JPS62108421A - Self-reset current limitter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention uses high-resistance metal to limit the current for large currents that may cause damage to wiring equipment, such as short-circuit currents, overload currents, etc. This invention relates to a self-restoring current limiting device that exhibits good conductivity if the current returns to normal.

[Conventional technology]

The drawing shows, for example, a conventional self-restoring current limiting device disclosed in Japanese Utility Model Publication No. 53-53060, and in the drawing,
(1) is the first electrode, which is made of a conductive metal, such as copper or copper alloy, and is formed into a cylindrical shape. One end has a terminal screw for screwing the bus bar, and a terminal screw is threaded in the center of the electrode. A female thread is formed on the bottom. (2) is an insulating tube, which is made of a heat-resistant, alkali-resistant material such as porcelain, and has one end in contact with the first electrode tube (1). (
3) is a metal reinforcing tube, which is formed into a cylindrical shape and has a hollow hole inside, and houses the electrode tube (1) and the rounded tube (2), one of which is made of a metal reinforcing tube. (4) is a thermoplastic insulator made by molding powder of glass, mica, etc. together with the first electrode tube (1), metal reinforcing tube (3), and insulating tube (2) after firing at a high temperature. The metal reinforcing cylinders (1) and (3)' are insulated from each other, and these and the insulation Wt (2) are integrally fixed. (5) is a second electrode made of a conductive metal, such as copper or a copper alloy, and a male screw provided on the outer periphery is screwed into the acid screw provided in the hollow hole of the metal reinforcing cylinder. It is fixed to the reinforcing tube (3). (7) is made of an alkali metal such as sodium, and when a current that should be limited, such as a short circuit current or an overload current, passes through it, it vaporizes and becomes an insulator due to the Joule heat generated by the current, and when the current is constantly on. is a current limiting material that is a good conductor of electricity,
(6) is this current limiting material (7) a sealing material that completely seals, (8
) is a movable piston provided in the hollow bottomed hole of the second electrode (5) so as to be actuated in the axial direction by the vaporization of the current limiting material (7), and (9) is a recessed portion of the piston (3). αQ is a spacer inserted into the hollow hole of the second electrode (5) to maintain airtightness between the current limiting material (7) and the pressure buffer fluid (2) described below. When the restricting material (7) is vaporized, it receives the impact of the piston (3). (2) is a pressure buffer fluid made of an inert gas that cushions the impact on the piston (8) due to the vaporization of the current limiting material (7); (B) is a sealing body for sealing the pressure buffer fluid (2); It is.

Next, the operation will be explained. When a short circuit current flows, the current limiting material (7) filled in the insulating tube (2) is heated by self-Joule heat and vaporized. When vaporization occurs, the specific resistance of the current limiting material (7) increases rapidly, and the short circuit current is significantly limited. The current limiting material (7) becomes high-pressure plasma by vaporization, so the pressure in the inner hole in the insulation 8 (2) increases, but the piston (8) moves to the right in the drawing, reducing the pressure. The increase will be suppressed. The insulating tube (2) is reinforced by the metal reinforcing tube (3) via the Fi insulator (4), so it will not be damaged by the pressure suppressed by the piston (3).

The limited current is cut off by a series switch (not shown). After the shutoff, there is no energy input to the self-recovery current limiting device, so the vaporized current limiting material (7) is cooled and returns to a solid or liquid state.

Therefore, the pressure in the inner hole of the insulating cylinder (2) also decreases, and the piston (8) is pushed back by the force of the pressure buffer fluid (2) and self-recovers to the state before operation.

[Problem that the invention seeks to solve]

The conventional self-restoring current limiting device is constructed and operated as described above, but when an overload current flows continuously, the self-Joule heating of the current limiting material (7) causes the current limiting device (7) to be made of a thermoplastic material. Since the insulator (4) softens, the current limiting material (7) often leaks to the outside. Furthermore, if a short circuit occurs while the insulator (4) is softened and the current limiting material (7) evaporates, there is a risk that the self-restoring current limiting device may explode.

This invention was made to solve the above-mentioned problems, and its purpose is to obtain a self-restoring current limiting device in which the insulator (4) does not soften even if an overcurrent flows for a long time. .

[Means for solving problems]

In the self-restoring current limiting device according to the present invention, the insulator is made of a non-thermoplastic material.

[Effect]

Since the insulator in this invention is made of a non-thermoplastic material, even if an overcurrent flows for a long time and the temperature of the current limiting material rises, the insulator will not easily soften. An embodiment of this invention will be described.

The structure of the self-restoring current limiting device according to an embodiment of the present invention is exactly the same as the conventional self-restoring current limiting device shown in FIG. In the present invention, a non-thermoplastic material such as low temperature fired porcelain is used as the insulator (4). Low-temperature-fired porcelain is mainly composed of silica sand and clay, and is fired with a binder added, such as Toughlite (trade name, manufactured by Nihon Koatsu Denki Co., Ltd.). Such low-temperature fired porcelain can be molded into complex shapes by injection molding, and can be fired at a temperature of around 650°C in about two hours. Therefore, the raw material for such low-temperature fired porcelain? It is preferable to inject it into the self-recovery current limiting device in advance and then bake it.

Since the operation of the self-restoring current limiting device of the present invention is almost the same as that of the conventional current limiting device, only the differences will be explained below. When an overcurrent flows through the self-restoring current limiting device of the present invention for a long period of time, the current limiting material (7) is heated by self-Joule heating, and this heat is transferred to the insulator (4). Increase temperature.

However, in the present invention, since a non-thermoplastic material is used as the insulator (4), it is possible to prevent the softening phenomenon of the insulator (4) as in the conventional case.

〔Effect of the invention〕

As described above, according to the present invention, since a non-thermoplastic material is used as the insulator, it is possible to prevent the current limiting material from leaking outside due to softening of the insulator. Furthermore, since the insulator is less likely to soften, the self-restoring current limiting device is less likely to explode in the event of a short-circuit accident.

[Brief explanation of drawings]

The figure is a sectional view showing the entire self-restoring current limiting device according to a conventional method and an embodiment of the present invention. In the figure, (1) is the first electrode, (2) is the insulating cylinder, (
3) is a metal reinforcing tube, (4) is an insulator, (5) is a second electrode, and (7) is a current limiting material.

Claims (2)

[Claims] (1) A first electrode, a second electrode with a built-in pressure buffer, an insulating cylinder having an inner hole provided between the first electrode and the second electrode, and filling the inner hole of the insulating cylinder. a current limiting material, a metal reinforcing tube provided on the outer periphery of the insulating tube, and an insulator provided between the metal reinforcing tube and the insulating tube to insulate the first electrode and the second electrode. A self-restoring current limiting device, wherein the insulator is made of a non-thermoplastic material. (2) The self-restoring current limiting device according to claim 1, wherein the non-thermoplastic material is low temperature fired porcelain.