Method of retrofitting a stator end winding

A stator end-winding system is proposed in which the bars of the winding are bent outwards and describe a hollow cone. The supporting proceeds by a wedge-like braced inside ring, a segmented outside ring and supports which also have a wedging effect. The bracing of the inside ring and outside ring is made by tie rods, the outside ring being azimuthally tensionable. Therefore, it can be placed over the above-mentioned cone described by the bars without the necessity of disassembling the stator end-winding system.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a stator end-winding system of the stator 
of an electric machine having a array of bars expanding coaxially to the 
axis of the machine at its end areas in the shape of a hollow cone, and 
having a means for supporting same including an inside-ring which extends 
cone-like along a substantial axial portion of the cone-shaped array of 
bars. It relates also to a retrofitting set for a stator end-winding 
support system of an electric machine having a array of bars expanding 
outwards coaxially to the axis of the machine at its end areas in the 
shape of a hollow cone. It relates further to a method of retrofitting a 
stator end-winding system of an electric machine having an array of bars 
expanding outwards coaxially to the axis of the machine at its end areas 
in the shape of a hollow cone, and a support system for same which 
includes supporting members located at the inside and outside relative to 
the cone-shaped array of bars. 
The high dynamic forces acting during the operation at locations of 
resonance of the mechanical stator end-winding system of stator 
end-windings and the problems resulting therefrom, specifically in the 
case of large electrical machines, specifically of turbo-generators with a 
directly hydrogen-cooled stator winding, are generally known. The 
appearance of exciting forces of specific frequencies can not be 
influenced at a given operation wherewith it is endeavoured to move the 
locations of resonance of the mechanical stator impedance as much as 
possible away from the exciting frequencies occuring during the operation. 
In operation, operational vibrations, specifically in the case of 
resonance, lead to high dynamic stresses of the end-windings, specifically 
in case of turbo-generators, which may lead to a loosening of the entire 
stator winding assembly. Abrasions of insulation and damages at the stator 
and the results thereof lead in turn to long shut-down times for a repair 
of the stators. Due to the known direct hydrogen cooling of the stator 
winding of generators the number of slots of the stators is kept as low as 
possible resulting in large dimensions of the bars of the stator and 
accordingly in large masses. Because the dynamic forces are proportional 
to the masses acted upon, aside from the acceleration of the vibrations, 
accordingly high stresses are the result, specifically of the end-winding 
assembly. Accordingly, there exists on the one hand the problem in the 
case of the known stator end-winding systems to be able to absorb the 
large dynamic forces. On the other hand such stator end-winding systems, 
also if they have been improved regarding dynamic stresses, must be 
subjected from time to time to maintenance work whereby the generally 
complicated and, regarding the maintenance, difficult structural designs 
of stator end-winding systems lead to corresponding shut-down times: A 
repair of most of the known stator end-windings means a new winding of the 
stator. 
2. Description of the Prior Art 
The U.S. Pat. No. 4,488,179 discloses a stator end-winding system, 
specifically of a turbo-generator, including an array of bars expanding 
outwards coaxially to the axis of the machine at its end areas in the 
shape of a hollow cone and a supporting system for same. The supporting 
system includes a plurality of rings located inside of the hollow cone 
formed by the array of bars, and at the outside a massive conically 
extending outside ring. The bars of the winding are braced therebetween by 
means of tie rods and intermediate rings. The outer massive ring is, 
furthermore, axially anchored at the stator body. Due to the generally 
used cone-shaped array of the bars which expands axially towards the 
outside it is not possible to revise or repair, respectively the stator 
end-winding support system without a dismounting of the bars which means a 
new winding of the stator. Furthermore, a plurality of weakly dimensioned 
inside rings lead to a merely low stiffness or rigidity, respectively of 
the stator end-winding unit because the bracing forces act more or less 
only along straight lines and do not act uniformly at the cone of the 
stator bars. 
The U.S. Pat. No. 4,525,642 discloses a stator end-winding again with an 
array of bars expanding conically outwards and an anchoring between the 
body of the stator and the outer support of the bars at the stator 
end-winding in order to absorb thermally caused expansions between the 
arrangement of bars and the body of the stator. 
U.S. Pat. No. 4,563,607 discloses a stator end-winding again with an array 
of bars expanding outward coaxially to the axis of the machine at its end 
areas in the shape of a hollow cone and a support for same as well, which 
latter, located at the inside includes clamps extending under the bars and 
holding same and being radially braced to upper plates which are anchored 
at the body of the stator and are substantially axially aligned. The 
plates and the clamps are braced together by means of bracing rings 
located between the bars of the bar array. The support is mounted to the 
stator body. The small masses of the inner and outer members used here for 
the support and braced against each other have a negative effect upon the 
damping of the resonance behaviour of the stator end-winding such that, 
together with the line-contact bracing only a unsufficient rigidity of the 
stator end-winding is achieved. 
U.S. Pat. No. 4,808,873 discloses basically to insert a suitable padding 
material between the bars of the array of bars. 
The European Patent document EP-A-0 309 096 discloses further to forsee an 
outer support in the form of an outer ring at a stator end-winding having 
again a array of bars expanding in the form of a hollow cone in order to 
embrace the bars by tensioning bands extending from said outer ring. 
Again, due to the small installed supporting masses and line-contact like 
bracings the resonance behaviour of this stator end-winding is 
unsatisfactory due to the lack of rigidity. Additionally, due to the fact 
that the ring is displaced axially inwards from the largest outer diameter 
of the cone of the arrangement of bars a revision of the stator 
end-winding is not possible but rather only a disassembly along with at 
least a partial removal of the bars. 
Now, the Swiss Patent Specification 634 695 discloses a stator end-winding 
of an electric machine having an array of bars expanding outwards 
coaxially to the axis of the machine at its end areas in the shape of a 
hollow cone, whereby a support is provided which includes an inside ring 
which extends cone-like along a substantial axial portion of the 
cone-shaped array of bars, and includes an outside ring system at the end 
of the arrangement of bars which is radially braced onto the inside ring 
by means of tie rods via the array of bars. In order to make the 
maintenance activity of the stator end-winding easier in spite of the 
forseen outside ring, i.e. to remove the inside ring and outer ring 
without having to disassemble the array of bars itself, the outside ring 
is located directly in the area of a bracket portion interconnecting the 
inner and outer bars, which bracket portion defines at the end area of the 
cone substantially a cylindrical surface such that, after the unscrewing 
of the tie-rods, the outside ring located at the end area can be pulled 
off. The outside ring and the inside ring as well are, however, 
additionally locked axially such that a disassembling remains relatively 
cumbersome. In order to benefit by a simpler disassembling procedure after 
all the relatively weakly dimensioned outside ring is arranged in such a 
manner at the cylindrical end area portion of the arrangement of bars that 
the radial bracing with the inside ring proceeds only at the end area of 
the bars, the axially much longer cone-shaped portion of the array of the 
bars is not braced further up to the body of the stator or core, 
respectively. The result thereof is a only limited rigidity of the stator 
end-winding system in spite of the massive inside ring. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a stator end-winding 
system of the kind mentioned above which is less prone to vibrations or 
oscillations, respectively, i.e. to design it more rigid. 
A further object is to provide a stator end-winding system in which the 
inside-ring is braced axially into the array of bars which expands in the 
shape of a hollow cone. 
A further object is to provide a rigid interconnection inside ring/outside 
support elements by bracing the inside ring wedge-like axially in the 
hollow cone described by the bars. Accordingly, on as high as possible 
rigidity of the stator end-winding system shall be arrived at in order to 
raise the resonance frequencies of this system above exciting frequencies 
occuring during the operation of the electrical machine at base 
frequencies of 50 or 60 Hz usually predominantly at their first harmonic 
frequencies, namely 100 and 120 Hz., respectively. 
Still a further object is to provide a stator end-winding system which is 
easy to disassemble and to assemble without having to remove the bars of 
the winding in that an outer support system is provided which includes at 
least one segmented ring or supporting bars extending substantially in the 
aximuthal direction. 
Yet a further object is to provide a stator end-winding in which an outer 
support system includes an outside ring system in the region of the outer 
side of the array of bars which converges cone-like inwards such as to 
arrive at a bracing of the array of bars along the plane of the cone 
formed by the bars over a large surface or plane respectively by means of 
which the rigidity of the stator end-winding system is increased 
considerably, and in which the outer ring system is, furthermore, 
azimuthally and/or radially tensionable such that it nevertheless can be 
slid in its entirety over the end area of the array of bars having the 
largest diameter without disassembling the stator-end winding or 
disassembled therefrom and thereafter be fixedly braced at an area of the 
reduced cone diameter, by a radial pull and/or azimuthal tensioning. 
A further object is to provide a stator end-winding wherein the inside ring 
acts upon the array of bars in a wedge-like fashion and is axially braced 
by tie-rods extending oblique-angled inclined and axially inwards relative 
to its cone surface such that the axially acting tension also excerted by 
the tie-rods will brace the inside ring axially against the stator body. 
The wedge action shall be, thereby, adjustable by an increase or decrease, 
respectively of the tension of the tie-rods and accordingly the rigidity 
of the stator end-winding system. 
Yet a further object is to provide a stator end-winding comprising an 
outside-ring system which acts via a conical tension surface arrangement 
upon the outer side of the cone-shaped array of bars and acts in a 
wedge-like fashion upon the array of bars by means of tie-rods inclined 
axially oblique-angled and outwards relative to the tension surface, such 
that the wedge principle at the cone-shaped array of bars is consequently 
made use of for the outer ring system in that it acts via a conical 
bracing surface system upon the outer side of the conical array of bars 
and acts wedge-like upon the array of bars by tie-rods which are axially 
inclined outwards relative to the above-mentioned surface. 
A further object is to provide a stator end-winding system which is 
optimally rigid by means of two wedge arrangements, namely an inside wedge 
formed by an inside ring and an outside wedge formed by an outside ring 
system which wedges are braced (i.e., urged) by means of the tie rods 
against each other. 
Yet a further object is to provide a stator end-winding system in which the 
inner ring is held substantially only by means of tie-rods, apart from an 
axial locking relative to the winding such as e.g. achieved by means of a 
cord. Bearing in mind that either an outer support or the inside ring 
system is to be axially anchored at the body of the stator it becomes 
obvious that due to the accessability this must be realized at the outside 
ring support and thus the inside ring is mounted such as set forth above. 
Still a further object is to provide a stator-end winding system including 
an outer support system which has at least one tensionable outside ring 
which is substantially held only by means of tie-rods such that the 
tensioning of the outer ring system can be made independently from the 
axial anchoring of the outer ring system. 
Yet a further object is to provide a stator end-winding system which 
comprises an outer support system which includes at least one outside ring 
having two, or preferably three or more azimuthally and/or radially 
braceable ring segments which may be detached from each other, such that 
the outside ring can be placed in form of segments which are separated 
from each other over the outer cone of the array of bars and thereafter 
the segments can be connected to each other and finally be azimuthally 
tightened around the stator bar cone. Alternatively thereto, the segments 
may be tightened only radially inwards. The tightening of the segments 
proceeds preferably by an azimuthal screwing and/or by radial anchors. 
A further object is to provide a stator end-winding system including a 
support in form of a hollow cone having substantially an axial extent 
corresponding to the axial extent of the cone-shaped array of bars, via 
which outer support system as the outer ring system rests on the outer 
surface of cone-shaped array of bars, such that a uniform bracing of the 
array of bars is produced over large areas of the cone surface: The 
support distributes the forces e.g. generated by the tie-rods uniformly 
over the above-mentioned cone surface. It is thereby preferred to insert 
one or more preferably padded rings between the support and the bars of 
the winding located adjacent of same. 
Still a further object is to provide a stator end-winding system in which 
an outer ring system is anchored preferably via rigid connectors and/or 
connectors having spring members and/or guide members to the body of the 
stator such that either within the scope of the elasticity of the material 
of the rigid connectors which are designed accordingly or within the scope 
of the spring action of the spring members or slidable, an axial, 
thermally caused shifting between the bars and the body of the stator is 
made possible without producing stresses thereon which are too high. 
Yet a further object is to provide a stator end-winding system in which the 
bars, the inside ring, and an outer support of the stator end-winding 
system are at least partially mutually cast in and/or padded and/or 
provided with cords and braced together. 
A further object is to provide a stator end-winding system having a basic 
design which allows an easy disassembling of the end-winding system in 
order to be mounted upon maintenance and repair work at known existing 
stator end-windings having an array of bars which expand at the end areas 
coaxially to the axis of the machine outwards. 
Thus, a further object is to thereto provide a retrofitting set for such a 
stator end-winding system which includes an axially braceable inside-ring 
having a conical outer surface and corresponding to at least a substantial 
portion of the inner cone formed by the above-mentioned array of bars. 
A further object is to provide for such retrofitting set an at the outside 
conical and axially braceable ring and possibly an azimuthally and/or 
radially braceable outer support to allow a repair of a stator end-winding 
system rapidly and without long down-times, with further help of further 
known structural members such as tie-rods, intermediate bracing rings, 
material for a casting-in, for padding and applying of cords, etc. 
Still a further object is to provide a method of retrofitting a stator 
end-winding system of a known or of the inventive design wherein the 
originally forseen existing support system for the bars of the stator is 
at least partially removed, at least one inside ring which has a 
conical-shaped outer surface corresponding to at least a substantial 
portion of the inner cone of the array of bars is inserted into the array 
of bars and braced axially. Preferably, furthermore, an azimuthally and/or 
radially tensionable outer support system is placed over the outer surface 
of the array of bars and is further preferably braced via tie-rods to the 
inside ring and in itself azimuthally and/or radially. 
A further object is to provide a retro-fitting method according to which 
rigid connectors and/or connectors with spring members or slidable 
connectors for an outer support system, preferably an outer ring system 
are mounted to the stator body which latter allows an axial displacement 
between the stator body and the outer support system, may such be within 
the scope of the elasticity of the material, of the rigid connectors or 
within the scope of the spring properties or then slidable. 
A further object is to provide a method wherein an outer support system is 
provided which is mounted in a padded fashion to the array of bars and 
where preferably the interstices between forseen upper and lower bars are 
at least partly padded and the bars are preferably additionally supported 
by filler materials and or cords. 
Still a further object is to provide a method wherein pads and/or a filler 
material are built in at the stator-end winding and are impregnated with 
resin prior to the bracing of at least the inside ring and wherein 
preferably an outer support system preferably in the form of an outer ring 
system and secured by cords is provided. 
Yet a further object is to provide a method wherein prior to the 
retro-fitting and preferably also thereafter the state of the stator 
end-winding system is controlled regarding its resonance behaviour by 
means of a modal analysis and its resonance behaviour is adjusted by a 
further tensioning or a change of the tension.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The portion of a stator illustrated in FIG. 1, for instance a stator of a 
turbo-generator includes, according to known designs, a stator core 1 
bolted by through bolts 3 extending coaxially to the merely schematically 
designed machine axis A. The outer bars 5 of the winding and the inner 
bars 7, respectively thereof are located in the core 1 of the stator. 
These bars project at the front ends out of stator body 1 and are bent 
outwards in radial planes extending through the machine axis A such that 
they form in their entirety an array of bars having the form of a hollow 
cone around the machine axis A. According to the present invention now an 
inside ring 9 is provided which includes a cylindrical inner surface 11 
and a conical outer surface 12. The outer cone surface 12 describes 
relative to the machine axis A at least approximately the same cone angle 
which the inner bars 7 describe relative to the above-mentioned axis A, 
and possibly a somewhat larger angle. The cone surface 12 of the inside 
ring 9 includes preferably no radial recesses or projections except 
possibly a grooving or similar means for holding a filler material 
wherewith the inside ring 9 can be slidingly inserted in a wedge-like 
manner into the open cone-shaped region as formed by the inner bars 7 and 
be axially braced therein. The inside ring 9 is preferably made of an 
electrically non-conductive or at least poorly conductive material such as 
a glass-fibre reinforced plastic material. Further, the inside ring may be 
formed as one piece or may be composed of a plurality of assembled pieces. 
The illustration in broken lines in FIG. 1 indicates that possibly a 
ventilator V may be arranged on the shaft of the rotor R in the general 
area of the stator end-winding; in such case the end portion of the inside 
ring 9 may be designed as having a gas guiding arrangement 9, for the flow 
of the cooling gas, such as e.g. the outer casing of the ventilator. 
Bracket plates 15 located outside of the cone-shaped surface described by 
the bars as illustrated in FIG. 1 are anchored by means of screw bolts at 
the body 1 of the stator via angle members 13. The bracket plates 15 
themselves are bolted to the angle members 13 by means of screw bolts 19. 
The bracket plates 15 cover one or more bars 5, 7 of the winding seen in 
axial and azimuthal direction and describe, relative to the outer bars 5 
by means of their inner surfaces 21 a cone-shaped surface which extends 
substantially parallel to the cone-shaped surface described by the outer 
bars 5. The aperture angle of the surfaces 21 is possibly smaller than the 
aperture angle of the cone described by the outer bars 5. An outside ring 
25 which in the assembled state is a continuous embracing ring rides on 
the radially outer supporting surfaces 23 of the bracket plates 15. 
According to the schematic illustration in FIG. 2a the outer ring 25 can be 
tensioned in the azimuthal direction and according to a simple embodiment 
in accordance with said FIG. 2a it consists of at least two, and 
preferably three or more segments of a circular ring 25a, 25b etc. which 
are interconnected via the bracket plates 15 forming a portion of the 
outer ring system by means of connectors 27 and azimuthally acting 
tightening screw bolts 28 designed in FIG. 2a and are braced azimuthally. 
In certain cases the outer support system having the azimuthally braceable 
outside ring 25 may be replaced by an outer support system of a plurality 
of bracing bars resting at both sides e.g. on or between bracket plates 15 
which bracing bars are individually braced radially by tie rods 29 or it 
is possible to forsee a ring of such individual elements 25 which are 
radially braced by tie rods 29 in accordance with FIG. 2b. In such case 
the segments 25c must not form an encircling ring, such as illustrated by 
broken lines. The segments as shown at 25d may also rest on top of plates 
15 and be axially staggered. 
It shall be noted here distinctly that the end-winding can be structured in 
accordance with the invention and depending from the demands of the 
machine such as follows: 
Inside ring with tie rods and azimuthally braceable outer ring. Basic 
variant. 
Inside ring without tie rods, only with azimuthally braceable outer ring. 
Inside ring with outside ring of lateral bars which can not be braced 
azimuthally. Lateral bars and inside ring are braced by tie rods. 
Only inside ring which is pressed in and is locked with axial prestressing 
without outside ring 25 and without tie rods. 
In each variant the inside ring is locked relative to the windings. 
The inside ring can be made of a homogeneous piece or be assembled of 
pieces which are glued and/or bolted together. 
In the case of smaller generators the long inside ring may be replaced by 
two smaller rings which are not connected together. 
According to the basic variant illustrated in FIG. 1 the tie rods 29 are 
forseen between the bars 5 and 7 of the outer winding and of the inner 
winding which are braced by means of tightening nuts at the one hand at 
the outer ring 25 and at the other hand at the inside ring 9. The 
tightening nuts may thereby be preferably sunk into the inside and/or 
outside ring. 
In relation to the vertical direction onto the coaxial and substantially 
parallel and each other facing planes at the one hand of the inside ring 
and at the other hand described by the inner bars 7, the tie rods 29 are 
inclined towards the body 1 of the stator such as illustrated by .alpha., 
such that the tie rods 29 exert a wedging pulling action upon the inside 
ring 9. In certain embodiments the angle .alpha. is selected such that 
also the axis of the tie rods 29 are inclined in relation to the coaxial 
cone surfaces facing each other, at the one hand described by the bracket 
plates 15, at the other hand by the outer bars 5 out of the vertical 
direction and away from the stator core 1 wherewith the outside ring 25 
and the bracket plates 15 are tensioned towards the outside in a wedge 
like fashion. The axial bracing force of the inner ring 9 towards the 
inside is marked in FIG. 1 schematically by K.sub.9 and the bracing force 
of the bracket plates 15 towards the outside by K.sub.15. 
In accordance with the illustration the bracket plates 15 transmit the 
forces produced by the tie rods 29 preferably via two or more rings 31, 
filler and/or padding material 40 uniformly onto the outer bars 5, the 
latter via one or more rings 33 onto the inner bars 7 which abut the 
inside ring 9 along practically their entire length bent outwards. 
Paddings 35 and filler pieces 40 are forseen between the bracket plates 
15, the encircling rings 31 and the outer bars 5 of the winding, and also 
between the ring 33 and the inner and outer bars 5 and 7, respectively. A 
further padding 37 is forseen between the conical outer surface 12 of the 
inside ring 9 and the inner bars 7. A padded insert 39 is located between 
the inner and the outer bars 5 and 7, respectively. 
The bracket plates 15, the tie rods 29 with the tightening nuts consist 
preferably of an electrically non-conducting material or, specifically 
latter of insulated, electrically poorly conducting steel. 
When performing maintenance or repair of the stator end-winding system with 
a stator body 1 and cone-like outwardly bent bars of the winding analogous 
to the illustration of FIG. 1 the actual state of the original winding is 
analyzed by a modal analysis with regard to the resonance behaviour. 
Thereafter the original means forseen for anchoring the bars at the stator 
end winding system are completely or partially removed. If necessary, new 
or modified connecting members 13 are mounted onto the body 1 of the 
stator, if necessary the bracket plates 15 are replaced or then the 
originally forseen connectors and/or bracket plates are used again. Prior 
to this the rings 31, 33 were equipped with the corresponding padding. 
Thereafter, the segmented outside ring 25 is assembled over the bracket 
plates 15, the filling inserts 39 padded, placed as an intermediate layer 
between the outer and inner bars are 5, 7 and these bars then supported 
further by filling material and cords. 
Thereafter, the inside ring 9 inclusive of the padding 37 is inserted and 
the tie-rods 29 are mounted. Then, all paddings, padding 37 inclusive or 
exclusive, are impregnated with a setting resin which is allowed to set 
and thereafter the end-winding is tensioned or braced, respectively by 
means of the tie rods 29 and the azimuthal tightening screw bolts 28 at 
the outside ring 25. Finally, the outside ring 25 and the inside ring 9 
are locked by means of not illustrated cords or filling pieces placed 
against the winding and the resonance behaviour of the stator is checked 
by means of a control modal-analysis and if necessary changed by an 
adjusting of the tension or a further tightening or bracing, respectively. 
Due to the fact that the inside ring can be braced axially by means of the 
tie rods and specifically to the large surface contact acting upon the 
outside and inside ring systems, an extraordinary stiff and rigid 
structure having resonance frequencies which are substantially above the 
possible exciting frequencies occuring during normal operation is arrived 
at in spite of the fact that the disclosed stator end-winding system can 
be easily disassembled. 
In FIG. 1 a preferred embodiment of the connectors 13 is illustrated. FIG. 
3 illustrates a section through one connector thereof. The connector 13 
includes an upper laterally extending anchor beam 41 which, when mounted, 
extends azimuthally and is bolted to the stator body 1 and which acts in 
the axial direction as a leaf spring. A connecting plate 43 arranged to 
form a T with upper beam 41 visible in FIG. 1, connects the lateral beam 
41 to a lower anchor plate 45 having the shape substantially of a "U", 
which latter, according to FIG. 1, is bolted to a bracket plate 15. The 
plate 43 can be provided with a recess 47 (see also FIG. 1) 
According to a further variation of the embodiments it is also possible to 
forsee existing supporting angles as connector 13 which are mounted to the 
body 1 of the stator via pressure springs such that additionally or alone, 
due to the action of the pressure springs the necessary axial moveability 
between the braced array of the bars of the winding and the body 1 of the 
stator is allowed. 
A simple possibility for an absorbing of a thermally caused expansion of 
the bars relative to the stator body 1 is to support the screw bolts 19 
(FIG. 1) in the corresponding bores in the connector and/or in the bracket 
plates 15 in rubber elastic sleeves which absorb resiliently the mentioned 
axial displacements and at the same time guide the bracket plates 15 
azimuthally in the U-shaped plates 45 as longitudinal guides, azimuthally 
stiff. 
The bracket plates 15 can also be supported freely slidable in the U-shaped 
plates 45 acting as guides; in such cases the screw bolts 19 are not 
present. Further in this case the plates 15 may be advantageously shaped 
with outer surfaces 23 parallel to axis A. 
This means that then the sliding lower surface of plate 45 of connector 13 
is parallel to the axis A. Therefore, both, connectors 13 and bracket 
plates 15 have to be replaced. The new connectors, with such parallel 
surfaces, can be mounted to the core 1 as the replaced ones. The new 
connectors 13 may be made of non-magnetic material, especially of 
stainless steel or of fibre glass or of a combination of both. 
FIG. 4 illustrates a portion of a further embodiment of the inventive 
stator end-winding system, namely without an outer ring and without 
tie-rods. In this embodiment a modified angular member 13a is mounted via 
screw bolts to the stator body 1 which is not illustrated in detail. A 
bracket plate 15 is allocated to every angular member 13a which includes a 
transmitter member 15a. A bracing system 14 is forseen in the angular 
member 13a which may be a spring system or as illustrated a wedge system 
which braces the bracket plate 15 against the bars 5. This illustrated 
bracing device absorbs axial changes of the dimensions of the stator 
without loss of its effectiveness. The illustrated embodiment includes two 
wedges 16a, 16b which are driven by tensioning bolt 16c in opposite 
directions and brace (i.e., urge) the bracket plate 15 radially inwards. 
The illustration of a stator end-winding system in FIG. 5 discloses how the 
inside ring 9 can be axially braced in the shown direction and be arrested 
without connection to an outside supporting system such as formed by the 
outside rings or bracing bars. The inside ring 9 is thereby axially braced 
towards the inside by the cord system 10 which is rigidly arranged at the 
bars 5, 7 and/or safety pins 10a are inserted in slide bars 9a which pins 
10a claw into the bars. After the inside ring 9 has been pressed into the 
end-winding in the indicated direction the inside ring 9 is possibly glued 
to the slide bars 9a. 
Preferably, the two embodiments according to FIGS. 4 and 5 may be combined. 
For the axial bracing of the inside ring 9 it is possible to forsee wedge 
and/or spring systems acting axially onto the inside ring instead of the 
measures of FIG. 5. 
While there are shown and described present preferred embodiments of the 
invention, it is to be distinctly understood that the invention is not 
limited thereto, but may be otherwise variously embodied and practiced 
within the scope of the following claims.