JP2009032567A - Fuse - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress temperature-rising in a rated current and reduce a cut-off current at the time of fusion by maintaining a current-limiting performance. <P>SOLUTION: A linear or belt-like fuse-element 3 is wound around the outer periphery of an inner cylinder 1, and an integrated body of the inner cylinder 1 and the fuse-element 3 is housed in an insulator cylindrical body 6, while an arc extinguishing sand 7 is filled between the outer wall of the inner cylinder 1 and the inner wall of the cylindrical body 6, and both end apertures of the cylindrical body 6 are sealed with terminals 5. The fuse-element 3 has a structure in which on the outer peripheral face of a round wire 10 or belt-like wires 20 composed of high melting point metal materials and metal covering materials 11, 21 composed of low melting point metal materials are covered. As the high melting point metal material, tungsten or molybdenum is used, and as the low melting point material, lead, zinc, tin, cadmium, aluminum, copper, silver, or alloy of these is used. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuse applicable to a high voltage circuit for electric power.

  FIG. 4 is a cross-sectional view showing a configuration example of a high-voltage fuse applied to a conventional high-voltage circuit of 3 to 22 kV. A metallic retaining ring 2 is wound around and fixed to both ends of a porcelain star-shaped inner cylinder 1. The wire or belt-like fusible body 3 is wound around the outer peripheral surface of the inner cylinder 1 with an interval so as not to wrap, and both end portions of the fusible body 3 are spot-welded to the retaining ring 2. One end of a connection piece 4 is connected to the retaining ring 2, and the other end is spot welded to a metallic terminal 5. The inner cylinder 1 around which the fusible body 3 is wound is stored in a porcelain cylindrical body 6 with a gap maintained therein, and arc-extinguishing sand 7 is filled in the gap.

  FIG. 5 is a cross-sectional view taken along the line XX of FIG. A plurality of ridges 1 a are formed in the axial direction of the outer periphery of the inner cylinder 1. Due to the presence of the plurality of protrusions 1a, the current interruption capacity and the energization performance of the device are improved. The fusible body 3 is wound around the outer periphery of the inner cylinder 1 in a state of being pulled linearly at the tip of the protrusion 1a. Arc-extinguishing sand 7 is also filled in the recesses formed between the protrusions 1a adjacent in the circumferential direction. Thereby, the arc-extinguishing sand 7 can be in contact with both surfaces of the fusible body 3. The current flows from the terminal 5 to the fusible body 3 through the connecting piece 4 and the retaining ring 2, but when an overcurrent flows, the fusible body 3 is melted and the current is cut off. The arc-extinguishing sand 7 serves to extinguish a current arc generated when the fusible body 3 is melted. As the arc-extinguishing sand 7, quartz sand is generally used.

  When the high-voltage fuse receives an applied current that exceeds the rated current of the fusible body 3, this excessive current causes resistance heating sufficient for the fusible body 3 to reach the melting temperature. Melting or vaporization of the fusible body 3 occurs along its length, in which case an electric arc is isolated in each of the melting regions of the fusible body 3. When the isolation occurs, the fusible body 3 or the metal vapor enters between the sands of the arc-extinguishing sand 7 and condenses through the heat transfer phenomenon to the arc-extinguishing sand 7. Dispersed mechanically, no conduction can be obtained. Further, since heat generated by the arc and ionized gas are cooled between the sands of the arc-extinguishing sand 7, conduction in the fuse is completely interrupted.

  Aluminum, copper, tin, zinc, cadmium, or an alloy thereof is used as the fusible material of the high-voltage fuse as described above, and silver is a particularly preferable material. A high melting point metal material such as molybdenum or tungsten having excellent current limiting performance is also used. This refractory metal material has a large increase in resistance due to temperature rise, so when overcurrent flows through the fusible body, the resistance value increases due to the temperature rise, the current amount before melting of the fusible body decreases, Breaking current can be reduced. For this reason, it becomes possible to suppress the rebound voltage accompanying the interruption | blocking which generate | occur | produces from the excessive current by a short circuit, and the reactor part on the electric power supply side and load side.

  Copper or silver, which is one of the metal materials used for the fusible body, has a small current limiting effect because of its good electrical conductivity. Therefore, the shape of the fusible body is devised, or an alloy using copper and silver is used. However, since these materials also have relatively good electrical conductivity, the self-heating of the fuse at the rated current amount is small. On the other hand, fuses with fusible materials such as tungsten or molybdenum, which is a refractory metal material, have a large increase in resistance due to room temperature and temperature rise, so the fuse generates heat even within the rated current and the temperature rises significantly. Some have surface temperatures of 200 ° C. or higher.

In addition, there is a device in which a fusible element is added to the main fusible body, and after the fusible element is blown in the overcurrent region, the main fusible body is blown and current-limited to improve the cut-off characteristics (for example, Patent Document 1 and Patent Document). 2).
Japanese Patent Publication No. 60-35439 Japanese Patent Publication No. 7-7634

  However, high-voltage fuses that use high-melting-point metal materials such as tungsten and molybdenum as the fusible body generate heat due to the high resistance of the fusible body, even within the rated current, and they are caused by the temperature rise of the arc-extinguishing sand. There is a risk of voltage fluctuation on the load side due to a drop in the breaking characteristics or a current change. The temperature rise at the outer periphery of the fuse causes the temperature inside the fuse storage device to rise, so it is necessary not only to maintain the heat resistance of the equipment in the device, but also to reduce the cooling performance of the device when multiple high-voltage fuses are used. invited. Further, in an atmosphere in which a high-voltage fuse is used, for example, a generator such as an ozonizer, there is a problem that the generated gas component is decomposed and the generation efficiency is lowered due to this temperature rise.

  On the other hand, a high-voltage fuse using tungsten or molybdenum has a large temperature change during energization and non-energization. Therefore, at the junction with the terminal 5 connected to the cylindrical body 6, the difference between these thermal expansion coefficients and the temperature. Due to the difference, airtightness and bonding could not be maintained.

  Moreover, as described in Patent Document 1 or Patent Document 2, after the fusible element is melted in the overcurrent region, the main fusible body is melted to improve the shut-off characteristics, and the structure of the fusible body is complicated. There was a problem that it was difficult.

  The present invention has been made in view of the above points, and can suppress a temperature rise within the rated current, maintain current-limiting performance, reduce the breaking current during fusing, and reduce the temperature to the peripheral device. An object of the present invention is to provide a fuse that can eliminate the influence of the rise and improve the reliability.

  The fuse of the present invention has an inner cylinder made of an insulator and a fusible body wound around the inner cylinder. In the fuse in which the fusible body is blown by an overcurrent, the fusible body has an electric resistance due to a temperature rise. It is characterized by having a structure in which a high melting point metal material having an increased resistance is coated with a low melting point metal material having a smaller electric resistance than the high melting point metal material.

  According to this configuration, when the current flowing through the fuse is in the rated current range, the current flowing through the layer having high electrical conductivity made of the low melting point metal material disposed on the surface layer of the fusible body is dominant. Therefore, the temperature rise in the rated current range can be kept low compared to a high-voltage fuse using a refractory metal material alone as a fusible element. On the other hand, when an overcurrent occurs, the temperature rises due to the current flowing through the fusible body, but when the temperature reaches or exceeds the melting point of the low melting point metal material coated on the surface of the high melting point metal material, The melting point metal material melts and vaporizes, and desorbs from the surface of the refractory metal material. As a result, the refractory metal material becomes a line or a band, and the cross-sectional area through which the current flows through the fusible body is reduced. Will flow. Since the current concentrates on the refractory metal material, the current flowing in the fusible body increases and the cross-sectional area of the fusible body decreases at the same time. In addition to being reduced, when a current further flows, the refractory metal material is melted and the current is interrupted. Therefore, by covering the surface of the refractory metal material with a low-melting-point metal material having low electrical resistance, the temperature rise of the fuse within the rated current capacity is reduced, and the current in the overcurrent region is instantaneously limited. Can cut off load and abnormal current.

  According to the present invention, in the fuse, the inner cylinder around which the fusible body is wound is housed in a housing made of an insulating material, and an arc extinguishing body is filled in a gap between the inner cylinder and the inner wall of the housing. The arc extinguishing body is made of arc extinguishing sand fixed in the gap by infiltrating water glass.

  With this configuration, the water glass undergoes an endothermic reaction due to the heat generated when the fusible body melts, thereby preventing overheating by suppressing the temperature rise of the melt of the fusible body and shortening the arc extinguishing time. . As a result, it is possible to suppress a rapid increase in the internal pressure of the fuse, and to prevent cracking and destruction of the fuse outer tube due to heat shock and overpressure. In addition, the water glass reacts with the melt of the high-temperature soluble material to form a non-conductive material, so that re-conduction is prevented and complete disconnection of the fuse is realized.

  In the above fuse, the fusible body has a low melting point made of lead, zinc, tin, cadmium, aluminum, copper, silver, or an alloy thereof on the surface of a round wire or strip of a high melting point metal material made of tungsten or molybdenum. It can be set as the structure coat | covered with the metal material.

  According to the present invention, the temperature rise within the rated current can be suppressed, the current limiting performance can be maintained, the breaking current at the time of fusing can be reduced, the influence of the temperature rise on the peripheral device can be eliminated, and the reliability can be improved. Can be improved.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
The basic structure of the high-voltage fuse according to the present embodiment is the same as that of the high-voltage fuse shown in FIGS. 4 and 5 except for the structure of the fusible body and the method for fixing the arc-extinguishing sand. That is, a linear or belt-like fusible body 3 is wound so as not to wrap around the outer circumference of the inner cylinder 1 having a star-shaped cross section, and the integral body of the inner cylinder 1 and the fusible body 3 serves as an insulating housing 6. The arc-extinguishing sand 7 serving as an arc extinguishing body is filled between the outer wall of the inner cylinder 1 and the inner wall of the cylindrical body 6, and both ends of the cylindrical body 6 are sealed with terminals 5. The inner cylinder 1 and the cylindrical body 6 are made of ceramic or high heat resistant resin having excellent insulation and heat resistance. The arc extinguishing body is not limited to the arc extinguishing sand 7. Other materials may be used as long as they can realize the conduction cutoff function in the fuse by condensing / dispersing the metal vapor at the time of melting the fusible body 3 and cooling the arc heat or ionized gas.

  FIG. 1 is a cross-sectional view of a fusible body 3 configured in a linear shape. The linear fusible body 3 shown in the figure has a structure in which the outer peripheral surface of a round wire 10 made of a high melting point metal material is covered with a metal coating material 11 made of a low melting point metal material. The characteristics of the refractory metal material are as described above. The low melting point metal material has a lower electrical resistance in the rated current region than the high melting point metal material and is composed of a metal material having a low melting point. For example, tungsten or molybdenum can be used as the high melting point metal material constituting the round wire 10, and the low melting point metal material constituting the metal coating material 11 can be lead, zinc, tin, cadmium, aluminum, copper, silver, or These alloys can be used.

  In this example, a low melting point metal material made of lead, zinc, tin, cadmium, aluminum, copper, silver, or an alloy thereof is electroplated on the surface of a round wire 10 of tungsten or molybdenum which is a high melting point metal material. It is covered. However, the present invention is not limited to the coating by the electroplating method, and lead, zinc, tin, cadmium, aluminum, copper, silver, or an alloy thereof may be bonded to the round wire 10 of the refractory metal material to form a clad structure. good. Alternatively, by depositing lead, zinc, tin, cadmium, aluminum, copper, silver, or an alloy thereof, the metal coating material 11 made of a low melting point metal material can be formed on the surface of the high melting point metal material.

  2 and 3 are sectional views of the fusible body 3 configured in a band shape. FIG. 2 is a cross-sectional view of the fusible body 3 cut in the longitudinal direction, and FIG. 3 is a cross-sectional view of the fusible body 3 cut in a direction orthogonal to the longitudinal direction. Instead of the linear soluble body 3 shown in FIG. 1, the belt-like soluble body 3 shown in FIGS. 2 and 3 can be used. The band-shaped fusible body 3 has a configuration in which a metal coating material 21 made of a low-melting-point metal material is formed on the surface of a band-shaped wire 20 made of a high-melting-point metal material. Tungsten or molybdenum can be used as the high melting point metal material, and lead, zinc, tin, cadmium, aluminum, copper, silver, or an alloy thereof can be used as the low melting point metal material.

  As described above, in the present embodiment, when the fusible body 3 is viewed in cross section, the low melting point metal material (11, 21) having the high melting point metal material (10, 20) as a core and having a low melting temperature in the periphery thereof. A coating is formed. The electrical conductivity is divided into a high melting point metal material (10, 20) and a peripheral low melting point metal material (11, 21), and the current flowing through the fusible body 3 of the fuse is also high melting point metal material (10, 20). And the low melting point metal material (11, 21). The cross-sectional area of the refractory metal material (10, 20) and the cross-sectional area of the low-melting metal material (11, 21) are arbitrarily set depending on the capacity of the high-voltage fuse and the current interruption characteristics.

  The fusible body 3 is wound around the outer periphery of the inner cylinder 1 with an interval so as not to wrap. Both ends of the fusible body 3 wound around the outer periphery of the inner cylinder 1 are spot-welded to a metallic retaining ring 2 wound around and fixed to both ends of the inner cylinder 1. In this way, the star-shaped inner cylinder 1 in which the fusible body 3 is installed is housed in the cylindrical body 6, and the sand 7 is filled between the outer wall of the inner cylinder 1 and the inner wall of the cylindrical body 6.

  Here, in the present embodiment, water glass is infiltrated and dried in order to fix the extinct sand 7. The extinct sand 7 is fixed to the tube wall by the permeated water glass to prevent scattering. Since the main component of water glass is sodium silicate, it becomes a glass component at high temperatures. For this reason, it vitrifies and reacts with the melt of the high-temperature fusible body 3 to produce a non-conductor but a non-conductive material and to prevent re-conduction.

  Hereinafter, the operation and effect when the fusible body 3 formed by forming the metal coating material 11 made of the low melting point metal material on the round wire 10 made of the high melting point metal material shown in FIG. 1 will be described. In addition, when using the strip | belt-shaped soluble body 3 shown in FIG.2 and FIG.3, there can exist the same effect.

  A high-voltage fuse including the fusible body 3 configured as described above is installed in the load circuit. In the rated current range, the current flowing through the fusible body 3 is divided into two parts, a high melting point metal material round wire 10 and a low melting point metal material covering material 11 coated on the surface thereof. The current flow is dominant in the metal covering material 11 of the low melting point metal material which becomes the arranged layer having high electrical conductivity. Therefore, the temperature rise is smaller than that of the high-voltage fuse using the refractory metal material round wire 10 alone as the fusible element 3.

  On the other hand, the operation when an overcurrent flows due to a short circuit or overload of a device or circuit connected to the secondary side of the load circuit is as follows. When an overcurrent flows through the high-voltage fuse, a current flows through the metal cover 11 of the low-melting-point metal material and the round wire 10 of the high-melting-point metal material that are covered with the fusible body 3, and can be changed depending on the resistance and the amount of current flowing. The solution 3 generates heat. First, the metal coating material 11 of the low melting point metal material coated on the fusible body 3 is melted.

  Although the cross-sectional area of the fusible body 3 decreases due to the melting of the metal coating material 11 of the low melting point metal material, the overcurrent concentrates on the round wire 10 of the high melting point metal material, but the resistance value of the round wire 10 of the high melting point metal material. The current flowing is limited. When a current further flows, the temperature of the fusible body 3 instantaneously rises due to the high resistance of the round wire 10 of the refractory metal material, reaches the oxidation and melting temperature of the round wire 10 of the refractory metal material, and the conduction is cut off.

  At this time, the water glass infiltrated into the arc-extinguishing sand 7 causes a reaction (endothermic reaction) such as self-decomposition or release of water by heat generated when the fusible body 3 is blown. Thereby, while raising the temperature of the melt of the soluble body 3 is suppressed and overheating is prevented, the arc extinguishing time is shortened. As a result, it is possible to suppress a rapid increase in the internal pressure of the fuse, and to prevent cracking and destruction of the fuse outer tube due to heat shock and overpressure. Moreover, the water glass reacts with the melt of the high-temperature fusible body 3 to form a non-conductive material, so that re-conduction is prevented and complete disconnection of the fuse is realized.

  As described above, according to the present embodiment, in the rated current range, a current flows in the low resistance portion of the metal covering material 11 made of the low melting point metal material of the fusible body 3, so that the temperature rises in the fusible body 3 and the fuse body. Can be suppressed, the influence of the temperature rise on the peripheral device can be reduced, and the reliability can be improved. Further, in the overcurrent region, overcurrent concentrates on the round wire 10 made of a high-melting-point metal material having a high resistance due to melting of the metal coating material 11 made of a low-melting-point metal material and detachment from the surface of the fusible body 3, and the temperature Since the current limit increases as the resistance increases due to the increase, a large current limiting effect can be obtained.

  The low resistance low melting point metal material (11, 21) to be coated is selected depending on the capacity of the fuse and the current limiting characteristic. The lower the melting point of the metal coating material, the lower the temperature rise during overcurrent. I can do it. Moreover, since the metal coating material (11, 21) melts at a low temperature in the process of increasing the temperature of the fusible body 3 at the time of overcurrent, the current limiting effect can be obtained in a faster time.

  Although the above embodiments have been described for the high-voltage fuse, the structure in which the surface of the fusible body (core wire portion) is covered with a low melting point metal material like the high-voltage fuse can be applied to a general power fuse and is a fusible body. By covering the surface of the core portion made of copper or silver with lead, zinc, tin, cadmium, or aluminum, which is a low melting point metal material, the low melting point metal material coated on the core portion of the fusible body 3 is overcurrent. It melts and scatters at the initial stage, and the cross-sectional area through which the current of the fusible body 3 flows decreases, so that the resistance value of the fusible body 3 increases, the temperature rises sharply, and the fusing time against overcurrent is shortened. is there.

  The present invention is applicable to a high-voltage fuse or a general power fuse used in a high-voltage circuit of 3 to 22 kV.

Sectional drawing of the fusible body in the high voltage fuse which concerns on embodiment Sectional drawing of the longitudinal direction of the fusible body in the high voltage fuse which concerns on the modification of the said embodiment Sectional drawing of the direction orthogonal to the longitudinal direction of the fusible body shown in FIG. Sectional view showing a configuration example of a high-voltage fuse XX sectional view shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Inner cylinder, 1a ... Projection, 2 ... Retaining ring, 3 ... Soluble body, 4 ... Connection piece, 5 ... Terminal, 6 ... Cylindrical body, 7 ... Arc-extinguishing sand, 10 ... Round wire (refractory metal material) 11 ... Metal coating material (low melting point metal material), 20 ... Strip line (high melting point metal material), 21 ... Metal coating material (low melting point metal material)

Claims (3)

In a fuse having an inner cylinder made of an insulator and a fusible body wound around the inner cylinder, the fusible body is blown by overcurrent,
The fusible body has a structure in which a high-melting-point metal material whose electrical resistance increases with a temperature rise is covered with a low-melting-point metal material whose electrical resistance is smaller than that of the high-melting-point metal material.   The inner cylinder around which the fusible body is wound is housed in a housing made of an insulating material, and an arc extinguishing body is filled in a gap between the inner cylinder and the inner wall of the housing. 2. The fuse according to claim 1, wherein the fuse is made of arc-extinguishing sand that has penetrated and is fixed in the gap. The fusible body is coated with a low melting point metal material made of lead, zinc, tin, cadmium, aluminum, copper, silver, or an alloy thereof on the surface of a round wire or strip of a high melting point metal material made of tungsten or molybdenum. The fuse according to claim 1 or 2, wherein the fuse is formed.

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