JPS6336679Y2 - - Google Patents

Description

[Detailed explanation of the idea]

This invention is a metallized film capacitor.
In particular, it prevents abnormal breakdown that occurs in the dielectric rear winding portion and stabilizes electrical characteristics such as capacitance and tanδ. Traditionally, most metallized film capacitors have been oil-immersed, and measures have been taken to reduce the tension during winding of the capacitor element to reduce oil flow resistance between film layers and improve impregnability. . Regarding the surface condition of the plastic film used as the dielectric, one surface is generally roughened to improve impregnability with insulating oil in conjunction with the above-mentioned winding tension adjustment. However, metallized film capacitors manufactured using these methods have many advantages in that they can take full advantage of the withstand voltage performance and corona resistance performance of insulating oil when the rated voltage is 500 VAC or higher.
In the low range of less than 500 VAC, there are dry type capacitors that are not impregnated with insulating oil, but this capacitor eliminates the need for the vacuum heating drying insulating oil impregnation process, making it possible to simplify and shorten the manufacturing process, and to This has the advantage of eliminating the need for additional equipment. However, on the other hand, it also has a drawback because it does not impregnate insulating oil between the film layers. That is, since the dielectric breakdown voltage of air is much lower than that of insulating oil, the corona onset voltage is lower in dry metallized film capacitors. In addition, partial breakdowns occur due to insulation defects contained in metallized films or plastic films, but generally, when a dielectric partially breaks down, the deposited metal scatters due to the energy, so it can occur in a very short time. Insulation performance is restored. However, when the tension during winding of the metallized film or the metallized film and the plastic film is small, there is a large amount of air space between the film layers, so that when the film partially breaks, the effect may be large and spread over a wide area. This tendency is particularly noticeable at the end of the winding of the capacitor element, and this was confirmed by disassembly of samples subjected to high-temperature continuous energization tests and high-temperature intermittent energization tests.
This is also supported by the fact that many large partial fractures of about 5φ are observed up to about 2m from the end of the dielectric roll. This phenomenon has a greater effect on the electrical characteristics of dry metallized film capacitors as the partial breakdown becomes larger, and may even lead to breakdown, or may cause damage to capacitors of the type with insulation margins provided at regular intervals along the width of the film. This may increase capacity reduction. The present invention aims to improve the instability of electrical characteristics caused by structural defects that appear in such dry metallized film capacitors. Specifically, an electrode dielectric of metallized film or metallized film and plastic film is wound with high tension, and when slowing down to wind the insulating film later, the insulation must be within 2 m from the end of the dielectric. It is coated with oil and then wound. According to this, it is possible to prevent many partial breakdowns occurring at the winding end portion of the capacitor element, and it is possible to obtain a metallized film capacitor with stable electrical characteristics. Hereinafter, the present invention will be explained in detail with reference to embodiments shown in the drawings. The figure is a perspective view of an embodiment of the present invention, in which 1 is a metallized film, 2 is an insulating oil layer, and a metalized polypropylene film 1 with an aluminum vapor-deposited film resistance of 6Ω/□ and a thickness of 9μ is wound to a certain length. After winding, when the winding speed is slowed down to rewind the insulating film, the metallized polypropylene film 1 is coated with alkylbenzene 2 to prevent it from leaking to the ends, and then the insulating film is re-wound. A capacitor element is formed by winding the capacitor element, a contact layer is formed by spraying metal on the end face of the element, an external lead terminal is connected to the contact layer, and the resulting metallized film capacitor is packaged with resin. As a test sample, the sample was subjected to an ambient temperature of 80℃ and a voltage of 560VAC for 2
As a result of applying the power intermittently 100,000 times with one cycle of ON for 2 seconds and OFF for 2 seconds, the values shown in Table 1 were obtained.

[Table] shows the distance from the end of the dielectric winding.
Similarly, the resistance value of the aluminum vapor deposited film is 6.
Ω/□, an insulation margin is provided in the width direction of the metallized polypropylene film 1 with a thickness of 9μ, and the width is
After winding the metallized film 1 with a pitch of 0.5 mm and 40 mm to a certain length, when slowing down to wind the insulating film later, the metallized polypropylene film 1 is made to prevent alkylbenzene from leaking to the ends. The capacitor element is formed by coating and winding, followed by winding an insulating layer, forming a contact layer by thermally spraying metal on the end face of the element, connecting an external lead terminal to the contact layer, and encasing the capacitor element with resin. The obtained metallized film capacitor was used as a test sample, and the test conditions were the same as those described above, and the results are shown in Table 2.

[Table] shows the distance from the end of the dielectric winding.
In addition, a corresponding conventional example is that in the above-mentioned embodiment, a capacitor element is formed by winding the metallized film 1 without applying an insulating oil such as alkylbenzene to the latter part of the winding part, and in the same manner as in the other embodiments. The length of the insulating oil coating used to construct the metallized film capacitor is 0 m. As a result, in all of the examples, the products of the present invention were able to have the same initial characteristics, a small decrease in capacity, and stable tan δ characteristics.
This is because, as mentioned earlier, in dry capacitors, the gap between the metallized film layers or the gap between the metalized film and the plastic film layer is larger than other parts, especially at the end of the winding, so it is more susceptible to partial breakdown when electricity is applied. Therefore, the capacitor element was wound with strong tension and an insulating oil, such as alkylbenzene, was applied to the end of the dielectric winding, and good results were obtained when the length was within 2 m from the end of the dielectric winding. The test was conducted on a round capacitor element, but it is not limited to this. For example, when a flat capacitor element is crushed, the air space between the metallized film layers or between the metallized film and the plastic film layer is reduced. In other curved parts, the number of air layers increases, resulting in the above-mentioned structural defects, especially at the end of the winding, and it is necessary to take the method of the present invention. Furthermore, although alkylbenzene was used as an example of the insulating oil applied to the end of the dielectric winding of the present invention, the same effect was obtained when other insulating oils were used. As described above, according to the present invention, abnormal breakdown occurring at the end of the dielectric winding can be prevented and electrical characteristics can be stabilized, which is economically effective.

[Brief explanation of drawings]

The figure is a partially exploded perspective view of the metallized film capacitor element of the present invention. 1...Metalized polypropylene film, 2...
Insulating oil layer.

Claims (1)

[Claims for Utility Model Registration] (1) A metallized film capacitor made of a metallized film or a metallized film and a plastic film, characterized in that an insulating oil layer is formed on the dielectric material at the end of the winding of the capacitor element. Metallized film capacitor. (2) The metallized film capacitor according to claim 1, wherein the dielectric material at the end of the winding of the capacitor element is coated with insulating oil within 2 m from the end.