Fuse

Abstract

To provide a fuse which allows increase of a shut-down current and reduction of the size and also reduces the insulation performance at the time of shutting-down.SOLUTION: A fuse 1 includes: a fuse element 7; a case (an external container) 15 for storing the fuse element 7; and arc extinguishing sands 3 filled in the space of the case 15. In the present invention, a silicone oil 6 with a viscosity which permeates among the arc extinguishing sands 3 fills the inside of the case 15.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a fuse in which the space inside a case housing an electric conductor is filled with arc-extinguishing sand as an arc-extinguishing agent. [Background technology]

[0002] Japanese Patent Laid-Open Publication No. 2018-152359 (Patent Document 1) discloses a fuse in which the space inside a case that houses a conductor is filled with arc-extinguishing sand.

[0003] Furthermore, Japanese Utility Model Publication No. 53-86527 (Patent Document 2) discloses a fuse that does not use arc-extinguishing sand, which is placed in insulating oil in an oil-filled electrical device and has a through hole formed in the case to allow the insulating oil to penetrate into the case in which the conductor is placed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-152359 A [Patent Document 2] Japanese Utility Model Application Publication No. 53-86527 Summary of the Invention [Problem to be solved by the invention]

[0005] In order to miniaturize a fuse in which arc-extinguishing sand is filled in the case for arc-extinguishing and to increase the breaking current, it is necessary to suppress heat generation due to the arc during interruption. However, since the arc-extinguishing sand alone cannot improve the cooling performance as in the fuse shown in Patent Document 1, it is difficult to miniaturize the fuse and to handle a large breaking current. In the fuse shown in Patent Document 2, it was expected that the arc current would be extinguished in a short time by the cooling effect of the insulating oil. However, the insulating oil in the oil-filled electrical device is carbonized due to the high heat caused by the arc current, and if the amount of carbonization becomes too large, there is a problem that the insulating performance during interruption will be reduced.

[0006] An object of the present invention is to provide a fuse which allows for a smaller size and a larger breaking current, without deteriorating the insulating performance during breaking. [Means for solving the problem]

[0007] The fuse of the present invention comprises a conductor, a case for accommodating the conductor, and arc-extinguishing sand filled in the space inside the case, and the case is filled with silicone oil having a viscosity that allows it to penetrate between the arc-extinguishing sand. According to the present invention, the cooling performance is improved by the silicone oil, which is less likely to carbonize than the insulating oil of oil-filled electrical equipment, and the arc-extinguishing performance of the arc-extinguishing sand can be maximized. Therefore, according to the present invention, it is possible to both reduce the size of the fuse and increase the breaking current without reducing the insulating performance during breaking.

[0008] Specifically, the arc-extinguishing sand is SiO2, and the silicone oil is preferably dimethyl silicone oil, which among various silicone oils can maintain its liquid state even if slight carbonization occurs, and can ensure insulation performance.

[0009] It goes without saying that the fuse of the present invention can be placed in insulating oil and used in oil-filled electrical equipment. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a vertical cross-sectional view of the fuse of the present embodiment. [Diagram 2] (A) shows the test results (breaking current waveform) of a fuse whose outer container is filled with silicone oil, and (B) shows the test results (breaking voltage waveform) of a fuse whose outer container is filled with silicone oil. [Diagram 3] (A) shows the test results (breaking current waveform) of a conventional fuse whose outer casing is not filled with silicone oil, and (B) shows the test results (breaking voltage waveform) of a conventional fuse whose outer casing is not filled with silicone oil. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the fuse of the present invention will be described in detail with reference to the drawings.

[0012] 1 is a vertical cross-sectional view of a fuse 1 according to the present embodiment. The fuse 1 according to the present embodiment includes an insulating cylindrical body 5 filled with arc-extinguishing sand 3, and an outer container (case) 15 consisting of a pair of cap-shaped electrodes 9 and 11 fitted to both ends of the cylindrical body 5 and electrically connected to a fuse element (conductor) 7. In the present embodiment, the arc-extinguishing sand 3 is SiO2.

[0013] The cylindrical body 5 is integrally formed from ceramic. The cap-shaped electrodes 9 and 11 have bottom wall portions 9A and 11A facing the openings 51 and 53 of the cylindrical body 5, and cylindrical peripheral wall portions 9B and 11B extending upright from the peripheral edges of the bottom wall portions 9A and 11A. The inner wall surfaces of the bottom wall portions 9A and 11A of the cap-shaped electrodes 9 and 11 facing the openings 51 and 53 of the cylindrical body 5 are covered with an insulating material 13 having electrical insulation properties made of aramid paper.

[0014] A silicone adhesive is applied to bottom wall portions 9A and 11A of the pair of cap-shaped electrodes 9 and 11, and the inside of the outer container 15 is kept liquid-tight by fitting the electrodes into the cylindrical body 5. The structure for making the outer container liquid-tight is arbitrary.

[0015] Silicone oil 6 is filled in the liquid-tight exterior container 15. The silicone oil 6 used in this embodiment has a viscosity that allows it to penetrate between the arc-extinguishing sand 3. The preferred viscosity μ is 100 to 1000 m 2 / s. More specifically, the silicone oil 6 is preferably a high-temperature, sealed dimethyl silicone oil sold by Shin-Etsu Chemical Co., Ltd. under the product name "KF-96-20cs". Of course, other silicone oils than "KF-96-20cs" can also be used in the present invention as long as they have a viscosity that allows them to penetrate between the arc-extinguishing sand.

[0016] The fuse element 7 is integrally formed by pressing an elongated metal plate for fuses made of silver or copper. The fuse element 7 is configured by three melting parts 71A to 71C and four non-melting parts 73A to 73D arranged alternately along an imaginary center line L1. Each of the melting parts 71A to 71C is configured by a pair of notches 72A, 72A formed on the edge part 7a of the fuse element 7, and a remaining part 72C, 72C of a circular hole part 72B formed between the pair of notches 72A, 72A, on either side of the imaginary center line L1. The remaining parts 72C, 72C have a narrower width dimension than the non-melting parts 73A to 73D, and therefore have a higher electrical resistance than the non-melting parts 73A to 73D, and are more likely to melt than the non-melting parts 73A to 73D.

[0017] Of the four non-fusible portions 73A to 73D, non-fusible portions 73B and 73C located in the central region are formed with two grooves 72D extending in the width direction.

[0018] Next, to confirm the breaking performance, a comparison test was conducted on a fuse 1 in which silicone oil 6 was filled in the outer container 15 and a fuse in which silicone oil was not filled. Figures 2(A) and 2(B) show the test results for fuse 1 in which silicone oil 6 was filled in the outer container 15, with Figure 2(A) showing the breaking current waveform (current [A]-time [ms]) and Figure 2(B) showing the breaking voltage waveform (voltage [V]-time [ms]).

[0019] Figures 3(A) and 3(B) show the test results of a conventional fuse in which silicone oil is not filled inside the outer casing. Figure 3A shows the breaking current waveform (current [A]-time [ms]), and Figure 3(B) shows the breaking voltage waveform (voltage [V]-time [ms]).

[0020] Comparing the two, no significant difference is observed in the interruption voltage waveforms [Fig. 2(B) and Fig. 3(B)], but a significant difference is observed in the interruption current waveforms [Fig. 2(A) and Fig. 3(A)]. That is, in Fig. 3(A), after an arc current of about 600A flows in 5ms, the arc current falls slowly, and the time (time required for interruption) t during which the arc current continues is long (the arc current continues even after 10ms has passed). In contrast, in Fig. 2(A), after an arc current of about 600A flows in 5ms, the arc current falls quickly, and it can be seen that the interruption performance is improved. This shows that the silicone oil 6 filled in the outer container 15 is not carbonized by the arc current, and the arc current can be extinguished in a short time due to the cooling effect of the silicone oil 6. In the case of the fuse of this embodiment, a voltage was applied for 5 minutes after the interruption, but no voltage drop was observed during that time, and no continued rise in the fuse temperature was observed. Furthermore, when the fuse was dismantled, the arc-extinguishing sand other than that around the fuse element 7 had not turned black, which suggested that there had been substantially no carbonization of the silicone oil.

[0021] In addition, when a similar reference test was performed by putting Shell transformer oil in the case instead of silicone oil, while continuing to apply the specified voltage after the cutoff, the voltage dropped, the fuse temperature rose, and the outer casing cracked. It is presumed that this is because the Shell transformer oil was carbonized by the heat at the time of the cutoff, causing a small amount of current to continue to flow, causing a rise in temperature, and the case cracked due to thermal shock. From this reference test, it was confirmed that silicone oil is the preferred oil to use.

[0022] The above embodiment is described as an example, and the present invention is not limited to this embodiment as long as it does not deviate from the gist of the present invention. For example, in the above embodiment, the outer container is made liquid-tight and filled with silicone oil, but a non-liquid-tight fuse may be disposed inside an insulating device filled with silicone oil, and the inside of the outer container may be filled with silicone oil. [Industrial Applicability]

[0023] According to the present invention, it is possible to provide a fuse that allows for miniaturization and a large breaking current, without deteriorating the insulating performance during breaking. [Explanation of symbols]

[0024] 1. Fuse 3. Arc-extinguishing sand 5 Cylinder 6. Silicone Oil 7 Fuse Element 71A to 71C Melted parts 73A to 73D Non-melting parts 9,11 Cap-shaped electrode 13 Insulating materials 15 Outer packaging

Claims

1. A fuse comprising a conductor, a case for accommodating the conductor, and arc-extinguishing sand filled in a space within the case, A fuse characterized in that the case is filled with silicone oil having a viscosity that allows it to penetrate between the arc-extinguishing sand particles.

2. The arc-extinguishing sand is SiO 2 and 2. The fuse of claim 1, wherein the silicone oil is a dimethyl silicone oil.

3. 3. An oil-filled electrical device comprising the fuse according to claim 1 or 2 disposed in insulating oil.

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