Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1 15~5
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Regulating winding connected in series with a main winding
of a transformer
Technical Field
. .
This invention relates to a multi-turn regulating
winding arranged in a transformer and provided with a plur~
ality of connecting contacts (e.g. for an on-load tap-
changer) arranged at different potentials, the separateturns of the regulating winding being series-connected with
- each other. Such regulating windings are known from
Swedish Patent No. 389,942 and from published German Patent
Application 2938531.
Discussion of Prior Art
During transient oscillations, high voltages will often
occur across the regulating winding, especially across the
end portions of the regulating winding. It is ~nown that
these overvoltages are dependent on the capacitive coupling
between the different turns of the regulating winding in
such a way that a relatively strong capacitive coupling
gives lower overvoltages than those obtained when there is
a relatively weak capacitive coupling. I~hen designing a
regulating winding,the aim is therefore to obtain as high a
value as possible for the so-called series_capacitance of the
regulating windingg or in other words, the aim is to maxi-
mize the ability of the regulating winding to store capaci-
) ~ tive energy. It is thus known to arrange, for this purpose,
an electrostatic screen radially outside the regulating
winding. Such a screen has a uniform potential equal tothat of its point of connection to the winding. This means
that the electrical insulation between the electrostatic
screen and the regulating winding must be capable of with-
standing the total voltage across the regulating winding,
which sets a limit on the increase in the series capacitance
that may be attained with the aid of an electrostatic
screen, and, since the screen must be spaced a relatively
large distance away from the winding, the use of an elec~ro-
static screen considerably increases the space required for
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the regul~ting winding.
Disclosure of the Invention
According to the invention there is provided a regu-
lating winding arranged in a transformer and provided with
a plurality of connecting contacts, arranged at differer.t
potentials, each connecting contact representing a corres-
ponding regulating step, said winding comprlsing a plurality
of multi-turn, substantially helical current-carrying con-
ductor loops, said current~carrying conductor loops being
electrically insulated from each other and arranged in such
~) a way that each one of said current-carrying conductor loops
has a first end point at the one end of said winding and a
second end point at the other end of said winding, a plural-
ity of electrical connecting elements arranged to connect a
plurality of said first end points to a plurality of said
second end points in such a way that said helical current-
carrying conductor loops are thereby series-connected with
each other, each of said connecting elements belng connected
to a respective one of said connecting contacts, which is
characteri,.ed in that said winding also comprises a plural-
ity of insulated, helical potential loops, each of which is
arranged with at least one surface portion thereof facing
an adjoining surface portion of at least on~ of said current-
carrying conductor loops along at least part of the length
.) 25 thereof, each of said potential loops at one or the other
end of said winding having an end point, which by means
of electrical connecting means, is placed in electrical
connection w;th an end point of a corresponding current-
carrying conductor loop located at the same end of the
winding, whereby each potential loop has a surface portion
confronting an adjacent surface portion belonging to a
current-carrying conductor loop, but not to the current-
carrying conductor loop which is electrically connected tothat potential loop.
Brief Description of Drawings
The invention will now be described, by way of example,
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with refererlce to the accompanying drawingc,in which Figures
1, 2, 3 and 4 show axial sections through the cylinder
wall of four different embodiments of a regulating winding
according to the invention.
Description of ?referred Embodiments
In each embodiment, the regulating winding is a substan-
tially hollow cylindrical body and in ~he interests of clarity,
the cross-sectional surfaces Or the current-carrying conduc-
tor loops of the windings shown in the drawings have not
been provided with the conventional hatching normally used
) to indicate a cross-section~
The regulating winding shown in Figure 1 has been
provided by collecting eight electrically insulated copper
bars 20 of rectangular cross-section and eight electrically
insulated copper bars 21 also of rectangular cross-section
in one bundle, the bars 21 being shown as havi~ng the same
height but smaller width, than the bars 20. rhe bundle of
bars 20, 21 is wound in two full turns so as to form a sub-
stantially hollow cylindrical body with a vertical axis.
The sectional surfaces shown in Figure 1 all lie in the same
axial plane, the sectional surfaces indicated by the arrow A
representing the beginning of the uppermost~turn a the sec-
tional surfaces indicated by the arrow B representing the
transition between the first and the second turn, and the
' 25 sectionai surfaces indicated by the arrow C representing the
end of the second turn.
The conductors 20 thus form eight helical current-
carrying loops and the conductors 21 form eight helical
potential loops. The current-carrying conductor loops, which
are designated by the Roman numbers I-VIII, are series-
connected with each other by means of a plurality of electri-
cal connecting elements shown schematically at 12'-18', and
these elements are each provided with a corresponding conn-
ecting contact 12-18 corresponding to the different regu-
lating steps of the winding. The upper end of the current-
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carr~ing conductor loop I is sho~.~n connected to a connect-
ing contact 11 and to one end poin~ of a main windirg 10
of the transformer, which together with the regulating
winding is wound around a transforrner leg (not shown).
The Roman numbers I-VIII indicate the sequence in which the
corresponding current-carrying conductor loops are series-
connected. The lower end of the current-carrying conductor
loop VIII is connected to a contact 19 which represents
the highest regulating stage in a regulating winding having
the same windi.ng direction as the main winding 10.
In each of the potential loops, the upper end thereof
is held at the same poential as the upper end of some of
the current loops II, IV, V, VII by means of one of a plur-
ality of potential connections 22-29~ In the drawings,
each potential loo~ is provided with a number corresponding
to the Roman number of the current-carr~ing conductor loop
to the upper end of which the upper end of that potential
loop is electrically connected. No potential loop is
directly connected to an i~mediately adjacent current-
carrying conductor ioop~ which means that the potential
difference between any point in a current loop and the
nearest point in an adjacent potential loop is always greater
than zero. With the current loop I, this p~tential differ-
ence during normal operation is equal to the voltage appear-
~ ` 25 ing across the series-connected current loops I, II, III and
) IV, and with the current loop VIII~ the above-mentioned
potential difference is equal to the voltage appearing
across the series-connected current loops IV, V, VI and
VII. Thus with both current loops I and VIII the potential
difference is equal to 50% of the full voltage appearing
across the regulating winding5 With the current loops II
and VII, the potential difference in question is equal to
37.5% of the full voltage appearing across the regulating
winding, the corresponding potential difference for each of
the current loops III, IV, V and VI being 25% of the full
regulating winding voltage.
-- 6 --
In ~igures 2, 3 and 4, reference numerals which are
also used in Figure 1 denote the same items.
The regulating winding sho~ln in Figure 2 - which is
similar to that shown in ~igure 1 - de~ines a substantially
hollow cylindrical body which is formed by winding a con-
ductor bundle two full turns along a helical line. For the
sake of clarity, the winding shown in Figure 2 has also been
drawn with gaps between the turns. The winding has a vertical
longitudinal ax;s and each turn comprises eight substantially
helical current-carrylng conductor loops. These are
arranged with two loops forming a pair in the radial direc-
) tion so that only four potential loops are required~ the
opposite side surfaces of each potential loop facing and
making mechanical contact with a different one of the current
loops in each pair.
As in the e~bodiment shown in Figure 1, the potentialloops are arranged in direct electrical connection with
each other or with a current loop only at the upper end of
the winding. The corresponding potential connections are
designated 31, 32, 33 and 34 in Figure 2.
The potential difference between any ~oint in any of
the current loops I and VIII and the nearest point in an
adjacent potential loop is equal to the voltage across four
) series-connected current loops, thus representing 50%
of the total voltage appearing across the regulating winding.
The corresponding potential di~ferences cf the current
loops II and VII are 37.5~, of the current loops III and
VI 25%, and of the current loops IV and V 12.5~, which
last mentioned potential difference is equal to the voltage
ap~earing across a single current loop.
In the regulating winding shown in Figure 3, the partial
sectional surfaces A, B, C and D lie in an axial plane
through the wall of a substantially hollow cylindrical body,
which again is shown as having a vertical axis but which now
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consists of three turns of a con~ c~or bundlP, each turn
consisting of six insulated copper bars 35 of rectangular,
relatively large cross-section forming the current loops and
twelve insulated copper bars ~6 of the same height as the
bars 35, but of reduced width, the bars 36 forming the volt-
a~e loops. The sectional surface indicated by the arrow A
represents the start of the first turn and the sectional
surface indicated by the arrow D represents the end of the
third turnO ~he winding thus contains six insulated, substan-
tially helical current conductor loops I-VI and twelve
insulated, substantially helical potential loops, the two
) opposite side surfaces of each'current loop being each
arranged in mechanical contact with a different potential
loop along the entire length of the winding. The lnvention
also includes arrangements in which contact between the
current and voltage loops only existsalong part of the length
of at least some o. the current loops. By means of a plural-
ity of potential connections ~indicated by short lines in
Figure 3, but not numbered), the upper ends of the potential
loops and the upper ends of the curren~ loops are connected
together in pairs. In the same way as in Figures 1 and 2,
each of the potential loops in Figure 3 is provided with a
nùmber corres'ponding to the Roman number of the current
loop to which it is connectedO The current loops I-~I are
series-connected to each other by means of a plurality of
connecting elements 12'-16', which are provided with corres-
ponding connecting contacts 12-16 intended for an on-load
tap changer. In all current loops I-VI and at each point
thereof, the potential in relation to the nearest point
of any adjoining potential loop is equal to the voltage
across two series-connected current loops, that is, in nor~al
operation it is equal to 33.3~ of the voltage appearing
across the entire regulating winding.
In the regulating winding shown in Figure 4, the partial
sectional surfaces designated by the arrows A, B and C
lie in an axial'plane through the wall of a substantially
hollow cylindrical body again shown with its axis vertical.
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The ~inding illus~rated in ~igure 4 consists of a substantially
helical bundle of copE)er bars ha~/inæ t--lo t~lrns~ the section-
al surface indica ed by the arrow A l~ing at the start of
the firs~ turn, the sectional surface indicated by the arrow
B representing the tr~nsition between the first and the
second turn, ancl the sec~ional surface indicated by the
arrow C representing the end of the second turn. In Figure
. 4, the bundle contains five insulated copper bars 37 of
.~ rectangular, relatively large cross-section, which form five
equally long helical current loops I-V~ and fifteen insu-
lated copper bars 38 each of smaller rectangular cross-section
than the bars 37, which bars 3~ form fifteen helical poten-
) tial loops. The current loops are series-connected to
each other by means of a plurality of electric connecting
elements 12'-15', each of which is provided with a respective
connecting contact 12-15. The end points of the series-
connected group are connected to contacts 11 and 16 via
connections 11' and 16'. The potential loops are again
provided with numerals corresponding to the Roman numbers
of the current: loops to which the potential loops are
connected at their upper ends.
In the current loop I, the four limiting surfaces of
the bar 37 forming the loop each makes contact with a
corresponding potential loop, with a potential difference
Of respectively one, three, three and three times the volt-
age appearing across the current loop. Expressed in the same
manner, the potential differences of the voltage loops
surrounding the current loop V are three, two, two and two,
the potential differences in the case of the current loop II
30 are two, two, one and one, whereas the potential differences
in the case of the current loop II are two, three, two and
one. The potential differences of the current loop IV in
relation to each of the three adjoining potential loops
at the upper end of the winding are twice the voltage across
a current loop~ At other places in the winding the current
conductor loop IV also makes contact with a potential loop
poSitioned above it and has in relation thereto a potential
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whic~l is equal to the voltage across one current
loop.
In all the embodiments of the invention, each one of a
plurality o~ potential loops has, at one or the other end of
the regulating winding, an end which is arranged in elec-
trical connection with an end, located at the same end of
- the winding, of a current loop which does not make mechanical
contact via any of its side surfaces with the potential
loop.
In the drawings, all the connections between the current
loops and the potential loops have been shown to be located
at the upper end of the winding. It is, of course,
equally possible to use connection points which are only
positioned at the lower end of the winding, or indeed to
arrange some of these connections at the upper end of the
winding and the remainder at the lower end of the winding.
- Although the illustrated embodîments all show the
connections between loop ends positioned at the same end of
the winding, this does not mean that the corresponding
connecting wires have to be positioned at one end or the
other end only of the winding. Thus, for example, the upper
end of a potential loop can be directly connected to the
lower end of a first current loop, so that the upper poten-
) tial loop end is effectively also connected to the upper
end of the second, series-connected current loop which
follows immediately after the first current loop in the
series group.
.
In the embodiments of the invention shown in the draw-
ings, each current loop contains only one conductor. The
invention also includes the case where each current loop
is formed by a conductor which consists of a plurality of
individually insulated and mutually parallel-connected bars
or wire bundles of electrically conducting material.
