JPH077635B2 - Current limiting fuses - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current limiting fuse, and more particularly, to an improvement in the terminal portion of a fuse element during a short-circuit current cutoff operation.

[Background of the Invention]

In recent years, there has been a demand for miniaturization of current limiting fuses as power receiving equipment becomes smaller and lighter. Since the small fuse has a small filling amount of arc-extinguishing particles, the conventional technique has the following problems in work aspect and performance.

1. Problems in work .1 By reducing the gap between the porcelain insulator and the insulating rod,
It is difficult to connect the fuse element terminal portion to the electrode cap, and tension acts on the terminal portion, which tends to cause local elongation.

． At the time of filling the arc-extinguishing particles into the porcelain tube, voids (insufficient arc-extinguishing particles) are likely to occur at the ends of both ends.

2. Problems during transportation and installation Due to vibrations and impacts during transportation and installation, the filled arc-extinguishing particles behave (because the retention balance between arc-extinguishing particles is lost during packing), and as a result, both Voids are likely to occur in the terminal part.

3. Effect on breaking performance As an effect of the above problems on breaking performance, when a short-circuit current flows, the point at which the local extension of the terminal portion with the smallest current carrying capacity occurs is first melted and arc extinguishing begins. If there is the void in the porcelain tube, the arc generated will expand and the arc extinguishing particles that will be extinguished while cooling will be insufficient. As a result, the high-temperature high-resistance molten product (commonly known as worms) will swell and the inner surface of the porcelain tube end Due to the contact, heat shock causes porcelain tube cracking and damage.

A current limiting fuse of this type is disclosed in Japanese Laid-Open Patent Publication No. 49-54844.
And JP-A-54-63255.

[Object of the Invention]

An object of the present invention is to provide a current limiting fuse which prevents porcelain tube cracking and breakage during short-circuit current interruption operation due to voids in the porcelain tube end portion.

[Outline of Invention]

The cooling ring used in the current limiting fuse of the present invention is composed of a tubular portion and a flange portion provided at one end thereof, and the outside diameter side is formed through a through groove that axially penetrates the tubular portion and a part of the flange portion. The elastic ring is pressed from the outer diameter side to be inserted into the insulating cylinder, and the cylindrical portion and the flange portion are arranged on the inner surface and the end surface of the insulating cylinder.

Example of Invention

An embodiment of the present invention will be described below with reference to the current limiting fuse shown in FIG.

The insulating porcelain porcelain tube 2 having the electrode caps 1 at both ends is
A particle-shaped arc-extinguishing agent 3 filled in the inside, for example, silica sand, an electrode guide 4 made of both ends of the electrode cap 1 and a ring-shaped metal material, and electrically connected by crimping and caulking work, the fuse wire of good conductor. 5 For example φ0.3m
An insulating rod 6 formed by spirally winding a thin Ag wire of about m is stored. Both ends of the fuse wire 5 are fixed to an insulating rod by an insulating material 7 having an arc extinguishing property, for example, a fluorine resin, and the spiral winding position is held.

Both ends of the porcelain porcelain tube 2 are made of elastic metal material,
In order to meet the molding tolerance of the inner diameter of the porcelain insulator, the arc heat cooling ring 8 made of, for example, a phosphor bronze plate having the through groove 8a shown in FIG. And the same electric potential as that of the electrode cap 1.

Next, the assembling work and actual use of the current limiting fuse of the present invention will be described.

FIG. 1 shows an overall view of an assembled state, FIG. 2 shows a detailed view of an arc heat cooling ring alone, and FIG. 3 shows a fuse wire 5 wound around an insulating rod 6 inside an insulator tube 2 with an arc heat cooling ring 8. FIG. 11 is a diagram showing a state in which after being held and stored by the element guide 4, the arc extinguishing agent 3 made of arc extinguishing particles of about 48 to 100 mesh is filled in the porcelain tube inner space portion while applying vibration from the direction of the arrow P. .

Since there are many constituent members at the end of the fuse wire 5, there is a large obstacle to the inflow of the arc-extinguishing agent, and in reality, voids are likely to occur at the inner corners of the pipe as shown by G in FIGS. FIG. 4 is a view showing a state in which the fuse wire 5 is connected to the electrode cap 1 after the arc-extinguishing agent is filled, and FIG. 4I is a crimping caulking force F between the end of the fuse wire 5 and the projection 4C of the electrode cap 1. Fig. 4-II shows a state in which assembling work is uneven when left and right are uniformly worked, and Fig. 4-II shows a state in which assembly work varies when a pressing force F of the protrusion 4C is applied unevenly on the left and right. At the end of the fuse wire 5 of such a variation work product, an excessive tension f due to the displacement θ of the electrode cap 1 and the element guide 4 at the time of crimping and crimping work is applied, and even if the wire is not broken, a thin portion is formed due to local extension. Occur.

A case where the current limiting fuse assembled in this way is actually used will be described.

FIG. 5I shows an example of a balance state between the particles of the arc-quenching agent 4 formed under the filling condition at the time of assembly, and the gap g is held between the particles.

However, vibrations and impact forces different from the arc extinguishing agent filling conditions during assembly were newly added during field transportation, installation, and operation, and the balance between the particles in Figure 5 -I was lost, causing
It changes like II and the gap between particles changes narrowly like g '. That is, in actual use, the arc extinguishing agent space portion G in the porcelain bushing, which is generated during assembly, is further enlarged.

When an excessive current such as a short-circuit current flows in this current limiting fuse, the fuse wire 5 that generally has a small current flow and heat capacity is used.
The one that melts and extinguishes from the central part of the fuse is the thinning due to the local extension of the fuse fuse wire end during the above-mentioned assembly work, the vibration during the assembly and transportation, installation and operation, and the arc extinguishing agent in the insulator tube due to impact. The terminal portion is melted first due to the expansion of the void.

In the case of the prior art, if the fuse is blown out first at the end of the fuse wire, it is instantly pyrolyzed (solid → liquid → gas) and gasified (silver, hydrogen gas) as shown in Fig. 6-II, and the arc-extinguishing agent. High temperature (approx. 1000 ℃)
The arc-extinguishing operation is completed while producing the high-resistance melted product (commonly known as worm), but since the arc-extinguishing particles are few in the terminal part, the high-resistance melted product is enlarged and the porcelain becomes porcelain. It comes into direct contact with the porcelain tube 2 (gives heat insulation of about 1000 ° C. to the porcelain tube), and cracks 10 occur, which in the worst case lead to breakage. However, in the case of the current limiting fuse of the present invention, the arc heat cooling ring 8 made of, for example, a phosphor bronze plate is arranged as shown in FIG. The heat is instantaneously conducted to the cooling ring 8 and rapidly radiated by the electrode cap 1, so that the required cooling volume of the arc extinguishing agent 3 is reduced. Therefore, the high resistance melting product can be reduced to about 40% in volume ratio as compared with the prior art. It is possible to prevent contact with the porcelain pipes by reducing the amount of high-resistance melted product, which is a reliable current limiting fuse with stable blocking performance. The cooling ring 8 is composed of a tubular portion 8b, a flange portion 8c provided at one end thereof, and a through groove 8a obtained by axially cutting a portion of the tubular portion 8b and the flange portion 8c. The through groove 8a has a function of absorbing expansion and contraction of the cooling ring 8 toward the outer and inner diameter sides.

Therefore, the cooling ring 8 is pressed from the outer diameter side to be inserted into the porcelain bushing, and the cylindrical portion 8b and the flange portion 8c are provided on the inner surface and the end surface of the porcelain bushing.
Since the cooling ring 8 can absorb the tolerance of the inner diameter of the porcelain tube 2, the cooling ring 8 can be easily inserted, and at the same time, the expansion and contraction of the cooling ring 8 due to the heat of the overcurrent can be absorbed. It became possible to prevent the damage of 2.

〔The invention's effect〕

As described above, according to the present invention, assembling work, transportation,
It is possible to prevent porcelain tube cracks and breakage accidents during breaking operation due to uncertain factors such as installation tolerances, assembly tolerances, work variations, and diversification of usage conditions. Can be obtained.

[Brief description of drawings]

1 is a side sectional view of a current limiting fuse shown as an embodiment of the present invention, FIG. 2 is a perspective view of the arc heat cooling ring of FIG. 1, FIG. 3 and FIG. 4—I and FIG. 4— II is an enlarged side sectional view of an essential part of FIG. 1, FIG. 5-I and FIG. 5-II are state diagrams showing the state of arc-extinguishing particles of FIG. 1, and FIG. FIG. 6-II is an enlarged side sectional view of a main part of the figure, and FIG. 6-II is an enlarged side sectional view of a conventional current limiting fuse. DESCRIPTION OF SYMBOLS 1 ... Electrode cap, 2 ... Porcelain porcelain tube, 3 ... Arc extinguishing agent, 4 ... Element guide, 5 ... Fuse wire, 6 ... Insulating rod, 7 ... Insulating material, 8 ... Arc heat cooling ring, 9 ... High resistance fusion product .

Claims (1)

[Claims] 1. An insulating rod around which a fuse wire is wound is arranged in an insulating cylinder having an arc extinguishing agent, both ends of the insulating cylinder are sealed with a cap, and the fuse wire end and one end are insulated from each other in a protrusion provided on the cap. In the case where the other end of the element guide that supports the rod is inserted and the protruding portion is pressed to hold the fuse wire end and the other end of the element guide in the protruding portion, the cylindrical portion and the flange portion provided at this one end Provide a cooling ring that expands and contracts to the outer and inner diameter side through a through groove that axially penetrates a part of the cylindrical portion and the flange portion, press the cooling ring from the outer diameter side, and insert it into the insulating cylinder for insulation. A current limiting fuse characterized in that a cylinder portion and a flange portion are arranged on a cylinder inner surface and an end surface.