JP2947844B2 - Transformer winding - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transformer winding, and more particularly, to a transformer winding having an improved insulating structure between a winding surface and an adjacent disk coil in the winding. About.

[Conventional technology]

Conventionally, kraft paper has been mainly used as an insulating coating for electric wires of transformer windings, and press boards have been mainly used as insulating cylinders, linear spacers, and spacers between coils. It is a composite insulation of insulating paper and mineral oil. By the way, comparing the relative permittivity of oil-impregnated paper obtained by subjecting these insulating papers to oil impregnation and the relative permittivity of mineral oil,
The relative permittivity of mineral oil is about 2.2, while the relative permittivity of oil-impregnated paper is about 3.5 to 4.7, and that of oil-impregnated paper is about 1.5 to 2 times larger. Therefore, a higher electric field is applied to the mineral oil.
On the other hand, mineral oil has lower insulation strength than oil-immersed paper,
The insulation strength of the composite insulation system of the winding is determined by the insulation strength of the mineral oil. In particular, where the wire and the linear spacer touch,
It is known that a wedge-shaped oil gap between an electric wire and an inter-coil spacer and a wedge-shaped oil gap between adjacent electric wires have a high electric field and cause a dielectric breakdown. For example, JP-A-62-14
As described in No. 7710, the dielectric constant of the insulating coating of the electric wire, the linear spacer and the spacer between the coils is 1.
By using a material having a value of three times or less, the electric field applied to the wedge-shaped oil gap is relaxed to improve the dielectric strength of the transformer winding, and Japanese Unexamined Utility Model Publication No. 59-93116 discloses As described, a band-shaped, soft or semi-rigid paper made of cotton fiber is placed between the disc coil and the inter-coil spacer and the linear spacer, and the paper is compressed. Some wedge-shaped oil gaps have been eliminated to improve the dielectric strength of transformer windings.

[Problems to be solved by the invention]

Among the above-mentioned prior arts, the former can certainly reduce the electric field of the wedge-shaped oil gap and improve the dielectric strength. However, since the wedge-shaped oil gap remains,
Although the dielectric strength is improved as compared with the prior art, the dielectric breakdown is caused by the wedge-shaped oil gap as before, and it is insufficient in terms of drastically improving the dielectric strength. On the other hand, the latter can eliminate wedge-shaped oil gaps if it can be manufactured exactly according to the dimensions, and can further improve the dielectric strength as compared with the former. However, since the band-shaped paper and the disc coil are not fixed to each other, they may shift due to drying shrinkage of the insulator during the insulation treatment, and wrinkles may occur because the paper does not shrink uniformly. A minute oil gap may occur between the disc coil and the band-shaped paper. that time,
Since the paper is made of cotton fiber and the dielectric constant is about 1.5 times larger than mineral oil, the electric field concentrates on the minute oil gap,
There is a problem in that dielectric breakdown occurs at a low voltage, and the intended effect of improving the dielectric strength cannot be stably obtained.

An object of the present invention is to eliminate wedge-shaped oil gaps between the disk coil and the linear spacer and between the disk coil and the spacer between the coils, and to reduce the electric field even if a minute oil gap is generated. An object of the present invention is to provide a transformer winding capable of stably improving the dielectric strength by preventing the rise of the transformer winding.

[Means for solving the problem]

In order to achieve the above object, the surface corresponding to the disk coil of the linear spacer and the inter-coil spacer is made of plastic having a low dielectric constant of 1.3 times or less the dielectric constant of the insulating oil, and has a porosity. Install a porous elastic insulating sheet of 50% or more and cover the part corresponding to the linear spacer on the disk coil side and the spacer between the coils, and fill the wedge-shaped oil gap with these elastic insulating sheets. It has been crushed and eliminated.

[Action]

The elastic insulating sheet on the surface of the linear spacer and the surface of the disk coil corresponding to the linear spacer has a porosity of 50% or more, so it is very soft, and is crushed by the force of winding the electric wire at the time of winding production. This eliminates the wedge-shaped oil gap between the linear spacer and the disk coil. In addition, the elastic insulating sheet on the surface of the inter-coil spacer and the surface of the disk coil corresponding to the inter-coil spacer is also crushed by the tightening load from the upper part of the winding after manufacturing the winding, and the inter-coil spacer and the disk coil Since the wedge-shaped oil gap between them is eliminated, the dielectric strength of the transformer winding can be improved.

Even if the disc coil and the linear spacer or the inter-coil spacer are displaced due to drying shrinkage of the insulator during the insulation treatment, the elastic insulating sheet on the disc coil surface is fixed to the disc coil. Oil gap does not occur on the surface of the disk coil where the electric field is high. The oil gap is located between the elastic insulating sheet on the surface of the linear spacer and the elastic insulating sheet on the surface of the disk coil, or the elastic insulating sheet on the surface of the spacer between the coils and the elastic insulating sheet on the surface of the disk coil. Occurs in between. This area is slightly away from the surface of the disk coil where the electric field is high, and the dielectric constant of the surrounding elastic insulating sheet is not much different from the dielectric constant of the insulating oil. Hateful. Further, since the plastic shrinks uniformly, there is no wrinkling like a paper and a minute oil gap is formed. Therefore, stable dielectric strength can be improved.

〔Example〕

 Hereinafter, an embodiment of the present invention will be described with reference to FIG.

A plurality of linear spacers 2 are arranged on the outer periphery of the insulating cylinder 1,
An elastic insulating sheet 3 slightly wider than the linear spacers 2 is bonded to the outer surface of each linear spacer 2. Then, an elastic insulating sheet 4 is provided on the outside, and an insulating coating 5 is placed thereon.
The coil 6 is wound a plurality of times while pressing the electric wire 6 subjected to the above process to form the disk coil 7. Thereafter, as shown by the arrow in FIG. 2, the elastic insulating sheet 4 is bent so as to enclose the disk coil 7, and the end is adhered to cover the disk coil. An inter-coil spacer 9 having an elastic insulating sheet 8 bonded to the upper and lower surfaces is disposed between the plurality of disk coils 7 formed as described above, a tightening load is applied from above, and the coil is immersed in mineral oil (not shown). The transformer winding 10 of the invention is configured. The width of the elastic insulating sheet 8 is slightly wider than the spacer 9 between the coils, and the elastic insulating sheet 4 is slightly wider than that.

FIG. 3 is an enlarged view of a portion corresponding to the disk coil 7 and the linear spacer 2 and the inter-coil spacer 9 of the transformer winding 10 according to the present invention. The elastic insulating sheets 3, 4, and 8 are crushed by the tightening pressure when the electric wire 6 is wound and the tightening load from above, and the elastic insulating sheets 3, 4, and 8 are brought into close contact with each other, and a wedge-shaped oil gap that is a weak point on insulation is eliminated. I have. The electric field of the wedge-shaped oil gap is about 1.5 to 2 times higher than the electric field of the other part of the disc coil 7. Therefore, according to the present invention, the dielectric strength of the transformer winding 10 is improved by about 1.5 to 2 times.

FIG. 4 shows a case where the disk coil 7, the linear spacer 2, and the inter-coil spacer 9 are displaced due to drying shrinkage or the like in the transformer wire winding 10 of the present invention. Since the disk coil 7 and the elastic insulating sheet 4 placed thereon are integrated, no oil gap occurs on the surface of the disk coil 7 where the electric field is high. Instead, an oil gap 11 is formed in a portion surrounded by the elastic insulating sheets 3, 4, and 8. However, since this part is far from the disk coil 7 of the high electric field, the electric field is originally weak, and the dielectric constant of the surrounding elastic insulating sheets 3, 4, 8 is not much different from the dielectric constant of the insulating oil. Is small, so the electric field is weak. For this reason, a stable effect of improving the dielectric strength can be obtained without forming an insulating coating.

As the insulating cylinder 1, the linear spacer 2, and the inter-coil spacer 9 of the transformer winding 10 of the present invention, a conventionally used press boat is preferable because of its high insulation strength and mechanical strength.

As the elastic insulating sheets 3, 4, and 8, low-permittivity plastics, such as fluorine resin, polyethylene, polyurethane, polypropylene, polymethylpentene, and polyethylene, are used. A porous body is preferable because it has a low dielectric constant and a small electric field concentration on the oil gap, and is flexible and can sufficiently fill the wedge-shaped oil gap. The relative dielectric constant of the plastic material is 2.
It is about 1 to 2.7, which is 1.3 times or less the relative permittivity of mineral oil. In addition, since it is made porous, the dielectric constant further decreases, and the dielectric constant after oil immersion is not much different from the dielectric constant of mineral oil. Further, among these, a porous body of polytetrafluoroethylene of a fluorine resin, for example, a Goatex or a microtex, or a porous body of polymethylpentene, has a relative dielectric constant of the material.
2.1 and smaller than the dielectric constant of mineral oil. Therefore, even if crushed, the dielectric constant is smaller than the dielectric constant of the mineral oil, and no electric field concentration occurs at the oil gap, which is very suitable for insulation.

The elastic insulating sheets 3, 4, and 8 are also used to effectively eliminate the wedge-shaped oil gap by half of the original thickness by the tightening force at the time of winding the electric wire 6 or the winding tightening load after manufacturing. Need to be crushed below. Compression by such a relatively small force is only possible if the holes in the elastic insulating sheets 3, 4, 8 are crushed, and in order to be able to crush less than half, the volume of the holes occupies The proportion, that is, the porosity (or porosity) needs to be 50% or more.

The holes are continuously connected inside the elastic insulating sheets 3, 4, 8. By the way, it is conventionally known that a streamer is generated and progresses as a precursor of dielectric breakdown, and the diameter of the streamer is about 10 μm. Therefore, when the diameter of the hole exceeds 10 μm, dielectric breakdown easily occurs through the hole. Therefore, the diameter of the holes needs to be 10 μm or less.

In addition to the above porous materials, various types of plastic fibers having a dielectric constant of 1.3 times or less that of mineral oil are formed into a felt or nonwoven fabric, for example, polyflon paper in which polytetrafluoroethylene fibers are formed into a nonwoven fabric, or various types of nonwoven fabrics. A sheet made by laminating a plurality of thin plastic films is also elastic like a porous body, and can be buried in an oil gap, so that it is suitable as a material for the elastic insulating sheets 3, 4, and 8.

 Hereinafter, another embodiment of the present invention will be described with reference to FIG.

The elastic insulating sheet 12 is also provided between the electric wires 6, and the electric wire 6 is wound while crushing the elastic insulating sheet 12 to form the disk coil 7.

Although the width of the disk coil 7 is slightly increased, the oil gap between the electric wires 6 can be eliminated, and the dielectric strength can be further improved.

 Hereinafter, another embodiment of the present invention will be described with reference to FIG.

The disk coil 7 is formed by covering the surface of the electric wire 6 with an elastic insulating sheet 13 in advance. Disc coil 7
, But the production time can be shortened.

Hereinafter, another embodiment of the present invention will be described with reference to FIGS. 7 and 8.

The surfaces of the linear spacer 2 and the inter-coil spacer 9 are wrapped and adhered with elastic insulating sheets 14 and 15. Although it takes a lot of man-hours, it can prevent the elastic insulating sheet from being turned up.

 Hereinafter, an application example of the present invention will be described with reference to FIG.

The entire outer peripheral surface of the insulating tube 1 is covered with an elastic insulating sheet 16, and the electric wire 6 is wound thereon to form the disk coil 7. The present invention can be applied to a type of transformer winding that does not use a linear spacer.

 Hereinafter, an application example of the present invention will be described with reference to FIG.

Normally, the end of the winding is insulated to reduce the electric field.
A shield ring 18 is provided. The shield ring 18 is covered with the elastic insulating sheet 19, and the elastic insulating sheet 21 is also adhered to the surface of the support insulator 20 corresponding to the shield ring 18. The wedge-shaped oil gap between the supporting insulator 20 and the linear spacer 2 is eliminated. It is possible to improve the dielectric strength of the winding end.

 Hereinafter, another application example of the present invention will be described with reference to FIG.

The U-shaped elastic insulating sheet 24 is adhered to the innermost electric wire 6 of the disk coil 7, and the thickness of a part of the inter-coil spacer 25 corresponding to the U-shaped elastic sheet 24 is reduced by cutting. The purpose is to eliminate the oil gap at the portion corresponding to the linear spacer 2 of the plate coil 7. It can be applied to the case where an electric field is applied only to the surface of the winding corresponding to the main insulation, such as a low-voltage winding, and an electric field is hardly applied between the disc coils.
Can be reduced.

〔The invention's effect〕

ADVANTAGE OF THE INVENTION According to this invention, the wedge-shaped oil gap which is a weak point on insulation can be eliminated and the dielectric strength of a transformer winding can be improved about 1.5 to 2 times. Thus, even if an oil gap occurs, an increase in the electric field can be prevented, and a stable effect of improving the dielectric strength can be obtained.

[Brief description of the drawings]

FIG. 1 is a partial perspective view of a transformer winding according to an embodiment of the present invention,
FIG. 2 is an explanatory diagram of application of an insulating sheet according to one embodiment of the present invention,
3 and 4 are explanatory views of the operation of one embodiment of the present invention, FIGS. 5 and 6 are cross-sectional views of a disk coil portion of another embodiment of the present invention, and FIG. FIG. 8 is a perspective view of a linear spacer of another embodiment of the present invention, FIG. 8 is a perspective view of an inter-coil spacer of another embodiment of the present invention, FIG. 9 is a partial cross-sectional view of a transformer winding of one application of the present invention, FIG. 10 is a partial sectional view of a winding end portion of one application example of the present invention, and FIG. 11 is a partial sectional view of a transformer winding of one application example of the present invention. 1 ... insulating cylinder, 2 ... linear spacer, 3, 4, 8 ... elastic elastic sheet, 6 ... electric wire, 7 ... disk coil, 9 ... spacer between coils, 12, 13, 14, 15, 15, 16 ... elastic insulating sheet, 18
…… Shield ring, 19,21,24 …… Elastic insulating sheet, 20
...... Support insulator.

Continuation of the front page (72) Inventor Hiroyuki Fujita 1-1-1, Kokubuncho, Hitachi City, Ibaraki Prefecture Inside the Kokubu Plant of Hitachi, Ltd. (56) References JP-A-46-7284 (JP, A) Akira Mikai 59-1111021 (JP, U) Fully open sho 59-93116 (JP, U) Fully open sho 56-114525 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01F 27/28 H01F 27/32 B32B 5/24

Claims (3)

(57) [Claims] A plurality of linear spacers are arranged on the outer periphery of an insulating tube, and a plurality of disk coils and inter-coil spacers each formed by winding an electric wire a plurality of times in a disk shape are alternately stacked on the outer side thereof. In a transformer winding formed by immersing the linear spacer in insulating oil, the surface of the linear spacer corresponding to the disk coil and the surface of the inter-coil spacer corresponding to the disk coil have a dielectric constant of plastic. In addition to disposing a porous elastic insulating sheet having a dielectric constant of 1.3 times or less and a porosity of 50% or more, a portion corresponding to the linear spacer and the inter-coil spacer of the disc coil is also provided. A transformer winding covered with the elastic insulating sheet. 2. The diameter of pores in said elastic insulating sheet is 10 μm.
2. The transformer winding according to claim 1, wherein the length is not more than m. 3. The transformer winding according to claim 1, wherein the elastic insulating sheet is formed of a porous body of polytetrafluoroethylene or a porous body of polymethylpentene.