JPS6116593Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention relates to an improvement of a current limiting device used to protect an electric circuit.

[Prior art]

FIG. 1 is a vertical cross-sectional view showing the configuration of a conventional current limiting device. In the figure, 1 and 2 are a first electrode and a second electrode, respectively, 3 is an insulator that insulates the electrodes, 3a,
3b is a reduced hole and a large hole drilled in the insulator 3, and 4 is a conductor filled in the through holes 3a and 3b of the insulator 3, such as an alkali metal or mercury. 4a is a reduced portion of the conductor 4 filled in the reduced hole 3a;
b is the thick portion thereof, and 5 is an intermediate electrode taken out from the boundary between the reduced portion 4a and the thick portion 4b. In the current limiting element 6 having the above configuration, a first parallel resistance 7a is connected between the first electrode 1 and the second electrode 2, and a second parallel resistance 7b is connected between the first electrode 1 and the intermediate electrode 5. Connected.

In the current limiting device configured as described above, when an overcurrent flows through the current limiting element 6, the reduced portion 4a and the thick portion 4b become high resistance plasma several hundred times the room temperature resistance as described above, and the first The resistance between the electrode 1 and the intermediate electrode 5 is the combined resistance of the plasma resistance and the second parallel resistance 7a connected in advance, and the resistance between the first electrode 1 and the intermediate electrode 5 appears as a shared voltage of the voltage across the current limiting element 6. The voltage is smaller than that in the case without the second parallel resistor 7a, and the energy injected into the reduced portion 4a is significantly reduced.

As a result, wear and deterioration of the reduced hole 3a are significantly reduced, and a current limiting device that can be used with significantly reduced changes in electrical characteristics due to repeated current limiting operations of the current limiting element 6 is made possible.

However, the conventional device having the above configuration has the disadvantage that the current limiting element 6 is damaged by the explosive pressure caused by the vaporization of the conductor 4.
Another drawback is that it is not easy to determine the voltage to be shared between the reduced portion 4a and the thick portion 4b.

[Summary of the idea]

This idea was made with attention to the above points, and in a self-restoring type current limiting device, an intermediate electrode is provided at the boundary of the contracted part, and the intermediate electrode is connected between each of the two main electrodes. The present invention provides a current limiting device equipped with a resistor.

[Example of idea]

An embodiment of this invention will be described below.

Fig. 2 is a partial detailed view of the self-restoring current limiting device used in this invention. A piston 9 is placed inside via an O-ring 8, an inert gas is filled in a buffer chamber 10 formed between the piston 9 and the bottom of the second electrode 2, and the insulator 3 and the second electrode 2 are placed inside the outer cylinder 11. It is loaded with. Other parts are the same as in FIG.

FIG. 3 shows the overall configuration including that shown in FIG.

In the figure, 1 to 6 are the same or equivalent parts as in FIG. 1, and 6a and 6b are parallel resistors connected between the intermediate electrode 5 and the first and second electrodes 1 and 2, respectively. The current-limiting operation of the current-limiting element 6 is as described above, but the voltage shared by the narrow portion 4a and the thick portion 4b during the current-limiting period is mainly determined by the ratio of the parallel resistors 6a and 6b. By appropriate selection, wear and deterioration of the reduction hole 3a can be further significantly reduced.

With the above configuration, the voltage shared by the reduced portion 4a and the thick portion 4b can be easily determined, and the current flowing through the reduced portion 4a can be appropriately shunted to the resistor 6b. Further, the explosive pressure generated when the conductor 4 is vaporized is buffered by the movement of the piston 9 and the sealing O-ring 8 in the buffer chamber. When the electric circuit is opened by the operation of a circuit breaker (not shown) installed in the electric circuit, the conductor 4 is cooled and the pressure decreases, and the piston 9 and O-ring 8 return to their original positions. It is something.

[Effect of idea]

As explained above, this invention provides an intermediate electrode in the reduced portion of the current limiting element, connects resistors between this intermediate electrode and both main electrodes, and provides a buffer chamber, thereby reducing the energy input to the reduced through-hole portion of the current limiting element and therefore reducing damage to this portion.

[Brief description of the drawings]

Figure 1 is a longitudinal sectional view showing a conventional current limiting device;
The figure shows an embodiment of this invention, and FIG. 2 is a longitudinal sectional view. In the figure, 1 is the first electrode, 2 is the second electrode, 3
3a is an insulator, 3a is a reduced through hole, 3b is a thick through hole, 4 is a conductor, 4a is a reduced portion, 4b is a thick portion, 6a and 6b are parallel resistors, and 5 is an intermediate electrode. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of utility model registration request] an insulator in which a through hole consisting of a reduced hole and a large hole is formed; a first electrode connected to an end of the reduced hole of the insulator; and a hollow cylindrical shape that is connected to an end of the large hole and has an open top. a second electrode, a vaporizable conductor filled in the through hole, an intermediate electrode protruding from the boundary between the reduced hole and the large hole, and between the first electrode and the intermediate electrode. and a first connected between the intermediate electrode and the second electrode, respectively.
A current limiting device comprising: a second parallel resistor; a piston that forms a buffer chamber between the bottom of the second electrode; and an inert gas sealed in the buffer chamber.