JPH0547570A - Three-phase transformer - Google Patents

Abstract

PURPOSE:To obtain a three-phase transformer which can be changed and controlled in three-phase voltage only by providing taps to the two-phase coils out of three-phase coils. CONSTITUTION:Taps tu and tw are provided to the ends of two-phase coils C1u and C1w out of three-phase coils on the voltage control side in a three- phase transformer provided with a primary and a secondary winding. Both the ends of another coil C1v are connected between the specific taps tuh and twh of the taps of the two-phase coils C1u and C1w, and the taps tu and tw of the coils C1u and C1w provided with taps are connected to the opposite ends.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a three-phase transformer having a tap.

[0002]

2. Description of the Related Art In a conventional three-phase transformer with a tap, the tap is drawn from each winding on the voltage adjusting side. Therefore, a star connection and a delta connection three-phase transformer having three windings on the voltage adjustment side have tap leads for three phases, and a V connection transformer has tap leads for two phases. Was.

[0003]

In the winding manufacturing process, since the tap pull-out work requires a wide variety of manual work, a lot of man-hours are required.

In particular, star connection or delta connection,
In the case of a general three-phase transformer with taps, it is necessary to provide a tap for each winding of three phases, so that many steps are required to manufacture the windings.

The tap switching mechanism must be compatible with switching of three phases, but in the case of a load tap switching device, if a tap switching mechanism of three phases is provided, the structure becomes large and complicated and expensive. I couldn't avoid it.

In the V-connection transformer, the windings for two phases are sufficient. Therefore, in the case of the transformer with taps, the taps may be provided in the windings for two phases, and the taps may be provided for the windings for three phases. Much less effort is required to manufacture the winding than if it were provided.

Particularly, in the load tap changer, the case where the switching mechanism for two phases is provided is much smaller and can be manufactured at a lower cost than the case where the switching mechanism for three phases is provided. In the case of, a V-connection transformer is often used.

However, the V-connection transformer is inferior in function as a transformer because of low utilization rate of winding capacity and poor balance of impedance voltage among three phases.

An object of the present invention is to provide a three-phase transformer having taps, which requires only a small number of tap leads, has a high winding capacity utilization factor, and has a good balance between the three phases of impedance voltage. Especially.

[0010]

SUMMARY OF THE INVENTION In the present invention, first to third windings C1u to C1w are provided on the voltage adjusting side of a three-phase transformer, and the construction of these windings and the connection between the windings are made. Do the following:

In the invention described in claim 1, the first
The winding C1u is exposed from the taps provided at one end and the other end of the winding C1u. The second winding C1v is exposed from its one end and the other end, and the third winding C1w is exposed from its one end and the other end and taps provided on the one end side. Then, while pulling out one end of the first winding C1u to the outside, any one of the other end of the first winding C1u and the tap is selected by the tap switching mechanism and pulled out to the outside. Further, one end of the third winding C1w and one of the taps are selected by the tap switching mechanism and drawn out to the outside, and the other end of the third winding C1w is one end of the first winding C1u. Connect to. Further, one end of the second winding C1v is connected to the other end of the first winding C1u and a specific lead of the tap, and the other end of the second winding C1v is connected to one end of the third winding C1w and Connect to a particular tap out of the tap.

In the invention described in claim 2, the first winding C1u is composed of the main winding C1um and the tap winding C1ut, and the second winding C1v has no tap. Composed of only. The third winding C1w is composed of a main winding C1wm and a tap winding C1wt. Then, one end of the main winding C1um of the first winding is drawn to the outside, and any one of the taps of the tap winding C1ut of the first winding is selected by the tap switching mechanism and Be withdrawn. Further, any one of the taps of the tap winding C1wt of the third winding is selected by the tap switching mechanism and drawn out to the outside, and the tap winding C of the first winding C
One of the one end and the other end of 1ut is selected by the polarity switching mechanism and connected to the other end of the main winding C1um of the first winding. Further, one of the one end and the other end of the tap winding C1wt of the third winding is selected by the polarity switching mechanism and connected to one end of the main winding C1wm of the third winding.
The other end of the main winding C1wm of the first winding is the main winding C1u of the first winding.
Connected to one end of m. One end of the second winding C1v is connected to the other end of the main winding C1um of the first winding, and the other end of the second winding C1v is connected to one end of the main winding C1wm of the third winding. Connected.

In the invention described in claim 3, the first winding C1u is constituted by the main winding C1um and the tap winding C1ut, and the second winding C1v is constituted by only the winding not having the tap. Composed. The third winding C1w is the main winding C1w
It is composed of m and the tap winding C1wt. One end of the main winding C1um of the first winding is drawn to the outside, and one of the one end and the other end of the tap winding C1ut of the first winding is selected by the polarity switching mechanism and drawn to the outside. To be done. Further, one of the one end and the other end of the tap winding C1wt of the third winding is selected by the polarity switching mechanism and drawn out to the outside, and from the taps of the tap winding C1ut of the first winding. Any one tap is selected by the tap switching mechanism and is connected to the other end of the main winding C1um of the first winding. Arbitrary 1 from the taps of the third winding C1wt
Taps are selected by the tap switching mechanism and connected to one end of the main winding of the third winding, and the main winding C of the third winding is
The other end of 1wm is connected to one end of the main winding C1um of the first winding. Further, one end of the second winding C1v is connected to the other end of the main winding C1um of the first winding, and the other end of the second winding C1v is the third
Is connected to one end of the main winding C1wm.

In the invention described in claim 4, the first winding C1u is exposed through taps provided at one end, the other end and the other end thereof, and the second winding C1v is exposed. It is performed from one end and the other end. The third winding C1w is the first
The winding C1u and the second winding C1v are wound in the opposite directions, and the third winding is exposed from one end, the other end, and taps provided on the other end side. One end of the first winding C1u is drawn to the outside, and the other end of the first winding C1u and any one of the taps is selected by the tap switching mechanism and drawn to the outside. The other end of the third winding C1w and an arbitrary one of the taps are selected by the tap switching mechanism and drawn out to the outside, and one end of the third winding C1w is one end of the first winding C1u. Connected to. Second winding C1v
One end of the first winding C1u is connected to the other end of the first winding C1u and a specific output of the taps, and the other end of the second winding C1v is connected to one end of the third winding C1w and the specific output of the taps. Connected to.

In the invention described in claim 5, the first
The winding C1u is composed of a main winding C1um and a tap winding C1ut, and the second winding C1v is composed only of a winding having no tap. The third winding C1w is a main winding C wound in the opposite direction to the first winding and the second winding.
1wm and tap winding C1wt. One end of the main winding C1um of the first winding is connected to one end of the main winding C1wt of the third winding and is pulled out to the outside, and the tap of the tap winding C1ut of the first winding An arbitrary one is selected by the tap switching mechanism and drawn out. Also the third
Any one of the taps of the winding C1wt of the winding of the coil is selected by the tap switching mechanism and drawn out to the outside.
Any one of the one end and the other end of the tap winding C1ut of the first winding is selected by the polarity switching mechanism and connected to the other end of the main winding C1um of the first winding. Further, one of the one end and the other end of the tap winding C1wt of the third winding is selected by the polarity switching mechanism and connected to one end of the main winding C1wm of the third winding. The other end of the main winding C1wm of the wire is connected to one end of the main winding C1um of the first winding. One end of the second winding C1v is connected to the other end of the main winding C1um of the first winding, and the other end of the second winding C1v is the main winding C1w of the third winding.
Connected to the other end of m.

In the invention described in claim 6, the first winding C1u is constituted by the main winding C1um and the tap winding C1ut, and the second winding C1v is constituted only by the winding having no tap. Composed. The third winding C1w is the main winding C1w wound in the opposite direction to the first winding and the second winding.
It is composed of m and the tap winding C1wt. One end of the main winding C1um of the first winding is connected to one end of the main winding C1wt of the third winding and is drawn to the outside, and one end and the other end of the tap winding C1ut of the first winding. Any one of them is selected by the polarity switching mechanism and drawn out. Third
Any one of the one end and the other end of the tap winding C1wt of the first winding is selected by the polarity switching mechanism and drawn out to the outside, and any one of the taps of the first winding tap winding C1ut is selected. The taps are selected by the tap switching mechanism and connected to the other end of the main winding C1um of the first winding. Also the third
Any one of the taps of the winding C1wt of the third winding is selected by the tap switching mechanism and connected to the other end of the main winding of the third winding. One end of the second winding C1v is connected to the other end of the main winding C1um of the first winding, and the other end of the second winding C1v is connected to the other end of the main winding C1wm of the third winding. Connected.

In each of the above inventions, the first winding C1u and the third winding C1w are preferably arranged on the side legs of the three-leg iron core, and the second winding is the central leg of the three-leg iron core. It is better to place In this case, the cooling duct in the windings arranged on the side legs of the iron core shall be provided only in the width direction of the transformer, and the cooling duct in the windings arranged in the center leg of the iron core shall be provided only in the depth direction of the transformer. Is preferred.

[0018]

As described above, in the present invention, both ends of the other one winding are connected between the specific taps of the two windings provided with the tap portion on one end side, The ends of the two windings having the taps and the ends on the opposite side were connected to each other, and the connection between the ends on the opposite side was drawn out, and selected from each of the two taps. Any one tap is drawn to the outside, and these outside drawers are connected to a three-phase power supply. With the above configuration, the voltage vectors of the three windings form an A-shaped voltage vector having an apex angle of 60 degrees. This voltage vector is a voltage vector having a portion extending from the apex angle in the direction in which the other apex angle of the delta connection remains the same and the phase difference between the other two apex angles is 60 degrees. When the connections are made as described above, the conversion and adjustment of the three-phase voltage can be performed only by providing the tap portion on the two-phase winding in the three-phase winding. Further, since the above-mentioned connection basically belongs to the delta connection system, the winding capacity utilization factor is high and the balanced state between the three phases of the impedance voltage is good.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the three-phase transformer of the present invention, in the winding system on the voltage adjusting side, only the winding of two phases among the three phases has taps. Here, the "voltage adjustment side winding system" means a winding side having a plurality of voltage specifications at a constant iron core magnetic flux density. In the embodiments described below, in the two-winding transformer or the single-winding transformer, the winding system on the voltage adjustment side is the primary side.

Embodiments of the present invention will be described below with reference to the drawings.

[Embodiment 1] FIG. 1 is a connection diagram between windings of this embodiment. The three-phase transformer of the present embodiment includes the first to third
Of the primary windings C1u, C1v, C1w and the first to third secondary windings C2u, C2v, C2w of two of the three phases of the primary winding.
Only the phase is tapped. In addition, one set of the primary winding and the secondary winding arranged on the same iron core leg is referred to as a pair of windings.

First primary winding C1u and first secondary winding C2
u, the second primary winding C1v and the second secondary winding C2v, and the third primary winding C1w and the third secondary winding C2w are a pair of windings, respectively. The primary winding for tapping is C
Although any two windings in 1u, C1v and C1w can be used, in the present embodiment, tap drawing is performed in the first primary winding C1u and the third primary winding C1w. And Connect one end and the other end of the first primary winding C1u to 1
u and 1ue, and one end and the other end of the second primary winding C1v are 1v and 1ve, respectively. The third primary winding C1w
Let 1w and 1we be one end and the other end, respectively. The number of turns of the first primary winding C1u and the number of turns of the third primary winding C1w are set equal to each other. Here, "one end and the other end of the winding"
Means a winding start end or a winding end end, and if one end is a winding start end, the other end is a winding end end. The winding direction of all windings is the same for all windings unless otherwise specified. The taps of the first primary winding C1u are tu1, tu2, ..., From the other end to the one end.
Let tuh, ..., Tu (k-1), tuk. Tap tu1 is the first
The same terminal as the other end 1ue of the primary winding C1u. Furthermore the third
Of the primary winding C1w from the one end side to the other end side are tw1, tw2, ..., Twh, ..., tw (k-1), twk. The tap tw1 is the same terminal as the one end 1w of the third primary winding C1w. The taps tu1 to tuk of the first primary winding C1u are collectively referred to as a first tap portion tu, and similarly the taps tw1 to twk of the third primary winding C1w are collectively referred to as a second tap. Call part tw. The numbers at the end of subscripts such as tu1 and tw1 indicate tap numbers, and the symbol k representing the maximum number of subscripts in the case of 5 taps is 5. The tap voltages of the same tap numbers are the same. tu1 and tw1 are the highest taps, and tuk and twk are the lowest taps. Here, the highest tap means a tap with which the primary voltage is minimized under the condition that the secondary voltage is constant. Further, a set of taps having the same tap number in the first tap part tu and the second tap part tw will be referred to as a pair of taps. The taps tu1 and tw1 are a pair of taps, and generally the taps tun and twn (n is an arbitrary integer of 1 to k) are a pair of taps. Further, the three line terminals in the primary side system are a first primary side terminal U1, a second primary side terminal V1 and a third primary side terminal W1.

In this embodiment, one end 1u of the first primary winding C1u is connected to the first primary side terminal U1. First one
Any one of the taps tu1 to tuk of the secondary winding C1u is selected by the tap switching mechanism St and connected to the second primary side terminal V1. Tap switching mechanism St
The tap selected by will be referred to as a selection tap. When the tap switching mechanism is a tap switching device, the tap connected to the movable contactor is the selection tap, and the tap connected to the tap switching piece of the tap switching board is the selection tap. The tap switching mechanism St shown in the drawing symbolically shows only the fixed contact (or tap switching piece) portion of the tap switching mechanism.

Taps tw1 to t of the third primary winding C1w
In wk, a tap paired with the selection tap on the first tap part tu side is selected by the tap switching mechanism St,
It is connected to the third primary side terminal W1. For example, when the selection tap in the first tap section tu is tun (n is an arbitrary integer between 1 and k), the selection tap in the second tap section tw is twn. One end 1u of the first primary winding C1u
Is connected to the other end 1we of the third primary winding C1w, and one end 1v of the second primary winding C1v is connected to the tap tuh of the first primary winding C1u. The other end 1ve of the second primary winding C1v is connected to the tap tuh of the third primary winding C1w. That is, the taps tuh and twh are one of the taps selected by the tap switching mechanism St, and
It is also a terminal that is always directly connected to the winding of the other phase (secondary primary winding). As described above, the tap that is always directly connected to the winding of the other phase is called a plain tap. The plain tap is a specific one of tu1 to tuk and tw1.
1 to twk, both taps having the same subscript (that is, a pair of taps), but a central tap (a tap located in the central portion between the highest tap and the lowest tap) It is desirable to set it in the vicinity. Further, it is desirable that the plain tap is a rated tap. As can be seen from FIG. 1, 1 when the plain tap is selected
The connection on the secondary side is equivalent to the delta connection. On the secondary side, the first secondary winding C2u to the third secondary winding C2w are delta-connected and connected to the first secondary terminal U2 to the third secondary terminal W2. . However, the feature of the three-phase transformer of the present invention lies in the winding configuration on the voltage adjustment side and its connection,
The connection of the winding (secondary winding in this example) that is not on the voltage adjustment side is not limited to the delta connection described above, and may be a star connection.

FIG. 2 shows the highest taps tu1, t in FIG.
It is a vector diagram showing a voltage vector and a reference direction of current when w1 is selected. FIG. 3 is a vector diagram showing the voltage vector and the current reference direction when the transparent taps tuh and twh are selected in FIG.
Further, FIG. 4 is a vector diagram showing the voltage vector and the current reference direction when the lowest taps tuk and twk are selected in FIG. FIG. 5 is a vector diagram showing the voltage vector on the secondary side in FIG. 1 and the reference direction of the current. The terminal U2 shown in parentheses in FIGS.
, V2, W2 represent secondary side terminals in the case of an autotransformer. However, the current vector is shown not for the autotransformer but for the two-winding transformer shown in FIG. In the vector diagrams of FIGS. 2 to 5, E1uv, E1vw and E1wu are respectively C1.
u, C1v, and C1w are induced voltages, and I1u, I1v, and I1w are currents that flow into the primary side terminals U1, V1, and W1 from the power source side, respectively. Further, I1cu is the current of the first primary winding C1u when the selection tap is in tu1 to tuh, and is the terminal of the first primary winding C1u when the selection tap is in tuh to tuk. It is the current between U1 and the select tap. I1cw is the current of the first primary winding C1w when the selection tap is in tw1 to twh, and I1cw is the terminal of the first primary winding C1w when it is in the selection tap twh to twk. It is the current between U1 and the select tap. When the selection tap is within tuh or tuk, the current between the selection tap and the tap tuh in the first primary winding C1u is
It is equal to the current in the second primary winding C1v. Similarly, when the select tap is between twk and twk, the current between the select tap in the third primary winding C1w and the tap twh is equal to the current in the second primary winding C1v.

FIG. 6 is a current vector diagram on the secondary side when the windings are connected as shown in FIG. 1, which is the same as the current vector on the secondary side delta connection. The current vector in FIG. 6 represents the case where the load power factor is 1 in a three-phase balanced load.

FIG. 7 is a vector diagram showing the current distribution on the primary side of the three-phase transformer of the present invention, which is the maximum tap tu1, t.
It shows the case where w1 is selected. FIG. 7 is a current vector diagram corresponding to the voltage vector diagram of FIG.

FIG. 8 is a vector diagram showing the current distribution on the primary side when the transparent taps tuh and twh are selected.
This corresponds to the voltage vector diagram of FIG. 3, and FIG.
FIG. 5 is a vector diagram showing a current distribution on the primary side when the lowest taps tuk and twk are selected, and corresponds to the vector diagram of FIG. 4.

Next, the magnitude of the current and the phase angle of each winding on the primary side will be described. The number of turns between the first primary side terminal U1 and the second primary side terminal V1 in the first primary winding C1u (the number of turns between the first primary side terminal U1 and the selection tap). ) Is Na, the number of turns between the first primary side terminal U1 and the third primary side terminal W1 in the third primary winding C1w is also Na. The number of turns of the second primary winding C1v is Nb. Na varies depending on the selection tap, but Nb is constant. Here, the winding turn ratio R
Define t by the following equation (1). Rt = Na / Nb (1) Further, when the absolute value of I1cu and I1cw is Ia and the absolute value of I1cv is Ib, the winding current ratio Ri is the following (2).
It is defined by an expression. Ri = Ia / Ib (2) 0 Next, the phase angle of the inter-winding current is determined. Since the phase angle between I1cv and I1cu and the phase angle between I1cv and I1cw are equal, this is designated as θ1. Here, the inter-winding current ratio Ri and the inter-winding current phase angle θ1 are expressed as follows using the inter-winding turn number ratio Rt. Ri = (Rt ² -3Rt +3) ^0.5 / Rt (3) θ1 = cos ^-1 [(Rt -1.5) (Rt ² -3Rt +3) ^-0.5 ] (4) Winding current ratio Ri and FIG. 10 is a diagram showing a relationship with the number of turns Rt between windings. When Rt = 1, Ri = 1
And Ri has a minimum value of 0.5 when Rt = 2.
At Rt = 2, Ri turns to increase. FIG. 11 shows the relationship between the phase angle θ1 of the winding current and the winding turn ratio Rt. When Rt = 1, θ1 = 120 °, and θ1 decreases as Rt increases. At Rt = 2 and 3, θ1 is 60 ° and 30 °, respectively.
In FIGS. 10 and 11, a wide range of Rt is shown to facilitate understanding of the trends of Ri and θ1 with respect to R2.
Is in the vicinity (for example, about 0.9 to 1.1). R
When t = 1, it corresponds to a normal delta winding.

Based on the above, the equilibrium state between the phases of the winding capacity utilization factor and the impedance voltage in the three-phase transformer of the present invention will be described. When θ1 = 120 °,
Since the phase difference of the voltage between the windings and the phase difference of the current between the windings are equal to each other, the winding capacity utilization factor is 1, which is the maximum. As described above, the practical turn-to-winding turn number ratio Rt is in the vicinity of 1, and in this case θ1 is in the vicinity of 120 degrees as can be seen from FIG. Therefore, it can be seen that the winding capacity utilization factor of the three-phase transformer of the present invention is extremely higher than the winding capacity utilization factor (0.866) of the V-connection transformer.

Considering the equilibrium state between the phases of the impedance voltage, since the windings corresponding to the respective phases are provided, one of the three phases has a winding that is not corresponding to the V-connection transformer. , The parallel state between the phases of the impedance voltage is much better. Specifically, the interphase equilibrium state of the impedance voltage is best when the inter-winding turn number Rt is 1, and is considered to be three-phase perfect equilibrium or close thereto. A good equilibrium state between the phases of the impedance voltage means a small interphase imbalance of the voltage fluctuation rate, which is an important requirement in terms of supplying high-quality power.

Next, the arrangement and structure of the winding and the lead wire will be described. The basic structure of the three-phase transformer is a three-leg iron-core inner structure, and the legs of the three cores are sequentially arranged from one side to the other side to form first-phase legs or third-phase legs. The first phase leg and the third phase leg will be referred to as side legs, and the second phase leg will be referred to as the central leg. Theoretically, the first primary winding C1u and the third primary winding C1w with taps can be placed on any two legs. However, by limiting the winding having the taps to a specific leg, the effect of the present invention can be exerted more greatly.

In the winding of the three-phase transformer according to the present invention, the winding thickness of the second primary winding C1v having no tap portion is equal to that of the first primary winding C1u having a tap portion and the first primary winding C1u having a tap portion. 1 of 3
It is smaller than the winding thickness of the next winding C1w. Therefore, the first
If both the primary winding C1u and the third primary winding C1w of the above are arranged on the side legs, one of the first primary winding C1u and the third primary winding C1w is placed in the central leg. The size in the width direction of the iron core is smaller than that in the case of. Needless to say, when the primary winding and the secondary winding are concentrically arranged, it is preferable to dispose the winding having the taps outside.

FIG. 12 is a front view showing a partially broken three-phase transformer of the embodiment of the present invention, and FIG. 13 is a partially broken view of the three-phase transformer of the embodiment of the present invention. It is the top view shown. Iron core 10 has rims (legs) 10L1 to 10L3
And a yoke portion 10Y. Where the side legs are 1
0L1 and 10L3 and the central leg is 10L2.

The three-phase transformer according to the present invention can be applied to both a bare transformer (for example, a dry transformer) and a cased transformer (for example, an oil-filled transformer). Since it is in the main body part (winding and iron core part), only the main body part is shown in the figure. Also, regarding the dimensional relationship of the transformer, only the main body part will be described. A second primary winding C1v, which is a primary winding having no tap, is arranged on the center leg 10L2, and
Second secondary winding C which is a secondary winding of a pair of primary winding C1v of
Place 2v. The side leg 10L1 has a tap 1
The first primary winding C1u which is one of the secondary windings is arranged, and the first secondary winding C2u which is a secondary winding of the pair of the first primary winding C1u is arranged. A third primary winding C1w, which is one of the primary windings having a tap, is arranged on the side leg 10L3, and the third primary winding C1w is a secondary winding paired with the third primary winding C1w. The secondary winding C2w of No. 1 is arranged.

In FIG. 12, a1 is the width of the iron core, which corresponds to the length of the yoke portion 10Y. Also a2
Is the width dimension of the transformer and is the maximum dimension in the width direction of the transformer. In FIG. 13, b is the maximum transformer depth dimension, and when the dimension of the winding depth direction differs depending on the phase,
The maximum dimension is the transformer maximum dimension. When the depth dimensions of the respective windings are expressed separately, the depth dimensions of the first primary winding C1u, the second primary winding C1v, and the third primary winding C1w are represented by bu, bv, and Expressed as bw. That is, the maximum of bu, bv and bw is equal to the maximum transformer depth dimension b.

By the way, in electrical equipment such as a switchboard installed in a business space in a building such as an office or a sales floor, the electrical equipment is downsized, and in order to reduce the protrusion from the wall surface, the electrical equipment is made thin. Is strongly required. Therefore, for transformers that occupy the maximum space in these electric facilities, it is important to design the transformers and reduce the maximum depth dimension thereof.

Next, paying attention to the fact that the winding thickness of one phase in the three phases, which is the external characteristic of the three-phase transformer according to the present invention, is smaller than the winding thickness of the other two phases. This section describes a device to reduce the dimension between transformer depths by suppressing an increase in the width of the iron core without increasing the transformer width. Generally, in a transformer having a relatively small capacity (several tens of kVA), the cooling duct in the winding is provided in a part of the winding circumferential direction. The cooling duct provided in a part of the winding circumferential direction as described above is called a partial duct. Conventionally, the partial duct D has been provided in the front and rear portions (front portion and rear portion) of the depth dimension of the winding. This is because the partial duct does not increase the core size. However, in the three-phase transformer of the present invention, it is not appropriate to follow the conventional arrangement of partial ducts.

If the partial ducts are provided in the width direction of the transformer for the three-phase windings, the maximum dimension of the transformer depth can be reduced as compared with the case where the partial ducts are provided in the depth direction of the transformer. The following waste occurs in the three-phase transformer of the invention. When partial ducts in the transformer width direction are provided in all of the three-phase windings, the width direction of the transformer and the width of the iron core increase, while the depth dimension (depth dimension) of the outer circumference of the winding of the center leg is increased. The unbalanced state in the transformer depth direction in which bv) is smaller than the depth dimension (depth dimension bu, bw) on the outer peripheral surface of the side leg winding is not improved. That is, even if the depth dimension of the winding of the central leg which is originally small is further reduced, it does not effectively contribute to the reduction of the maximum dimension of the transformer. Therefore, in the three-phase transformer of the present invention, the dimension in the width direction of the transformer is reduced. In order to reduce the maximum depth dimension of the transformer while suppressing the increase, partial ducts D are provided in the front and rear parts in the depth direction of the transformer in the winding of the central leg, and the transformer is provided in the winding of the side leg. Partial ducts D are provided on the left and right sides in the width direction. Providing the partial ducts D at the front and rear portions in the depth direction of the transformer means providing cooling ducts only at the front and rear portions in the depth direction of the transformer. Further, providing the partial ducts D on the left and right portions of the transformer in the width direction means that the cooling ducts are provided only on the left and right portions of the transformer in the width direction. In addition, B is a barrier for interphase insulation, and I is an insulating layer for insulation between the primary winding and the secondary winding or for insulation between the secondary winding and the iron core.

When the partial ducts are arranged as described above,
The depth dimension (bv) of the center leg on the outer circumference of the winding, the depth dimension of the side leg on the outer circumference of the winding (bv) and the depth dimension of the side leg on the outer circumference of the winding (bu, bw) are substantially the same. Often. Below, the conditions will be simplified to describe whether the dimensions of the transformer vary depending on the position of the partial duct. Let e1 be the winding thickness of the side leg winding where there is no partial duct, and e2 be the winding thickness of the center leg winding where there is no partial duct.
The difference between e1 and e2 is e3. Let e4 be the winding thickness in the portion of the side leg winding where the partial duct exists, and let e5 be the winding thickness in the portion of the center leg winding where the partial duct exists. Here, the difference between e4 and e5 is equal to e3. Further, the thickness of the partial ducts (the total thickness of the partial ducts when the partial ducts are provided at two locations in the winding thickness direction as shown in FIGS. 12 and 13)
Let e6 be e6 = e4 -e1 = e5 -e2.

Table 1 shows how the dimensions increase and decrease as compared with the case where the partial ducts for both the central leg and the side leg windings are provided before and after the depth of the transformer (comparison reference case). In addition to the above, the relationship between the depth dimensions of the first primary winding to the third primary winding is shown. Case I and Case II in Table 1 mean the following conditions. In case I, as shown in the embodiment of the present invention, the partial ducts of the windings of the central leg are provided in the front and rear portions in the transformer depth direction, and the partial ducts of the windings of the side legs are provided on the left and right in the transformer width direction. It is provided. In Case II, partial ducts are provided on the left and right sides of the transformer width direction for both the windings of the center leg and the side legs.

[0042]

[Table 1]

As can be seen from Table 1, if, for example, e6 = e3, in case I, the maximum transformer depth dimension b becomes e6 smaller than the comparison reference case, and the iron core width dimension a
While 1 is 2e6 larger, in Case II,
The maximum transformer depth dimension b is reduced by e6 and the iron core width dimension a1 is increased by 4e6 with respect to the reference case. It is obvious that the case I (the embodiment of the present invention) is preferable when the reduction in the depth of the transformer is emphasized and the effects of downsizing the entire transformer and reducing the required materials are taken into consideration.

In the above description, the bulging in the winding thickness direction of the winding due to the tap drawing and the required space outside the winding for tap drawing are ignored. However, ignoring them often has a considerable impact on the overall floor space of the transformer.

In case I of Table 1, when the maximum transformer depth dimension is determined by the winding depth dimension of the side leg, as a method of further reducing the maximum transformer depth dimension,
There is a method of drawing out the first tap component tu and the second tap component tw at both ends in the transformer width direction.
The chain line segment in FIG. 12 represents the case where tap drawing is performed at the above position.

FIG. 14 is a connection diagram between windings in the case of an autotransformer. In the same figure, the secondary side terminal U2 is shared with the primary side terminal U1, and one end 1v and the other end 1ve of the second primary winding C1v are designated as the secondary side terminals V2 and W2, respectively.
The current vector in the case of the autotransformer as shown in FIG. 14 is different from the vector diagrams shown in FIGS. 6 to 9, but the illustration is omitted.

In the autotransformer with the interwinding connection of FIG. 14, the voltage phase difference between the primary side and the secondary side is zero at any selection tap. In the side-extending delta connection or inscribed delta connection that has been conventionally used as a three-phase autotransformer, the voltage phase difference between the primary side and the secondary side changes due to the selection tap, which causes troubles in parallel operation. However, the inter-winding connection of FIG. 14 does not cause such trouble.

[Embodiment 2] In this embodiment, the winding of the tap portion is separated from the winding portion having no in-phase tap portion, and the inter-winding connection is shown in FIG. Here, the winding of the tap portion is called a tap winding, and the winding having no tap portion is called a main winding. The first primary winding is composed of a main winding C1um and a tap winding C1ut, and the third primary winding is composed of a main winding C1wm and a tap winding C1wt. Second
The primary winding C1v has no tap. Tap winding C1ut
Has taps tu1 to tuk, and tap t
uk has the same polarity as one end 1u of the main winding C1um, and tap t
u1 has the same polarity as the other end 1ue of the main winding C1um. The tap winding C1wt has taps tw1 to twk,
The tap tw1 has the same polarity as the one end 1w of the main winding C1wm,
The tap twk has the same polarity as the other end 1we of the main winding C1wm.
One end 1u of the main winding C1um of the first primary winding is connected to the first primary side terminal U1. Any one of the taps tu1 to tuk of the tap winding C1ut of the first primary winding is selected by the tap switching mechanism St and connected to the second primary side terminal V1.

Among the taps tw1 to twk of the tap winding C1wt of the third primary winding, the taps that form a pair with the selection taps on the first tap portion tu side are selected by the tap switching mechanism St, and the third taps are selected. Is connected to the primary side terminal w1. Taps tu1 and tuk of the tap winding C1ut of the first primary winding
One of the two is selected by the polarity switching mechanism Sp,
The other end 1ue of the main winding C1um of the first primary winding is connected. The tap selected by the polarity switching mechanism Sp will be referred to as a connection tap. At the taps tw1 and twk of the tap winding C1wt of the third primary winding,
A tap forming a pair with the connection tap on the tap portion tu side of is selected by the polarity switching mechanism Sp and connected to one end 1w of the main winding C1wm of the third primary winding. One end 1u of the main winding C1um of the first primary winding is connected to the main winding C1 of the third primary winding.
It is connected to the other end 1we of 1wm. One end 1v of the second primary winding C1v is connected to the other end 1u of the main winding C1um of the first primary winding, and the other end 1ve of the second primary winding C1v is connected to the third end 1v. 1
It is connected to one end 1w of the main winding C1wm of the next winding. The highest taps are the taps tu1 and tw1 when the taps tuk and twk are selected by the polarity switching mechanism Sp. The lowest tap is the tap tuk in the state where the taps tu1 and tw1 are selected by the polarity switching mechanism Sp.
And twk. The tap that is connected by the polarity switching mechanism Sp and is selected by the tap switching mechanism St at the same time is a plain tap.

As described above, when the tap winding is switched to the same polarity connection or the opposite polarity connection with respect to the main winding, 2k-1 kinds of voltage can be obtained for k tap pull-outs of the tap winding. Therefore, it is suitable when many tap voltages are required. The terminals U2, V2, W2 shown in parentheses in FIG. 15 are secondary terminals in the case of an autotransformer.

FIG. 16 is a connection diagram between windings showing a modification of FIG. 15, in which the tap switching mechanism St and the polarity switching mechanism Sp are connected.
The mounting position of is replaced with the mounting position in FIG. In this embodiment, one end 1u of the main winding C1um of the first primary winding is connected to the first primary side terminal U1. Further, any one of the taps tu1 and tuk of the tap winding C1ut of the first primary winding is selected by the polarity switching mechanism Sp and connected to the second primary side terminal V1. Further, in the taps tw1 and twk of the tap winding C1wt of the third primary winding, the tap paired with the connection tap on the first tap tu side is selected by the polarity switching mechanism Sp, and the third tap is selected.
Is connected to the primary side terminal W1. Further, any one of the taps tu1 to tuk of the tap winding C1ut of the first primary winding is selected by the tap switching mechanism St, and the main winding C1um of the first primary winding is selected. Is connected to the other end 1ue. Tap tw1 of tap winding C1wt of the third primary winding
At twk to twk, a tap paired with the selection tap on the first tap portion tu side is selected by the tap switching mechanism St and connected to one end 1w of the main winding C1wm of the third primary winding. One end 1u of the main winding C1um of the first primary winding is connected to the other end 1we of the main winding C1wm of the third primary winding. One end 1v of the second primary winding C1v is connected to the other end 1ue of the main winding C1um of the first primary winding, and the second primary winding C1v
The other end 1ve of 1v is connected to one end 1w of the main winding C1wm of the third primary winding.

When the inter-winding connection shown in FIG. 16 is performed, the number of taps that are directly connected to the primary side terminal is limited to those having the tap numbers 1 and k. The insulation reinforcement measure can be simpler than in the case of the interwinding connection of FIG. In addition,
Terminals U2, V2, W2 shown in parentheses in FIG.
Is a secondary side terminal in the case of an autotransformer.

[Embodiment 3] FIG. 17 is a connection diagram between windings showing the present embodiment. This embodiment is similar to the third embodiment in FIG.
The primary winding C1w is wound in the opposite direction to the other primary windings. In the inter-winding connection diagrams (FIGS. 1 and 14 to 17 and later-described FIGS. 18 and 19) of the present specification, the diagonal direction of the rectangular portion showing the winding symbolically indicates the winding direction of the winding. That is, if the winding direction of the winding whose diagonal direction is upper right is right winding, the winding direction of the winding whose diagonal direction is upper left is left winding. First primary winding C
One end 1u of 1u is connected to the first primary side terminal U1, and any one of the taps tu1 to tuk of the first primary winding C1u is selected by the tap switching mechanism St. , Second primary side terminal V1. Among the taps tw1 to twk of the third primary winding C1w, a tap paired with the selection tap on the first tap portion tu side is selected by the tap switching mechanism St and connected to the third primary side terminal W1. To be done. One end 1u of the first primary winding C1u is connected to one end of the third primary winding C1w, and one end 1u of the second primary winding C1v is connected.
v is connected to the tap tuh of the first primary winding C1u.
The other end 1ve of the second primary winding C1v is connected to the third primary winding C1w.
Connected to tap twh. In the inter-winding connection shown in FIG. 17, if one end side of the primary winding is the winding start side,
Both the taps of the primary winding C1u and the third primary winding C1w are located on the winding end side. In the case of the layer winding structure, since the winding end side is located on the outer peripheral side of the winding, the winding directions of the first winding and the third winding are opposite to each other as shown in FIG. With this, tap drawing becomes easy. The terminal U2 shown in parentheses in FIG.
, V2, W2 are secondary side terminals in the case of an autotransformer.

[Embodiment 4] FIG. 18 is a connection diagram between windings showing the present embodiment. In this embodiment, the third primary winding (main winding C1vm, tap winding) in FIG. C1wt)
It is wound in the opposite direction to the other primary winding. In this embodiment, one end 1 of the main winding C1um of the first primary winding is
u is connected to the first primary terminal U1. Any one of the taps tu1 to tuk of the tap winding C1ut of the first primary winding is selected by the tap switching mechanism St and connected to the second primary side terminal V1. In the taps tw1 to twk of the tap winding C1wt of the third primary winding, a tap paired with the selection tap on the first tap portion tu side is selected by the tap switching mechanism St, and the third first winding is selected.
It is connected to the next terminal W1. Any one of the taps tu1 and tuk of the tap winding C1ut of the first primary winding is selected by the polarity switching mechanism Sp and connected to the other end 1ue of the main winding C1um of the first primary winding. To be done. In the taps tw1 and 1wk of the tap winding C1wt of the third primary winding, the taps paired with the connection taps on the first tap portion tu side are selected by the polarity switching mechanism Sp and the third primary winding is selected. Main wire winding C1wm
Is connected to the other end 1we. Main winding C1 of the first primary winding
One end 1u of um is connected to one end 1w of the main winding C1wm of the third primary winding, and one end 1v of the second primary winding C1v is the main winding C1um of the first primary winding. Is connected to the other end 1ue.
The other end 1ve of the second primary winding C1v is connected to the other end 1we of the main winding C1wm of the third primary winding. The primary winding
When the main winding and the tap winding are concentrically arranged, the main winding is arranged inside and the tap winding is arranged outside. Further, in the case of the layer winding structure, it is preferable to set one end side to the winding start side because the voltage applied to the facing surface of the main winding and the tap winding becomes extremely small.

As shown in FIG. 18, when the winding directions of the first winding and the third winding are opposite to each other, both of the first winding and the third winding are wound. The one end side can be the winding start side. The terminals U2, V2 and W2 shown in parentheses in FIG. 18 are secondary side terminals in the case of an autotransformer.

FIG. 19 is a connection diagram between windings showing a modification of FIG. 18, in which the tap switching mechanism St and the polarity switching mechanism Sp are connected.
18 corresponds to the case where the mounting position is replaced with the mounting position in FIG. In this embodiment, one end 1u of the first primary winding C1um is connected to the first primary side terminal U1. Also, the tap t of the tap winding C1ut of the first primary winding
Any one of u1 and tuk is selected by the polarity switching mechanism Sp and connected to the second primary side terminal V1. Furthermore, the taps tw1 and twk of the tap winding C1wt of the third primary winding
, A tap paired with the connection tap on the side of the first tap portion tu is selected by the polarity switching mechanism Sp, and the third tap
It is connected to the next terminal W1. Any one of the taps tu1 to tuk of the tap winding C1ut of the first primary winding is selected by the tap switching mechanism St, and
Is connected to the other end 1ue of the main winding C1um of the primary winding. Taps tw1 to t of tap winding C1wt of the third primary winding
In wk, a tap paired with the selection tap on the first tap part tu side is selected by the tap switching mechanism St,
The other end 1we of the main winding C1wm of the third primary winding is connected. One end of the main winding C1um of the first primary winding is connected to one end of the main winding C1wm of the third primary winding. The second one
One end 1v of the secondary winding C1v is the main winding C1um of the first primary winding.
Connected to the other end 1ue of the second primary winding C1v of the other end 1ve
Is connected to the other end 1we of the main winding C1wm of the third primary winding.

When the winding-to-winding connection shown in FIG. 19 is performed, the taps that are directly connected to the primary side terminal are limited to taps having tap numbers 1 and k. The reinforcing measure can be simplified as compared with the case of winding connection in FIG. The bracket terminals U2, V2, and W2 shown in parentheses in FIG. 19 are secondary terminals in the case of an autotransformer.

In the above description, the winding system on the voltage adjusting side is the primary winding side, but it goes without saying that the winding system on the voltage adjusting side may be the secondary winding side. Also, on any winding side in a multi-winding transformer (eg, a 3-winding transformer),
The winding configuration according to the present invention can be applied.

[0059]

According to the present invention, both ends of another winding are connected between the respective specific taps of the two windings provided with the taps at one end, and the taps are provided. Since the three windings are connected by connecting the taps of the two windings and the ends on the opposite side, the
Exchange of three-phase voltage by simply providing a tap on the phase winding,
It is possible to obtain a three-phase transformer which not only can be adjusted but also has a high utilization factor of the winding capacitance and a good equilibrium state between the three phases of the impedance voltage.

[Brief description of drawings]

FIG. 1 is a connection diagram between windings according to a first embodiment of the present invention.

2 is a vector diagram showing a reference direction of a voltage vector and a current on the primary side when the highest tap is selected in the winding connection of FIG. 1. FIG.

3 is a vector diagram showing a voltage vector on the primary side and a vector diagram showing a reference direction of current when a plain thread tap is selected in the inter-winding connection of FIG. 1. FIG.

FIG. 4 is a vector diagram showing a reference direction of a voltage vector and a current on the primary side when the lowest tap is selected in the winding connection of FIG. 1.

FIG. 5 is a vector diagram showing a reference direction of a voltage vector and a current on the secondary side in the inter-winding connection of FIG.

FIG. 6 is a vector diagram showing a current on the secondary side in the inter-winding connection of FIG.

FIG. 7 is a vector diagram showing a primary side current in FIG.

FIG. 8 is a vector diagram showing a primary side current in FIG.

9 is a vector diagram showing a primary side current in FIG.

FIG. 10 is a diagram showing the relationship between the winding current ratio and the winding turn number ratio.

FIG. 11 is a diagram showing a relationship between an inter-winding current phase angle and an inter-winding turn number ratio.

FIG. 12 is a partially cutaway front view of a three-phase transformer according to an embodiment of the present invention.

FIG. 13 is a partially cutaway plan view of a three-phase transformer according to an embodiment of the present invention.

FIG. 14 is a connection diagram between windings in the case where the autotransformer is used in the first embodiment of the present invention.

FIG. 15 is a connection diagram between windings according to a second embodiment of the present invention.

FIG. 16 is a connection diagram between windings in a modified example of the second embodiment of the present invention.

FIG. 17 is a connection diagram between windings according to a third embodiment of the present invention.

FIG. 18 is a connection diagram between windings according to a fourth embodiment of the present invention.

FIG. 19 is a connection diagram between windings in a modified example of the fourth embodiment of the present invention.

[Explanation of symbols]

U1 ... First primary side terminal, V1 ... Second primary side terminal, W
1 ... Third primary side terminal, C1u ... First primary winding, C1v ...
Second primary side winding, C1w ... Third primary winding, C1um ... First primary main winding, C1ut ... First primary tap winding, C1w
m ... third primary main winding, C1wt ... third primary tap winding, tu1, tuh, tuk ... first primary winding (first primary tap winding) tap, tu ... 1st tap part: 1st 1
Tw, the general term for the taps of the secondary winding (first primary tap winding)
1, twh, twk ... Tap of the third primary winding (third primary tap winding), tw ... Third tap portion: Third primary winding (third primary tap winding) ) Taps, St ... tap switching mechanism, Sp ... polarity switching mechanism, U2 ... first secondary side terminal, V2 ... second secondary side terminal, W2 ... third secondary side terminal, C2u ... First secondary winding, C2v ... Second secondary winding, C
2w ... third secondary winding, 10 ... iron core, 10L ... rim portion, 1
0L1, 10L3 ... side leg, 10L2 ... center leg, 10Y
… Yoke part, C… partial duct.

Claims (8)

[Claims] 1. A three-phase transformer having a tap, wherein first to third windings C1u to C1w are provided on a voltage adjusting side, and the first winding C1u and the third winding C1w are respectively provided. A tap is provided, the first winding C1u is exposed from one end and the other end, and the tap provided on the other end side, and the second winding C1v is exposed from one end and the other end. Of the winding C1w is performed from one end and the other end and a tap provided on one end side, one end of the first winding C1u is drawn out, the other end and the tap of the first winding C1u Any one of
One of the taps is selected by the tap switching mechanism and drawn out to the outside, and one end of the third winding C1w and any one of the taps are selected.
The individual lead wires are selected by the tap switching mechanism and led out to the outside, the other end of the third winding C1w is connected to one end of the first winding C1u, and one end of the second winding C1v is The other end of the first winding C1u is connected to a specific output of the taps, and the other end of the second winding C1v is connected to a specific output of the one end of the third winding C1w and the taps. A three-phase transformer characterized in that it is connected to. 2. A three-phase transformer having a tap, which has first to third windings C1u to C1w on the voltage adjustment side, and the first winding C1u includes a main winding C1um and a tap winding C1ut. The second winding C1v is composed only of a winding having no tap, the third winding C1w is composed of a main winding C1wm and a tap winding C1wt, and One end of the main winding C1um is drawn to the outside, and any one of the taps of the tap winding C1ut of the first winding is selected by a tap switching mechanism and drawn to the outside. Any one of the taps of the tap winding C1wt of the first winding is selected by the tap switching mechanism and is drawn to the outside, and one of the one end and the other end of the tap winding C1ut of the first winding is selected. Of the main windings of the first winding selected by the polarity switching mechanism. It is connected to the other end of C1um, and one of the one end and the other end of the tap winding C1wt of the third winding is selected by the polarity switching mechanism and the main winding C1wm of the third winding is connected. One end of the main winding C1wm of the third winding is connected to one end of the main winding C1um of the first winding, and one end of the second winding C1v is connected to the first winding. Main winding C
Is connected to the other end of 1 um, and the other end of the second winding C1v is the main winding C of the third winding.
A three-phase transformer characterized by being connected to one end of 1wm. 3. A three-phase transformer having a tap, which has first to third windings C1u to C1w on the voltage adjustment side, and the first winding C1u includes a main winding C1um and a tap winding C1ut. The second winding C1v is composed only of a winding having no tap, the third winding C1w is composed of a main winding C1wm and a tap winding C1wt, and One end of the main winding C1um is drawn to the outside, and one of the one end and the other end of the tap winding C1ut of the first winding is selected by a polarity switching mechanism and drawn to the outside. Any one of one end and the other end of the tap winding C1wt of the first winding is selected by the polarity switching mechanism and drawn out to the outside, and any one of the taps of the tap winding C1ut of the first winding is selected. One tap is selected by the tap switching mechanism,
It is connected to the other end of the main winding C1um of the first winding and any one tap is selected by the tap switching mechanism from the taps of the tap winding C1wt of the third winding. The main winding C1wm of the third winding is connected to one end of the main winding of the third winding, and the other end of the main winding of the first winding is connected to one end of the main winding C1um of the first winding. One end of the winding C1v is the main winding C of the first winding.
Is connected to the other end of the first winding, and the other end of the second winding C1v is connected to the main winding C of the third winding.
Three-phase transformer characterized by being connected to one end of 1wm. 4. A three-phase transformer having a tap, wherein first to third windings C1u to C1w are provided on the voltage adjustment side, and the first winding C1u is connected to one end and the other end and the other end side. Of the second winding C1v is performed from one end and the other end, and the third winding C1w is the first winding C1u and the second winding C.
It is wound in the opposite direction with respect to 1v, the third winding is exposed through taps provided at one end and the other end, and the other end side, and one end of the first winding C1u is pulled out to the outside. And the first
The other end of the winding C1u and the tap of any one of the taps are selected by the tap switching mechanism and drawn out to the outside, and the other end of the third winding C1w and any one of the taps are tapped.
The individual lead wires are selected by the tap switching mechanism and drawn out to the outside, one end of the third winding C1w is connected to one end of the first winding C1u, and one end of the second winding C1v is The other end of the first winding C1u is connected to a specific lead of the taps, and the other end of the second winding C1v is connected to one end of the third winding C1w and a particular lead of the taps. Three-phase transformer characterized by being connected. 5. A three-phase transformer having a tap, which has first to third windings C1u to C1w on the voltage adjustment side, and the first winding C1u includes a main winding C1um and a tap winding C1ut. The second winding C1v is composed only of a winding having no tap, and the third winding C1w is wound in the opposite direction to the first winding and the second winding. Main winding C1wm and tap winding C1wt
And one end of the main winding C1um of the first winding is connected to one end of the main winding C1wt of the third winding and is drawn to the outside, and the tap of the first winding is formed. Any one of the taps of the winding C1ut is selected by the tap switching mechanism and drawn out, and any one of the taps of the tap winding C1wt of the third winding is selected by the tap switching mechanism. One of the one end and the other end of the tap winding C1ut of the first winding is selected by a polarity switching mechanism and is selected to be drawn out to the outside of the main winding C1um of the first winding. Connected to the other end, one of the one end and the other end of the tap winding C1wt of the third winding is selected by the polarity switching mechanism to be connected to one end of the main winding C1wm of the third winding. And the other end of the main winding C1wm of the third winding is connected to the main winding C1um of the first winding. Is connected to one end, one end of the second winding C1v the main winding C of the first winding
Is connected to the other end of 1 um, and the other end of the second winding C1v is the main winding C of the third winding.
A three-phase transformer characterized by being connected to the other end of 1wm. 6. A three-phase transformer having a tap, which has first to third windings C1u to C1w on the voltage adjusting side, and the first winding C1u includes a main winding C1um and a tap winding C1ut. The second winding C1v is composed only of a winding having no tap, and the third winding C1w is wound in the opposite direction to the first winding and the second winding. Main winding C1wm and tap winding C1wt
And one end of the main winding C1um of the first winding is connected to one end of the main winding C1wt of the third winding and is drawn to the outside, and the tap of the first winding is formed. Any one of one end and the other end of the winding C1ut is selected by the polarity switching mechanism and is drawn to the outside, and one of the one end and the other end of the tap winding C1wt of the third winding is It is selected by the polarity switching mechanism and drawn out to the outside, and any one of the taps of the tap winding C1ut of the first winding is selected by the tap switching mechanism and the main winding of the first winding is selected. The main winding of the third winding is connected to the other end of the winding C1um, and one of the taps of the tap winding C1wt of the third winding is selected by a tap switching mechanism. Is connected to the other end of the second winding C1v, and one end of the second winding C1v is connected to the main winding C of the first winding.
Is connected to the other end of 1 um, and the other end of C1v of the second winding is the main winding C of the third winding.
A three-phase transformer characterized by being connected to the other end of 1wm. 7. The first winding and the third winding are arranged on side legs of the three-leg core, and the second winding is arranged on a central leg of the three-leg core. The three-phase transformer according to any one of claims 1 to 6. 8. The cooling duct in the winding arranged on the side leg of the iron core is provided only in the width direction of the transformer, and the cooling duct in the winding arranged on the center leg of the iron core is arranged only in the depth direction of the transformer. The three-phase transformer according to claim 7, wherein the three-phase transformer is provided.