed" framework or molded cage holding the armature bars
rigidly in position. Of course, if resilient pads are used instead
of thermosetting pads, this curing step will be unnecessary.
It may also be noted that, prior to the curing and while the
tension is being applied by members 16, 17, pads 15 are also
squeezed into the recesses 11c, 12e in the bottom of grooves 11b,
12b. Then when the pads 15 cure, these portions squeezed into
recesses 11c, 12c form a "lock" preventing pads 15 from sliding
longitudinally along the support member.
The air gap baffle segments 32 may be attached later after the
rotor of the generator is in position.
In operation, the entire framework encasing the end turns is free
to move axially in response to thermal expansion and contraction of
the slot portions of the bars by virtue of the pins 29 sliding
axially in brackets 25. This serves to prevent setting up any
stresses in the armature bars which may tend to crack the
insulation. Pins 29, however, prevent any radial movement of the
end turns which may result from magnetic forces imposed on the
windings.
The ease of assembly compared to previous methods of assembly
constituting individual lashing of the armature bars will be
readily apparent. The structure outlined provides a molded cage
which exactly conforms to the configuration of the end turns and
yet which allows the complete end turn structure to move axially
when the armature bars are heated. It will be observed that the end
turn portions of the bars are also free to expand along their own
lengths in respone to an increased temperature, since the bars
merely expand longitudinally through the permanent indentations
formed in the thermosetting pads.
The collecting ring support structure is, of course, fixed to the
stator and needs no provision for thermal movement. The flexible
leads 9 allow for relative movement between the end turn framework
and the collecting ring framework.
One possible modification of the invention would be to support the
inner support members 11 instead of outer support members 12 from
the stator for axial movement therewith, or perhaps to support both
the inner and outer support members for axial movement. Such
modifications are naturally within the scope of the invention.
Various substitutions may be made for the tension means represented
by bolt 16 and member 17. In place of brackets 25, axial pins
attached to either support members 12 or flange 2 and sliding in
holes in the opposite members would provide a suitable axially
slidable support. The invention is also applicable to stators
having one, three, or more, armature bars in each slot rather than
the two armature bars in the embodiment shown.
While there has been described what is at present considered to be
the preferred embodiment of the invention, it will be understood
that other modifications may be made therein, and it is intended to
cover in the appended claims all such modifications as fall within
the spirit and scope of this invention.
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