Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This invention relates to a tap changing transformer
wherein the voltage developed between the high-voltage
terminals is controlled by changing over the taps of the
tap winding provided for the high-voltage winding while
the voltage between the low-voltage terminals is controlled
by the series transformer connected with the low-voltage
winding.
In general, a transformer has a multi-winding structure
in which a high-voltage winding to be connected with a
lQ high-voltage primary circuit and a low-voltage winding to
be connected with a low-voltage secondary circuit, some-
times with a tertiary winding for power supply use in a
substation, are wound about an iron core.
With such a multi-winding type transformer as
described above, it is sometimes required to make the
voltages across all or some of the high-voltage primary
winding, the low-voltage secondary winding and the
tertiary winding capable of being adjusted by changing
over the taps provided on the respective windings.
To enable the prior art to be described with the aid
of diagrams, the figures of the drawings will first be
listed.
Figs. l and 2 schematically show examples of a
conventional tap changing transformer;
2~ Fig. 3 shows the electrical wiring of a tap changing
transformer as an embodiment of this` invention;
Fig. 4 shows the electrical wiring of a tap changing
transformer as another embodiment of this invention;
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Fig. S schematically shows in plan the internal
structure of a three-phase on-load tap changing
transformer to which this invention is applied and
Fig. 6 schematically shows in front view the internal
S structure of the transformer shown-in Fig. 5.
Figs. 1 and 2 show the conventional winding structures
of multi-winding type transformer for a single phase. As
shown in Fig. 1, the multi-winding type transformer has
its tertiary, secondary and primary windings 11, 12 and 14
wound concentrically about an iron core in this order
mentioned, i.e., in the order of increasing voltages to be
induced, in view of the respective withstand voltages.
The secondary and primary windings 12 and 14 are provided
respectively with tap windings 13 and 15 in series.
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1 Reference numerals 16 and 17 designate tertiary terminals,
18 and 19 a secondary line terminal and a secondary neutral
terminal, 20 and 21 a primary line terminal and a primary
neutral terminal. In this type of transformer, the voltages
across the primary and secondary windings are controlled
by changing over the taps taken out of the tap windings
13 and 15 by a first and a second no-load or on-load tap
changers 22 and 23 provided separately. In this case,
however, the secondary winding usually generates a low
voltage and therefore only a voltage is developed between the
adjacent taps, the adjacent taps containing only several
turns, so that the structures of the tap windings are
complicated. Moreover, since the primary winding 14 is
also provided with the tap winding 15, the tap winding 13
for the secondary winding 12 is usually located between the
secondary winding 12 ard the tertiary winding 11.
Accordingly, this type of tap changing transformer has a
drawback that the taking-out of lead wires is diff~cult.
Further, since the secondary winding with its low voltage
must conduct a large current, a tap changer ha~ing a small
current capaclty, especially an on-load tap changer, which
is widely used ca~ perform the change-over of taps only
with difficulty. This is another drawback OI the conven-
tional tap changing transformer.
It has therefore been proposed to control the
voltage between the secondary terminals 18 and 19 by a
series transformer ~0 consisting of an exciting winding 3
and a series winding ~2 wound about an iron core 31, as
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1 sho~n in Fig. 2, instead of by the tap winding 1~ provided
for the secondary winding 12 to induce a low voltage therein,
as shown in Fig. 1.
Namely, in this type of a transformer, the voltage
between the high-~oltage primary terminals 20 and 21 is
controlled by changing over the taps o~ the tap winding
provided for the primary winding 14 by the first tap changer
22 while the voltage between the low-voltage secondary
terminals 18 and 19 is regulated by controlling the voltage
across the series winding 32 o~ the series transformer 30
connected with the secondary winding 12 by means of the
exciting winding 32. ~he exciting ~inding 33 o~ t'ne series
transformer 30 is controlled by changing over the taps OI
the tap winding 34 connected with the exciting winding 33
by the second tap changer 23, whereby the voltage generated
by the series winding 32 is regulated.
According to this transformer shown in ~ig. 2, the
problem associated with the on-load tap changer can be
eliminated since the tap voltage (i.e. number of turns from
one tap to ne~t) of the tap winding 34 provided in the main
transformer can be chosen depending on the current capacit~
of the on-load tap changer. In this case, however, the tap
winding 34 must be separately provided in the main trans-
former sc that the structure of the main transformer
becomes complicated and that the radial dimension of the
windings increases to result in the drawback of being large
in size. Moreover, since the tap leads taken out OI the
tap windings 15 and 34 on the primary ar.d secondary sides?
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1 which carry different voltages, must be respectivel~ laid
on through small space in the main trans~ormer, the ~abri-
cation becomes difYicult and also there is a risk that the
layout of ~he leads in the small-space may cause a ~ea~
point in insulation.
One object of this invention is to ~rovide a tap
changing transformer whose fabrication is facilitated by
considerably decreasing the number of the tap leads extended
from a single tap winding provided for common use to tap
changers.
Another o~ject o~ this in~en~lo~ is to provlde a
tap changing transformer in which the changeover of the ta s
of the tap winding can be perfor~ed by tap changers current
on the market.
According to one of the features of this invention
which has been made to attain the above objects, at least
low-voltage winding and a high-voltage winding are wound
about an iron core; the high-voltage winding is pro~ided
with a tap winding having a plurality of taps, which are
changed over by a first tap changer so as to regula~e the
voltage developed between tke high-voltage te~ als; and
the low-voltage winding is provided with the series winding
o~ a series translormer and the voltage between the
secondary windings is regulated by reg~ating the voltage
across the exciting winding o~ the series trans~ormer
through the changeover of all or some of the taps of the
tap winding by a second tap changer.
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Tap changing transformers as embodiments of this
invention will be described below with the aid of ~igs. 3
to 6. Fi~s. ~ and 4 show the embodiments OI t'nis inven~ion
applied to a single ~hase a~paratus, but it ls needless to
say that this invention car be applied also to a three-
phase apparatus.
In the embodiment shown in ~ig. 3, a main trar.s-
former comprises an iron core 120, a tertiar~ winding 101,
a secondary winding 104, a prlmary windlng 107 and a tap
winding 111, the windings 1~1, 104, 107 and 111 being wo~nd
about the ircn core 120. ~he order of windings wound about
the core 120 coincides with the order of increasing ampll-
tudes of voltages. One end OI the high-voltage primar~
winding 107 is connected with a line terminal 108 and the
other end of the primar~ winding 107 is selectively con-
nected with either end of the tap winding 111 via a polarity
changer 110 through a connecting wire 109. ~he ~ap winding
111 has a plurality OI taps 112 which are connected with a
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1 well-known tap selector (not shown) through respective tap
leads so as to be connected with a first tap changer 113.
'~he tap changer 113 is connected with a primary neutral
terminal 114. rrhe structure described above and shown in
~ig. 3 is a well-known polarity changeover system which
has a wide range of voltage regulation by using tap change-
over operations, that is, which regulates the primary
terminal voltage by changing over the taps 112. rrhe polarity
changer 110 may be omitted if the number of the taps is
suitably chosen.
One end of the low-voltage secondary winding 104
is connected with a secondary line terminal 105 and the
other end of the secondary winding 104 is connected through
a connecting wire lQ6 with one end of the series winding
133 of a series transformer 130. '~he other end of the
series winding 133 is connected with a seGondar~ neutral
terminal 115. '~he series transformer 130 comprises the
series winding 133 and an exciting winding 132 both wound
about an iron core 131 different from the iron core 120 of
the main transformer 100. As well known, the voltage
induced in the series winding 133 is controlled by the
exciting winding 132. '~herefore, one of the ends of the
exciting winding 132 of the series transformer 130 is selec-
tively connected via a second polarity changer 122 with
either end of the tap winding 111 through a connecting wire
121 and the other end of the exciting winding 131 is con-
nected with a second tap changer 123 for changing over
plural taps through a connecting wire 124. Accordingly,
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1 with this circuit configuration, the tap winding 111 i~
shared by the primary and secondary winding 107 and 104 so
that the voltages between the primary and the secondary
terminals can be regulated through the changeover of taps
by the first and the second tap changer 110 and 122. The
second polarity changer 122 inserted between the tap winding
111 and the exciting winding 132, also serves to expand the
range of the voltage regulation and therefore may be omitted
if the number of taps is appropriately chosen. ~he egciting
winding 132 is connected via the second polarity changer
with either end of the tap winding 111 so as to use the
whole changeover range, as shown ln ~ig. ~, but it may also
be so connected as to use a part of the whole changeover
range.
~he tap winding 111 need not be tapped in the
same manner as shown in Fig. 3 on both the sides of the
primary winding and the eæciting winding, but provided with
taps depending only on the tap-to-tap voltages and the
capacity of the tap changer itself. ~or example, taps may
be provided on the low-voltage side corresponding to every
two or three taps on the high-vollage side. The first and
the second tap changers 113 and 123 may take each of the
no-load and on-load tap changeover modes without departing
from the scope of this invention.
By constructing a tap changing transformer in
the manner described above, the tap winding 111 of the main
transformer 100 can be used for the control of both the
high-voltage primary power and the low-voltage secondary
11;~01 12
1 power so that the structure of the tap changing trans~ormer
is simpli~ied and it is produced with lower cost.
~ he leads connecting the taps on the high-voltage
side with the selector of the first tap changer 113 are
separate from those connecting the taps on the side of the
exciting winding 132 with the selector of the second tap
changer 123, as shown in Fig. 3, but the selectors of both
the tap changers may be connected with the same tap leads
each connecting together the corresponding taps on both the
sides if all the corresponding tap-to-tap voltages are set
coincident on both sides.
~ ow, a concrete example will be dlseussed ~n which
a tap changing transformer as shown in Fig. 3 has a primary
winding treating 220 + 10% ~+ 8 step) kV with capacity of
100 MVA, a secondary winding treating 33 + lO~o (+ 8 step)
kV with capacity of 60 MVA and a tertiary winding treating
11 kV with capacity of 40 MVA. In this case, the total
tap voltage width (maximum voltage difference possible by
changing the tap) on the primary side is + 22/~
+ 12.7 kV, the current is 239 A from the highest tap (at
242 kV) and 292 A from the lowest tap (at 1 ~ 98 k~), and a
tap-to-tap voltage is approximately 1590 V sO that an
ordinary on-load tap changer can be used. On the other hand,
the total tap voltage width on the secondary side is + 3 ~ 3/
25 ~ = + 1.91 kV, the current is 954 A from the highest tap
(at 36 ~ 3 kV) and 1166 A from the lowest tap (at 29~ 7 kV),
ar,d a tap-to-tap voltage is approximately 239 ~ sO that if
this tap winding is separately provided in the main
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1 transformer as according to the conventional method, one or
two turns will constitute a tap-to-tap portion of the tap
winding. Also, with a heavy current treated, the size of
the tap changer must be increased and the resulting trans-
former becomes uneconomical. ~he number of the re~uiredtap leads for the primary and secondary use per phase is
9 x 2 = 18. Also, the number of the windings is increased.
On the contrary, in the ca~e where the consti-
tution according to the embodiment of this invention is
employed, the series transformer 130 neeas a capacity of
6666 kVA (= (3.3/ ~ ) x 1166 x 3) and the current through
the exciting winding 132 is 175 A (= (~.~/22) ~ 1166) so
that the tap changer 123 on the secondary side may have the
same capacity as the tap changer 113 on the primary side.
Concerning the tap winding 111, on the other hand, the
current takes the maximum value of about 435 A when the
lowest tap on the primary side and the highest tap on the
secondary side are chosen. However, when the lowest taps
on the primary and the secondary sides are chosen, where the
power loss is the maximum for the conventional apparatus,
- current through the tap winding 111 takes a small value of
about 117A, the power loss in the main transformer 100 not
increasing so much.
The greatest advantage of this embodiment is that
only the single tap winding 111 is needed since it operates
for both primary and secondary uses and that the tap changers
113 and 12~ having the same specification can be used if
the tap leads are adjusted to the values of current
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1 described above. Moreover, the interconnections among the
tap leads can be facilitated since the tap winding 111 can
be disposed in the outermost position around the iron co-re
120 and on the side of the neutral point of the high-voltage
primary winding.
Fig. 4 shows a tap changing transformer as another
embodiment of this invention, in which the voltage is
regulated through the transfer switch on the primary side
and the changeover switch on the secondary side. In this
embodiment, a coarse tap winding 125 is connected with the
other end of the high-voltage primary winding 107 with its
one end connecte~ with the primary line terminal 108 ana
a close tap winding 111 having plural taps 112 is connected
with the coarse tap winding 125 or the high-voltage primary
winding 107 via a transfer switch 126 having a pair of
chan$eover terminals P ar~d N. ~he remaining parts are
similar to those in the embodiment shown in Fig. 3. ~his
embodiment can not only enjoy the same effect as attained
by the previous embodiment but also expands the range of
regulation of the voltage across the high-voltage primary
winding by the use of the coarse tap winding 125. It is
further possible in this case to use a transfer switch also
on the secondary side, to utilize only a portion of the
close tap winding, and to use only every two or three taps.
Figs. 5 and 6 show a concrete structure of a
three-phase tap changing transformer the single-phase of
which is shown in Fig. 3 or 4. As shown in these figures,
the three-phase tap changing transformer comprises a
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1 three-phase main transformer 100 T~ith its windings 142 for
three phases wound about an iron core 141 of three-phase
configuration; series transformers l~OU, 130V and 130~J
provided separately for respective phases; first tap changers
11~ for the primary windings; and second tap changers 123
for the secondary windings, for regulating the voltages
across the exciting windings of the respective series trans-
formers, all these members being contained in a tank 140.
In this embodiment, t~o, as described above, since the
corresponding taps on the primary and secondary sides of the
tap windl~g for each pha~e are c~nnecte~ in common and since
only one tap lead 143 is needed for connecting the corres-
ponding pair of the taps with another terminal, the number
of the tap leads can be halved in comparison with the case
where the taps on the primary and secondary sides are
separately wired, so that wiring work is c.onsiderably
facilitated.
The series transformers may be constructed in a
single block, but in this embodiment three series trans-
formers are used, one of them being disposed in the spaceunder the first and second tap changers 11~ and 12~
juxtaposed in the tank 140 and the remaining two being
stacked one upon another (for example, they are integrated
by a metal cramper etc.). With this structure, the other-
wise useless space is effectively utilized so that theresulting three-phase tap changing transformer can be made
compact.
In the above described embodiments, the case is
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1 exclusively enlarged upon where the primary high voltages
ana the secondary low voltages are changed over, but it
should be noted that this invention can equally be applied
to the case where the primary high voltages and the tertiary
5 low voltages are changed over and to the case where the
primary to the tertiary voltages are changed over.
Moreover, this invention can be applied not only
- to a three-phase transformer of Y-Y connection but also to
a three-phase transformer of ~-Y connection, if the above
described techni~ues are applied to the winding~ of the same
phase.
As described above, according to this invention,
in the regulation of different voltages developed across
plural windings through the changeover of taps, all or a
portion of the tap winding provided for the high-voltage
windings is used in common, and the voltage across the
exciting winding of the series transformer is regulated ky
the first tap changer on the high-voltage side and by the
second tap changer on the low-voltage side, whereby only
one tap winding suffices for the required purpose and the
number of the tap leads connected with the taps OI the
tap windings to be changed over by the respective tap
changers can be considerably decreased. Accordingly, the
structure of the tap changing transformer is simplified and
the fabrication thereof is facilitated. Further, since the
tap winding is used in common, the tap changers may be of
the same specification and this leads to economy.
