Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~047091 ~; ~
The invention concerns components of the supporting --
structure of electrical machines such as generators or motors
which are at least of approximately rotationally symmetrical form ~ ~
and consist of at least two rings arranged concentrically to each --
other by way of a number of spoke-like connecting elements.
Supporting structure components of this kind are known ~- ~
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predominantly in conjunction with slow-running, large diameter,
electrical machines of vertical construction (Swiss patent No.
440, 435, published on December 29, 1967, invented by M~cke and
issued to Siemens-Schuckertwerke ~ktiengesellschaft), their
purpose being to transmit forces of whatever nature directly to
the foundation. The outer concentric ring is usually the generator
pit, built as a concrete ring, and the inner ring is formed by the
bearing housing surrounding the machine bearing, this housing
being also the central body for the bearing support. The latter ~
comprises a number of spoke-like connecting elements which in ;
a known arrangement extend radially, Particularly in the case of
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machines of large dimensions this gives rise to problems which
are difficult to solve, as described in the following example.
Consider an arrangement of the guide bearing according ;
to Fig. 1 of the accompanying drawings to be described below, with
the following date and dimensions:
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Outside diameter of bearing housing: 4 m `:
Diameter of concrete pit: 16 m
Number OI radial arms in bearing support: 12
Nature of arms: beams IPB 1000
A change in temperature o:f only 10C acting on the
arms gives rise to a compressive load of about 100 t per arm,
which means that forces of 12 x 100 t act radially outwards around ~
the circur~erence of the concrete, creating in it tangential tensile . ~ :
stresses which are harmful to the concrete. These same forces
naturally also press on the bearing housing, seriously endangering
the already small bearing clearance of about 0. 3 mm.
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Wlth the known ~olution~, the relative expansion o~ the compon-
ent~ i~ achieved either by making the connecting element~ resilient ln
~` the radial direction or by allowing them to move radially. I~ the
resilience i~ increa~d the central ~haft guide i5 inadequate, while
with radial freedom of movement the very connecting element which is
not anchored, for example when using radial keyways, is the one posi-
tioned at right angles to the direction of the appl~ed ~orce, and
hence sub~ected to the greatest load. Moreover, the known solutions
are very costly.
j~ The obJect of the invention is to avoia the disadvantages
stated above and devise a rigid con~truction which can transmit axial,
radial and tangential forces, allows concentric expan~ion of the rings
in the event of both ~ymmetrical and asymmetrical loads, and is sub-
~ect to only small expansion forces.
This ob~ect is achieved in that the connecting elements are
tangents to the surface of an imagined coaxial cyllnder the diameter
of which is smaller than that of the inner ring, that the axes of two
neighbouring connecting element~ when imagined as extended in a straight
line over both rings intersect only within the inner ring, and that
3 the connecting elements are inflexible over their whole effective
length in the longitudinal direction corresponding to the applied load. ;
The advantage of the invention lles partlcularly in the fact
that all components are completely ~ree to expand concentrically wi~h- -
out the use of resilient radial elements, such as ~prings for example.
~his allows simpler and les~ expensive construction~
If the connecting elements are fixed to at least one of the
r$ngs by means of hinged ~oint~, the thermal expansion forces exerted
; on the rings by the connecting elements are almost completely elim-
inated, and so the ring can be of lighter construction. In additionJ
a hinged form of attachment has important advantages over a rigid
fixing as regards a3sembling and dismaAtling the components.
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It is of advantage if the anchoring points of
at least one of the rings are joined with tie bars for purposes
of stiffeningO If these bars are adjustable in length, any
desired pre-stress can easily be exerted on the rings. This
construction, which thus behaves as a truss, is extremely stiff
and light.
In the case of machines of large dimensions it is
recommended that the connecting elements should be divided into
a number of sections, pairs of these ~rought together at
junctionspoints, and the latter linked to each other by cross-
braces. As this xeduces the unsupported length of the connecting
elements, these can be made considexably lighter. At least the
load-bearing cross-section of the various sections can be matched ~;
to the respective loading.
A further aspect of the invention is an arrangement
whereby the connecting elements extend outwards from the inner
ring in a spiral shapeO This can facilitate erection in particular
In a further aspect of the pxesent invention there is
provided components of the bearing support structure of
electrical machines which are at least of approximately
rotationally symmetrical form and consist of at least tw~ rings
arranged concentrically to each other by way of a number of spoke-
like connecting elements, in which the connecting elements are
tangents to the surface of an imagined coaxial cylinder, the
diameter of which is smaller than that of the inner ring, the
axes of two neighboring connecting elements when imagined as
extended in a straight line over both rings intersect only within
the inner ring, and the connecting elements are inflexible over ~;
their whole effective length in the longitudinal direction corres-
ponding to the applied load.
me invention is explained in the following by means of
examples with reference to the drawings, in which~
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Fig. 1 shows part of an axial section through an -
electrical machine of vertical construction
and through its surrounding concrete shell,
Fig. 2 is a partial section of the arrangement shown
in Fig. 1 along the line A-A,
Fig. 3 is a partial axial section through the
supporting structure of a free-standing machine,
Fig. 4 shows schematically a partial section through the
arrangement of Fig, 3 along the line B-B, ~
10FigO 5 shows schematically a mDdification of the ~ ;-
arrangement of Fig~ 4.
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FigO 6 is a partial section of the arrangement shown ~ -
' in FigO l along the line C-C, and
Fig. 7 is a schematic representation of the components to
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lllustrate the princlple of the invention.
Identical components are provid~d with the ~ame reference
symbols in all the figures.
According to Fig. 1 the outer ring 1 of' the considered compon-
ents i9 a concrete rlng arranged on a concrete foundation 20, the ring
serving to support the electrlcal machine comprising es~entially the
rotor 2 rotatable about a vertical axis and stator 3, and also its
guide bearing and thrust bearing, which are not described ln ~urther
detail.
The guide bearing, the purpose o~ which ln the example shown is
solely to gulde the rotor shaft 4 in the radial direction~ is support-
ed by way of a guide splder consisting sf a central body and beam arms,
the central body comprising the inner ring 5~ and the arms the connect-
ing elements 6. Tie bars 7 ~oin the anchorage points of the arms to
the concrete ring 1.
The thrust-bearing spider consists of the central body, contain-
ing the thrust bearing (not shown), and a number of r~dial arm~ in the
~orm of sectional beams or box beams which ~upport and align the cen-
tral body. Within the term~ o~ the invention the polygonal thrust-
bearing spider ls inner ring 5'. At the ends of the arms the verti-
cal ~orces from the thru~t bearing are transmitted direct to ~he
foundation 20 through the bearing surface 18, which is only indi¢ated.
Tie bars 7' ~oin the raæial arms at their ends, which form the anchor-
age points for the beams comprlslng connecting element3 6'. The lat-
ter transmit the forces, whether they be thermal expan~ion ~orces,
forces due to rotor imbalance or forces caused by magnetic pull/ to
the concrete ~oundatlon 20. Both the connecting elements 6 from the - -~
`guide bearing and the connecting element~ 6' ~rom the thrust bearing ~-
¢omprise components whlch are rigid and lnflexible in the longitudinal
direction in accordance with ~orces actlng on them.
Fig. 2 shows a cross-section through thé arrangement of Fig. 1
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a7~91
at llne A-A. The connecting elements 6 are tangent~ to the aurface
of a coaxial cylinder 8 withln the ring 5 and indicated by a chain-
dotted line. The hlnged attachment of the arm~ to the central body
'ls indicated schematlcally. The arms are located in an annular re- -
; cess l9 (Fig. l) in concrete ring l and can be fixed in any manner
deslred. A defined tangential compressive load can be exerted on the
concrete ring by mean~ of the adJustable tie bars 7 which are fixed to
the outer anchorage points of connectlng elements 6. These tie bars 7
can be round bars with left and right-hand thread~ at the end~, for
~ example, with which a pre-stress can be applled to the outer rlng l
i whlch perslsts under all operating conditions.
Fig. 3 shows an ar~angement which is of advantage with machines
of very large dimensions. This is a free-standing machine which has
no concrete ~lng or concrete pit. The bearing spider and the stator 3
are supported on a truss construction wh~ch ~orms the outer ring l'. ;~
With constructions o~ this kind there is no need for the otherwise
customary lightweight steel machine housing, which is replaced by a
steel enclosure mounted direct on the frame, giving it the necessary
if~ne~s and the present example consisting of the tie bars 7". The '!
lnner ring 5" is composed of the central body comprising a steel rein-
forced-concrete structure, and the connecting elemen~s 6';' are frame
girders.
. Fig. 4 shows a partial cros~-section of the arranBement in
Fig. 3 at the line B-B. To reduce the unsupported length, the conn- ~ ;
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~ ecting elements 6" are divided into several sections 9 and ~oined to-
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gether at ~unction points lO. The latter are Joined to each other by
cross-brace~ ll. The central body of the guide spider can be of con-
~,~' crete to increase it~ dynamic stiffness or, as shown, the ~paces be-
tween the radial elements 12 and tran~ver~e elements 13, which form
closed boxes~ can be ~ d with concrete, whereupon this as~embly
- forms the ring 5". In this way the bearing support can be assumed ~ -~
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1~347091
to be completely rigld, even with machine~ of very large dimensionss.
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Fig. 5 sshows an alternative from the arrangement in Fig~ 4.
The connecting ele5nents 6', agaln divided lnto sections 9, are arrang-
ed in spiral form. The central body in this case is no longer assumed
to be rigid. It is then possible to make the connecting elements 6"
leave the inner rlng 5" eccentrically, still in accordance with the
aspects of the inventionJ but they are approximately radial, which
~! can make erection easier.
Fig. 6 shows a further example of the inventionJ being a cross-
~3 section at line C-C o~ the arrangement ln Fig. 1. The central body
of the thrust-bearing spider is provided with eight arms, the spider
as a whole~forming the rlng 5'. Ring 1 corresponds to the concrete
foundation. The connectlng elements 6~, in accordance with the in-
vention, are spokes in the form of profiled or box beams which ab one
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and are anchored to I-beam columns 14 cast in the concrete ring, while
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at the other end the arms are fixed by bolting, welding or hinged
oints. A hinged ~oint 15 at the ends of the arms is indicated in
;~ the present example. The tie rods 7~ are round bars of adJustable
-- length, their purpose being to stif~en and pre-stress the structure.
~,0 The principle o~ the invention can be described wlth re~erence
~; to the diagram o~ Fig. 7. The two concentr~c rings and the connecting
- elements are identlfled by the same reference symbols as the corre-
sponding parts in Fig. 1 to 5. The conne¢ting elements 6 are tan-
gents to the chaln-dotted cylinder 8, Starting from the centre 1~
of the system, RI is the radius o~ ring 5, RA that of ring 1, and the
two radii form the angle ~ . C denotes the angle contained be-
tween RA and the considered connécting element 6, which has a length
-~ of L. For simplicity the angle ~ is introduced; this ls the arith-
. ~
i metic sum of c~ and ~ .
Let one flrst consider symmetrical expansion ~ L of connect-
ing elements 6, due to heat ~or example. This elongation is converted
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into a relative rotation o~ the two rings 1, 5, whlch is most conven-
iently expressed as a change in angle
L
RI sin
According to the ob~ect of the invention, expan~ion o~ the rings -
ls required to be free and concentric under all load conditions. The
~ollowing generally valld relationship can be written ~or both sepa-
rate and combined changes of L, RI and RA~
. ~.
l~L ~RI RA . COB OC
RI sin ~ Rl . tan ~ RI . Bin ~ ~ ;
This relation~hip i8 valid when the ~ixings at both end3 of the conn-
iO ecting elements 6 are hinged.
The forces acting at right angles to the machine axi~ are re~
301ved into components which act in the direction of the axes of the
connecting elements. A3 with a ~rame 3tructure, the connecting ele~
ments are ætressed only in tension or compression and consequently th~
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assembly has great ~ti~fness.
When the a~sembly i~ loaaed symmetrically the ring-shaped parts
remain concentric, both on expan~ion and contraction. With asymmetri~
cal loading, ~or example heating o~ the connecting element~ 6 on one
~ide, the centrs o~ the a~embly could move eccentrically. This can ;~
be remedied by v~rious mean~ o~ adaptation, for instance by dimension-
ing the cross-sections ln accordance with the ~orces which occur, by
a suitable choice o~ material~, or in the case of individual connect-
ing element~ 6 by altering the angle~ c~ and ~ with appropriate
modi~ication of length ~.
If the arrange~ent o~ ~ig. 2, considered a~ representing the
pre~ent state o~ the technology, i~ con~tructed in accordance with the
lnvention, but with the conne¢ting elements 6 rigidly fixed at both
ends, and the cylinder 8 has a diameter of 3 m, the compressive load-
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ing of 100 t/bar exerted on the originally radlal connectln~ elements
can be reduced to 1 t/bar. If the anchorage points on one of the two
rlngæ~ in Fig. 2 on the bearing hou~ing ~or example, are provided with
hinged Joints, which by their nature do not transmit bending forces,
none o~ the forces caused by the connecting elements are transferred
to the rlngs.
If the connecting elements are rigidly ~ixed to the anchorage
points they undergo slight bending owing to the relative ro~ation o~
the rings. The change of angle ~ ~ i3 somewhat smaller than with a
hinged arrangement. Since the connecting elements are pre~erably of
shaped pro~lle with a relatively high moment of inertia, the ends can
be solid, but mu~t have a moment of inertia as ~mall as possible about
the bending axis. In this way, bending can be localized to the ends
o~ the connecting element~. A particularly easy way o~ making these
ends easily bendable is to use hollow sections ~or the connecting
elements 6. Over their e~ective load-bearing length these have a
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cross-section with a relatively high moment of inertia, at the anchor-
age points the cross-section is pressed to a ~lat shape. The load-
bearing cro~s-section then remains the ~ame, while the moment o~ in-
ertia about the be~ding a~i~ is sharply reduced. ~ -
The invention is of course not restricted to what i3 shown in
the drawings. The rings o~ the invent~on can be Or polygonal or cir-
cular ~orm, provided the anchorage polnts o~ each ring lie on a circle.
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