JPH0580091B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Field of Industrial Application) The present invention relates to a current limiting fuse having a large current interrupting section and a small current interrupting section.

(Prior art) Normally, when trying to increase the rated current capacity of a current limiting fuse, it is necessary to increase the cross-sectional area of the fuse element, which increases the size of the caterpillar-like high resistance element that is formed when the fuse is cut off. The thermal influence of the flowing fuse on the insulator tube increases, causing a phenomenon called uneven heat failure of the insulator tube. As a result, it is necessary to increase the size of the fuse link itself, and the amount of arc-extinguishing sand to be filled also increases, resulting in an increase in overall weight.

Further, when the cross-sectional area of a single fuse element becomes large, it becomes difficult for the element metal to diffuse into the arc-extinguishing sand, causing problems in forming a resistor and causing a problem of poor interrupting performance.

Therefore, if you try to solve the above problem by using multiple fuse elements with small cross-sectional areas, simply reducing the cross-sectional area of the fuse elements and winding them at regular intervals will not work. The high-resistance elements that are formed when the current is cut off stick to each other and become linearly formed, making it impossible to maintain sufficient insulation distance, which eliminates the point of spirally winding the fuse element. .

As a solution to this problem, the applicant has already constructed a group fuse element with a plurality of fuse elements arranged at short pitches less than the diameter of the high resistance element, as shown in Japanese Patent Application Laid-Open No. 57-23439. However, it has been proposed that the group fuse element is wound around an insulating core at a pitch larger than the diameter of the high resistance element.

However, since the current limiting fuse configured as described above is not configured to cut off all areas, there is also a demand for a fuse that has a large current carrying rated current capacity and is capable of cutting off all areas.

(Problem to be Solved by the Invention) However, a part contributing to small current interruption (low alloy wire) is arranged in series with the large current interruption section, and the low alloy wire is covered with an arc-extinguishing tube. If a small current interrupting section is provided, and the winding pitch of the small current interrupting section is wound indistinguishably from the winding pitch of the large current interrupting section, the following problems occur.

(a) The arc extinguishing tube is damaged due to a sudden increase in arc heat and internal pressure, and the molten product formed by melting the arc extinguishing sand filled around it becomes large, causing the pitches to come close to each other or When they come into contact, this molten product causes flashover between the pitches, making it impossible to shut off.

(b) In order to prevent the problem in (a) above, it may be possible to increase the winding pitch of the large current interrupting portion, but this increases the volume of the entire fuse.

Structure of the Invention (Means for Solving the Problems) This invention provides an insulating core with a star-shaped cross section, and a large current interrupting section consisting of a large current element that contributes to interrupting large currents, and a small section that contributes to interrupting small currents. A current-limiting fuse consisting of a small current interrupting part constituted by a current element, and a fuse element covered with an arc-extinguishing tube wrapped around the part corresponding to the small current interrupting part, in which a plurality of said fuse elements are used. , these plurality of fuse elements constitute a group of elements, and in the large current interrupting section, a short pitch smaller than the maximum diameter of the caterpillar-like high-resistance material that is formed together with the arc-extinguishing sand when the large current is interrupted.
At P1, the fuse elements are arranged in parallel within an element group, and the element group is wound around the insulating core with a pitch P3 larger than the maximum diameter of the high resistance body, and the small current interrupting In the section, each fuse element is wound around the insulating core at a pitch P2 that is approximately equal to or larger than the pitch P3, and further, at both ends of an arc-extinguishing tube that covers each fuse element at the small current interrupting section. The opening and the openings at both ends of the arc extinguishing tubes of adjacent fuse elements are spaced apart from each other in the axial direction and circumferential direction via a protrusion on the circumference of the insulating core forming a star-shaped cross section. .

(Function) With the above solution, when the low magnification current is cut off due to an accident such as overload, the arc extinguishing tube is damaged due to arc heat and a sudden increase in internal pressure, and the arc extinguishing sand filled around it melts. Even if the molten product formed by the melting process elutes and spreads, the winding pitch P2 of the arc-extinguishing tube part of the fuse element is large, so there is no risk of flashing between these pitches due to the molten product, and the current limiting fuse will definitely complete the shutdown.

The caterpillar-like high-resistance body that the large-current interrupter forms with the arc-extinguishing sand sticks to the adjacent high-resistance member and becomes flat, so if the large-current interrupter is replaced with a single large-current interrupter, Its thickness is thinner than that of the formed high-resistance body, and the distance between the current-limiting fuse and the inner surface of the insulating cylinder can be reduced. Furthermore, the elements of the large current interrupting section are arranged at short pitches, so they can be wrapped around the insulating core for a long time.
If the overall quantity of the fuse element is the same, a thin insulating core or a short insulating core can be used.

(Example) Below, examples embodying this invention are shown in Figures 1 to 1.
This will be explained according to FIG.

The insulating tube 1 is made of an insulating material such as porcelain that has particularly excellent heat resistance, and has bottomed cylindrical electrode fittings 2 crowned at both ends thereof. An insulating core 3 with a star-shaped cross section is housed in the insulating tube 1 along the axial direction, and two fuse elements 4 are wound around the insulating core 3, each of which has both ends connected to the center of the electrode fittings 2. .

To explain the winding structure of the fuse element 4, each fuse element 4 is made of silver wire or the like as a large current element, and has a large current interrupting part 5 that contributes to interrupting large current such as short circuit current, and a large current interrupting part 5. A low-alloy metal wire 6 is connected in series to the central portion of the wire 5 and is made of a gold-silicon alloy or the like as a small current element and contributes to interrupting small currents such as overloads. A group of large current interrupting sections 7 made up of the large current interrupting sections 5 of each fuse element 4 are wound around the insulating core 3 at a pitch P3 having a sufficient insulation distance. The sufficient insulation distance is determined by the arc-extinguishing sand 8 filled in the insulating cylinder 1 when the large current interrupting part 5 is interrupted when a large current is interrupted.
The diameter is set to be sufficiently larger than the diameter of the caterpillar-shaped high-resistance body 9 that is formed together.

Further, the large current interrupting sections 5 in the group of large current interrupting sections 7 are arranged at short pitches P1 that are equal to or less than the diameter of the high resistance element 9.

Further, the low alloy wire 6 corresponding to the small current interrupting portion of each fuse element 4 is covered with arc extinguishing tubes 10A and 10B made of a fluorinated polymer such as polytetrafluoroethylene with a small gap therebetween. It is inserted into arc tubes 10A and 10B. Note that the arc extinguishing tube 10A, 1
0B is formed long enough to sufficiently cover the low alloy wire 6, and has openings 10a at both ends.
is plugged with a noncombustible material 11 such as asbestos to allow pressure to be released to the outside and to prevent the arc-extinguishing sand 8 from entering.

a low fusion alloy wire 6 of the fuse element 4;
The arc extinguishing tubes 10A and 10B constitute a small current interrupting section 12, and the winding pitch P2 of this small current interrupting section 12 with respect to the insulating core 3 (that is, the distance from the small current interrupting section 12 of another fuse element 4)
The winding pitch is such that when the arc extinguishing tubes 10A and 10B are wound and melted by arc heat, the molten products do not connect with each other, that is, the insulating core 3 of the group of large current interrupting parts 7.
The winding pitch P3 is set to be approximately equal to or larger than the winding pitch P3.

Further, in one arc extinguishing tube 10A, there is an opening 10 into which a silver wire or the like constituting the large current interrupting section 5 is inserted.
a and the corresponding opening 10a of the other arc-extinguishing tube 10B are spaced apart from each other in the axial direction and circumferential direction of the insulating core 3 via one protrusion 3a.

Note that the pitches P1, P2, and P3 are the distances between the centers of each corresponding element.

The action of the current limiting fuse configured as above will be explained.

Now, when a high-magnification current due to a phase-to-phase short circuit or a ground fault flows between the two electrode fittings 2 in this current-limiting fuse, the large current interrupting section 5 and the small current interrupting section 12 simultaneously fuse and fire. At this time, the surface area of the silver wire of the large current interrupting part 5 that comes into contact with the arc extinguishing sand 8 is larger than that of a single winding, and the cross-sectional area is small, so the metal vapor at the time of fusing and ignition is transferred to the arc extinguishing sand 8. Diffusion is facilitated, the cooling effect of the arc is enhanced, and the uniform caterpillar-shaped high-resistance elements 9 mutually form a flat caterpillar shape to rapidly limit and interrupt the current.

In the case of this high magnification current interruption, the large current interruption section 5 is arranged with a short pitch P1 smaller than the diameter of the caterpillar-like high resistance body 9 formed together with the arc extinguishing sand 8, and two large current Since the group of large current interrupting parts 7 made up of the interrupting parts 5 are wound with a pitch P3 larger than the diameter of the high-resistance element 9, the high-resistance elements 9 formed in the group are connected to adjacent ones separated by a distance of pitch P3. There is no contact with the high resistance element 9,
Since it is formed in a long spiral shape, the resistance that the fuse element 4 should have over its entire length is ensured.

Furthermore, in the two large current interrupting sections 5, the high resistance elements 9 formed by the respective large current elements in the group stick together and become flat as described above, so the two large current interrupting sections 5 are combined into one Its thickness is thinner than that of the high resistance body formed when it is replaced with a real large current interrupting part, and the distance between it and the inner surface of the insulating cylinder 1 can be reduced.

Furthermore, since the fuse elements 4 in a group are arranged at short pitches, long windings can be made around the insulating core 3, and if the overall amount of the fuse elements 4 is the same, fine insulating cores or short insulating cores can be wound. will be adopted.

Furthermore, when a low magnification current flows between the two electrode fittings 2 due to an accident such as overload, the silver wire of the high current interrupting section 5 with a high melting point will not melt, but the low fusion alloy wire 6 of the small current interrupting section 12 will melt. Only the tubes fuse and arc, and the heat from the arc thermally decomposes the arc-extinguishing tubes 10A and 10B.
Arc-extinguishing gas having negative electron characteristics is generated, and the pressure is increased in the arc-extinguishing tubes 10A, 10B to extinguish the slit arc.

Also, when this low magnification current is cut off, arc heat and a sudden increase in internal pressure may cause arc extinguishing tubes 10A, 1
Even if the arc extinguishing tube 10 of the fuse element 4 is damaged and the molten product formed by melting the arc extinguishing sand 8 filled around it elutes and spreads, the arc extinguishing tube 10 of the fuse element 4
Since the winding pitch P2 of the portions A and 10B is large, there is no risk of flashover occurring between these pitches due to molten products, and the current limiting fuse will surely shut off.

Furthermore, in this embodiment, arc extinguishing tubes 10A, 1
In 0B, the opening 10a into which the silver wire constituting the large current interrupting part 5 is inserted and the corresponding opening 10a of the other arc-extinguishing tube are shifted in the axial direction of the insulating core 3 and in the upward direction around the circumference of the insulating core 3. They are placed apart from each other. Therefore, when a small current is interrupted, the small current interrupting portion 1 of one of the fuse elements 4
The arc emitted by the slit arc extinguishing performed in step 2 does not adversely affect the arc extinguishing tube of the adjacent fuse element 4.

In addition, when increasing the breaking capacity with one element conventionally, there is a decrease in the breaking capacity in the small current range due to the increase in the cross-sectional area of the element as the breaking capacity increases, but since two elements are used, The cross-sectional area of one element can be made smaller as the capacity increases, and the interrupting ability in a small current range is improved.

Effects of the Invention As detailed above, the present invention increases the current carrying rated current capacity and is capable of interrupting the entire area, and even when interrupting a small current, the molten product short-circuits between pitches, making it impossible to interrupt the current. Moreover, in the small current interrupting section, there is no risk that the emitted arc due to the narrow arc extinguishing in the arc extinguishing tube of one fuse element will have an adverse effect on the small current interrupting section of other fuse elements. This is an excellent invention for industrial use.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of an embodiment of a current-limiting fuse embodying the present invention, FIG. 2 is a cross-sectional view of an arc-extinguishing tube, and FIG. 3 is a cross-sectional view of an insulating core. DESCRIPTION OF SYMBOLS 1... Insulating tube, 2... Electrode fitting, 3... Insulating core, 4... Fuse element, 5... Large current interrupting part, 6... Low alloy alloy wire, 7... Large current interrupting part,
8... Arc-extinguishing sand, 9... High resistance material, 10A, 10B
... Arc extinguishing tube, 12 ... Small current interrupting section.

Claims (1)

[Scope of Claims] 1. For an insulating core with a star-shaped cross section, a large current interrupting section is constructed of a large current element that contributes to interrupting large currents, and a small current interrupting section is composed of a small current element that contributes to interrupting small currents. In a current limiting fuse in which a fuse element covered with an arc-extinguishing tube is wrapped around the part corresponding to the small current interrupting part, there are a plurality of fuse elements, and these plurality of fuse elements form a group. In the large current interrupting section, each of the fuse elements is placed in the element group with a short pitch P1 that is less than the maximum diameter of the caterpillar-like high resistance material that is formed together with the arc extinguishing sand when the large current is interrupted. and the element group is wound around the insulating core at a pitch P3 larger than the maximum diameter of the high resistance element, and in the small current interrupting section, each fuse element is arranged in parallel with the pitch P3. Openings at both ends of the arc extinguishing tubes are wound around the insulating core at intervals of the same or greater pitch P2, and further cover each fuse element in the small current interrupting section, and the arc extinguishing tubes of the fuse elements adjacent to each other. A current limiting fuse characterized in that the openings at both ends are offset from each other in the axial direction and in the circumferential direction via a protrusion on the circumference of an insulating core forming a star-shaped cross section, and are spaced apart from each other.