JPS63204605A - Foil-wound transformer - Google Patents

Abstract

PURPOSE:To contrive to enhance the reliability and to miniaturize the title transformer, by a method wherein the part of an insulating cylinder positioned on a spacer and a part of a supporting insulator are notched, the wedge part to be formed on the end part of a shield is removed, and the degree of concentration of electric field of the part where a spacer is positioned is made equal to that of the part having no spacer. CONSTITUTION:The part of an end part supporting insulator 31 corresponding to an insulating spacer 14 and the part 33 of an insulating cylinder 30 are notched, and gas empty space is formed on the end part side of the shield 20 on the insulating spacer 14. Said notched parts are formed in the size of d2 making the relation of d2>=d1 when the insulating spacer 14 is formed in the width of d1, and the relation of d3>=R is formed in the notch of the insulating cylinder 30 when the radius of the shield 20 is set at R. As a result, a wedge-shaped microscopic gap is not formed at the end part of the shield 20, the degree of concentration of electric field is lowered on that part, and a foil-wound transformer having excellent withstand voltage can be obtained.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a foil-wound transformer formed by overlapping and winding a metal sheet and an insulating sheet on an insulating cylinder, and particularly relates to a foil-wound transformer formed by overlapping and winding a metal sheet and an insulating sheet on an insulating cylinder. This invention relates to a foil-wound transformer with an improved shield attached to it.

(Prior art) Foil-wound transformers have a good winding space factor and can be made smaller and lighter, and have already been put into practical use as small-capacity transformers with relatively low voltages of several KV or several hundred KVA. has been done.

Figure 3 shows a separate foil-wound transformer in which cooling and insulation are separated. In FIG. 3, the winding is constructed by attaching an insulating tube 17 concentrically to the iron core 1, and placing a metal sheet 2 on top of the insulating tube 17.
A high-voltage winding 5 and a low-voltage winding 4 are constructed by overlapping and winding an insulating sheet 3.

The heat inside the winding is then transferred to a cooling duct 6 placed inside the winding.
It is cooled by flowing refrigerant inside. The low and high voltage windings 4 and 5 are insulated and supported from a grounding object 15 by an insulating spacer 14. The insulating spacers 14 are distributed and attached around the winding.

Figure 4 shows details of the main parts of the winding. Note that the same parts as in FIG. 3 are denoted by the same reference numerals, and the explanation thereof will be omitted. In FIG. 4, 2o is a shield attached to the ends of the windings, thereby relaxing the electric field near the ends of the low and high voltage windings 4.5. The shield 20 is held by an end support insulator 21 and an insulator 22. In addition,
Of course.

The shield 20 is coated with an insulation coating. The conventional foil-wound transformer constructed in this manner has the following drawbacks.

That is, electrical breakdown in gas insulated equipment is said to be of the electric field type, and breakdown occurs from the part where the electric field is severe. In the conventional configuration shown in FIG. 4, the ends of the shield 20 are naturally severe, especially between the shield 20 and the end support insulator 2.
Part A, which is the wedge part formed between the gas M
Since the ratio t is smaller than that of the surrounding insulator, the electric field in the wedge portion A is generated. As a countermeasure to this, a method has been taken to alleviate the electric field by increasing the curvature of the shield zO. This results in dielectric breakdown during the voltage test between the lines.

In order to avoid this, the gap length n must be made longer, which increases the size of the transformer and increases the electric field concentration at the gap part where an expensive transformer is formed and the electric field concentration at the end of the shield 20. Among them, the part where the insulating spacer 14 is present is particularly large. The reason is that the insulating spacer is made of a material with high mechanical strength, such as epoxy. However, because the dielectric constant of epoxy is large, the equipotential surface is concentrated on the insulating cylinder 17 side where the dielectric constant is small, for example between the gaps Ω.According to calculations by the inventors, the shielding in the area without the insulating spacer 14 The stress at the 20 end is reduced to about 75%. Furthermore, in the wedge portion A, the shield 20 is sometimes covered with an insulating coating, so the shape thereof is complicated, and there is a drawback that electric field concentration tends to occur. In particular, gas insulated equipment has the disadvantage that destruction occurs due to minute gas gaps.

The present invention has been made to eliminate the above-mentioned drawbacks.
The purpose is to eliminate the wedge portion that occurs at the shield end of the spacer part that supports the first winding, and to make the electric field concentration in that part the same as in the part without the spacer, creating a highly reliable and compact gas-insulated foil-wound transformer. It provides equipment.

[Structure of the invention]

(Means and effects for solving the problems) In the present invention,
A portion of the insulating tube and supporting insulator located in the spacer is cut out to eliminate the wedge portion formed at the end of the shield, thereby reducing the electric field concentration portion formed at the end of the shield.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

An embodiment of the present invention is shown in FIGS. 1 and 2.

Components that are the same as those in the prior art are denoted by the same reference numerals, and their description will be omitted. In FIG. 2, the winding portion of the high-voltage winding is not shown.5 In FIG. 1 and FIG. A part 33 of the insulating cylinder 30 is cut out.

In the insulating spacer 14 portion, a gas space is formed on the end side of the shield 20. In addition, the notch portion is located at the insulating spacer 1 as shown in FIGS. 1 and 2.
When the width of 4 is d, cut out with the dimension of d2, at this time d
, ≧d□.・Furthermore, in the notch of the insulating cylinder 30, when the radius of the shield 20 is R,
d,) The relationship between H holds true.

In one embodiment of the present invention configured in this way, the following effects are produced.

In the present invention, the insulating cylinder 30 and the end support insulator 31
The size of the spark when the notch is located on the spacer part is d, > R, d, ≧d.

The end of the shield 20 is notched due to the following.

Wedge-shaped minute gaps cannot be formed. Therefore, the electric field is less concentrated in that part, and a foil-wound transformer with excellent withstand voltage can be obtained. Note that since the cutout portion is only the spacer portion, the shield 20 is supported by the uncut insulating cylinder and the end support insulator as in the conventional case, so this does not pose a problem.

As mentioned above, since the wedge-shaped gap is eliminated, electric field concentration does not occur, and therefore, there is no need to increase the size of the shield zO.

Since the electric field at the end of the shield is relaxed, the two dimensions of insulation distance between windings can be reduced compared to conventional models.

A small and highly reliable foil-wound transformer can be created.

Also, since the shield end is completely spaced by the notch, even if the shield is covered.

Destruction from that part can be prevented. In one embodiment of the present invention, both the end support insulator and the insulating tube are cut out, but for example, if only the end support insulator is cut out, the tip of the shield becomes a gas space. Therefore, effects similar to those described above are produced.

〔Effect of the invention〕

As described above, in one aspect of the present invention, there is no minute wedge portion at the tip of the shield where electric field concentration occurs, and a foil-wound transformer that is insulatively stable, highly reliable, and moreover compact can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of the present invention, FIG. 2 is a perspective view thereof, FIG. 3 is a sectional view showing the winding part of a conventional transformer, and FIG. 4 is the main part of FIG. 3. FIG. 2... Metal sheet 3... Insulating sheet 4...
Low voltage winding 5...High voltage winding 14...Insulating spacer 15...Grounding object 17...Insulating cylinder
20... Shield 21... End support insulator 22.
... Insulator 30 ... Insulator cylinder 31 ... End support insulator 33 ... Notch part Agent Patent attorney Norihiro Ken Yudo Hirofumi Mitsumata Figure 1 Figure 2 Figure 3/,,5 Figure 4

Claims (2)

[Claims] (1) In a device in which a foil winding formed by alternately stacking metal sheets and insulating sheets and winding them around an insulating cylinder is supported by an insulating spacer, and a shield is attached to the insulating cylinder, the shield is located in the spacer portion and the shield A foil-wound transformer characterized by having a part of the insulating cylinder in contact with the casing cut out. (2) The foil-wound transformer according to claim 1, characterized in that at least one of the insulating cylinder and the end pawl in contact with the shield is cut out.