JPS59196508A - Insulated wire for oil-filled transformer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an insulated wire that has characteristics suitable for use in oil-filled transformers and is inexpensive to manufacture.

Generally speaking, insulated wires for oil-filled transformers need to have excellent resistance to insulating oil since they come into contact with insulating oil, and they also need to have minimal deterioration of insulation properties due to hydrolysis when a small amount of water gets mixed into the insulating oil. This is required. Conventionally, so-called polyvinyl formal copper wire has been used in which a polyvinyl formal insulating paint is coated and baked on the surface of the copper wire in order to impart the above characteristics.

However, polyvinyl formal insulation paints have a very high viscosity when the concentration of non-volatile components (mainly resin components) in the paint is high, so the concentration must be set low during application. As an insulated wire for a transformer, a thick copper wire of 1 fi or more is usually used, and therefore the insulating layer also needs to have a thickness of about 35 to 60 μm. For this reason, in order to form an insulating layer of the required thickness using polyvinyl formal insulating paint, a time-consuming and labor-intensive method of repeating coating and baking more than 10 times is usually adopted, which reduces the manufacturing cost of insulated wires. The drawback was that it was expensive. Moreover, the polyvinyl formal insulating paint itself was expensive. In addition, polyvinyl formal electric wire has relatively excellent insulating oil resistance properties, but it does not have enough resistance to deterioration of the insulation layer due to hydrolysis when a small amount of water is mixed in the insulating oil, especially at high temperatures. The results are not satisfactory, and there is still room for improvement.

This invention was made to eliminate the above-mentioned conventional drawbacks, and is an insulated wire for oil-filled transformers that has a simpler manufacturing process, is lower in cost, and has superior performance compared to conventional polyvinyl formal copper wires. is intended to provide. That is, as shown in the drawings, the insulated wire according to the present invention has an insulating coating layer 2 on the surface of a conductor 1 such as a round wire or a rectangular wire.
The lower layer 3 is formed by applying and baking acrylic insulation paint, and the upper layer 3 is formed by applying and baking polyvinyl formal insulation paint.
This is a double structure consisting of 4.

The above-mentioned acrylic insulating paint is generally much cheaper than polyvinyl formal insulating paint, and is characterized by a small increase in viscosity even when the concentration of nonvolatile components is increased. Therefore, by setting the concentration high, the lower layer 3 that occupies a part or main part of the insulating coating layer 2 can be formed by coating and baking twice, and together with this, the polyvinyl formal insulating paint for forming the upper N4. Since the coating and baking process only needs to be performed once or several times, the material cost and manufacturing cost of the insulating coating layer 2 are greatly reduced.

The thickness of such an insulating coating layer 2 is preferably about 35 to 60 μm, particularly preferably 40 to 50 μm, and the thickness of the upper N4 layer is preferably about 2 to 10 μm, especially around 5 μm from the viewpoint of characteristics and manufacturing. Optimal.

The acrylic insulation paint used to form the lower layer 3 is as follows:
For example, the resin component contains nitrile compounds such as acrylonitrile and methacrylonitrile, and glycidyl compounds such as glycidyl methacrylate and allyl glycidyl ether as essential components, and optionally styrene, α-methylstyrene, methyl methacrylate, ethyl acrylate, etc.
Examples include copolymers of monomers containing other compounds having double bonds such as N-butyl methacrylate, methacrylic acid, and acrylic acid, and water-dispersed acrylic paints are particularly suitable. However, as the above copolymer,
50 to 80 mo of dilyl compound in the monomer component
%, the glycidyl compound is preferably 2 to 5 mo 1%, and if both are less than the above ranges, the general properties, especially the thermal properties, of the obtained electric wire will deteriorate, and the nitrile compound will deteriorate. If the amount of the glycidyl compound is too large, the general properties will be insufficient, and if the amount of the glycidyl compound is too large, the mechanical properties of the resulting wire will deteriorate. On the other hand, upper layer 4
Various commercially available polyvinyl formal insulating paints can be used to form the insulating coating.

Hereinafter, the present invention will be specifically explained with reference to Examples.

Table 1 below shows the monomers of the acrylic insulating paint used to form the lower layer 4 of the insulation coating layer 3 in the insulated wire A of the first embodiment and the insulated wire B of the second embodiment according to the present invention. Indicates the ingredients.

Table 1 Using the monomer mixture shown in the above table, using sodium lauric acid ester as a surfactant and potassium persulfate as a polymerization initiator, emulsion polymerization was carried out while rotating at 60 to 70°C in a nitrogen stream, and the nonvolatile content was A 20% by weight water-dispersed acrylic insulation paint was prepared. This insulating paint was electrodeposited on the surface of a copper wire with a diameter of 1.6 tm using a conventional method at a line speed of 6 m/min, and the coated wire was introduced into N,N'-dimethylformamide vapor. Dry at ℃, then apply polyvinyl formal insulation paint (trade name: WM-4 manufactured by Hitachi Chemical Co., Ltd.) to the surface.
47) is coated twice and baked at a temperature of 350°C, so that the lower N3 of the insulating coating layer 2 has a thickness of 35 μm and the upper layer 4
Insulated wires A and B each having a thickness of 5 μm were obtained.

On the other hand, for comparison, insulated wire C in which an insulating layer with a thickness of 40 μm was formed in the same manner using only the water-dispersed acrylic insulating paint used in the first example, and the polyvinyl formal used in the example Insulated wire strips each having an insulating layer with a thickness of 40 μm were manufactured by applying and baking only the insulating paint based on the conventional method.

When the above insulated wires A to D were tested for dielectric breakdown voltage, softening resistance, and insulating oil resistance, the results shown in Table 2 below were obtained. In addition, the insulating oil resistance is determined by applying 30 g of insulating paper containing about 2600 ppm of water to 400 ml of insulating oil to a length of 3.
The dielectric breakdown voltage after being sealed together with a wire test piece from country 0 and stored at the indicated temperature and number of days is expressed as a residual rate (%) with respect to the voltage before being sealed.

Table 2 As is clear from the above table, the insulated wire according to the present invention is
Compared to conventional polyvinyl formal electric wires, the resistance to deterioration of the insulation coating layer 2 when a small amount of water in the insulating oil gets mixed in is greatly improved, and the resistance is particularly good under high temperatures, and the wire is resistant to softening. Moreover, each property is good even when an insulating coating layer is formed using only acrylic insulating paint. In addition, as mentioned above, the insulating coating layer 2
A part or main part of the insulation coating layer 2 can be formed by one-time coating and baking using an inexpensive acrylic insulation paint, etc., and the amount of expensive polyvinyl formal insulation paint used can be reduced accordingly. In addition to reducing the material cost, the manufacturing process is simplified because the coating and baking process only needs to be completed twice, and the manufacturing cost is also greatly reduced.

[Brief explanation of drawings]

The drawing is a schematic cross-sectional view of an insulated wire for an oil-filled transformer according to the present invention. ■...Conductor, 2...Insulating wave ri layer, 3...Lower layer,
4... Upper layer. Applicant Denko Co., Ltd. Mitsubishi Electric Co., Ltd. Patent Attorney Tadashi Mizowaki Yukio Kubo 39-

Claims (1)

[Claims] An insulated wire for an oil-filled transformer in which a double insulation coating layer is formed on the conductor surface, consisting of a lower layer formed by applying and baking an acrylic insulation paint and an upper layer formed by applying and baking a polyvinyl formal insulation paint.