JP3255778B2 - Manufacturing method of oil immersion all film capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing an oil-immersed all-film capacitor.

[0002]

2. Description of the Related Art A capacitor in which a plurality of capacitor elements each having only a plastic film (hereinafter simply referred to as a film) as a dielectric material is assembled and impregnated with insulating oil is already well known. Usually, this kind of capacitor is manufactured as follows.

That is, a plurality of films are superposed and wound between a pair of electrode foils to form a capacitor element 1 as shown in FIG. After arranging a plurality of capacitor elements 1 side by side, fastening metal fittings 2 are applied to both sides of the capacitor elements 1, and assembled by tightening with studs 3. After that, it is stored in a case, dried by heating under vacuum, impregnated with insulating oil, and further subjected to heat treatment to complete an oil immersion capacitor.

[0004] However, capacitors manufactured in this manner tend to have a low partial discharge starting voltage immediately after the manufacture, and a reduced DC breakdown voltage after long-term heating. After examining the reason, the following results were obtained.

[0005] That is, when the heat treatment is performed by impregnating the insulating oil as described above, the film of the capacitor element swells. Due to this swelling, the layers between the films and between the films and the electrode foils are crushed, and the gaps between the layers are narrowed. Therefore, a sufficient passage for the insulating oil between the layers cannot be secured, and the performance of the insulating oil cannot be used to the maximum. It has been found that this causes a decrease in the partial discharge starting voltage and the DC breakdown voltage.

[0006]

SUMMARY OF THE INVENTION The present invention secures a sufficient flow path of insulating oil between layers even after completion of the capacitor, thereby ensuring the impregnation of the insulating oil between the layers, and the insulating performance of the capacitor. And to improve long-term stability performance.

[0007]

SUMMARY OF THE INVENTION The present invention provides a method for manufacturing a capacitor, comprising a plurality of capacitor elements each having a film as a dielectric material and sequentially performing drying by vacuum heating, impregnation with insulating oil, and heat treatment. The invention is characterized in that capacitor elements are assembled and heat-treated so that the average interlayer gap at the time of completion is 0.3 to 3.0 μm.

[0008]

When a plurality of capacitor elements are assembled by tightening, the interlayer gap of each capacitor element is determined almost uniformly. However, this interlayer gap is not maintained until completion of the capacitor. Thereafter, the film is impregnated with insulating oil and subjected to a heat treatment. The heating at this time causes the film to swell and increase in thickness. Therefore, the interlayer gap is reduced. Therefore, the degree of tightening and the heat treatment temperature at the time of the initial assembly are set such that the average interlayer gap (hereinafter simply referred to as interlayer gap) is 0.3 to 3.0 μm after completion of the capacitor.
Set so that

When the interlayer gap is smaller than 0.3 μm, the partial discharge starting voltage and the DC breakdown voltage are not preferable because they are much lower than the initial values immediately after the production of the capacitor.
When this exceeds 0.3 μm, each voltage approaches the initial value. If the interlayer gap exceeds 3.0 μm, the DC breakdown voltage becomes low, which is not preferable. In addition, the inter-layer gap is represented by Equation 1 where L is the assembly length when a plurality of capacitor elements are assembled, FT is the thickness of the film, M is the number of laminated layers, ET is the thickness of the electrode foil, and N is the number of laminated layers. calculate. The thickness of the film in this case is a value after the heat treatment, that is, after the completion of the capacitor. This depends on the thickness by the micrometer method (the same applies hereinafter).

[0010]

(Equation 1)

[0011]

An embodiment of the present invention will be described. Two polypropylene films each having a thickness of 15 μm were superposed and wound between electrode foils made of aluminum foil to form a capacitor element 1. Then, a plurality of the capacitor elements were juxtaposed, fastened so that the interlayer gap became 1.2 μm, and assembled as shown in FIG. After that, it is dried by heating under vacuum and impregnated with alkyldiphenylethane as insulating oil.
Heat treatment was performed at different temperatures to complete the capacitor.

At this time, the heat treatment was not performed, and the heating temperature was 60 ° C., 80 ° C., 90 ° C. and 100 ° C.
The interlayer gaps of the completed capacitors are 1.2 μm, 0.9 μm, 0.5 μm and 0.3 μm, respectively.
And 0.1 μm. The reason why the interlayer gap varies depending on the heating temperature is that the degree of swelling of the film varies depending on the heating temperature, and the increased thickness varies. Incidentally, the rate of increase in the thickness of the film after each heat treatment was 0% for the case where no heat treatment was performed, and 3% and 6% for the cases where the heating temperature was 60 ° C., 80 ° C., 90 ° C. and 100 ° C. %, 9% and 11%.

The partial discharge starting voltage ratios of the obtained five types of capacitors were obtained, and the results shown in FIG. 1 were obtained. In FIG. 1, the ratio of the partial discharge starting voltage when the rate of increase in the thickness of the film is 0% without performing the heat treatment is set to 1.0. As can be understood from the results, it is found that when the interlayer gap becomes 0.3 μm or less, the partial discharge starting voltage sharply decreases.

Next, for the same capacitor as above, the interlayer gap at the time of initial assembly is set to 0.8 μm and 0.9 μm, respectively.
2. μm, 1.1 μm, 1.6 μm, 3.6 μm and 3.
When heat treatment was performed at 80 ° C., the inter-layer gap after each completion was 0.2 μm and 0.1 μm.
They were 3 μm, 0.5 μm, 1.0 μm, 3.0 μm and 3.3 μm.

For each of these, the rated voltage of 1.3
After applying twice the voltage and conducting heating at 70 ° C. for 100 days, the DC breakdown voltage ratio was determined.
The result as shown in FIG. 2 was obtained. In FIG. 2,
The initial value is assumed that each DC breakdown voltage ratio before applying heat is 1.0. As can be understood from the result, the interlayer gap is set to 0.
In the range of 3 m to 3.0 μm, the rate of decrease in DC breakdown voltage is small, and it is found that long-term reliability is excellent. In addition, when the interlayer gap is smaller than 0.3 μm, and when 3.0 μm
When the width is larger than m, the DC breakdown voltage is significantly lower in each case.

[0016]

As described above, according to the present invention, when manufacturing an oil-immersed all-film capacitor, the interlayer gap of the capacitor after completion is 0.3 μm to 3.0 μm.
By assembling so as to be μm and performing heat treatment,
This produces an effect that a capacitor having excellent partial discharge characteristics and long-term stability can be manufactured.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing a partial discharge starting voltage ratio characteristic of a capacitor according to the present invention.

FIG. 2 is a characteristic diagram showing a DC breakdown voltage ratio characteristic according to the present invention.

FIG. 3 is a plan view showing a state where capacitor elements are assembled.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Capacitor element 2 Clamping fitting 3 Stud

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshihisa Tanaka 47, Umezu Takaune-cho, Ukyo-ku, Kyoto-shi Inside Nissin Electric Co., Ltd. (56) References JP-A-58-93318 (JP, A)

Claims (1)

(57) [Claims] 1. A method of manufacturing an oil-immersed all-film capacitor in which a plurality of capacitor elements each of which is made of only a plastic film as a dielectric material is assembled, and dried by vacuum heating, insulating oil impregnation and heat treatment sequentially. An oil characterized in that the capacitor elements are assembled and heat-treated so that the average gap between the plastic films and between the plastic film and the electrode foil at the time is 0.3 to 3.0 μm. Manufacturing method of immersion all film capacitor.