JPH07254517A - Outdoor mold transformer - Google Patents

Abstract

(57) [Summary] [Purpose] To reduce the weight of outdoor molded transformers. [Structure] The contents of a molded transformer consisting of an iron core and windings are housed in a case, and the case is made of a synthetic resin in an outdoor molded transformer in which the molding resin is filled to a height to cover the contents and cured by heating. In this case, since the specific gravity of the synthetic resin is much smaller than that of the steel plate used as the metal case, the case is lightened. In addition, the inorganic filler is applied to the part of the molding resin made of a mixture of the inorganic filler particles and the epoxy resin, which is separated from the winding by a predetermined distance up to the height from the bottom surface of the case and has no problem in terms of insulation strength and heat conduction. By filling the hollow inorganic filler instead of the particles, the volume of the hollow portion is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an outdoor molded transformer which can be used outdoors by housing a molded transformer in a case.

[0002]

2. Description of the Related Art There are various types of molded transformers, such as those in which only the winding is resin-molded and those in which the iron core is integrally molded. Mold resin, which is a thermosetting resin used for molding, generally has problems of surface deterioration due to ultraviolet rays and deterioration of dielectric strength due to surface contamination due to moisture and dust. The conventional molded transformer is not used as it is.

Since the molded transformer has various features such as low noise, compact size, high reliability and maintenance-free, it is required to use the molded transformer outdoors. Like the container, it is housed in an iron case for outdoor use.
FIG. 2 is a side view of a conventional outdoor molded transformer, which is the same as that disclosed in Japanese Patent Laid-Open No. 5-166661 by the same applicant as the present invention except for a part. In this figure, the front wall of the metal case 1 in the figure is omitted and shown as a cross section, and the contents 20 of the outdoor molded transformer such as the iron core 2 and the winding 3 are shown. In addition, a right side is a cross-sectional view of the content 20 and a left side is a side view with a center line indicated by a dashed line as a boundary. In this figure, a metal case 1 which is mostly made of steel plate is composed of a box part 11, a lid part 12 and a pedestal 13,
The contents 20 composed of the iron core 2 and the winding wire 3 are housed therein and filled with a mold resin 5 as a mixture of granular silica sand 51 and epoxy resin 52. Epoxy resin 52 when completed
Is hardened, and the iron core 2, the winding 3, and the metal case 1 including the silica sand 51 are integrated.

Silica sand 51 as the inorganic filler particles of the mold resin 5 is charged from above to a height at which the iron core 2 is covered with the lid 12 removed. The epoxy resin 52 is injected from the injection port 8 provided near the bottom surface of the box 11. Epoxy resin 52
For the reason described below, a resin having good flexibility like rubber even after curing (for example, XN1019 / XN1124 manufactured by Nagase CIBA) is used.

A high voltage lead 36 is drawn from the high voltage winding 31 and connected to a high voltage bushing 41, and a low voltage lead 37 is drawn from the low voltage winding 32 and connected to a low voltage bushing 42. These bushings 41, 42 penetrate the case 1 and are drawn to the outside. High pressure bushing as shown
Both the low pressure bushing 41 and the low pressure bushing 42 are drawn out from the upper part of the side surface of the case 1 because both the high voltage lead 36 and the low voltage lead 37 are filled in the mold resin 5 to enhance both insulation strength and mechanical strength. This is because of the configuration.

The winding 3 is a high-voltage winding 31 arranged on the outer diameter side,
Low-voltage winding 32, low-voltage winding 32 and high-voltage winding arranged on the inner diameter side
It is composed of an insulating cylinder 33 for insulating between the core 31 and the low-voltage winding 32 and an insulating cylinder 34 for insulating between the iron core 2 and the low-voltage winding 32. The epoxy resin 52 is injected in a vacuum state and then returned to normal pressure. The epoxy resin 52 penetrates into a small gap by the heat treatment, and subsequent heat curing mechanically integrates all the components including the components not shown in the winding 3 including insulation, and further enhances the heat conduction. Get better.

Generally, when injecting the epoxy resin 52, great care is taken so that no bubbles remain afterwards. Since the injection work of the epoxy resin 52 is carried out in a vacuum atmosphere, even if a space surrounded by the epoxy resin 52, that is, a bubble is formed, this space becomes small and disappears when it is returned to normal pressure after the injection work, but it may be a little. May remain as a large bubble,
This is an important factor in the decrease in dielectric strength.

In order to prevent bubbles, it is preferable to gently inject the epoxy resin 52 from the bottom of the case 1. Therefore, the epoxy resin 52 is injected from the injection port 8 provided near the bottom of the case 1. It is injected so that the epoxy resin 52 is gradually filled from the bottom. In the above-mentioned publication, instead of the injection port 8, a vertically standing injection cylinder that reaches the bottom from the top of the case 1 is provided, and the epoxy resin 52 is injected from the opening above the injection cylinder. However, it is common in that the epoxy resin 52 is injected from the lower side, and there is another configuration in which the epoxy resin 52 is injected from the lower side, and the present invention is not concerned with the injection method. The method of FIG. 3 is shown as an example of the simplest configuration in principle.

The silica sand 51 has a particle size of about 4 to 5 (1
99 μm to 150 μm) is appropriate, but since it is granular, it does not enter the small gap of the winding 3. The gap where silica sand 51 does not enter is filled with epoxy resin 52. In addition, since the wide space between the winding 3 and the metal case 1 is filled with silica sand 51 and the gap is filled with the epoxy resin 52, the epoxy resin is macroscopically filled with fine powder of silica sand at the same ratio. The thermal expansion coefficient and the thermal conductivity are the same as those of the conventional mold resin 5 when mixed.

As described above, since the silica sand 51 does not enter the small gaps between the iron core 2 and the winding 3, only the epoxy resin 52 having good fluidity is filled in such gaps. Air bubbles are less likely to occur in the contents. Further, since the silica sand 51 is filled in the vicinity of the metal case 1, the coefficient of thermal expansion of the mold resin 5 in this portion is close to that of iron which is the material of the metal case 1, and as a result, a mixture of the epoxy resin 52 and the silica sand 51 is obtained. The difference in dimensional change between the mold resin 5 and the case 1 due to temperature change becomes small, and local thermal stress is absorbed by the deformation due to the flexibility of the epoxy resin 52, and peeling hardly occurs. It will be composed.

[0011]

By the way, the outdoor molded transformer is often used as a pole transformer as described above. Therefore, weight reduction is particularly required as compared with installation on the ground. However, as mentioned above, the specific gravity is 2
Since the mold resin 5 which is near is filled and the metal case 1 is used, the weight is increased accordingly. For example, for a pole transformer of 10kVA, the result is that the outdoor molded transformer is about 40kg heavier than the conventional oil-filled transformer.

The present invention has been made in view of the above problems, and an object thereof is to provide a lighter outdoor molded transformer.

[0013]

In order to solve the above problems, according to the present invention, the contents of a mold transformer consisting of an iron core and windings are housed in a case, and the molding resin is placed at a height to cover the contents. In an outdoor molded transformer that is filled and heat-cured, the case shall be made of synthetic resin. In addition, in the outdoor mold transformer in which the contents of the mold transformer consisting of the iron core and the winding are housed in the case, the mold resin is filled to the height to cover the contents and heat-cured, the mold resin is not filled with inorganic material. Made of a mixture of material and epoxy resin, filled with hollow inorganic filler up to the height from the bottom of the case at a predetermined distance from the winding, and the inorganic filler particles are filled by covering the hollow inorganic filler. It has been done. In addition, in the case of an outdoor mold transformer in which the contents of a molded transformer consisting of an iron core and windings are housed in a case, and the height of covering the contents is filled with mold resin and cured by heating, the case is made of synthetic resin. Yes, the mold resin consists of a mixture of an inorganic filler and an epoxy resin, and the hollow inorganic filler is filled to a height near the bottom of the case at a predetermined distance from the winding, and the contents are placed on the hollow inorganic filler. It shall be covered and filled with inorganic filler particles.

[0014]

In the structure of the present invention, when the case is made of synthetic resin, the specific gravity of the synthetic resin is about 1, and the steel sheet used for the metal case has a specific gravity of about 8, so that the mechanical strength of the synthetic resin is that of the steel sheet. Even if the thickness dimension of the case wall, which is considered to be small, is adopted, the result is that the case is lightened. Further, by molding the inorganic filler particles 51 of the molding resin made of a mixture of the inorganic filler and the epoxy resin up to the height near the bottom face of the case, which is a predetermined distance from the winding, as a hollow inorganic filler, this portion Also, the weight of the volume of the hollow portion is lighter than that of filling the same inorganic filler particles as the other portions. By using a synthetic resin case and a hollow inorganic filler together, both weight reductions are added.

[0015]

EXAMPLES The present invention will be described below based on examples.
FIG. 1 is a side view of an outdoor molded transformer showing an embodiment of the present invention, in which the same members as those in FIG.
Similar members are denoted by the same reference numeral with a suffix A, and duplicate description is omitted. 2 differs from FIG. 2 in FIG. 1 in that the case is made of steel plate in FIG. 2, whereas in FIG. 1 it is made of synthetic resin, and the inorganic filler particles 51 are formed near the bottom surface of the synthetic resin case 1A. Instead, it is filled with the hollow inorganic filler 53.

When the case is made of steel plate instead of synthetic resin,
As is well known, the specific gravity of steel plate is about 8, and that of synthetic resin is about 1.
Therefore, if the same volume is used, the weight of the synthetic resin case is about 1/8. The difference in volume is approximately proportional to the thickness of the plate used. The thickness of each of the metal case 1 and the synthetic resin case 1A cannot be determined simply by the ratio of the allowable stresses to each other.

As is well known, the thermal expansion coefficient of the mold resin 5 is close to a value obtained by filling a large amount of silica sand 51, but is still larger than that of a steel plate. Therefore, when the metal case 1 thermally expands due to the temperature rise of the contents of the case including the mold resin 5 and the contents 20 of the outdoor mold transformer, the metal case 1 exerts a force so as to increase the volume, and mainly a tensile stress acts. In the case of the steel plate case 1, it is necessary to withstand this stress. On the other hand, in the case of the synthetic resin case 1A, the coefficient of thermal expansion of the synthetic resin is higher than that of the steel plate, and therefore the stress of the synthetic resin case 1A does not increase so much as the contents of the case expand due to the temperature rise. Since the thickness dimension of the synthetic resin plate constituting the synthetic resin case 1A is determined in consideration of this point as well, as a result, the thickness dimension of the metal case 1 and the synthetic resin case 1A is very different. As a result, the weight of the case is considerably reduced, if not about one-eighth as described above. As the material of the synthetic resin case 1A, there are those that can be used for outdoor use and can be formed into a large size, for example, a fiber reinforced synthetic resin case made by Nippon Quinlite or a pentam resin case made by Nippon Zeon. .

By the way, in the outdoor mold transformer manufactured as a pole transformer of 10 kVA, by adopting the synthetic resin case 1A to the conventional outdoor mold transformer in which the metal case 1 is used, The result was that the weight of 10 kg was reduced. As described above, since the internal volume of the synthetic resin case 1A changes according to the volume change due to the temperature change of the stored items, not only the thermal stress is small, but also the molding resin 5 and the internal surface of the synthetic resin case 1A. It has the feature that the possibility of cracks between the and is reduced and the corona resistance is also excellent.

By filling a hollow inorganic filler 53, which is a hollow filler, as a filler near the bottom surface of the case 1A to a certain height, a hollow portion is formed in this portion, and the weight is reduced accordingly. Since the portion filled with the hollow inorganic filler 53 is located away from the high-voltage winding 3, no discharge occurs in the hollow portion. On the contrary, the hollow inorganic filler is applied only to the position where the electric field strength is low enough to prevent discharge from occurring in the hollow part
53 is filled. In addition, the contents 20 near the bottom of the case 1A
Since the heat flow from the case to the surface of the case 1A is also small, the presence of the hollow inorganic filler 53 does not affect the cooling effect of the outdoor mold transformer.

As the hollow inorganic filler 53, commercially available glass hollow spheres or tubes can be used. By adopting such a hollow inorganic filler 53, in the case of the same 10 kVA pole transformer as described above, the weight is reduced by about 10 kg.

[0021]

As described above, according to the present invention, since the case is made of synthetic resin, the specific gravity of the synthetic resin is smaller than that of the steel plate used for the conventional metal case.
Considering that the mechanical strength of synthetic resin is smaller, the case becomes lighter, and as a result, the effect of contributing to the weight reduction of the outdoor molded transformer can be obtained. Also, if a hollow inorganic filler is filled instead of the inorganic filler up to a height near the bottom of the case that is separated from the winding by a predetermined distance, the volume of the hollow portion becomes lighter. The effect of reducing the weight is obtained. It should be noted that even if only one of the synthetic resin case and the hollow inorganic filler is adopted, the above-mentioned effects can be obtained respectively, but since there is no factor that influences each other in adoption, both of them are adopted as shown in FIG. It is possible to adopt this, and at this time, the effect of further reducing the weight of the outdoor molded transformer in which both the weight reducing effects are added can be obtained.

[Brief description of drawings]

FIG. 1 is a side view of an outdoor mold transformer showing an embodiment of the present invention.

FIG. 2 is a side view of a conventional outdoor molded transformer.

[Explanation of symbols]

1 ... Metal case, 1A ... Synthetic resin case, 11, 11A ...
Box part, 12, 12A… Lid part, 13, 13A… Stand, 20… Contents,
2 ... Iron core, 3 ... Winding wire, 5 ... Mold resin, 51 ... Silica sand (inorganic filler particles), 52 ... Epoxy resin (flexible cured resin), 53 ... Hollow inorganic filler

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tatsuo Nishizawa 1-1 Tanabe Shinden, Kawasaki-ku, Kawasaki-shi, Kanagawa Fuji Electric Co., Ltd. No. 1 in Fuji Electric Co., Ltd. (72) Inventor Tsutomu Fukushima 333, Wheathara, Minamihata-cho, Imari-shi, Saga Kyoden Cut Core Manufacturing Co., Ltd.

Claims (3)

[Claims] 1. An outdoor mold transformer in which the contents of a molded transformer consisting of an iron core and a winding are housed in a case, and a molding resin is filled to a height to cover the contents and heat-cured to form a case. An outdoor molded transformer that is made of resin. 2. An outdoor mold transformer in which the contents of a mold transformer consisting of an iron core and a winding are housed in a case, and the mold resin is filled to a height to cover the contents and heat-cured. A mixture of an inorganic filler and an epoxy resin, which is filled with a hollow inorganic filler up to a height from the bottom of the case at a predetermined distance from the winding, and the inorganic filler is covered on the hollow inorganic filler. An outdoor molded transformer characterized by being filled with grains. 3. An outdoor mold transformer in which the contents of a molded transformer consisting of an iron core and a winding are housed in a case, and a mold resin is filled to a height to cover the contents and heat-cured. It is made of resin, the molding resin is a mixture of inorganic filler and epoxy resin, and the hollow inorganic filler is filled up to a height near the bottom of the case at a predetermined distance from the winding. An outdoor molded transformer, characterized in that the inside is covered with inorganic filler particles.