CA1120112A - Tap changing transformer - Google Patents
Tap changing transformerInfo
- Publication number
- CA1120112A CA1120112A CA000308748A CA308748A CA1120112A CA 1120112 A CA1120112 A CA 1120112A CA 000308748 A CA000308748 A CA 000308748A CA 308748 A CA308748 A CA 308748A CA 1120112 A CA1120112 A CA 1120112A
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- winding
- tap
- voltage
- transformer
- series
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Abstract
ABSTRACT OF THE DISCLOSURE
A tap changing transformer in which the voltage developed between the high-voltage terminals is adjusted by changing over the taps of the tap winding provided for the high-voltage winding by a first tap changer while the voltage between the low-voltage terminals is controlled by the series transformer connected with the low-voltage winding. The series winding connected with the low-voltage winding and the exciting winding for exciting the series winding constitutes the series transformer and one end of the exciting winding is connected with the tap winding of the high-voltage winding while the other end of the exciting winding is connected with a second tap change for changing over the taps of the tap winding. Accordingly, the exciting winding of the series transformer and the tap winding connected therewith through the second tap changer are caused to operate in combination, whereby the number of tap leads can be considerably decreased, which facilitates the taking-out of the leads and simplifier the structure of the tap changing transformer.
A tap changing transformer in which the voltage developed between the high-voltage terminals is adjusted by changing over the taps of the tap winding provided for the high-voltage winding by a first tap changer while the voltage between the low-voltage terminals is controlled by the series transformer connected with the low-voltage winding. The series winding connected with the low-voltage winding and the exciting winding for exciting the series winding constitutes the series transformer and one end of the exciting winding is connected with the tap winding of the high-voltage winding while the other end of the exciting winding is connected with a second tap change for changing over the taps of the tap winding. Accordingly, the exciting winding of the series transformer and the tap winding connected therewith through the second tap changer are caused to operate in combination, whereby the number of tap leads can be considerably decreased, which facilitates the taking-out of the leads and simplifier the structure of the tap changing transformer.
Description
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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;
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 O~Z
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 5 _ , .
ll;~Oli2 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, ll'~Ol~Z
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 li'~O112 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 OllZ
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 ll'~Oli'Z
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 OliZ
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.
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 O~Z
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 5 _ , .
ll;~Oli2 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, ll'~Ol~Z
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 li'~O112 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 OllZ
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 ll'~Oli'Z
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 OliZ
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.
Claims (10)
1. A tap changing transformer comprising a main transformer having at least a high-voltage winding and a low-voltage winding wound about an iron core, said high-voltage winding being provided with a tap winding having plural taps which are changed over by a first tap changer;
and a series transformer having a series winding and an exciting winding wound about an iron core, wherein said series winding of said series transformer is connected with one end of said low-voltage winding of said main transformer and one end of said exciting winding of said series trans-former is connected with one end of said tap winding while the other end of said exciting winding is connected with at least some of said taps of said tap winding through a second tap changer, whereby the voltages on the high-voltage side and the low-voltage side are independently regulated by said first and second tap changers, respectively.
and a series transformer having a series winding and an exciting winding wound about an iron core, wherein said series winding of said series transformer is connected with one end of said low-voltage winding of said main transformer and one end of said exciting winding of said series trans-former is connected with one end of said tap winding while the other end of said exciting winding is connected with at least some of said taps of said tap winding through a second tap changer, whereby the voltages on the high-voltage side and the low-voltage side are independently regulated by said first and second tap changers, respectively.
2. A tap changing transformer as claimed in Claim 1, wherein said main transformer is provided with two low-voltage windings and at least one of said low-voltage windings is connected with said series winding of said series transformer.
3. A tap changing transformer as claimed in Claim 1, wherein said plural taps of said tap winding to be changed over by said first and second tap changers are connected through common tap leads with said first and second tap changers.
4. A tap changing transformer as claimed in Claim 1, wherein said main transformer and said series transformer are contained in a casing and said first and second tap changers are juxtaposed in said casing.
5. A tap changing transformer as claimed in Claim 1, wherein said high-voltage winding of said main transformer is provided with a coarse tap winding and a close tap winding having plural taps and said close tap winding is selectively connected with said high-voltage winding or said coarse tap winding by a transfer switch.
6. A tap changing transformer as claimed in Claim 1, wherein said tap winding having said plural taps is con-nected with said high-voltage winding through a polarity changer.
7. A tap changing transformer as claimed in Claim 1, wherein said exciting winding of said series transformer is connected with one end of said tap winding through a polarity changer.
8. A tap changing transformer comprising a main transformer having a high-voltage winding and two low-voltage windings wound about an iron core, said high-voltage winding being provided with a tap winding having plural taps which are changed over by a first tap changer, with a polarity changer interposed therebetween; and a series transformer having a series winding and an exciting winding wound about an iron core, wherein said series winding of said series transformer is connected with one end of one of said low-voltage windings of said main transformer and one end of said exciting winding of said series transformer is connected with one end of said tap winding through a polarity changer while the other end of said exciting winding is connected with at least some of said taps of said tap winding through a second tap changer, whereby the voltages on the high-voltage and the low-voltage sides are independently regulated by said first and second tap changers, respectively.
9. A tap changing transformer comprising a main transformer having a high-voltage winding and two low-volt-age windings wound about an iron core, said high-voltage winding being provided with a coares tap winding and a close tap winding having plural taps which are changed over by a first tap changer and said close tap winding is selec-tively connected with said high-voltage winding or said coarse tap winding through a transfer switch; and a series transformer having a series winding and an exciting winding wound about an iron core, wherein said series winding of said series transformer is connected with one end of one of said low-voltage windings of said main transformer and one end of said exciting winding of said series transformer is connected with one end of said close tap winding through a polarity changer while the other end of said exciting wind-ing is connected with at least some of said taps of said tap winding through a second tap changer, whereby the voltages on the high-voltage and the low-voltage sides are independently regulated by said first and second tap changers, respectively.
10. A tap changing transformer as claimed in Claim 1, 8 or 9, wherein said main transformer is of three-phase configuration and two similar series transformers are addi-tionally provided to be adapted for three-phase operation, said main transformer and said series transformers being contained in a casing and wherein said first and second tap changers are juxtaposed to each other in said casing and one of said series transformers is disposed under said juxtaposed tap changers while the remaining series trans-formers are stacked one upon another.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP97352/77 | 1977-08-13 | ||
| JP9735277A JPS5431531A (en) | 1977-08-13 | 1977-08-13 | Tap changing transformer |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1120112A true CA1120112A (en) | 1982-03-16 |
Family
ID=14190086
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000308748A Expired CA1120112A (en) | 1977-08-13 | 1978-08-04 | Tap changing transformer |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPS5431531A (en) |
| CA (1) | CA1120112A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103606445A (en) * | 2013-12-04 | 2014-02-26 | 正泰电气股份有限公司 | Method for effectively reducing current passing through on-load tap-changer of transformers |
-
1977
- 1977-08-13 JP JP9735277A patent/JPS5431531A/en active Granted
-
1978
- 1978-08-04 CA CA000308748A patent/CA1120112A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103606445A (en) * | 2013-12-04 | 2014-02-26 | 正泰电气股份有限公司 | Method for effectively reducing current passing through on-load tap-changer of transformers |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5714565B2 (en) | 1982-03-25 |
| JPS5431531A (en) | 1979-03-08 |
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| MKEX | Expiry |