JPS6154242B2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to an oil-filled capacitor.

As is well known, due to the trend of the times, there is a strong demand for this type of oil-filled capacitor to be flame retardant, small and lightweight, and in order to meet this demand, in recent years only plastic film has been used as a dielectric between the electrodes. Various types of capacitor elements have been proposed in which the capacitor element is impregnated with a mixture of aromatic hydrocarbon oil and orthophosphoric acid ester having a self-extinguishing function. However, since the plastic film has the property of being dissolved and swollen by mixed oil, the excellent properties of the plastic film cannot be fully exhibited, and it is extremely difficult to obtain an oil-immersed capacitor with desired properties. Ta.

The inventors conducted various experiments on the compatibility of biaxially oriented polypropylene film (hereinafter simply referred to as PP film) as a plastic film with mixed oil, and found that the atactic structure (hereinafter simply referred to as AT) of PP film. Ionic substances (impurities) whose parts are easily dissolved or swollen by aromatic hydrocarbon oil, and which are liberated thereby
However, it was confirmed that dielectric properties were adversely affected due to the dissolution of orthophosphoric acid ester, which is not a particular problem for the PP film itself.

In view of the above, this invention was created by mixing 30 to 55% by weight of aromatic hydrocarbon oil with orthophosphoric acid ester in a capacitor element formed by interposing only a PP film with an AT content of 5% or less. By impregnating it with a mixed oil, it provides an oil-filled capacitor that is flame retardant and has excellent electrical characteristics.

Examples of the orthophosphoric acid esters include tricresyl phosphate (hereinafter simply referred to as TCP), tri(ethylphenyl) phosphate (hereinafter simply referred to as TEP), tricylenyl phosphate, and tri(isopropylphenyl) phosphate. These can be used alone or in combination. Examples of the aromatic hydrocarbon oil include diisopropylnaphthalene (hereinafter simply referred to as DIPN), which is an alkylnaphthalene, and monoisopropylnaphthalene, and 1-phenyl-1-(dimethylphenyl)ethane (which is diallylalkane). Below simply
It is called PXE. ), 1-phenyl-1-(ethyl phenyl) ethane (hereinafter simply referred to as EDE), alkylbenzene, alkyl diphenyl, etc. alone or in combination are used.

Here, the mixing ratio of the aromatic hydrocarbon oil is 30
The reason for setting it at ~55% by weight is that if it is less than 30% by weight, the viscosity and pour point of the mixed oil will be high, which will cause problems in terms of impregnating capacitor elements, and the excellent electrical properties of aromatic hydrocarbon oils. This is because the effect cannot be fully demonstrated. Moreover, if it exceeds 55% by weight, it is flammable and therefore the self-extinguishing function of the orthophosphoric acid ester cannot be fully exhibited, and the solubility or swelling property of the AT portion of the PP film increases.

Next, mix oil A, which is a mixture of TCP and DIPN, and TEP.
The relationship between the AT content of the PP film and the amount of swelling after heating at 100°C for 72 hours was examined for mixed oil B containing PXE and mixed oil C containing TCP and EDE, as shown in Figure 1. It was hot. The mixing ratio of these mixed oils A to C is 50:50 in weight percent.

As is clear from FIG. 1, if the AT content of the PP film is 5% or less, that is, the isotactic structure content of the PP film is about 95% or more, the degree of swelling is 10% or less.

Next, embodiments of the present invention will be described in detail.

Example: As a dielectric between aluminum foils,
PP with AT content of 1%, 3%, 5% and 7%
4 formed with only a film (3 layers) interposed
Twelve types of test capacitors _a1 , _a3 , _a5 , _a7 ,
We investigated b ₁ , b ₃ , b ₅ , b ₇ , c ₁ , c ₃ , c ₅ and c ₇ .

Figure 2 shows a test capacitor impregnated with mixed oil A.
a ₁ a ₃ , a ₅ , a ₇ , Figure 3 shows the sample capacitors b ₁ , b ₃ , b ₅ , b ₇ impregnated with mixed oil B, and Figure 4 shows the test capacitors impregnated with mixed oil C. Capacitors c ₁ , c ₃ , c ₅ , c ₇
For each, the relationship between the AT content of the PP film, the dielectric loss tangent, and the corona onset voltage is shown. In addition, in Figures 2 to 4, the solid line (tan
δ) indicates the dielectric loss tangent, and the dotted line (CSV) indicates the corona onset voltage.

As is clear from Figures 2 to 4, the test capacitor has a PP film AT content of 5% or less.
a ₁ , a ₃ , a ₅ , b ₁ , b ₃ , b ₅ , c ₁ , c ₃ , c ₅ have lower dielectric properties than the test capacitors a ₇ , b ₇ , c ₇ with AT content of 7%. The tangent is low and the corona initiation voltage is high. This result is clear from Figure 1,
This can be understood from the fact that the degree of swelling decreases as the AT content of the PP film decreases.

As detailed above, according to the present invention, it is possible to obtain an oil-filled capacitor that is flame retardant and has excellent electrical characteristics, and because the dielectric loss is small, there is no need to increase the heat dissipation area, making it possible to reduce the size and weight. It is extremely useful.

Note that the present invention is not limited to the above-mentioned embodiments, and various modifications are possible. For example, 0.5 to 5% by weight of one or more stabilizers such as epoxy, phenol, and amine are mixed in the mixed oil. Of course, the life of the oil-immersed capacitor may be extended by trapping impurities in the mixed oil.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the content of the atactic structure and the swelling degree of a biaxially oriented polypropylene film, and FIGS. FIG. 3 is a diagram showing the relationship between structure content, dielectric loss tangent, and corona onset voltage. tanδ: dielectric loss tangent, CSV: corona starting voltage,
A: Mixed oil A, B: Mixed oil B, C: Mixed oil C.

Claims (1)

[Scope of Claims] 1. A capacitor element formed by interposing only a biaxially oriented polypropylene film with an atactic structure content of 5% or less as a dielectric between electrodes, and an aromatic hydrocarbon oil in orthophosphoric acid ester. An oil-filled capacitor impregnated with a mixture of 30 to 55% by weight of oil. 2. The oil-filled capacitor according to claim 1, wherein the mixed oil is a mixture of tricresyl phosphate and alkylnaphthalene. 3. Claim 1, in which the mixed oil is a mixture of tricresyl phosphate and diallyl alkane.
Oil-filled capacitor as described in section. 4. The oil-filled capacitor according to claim 1, wherein the orthophosphoric acid ester is tri(ethyl phenyl) phosphate.