JP5229646B2 - Current fuse - Google Patents

Description

Detailed Description of the Invention

Industrial application fields

The present invention relates to a current fuse for an electrical component.

The shock wave generated when the current fuse explosively interrupts the overcurrent is reflected and converged in the fuse container to focus on the fuse wire, and the arc generation is suppressed by the pressure rise caused by the shock wave, and the current is stabilized. A shock wave-utilizing fuse that is interrupted in a short time is known in Patent Document 1). However, since the shock wave has a short duration, there is a case where the atmospheric pressure increase state necessary for arc suppression does not continue and a stable interruption may not be obtained.

1) Japanese Patent No. 3966114 The patent is the same as the inventor / applicant of this application.

1) The Institute of Electrical Engineers of Japan (1969) University Lecture “Ionized Gas Theory” published by Ohmsha P199-210. 2) ISSW (2009 International Shockwave Society) report (2009) English text Kazuyoshi Takayama, Kiyonobu Otani, Tadaji Umeda. 3) "Condensation coefficient of thick orifice for compression flow", Japan Society of Mechanical Engineers, Vol. 55, No. 515 / 1989-7 Hirahara et al., P175-1788. 4) “Introduction to Fluid Mechanics” Nagoya University Graduate School of Engineering, Fluid Mechanics Course Chapter 6 Shock Waves Page 33-34, Rankin Yugonio's equation of state.

It is an object of the present invention to obtain a sufficient time necessary for suppressing the occurrence of arc by extending the duration of the atmospheric pressure rise state in which the shock wave is generated by reflecting and converging the shock wave on the fuse wire.

As the fuse wire explosively melts and vaporizes due to an excessive current, a shock wave is generated and reflected on the unfused residual fuse wire to converge and increase the pressure condition due to the shock wave, increasing the voltage condition for arc generation. The basic concept of a shock wave-utilizing fuse is to suppress arc generation. It is derived from Paschen's law (Non-Patent Document 1) that whether arc generation occurs or can be suppressed at the time of interruption can be determined by the applied voltage of the fuse and the atmospheric pressure around the fuse wire.

This is precisely realized when the interrupting current is very short and in relatively small fuses.
However, it does not always work effectively when the fuse is large.

When observing the breaking operation with an oscilloscope by the voltage and current across the fuse, the current once drops to be cut off immediately after the application of the excessive current, but the current increases again and an arc is generated and the breaking fails. (Figure 1)

FIG. 2 (Non-Patent Document 2) shows the measurement results of shock wave and pressure increase due to excessive current.
In this measurement example, the pressure increase due to the shock wave has reached 20 to 30 atmospheres, and since the arc generation voltage according to Paschen's law (Non-patent Document 1) is greatly exceeded, no arc should occur in any fuse.
However, as is clear from the figure, the duration of the shock wave is at most 200 nanoseconds (-0.000002 seconds).
Since this figure is a measurement result of open space, it seems that it will last longer than this in the case of a packaged fuse, but even in that case, it seems that the air pressure rises instantaneously and then diffuses to the entire fuse container relatively quickly .

Satisfactory results can be obtained even if the fuse is small, but the duration of the pressure required to cut off the current due to the shock wave is low because the time required to cut off the normal fuse is 0.001 to 0.010 seconds. There is a problem that is slightly lacking.

The process up to the stage where the shock wave generated when the fuse wire is explosively melted and vaporized is reflected by the concave spherical inner wall of the fuse container and converged to the focal point is in accordance with Patent Document (1). It is characterized in that a shock wave whose energy density is increased by convergence is guided to a small space sealed through the pores.

First, according to the shock wave passing through the pore (Non-Patent Document 2), the process by which the shock wave passes through the pore is elucidated. (Figure 3)

Next, in a small space closed except for the pores, the kinetic energy of the shock wave becomes the energy of pressure by the energy conservation law, and the atmospheric pressure in the small space rises. This is due to the development of the shock wave equation of state (Rankin Yugonio's equation of state). (Non Patent Literature 3)

An undissolved remaining portion of the fuse wire is located in the small space, and Paschen's law is applied at this location, and the arc is suppressed by the increased atmospheric pressure.
Since it takes some time until the pressure that has risen from the pores into which the shock wave has entered leaks, the blocking operation is completed during that time.

Example 1 is shown in FIG. A shock wave-use fuse that secures a shock wave path by expanding the cross-sectional area of the hole through which the fuse wire passes on the elliptical concave curved wall of the fuse and communicates it with the adjacent small space is shown.
FIG. 6 shows the result of the blocking test of the product of the present invention.

In addition to the communication path shared with the fuse wire path in the embodiment of FIG. 4, a shock wave-utilizing fuse that secures a shock wave path by making a separate hole in the elliptical concave curved wall of the fuse and communicates with an adjacent small chamber is shown in FIG. Shown in
This is to secure a shock wave path even when the fused fuse wire in Example 1 blocks the pores of the fuse wire.

  It is a voltage / current waveform when the interruption is unsuccessful. It is the figure extracted from nonpatent literature 2). Measured pressure during explosive melting and vaporization due to overcurrent of fuse wire. Energized 250VAC100A in open space to Φ0.3mm × 40mm length. The pressure axis is 1 MPa / Div. The time axis is 200 nanoseconds / Div. (= 2 × 10 ⁻⁴ milliseconds).   It is an excerpt from Non-Patent Document 3).   Patent Document: Drawing extracted from Japanese Patent No. 3966114 for reference.   Example 1. It is the Example of the shock wave utilization fuse provided with the reflective wall which has the pore shared with the path | route of a fuse wire, and a small space.   Example 2. It is an Example of the shock wave utilization fuse provided with the reflecting wall and small chamber which provided the pore. In addition to the passage shared with the fuse wire, another small hole is provided in the reflecting wall.   FIG. 6 is a voltage / current waveform when the interruption is successful according to the first embodiment. FIG.

DESCRIPTION OF SYMBOLS 1 Insulation member 2 Current supply member 3 Fuse wire 4 Reflective concave curved surface 5 Convergence focal point 6 of shock wave Solder 7 Communication path 8 Small space 9 Additional communication path

Since the arc extinguishing technique of the fuse according to the present invention does not include arc extinguishing sand, it is suitable for a fuse in which the wear deterioration of the fuse wire due to the arc extinguishing sand is concerned due to vibration of the installation place. Moreover, since arc-extinguishing sand is not a constituent requirement, when the breaking current is a relatively light overcurrent that is about twice the rated current, reliable breaking can be achieved without concern about re-arcing.

Claims (1)

The shock wave generated when the fuse wire explosively melts and vaporizes due to overcurrent is reflected and converged on the fuse wire to increase the pressure and suppress the arc generation. A method of extending the time for introducing an additional small space to increase atmospheric pressure and maintaining the atmospheric pressure to suppress arc generation, and a current fuse having this structure.

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