JPS6146962B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a dry metallized film capacitor.

As is well known, dry-type metallized film capacitors are made by winding a plastic film with a metal film formed on its surface by vacuum evaporation so that the metal film forms a pair of opposing electrodes to form a capacitor element, and then applying metallized silicon to the end face of the capacitor element. At the same time, a lead wire is connected to the metallic contact portion.

In general, capacitor elements are designed to be insulated from the outside, to prevent deterioration over time due to environmental conditions surrounding the capacitor, for example, a decrease in dielectric strength due to moisture absorption, cooling of the constituent materials, and other effects such as ultraviolet rays and harmful gases. The exterior is installed to isolate it from the outside air. As for this exterior method,
A method of storing the capacitor element in a container made of metal or resin and sealing it, a method of wrapping the capacitor element with thermosetting or thermoplastic resin by dipping or molding, or a method of storing the element in a container made of metal or resin and sealing it, That is, a method of injecting and filling a thermosetting or thermoplastic resin around the capacitor element, and a method of wrapping an adhesive tape or the like around the outer circumference of the capacitor element and sealing the exposed part of the capacitor element with the resin. is taken.

In this way, the capacitor element is isolated from the outside air,
Although the negative effects of the surrounding environment of the capacitor are avoided, the interior of the capacitor element, that is, the space between each film layer, is not completely impregnated with synthetic resin even if the filling method is used, and air is trapped between the film layers and near the end face of the capacitor element. exists.

Therefore, the fatal defects of dry metallized film capacitors include a low corona discharge starting voltage due to the presence of the voids, and a decrease in capacitance due to this. For these reasons, the operating voltage of dry metallized film capacitors has been forced to be limited, even though the film has a high withstand voltage.

The present invention aims to eliminate such drawbacks of dry-type metallized film capacitors, and aims to increase the withstand power of the voids inherent in metallized film capacitor elements and increase the capacitor's corona discharge starting voltage. . As a means of doing so, when the capacitor element is covered with resin by methods such as dipping, resin filling, and molding,
The pressure inside the capacitor element is increased using the gas generated during the curing reaction of the resin.

That is, it utilizes carbon dioxide gas generated during the curing reaction of polyurethane resin. This polyurethane resin is obtained by the reaction of an alcohol having a difunctional hydroxyl group with an isocyanate, and this isocyanate releases carbon dioxide gas when it reacts with water.

The present invention utilizes carbon dioxide gas released by the reaction between isocyanate and moisture to increase the pressure in the voids within the capacitor element and improve the corona characteristics, which are disadvantages of dry metallized film capacitors. This suppresses the decrease in capacity that occurs.

Next, specific examples of the present invention will be described.

Example 1 As shown in FIG. 1, a metallized film capacitor element 1 made of a polypropylene film deposited with Al was placed in a container 2, and alcohol and isocyanate were placed in the container 2 with hydroxyl groups and isocyanate groups, respectively. The capacitor characteristics were studied for a capacitor in which an alcohol compound and an isocyanate compound were mixed in approximately equivalent amounts, and the mixed solution was injected and cured by heating to surround the polyurethane resin 3.

The metallized film capacitor element 1 is a 15 μF wound type capacitor element with a film thickness of 9 μm and a width of 60 mm, which is made by winding an Al-deposited metalized polypropylene film and applying metallicon on both end faces. The container 2 is large enough to accommodate the metallized film capacitor element 1, and is made of glass fiber-containing polybutylene terephthalate resin and has a thickness of 2 mm. Also, the amount of urethane resin 3 is 35g
It was hot.

Further, as the alcohol compound, castor oil polyol was used, and as the isocyanate compound, a urethane prepolymer consisting of castor oil polyol and organic diisocyanate was used, the blending ratio of both was 130 parts to 100 parts, and the water content was 500 ppm.
And so. Before mixing both, they were sufficiently degassed, and after they were mixed, they were degassed under vacuum, and when injected into the container 2, they were injected by vacuum injection.

The heat curing conditions were as follows: heat curing at 60°C for 1 hour, and further heat curing at 100°C for 1 hour. Note that heating was performed in an oven equipped with a fan.

As mentioned above, the alcohol compound and isocyanate compound are defoamed before mixing, vacuum defoamed after mixing, and then injected into the container by vacuum injection, so there is very little foaming during curing. There were no practical problems. Furthermore, although we did not measure the degree of increase in the internal pressure of the condenser, it is presumed that the pressure was extremely high due to the generation of carbon dioxide gas.

Corona discharge starting voltage and applied voltage of the metallized film capacitor whose outer periphery is covered with the polyurethane resin 3 in this way.
The change in capacitance after energizing at AC550V, 60°, for 1000 hours was compared with that using conventional epoxy resin. The results are shown in FIG.

Example 2 A metallized film capacitor element 1 using the same polypropylene film as in Example 1 was placed in the same container 2 as in Example 1, and 100 weight of the same solution was added to the solution used in Example 1 in the container 2. A solution containing 80 parts by weight of quartz powder was injected and cured in the same manner as in Example 1. The corona discharge starting voltage of this capacitor and the change in capacitance after energization were investigated in the same manner as in Example 1. The results are also shown in FIG.
The quartz powder had an average particle diameter of 6.7 μm and a water content of 0.02%.

Example 3 A metallized film capacitor element 1 using the same polypropylene film as in Example 1 was placed in the same container 2 as in Example 1, and 80 parts by weight of water was added to the solution used in Example 1 in the container 2. A solution containing Japanese alumina was injected and cured in the same manner as in Example 1. The corona discharge starting voltage of this capacitor and the change in capacitance after energization were investigated in the same manner as in Example 1. The results are also shown in FIG. Note that the hydrated alumina had an average particle diameter of 6.5 μm and a water content of 0.09%.

Example 4 Metallized film capacitor element 1 (20 μF) made of Al-deposited metalized polyethylene terephthalate film with a film thickness of 9 μm and a width of 60 mm.
was stored in the same container 2 as in Example 1, and an alcohol and isocyanate solution mixed with quartz powder was poured in according to Example 2, and the capacitor was cured by heating in the same manner, and the capacitor characteristics were examined. Comparison of the corona discharge starting voltage and capacitance of a metal polyethylene terephthalate film capacitor whose outer periphery of the capacitor element is covered with polyurethane resin and capacitance after 1000 hours of electricity applied at 300 VAC at 60°C with a capacitor using conventional epoxy resin. did. The results are shown in FIG.

As is clear from FIGS. 2 and 3, the metallized film capacitors of Examples 1 to 4 have significantly higher corona discharge initiation voltages and smaller capacitance reductions than those of commonly used epoxy resins. . During the curing reaction of a mixed solution of alcohol and isocyanate, the isocyanate reacts with the capacitor element material or moisture originally contained in the alcohol, and even with trace amounts of moisture present in the air during mixing and stirring, producing carbon dioxide gas. It is thought that this is the result of the air being released and diffusing inside the capacitor element, thereby increasing the air pressure between the film layers. That is, the polyurethane resin traps carbon dioxide gas produced by the reaction between isocyanate and moisture in the capacitor element during the curing reaction, and isolates it from the outside air while increasing the internal pressure of the capacitor element. Of course, the carbon dioxide gas released into the capacitor element is from the surface where the resin and the capacitor element are in contact, and the carbon dioxide gas released from the part of the resin exposed to the outside air is released into the outside air. .

Furthermore, as in Examples 2 and 3, if a filler such as metal oxide powder is mixed into the resin, the effect will be even greater. This is because metal oxide powder easily adsorbs water, and the reaction between that water and isocyanate releases more carbon dioxide gas.

Furthermore, using the capacitor element and polyurethane resin used in Examples 1 to 4, the same tests as in Examples 1 to 4 were conducted on the structure shown in FIG. 4, and almost the same results were obtained. In addition,
In FIG. 4, the container is constructed of polyester tape treated with an adhesive on one side.

Further, the polyurethane resin does not need to be in contact with the entire capacitor element, but may be in contact with at least a portion of the capacitor element. Furthermore, the heat curing conditions do not have to be those shown in the above examples.

As described above, according to the method of manufacturing a dry-type metallized film capacitor of the present invention, by bringing a metallized film capacitor element into contact with a polyurethane resin, the electrostatic capacitance that occurs during operation, which is the fate of dry-type metallized film capacitors, can be reduced. At the same time, it is possible to improve the corona discharge starting voltage and to set a rated voltage close to the original dielectric strength of the plastic film.
Its industrial potential is extremely high.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of one embodiment of a metallized film capacitor using the manufacturing method according to the present invention, and FIG.
3 and 3 are corona discharge start voltage and capacitance change rate characteristic diagrams of a capacitor according to the present invention and a conventional capacitor, respectively, and FIG. 4 is another example of a metallized film capacitor using the manufacturing method according to the present invention. FIG. 1... Capacitor element, 2... Container, 3... Polyurethane resin.

Claims (1)

[Claims] 1. A metallized film capacitor element is housed in a container, and a solution containing alcohol and isocyanate is injected into the container, and then the solution is heated and hardened to form a polyurethane material on the outer periphery of the metallized film capacitor element. A method for manufacturing a dry metallized film capacitor characterized by covering it with a resin.