JPS63289804A - Foil wound transformer - Google Patents

Abstract

PURPOSE:To obtain a small-sized and inexpensive transformer having high quality and high performance, by mounting an electronic shield on the inner wall of a tank for decreasing eddy current loss occurring in the tank and windings and for pre venting local heating. CONSTITUTION:A transformer body comprising an iron core 1 on which a metallic sheet 2 and an insulating sheet 3 laid thereon are wound is received in a tank 8 filled with an insulating medium. An electromagnetic shield 14 formed of a highly conductive metal such as aluminium or copper is mounted on the inner wall of the tank 8. Since any leakage magnetic flux 12 is repulsed by the electromagnetic shield 14, an amount of magnetic flux entering into the tank 8 is decreased. Also on the side the windings, particularly in the external winding 5, leakage magnetic flux is hardly leaked out of the winding and, therefore, less current will flow in the direction for cancelling radial leakage of the magnetic flux. Therefore, eddy current loss occurring in the tank and the windings can be reduced. Since local heating is prevented, a number of cooling panels can be decreased. In this manner, it is possible to obtain a small- sized and economical transformer having high quality and high performance.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention is directed to a transformer body formed by stacking metal sheets and insulating sheets and winding them around an iron core in a tank filled with an insulating medium. This invention relates to a foil-wound transformer housed in a foil-wound transformer.

(Prior art) Sheet-shaped windings conventionally used in foil-wound transformers are
Excellent winding space factor, good potential distribution,
Although it has been widely used because it is easy to manufacture, it has been limited to relatively small capacity transformers.

However, in order to realize higher-voltage, larger-capacity transformers, it is essential to further improve the cooling efficiency of the windings and provide the windings with high insulation ability. It has been considered to incorporate a cooling panel through which a refrigerant flows inside, so that the heat generated from the windings can be directly cooled.

Examples of this type of transformer include JP-A-54-16861.
No. 3 is known. In this transformer, for example, as shown in FIG. 3, a metal sheet 2 and an insulating sheet 3 are layered and wound around an iron core 1 to form a sheet-like winding, which is housed in a tank 8. .

This sheet-like winding consists of an inner winding 4 and an outer winding 5 that are arranged concentrically, and an annular cooling panel 6 is built in each of these windings.

The cooling panel 6 is made up of two metal plates stacked one on top of the other with a narrow gap for the coolant to flow, and the periphery of the two metal plates is sealed by welding or the like. Cooling is performed by constantly flowing a refrigerant such as Freon R-113 or Fluorinert FC-75 into the gap between the cooling panels 6 using a pump 7, and allowing the refrigerant to remove the heat generated within the sheet windings. The refrigerant that has absorbed the heat is sent out to the outside of the winding, cooled in a cooler 9 provided outside the tank 8, and sent into the cooling panel again. Note that the refrigerant is once collected in the liquid pipe 10 before being sent to the cooling panel 6, but since this liquid collecting pipe 10 maintains the same ground potential as the tank 8, etc., it is at the same potential as the metal sheet 2. Connection to the cooling panel 6 having a potential is made via an insulating pipe 11. The cooling panel 6 is in contact with the metal sheet 2 or the insulating sheet 3 in order to cool the metal sheet 2 by thermal conduction, and since the cooling panel 6 is wrapped in the winding, the cooling panel 6 is also in contact with the metal sheet 2 or the insulating sheet 3. Approximately the same potential is applied, and insulation between the metal sheet 2 and the cooling panel 6 and the outside is made using, for example, sulfur hexafluoride (S F6) sealed in the tank 8.
) and other insulating gases.

The foil-wound transformer described above is called a separate foil-wound transformer because the circulation circuit through which the refrigerant for cooling flows and the insulating gas are completely separated. Compared to transformers that use

By the way, in the separate foil-wound transformer having the above configuration, as the capacity of the transformer increases, the amount of leakage magnetic flux from the windings 4 and 5 increases, and large eddy currents occur in the windings 4 and 5 themselves and the tank 8. This causes loss and local heating. The occurrence of eddy current loss due to this leakage magnetic flux will be explained with reference to FIG. As shown in FIG. 4, the leakage magnetic flux 12 generated from the winding 4.5 forms a loop from the winding through the insulating space 13 and the tank 8. As described above, when the leakage magnetic flux 12 enters the tank 8, since the tank 8 is made of metal such as mild steel, an eddy current flows in a direction that cancels the leakage magnetic flux 12, causing a loss.

On the other hand, eddy current loss also occurs in the metal sheet 2 that constitutes the winding. That is, the leakage magnetic flux 12 tries to create a loop across the metal sheet 2 with the shortest magnetic path (minimum energy), but since the vertical width of the metal sheet 2 is large, the leakage magnetic flux 12 crosses the metal sheet 2. An eddy current flows in a direction that cancels out the leakage in the radial direction of 12. This eddy current is particularly concentrated at the upper and lower ends of the metal sheet 2 and causes a large loss.

This phenomenon is more noticeable in a foil-wound transformer using a sheet-shaped conductor because the width of the conductor is wider than in a transformer using a conventional rectangular conductor.

The losses due to eddy currents as described above are caused by the tank 8, winding 4,
Not only is there a risk of local heating of the windings 4 and 5, but the number of cooling panels 6 for cooling the windings 4 and 5 is increased, leading to increased costs and larger windings.

(Problems to be Solved by the Invention) As described above, in conventional foil-wound transformers, the amount of leakage magnetic flux from the windings is large, which causes large a current loss in the tank and windings, causing local There was a problem in that it caused heating.

The present invention has been made in consideration of the shortcomings of the prior art, and its purpose is to reduce eddy current loss occurring in the windings and windings, and to prevent local heating. Our objective is to provide a high-quality, high-performance, compact, and inexpensive @-winding transformer.

[Configuration of the Invention (Means for Solving Problems) The foil-wound transformer of the present invention is characterized in that an electromagnetic shield is attached to the inner wall of the tank.

(Function) In the foil-wound transformer of the present invention, the electromagnetic shield attached to the inner wall of the tank repels the winding leakage magnetic flux over a distance of 1 m, reducing the eddy current loss generated in the tank, and at the same time reducing the eddy current loss generated in the winding. Eddy current loss can be reduced.

(Example) Hereinafter, an example of the present invention will be specifically described based on FIGS. 1 and 2. Note that the same members as those of the conventional type shown in FIGS. 3 to 4 are denoted by the same reference numerals, and explanations thereof will be omitted.

*Configuration of the Embodiment* In the present invention, as shown in FIG. 1, a transformer body consisting of a metal sheet 2 and an insulating sheet 3 wound around an iron core 1 is placed inside a tank 8 filled with an insulating medium. It is stored in. An electromagnetic shield 14 made of a highly conductive metal such as aluminum or copper is attached to the inner wall of the tank 8.

Effect of this embodiment* In the foil-wound transformer of this embodiment having such a configuration, the leakage magnetic flux 12 is repelled by the electromagnetic shield 14 attached to the inner wall of the tank 8, as shown in FIG. Therefore, the magnetic flux incident on the tank 8 is reduced compared to the conventional method, and the magnetic flux entering the tank 8 is
The eddy current loss generated in the process is significantly reduced. This prevents local heating of the tank. Moreover, when the leakage magnetic flux 12 is repelled by the electromagnetic shield 14 in this way, the leakage magnetic flux becomes difficult to leak to the outside of the winding in the outer winding 5 on the winding side as well. As a result, the current flowing in the direction to cancel the leakage of leakage magnetic flux in the radial direction is reduced, the generated eddy current loss is reduced, and local heating of the winding is prevented.

In addition, as a result of preventing local heating in the tank 8 and the windings 4 and 5, the number of cooling panels 6 built into the windings 4.5 can be reduced, which has the advantage of downsizing the device and reducing costs. be.

[Effects of the Invention] As described above, according to the present invention, *r is applied to the inner wall of the tank.
The simple configuration of attaching an a-shield can reduce eddy current loss generated in the tank and windings, reducing local heating. This also makes it possible to reduce the number of cooling panels, resulting in high quality, high performance, A compact and economically superior foil-wound transformer can be provided.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing an embodiment of a foil-wound transformer according to the present invention, Fig. 2 is an enlarged sectional view of essential parts showing leakage flux generated in the foil-wound transformer of the same embodiment, and Fig. 3 is a conventional one. FIG. 4 is an enlarged sectional view of a main part showing leakage flux generated in the foil-wound transformer of FIG. 3. FIG. DESCRIPTION OF SYMBOLS 1... Iron core, 2... Metal sheet, 3... Insulating sheet, 4... Inner winding, 5... Outer winding, 8... Tank, 12... Leakage magnetic flux, 14 ...Electromagnetic shield.

Claims (1)

[Claims] In a foil-wound transformer in which a transformer body consisting of a metal sheet and an insulating sheet wound over an iron core is housed in a tank filled with an insulating medium, an electromagnetic shield is attached to the inner wall of the tank. A foil-wound transformer featuring: