JPH0143852Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to improvements in metallized film capacitors, and provides a metalized film capacitor with extremely high safety and reliability. Conventionally, metallized film capacitors are made of a plastic dielectric film such as polypropylene film, polyethylene terephthalate film, polystyrene film, or polycarbonate film, and a metal such as aluminum or zinc is provided at the widthwise end of the film with an insulating margin of 0.02 to 0.03. μm
A capacitor element is formed by winding a thick vacuum-deposited metallized plastic film so that the insulating margins face each other, and a contact layer is formed by thermally spraying metal such as solder or zinc on both end faces of the capacitor element. Lead wires or terminals were connected to the electrode lead-out portions obtained, and the metallized film capacitor was constructed by storing the capacitor in a case and sealing it. In a metallized film capacitor constructed in this manner, the metallized film may partially break down during a voltage test due to insulation defects contained within the plastic film or insulation defects formed during metal deposition. However, as the electrode is made of an extremely thin vacuum-deposited film as mentioned above, the energy of partial breakdown can cause the vapor-deposited metal layer to scatter, and generally the insulation recovers and the capacitor is then It becomes available for use. The effect of this partial destruction on the dielectric is slight at the initial stage, but continued partial destruction due to long-term use gradually deteriorates the dielectric, eventually causing it to catch fire and emit smoke. There was a danger that In order to improve these drawbacks, in the past, a pressure type fuse was used, or an insulating margin part 2 was provided on at least one side of the metallized film 1 at the end in the width direction to form an electrode 3 as shown in FIG. At the same time, an insulating groove 4 is provided so as to divide the metallized film 1 into a plurality of pieces in the length direction, and a safety function is provided to the capacitor element itself, in which the metallized film 1 is wound so that the insulating margin portions face each other. Metalized film capacitors have been proposed.
5 is an insulating film. In particular, the latter method has the advantage that the capacitor element itself has a safety function, which simplifies the structure and contributes to improved productivity. Since an insulating film is used at the end of the winding, it has the disadvantage that the capacity decreases greatly in the life test. That is, in the conventional structure, the insulating film has a dielectric strength between the inner layer and the outer layer at the beginning or the end of the winding, and when metal powder is sprayed during metallization,
In order to prevent the dielectric from being pushed down by air pressure, the dielectric film was wound so that the width was wider than the dielectric film width and the width was the same as the winding element width. The configuration shown in FIG. 1 has the disadvantage that the capacity decreases greatly in the life test. The present invention eliminates the above-mentioned drawbacks and provides a metallized film capacitor with stable electrical properties, especially capacitance, and safety. The present invention will be described in detail below based on examples. Figures 2 and 3 are exploded perspective views of the main parts of the metallized film capacitor element at the beginning and end of the winding, respectively, and 5 and 6 are the beginning and/or end of the dielectric winding. This is an insulating film that is wound with a part interposed between the films. In the figure, L ₁ is the width of the dielectric film winding element, and L _{2 is} the width of the dielectric film winding element.
indicates the insulation film width. An 8μ polypropylene film is used as the dielectric material, and an insulating margin part 2 is attached to this.
Aluminum was vacuum-deposited, leaving behind, and the resistance value of the deposited film was set to 3Ω/D. Metalized film capacitor samples with a rating of 350 V and 5 μF were prepared by fixing the wound element width L ₁ to a predetermined width and varying the insulating film width L ₂ . A life test was conducted, and the results of measuring and comparing the capacitance change rate (%) before and after the test and the tan δ (%) measured by applying the rated voltage at 75°C after the test are shown in the table. In the life test, an AC voltage of 1.2 times the rated voltage was continuously applied for 1000 hours at an ambient temperature of 80°C.

[Table] As a result, it is clear that the winding element width in this invention is
Dimensional difference between L ₁ and insulating film width L ₂ (L = L ₁ - _{L 2} )
By setting the value to 0.3 to 3 mm, we were able to suppress the decrease in capacity and stabilize the tan δ characteristics. If this dimensional difference L is less than 0.3 mm, the capacitance change rate will be large, and if it exceeds 3 mm, the above-mentioned tan δ will increase, which is not desirable. Although polypropylene film was used as the plastic film in the examples, other thermoplastic plastic films such as polyethylene terephthalate film or a combination of polypropylene film and polyethylene terephthalate film may be used, and the vapor-deposited metal is not particularly limited to aluminum. The same effect can be achieved with materials made of zinc or a composite of aluminum and zinc. Furthermore, although the above-mentioned embodiments have been described using a metallized film deposited on one side, it goes without saying that the same effect can be obtained even if a metallized film deposited on both sides is used. In addition, although the insulating film has been described as being used at the beginning and end of winding, it is not applied to either the beginning or the end of winding, and the evaporated electrode is removed, and the dielectric film is You may also wind the wire only. As described above, the metallized film capacitor of the present invention has electrical properties, especially a self-protection function, stable capacitance in life tests, and can be used at high potential gradients, resulting in miniaturization and high reliability. can be realized and is extremely beneficial.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view of essential parts of a conventional metallized film capacitor element, and FIGS. 2 and 3 are exploded perspective views of essential parts of an embodiment of the metallized film capacitor element of the present invention. 1: metallized film, 2: insulation margin part,
3: Electrode, 4: Insulating groove, 5, 6: Insulating film,
L ₁ : Winding element width, L ₂ : Insulating film width.

Claims (1)

[Claims for Utility Model Registration] (1) An electrode is formed by providing an insulating margin at the end of at least one side of the film in the width direction, and an insulating groove is provided in at least a part of at least one side of the electrode, and A metallized film capacitor formed by winding a metallized film divided into a plurality of pieces so that the insulating margin parts face each other, forming electrode extension parts at both ends of the metallized film to form a capacitor element, and packaging the capacitor element. In,
The width of the insulating film that is wound with a part interposed between the films at the beginning of winding of the dielectric, the end of winding, or both is configured to be narrower than the width of the winding element of the dielectric film. A metallized film capacitor characterized by: (2) The dimensional difference between the winding element width and the insulation film width is
The metallized film capacitor according to claim 1, wherein the metallized film capacitor has a diameter in the range of 0.3 to 3 mm. (3) The metallized film capacitor according to claim 1, wherein the dielectric of the metallized film is made of polypropylene, polyethylene terephthalate, or a combination thereof. (4) The metallized film capacitor according to claim 1, wherein the metallized electrode of the metallized film is made of aluminum, zinc, or a composite thereof.