JPS6210983Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a resin-filled capacitor with a current fuse provided with a current fuse as a safety device.

Generally, in most capacitors, dielectric breakdown occurs due to deterioration of the dielectric material that is a component of the capacitor element, resulting in a short circuit, but this invention provides more complete safety for this type of capacitor. This is an attempt to shut off the fuse as a device.

That is, in general, in the above-described type of capacitor, when the capacitor breaks down, the dielectric material decomposes at the same time as the dielectric breakdown occurs, and gas is rapidly generated, and the internal pressure increases, causing the filled resin and the container to rupture and catch fire. Conventionally, in order to prevent the above-mentioned accidents, some conventional capacitors have a current fuse connected in series with the capacitor element, and the fuse is cut off by the short-circuit current of the capacitor element, but naturally the amount of gas generated is It has no effect unless the current fuse is shut off before the explosive amount is reached. As mentioned above, the amount of gas generated by the decomposition of the dielectric increases rapidly, and the strength of the container becomes unbearable, and the container may be destroyed within the time it takes for the fuse to melt and shut off. Conventional resin-filled capacitors with current fuses have the disadvantage of being unreliable as safety devices.

It is an object of the present invention to eliminate the above-mentioned conventional drawbacks and to provide a resin-filled capacitor with a current fuse that operates reliably.

The feature of the present invention is that when the capacitor element is destroyed, a space is formed on both end faces of the capacitor element, and this space is communicated with the cavity in the winding core to form a communication space. At the same time, the decomposition gas generated by decomposition is stored in the space, and the core is deformed inward by the gas pressure of the decomposition gas, so that the container can withstand explosion until the current fuse is cut off. The point lies in the structure.

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, 1 is a metallized film capacitor element, 2 is a cylindrical winding core made of thermoplastic resin and open at both ends, 3 is a current fuse connected in series with the capacitor element 1, 4 is a filled resin, and 5
Numerals a and 5b are lead wires for electrically connecting the capacitor element 1 and the terminal 7, 6 is a synthetic resin container, and 8 is a closed-cell foam made of a polymeric material.

Since the closed cell foam 8 has independent cells, the resin 4 filled in the synthetic resin container 6 does not enter the closed cell foam 8. Therefore, a cavity sealed by the closed-cell foam 8 is formed within the core 2 .

Generally, when a capacitor element breaks down, that is, when decomposed gas is generated from the dielectric material that is a component of the capacitor element, the decomposed gas passes between the dielectric materials and has a higher strength than in the outer circumferential direction of the capacitor element, which is stronger. It is most likely to escape in the direction of the end face of the capacitor element, which is vulnerable to damage, passing through the contact gap between the capacitor element and the filling resin, gradually increasing the decomposed gas pressure, and attempting to rupture the part where the exterior strength is weakest.

In this example, a closed-cell foam 8 made of a polymeric material having a heat resistance of about 80 to 150 degrees Celsius is attached to the end face of the capacitor element 1 using an adhesive or the like, and the winding core 2 is not broken by the capacitor element 1. By being made of a thermoplastic resin material that deforms in shape in response to the heat generated and decomposed gas pressure, the decomposed gas when the capacitor element 1 breaks is transferred from the end face of the capacitor element 1 to the closed cell foam 8, which is weak in strength. Due to its high temperature and rapid generation, the decomposed gas instantly melts or breaks through the walls of each cell in the closed cell foam 8, instantly creating a space at the end face of the capacitor element 1. In addition to forming
A communication space is formed by communicating this space with the cavity in the winding core 2, and the cracked gas can be temporarily stored in the communication space. At the same time, since the winding core 2 is thermoplastic, the winding core 1 can be deformed inward by the heat generated and gas pressure when the capacitor element 1 breaks down, and by the thermal contraction of the dielectric of the capacitor element 1, thereby alleviating the increase in cracked gas pressure. can do. Therefore, the synthetic resin container 6 can withstand the decomposition gas pressure generated by the capacitor element 1 until the current fuse 3 is interrupted by the short circuit current. FIG. 2 shows the state when the capacitor element 1 of the resin-filled capacitor with current fuse of this embodiment is destroyed.

Figure 3 is a graph showing the relationship between decomposition gas pressure and decomposition gas pressure over time until the capacitor breaks down. Breakdown starts at origin O, dielectric breakdown occurs, and a short circuit occurs.
The current fuse breaks at time T _O . Figure 3b
is the decomposed gas pressure in the conventional capacitor, c is the decomposed gas pressure in the capacitor of this embodiment, and d is the fuse current. Note that the broken line a in FIG. 3 shows the short circuit current when no current fuse is provided.
At this point, decomposition gas from the dielectric material is rapidly generated, and the gas pressure
The container explodes between Pa and Pb. In conventional resin-filled capacitors with current fuses, the time T _1-a
The container 6 explodes between ~ _T1-b . Therefore, time T _O >T _1-a , and in the conventional example, current fuse 3
The container 6 may explode before it is shut off. In the experiment, 20 containers 6 out of 50 exploded with capacitors rated at 200V and 30μF. On the other hand, the first
In the capacitor of this embodiment shown in the figure, the time T _2-a
It explodes between ~T _2-b (>T _O ). Therefore, in the case of this example, fuse 3 broke before container 6 exploded in all 50 out of 50 units in a similar experiment.

As described above, the resin-filled capacitor with a current fuse according to the present invention has a closed-cell foam attached to both end faces of the capacitor element and both end faces of the winding core, and a cavity is formed in the winding core, thereby making it possible to create a current fuse. The gas pressure of the decomposed gas generated by the capacitor element can be temporarily relieved until the fuse is cut off, and the current fuse is cut off before the container explodes.
It is possible to prevent the risk of fire in advance and reliably.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a capacitor in an embodiment of the present invention, Fig. 2 is a cross-sectional view showing the state when the capacitor element of the capacitor breaks down, and Fig. 3 shows the time taken for the capacitor to break down. FIG. 3 is a characteristic diagram showing the relationship with gas pressure. DESCRIPTION OF SYMBOLS 1... Capacitor element, 2... Winding core, 3... Current fuse, 4... Filled resin, 6... Synthetic resin container, 8... Closed cell foam.

Claims (1)

[Scope of utility model registration request] A capacitor element is provided around a cylindrical core with both ends open, and both ends of the core and both ends of the capacitor element are covered with closed cell foam to form a cavity within the core, and the capacitor element is A current fuse is connected in series with the core, the capacitor element, the closed cell foam, and the current fuse are housed in a container, and the container is filled with resin.