JPH0883721A - Three-phase transformer - Google Patents

Abstract

PURPOSE: To provide a three-phase transformer capable of surely converging a magnetic flux leakage by a magnetic shield so as to prevent a tank from increasing locally in temperature, low in loss, and simple in structure even if the three-phase transformer has such a structure that it is composed of the tank split into several parts in a horizontal direction, and a high-voltage lead is led out through a through-hole provided to the tank. CONSTITUTION: A three-leg iron core 1 possessed of main legs each wound with a set of a low-voltage winding wire 2 and a high-voltage winding wire 3 is housed in a tank 4, and a through-hole 8 is provided to the center of the tank wall which confronts the winding wires of three phases. A high-voltage lead 7 extending from the high-voltage winding 3 is led out of the tank 4 through the through-hole 8. Magnetic shields 5 are formed of material such as silicon steel plate which is high in permeability to a magnetic flux. The shield 5 are arranged in parallel on the inner wall of the tank 4 as separated from each other in a vertical direction avoiding the high-voltage lead 7 and the through-hole 8, aligning their axes with the arrangement direction of the windings, and keeping their axes as long as the length of a space between the ends of the windings 2 and 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-phase transformer provided with a magnetic shield on the inner wall surface of a tank for converging leakage flux from a winding.

[0002]

2. Description of the Related Art Generally, when a transformer takes a load, a magnetic flux leaks from a winding. FIG. 5 is a sectional view of a three-phase transformer showing an example of generation of leakage magnetic flux. This three-phase transformer is configured by arranging a low voltage winding 2 and a high voltage winding 3 around a tripod core 1 and accommodating them in a tank 4. When a load is connected to such a three-phase transformer for operation, a leakage magnetic flux generated from the low voltage winding 2 and the high voltage winding 3 is generated as shown by a broken line in the figure as an example. This leakage magnetic flux is in tank 4
When incident on the metal structure that constitutes the, the stray loss may increase, and the stray loss may cause a local temperature rise. This reduces the quality, performance and reliability of the transformer. Therefore, in order to reduce or eliminate such a problem, as shown in FIGS. 6 and 7, measures are taken to provide the magnetic shield 5 on the inner wall surface of the tank 4. FIG. 6 is a sectional view of a conventional three-phase transformer body,
FIG. 7 is a plan view of a conventional three-phase transformer body. In such a conventional technique, a magnetic shield 5 made of a material such as a grain-oriented silicon steel plate through which magnetic flux easily passes is provided along the vertical direction of the inner wall surface of the tank 4 facing the high-voltage winding 3 of each phase. .

When a load is connected to the conventional three-phase transformer having the above-mentioned structure and operated, the low voltage winding 2 and the high voltage winding 3 are connected.
The leakage flux between the gaps of the magnetic flux strays in the portion other than the tripod core 1, but the magnetic flux straying in the wall direction of the tank 4 therein does not enter the tank 4 and has a magnetic permeability higher than that of the tank 4. It flows in the shield 5. Therefore, the stray loss generated can be reduced as compared with the case where the tank 4 does not overheat and the magnetic shield 5 is not provided.

[0004]

However, the conventional three-phase transformer as described above has some problems. First, as shown in FIGS. 6 and 7, in the configuration of the conventional three-phase transformer in which the dedicated magnetic shield 5 is provided for each phase winding, the magnetic shield 5 divides the magnetic flux. In order not to do so, it is preferable that the tank inner wall surface is configured to be connected in the vertical direction. However, in a three-phase transformer having a configuration in which the tank 4 is horizontally divided into a plurality of parts such as a bell-type three-phase transformer as shown in FIGS.
It is necessary to divide the magnetic shield 5 of each phase in accordance with a and 6b. Therefore, not only the structure of the transformer becomes complicated, but also a part of the magnetic flux enters the tank 4 in the vicinity of the divided portions 5a and 5b of the magnetic shield.
As a result, there is a problem that the concentration of magnetic flux causes a local temperature rise of the tank 4.

Further, in the case of actually manufacturing a three-phase transformer, in order to pull out the lead 7 of the winding to the outside, a through hole is formed in the side surface of the tank 4 facing the winding as shown in FIGS. It may be necessary to provide 8. Since the magnetic shield 5 achieves its unique purpose of converging the leakage magnetic flux, its mounting range is naturally limited. Therefore, it is often difficult to avoid the through hole 8 and to dispose the magnetic shield 5 dedicated to each winding without separating it.

The present invention was devised to solve the above-mentioned problems of the prior art, and its main purpose is to arrange the magnetic shields separately in the vertical direction of the inner wall surface of the tank. Even so, it is an object of the present invention to provide a three-phase transformer having a simple structure that can surely converge the leakage magnetic flux with a magnetic shield and avoid a local temperature rise in the tank. Further, another invention of the present invention effectively converges the leakage magnetic flux in a three-phase transformer having a structure in which a high voltage lead is drawn out from a through hole provided in a tank and a tank divided in a horizontal direction. Is to provide a three-phase transformer that can.

[0007]

In order to achieve the above object, the invention of claim 1 stores windings wound around the outer circumference of a plurality of iron core legs arranged in a tank. In the three-phase transformer consisting of, a plurality of magnetic shield plates having an axial length extending in the direction in which the plurality of windings are arranged and having a length between the end portions of the windings, which axial length is at least at both ends, It is characterized in that the plurality of magnetic shield plates are arranged in parallel with their axial directions facing the winding arrangement direction and separated in the vertical direction of the inner wall surface of the tank.

According to a second aspect of the present invention, in the three-phase transformer according to the first aspect, the transformer tank is provided with a through hole in the center thereof for drawing out the high voltage lead from the winding, and the through hole portion is aligned with the through hole. It is characterized in that the magnetic shields are separately arranged.

According to a third aspect of the present invention, in the three-phase transformer according to the first aspect, the transformer tank has a divided portion, and the tank is divided horizontally in the divided portion and faces the divided portion of the tank. It is characterized in that no magnetic shield plate is arranged on the inner wall surface of the tank.

[0010]

The three-phase transformer of the present invention having the above structure has the following functions.

In the case of the three-phase transformer, the leakage magnetic fluxes incident on the same high position of the tanks facing the windings of the respective phases have the same magnitude and are out of phase by 120 degrees. In the three-phase transformer of the present invention, a plurality of magnetic fields having an axial length extending in the direction in which the plurality of windings are arranged and having a length between the ends of the windings located at least at both ends are provided. A shield plate is provided, and the plurality of magnetic shield plates are arranged with their axial directions facing the winding arrangement direction. Therefore, the magnetic fluxes in the magnetic shield attached to the inner wall of the tank through the three phases cancel each other in vector by combining the incident magnetic fluxes for the three phases with the phases shifted by 120 degrees.

In the three-phase transformer of the present invention, the magnetic shields are provided separately in the vertical direction of the inner wall surface of the tank. Therefore, the concentration of the leakage magnetic flux in the separated portion of the magnetic shield is naturally a matter of concern. Here, FIG. 12 shows an incident magnetic flux distribution on the tank inner wall in the vertical direction of the tank inner wall. In the figure, 9 is the amount of incident magnetic flux, 10 is the wall surface of the tank 4, and 11 is the leakage magnetic flux distribution. As is clear from the leakage flux distribution 11, the incident magnetic flux becomes maximum at the portion facing the end of the winding, and the amount of incident magnetic flux at the portion facing the central portion in the vertical direction of the inner wall surface of the tank becomes extremely small. Thus, since the incident magnetic flux is small in the central portion of the tank, it is not necessary to attach the magnetic shield only to this portion. Therefore, due to the combination of the canceling action of the incident magnetic flux for the three phases and the action due to the leak magnetic flux distribution, the leak magnetic flux can be effectively converged even with the magnetic shields separated in the vertical direction of the inner wall surface of the tank. Further, as in the case of the three-phase transformer according to claim 2, when a through hole is provided in the center portion in the height direction of the tank wall surface and the high voltage lead is pulled out from the through hole, as in the three-phase transformer according to claim 3. In the case where the tank is divided horizontally, even if a separate magnetic shield is provided avoiding the through hole and the tank dividing part, leakage magnetic flux will not be concentrated on the inner wall of the tank for the above reason. , Local overheating of the tank is avoided.

[0013]

Embodiments of the three-phase transformer according to the present invention will be described below in detail with reference to the accompanying drawings. 1 to 12, the same parts are designated by the same reference numerals. (1) First Embodiment A first embodiment shown in FIG. 1 is a sectional view showing a magnetic shield mounting structure in a three-phase transformer according to claim 2 of the present invention, and FIG. 2 is a plan view thereof. It is a thing. In FIG. 1, a tank 4 accommodates a tripod core 1 in which a pair of low-voltage windings 2 and high-voltage windings 3 are wound around each main landing gear, and is installed in the center of the tank wall facing the windings for three phases. Has a through hole 8 penetrating the tank 4. High voltage lead 7 from winding is through hole 8
From the tank 4 to the outside of the tank 4. In addition, the magnetic shield 5 made of a material that facilitates the passage of magnetic flux, such as a grain-oriented silicon steel plate, avoids the high voltage lead 7 and the through hole 8 and avoids the axis of the length between the ends of the low voltage winding 2 and the high voltage winding 3. While having a length, their axial directions are separated in the winding arrangement direction and in the vertical direction of the inner wall surface of the tank, and are arranged in parallel.

When a load is connected to the three-phase transformer having the above structure, a leakage magnetic flux is generated between the low voltage winding 1 and the high voltage winding 2 and strays in a portion other than the tripod core 1. Tank 4
Leakage magnetic flux straying inside the tank flows into the magnetic shield 5 having a higher magnetic permeability than the tank 4. In the case of a three-phase transformer, it is well known that these three magnetic fluxes that are incident at the same high level have the same magnitude, and the magnetic fluxes in the magnetic shield combine the incident magnetic fluxes for three phases that are 120 degrees out of phase. By doing so, they cancel each other in a vector manner. In the present embodiment, the magnetic shield 5 is provided separately in the vertical direction on the inner wall surface of the tank, but it is possible to avoid partial overheating on the inner wall surface of the tank for the above reason.

Further, the magnetic shield 5 in the present embodiment.
Are attached only to the upper half and the lower half of the inner wall of the tank 4 excluding the through holes 8 where the amount of magnetic flux is large. However, since the through hole 8 provided in the inner wall of the tank 4 is provided at a position facing the central portion in the vertical direction of the inner wall surface of the tank, the amount of incident magnetic flux is small. Further, the magnetic shield 5 has a length corresponding to the winding end portions for three phases and is provided in the horizontal direction. Therefore, the problematic leakage flux is sufficiently converged, and local overheating of the inner wall of the tank 4 facing the non-installed portion of the magnetic shield 5 is not caused.

As described above, in the three-phase transformer of the present embodiment, it is possible to provide a practical transformer with a low loss and a simple structure that does not obstruct the through hole when attaching the magnetic shield.

(2) Second Embodiment A second embodiment shown in FIG. 3 is a sectional view showing a magnetic shield mounting structure in a three-phase transformer corresponding to claim 3 of the present invention, and FIG. 4 is a plan view thereof. The figure is shown. In FIG. 3, a tank 4 is connected by split portions 6a and 6b, and accommodates a tripod core 1 in which a pair of low-voltage winding 2 and high-voltage winding 3 are wound around each main leg. In the portion of the inner wall of the tank 4 facing the winding, the dividing portion 6 corresponding to the joint of the tank 4
The magnetic shield 5 is attached to a portion avoiding a and 6b.

In the three-phase transformer of this embodiment having such a configuration, the magnetic fluxes straying inside the tank 4 cancel each other in three vectors in the magnetic shield 5 in the same manner as in the first embodiment. Therefore, local overheating of the tank facing the divided portions 6a and 6b corresponding to the joint of the tank 4 does not occur. Therefore, unlike the conventional three-phase transformer, it is possible to provide a three-phase transformer having a low loss and a simple structure without continuously attaching a magnetic shield in the height direction of the winding.

(3) Other Embodiments The present invention is not limited to the above embodiments, and the materials and shapes of the members used in each configuration can be changed as appropriate. For example, the through holes may be located in the inner wall of the tank at positions corresponding to the central portion in the vertical direction of the inner wall surface of the tank, and the number and position of the through holes do not matter. Therefore, it is possible to provide through holes on both wall surfaces of the tank.
Further, even when the tank has a structure that can be divided into a plurality of parts in the horizontal direction, it is possible to obtain the same effect as above by attaching the three-phase magnetic shields on both sides of the joint. Further, the same applies to a tank having the structures of claims 3 and 4.

[0020]

As described above, according to the present invention, a three-phase transformer in which magnetic shields are vertically arranged in parallel in the inner wall surface of a tank, for example, a high voltage lead is pulled out from a through hole provided in the tank. Even in a three-phase transformer having a horizontally divided tank, the leakage flux can be reliably converged by the magnetic shield to avoid the local temperature rise of the tank, and the structure is low loss and practical. It is possible to provide a simple three-phase transformer.

[Brief description of drawings]

FIG. 1 is a sectional view of a magnetic shield portion of a three-phase transformer according to a first embodiment of the present invention.

FIG. 2 is a plan view of a magnetic shield portion of the three-phase transformer of the first embodiment of the present invention.

FIG. 3 is a sectional view of a magnetic shield portion of a three-phase transformer according to a second embodiment of the present invention.

FIG. 4 is a plan view of a magnetic shield portion of a three-phase transformer according to a second embodiment of the present invention.

FIG. 5 is a leakage flux diagram of a general transformer cross section without a magnetic shield.

FIG. 6 is a sectional view showing an example of a magnetic shield mounting structure in a conventional three-phase transformer.

FIG. 7 is a plan view of FIG.

FIG. 8 is a sectional view of a magnetic shield mounting structure in a transformer in which a conventional three-phase transformer tank is divided.

9 is a plan view of FIG.

FIG. 10 is a cross-sectional view of a magnetic shield mounting structure in a conventional three-phase transformer having a through hole for leading out a high voltage lead.

11 is a plan view of FIG.

FIG. 12 is a leakage magnetic flux distribution map of a tank wall of a general transformer having no magnetic shield.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Tripod core 2 ... Low voltage winding 3 ... High voltage winding 4 ... Tank 5 ... Magnetic shield 6a, 6b ... Dividing part 7 ... High voltage lead 8 ... Through hole 9 ... Incident magnetic flux amount 10 ... Tank wall surface 11 ... Leakage magnetic flux distribution

Claims (3)

[Claims] 1. A three-phase transformer comprising windings wound around the outer circumference of a plurality of iron core legs arranged in a tank, wherein a shaft extending in a direction in which the plurality of windings are arranged. A plurality of magnetic shield plates each having a length and an axial length of at least both ends of a winding located between the end portions of the winding, A three-phase transformer, characterized in that the three-phase transformer is placed in parallel with being separated in the vertical direction of the inner wall surface of the tank. 2. The transformer tank is provided with a through hole for pulling out a high voltage lead from a winding in a central portion thereof, and the plurality of magnetic shields are separately arranged in accordance with the through hole portion. The three-phase transformer according to claim 1, which is characterized in that. 3. The transformer tank has a dividing portion, and the tank is divided horizontally in the dividing portion,
The three-phase transformer according to claim 1, wherein the magnetic shield plate is not arranged on the inner wall surface of the tank facing the divided portion of the tank.