JP2013175362A - Electric wire fuse - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric wire fuse in which current limiting effects can be obtained without using an arc-extinguishing material, in the electric wire fuse which comprises inner and outer double fuse tubes and in which a terminal metal fitting for electric wire connection is projected from both end openings of the outer tube and both the end openings are sealed with an outer cap, and a fuse element is connected between these terminals inside of the inner tube.SOLUTION: Between an inner surface of an outer cap and protecting caps in both ends of an inner tube, a high-melting metal ring whose heat conductivity is low is provided while sealing a gap with an inner wall of an outer tube with an insulative sealing body such as a silicon ring.

Description

The present invention mainly relates to an improvement in an electric wire fuse that is attached to an outdoor distribution line and safely shuts off an overcurrent or a large current caused by an overload or a short circuit to protect the distribution line.

For example, a current limiting fuse is used to interrupt an accident current such as an overload in a power distribution line or a large short-circuit current. It has a basic structure in which a fuse element with a narrow cross section is filled with silica sand, alumina, etc. as an arc extinguishing agent. When an accident current such as a short-circuit current flows, the fuse element quickly melts and occurs. It absorbs and cools the gas with an arc extinguishing agent and has an action of interrupting the arc.
In addition, as seen in Patent Document 1, an example of a current limiting fuse having a two-stage element structure in which a large current interrupting part and a low load fusing part are connected is also provided. That is, at a relatively small current such as an overload current, a small current region of the low melting point alloy is melted to open the electric circuit. When an excessive current such as a short-circuit current flows, the interrupting portion of the large current interrupting portion is melted and vaporized, and the generated arc is adsorbed and cooled by the arc extinguishing agent and extinguished.

JP 2001-68010 A

In a current-limiting fuse, the fuse element repeatedly expands and contracts in the cold / thermal heat cycle of the fuse element due to repetitive current, causing friction with arc-extinguishing agents such as high-hardness and non-shrinkable silica sand and alumina. There is a difficulty to be damaged.
In addition, a non-current-limiting type fuse can be protected for a long period of time, but the current-limiting fuse has a fast fusing characteristic and a protection range of a distribution line such as a lead-in wire becomes narrow. When the rated current is lowered, the protection range is widened, but a short-time current pulse tends to cause a blown fuse.

In the manufacturing process, a process of filling the arc-extinguishing agent is required, and there is a problem that it takes time and cost. Since arc-extinguishing agents are related to the shut-off performance, it is necessary to mix the arc-extinguishing agent for each particle size, and the filling work must be mechanized because it is carried out by vibration etc. There is also a difficulty that equipment costs and maintenance costs are incurred. It was. Since it is housed in an opaque heat-resistant case and the arc-extinguishing agent causes a chemical reaction when it is shut off, it is necessary to provide an external display structure because it is not possible to visually check for a blown fuse, but this may cause problems or complicate the structure. There was also a problem that led to an increase in cost.

In addition, in a current limiting fuse with a two-stage element configuration, it is possible to give the fusing characteristics slowness, but the number of connection points increases, and there is a difficulty in lack of reliability in electrical conductivity, which complicates the structure. There was a drawback that led to an increase in cost.

Accordingly, an object of the present invention is to provide an electric wire fuse that can obtain a current limiting effect without using an arc extinguishing agent.

In order to achieve the above object, the present invention has an inner / outer double fuse cylinder, the terminal fitting for connecting the electric wire is protruded from the opening at both ends of the outer cylinder through the sleeve, and the opening at both ends is sealed with the outer cap. In a wire fuse in which a fuse element is connected between these terminals in the inner cylinder, a ring made of a refractory metal having a low thermal conductivity is provided between the inner surface of the outer cap and the protective caps at both ends of the inner cylinder. The space between the inner wall of the cylinder is provided by sealing with an insulating sealing body such as a silicon ring.

As the fuse element, an element in which a fusible portion made of a low melting point metal such as a tin alloy and a blocking portion made of a resistance wire such as a copper alloy are connected in series is used. Install this fuse element in the inner cylinder of the inner and outer double fuse cylinders, connect the terminal fittings for electric wire connection to both ends of the fuse element, and project them from the openings on both ends of the outer cylinder through the sleeves for electric wire connection. Both end openings are sealed with outer caps.

The inner cylinder is covered with protective caps such as silicon resin at both ends, and a ring made of a refractory metal with low thermal conductivity, such as a ring made of carbon steel or stainless steel, is installed between the outer cap and the protective cap. The ring and the inner wall of the outer cylinder are sealed with an insulating sealing body such as a silicon ring.

The ring made of a refractory metal can take various forms such as a short straight cylindrical shape, or a hook shape in which the inner end portion on the protective cap side is bent toward the inner diameter side. Usually, the inner cylinder is made of glass and the outer cylinder is made of polycarbonate.

  As described above, the electric wire fuse of the present invention does not require an arc-extinguishing agent. Therefore, there is a possibility that the fuse element may be damaged even if the fuse element repeatedly expands and contracts in the cold / thermal heat cycle of the fuse element due to repeated current. Absent. Since it is not necessary to fill the arc-extinguishing agent in the manufacturing process, manufacturing time and cost can be reduced. Moreover, since it is a non-current limiting type, it is possible to protect up to a long time region.

When a short circuit accident occurs in the distribution line and a large current flows through the distribution line, the breaker in the fuse element is ignited by the Joule heat due to the current and melts and vaporizes. At this time, arc discharge occurs between the fusible part and the terminal fitting, but since a ring made of refractory metal is installed,
The arc discharge line changes instantly and switches to discharge between the refractory metal rings at both ends. As a result, the fusible part is separated from the path of current energy, so that metal gasification can be avoided and the pressure in the fuse is reduced. In a refractory metal ring, the discharge point moves from the inside to the outside by electromagnetic force, and the discharge point shifts one after another, so that the progress of the heat-dependent arc discharge is suppressed. Since the ring is made of a refractory metal, melting and gasification are suppressed.

The metal gas generated by the arc discharge is released into the ring and is cooled and solidified. The refractory metal ring has a low thermal conductivity, and after being temporarily stored, it is gradually conducted to the sleeve and connecting wire. Therefore, the heat conduction time lag can be suppressed to the heat resistant range of the outer cylinder, so that thermal deformation can be avoided.
Further, since an insulating sealing body such as a silicon ring is used, the carbide generated from the outer cylinder is discharged only to the central portion between the outer cylinder and the glass, and the carbide does not adhere to both ends. Therefore, the mega (500 V insulation resistance) between the sleeves after being cut off becomes good.

Sectional drawing which shows one embodiment of the electric wire fuse which concerns on this invention Schematic showing the current limiting effect of the electric wire fuse Schematic showing the flow of generated gas in the same wire fuse Partial sectional view showing another example of an insulating sealing body such as a refractory metal ring and a silicon ring used for the electric wire fuse Partial sectional view showing still another example of an insulating sealing body such as a ring made of refractory metal and a silicon ring used for the electric wire fuse Partial sectional view showing still another example of an insulating sealing body such as a refractory metal ring and a silicon ring used for the electric wire fuse Front view showing another example of fuse element Front view showing still another example of fuse element

FIG. 1 is a cross-sectional view showing an example of an electric wire fuse according to the present invention. The basic structure of the electric wire fuse is an internal / external double fuse cylinder. The opening is sealed with an outer cap 3 and a fuse element 5 is connected between these terminals in the inner cylinder 4. The fuse element 5 is a fusible portion made of a low melting point metal such as a tin alloy. 6 and a blocking portion 7 made of a resistance wire such as a copper alloy are connected in series, and the terminal fitting 2 connected to both ends thereof is protruded from the outer cap 3 through a sleeve 8 for wire connection. The outer cylinder 1 is made of polycarbonate and is ultrasonically welded to the outer cap 3. The inner cylinder 4 is made of glass, and both ends of the inner cylinder are covered with protective caps 9 such as silicon resin.
This basic configuration is substantially the same as that of a conventional electric wire fuse.

The electric wire fuse of the present invention is intended to achieve a current-limiting effect without using an arc-extinguishing agent. For this purpose, a refractory metal ring 10 having a low thermal conductivity and an insulating sealing body 11 such as a silicon ring are employed. doing.
That is, a ring 10 made of a refractory metal having a low thermal conductivity, such as a ring made of carbon steel or stainless steel, is installed between a protective cap 9 made of silicon resin or the like that covers both ends of the inner cylinder 4 and the outer cap 3. The space between the ring 10 and the inner wall of the outer cylinder 1 is sealed with an insulating sealing body 11 such as a silicon ring.

The ring 10 made of a refractory metal has a bowl shape in which the inner end portion on the protective cap 9 side is bent toward the inner diameter side as shown in FIG. 1, or a short straight cylindrical shape as shown in FIG. 4, as shown in FIG. Various forms such as a state of being bent at right angles to each other can be taken.
Further, the insulating sealing body 11 such as a silicon ring also has a two-stage structure of a thick part 11a and a thin part 11b as shown in FIG. 1, or only a thick part 11a as shown in FIG. 4, or as shown in FIG. Alternatively, a structure in which the thick-walled portion 11a and the thin-walled portion 11b have a two-stage structure and the bent end portion of the thin-walled portion 11b seals between the ring 10 made of a refractory metal and the protective cap 9 can also be adopted.
Moreover, as shown in FIG. 6, it is also possible to integrally form a protective cap 9 that covers both ends of the inner cylinder 4 and an insulating sealing body 11 such as a silicon ring.

1 shows a type in which a fusible portion 6 made of a low melting point metal such as a tin alloy is cast between the blocking portions 7 made of a resistance wire such as a copper alloy, but is not limited thereto. Various types of fuse elements can be employed.
For example, the fuse element shown in FIG. 7 includes a heat storage part 12 made of a conduit or the like in a blocking part 7 made of a resistance wire, and solder is attached to the surface in a low melting point metal tank to form a soluble part 6. When an overcurrent is applied, the copper-based resistance wire and the tin-based metal cause a diffusion reaction due to heat generation, and can be melted at a temperature considerably lower than the melting point of the copper-based metal.
Further, the fuse element shown in FIG. 8 is obtained by winding a part of a resistance wire in a coil shape and attaching solder in a low melting point metal tank to form a soluble portion 6, which is more than the heat storage type of FIG. 7. It can be set as the soluble part 6 which consists of a tin-type metal, and can be made to melt | disconnect further at low temperature.

In the electric wire fuse having such a configuration, when a short circuit accident occurs in the distribution line and a large current flows through the distribution line, the interrupting portion 7 in the fuse element 5 is ignited and melted / vaporized by Joule heat due to the current. At this time, arc discharge occurs between the fusible part 6 and the terminal fitting 2, but since the refractory metal ring 10 is installed, the arc discharge line changes instantaneously and the refractory metal rings at both ends change. Switch to 10 discharges.

As a result, the fusible portion 6 is separated from the path of current energy, and metal gasification can be avoided, and the pressure on the fuse is reduced. In the refractory metal ring 10, the discharge point moves from the inside to the outside due to electromagnetic force, and the discharge point shifts one after another, so that the progress of the heat-dependent arc discharge is suppressed. Since the ring 10 itself is made of a refractory metal, melting and gasification are suppressed.

The metal gas generated by the arc discharge is released into the refractory metallic ring 10 and is cooled and solidified. The refractory metallic ring 10 has a low thermal conductivity, and after being temporarily stored, it is gradually conducted to the sleeve 8 and the connecting wire. Therefore, the heat conduction time lag can be suppressed to the heat-resistant range of the outer cylinder 1, so that thermal deformation can be avoided.

Further, since an insulating sealing body 11 such as a silicon ring is used, the carbide generated from the outer cylinder 1 is discharged only to the central portion between the outer cylinder 1 and the glass inner cylinder 4, and the carbide adheres to both ends. Not. Therefore, the mega (500 V insulation resistance) between the sleeves after being cut off becomes good.
FIG. 3 shows the flow of the generated gas with arrows. The metal gas generated by arc discharge is released into the high-melting-point metallic ring 10, and the carbide generated from the outer cylinder 1 is made of the outer cylinder 1 and glass. It is discharged only in the central part between the inner cylinders 4. Further, the metal gas does not adhere as soot in the portion surrounded by a circle.

FIG. 2 is a schematic diagram of the breaking current waveform. Compared with the accident current waveform (b), the effect of reducing the current energy (I ² t) of the electric wire fuse (b) according to the present invention is 3 cycles (53 mS). 92% and half-wave (12 mS) is about -75%, and the suppression of energy can greatly reduce the influence of thermal influences. That is, the electric wire fuse according to the present invention achieves a current limiting effect without using an arc extinguishing agent.

As described above, the electric wire fuse of the present invention has the following advantages.
Since the arc-extinguishing agent is unnecessary, there is no possibility that the fuse element is damaged in the cold / hot heat cycle of the fuse element due to repetitive current. Since it is not necessary to fill the arc-extinguishing agent in the manufacturing process, manufacturing time and cost can be reduced. Moreover, since it is a non-current limiting type, it is possible to protect up to a long time region.
When a short-circuit accident occurs, the arc discharge line switches to discharge between the refractory metal rings at both ends, so the fusible part is separated from the path of current energy, and metal gasification can be avoided. Pressure top is reduced. In a refractory metal ring, the discharge point moves from the inside to the outside by electromagnetic force, and the discharge point shifts one after another, so that the progress of the heat-dependent arc discharge is suppressed.
The metal gas generated by the arc discharge is released into the ring and is cooled and solidified. The refractory metal ring has a low thermal conductivity, and after being temporarily stored, it is gradually conducted to the sleeve and connecting wire. Therefore, the heat conduction time lag can be suppressed to the heat resistant range of the outer cylinder, so that thermal deformation can be avoided.
Further, since an insulating sealing body such as a silicon ring is used, the carbide generated from the outer cylinder is discharged only to the central portion between the outer cylinder and the glass, and the carbide does not adhere to both ends. Therefore, the mega (500 V insulation resistance) between the sleeves after being cut off becomes good.

DESCRIPTION OF SYMBOLS 1 ... Outer cylinder 2 ... Terminal metal fitting 3 ... Outer cap 4 ... Inner cylinder 5 ... Fuse element 6 ... Soluble part 7 ... Blocking part 8 ... Sleeve 9 ... Protective cap 10 ... Ring 11 made of refractory metal ... Insulating sealing body 11a ... thick part 11b ... thin part 12 ... heat storage part

Claims (2)

It has an inner and outer double fuse cylinder, and the terminal fitting for connecting the wire is projected from the opening at both ends of the outer cylinder through the sleeve, and the opening at both ends is sealed with an outer cap, and the fuse is connected between these terminals in the inner cylinder. In the electric wire fuse to which the element is connected, a ring made of a refractory metal having a low thermal conductivity is insulated between the inner surface of the outer cap and the protective caps at both ends of the inner cylinder, and a silicon ring or the like is insulated from the inner wall of the outer cylinder. An electric wire fuse characterized by being sealed with a sealing material.   The electric wire fuse according to claim 1, wherein the inner cylinder is a glass tube, the outer cylinder and the outer cap are made of polycarbonate, and the outer cylinder and the outer cap are ultrasonically welded.

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