JPH08316053A - Single phase transformer with central leg core - Google Patents

Abstract

PURPOSE: To provide a single phase transformer in which the tertiary winding is provided on the return path leg while sustaining the equivalent capacity at same level as a transformer where the tertiary winding is provided on the central leg. CONSTITUTION: A tertiary winding comprises two unit tertiary windings 23A, 23B which are mounted, respectively, on two return path legs 12, 13 of a central leg core 1A. The unit tertiary windings 23A, 23B are connected in series such that the fluxes generated therefrom are canceled each other. Since the magnetomotive forces induced by tertiary load currents flowing through the unit tertiary windings 23A, 23B are canceled each other in the magnetic path of central leg core 1A, the exciting winding can be eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single-phase transformer having a so-called central leg iron core, which has one main leg and two return legs sandwiching the main leg, and particularly, the width dimension of the transformer. The present invention relates to a single-phase transformer having a structure in which a tertiary winding is provided on a return leg to shorten the voltage.

[0002]

2. Description of the Related Art High voltage side rated voltage is 500 kv, primary,
When an ultra-high voltage, large capacity transformer with a secondary capacity of 1000 MVA is transported by rail, if one three-phase device is used, weight, length and / or width may exceed the transport limits. It's normal to end up. Therefore, it is assumed that three single-phase transformers substantially constitute one three-phase transformer, and that the single-phase transformers are separately transported during transportation. As the configuration of the single-phase unit adopted at this time, a group of windings is provided on each main leg of the two-leg iron core, or a group of windings is provided on the central leg of the central leg iron core. It is usual that either one is adopted. The former case is adopted to divide the winding into two to reduce the outer diameter when the width dimension during transportation is restricted, and the latter case is adopted when such a restriction is not imposed. In the case of the central leg iron core, there is an advantage that it is advantageous in terms of cost since only one group of windings is required.

FIG. 4 is a layout view of an iron core and a winding of a conventional single-phase transformer having a central leg iron core. In this figure, a central leg iron core 1 includes a central leg 11, two return legs 12 and 13 arranged on the left and right sides of the central leg 11, and upper and lower sides of the central leg 11 and the return legs 12 and 13. The yokes 14 and 15 are magnetically and mechanically connected to each other. The central leg 11 is provided with a high-voltage winding 21 and a low-voltage winding 22, and the return leg 12 is provided with a tertiary winding 23 and an exciting winding 24. The excitation winding 24 is connected in parallel with the low-voltage winding 22 as described later.

A tertiary winding 23 and an excitation winding 2 are provided on the return leg 12.
The reason why the configuration in which 4 is inserted is adopted is as follows.
In a general configuration in which the tertiary winding is also provided on the center leg 11, the diameter of the winding may increase and the width may exceed the transportation limit. Also, since the voltage is the lowest, the tertiary winding is arranged on the innermost diameter side. Since the wires are provided, the diameters of both the high-voltage winding and the low-voltage winding are increased, the number of conductive wires, which are the winding material, is increased, and the load loss is increased and the efficiency is reduced. This is because the price and efficiency of the transformer can be improved by providing a tertiary winding on the return leg. Further, the excitation winding 24 is provided only when the tertiary winding 23 is provided on the return leg 12.
All of the load current that flows into the return leg 12
Also, with this, an abnormal magnetic flux is generated in each iron core leg forming the closed magnetic circuit, the iron core is saturated, and the function as a transformer cannot be achieved.

The central leg 11 has a high-voltage winding 21 and a low-voltage winding 2
Depending on the exciting current supplied by the primary winding of either
The main magnetic flux Φ is generated by being excited by
At the T-shaped part that is the connection part of the central leg 11 with the yoke 14 or 15
Divided on both sides, half of each Φ / 2 is the yoke 14, 15 and return.
The flow is divided into the road legs 12 and 13. The excitation winding 24 is as described above.
Is connected in parallel to the low-voltage winding 22 and its number of turns N _FourIs
Number of turns of low-voltage winding 22 N₂It is set to twice. low pressure
The voltage induced in the winding 22 is directly applied to the excitation winding 24.
Since it is an applied voltage,
The pressure is the voltage per turn of the low voltage winding 22, that is,
Half of the induced voltage per turn of the central leg 11
Therefore, the induced voltage per turn of the return leg 12 is
Half of the central leg 11 and therefore the flux of the return leg 12
Φ which is one half of the magnetic flux Φ of the central leg 11 as shown
/ 2. Is the magnetic flux of the return leg 13 the magnetic flux of the central leg 11?
The value obtained by subtracting the magnetic flux of the return leg 12 from
It becomes Φ / 2 which is the same as that of the road leg 12.

FIG. 5 is a connection diagram of each winding of FIG. this
In the figure, the high-voltage winding 21 is tentatively a primary winding.
Even with this limitation, the following explanation loses generality
Not a thing. Primary current I from U terminal to high voltage winding 21₁
Flows into the low-voltage winding 22 and a current I_2WFlows. one
Current I to the excitation winding 24_FourFlows. This current I_FourIs
Current I_2WAnd flows as a secondary current from the u terminal.
put out. A tertiary load current I is applied to the tertiary winding 23.₃Flows.
Excluding the exciting current component, the current I of the high voltage winding 21₁And low pressure
Current I of winding 22_2WAnd the ampere turns are in equilibrium and the third order
Current I of winding 23 ₃And the current I of the excitation winding 24_FourTomo Anne
Pair turns are in equilibrium. Ie each winding
Number of turns of N₁, N₂, N₃, N_FourTosu
Then, the following equation is established. N₁I₁= N₂I_2W, N₃I₃= N_FourI_Four The secondary current I₂Is the current I_2WFrom current I_FourDeduct
It is a value. That is, I₂= I_2W-I_FourIs. this
Is rewritten, I_2W= I₂＋ I_FourAnd the meaning of this expression
The current flowing in the low voltage winding 22 is the secondary load voltage.
Current and the current in the excitation winding corresponding to the tertiary load current.
It means that

FIG. 6 is a magnetic circuit diagram showing a relationship between a magnetic circuit formed by the central leg iron core and a magnetomotive force for generating a magnetic flux in this magnetic circuit. In this figure, a straight line represents the magnetic circuit of the central leg iron core 1, and each leg of the central leg iron core 1 of FIG. 1 is represented by a straight line. Circles represent magnetomotive force sources, that is, windings.
The correspondence with is clarified. In the figure, in the central leg 11, the ampere-turns (N ₁ I ₁ ) of the high-voltage winding 21 and the ampere-turns (N ₂ I ₂ ) of the low-voltage winding 22 are in opposite directions to each other, which is the primary winding. Ampere turns are balanced except for the exciting current component of the voltage winding 21. Therefore, the magnetomotive force of the central leg 11 is the product (N ₁ I _1e ) of the exciting current component I _1e and the number of turns N ₁ . In the return leg 12, the ampere-turn (N ₃ I ₃ ) of the tertiary winding 23 and the excitation winding 24
Ampere-turn (N ₄ I ₄ ) is balanced with the excitation current component I _4e of the excitation winding 24. Excitation current component I _4e
Since this is supplied from the low voltage winding 22, this component is also I
Like _1e , it is supplied as a primary current.

[0008]

As described above, the exciting winding 24 is provided in order to cancel the magnetomotive force of the current I ₃ of the tertiary winding 23 in the return leg 12. Further, as described above, the ampere-turn of the tertiary winding 23 and the ampere-turn of the exciting winding 24 are the same except for the exciting current component having a much smaller value than the load current, so that the tertiary winding is substantially the same. The line 23 and the excitation winding 24 have the same ampere-turn, that is, the same capacitance. For example, the high-voltage winding 21 and the low-voltage winding 22 have a capacity of 100 MVA and the tertiary winding 2
Assuming that the capacity of 3 is 30 MVA (the capacity of the tertiary winding 23 is usually about 1/3 of the capacity of the high voltage winding 21 and the low voltage winding 22), the sum of the capacities of the respective windings is 100 + 100.
It becomes + 30 + 30 = 260 MVA. This means that the equivalent capacity of this transformer is half this, 130 MVA. On the other hand, generally, the nominal equivalent capacity of a transformer having a tertiary winding is one half of the sum of the primary, secondary, and tertiary capacities, that is, 115 MVA. In a conventional transformer provided with a wire and a tertiary winding, this value corresponds to one half of the sum of the capacities of the windings. That is, in the transformer shown in FIG.
-115) /115≈0.13, that is, the equivalent capacity is increased by about 13%. Since the weight of the transformer is proportional to the third power of the capacity and the price is approximately proportional to the weight, an increase in equivalent capacity of 13% results in a price increase of about 10%.

The object of the present invention is to solve such a problem and to provide a single-phase transformer having a central leg which has a tertiary winding in the return leg and whose equivalent capacity is the same as when the return leg is provided in the central leg. To provide.

[0010]

In order to solve the above problems, according to the present invention, in a single-phase transformer having a central leg iron core and a winding provided on the central leg of the central leg iron core, It is assumed that two return legs arranged on both sides are respectively provided with unit tertiary windings, these two unit tertiary windings are connected in series, and the directions of magnetomotive forces are in the same direction. Further, in this case, the two unit tertiary windings have the same structure including the winding direction, and the lower part of one unit tertiary winding and the upper part of the other unit tertiary winding are connected, and two terminals that are not connected are It may be a terminal that is pulled out to the outside. Also, the two unit tertiary windings have the same structure except that the winding directions are opposite to each other, and the lower or upper part of each unit tertiary winding is connected, and two terminals that are not connected become terminals to be drawn to the outside. Good to do.

[0011]

In the structure of the present invention, the unit tertiary windings are respectively wound around the two return legs and are connected in series so that the magnetic fluxes generated by these two unit tertiary windings cancel each other out. These unit tertiary windings cancel the load current components flowing in the tertiary windings formed by a series circuit of windings.

Further, the two unit tertiary windings have the same structure including the winding direction, the lower part of one unit tertiary winding and the upper part of the other unit tertiary winding are connected, and two terminals which are not connected are externally connected. The two unit tertiary windings generate magnetomotive force in the same direction by making the terminals to be drawn out, and the directions of these magnetomotive forces become opposite magnetomotive forces in the rectangular magnetic path except the central leg. Cancel each other out. Even if the winding directions of the two unit tertiary windings are reversed and the structures are made the same and the lower or upper portions of the respective unit tertiary windings are connected so that the two terminals that are not connected are the terminals that are drawn to the outside,
The magnetomotive forces cancel each other out as before.

[0013]

EXAMPLES The present invention will be described below based on examples.
FIG. 1 is a layout view of a central leg iron core and a winding of a single-phase transformer showing an embodiment of the present invention. The same components as those in FIG. The difference from FIG. 4 of FIG. 1 is that the return leg 13 is also provided with a winding, and instead the return leg 12 is provided with only one winding. The windings provided on the return legs 12 and 13 are unit tertiary windings 23A and 23B, respectively. Since the arrangement of the windings is different from that of FIG. 4, the size of the central leg iron core 1A is different from the size of the central leg iron core 1 of FIG.
That is, in FIG. 4, since the tertiary winding 23 and the excitation winding 24 are inserted in the return leg 12, the lengths of the yokes 14 and 15 on the right side from the central leg 11 are longer than those on the left side.
On the other hand, in FIG. 1, since the winding arrangement is symmetrical, the left and right lengths of the yokes 14 and 15 with the central leg 11 as a boundary are the same. That is, the central leg iron core 1A has a bilaterally symmetrical structure. This is also a natural consequence of the fact that the winding arrangement is symmetrical.

FIG. 2 is a connection diagram of the windings shown in FIG. 1. The high voltage winding 21 and the low voltage winding 22 are the same as those in FIG. Since the two unit tertiary windings 23A and 23B are connected in series as shown, the currents flowing through the unit tertiary windings 23A and 23B are the same. FIG. 3 is a magnetic circuit diagram showing the excitation system of the central leg iron core 1 of FIG. 1, and is similar to FIG. In this figure, the magnetomotive forces of the unitary tertiary windings 23A and 23B are oriented in the same direction as indicated by the arrows in the figure. The currents flowing through these unitary tertiary windings 23A and 23B are the same, and since the configurations including the number of turns are also made the same, the amperage of each number of turns, that is, the magnitude of the magnetomotive force is also the same. Therefore, both return legs 1
The magnetomotive force of the rectangular magnetic path formed by the upper and lower yokes 14 and 15A is completely canceled. On the other hand, the magnetomotive force of the central leg 11 cancels the magnetomotive force of the high-voltage winding 21, which is the primary winding, excluding the exciting current component, and the magnetomotive force of the low-voltage winding 22 cancels each other. A magnetic flux Φ is generated in 11, and the magnetic flux Φ is divided into both sides, and Φ is applied to the yokes 14A and 15A and the return legs 12 and 13, respectively.
The point where the / 2 splits is the same as that in FIG.

As described above, by adopting the construction in which the tertiary winding 23 is provided with two unit tertiary windings 23A and 23B on the return legs 12 and 13, respectively, and these are connected in series,
Even if the excitation winding 24 of FIG. 4 is not provided, the unit tertiary winding 23
A and 23B do not cancel each other's magnetomotive force to generate an abnormal magnetic flux in the central leg iron core 1A. The capacity of each of the unit tertiary windings 23A and 23B is equal to that of the conventional tertiary winding 23.
In practice, if the number of turns of the tertiary winding 23 is set to 2N ₃ as shown in FIG. 6, the number of turns of each of the unit tertiary windings 23A and 23B becomes N ₃ as shown in FIG. Becomes
The conductor weight of the tertiary winding in the embodiment including the two unit tertiary windings 23A and 23B is substantially the same as that of the conventional tertiary winding 23. That is, the winding capacity of the excitation winding 24 shown in FIG. 1 can be saved as compared with the conventional single-phase transformer. In terms of the above-mentioned capacity conversion, the equivalent capacity of the conventional single-phase transformer is 130 MVA, whereas the equivalent capacity of the single-phase transformers of FIGS. 1 to 3 is 115 MVA. Of course, in this connection, the effects of reducing the weight of the single-phase transformer, reducing the cost, and improving the efficiency can be obtained.

[0016]

As described above, according to the present invention, the tertiary winding is made up of two windings.
It consists of two unit tertiary windings, and each of the two return legs is provided with a unit tertiary winding, and the magnetic fluxes generated by these two unit tertiary windings are connected in series so as to cancel each other. Since the load current components cancel each other out by these unitary tertiary windings, the excitation winding is no longer required as in the past, so the equivalent capacity of the single-phase transformer is reduced by the amount of the excitation winding, and the weight is reduced accordingly. It is possible to obtain the effects of reduction of cost, cost reduction and efficiency improvement.

Even if the two unit tertiary windings have the same structure including the winding direction and the lower part of one unit tertiary winding and the upper part of the other unit tertiary winding are connected in series, Even if the unit tertiary windings have the same structure but the winding directions are reversed and the lower or upper portions of the respective unit tertiary windings are connected in series, the magnetomotive forces cancel each other out as described above, The same effect as described above can be obtained.

[Brief description of drawings]

FIG. 1 is a layout diagram of a center leg core and a winding of a single-phase transformer showing an embodiment of the present invention.

2 is a connection diagram of the winding of FIG.

FIG. 3 is a magnetic circuit diagram showing an excitation system of the iron core shown in FIG.

[Fig. 4] Layout of iron core and winding of a conventional single-phase transformer

5 is a connection diagram of the winding of FIG.

FIG. 6 is a magnetic circuit diagram showing an excitation system of the iron core of FIG.

[Explanation of symbols]

1, 1A ... Central leg core, 11 ... Central leg, 12, 13 ... Return leg, 14, 14A, 15, 15A ... Yoke, 21 ... High voltage winding, 22 ... Low voltage winding, 23 ... Tertiary winding, 23A , 23
B ... Unit tertiary winding

Claims (3)

[Claims] 1. A single-phase transformer comprising a central leg iron core and a winding provided on the central leg of the central leg iron core, wherein a unitary tertiary winding is provided on each of two return legs arranged on both sides of the central leg. A single-phase transformer provided with a central leg iron core, wherein these two unit tertiary windings are connected in series and the directions of magnetomotive forces are the same. 2. Two unit tertiary windings have the same structure including the winding direction, one unit tertiary winding lower part and the other unit tertiary winding upper part are connected, and two terminals not connected are The single-phase transformer with a central leg iron core according to claim 1, wherein the single-phase transformer serves as a terminal that is drawn out to the outside. 3. A unit tertiary winding having the same structure except that the winding directions are opposite to each other, connecting the lower or upper part of each unit tertiary winding, and two terminals that are not connected to each other being a terminal to be drawn to the outside. A single-phase transformer having a central leg iron core according to claim 1.