JPH0510811B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to resin-clad metallized film capacitors.

Conventional configurations and their problems In recent years, the trend toward miniaturization, high reliability, and labor-saving of electrical components has become a variety of important factors. Capacitors for electrical equipment have also improved in performance by improving dielectric materials, electrode materials, exterior materials, etc. Among them. Containers using resin-clad metallized films can be manufactured in a labor-saving manner.
Due to its excellent electrification characteristics, it has come to be applied in various fields.

First, the conventional structure of a resin-clad metal film capacitor will be explained.

FIG. 1 shows a cross-sectional view of a conventional resin-clad metallized film capacitor. 1 in Figure 1
2 is a metallized film, 2 is a dielectric film, 3 is a metallicon for the purpose of drawing out electrodes, 4 is a terminal, and 5 is a metallized film.
6 is an external case, and 6 is a volume resistivity value of 10 ¹² ~
10 ¹⁵ Ω/cm ³ casting resin such as epoxy resin or urethane resin, intended for fixing capacitor elements, insulating them, and shielding them from the outside air.

A conventional problem with resin-clad metallized film capacitors having such a configuration is a reduction in capacitance due to oxidation and scattering of the vapor deposited film of the metallized film 1 caused by long-term voltage application. The possible reason for this is that the air layer, moisture, etc. existing between the metallized films 2 react with the deposited metal under a high electric field and oxidize the deposited film, resulting in a decrease in the electrode area of the capacitor. . In addition, the electric field tends to concentrate in high electric field areas, such as the margins of vapor-deposited electrodes, at the edges of the electrodes, so partial discharges occur in these areas, and the discharge energy scatters the vapor-deposited metal.
The electrode area decreases, which manifests itself as a decrease in capacitance.

Therefore, in order to prevent such a decrease in capacitance, the capacitor element is impregnated with oil or wax, and the air layer between the films is replaced with oil or wax, thereby reducing the influence of air and preventing partial discharge. Some attempts have been made to prevent capacitance reduction by increasing the starting voltage. However, with the above method, oil or wax is not sufficiently impregnated between the film layers, or even if it is impregnated, there is only a small oil layer, and when a long-term durability test is performed, the oil layer may be damaged due to temperature changes or mechanical vibrations. There is a phenomenon in which the partial discharge inception voltage gradually decreases during service life, and the results of long-term durability tests show that the capacitance tends to decrease, similar to non-impregnated metallized film capacitors. Ta.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a resin-clad metallized film capacitor that shows extremely little decrease in capacitance during long-term durability tests.

Structure of the Invention The resin-clad metal film capacitor of the present invention includes:
The metallized film capacitor element is cast or molded in a resin with a volume resistivity of 10 ⁴ to ^{10 10} Ω/cm ³ , and the capacitor element is wrapped in a resin with a lower volume resistivity than conventional ones to increase the capacitance. It is characterized by preventing the decrease.

More specifically, the electric field near the margin of the vapor deposition electrode, which is the biggest cause of capacitance change during long-term voltage application, is alleviated by using a resin with a low volume resistivity.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

Here, a 10 μF element was fabricated as a capacitor using a 5 μm polyester metallized film and a 5 μm polypropylene dielectric.
Epoxy resin is used as the casting resin, and in order to change the volume resistivity value, titanium coupling agent is mixed as a low resistance mixture, resulting in 10 ² , 10 ⁴ , 10 ⁶ , 10 ⁸ , a casting resin having a volume resistivity of 10 ¹⁰ Ω/cm ³ was obtained. A resin-clad capacitor as shown in Fig. 1 is made by casting the above-mentioned elements with resins having respective volume resistivity values.
A long-term continuous test was conducted to determine the rate of change in capacitance. Figure 2 shows the results of this test. The test conditions are
This is the rate of change in capacitance after 1000 hours at 260 VAC and 70°C. Conventional molding resin using epoxy resin has a resistance of about 10 ¹⁴ Ω/ ^cm3 , but when using that resin, △C/C (capacitance change rate) is -4%, whereas the volume specific It can be seen that when a resin with a low resistance value is used, ΔC/C gradually decreases. However, when the resistance value reached approximately 10 ² Ω/cm ³ , the capacitor lost a lot and generated significant heat due to the almost low resistance value, causing destruction. However, if it was 10 ⁴ Ω/cm ³ or more, the loss was small enough to withstand practical use.

In order to further enhance the above-mentioned effect, Figure 3 shows the result of resin casting under pressurized or reduced pressure conditions so that the low-resistance resin penetrates into the vicinity of the margin of the metal film. It is a capacitance change graph showing the results of a long-term continuous durability test of a capacitor in comparison with a conventional capacitor. 10 ¹⁰ Ω/cm ³ was used as the casting resin, and the capacitor element was the same as the one described above. The most effective method is vacuum casting. This is because the air layer inside the element is reduced by reducing the pressure, and the force of the reduced pressure guides the casting resin closer to the margin, eliminating the air layer that causes the capacitance to decrease. This is because the two elements that lead the casting resin to the vicinity of the margin become bulky. Moreover, casting under pressurized conditions is for press-fitting the casting resin by applying pressure to the vicinity of the margin.

In the above embodiment, the effect was confirmed using a resin-casting type capacitor, but it goes without saying that the same thing can be said about a resin-molding type capacitor.

Effects of the Invention As described above, the resin-clad metallized film condenser of the present invention uses a resin for casting or molding that has a volume resistivity of 10 ⁴ to ^{10 10} Ω/cm ³ , which is lower than conventional ones. This makes it possible to extremely reduce the rate of change in capacitance during long-term durability tests of resin-clad film capacitors, and it is possible to achieve even greater effects by casting under pressurized conditions or under reduced pressure. It became. As a result, highly reliable and low-cost capacitors can be obtained, which has great effects.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a resin-clad metallized film capacitor, Figure 2 is a characteristic diagram of the volume resistivity of the casting resin and the rate of change in capacitance in a long-term durability test, and Figure 3 is a graph showing the characteristics of the casting resin under pressurized conditions. FIG. 3 is a characteristic diagram of the capacitance change rate in a long-term continuous durability test showing the effects of the mold and vacuum casting. 1...metalized film, 2...dielectric film, 6...casting resin.

Claims (1)

[Claims] 1. A resin-clad metallized film capacitor in which a metallized film capacitor element is cast or molded with a resin having a volume resistivity of 10 ⁴ to ^{10 10} Ω/cm ³ . 2. The resin-clad metallized film capacitor according to claim 1, wherein the metallized film capacitor element is pressure cast or reduced pressure cast.