JPS6226132B2 - - Google Patents

Description

Detailed Description of the Invention This invention reduces the arc cross-sectional area by confining the arc that is generated when a short circuit current or overcurrent flows through a fusible piece and causes the fusible piece to melt, in a slit formed by a solid insulator. This invention relates to a slit-type current-limiting fuse that suppresses the spread of water and exhibits high current-limiting performance.

Conventional current-limiting fuses have a fusible piece inserted into an arc-extinguishing material such as silica sand, and when the fusible piece fuses due to overcurrent, the arc is diffused and extinguished within the arc-extinguishing material to limit current and break the fuse. It was hot. However, since arc-extinguishing materials such as silica sand are porous, there are many voids, and the arc generated during current limiting diffuses within these voids and expands the cross-sectional area, suppressing the increase in arc resistance and making it an excellent material. However, it was not possible to obtain the desired current-limiting characteristics.

In order to improve the current-limiting characteristics of the above-mentioned slit-type current-limiting fuse, the prior art has developed a structure in which a slit is formed in a solid insulator and a fusible piece is inserted into this slit to conduct electricity. something was developed.

One example is a slit-type current-limiting fuse as shown in FIGS. 1 and 2. As shown in the figure, this slit-type current-limiting fuse uses solid arc-extinguishing insulators 1, 2a, and 2b made of inorganic, organic, or a mixture thereof, with a slit 3 formed between them. ing. A fusible piece 4 having a notch portion 4a is provided within this narrow gap 3, and the insulating plates 2a and 2b are fastened to the insulating plate 1 with screws 5 to form a groove 6 between the insulating plates 2a and 2b. Electrode terminals 7 are connected to both ends of the fusible piece 4, and the electrode terminals 7 are attached to the insulator 2 with screws 8. Such an assembly is housed in a fuse tube 9, with only both electrode terminals protruding from the fuse tube, and the fuse tube is filled with granular insulator 10, which is an arc-extinguishing material.

When an overcurrent flows through the slit-type current-limiting fuse constructed as described above, the fusible piece 4 is first fused at the notch portion 4a, and an arc is generated. This arc is caused by a narrow gap 3 formed between the insulating plate 1 and the insulating plates 2a and 2b.
The arc is confined within the arc, its cross-sectional area is limited, and it is cooled by the insulating plates 1, 2a, 2b, resulting in a significant increase in arc resistance and limiting the overcurrent. on the other hand,
The inside of the slit 3 is filled with high-temperature, high-pressure metal vapor generated by the arc, but since the insulating plate is provided with a groove 6 that communicates the slit with the outside, the metal vapor does not pass through the groove 6. The metal vapor diffuses outside the slit 3, and the high temperature and high pressure inside the slit is relieved. At the same time, the metal vapor is cooled and condensed by the granular insulator 10 outside the slit, resulting in excellent current limiting and It is possible to obtain cutting performance.

In this way, the granular insulator 10 only contributes to cooling the high-temperature metal vapor, so conventionally, the granular insulator 10 has a particle size ranging from ultra-fine particles in the form of fine powder to mesh #5 (number of meshes per inch = 5). considered to be applicable. However, if the particles are too small, the space will be narrow, and the vapor will not be sufficiently diffused and will stay near the slits, resulting in poor cooling.The granular insulators near the slits will melt and bond, and after the metal vapor is shattered, Since it condenses within the gap and along the inner surface of the melt, the insulation resistance after the shingle breaks becomes low. In addition, if the particle size is too coarse, the contact area with the steam will be small and the cooling effect will be weakened, exposing the fuse cylinder to high temperature and pressure, resulting in damage and
There is a risk of destruction and internal entanglement outside the slit.

This invention was made in order to eliminate the above-mentioned drawbacks, and its purpose is to provide a slit-type current-limiting fuse that has high insulation resistance after the shingle ruptures and eliminates the risk of damage to the fuse cylinder. By setting the particle size between mesh #9 and mesh #32, it suppresses the rise in temperature and pressure inside the fuse cylinder, maintains sufficient insulation resistance after the shingle ruptures, and allows freedom in particle size selection. This invention provides a slit-type current-limiting fuse that maintains the power level over a wide range.

The construction of the current limiting fuse of the slot type according to the invention is therefore exactly the same as that shown in FIGS. 1 and 2 and described above, except that the grain size of the granular insulator 10 is as described above.

If the particle size of the granular insulator 10 is finer than mesh #32 (particle average diameter 0.5 mm), the high-temperature, high-pressure metal vapor spewed out from the slits will not easily penetrate the granular insulation because the spaces between the granular insulators are small. The granular insulator cannot spread between the materials, and the granular insulator is melted near the slit, and after being shredded, it is bonded along the slit. For this reason,
Reduction of temperature and pressure inside the slit is hindered, impairing current limiting performance, and metal vapor condenses inside the slit or on the inner surface of the molten bond along the slit after cutting, reducing insulation resistance. . On the other hand, if the particle size is coarse, such as mesh #9 (particle average diameter 2 mm) or less, the spaces between the granular insulators are too large, allowing high temperature and high pressure metal vapor to fuse without sufficient cooling. It reaches the inner wall of the cylinder and damages the fuse cylinder, and since it has a high degree of ionization, it causes an internal circuit outside the slit. Therefore, if the particle size is between about mesh #9 and #32, metal vapor can be effectively cooled without the above-mentioned drawbacks. In this case, the granular insulator is
It goes without saying that in addition to the conventionally used silica sand, granular insulators such as alumina and magnesia can also be used.

As described above, according to the present invention, by using a granular insulator with a mesh size of about #9 to #32, high performance can be achieved without a decrease in insulation resistance or damage to the fuse cylinder after a shingle rupture. Limit the flow and cut off the flow,
In addition, the selection of granular insulators can be carried out with a wide range of freedom.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a fuse tube showing the inside of the structure of a slit-type current-limiting fuse according to the present invention in a plan view;
FIG. 2 is a sectional view of the fuse tube showing the inside in a side view. 1, 2a, 2b...insulating plate, 3...slit, 4...
...fusible piece, 4a...notch part of fusible piece, 5...screw, 6...groove, 7...electrode terminal, 8...screw, 9
...fuse tube, 10...granular insulator.

Claims (1)

[Claims] 1. A fusible piece connected to a pair of electrodes, at least a pair of arc extinguishers having a wider shape than the fusible piece, disposed opposite to each other with the fusible piece in between, and forming a narrow strip around the sides of the fusible piece. an insulator, a fixing member for fixing the pair of arc-extinguishing insulators together at both ends of the arc-extinguishing insulators, a fuse tube for housing the arc-extinguishing insulator, and the arc-extinguishing insulator and the fuse. A narrow-type current-limiting fuse that is filled in the space formed between the cylinder and the granular insulator whose particle size is between mesh #9 and #32.