JPH025285B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to metallized film capacitors. Aluminum metallized polypropylene film (hereinafter referred to as
A capacitor using AlMPP) is used. As film production technology and vapor deposition technology progress, the potential gradient is increasing year by year, and the transition to dry type capacitors is progressing. Especially wet
In AlMPP capacitors, the aluminum vapor-deposited metal 1 undergoes an electrochemical reaction as shown in Figure 1 due to an increase in the amount of corona due to the increase in potential gradient, moisture contained in the capacitor insulating oil and film itself, dissolved oxygen contained in the insulating oil, etc. (corrosion) and becomes aluminum oxide (Al ₂ O ₃ )2. The aluminum oxide portion 2 in the state shown in FIG. 1 grows depending on the voltage application time. Al ₂ O ₃ is an insulating material, so the capacitance of the capacitor decreases. Furthermore, in the AlMPP capacitor, the distance indicated by arrow D in Fig. 2 is the shortest distance between different poles, and the corona electric field is also the most severe. Due to this reason, it oxidizes to become Al ₂ O ₃ and is further scattered, causing the margin width to recede as shown in FIG. 1, and the margin width A expands to B. In other words, the capacitance of the capacitor decreases. 3 is a polypropylene film, 4 is a metallicon portion, and D is a film width. The above-mentioned corrosion phenomenon on the electrode plane,
Two phenomena, corrosion in the margin and scattering of aluminum-deposited metal, increase the reduction in capacitance of the capacitor. These phenomena occur even more severely in dry capacitors, and the capacitance decrease becomes very large. Furthermore, it is generally said that this corrosion phenomenon can be suppressed by using a metalized polypropylene film in which zinc metal is vapor-deposited. Metallized polypropylene film with membrane resistance (hereinafter referred to as
When ZnMPP is subjected to intermittent durability tests and continuous durability tests as described in JIS4908, corona occurs between different poles indicated by arrow D as shown in Figure 3. Reference numeral 6 indicates a metallicon portion, and reference numeral 7 indicates a deteriorated portion of the polypropylene film 3. For this reason
As mentioned above, in the AlMPP capacitor, due to the scattering of aluminum metal and the change to Al ₂ O ₃ , the distance between different electrodes shown by arrow D increases and the capacitance decreases, but the polypropylene film 3 that is the base film Since it had almost no effect, there were no problems in terms of quality other than a decrease in capacity. But 2~
In a ZnMPP capacitor with a film resistance value of 5Ω/□, the zinc evaporated metal 5 is less likely to scatter, so the generated corona will concentrate on the boundary line between the zinc evaporated part and the margin, and as a result, the base film As shown in Figure 3, the polypropylene film 3 deteriorates due to corona, resulting in a significant increase in loss in the capacitor, which can lead to abnormal breakdown and punctures. Also, zinc is sensitive to moisture, which can cause problems during the manufacturing process. ZnMPP has not been used due to two major drawbacks: The present invention overcomes the above-mentioned drawbacks and provides a highly stable ZnMPP capacitor of quality with less capacitance loss than AlMPP capacitors. That is, it has a membrane resistance value of 6 to 10Ω/□.
This problem could be solved by using ZnMPP and by heat treating the finished product. That is,
The film resistance value of the zinc-deposited metal 5 shown in FIG.
By setting the resistance to 10 Ω/□, it was possible to prevent abnormal destruction by causing some scattering of the zinc metal film and gradually moving the corona that corresponds to the base film under the border between the margin and the zinc evaporated film. This idea is similar to the regression phenomenon of aluminum, but in the case of aluminum, the capacitance decrease was large because the Al ₂ O ₃ insulator was larger, and in the case of zinc, the film resistance was 6 to 10 Ω/□ By doing so, the margin width is limited to a setback, that is, there is no corrosion phenomenon at the margin portion, and no corrosion phenomenon occurs at the flat portion. Further, if the resistance value of the zinc-deposited film exceeds 10Ω/□, the contact resistance in the metallized contact portion 4 increases, the loss increases, and the quality becomes unstable. Basically, heat treatment is not necessary, but in order to further stabilize the capacity, it is better to perform heat treatment at 90 to 100°C for 2 hours or more. At this time, after packaging the product by storing it in a case, the completed product is also tested for sealing. The reason for this is that the zinc evaporated film is weak against moisture, so if a large amount of ZnMPP elements and capacitors are heat treated or heated and vacuum treated at once, the inside of the element becomes evaporated due to the difference in temperature distribution and vacuum degree distribution, and the zinc evaporated film The metal disappears, causing an increase in loss. If carried out on a finished product, the effect will be limited to the moisture content inside a single capacitor, and will not be affected by moisture from other elements or manufacturing conditions, and the moisture content of ZnMPP itself will be 0.02%.
This is because the amount of zinc evaporated metal is so small that almost no disappearance of the zinc-deposited metal is observed. Next, zinc (Zn) and aluminum (Al) are vapor-deposited on polypropylene to change the film resistance and classify them.
We fabricated AlMPP and ZnMPP capacitors and conducted durability tests. Table 1 shows the results of an intermittent durability test in which an AC voltage of 1.4 times WV was intermittently applied to each sample at 80°C. In addition, Table 2 shows WV × at 80℃
The results of a continuous durability test in which 1.2 times the AC voltage was continuously applied to each sample are shown. The number of samples was 10 each.
Measured values are average values. In the table, sample numbers 2, 8, 12, and 18 are products of the present invention, and the others are samples for comparison, and tan δ is a value measured by applying the rated voltage at 75°C.

【table】

【table】

[Table] This shows that for AlMPP products, there is no change in loss in both dry and wet processes, but the capacity reduction is clearly large. In addition, in ZnMPP, the capacitance decrease is very small, but if the membrane resistance value is less than 2 to 6 Ω/□, loss increases and punctures occur, but in the 6 to 10 Ω/□ product, which is the product of the present invention, it is very small. It shows stable characteristics. Also, the membrane resistance exceeds 10~15Ω/
The ZnMPP product with □ is relatively stable in terms of quality, but the loss of the initial value is large and there are problems with the advanced film control technology during vapor deposition, resulting in a stable 10 to 15 Ω/□. In addition to the difficulty in obtaining ZnMPP, there is also the difficulty in achieving product stability during mass production. As described above, the present invention makes it possible to obtain a very stable capacitor with little loss fluctuation and capacitance reduction, and is of great industrial and practical value.

[Brief explanation of drawings]

Fig. 1 is a plan view of the main part of the electrode of a conventional metallized film capacitor having an aluminum metallized film, Fig. 2 is a cross-sectional view of the main part of the electrode of the conventional metallized film capacitor, and Fig. 3 is a zinc-deposited film. FIG. 4 is a sectional view of a main part of an electrode of a metallized film capacitor with a thin thickness. FIG. 3: Polypropylene film, 4, 6: Metallicon portion, 5: Zinc-deposited metal.

Claims (1)

[Scope of Claims] 1. A metallized film capacitor in which an electrode is formed by vapor-depositing a metal on a polypropylene film, which is wound or laminated, and the end of the electrode is covered with metallized to form an electrode part, The vapor-deposited metal is made of zinc, and the vapor-deposited metal has a resistance of 6 to 6.
A metallized film capacitor characterized by a resistance within the range of 10Ω/□. 2. Claim 1, characterized in that the metallized film capacitor is heat treated after being packaged.
Metallized film capacitors as described in .