JPH07254524A - Method for manufacturing outdoor molded transformer - Google Patents

Abstract

(57) [Summary] [Purpose] The upper surface of the mold resin that comes into contact with air has water resistance and does not cause cracks. [Constitution] Case 1 is filled with silica sand 51 and epoxy resin 52
After injecting, the water-resistant mold resin in which the water-resistant treated filler powder is mixed with the thermosetting resin is injected from above in a predetermined amount. By the momentum of injection, this water-resistant mold resin mixes with the epoxy resin 52 on the layer of silica sand 51 to form a water-resistant mold resin layer 70. Since the upper surface of the water resistant mold resin layer 70 is water resistant, even if water enters the upper space of the case 1 due to a breathing action due to temperature change, it does not adhere to the surface, and the filler powder is Since they are mixed, the coefficient of thermal expansion is small, and therefore the surface does not crack due to temperature change.

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.

A water-resistant coating on the upper surface of the mold resin 5, for example, a water-resistant resin obtained by pouring a prescribed thickness of a silane-treated filler DT1077JP manufactured by Ciba-Geigy Japan Inc. added to an epoxy resin) and curing it. Layer 7 has been formed. Due to the breathing action of air in and out of the upper space of the case 1 due to temperature change, moisture may enter the case 1. In order to prevent such moisture from adhering to the upper surface of the mold resin 5 and lowering the insulation strength, the water resistant resin layer 7 is employed as described above.
If sufficient measures are taken to prevent moisture from entering the case 1, the formation of the water resistant resin layer 7 may be omitted. The thickness of the water resistant resin layer 7 may be so thin as not to affect the mold resin 5 with water, so that the amount of the water resistant resin to be used is not increased by gently pouring the resin.

[0012]

When the epoxy resin 52 is injected after the silica sand 51 is filled, a large amount of the epoxy resin 5 is injected so that the silica sand 51 is entirely immersed in the epoxy resin 52. Therefore, a layer of only the epoxy resin 5 is formed on the upper surface of the mold resin 5. Epoxy resin without filler 5
Since the coefficient of thermal expansion is much larger than that of the case 1 and the area of the upper surface of the mold resin 5 is large, the epoxy resin 5 may crack due to temperature change. When cracks occur, the water resistant resin layer 7 provided on the upper surface of the mold resin 5 also cracks, and there is a possibility that moisture may penetrate into the interior from the cracked portions and deteriorate the insulation strength.

An object of the present invention is to solve the above problems and to provide a method for manufacturing an outdoor mold transformer in which the mold resin maintains water resistance and does not cause cracks due to temperature change on the upper surface in contact with air. To provide.

[0014]

In order to solve the above problems, according to the present invention, the contents of a molded transformer consisting of an iron core and windings are housed in a case to cover at least the contents of inorganic filler particles. An outdoor mold transformer that is filled to a height, then filled with a flexible thermosetting resin from the bottom of the case to a height at which all of the inorganic filler particles are immersed in a vacuumed state, and then heat-cured. In the manufacturing method, after the flexible thermosetting resin is injected, a predetermined amount of the water-resistant mold resin in which the water-resistant treated filler powder is mixed with the thermosetting resin is injected, and then the resin is heat-cured. In addition, after returning the inside of the case to a normal pressure, a water-resistant mold resin is injected and the vacuum is drawn again.

[0015]

In the structure of the present invention, by filling silica sand and injecting a flexible thermosetting resin, a predetermined amount of a water-resistant molding resin prepared by mixing water-resistant treated filler powder with the thermosetting resin is injected from above. A flexible thermosetting resin on silica sand and a water-resistant mold resin are mixed to form a water-resistant mold resin layer. The thickness of this water-resistant mold resin layer is the sum of the amount of the water-resistant mold resin injected and the portion of the flexible thermosetting resin that has been previously injected above the surface of the silica sand layer. A layer having a sufficient thickness can be formed by injecting a required amount of molding resin.

Since the upper surface of the water resistant mold resin layer has water resistance, even if water enters the upper space of the case 1 due to a breathing action due to temperature change, it does not adhere to the surface. Further, since the filler powder is mixed, the coefficient of thermal expansion is small, and therefore cracks due to temperature changes are less likely to occur. The flexible thermosetting resin is injected in a vacuumed state, but the water-resistant mold resin is returned to normal pressure, then injected and vacuumed again. The air bubbles mixed in the mixed layer of this and the flexible thermosetting resin grows and rises as the vacuuming progresses, and the momentum further promotes the mixing of the water-resistant mold resin and the flexible thermosetting resin. .

[0017]

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. The same members as those in FIG. 2 are designated by the same reference numerals, and a duplicate description will be omitted. 1 is different from FIG. 2 in that
The water resistant resin layer 7 is replaced with a water resistant molded resin layer 70 shown by diagonal lines in the figure. Water resistant mold resin layer 70
Is formed by injecting an epoxy resin 52 filled with silica sand 51 from below and then injecting a water resistant mold resin from above so as to mix with the epoxy resin 52 on the layer of silica sand 51 as much as possible. Therefore, the waterproof mold resin layer 70 is a mixture of the waterproof mold resin and the epoxy resin 52.

Since the filler powder is mixed in the water-resistant molding resin to be injected later, its specific gravity is larger than that of the flexible thermosetting resin in which the filler powder is not mixed, so that only the epoxy resin 52 layer is formed. If it is thick, the injected water-resistant mold resin that is not mixed with the flexible thermosetting resin will settle below the flexible thermosetting resin to form a layer on the layer of silica sand 51, and A mixed layer, and if it exists on top of it, it becomes a layer of flexible thermosetting resin. If the portion of the flexible thermosetting resin silica sand layer is reduced as much as possible, practically all will be a mixed layer with water resistance, and the surface after heat curing will be water resistant. Become.
Further, since the water-resistant filler powder is mixed, the coefficient of thermal expansion becomes small and approaches that of case 1, so there is no risk of cracks in the surface layer due to temperature changes.

It is desirable to ensure that both resins are mixed. Therefore, the resin is agitated by injecting the water-resistant mold resin vigorously. In order to more reliably mix the water-resistant mold resin and the epoxy resin 52, it is possible to adopt a method in which the atmosphere is once returned to normal pressure, the water-resistant mold resin is injected, and then a vacuum is drawn again. . When the water-resistant mold resin is injected in the process of vacuuming from normal pressure, the mixed air bubbles grow and rise, and the resin is mixed up and down with the force of the mixture. Mixing of both resins is more reliable than the injection method.

[0020]

As described above, according to the present invention, when the water-resistant mold resin layer is formed by injecting the water-resistant mold resin from above, the water-resistant mold resin layer has a water-resistant upper surface, so that the temperature Even if water enters the upper space of Case 1 due to the change in breathing, it does not adhere to the surface, and there is no possibility that water will reduce the insulation strength.
Further, since the filler powder is mixed, the coefficient of thermal expansion is small, and therefore cracks due to temperature changes are less likely to occur, so that it is possible to avoid a decrease in insulation strength due to the intrusion of water into the cracks.

If a method is adopted in which the water-resistant mold resin is returned to normal pressure and then evacuated again, the water-resistant mold resin and the mixed layer of the flexible thermosetting resin and the water-resistant mold resin are mixed when evacuating again. The mixed bubbles are further promoted by the force of rising and increasing bubbles that are contained, and the effect of stabilizing the characteristics of the water resistant mold resin layer 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 ... Case, 20 ... Contents, 2 ... Iron core, 3 ... Winding, 5 ... Mold resin, 51 ... Quartz sand (inorganic filler particles), 52 ... Epoxy resin (flexible thermosetting resin), 70 ... Water resistant mold Resin layer

Front page continued (72) Inventor Tatsuo Nishizawa 1-1 Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa Fuji Electric Co., Ltd. Electric Machinery Co., Ltd. (72) Inventor Tsutomu Fukushima 333 Wheat Hara, Minami Hata Town, Imari City, Saga Prefecture Kyoden Cut Core Manufacturing Co., Ltd.

Claims (2)

[Claims] Claim: What is claimed is: 1. A mold transformer including an iron core and a winding, the contents of which are housed in a case, and the inorganic filler particles are filled to a height that at least covers the contents. In the method for manufacturing an outdoor molded transformer, injecting a thermosetting resin from the lower part of the case to a height at which at least all of the inorganic filler particles are immersed, and then heat curing the same.
An outdoor mold transformer characterized by injecting a flexible thermosetting resin, injecting a predetermined amount of a water-resistant molding resin prepared by mixing water-resistant filler powder with the thermosetting resin, and then heating and curing the resin. Manufacturing method. 2. The method for producing an outdoor molded transformer according to claim 1, wherein the inside of the case is returned to normal pressure, water-resistant molding resin is injected, and then vacuum drawing is performed again.