JPH09326328A - Gas insulated capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent aluminum from being oxidized and hence avoid deterioration of capacitance drop by adding a specific amount of Si to the aluminum. SOLUTION: A capacitor is configured such that two sheets of a film A and a film B are superimposed an wound around a core 4. Any film is manufactured by continuously depositing an Al alloy on a polypropylene film 1 wound on a roll using a vacuum deposition apparatus. In the vacuum deposition apparatus an aluminum alloy containing 0.01% to 5.0% Si is continuously deposited on one surface of the polypropylene film 1 to form an aluminum deposited surface 2. A film having a non-deposited surface 3 downward is assumed to be the film A and a film having the non-deposited surface 3 upward to be the film B. Many sheets of these kinds of film are superimposed and laminated. After they are wound by a predetermined turns, metal is injected to form electrodes 5, 6. The upper injection electrode 5 makes contact with an upper end of the aluminum film of the film A. The lower injection electrode 6 makes contact with a lower end of the aluminum film of the film B.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to improvements in SF ₆ gas insulated capacitors. The capacitor mentioned here is not a small capacitor having a low breakdown voltage as used in a semiconductor circuit. It has a high withstand voltage of several thousand to tens of thousands of volts and a large current. In other words, the capacitor has a large withstand voltage. It is installed in the power receiving equipment of the building and is used to stabilize the voltage. The dielectric is a polypropylene film. The electrodes are Al vapor deposition films.

It is a film obtained by winding a film obtained by vapor-depositing Al on a polypropylene film many times. Use gas instead of oil for insulation. The insulating gas is SF ₆ .
Highly pure Al is used as Al. High-purity Al is evaporated by a resistance heating heater and deposited on a polypropylene film. The polypropylene film wound on a roll is sequentially unwound, and the exposed surface is vapor-deposited with Al vapor. The Al vapor-deposited portion is wound up by a winding roller. Thus, the polypropylene film on the sheet is continuously coated with the Al film with a uniform thickness.

[0003]

2. Description of the Related Art A polypropylene film having a thickness of 5 μm to 10 μm has a thickness of 10 nm to 50 nm (100 Å to 500 nm).
Å) Two MFs (metallized films) vapor-deposited with pure Al having a thickness were stacked and wound in a roll shape, which was used as a capacitor element. In reality, two kinds of electrodes, positive and negative, are required. Therefore, in such a film, two kinds of Al vapor deposition regions are slightly overlapped and wound, and the electrodes are formed on the end faces by metal spraying.

FIG. 1 is a perspective view showing a part of the gas-insulated capacitor in an unrolled state. The width of polypropylene film is 80mm-1000
mm. The thickness is 5 μm to 10 μm as described above.
It is. The length of the film can range from 700 m to 1000 m, which depends on the desired volume.

Al on one side of the polypropylene film 1
The film 2 has been deposited. A part is the non-evaporated surface 3. There are two types of positions for the non-deposited surface 3 and the Al film 2. The film A has a non-evaporated surface 3 below. The film B having the non-vapor-deposited surface 3 above is referred to as a film B.
The film A and the film B are overlapped and wound around the core 4. If the number of turns is small, it may be cylindrical. After winding two kinds of film, round electrodes are made on the end faces by metal spraying.

The metal sprayed electrode 5 on the upper side is connected to the film A having an Al film on the upper side. The lower metal spray electrode 6 is connected to the film B having an Al film on the lower side. One electrode is connected to an even-numbered laminated film, and the other electrode is connected to an odd-numbered laminated film. FIG. 2 is a cross-sectional view showing the state of connection between the Al film and the electrodes. A number of cylindrical elements thus made are arranged in parallel and housed in a container.

When the number of windings is large, it is flattened by compressing from the side after winding. It is the same as forming electrodes on the end faces by metal irradiation. A number of element units in the form of a piece are arranged and housed in a container. In either case, the container is SF
Fill ₆ gas. This is for insulation.

[0008]

When such a gas-insulated capacitor is used for many years, the capacity may decrease. The capacity decrease may be about 10% to 20%. At first there is a certain capacitance, but in 4 years, 6
Capacitance decreases with age. When such a capacitor is collected and disassembled, there is a part where the aluminum vapor deposition region is partially transparent. This phenomenon is called transparency of the electrode. This may be because the aluminum film has come off. Or maybe it is undergoing some kind of chemical change. How does transparency happen?

The present inventor analyzed the transparent portion by Auger electron spectroscopy. Then, it was found that aluminum oxide (alumina) was formed in the transparent part. The aluminum film was not peeled off but was oxidized. This was discovered around 1990. Although α-alumina is transparent, such alumina is produced. What was originally pure aluminum was oxidized and made transparent. The inventor first discovered this.

The reason is considered as follows. The container is filled with SF ₆ and hermetically sealed. It is unlikely that water or oxygen entered after sealing. SF ₆ has no oxidizing property. Then, it is speculated that water and oxygen may have been taken into the film during manufacturing. Deposition of aluminum on polypropylene film is done in vacuum. However, winding the film is done in the atmosphere. At this time, water, oxygen, etc. may enter. That is, when the MF (metallized film) is wound, moisture is adsorbed on the film surface or atmospheric components are adsorbed. Element winding is carried out in a form in which moisture, air, etc. are involved.

When a liquid such as oil is filled for insulation, it is possible that moisture and oxygen are physically removed from the aluminum surface by the action of the insulation oil. However, in the case of a gas-insulated capacitor, once attached water cannot be removed. Moisture, oxygen and vapor-deposited Al film cause chemical reaction during many years. The aluminum will gradually oxidize. The transparency of the electrodes is caused by the oxidation of aluminum. When the vapor-deposited Al film, which is the electrode, is oxidized, that portion becomes an insulator. Since the effective area as an electrode decreases, the capacitor characteristics deteriorate. In particular, a decrease in capacity occurs.

Such aging occurs in a large number of capacitors. Capacitors with reduced capacity must be collected and replaced. This takes time and money. There is a demand to manufacture a capacitor that does not deteriorate in characteristics over time. However, no suitable solution has been found yet. This is the current situation.

[0013]

The present invention prevents oxidation by adding a trace amount of Si, Mg, Mn and Cu to aluminum. That is, the deposited Al film is formed of Si, Mg, Mn, Cu.
An Al alloy film containing By doing so, the oxidation resistance and corrosion resistance of the aluminum foil electrode can be improved. Due to the action of impurities, the aluminum layer does not oxidize even if water or oxygen is initially attached. If it is not oxidized, aluminum oxide (alumina) is not generated, so the effective area of the electrode does not decrease. It is possible to avoid the deterioration of the capacity.
It is possible to obtain capacitors with stable characteristics for many years.

However, if the amount of impurities is too large, the aluminum layer may become hard and brittle. Curing may also facilitate peeling from the film. The proper mixing ratio of Si, Mg and Mn to aluminum is as follows.

(1) Si is 0.01 wt% to 5.0 w
t% (the rest is aluminum) (2) Mg is 0.02 wt% to 5.0 wt% (the rest is aluminum) (3) Mn is 0.02 wt% to 2.0 wt% (the rest is aluminum) (4) Cu is 0.01 wt% to 5.0 wt% (the remainder is aluminum) (5) Any two or more kinds of Si, Mg, Mn, and Cu may be in the ratios (1) to (4). Leave (the rest is aluminum).

If the amount of impurities is lower than the lower limit value, the effect of adding impurities hardly appears. In other words, it is impossible to prevent the aluminum from being oxidized. On the other hand, if the amount of impurities added exceeds the upper limit, the aluminum alloy becomes hard, which hinders the work of winding it in a coil many times. In addition, the electric resistance increases and heat generation in the capacitor also increases.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a SF ₆ gas insulated capacitor in which a polypropylene film is coated with Si, M
An aluminum film containing a small amount of g, Mn, and Cu is vapor-deposited and wound to form a capacitor. The addition of these impurities can prevent the oxidation of aluminum. To add these metals to the aluminum film, the aluminum vapor deposition equipment must be changed. There can be several means.

The easiest way is to use an aluminum alloy as the vapor deposition material itself. An aluminum alloy containing a predetermined amount of Si is put in a crucible and heated and evaporated. In this case, it is not necessary to change the vapor deposition equipment because only the vapor deposition material needs to be changed.

The second method is a method of initially containing aluminum and impurities such as Si in one crucible. Resistance heating, electron beam heating, etc. can be used for heating the crucible. A third method is to use a different crucible. An aluminum crucible and a crucible for impurities such as Si are used. With this, the content of impurities can be freely set and changed.

In any case, by adding these impurities to aluminum, it is possible to prevent oxidation of the deposited Al film for many years. Does not oxidize due to moisture adhering to the material when it is wound. Since aluminum oxide is not generated, the effective area of aluminum does not decrease. Aluminum does not become transparent. The deterioration of capacitor characteristics due to transparency can be improved. Since failure such as capacity reduction does not occur, 4-5
No need for complicated maintenance such as collecting and replacing in a year. This is a highly practical invention.

[0021]

EXAMPLE The shape of the capacitor of the present invention does not differ from the conventional one. As shown in the partially unrolled view of FIG. 1, two films A and B are superposed and wound around a core 4. Each film is produced by continuously evaporating an Al alloy on a polypropylene film wound on a roll by a vacuum evaporation device. The thickness of the polypropylene film is about 5 μm to 10 μm. The thickness of the aluminum alloy film is 10 nm to 50 nm (100
Å-500Å). The width of the polypropylene film is about 80 mm to 1000 mm, and the width is appropriately selected according to the desired capacity. The total length of polypropylene film is 700m
It is about 1000 m.

In a vacuum vapor deposition apparatus, an aluminum alloy containing a predetermined amount of one or more of Si, Mg, Mn and Cu is continuously vapor deposited on one surface of a polypropylene film.
A part of the film is a non-deposited surface that is not covered with the aluminum alloy. Two kinds of vapor-deposited films having different non-deposited surfaces are prepared. In FIG. 1, the non-evaporated surface on the lower side is referred to as film A, and the non-evaporated surface on the upper side is referred to as film B. A large number of these two kinds of films are laminated. When it is wound a predetermined number of times, the end surface is sprayed with a metal and the electrode 5,
6 is formed. The upper sprayed electrode 5 contacts the upper end of the aluminum film of the film A. The lower sprayed electrode 6 contacts the lower end of the aluminum film of the film B.

FIG. 2 is a schematic sectional view of the connecting portion. Film A and film B alternate in the cross section. Film A is all connected in the circumferential direction,
Each is connected to the sprayed electrode 5 at the upper end. Similarly, the films B are all connected in the circumferential direction, but are connected to the spray electrode 6 at their lower ends.

FIG. 3 shows one such capacitor structure.
The equivalent circuit is drawn by regarding the sheets as capacitor elements. When a voltage is applied between the two electrodes by the AC power source 7, the aluminum / polypropylene / aluminum unit elements of each sheet function as one capacitor.

[0025]

According to the present invention, in an SF ₆ insulating gas capacitor, aluminum is prevented from oxidizing by adding a small amount of Si, Mg, Mn, and Cu as impurities to the aluminum vapor deposition film. Addition of these metals effectively prevents aluminum oxidation. Since the oxidation does not occur, the effective area of the aluminum film does not decrease. Aluminum electrode can maintain its area for many years. The troublesome work of replacing the capacitors in 4 to 5 years is no longer necessary. It is an invention with excellent effects.

[Brief description of drawings]

FIG. 1 is a perspective view showing a schematic configuration of an SF ₆ gas-insulated capacitor with a part thereof unrolled.

FIG. 2 is a schematic cross-sectional view showing a connection between an aluminum film and a metal spray electrode.

FIG. 3 is an equivalent circuit diagram showing that one Al / polypropylene / Al element is integrated by a sprayed electrode into one capacitor.

[Explanation of symbols]

 1 Polypropylene film 2 Al vapor deposition surface 3 Non-vapor deposition surface 4 Core 5 Metal sprayed electrode 6 Metal sprayed electrode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomohiro Kawai 47 Umezu Takaune-cho, Ukyo-ku, Kyoto City, Kyoto Prefecture Nissin Electric Co., Ltd. Electric Co., Ltd.

Claims (5)

[Claims] 1. A capacitor, which is housed in a container filled with SF ₆ gas and has a structure in which a film obtained by vapor-depositing Al on a polypropylene film is wound many times.
An SF ₆ gas-insulated capacitor, characterized in that 0.01% to 5.0% of Si is added to 1 l. 2. A capacitor, which is housed in a container filled with SF ₆ gas and has a structure in which a film obtained by vapor-depositing Al on a polypropylene film is wound many times.
SF ₆ gas-insulated capacitor, characterized in that 0.02% to 5.0% of Mg is added to 1 l. 3. A capacitor, which is housed in a container filled with SF ₆ gas and has a structure in which a film obtained by vapor-depositing Al on a polypropylene film is wound many times.
SF ₆ gas-insulated capacitor, characterized in that 0.02% to 2.0% of Mn is added to 1 l. 4. A capacitor, which is housed in a container filled with SF ₆ gas and has a structure in which a film obtained by vapor-depositing Al on a polypropylene film is wound many times.
An SF ₆ gas-insulated capacitor, characterized in that 0.01% to 5.0% of Cu is added to 1 l. 5. A capacitor, which is housed in a container filled with SF ₆ gas and has a structure in which a film obtained by vapor-depositing Al on a polypropylene film is wound many times.
0.01% to 5.0% Si, 0.02% to 5.
0% Mg, 0.02% -2.0% Mn, 0.01%
An SF ₆ gas-insulated capacitor, characterized in that at least two types of substances of ˜5.0% Cu are added.