JPS60241207A - Foil-wound transformer - Google Patents

Abstract

PURPOSE:To relax the concentration of an electric field generated at the end section of a high-tension winding by mounting a shield, a sectional form thereof takes a shape close to a hanging bell shape, at an end section on the outermost side of the high-tension winding and bringing the potential of the shield to the same potential as the high-tension winding. CONSTITUTION:A shield 21, a sectional form thereof takes a shape close to a hanging bell shape, is disposed at the end section of a high-tension winding 5. The upper section of the shield 21 takes the arcuate shape of a curvature radius R1, the lower side thereof consists of a rectilinear section and the arcuate sections of curvature radii R2, R3, and the relationship of R1>(R2+R3) holds regarding the curvature radii R1, R2, R3. With the shield 21, the outside of a shield core 22 in which a potential wire is arranged on the outer circumference of an insulator is insulated and coated with the insulator 23. The thickness of the insulating coating is thinned as T2 on the winding 5 side and thickened as T1 on the tank 6 side, and the potential of the core 22 is made the same as that of the winding 5.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a foil-wound transformer having a foil-like winding formed by overlapping and winding a metal sheet and an insulating sheet. This relates to a foil-wrapped transformer with an improved shield attached to the.

[Technical Background of the Invention] Foil-wound transformers have a good winding space factor and are characterized by being compact and lightweight, and have already been put into practical use as small capacity transformers with relatively low voltage. Recently, in view of its excellent advantages,
Higher voltage, larger capacity (e.g. 257KV, 300MV
Research is underway to expand its application to class A) transformers.

An example of such a large-capacity foil-wound transformer that has been proposed in the past is shown in FIG.

A low-voltage winding 4 and a high-voltage winding 5 are constituted by a foil-like winding formed by overlapping and winding a metal sheet 2 and an insulating sheet 3 around the legs of an iron core 1. The contents of the transformer, such as the iron core 1 and the windings 4.5, are housed in a tank 6. This tank 6 is filled with an insulating medium such as SF6 gas or insulating oil to insulate each part of the windings. is ensured. Also, winding 4
, 5, insulation between the turns of the metal sheet 2 is achieved by making the width of the insulation sheet 3 appropriately wider than that of the metal sheet 2.

Furthermore, since the winding structure of the high voltage winding 5 is one in which the thin metal sheet 2 and the insulating sheet 3 are wound one on top of the other, the electric field at the end of the high voltage winding facing the tank 6 becomes extremely severe. For that reason,
Usually, a shield 7 for mitigating the electric field is attached to the end of the high voltage winding.

[Problems in the background art] By the way, the foil-wound transformer as described above is made by using a thin metal sheet 2.
By overlapping and winding the insulating sheet 3,
Since the low-voltage winding 4 and the high-voltage winding 5 are configured, the winding space factor within the core window is increased, but there are the following problems.

That is, as shown in the enlarged view of FIG. 2, the shield 7 attached to the end of the high voltage winding 5 is usually made of a metal cylinder and is connected to the outermost metal sheet of the high voltage winding 5. There is.

However, since the shield 7 is attached to the outermost side of the high voltage winding 5, the insulation path 111 between the high voltage winding 5 and the tank 6
1D is the diameter D of the shield 7 at the installation location of the shield 7
The distance becomes shorter by 2 minutes, resulting in a distance of Dl, and the dielectric strength decreases. Therefore, if the shield 7 is made larger in order to increase the dielectric strength between the high voltage winding 5, the tank 6, and the grounding objects 8 disposed at the upper and lower ends of the winding, the space for winding the winding will decrease accordingly. However, this had the disadvantage of reducing the winding space factor, resulting in a wasteful foil-wound transformer. In addition, although electric field concentration occurs at the end of the shield 7, the insulation performance of the SF6 gas filled for insulation between the high voltage winding 5 and the tank 6 is electric field dependent, so the end of the shield Another drawback is that dielectric breakdown occurs at areas where electric fields are concentrated.

In order to sufficiently reduce the electric field at the end of the shield 7, it is necessary to increase the diameter of the shield 7 and reduce some of the corners where electric field concentration tends to occur. Since the insulation distance of the tank 6 becomes short, it becomes necessary to expand the tank 6, which increases the manufacturing cost and also requires an expansion of the space for installing the foil-wound transformer.

Furthermore, in order to reduce the electric field at the end of the shield 7, there is an idea to cover the circumference of the shield 7 with an insulating material 9 to make it possible to make the shield smaller. The disadvantage of using insulation coatings is that it requires a lot of manufacturing man-hours and increases costs1.On the other hand, foil-wound transformers in which an insulation barrier 10 is attached to the outside of the high-voltage winding 5 have also been used. . This insulating barrier 10 is bound and fixed to the high voltage winding 5 via a spacer for forming a draw 11. However, transformers have a drying process, and during that drying process, the insulation barrier 1
0 expands and contracts, causing the internal spacer to detach from the winding 5 and fall, and as a result, the lottery 11 becomes uneven, causing problems such as partial discharge and dielectric breakdown occurring at that location.

[Object of the Invention] The present invention has been made in view of the above points, and its purpose is to provide high dielectric strength even at the end of the winding where the shield and tank are close to each other, without expanding the tank. Our goal is to provide compact and highly reliable foil-wound transformers.

[Summary of the Invention] The foil-wound transformer of the present invention has a shield having a cross-sectional shape close to a bell shape attached to the outermost end of the high-voltage winding.
By making the potential the same as that of the high-voltage winding, concentration of the electric field generated at the end of the winding is alleviated.

[Embodiments of the invention] Hereinafter, one embodiment of the present invention will be described with reference to FIG.

Incidentally, the same parts as those of the conventional type shown in FIGS. 1 and 2 are given the same reference numerals, and the explanation thereof will be omitted.

In FIG. 3, a shield 21 having a cross-sectional shape close to a bell shape is disposed at the end of the high voltage winding 5. As shown in FIG. The upper part of this shield 21 has an arc shape with a radius of curvature R1,
The lower side consists of a straight portion and a circular arc portion with radii of curvature R2 and R3, and the relationship between these radii of curvature R+, R2, and R3 is such that R+>(R2+R3).

In addition, the shield 21 has potential wires arranged around the outer periphery of the insulator.
An insulating coating is provided on the outside of the C shield core 22 with an insulating material 23. The thickness of this insulation coating is the high voltage winding 5
Thin < (T2) on the side, thick <<T+) on the tank 6 side
It is as it is. The potential of the shield core 22 is the same as the potential of the high voltage winding 5.

In the foil-wound transformer of the present invention configured in this way, the stress of the shield core 22 is concentrated on the upper part of the shield 21, but it is possible to increase the thickness of the insulation coating on the upper part of the shield 21 and on the tank side. Therefore, the stress on the shield surface is alleviated by the insulator 23, and a high withstand voltage can be obtained. Furthermore, since the shield 21 and the high voltage winding 5 of the present invention are at the same potential, the shield 21 and the high voltage winding 5
There is no added stress between them. Therefore, shield core 2
The thickness of the insulator 23 disposed on the outside of the high voltage winding 5
Even if it is made thinner on the side, dielectric breakdown does not occur, and the tank 6 can be made smaller accordingly. Furthermore, since the distance between the shield 21 and the high voltage winding 5 is shorter than in the conventional type, electric field concentration can be alleviated. Furthermore, since the lower part of the shield 21 has a straight part, the insulation barrier 10 can be supported by this straight part, and the internal spacer can be stored and removed from the winding 5 during the drying process of the transformer. Even if it falls, it can be caught by the straight portion of the shield 21, so that partial discharge or dielectric breakdown will not occur.

[Effects of the Invention] As described above, the present invention has the effect of providing a small, highly reliable foil-wound transformer with excellent dielectric strength at the winding ends.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing the structure of a conventional foil-wound transformer, Fig. 2 is an enlarged sectional view of the main part of Fig. 1, and Fig. 3 is a main part of an embodiment of the foil-wound transformer of the present invention. It is an enlarged sectional view shown. DESCRIPTION OF SYMBOLS 1... Leg of iron core, 2... Metal sheet, 3... Insulating sheet, 4... Low voltage winding, 5... High voltage winding, 6...
...Tank, 7...Shield, 8...Grounding object, 9.
...Insulator, 1o...Insulating barrier, 11...Lottery,
21... Shield, 22... Shield core, 23...
·Insulator. 7311 Agent Patent Attorney Last week Tentai (1 other person) No.
1 Figure 11F2

Claims (1)

[Claims] In a foil-wound transformer, in which a foil-shaped winding made by overlapping metal sheets and insulating sheets is housed in a tank together with an insulating medium, the outermost end of the high-voltage winding has a bell-shaped cross section. 1. A foil-wound transformer characterized in that a shield having a shape similar to the above is provided, and an insulating material is formed on the surface of the shield so that it is thicker on the tank side and thinner on the high-voltage winding side.