JPH0115130B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application and Prior Art] The present invention relates to a metallized film capacitor using plastic film as a dielectric.
Plastic film has excellent properties as a dielectric material for capacitors. Among them, polyethylene terephthalate film (hereinafter referred to as PET film)
has particularly excellent electrical properties, productivity and economy, and is therefore the mainstream of this type of dielectric. Metallized film capacitors made of metalized PET film are impregnated with wax or oil in order to stabilize their characteristics and improve their breakdown voltage.

However, conventional metallized film capacitors impregnated with wax or oil have the following problems that need to be solved. (1) When used at high temperatures for long periods of time, impregnating agents such as wax and oil deteriorate, and if sealing is not sufficient, they evaporate and escape, reducing dielectric strength. (2) If the sealing is incomplete, the impregnating agent may leak outside. (3) Since the film layers are separated by the impregnating agent, when used in an AC circuit, the vibration of the film generates a humming noise, so a thick exterior is required as a countermeasure.

[Purpose of the invention]

The present invention is intended to solve the problems (1), (2), and (3) above, and has stable characteristics during long-term use, and does not cause a decrease in dielectric strength or leakage. It is an object of the present invention to provide a metallized film capacitor which does not generate beat noise and whose exterior can be simplified.

[Structure of the invention]

The present invention provides a metallized film characterized in that a wound type metallized film capacitor element having a polyethylene terephthalate film (PET film) having a centerline average roughness of 0.15 to 0.30 μm as a dielectric material is impregnated with a thermosetting resin. It is a capacitor. The embodiment will be described below with reference to FIGS. 1 and 2. In Figure 1, 1 is a metallized film made of PET film with a metal electrode 1a deposited on one side, and the other side has a center line average roughness of 0.15 to 0.30 μm.
The unevenness 1b is formed. Two layers of this metallized film 1 are wound together, and a metallicon electrode 2 is placed on the end surface.
is formed and impregnated with the thermosetting resin 3. FIG. 2 shows another embodiment of the present invention using a double-sided metallized film 4, in which 4a is a metal electrode on both sides, and 5 is a PET film having irregularities 5a on both sides with an average centerline roughness of 0.15 to 0.30 μm. It is. 2 is a metallic electrode, and 3 is an impregnated thermosetting resin. In addition,
In the embodiments shown in FIGS. 1 and 2, the surfaces of metal electrodes 1a and 4a are smooth, but the surfaces of metal electrodes 1a and 4a may have irregularities similar to those of 1b or 5a.

〔Effect of the invention〕

Since the present invention has the above configuration, it has the following effects. The following table shows the surface roughness of various PET films (JIS-B-0601 center line average roughness Ra)
The results are shown below. In the following table, A
The surface is smooth, and the surface becomes rough in the order of B, C, D, and E.

PET film center line average roughness (Ra) Sample A 0.10 (μm) 〃B 0.15 〃 〃C 0.25 〃 〃D 0.30 〃 〃E 0.35 〃 The capacitors shown in Fig. 1 were made from the above samples A to E, and for each capacitor, (1) Short-time breakdown voltage, (2) Capacity change rate after 1000 hours of continuous durability test according to JIS-C-4908, (3) No breakdown after conducting the above-mentioned continuous durability test. ratio of numbers,
In other words, when we measured the residual rate, Figures 3 and 4 showed that
The results shown in the figure and FIG. 5 were obtained. In addition, the capacitor shown in Figure 1 was made using sample C,
Conventional capacitor impregnated with wax and JIS-C
-4908 was subjected to a 3000 hour continuous durability test and the insulation resistance values were compared and the results shown in Figure 6 were obtained.

As shown in Figures 3, 4, and 5, samples B, C, and D, that is, the center line average roughness Ra,
It can be seen that capacitors using PET films of 0.15 to 0.30 μm are excellent in short-time breakdown voltage (Figure 3), rate of change in capacity (Figure 4), and survival rate (Figure 5). That is, Ra is 0.15μm
The following (Sample A) has a low short-time breakdown voltage (Sample A) due to insufficient amount of thermosetting resin between the film layers (Sample A).
In addition, the results of the continuous durability test showed that corona discharge is likely to occur, causing the metal electrode to scatter and the rate of capacitance change to be large (Figure 4). The actual thickness becomes thinner,
The short-time breakdown voltage is low (Figure 3), and the continuous durability test results show that the survival rate drops to 80%. (Figure 5) Furthermore, as shown in Figure 6, it can be seen that the capacitor of the present invention impregnated with a thermosetting resin has a more stable insulation resistance value than the conventional capacitor that uses wax as an impregnating agent. . This is because wax decomposes and evaporates when used at high temperatures for a long time, whereas thermosetting resins harden further.
In addition, conventional capacitors impregnated with wax tend to leak and produce humming sounds, but the capacitors of the present invention impregnated with thermosetting resin do not suffer from such problems.

As described above, in the present invention, a PET film with a centerline average roughness Ra of 0.15 to 0.30 μm is used, and a sufficient insulating layer is formed between the film layers by using a thermosetting resin as an impregnation agent. However, it has the excellent effect of solving the above-mentioned problems (1), (2), and (3) of the conventional metallized film capacitor impregnated with wax or oil, and providing a metallized film capacitor with excellent characteristics.

[Brief explanation of drawings]

Figure 1: Partial sectional view of an embodiment of the capacitor of the present invention, Figure 2: Partial sectional view of another embodiment of the capacitor of the present invention, Figure 3: Short-time breakdown voltage characteristics of the capacitor of the present invention. FIG. 4: A diagram showing the rate of change in capacitance after continuous durability tests of the capacitor of the present invention. FIG. 5: A diagram showing the survival rate after continuous durability tests of the capacitor of the present invention. FIG. 6: This figure FIG. 3 is a diagram comparing insulation resistance between the inventive capacitor and a conventional capacitor. Symbol, 1...Metalized film, 1a...Metal electrode, 1b...Irregularities, 2...Metallicon electrode, 3...
...Thermosetting resin, 4...Double-sided metallized film, 4
a...Metal electrode, 5...PET film, 5a...
...Unevenness.

Claims (1)

[Claims] 1. A metallized film capacitor comprising a wound type metallized film capacitor element whose dielectric is a polyethylene terephthalate film having a center line average roughness of 0.15 to 0.30 μm and impregnated with a thermosetting resin.