Note: Descriptions are shown in the official language in which they were submitted.
- : ~z~
- 120/84
19.12 .84
Se/eh
~ Manufacture
The present invention concerns a coil in accord-
ance uith the preamble to Claim 1 and a method of manu-
facturing it.
An axially preloaded coil arrangement for trans-
formers and chokes, in which elastic loops wound frominsulating strips are used for the transmission of the
axial preloading forces from one end to the other of the
coil arrangement, is 3lready kno~n from the US Patent
3,321,567, Figure 1. These loops have, at each end, an
elastic eye used for fastening. These eyes are con-
pressed and each of them pushed through a hole in an end
retaining flange of the coil arrangement, in such a way
that a fastening bolt can be pushed through the eye on
the side of the retaining flange facing away from the
coil arrangement. The coil arrangement is subjected to
pressure by means of compress;on screws fitted in threade
holes of one retaining flange, ~hich act on the end sur-
face of the coil arrangement via intermediate compression
layers. The reacton forces resulting from this are
directly transmitted to the loops squashed between the
edge of the hole and the fastening bolt.
These loops are, in consequence, subjected to
shear at some locations, which has the disadvant3ge that
in this way local overloads and, in consequence, mechan-
ical damage eo the loops can occur. The preload;ng forceacting on the coil arrangement can only be determined
indirec~ly by means of the torque applied for turning the
compression scre~s. This method invoLves uncertainty so
that corresponding safety factors have to be allowed for,
leading to a more expensive construction of the coil
arrangement.
The invention is intended to provide a remedy on
these points. The invention, as characterised in the
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35;~38
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claims~ achieves the objective of producing a coil in
which the maintenance of an accurately defined axial
preload is possible by simple means, and which can be
manufactured by a cost effective method.
The advantages achieved by means of the invention
are mainly to be seen in that a large varie~y of coil
variants can be manufactured using relatively few similar
parts. The various retention variants for the loops can
be combined with one another in such a way that optimum
preloading conditions are achieved for the particular
appLication. Furthermore, the dimensions of the loops
and their retention devices can be kept relatively small
so that the flow of the cooling medium through the wind-
ing is hardly affected and effective coolin~ is, in con-
sequence, ensured. In addition, it is possible to manu-
facture coils of the most widely varying winding shapes
and hence always to select the most favourable structural
form for the particular requirements.
The invention is described in more detail below
ZO by means of drawings illustrating only one embodiment
route4 In the drawings:
Figure 1 shows, in the left-hand part, a section through
a first embodiment form and, in the right hand
part~ a section through a second embodiment
form of the ;nvention,
Figure 2 sho~s a section through a first looP retention
device, shown simplified only in Figure 1,
Figure 3 sho~s a section through a second embodiment
form of the loop retention device,
figure 4 shows, in the left-hand part, a section through
a third embodiment form, and, in the right-hand
part, a section through a fourth embodiment
form of the invention,
Figure S shows a section through a fifth embodiment form
of the invention,
Figure 6 shows an end view of a sixth embodiment form of
the coiL in accordance with the invention,
Figure 7 shows an end view of a coil segment of a
_ 3 ~ 35~
seventh embodiment form of the invention,
Figure 8 shows the s;de vie~, in section, of an
electrical connection of the coiL according to
the invention, and
Figure 9 shows the end view of the electrical connection
according to Figure 8.
In all the figures, parts having the same effect
are indicated by the same reference signs.
Two variants of a coil according to the inventîon
are shown in Figure 1. This coil has a~iaLly shaped
~indings 1 which are axialLy preloaded by means of a
preloading device. The preloading device consists of
retention devices in contact with the end surfaces of the
windings 1 and loops Z ~hich brace these mutually opposite
retention devices against one another. Each of the reten-
tion devices is composed of a support spider 3 with arms 4
and loop retention devices 6a ..~ 6d, 6a' ~.. 6d'
fastened to the arms 4 in axialLy extended longitudinal
holes S. The loop retention devices 6a ... 6d, 6a' ...
6d', not shown in detail, have semi-circular shaped
contact surfaces onto which the loops 2 are pushed. The
loops Z are wound in multiple layers fro~ elastic insulating
strips impregnated ~ith hardening synthetic resin, are
hardened in a definite shape and fit positively onto the
semi-circular shaped contact surfaces of the loop reten-
tion devices 6a ... 6d, 6a' ... 6d'.
Figure Z shows one of the loop retention devices
6a .~. 6d, 6à' ... 6d' in section. The loops 2 are,
generally speaking, held in pairs by each of the loop
retention devices 6a .~. 6d, 6a' ... 6d'. The loops Z
each lie in a groove on a strip holder 7. The strip
holder 7, in conjunct;on with the arm 4 of the support
spider 3, forms the groove of rectangular cross-section,
~hose bottom is, in part, of semi-circular shape. One
flank 8 of this groove ;s a part of the strip holder 7,
the second flank is formed by one side of the arm 4. The
section in Fi~ure 2 is laid preciseLy ~hrough the highest
point of the semi-circular shaped section of the groove.
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~ 4 --
The upper semi-circular section of the groove adjoins two
opposite and parallel straight groove sections o~ t~e
strip holder 7, each flank 8 becoming lower uith increas-
ing distance from the semi-circular shaped section.
Each of the two parallel, straight, mutually opposite
groove sections are located on one leg 7' of the strip
holder 7. The two legs limit a rectangular recess in the
strip holder 7~ the longitudinal flanks of the recess
being extended parallel to the bottom of thè s~raight
sections of the groove. Each of the two legs has on the
bottom end surface a rectan~ular contact surface 12. A
hole 9 for a bolt 10 is provided in the centre of the
semi-circular shaped sect;on of the strip holder 7~ This
bolt 10 connects one strip ho~der 7 with a second on the
other side of the arm 4. The bolt 10 has a one-sided flat
11 in the region within the elongated hole 5. This flat
11 rests on a cuboid shaped distance piece 13, which is
supported on a make-up intermediate layer 17, which rests
on a braçing wedge 14. The bracing ~edge 14 has a contour
on ~he side and on the bottom matched to the elongated
hole S. It is secured by two washers 15 held by the bolt
10 and is guided laterally in the rectangular recess of
the strip holder 7. The arm 4 rests on insulating in-
termediate plates 1S which are supported on the windings
1.
Figure 3 shows, in section, another possible
embod;ment form of the loop retention device 6a O~ 6d,
6a' ... bd'. It differs from that shown in Figure 3 only
in that the bolt 10 has no flat ancd that the strip holder
3G 7 is in direct contact with the make-up intermediate
layer 17, ~hich is supported by the bracing wedge 14.
Two further variants of a coil according to the
invention may be seen in Figure 4. The windings 1 are
axially preloaded by individual preloading devices evenly
distributed around the periphery of the coil The reten-
tion devices of these preloading devices consist of a
radially directed rod 3D which rests on a distance plate 31,
~5~;88
which is supported on an intermediate plate 16. This
intermediate plate 16 rests on the end surfaces of the
windings 1. The mutuaLly opposite retention devices are
connected together by the loops 2. The loops 2 are
pushed onto the preferably round shaped rod 30 so as to
make a positive connection. The rod 30 can also be
designed as a tube or as half-round material.
Figure 5 shows two different retention device
variants comb1ned in a common preloading device. The
upper retention device consists of a support spider 3
with loop holding devices 6a, 6b~ the lo~er retention
device consists of rods 30 directed ean9entially to the
winding, the rods being supported on a distance plate 31
and an intermediate plate 16. ~oth the intermed;ate
plate 16 and the distance plate 31 have cut-outs 29
through which the loops 2 can be fed w;thout contact.
Figure 6 shows a coil which has four-armed
- support spiders 3 each having a loop retention device 6a
... 6d per ar~ with two loops 2 within the coil in each
case. Also shown is a preloading device between two
support arms with a radially directed rod 30 as the
retention device for two loops 2. One or more of these
preLoading devices c-an be additionally mounted in each
coil segment between the support arms. In this way,
coils already delivered can be made suitable for higher
loads as a retrofit measure and at low cost.
Figure 7 shows a coil segment of a multi-layer
coil with two different installation types of preloading
devices with radially directed rods 30 as the retention
devices for the loops 2.
F;gure 8 shows a section through the fastening of
a terminal lug 32 by means of the radially directed rod
30 and two loops 2 pushed on to it~ The connecting lug
32 rests on the distance plate 31 and the insulating
ir,termediate plate 16. The connecting lug is covered
above by an insulating plate 33 on which the rod 30
presses. The part of the connecting lug 32 protruding
towards the inside of the coil can be connected to one
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end of the winding.
Figure 9 gives the end view of the fastening of
the connecting lug according to Figure 8. The loops Z
lead without contact through the cut-outs 34 into the
S fastening.
In order to explain the mode of operation,
Figures 1 and 2 are considered jointly. The Loops 2 are
elastic in the axial direction and this elasticity is
used in order to subject the coil to preload. The loops
Z are specially manufactured for each aoplication; they
are wound on a jig in several layers from an insulating
strip impregnated ~ith hardening synthetic resin and are
hardened in a definite shape. The loops 2 are therefore
only subject to relatively small manufacturing toler-
ances.
As an example, the fitting of a pair of lQOPS be-
tween the loop retention devices 6a and 6a' is now de-
scribed. The lower loop retention device 6a' is com-
pletely assembled, the two loops 2 being pushed onto the
lower strip holder 7 so as to form a positive connection.
During the assembly of the upper loop retention device 6a,
the loops 2 are also pushed onto the upper strip holder 7
so as to form a positive connection. The distance piece 13
is bonded to the flat 11 of the bolt 10 after the assembly
Z5 of the right-hand half of the strip retention device 6a.
There is not, initially, enough space between the distance
piece 13 and the bottom flank of the elongated hole 5 for
the insertion of the bracing wedge 14. Using a press~
wh;ch is supported at one end via the arm 4 and the
intermediate plate 16 on the end surface of the winding
and, at the other end, acts on the contact surface 12 of
the upper strip holder 7, and presses the latter upwards,
the loops 2 are preloaded and therefore extend in the
axial direction~ The preloading force is selec~ed to b-e
somewha~ higher than the required value. The bracing
wedge 14 can now be inserted and, if necessary, make-up
intermediate layers 17 as well. The externally applied
preloading force is reduced, the bracing wedge 14
~2S~S~
-- 7
becomes firmly clamped and the loops 2 undertake the
maintenance of the required value of preloading ~ithout
any shear loading. Only at this point are the bolts 10
of the loop retent;on devices 6a, 6a tightened and
secured.
This application of the preload to the coil is
generally carried out in segments because only relatively
small preloading forces then have to be applied. }n
addition, preloading in segments ensures be~ter accessi-
bility to the assembly positions of the loop retentiondevices 6a ... 6d, 6a ... 6d .
The semi-circular shaped contact surface of the
loops 2 on the strip holder 7 ensures that the loops 2
are evenly loaded in tension ~ithout shear forces
becoming effective. The preloading force which can be
carried per loop 2 can be increased as the number of
layers of the wound, glass-fibre reinforced insulating
strips increases~ It is also possible to increase the
preloading forces by raisiny the number of loops Z
zn fitted. As is sho~n in Figure 1, it is also possible to
place the loops 2 differently and, in fact, to suit each
specific loading case. Instead of the common instal-
lation of the loop retention devices 6a, 6a and 6b, 6b ,
it would - for example - suffice, in the case of lower
Z5 load, to install the loops 2 between the loop re~ention
devices 6b, 6b . Similarly, in the right-hand coil
variant, the outer loop retention device 6d, 6d could be
omitted. A large number of possible installation variants
ensures that an optimum and economical preloading device
can be provided for each application.
The loop retention device shown in Figure 3 is a
somewhat simplified embodiment form of the loop retention
device shown in Figure 2. It can be used advantageously
for relatively lightly preloaded coils, because the
bracing wedge 14 consisting of plastic is loaded in shear
and is therefore less able to carry load.
Figure 4 shows particularly economical coil
~2S~S~!3
variants with individual preloading devices. During
assembly, for example, the lower retention device is
first assembled, the loops 2 being pushed on the rod 30
so as to prov;de a positive connec~ion and the inter-
~ediate plate 16 being inserted between the rod 30 andthe end surface of the winding~ The loops 2 are then
pushed onto the upper rod 30 so as to form a positive
connection. Here again, the application of the preload
takes place by means of a press ~hich is supported, at
one end, on the upper end surface of the windings and,
at the other end~ on the rod 30, pressing the latter
upwards. The preloadin~ force is selected to be somewhat
larger than the required value. The space between the
rod 30 and the end surface of the windings is now provided
~ith the intermediate plate 16 and distance plates 31 in
such a way that, after the reduction of the preLoad pro-
duced externally by the press, the loops 2 are precisely
loaded with ~he req~ired value of preload without being
subjected to any shear Forces. The possibil;ty of making
an optimum selection among the most varied installation
variants for the loops 2 in the case of multi-layer
windings is available here also.
The preloading device variants given in Figures
5, 6 and 7, ~hich can also be combined ~ith one another
and ~ith the other variants, do not by any means show all
the possible arrangements. rhis principle of solidly
connecting parts, particularly retention devic~s for
preloading devices, ~o the coils by means of pre-shaped
loops can also be used to fasten, for example, carrying
eyes or connecting lugs 3Z to coils so that they are
stiff in torsion.
An embodiment example for the fastening of a con-
necting lug 32 may be seen in Figures 8 and 9. During
assembly, the intermediate plate 16, possibly distance
plates 31, the connecting lug 32 and insulating plate 33
are stacked so as to fit on the end surfaces of the
wind;ngs. T~o loops Z, ~hich are pushed onto the stack-
holding rod 3û so as to provide a positive cunnection~
. ~ . . . . .. .
~S35~38
_ 9 _
are fed ~ithout contact through cut-outs 34. In the
region of the opposite end surface, the two loops 2 ar~
pushed onto a further rod 30 and preloaded without shear
force as already described; the connecting lug 32 is then
solidly clamped.
It is also possible to design the intermediate
plates 16 on the winding side in comb shape so that
additional and safe spac;ng of the end ~indings is
achieved ;n the case of highly loaded coils.
The whole of the preloading device is~ generally
speaking, built of non-magnetic material; for particular
applications, it can be manufactured completely from
plastic, in which case the more highly loaded part~ must
have glass-fibre reinforcement.
An embodiment example of the method according to
the invention for manufacturing the coils previously
described is given below. The coil is wound in a known
manner; it is then fixed by temporary strips, impregnated
~ith casting resin and the casting resin subsequently
hardened. After the hardening, the coil is provided with
ehe preloading device. In this process, the loops 2 are
pushed onto the retention devices of the preloading
device so as to provide a positive connection. The loops
2 are subjected to a preloading force somewhat above the
required value by means of a press supported at one end
against the erid surfaces of the co;l and acting, at the
other end~ on the retention devices in such a way that
the loops 2 are preloaded in the axial direction. The
tensioning wedges 14 and the make-up in~ermediate layers
17 are then placed in the retention devices so that the
loops 2, after the reduction of the preloading force
applied externally by the press, are preloaded to the
required figure. The loop retention devices are then
finally tightened up and the temporary strips remo~ed.
The preload;ng of the loops 2 can be advan-
tageously carried out with a relatively small and easily
handled press if the preloading is carried out separately
for each individual retention device~ The coil is
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preloaded in segnents in this manner. A further
advantage of this procedure is that good accessibility to
the loop retention devices 6a ... 6d is continuousLy
ensured, which facilitates the assembly of the tension
wedge 14n
The f;nal preload;ng is at least O.SX of the
loading length of the loops 2 and in the majority of
applications does not exceed 1.2X~
