JPS6168824A - Power fuse - 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] [Technical field to which the invention pertains] This invention uses the main fusible body to handle fault currents in large current areas such as short-circuit currents, and the upper series equipment in overload areas below the minimum breaking current. The present invention relates to power fuses each having an overcurrent indicator that shuts off upon application of a trip command.

[Prior art and its problems]

The material of the main fusible body of the fuse is generally a wire rod such as pure silver, and although there are some differences depending on the shape and tension of the fusible body, the fusing characteristics are shown in Figure 6 on the vertical axis with time t,
As shown by curved edge 1, which shows the current I on the horizontal axis, it has a relatively steep slope.

Moreover, this fusing characteristic is small [in the light region, the fusing time is extremely long and varies greatly because the light region is close to the vertical axis corresponding to the minimum fusing current.

On the other hand, the deterioration characteristics of a protected device, such as a transformer, are as shown by curve 2, and a fuse having the fusing characteristics of curve 1 cannot maintain the current range below point P. Therefore, conventionally, to protect such a relatively small overcurrent area, other series devices were cut off, and it was necessary to separately install a thermal overload coupling LTC device as an overcurrent detector. This has the disadvantage of making the circuit Va complicated and expensive.

Purpose of the Invention] In view of the above, the purpose of the present invention is to issue a trip command to the upper series equipment without blowing out the main fusible body, not only when the main fusible body is cut off, but also in an overload region below the minimum breaking current. An object of the present invention is to provide a power fuse equipped with an overcurrent indicating device capable of detecting overcurrent.

[Key points of the invention]

The main point of this invention is to achieve the above-mentioned object by providing a first quadruple conductor cap and a second conductive sleeve having a conductive sleeve on the same axis.
A main fusible body stretched between both conductive carriers in a hollow insulating cylinder whose both ends are sealed with conductive caps, and a first conductive cap provided between the two conductive caps and connected at one end to the first conductive cap. Displayed soluble material.

A display pin is supported by the conductive sleeve, which contacts and separates from the other end of the display fusible body, through an insulator so that it can move forward and backward.

An indicator spring made of a unidirectional shape memory alloy that has one end fixed to the indicator pin and the other end wrapped around the conductive sleeve and operates the indicator pin by capturing a temperature rise caused by an overcurrent in the main fusible body. The present invention is intended to construct a power fuse with a current display device and issue a trip to a higher-order series device without blowing out the main fusible body in an overload region where the current is below the minimum breaking current.

[Embodiments of the invention]

1 to 3 show an embodiment of a power fuse according to the present invention, and FIG. 1 is a longitudinal sectional view.

FIGS. 2 and 3 are side views showing the state of main parts, respectively. As shown in the figure, the hollow insulating tube 3 is sealed at one end with a first conductive cap 4 and at the other end with a second conductive cap 5. The sleeve 6 is recessed. A plurality of parallel main fusible bodies 7 are stretched between both conductive caps 4 and 4.5, and the first conductive caps 4 and 41! There is an insulator 8111 between the insulator 8 provided at the end of the sleeve 6! A display fusible body 10 is stretched across a connecting fitting 9 with I as a forward/retreat mark. And hollow insulating cylinder 3P
'3 is filled with an arc extinguishing agent 11, and the conductive sleeve 6 houses the portion of the overcurrent display device other than the display fusible body 1O. The overcurrent display device consists of the aforementioned connecting fitting 9Σ, the display fusible body 10, the insulating tube 12 fixed to the inner wall of the four-conductor sleeve 6, and the insulating tube 12, which is movable in the axial direction, with one end attached to the end surface of the connecting fitting 9. The display pin 13 has a flange that can be brought into contact with and separated from it, and when it comes back into contact, the surface position of the end surface of the four-conductor sleeve 6 is -m. The indicator spring 15 is wound through the conductive sleeve 6 and has the other end connected to the inner wall of the conductive sleeve 6.

The display spring 15 is a frustoconical tension coil spring made of a unidirectional shape memory alloy, and its shape changes when the temperature (temperature rise value + ambient temperature) slightly exceeds the rated current applied to the main fusible body 7. It is made to change suddenly, and below the shape recovery temperature, it is in a contracted state as shown in Figure 2, and in the state shown in Figure 1, it is elongated than its free length.

Therefore, contact pressure is applied by the display spring to the contact between the display pin 13 and the connecting fitting 9. Furthermore, the third
The figure shows a case where a current slightly exceeding the rated current flows through the main fusible body 7 and the shape suddenly changes, that is, when the display pin 13 is in the protruding state shown by the chain line in FIG.

In the above configuration, when a large current such as a short-circuit current flows through the fuse, the main fusible body 7 first fuses and fires, and then the current flows to the display fusible body 10 and can be displayed. A current flows through the display bottle 13 - display spring 15 - conductive sleeve 6 - conductive cap 5 in this order. Therefore, displayable m body 1
0 flows through the indicating fusible body 10 until 0 interrupts the current.The current flows through the indicating spring 15 and its Joule heat and the main fusible body 7
Joule heat. The display spring 15 is heated by the arc heat, and when it reaches the shape recovery temperature, it rapidly expands and assumes the shape shown in Figure 3 as described above, causing the display bin 13 to protrude and the operation of the overcurrent display device being completed. And the short circuit current is the main fusible body 7
is blocked by In addition, since a unidirectional shape memory alloy is used for the material of the display spring 15, the display spring 1
Even if the temperature of the display pin 13 falls below the shape recovery temperature, the display pin 13 will not return to its original state. Next, when a fuse overload current flows, the indicator spring 10 is heated due to the temperature rise of the main fusible body 7, and when the indicator spring reaches its shape recovery temperature due to this heating,
The indicator pin 13 is projected before the main fusible body 7 is fused, and the force of the indicator pin 13 that is projected can be used, for example, to operate a microswitch and disconnect the upper series switching device, or to remove the indicator pin 13. By tripping the upper series switching equipment in series using the ejection force of No. 13, overload protection becomes possible without the need for particularly attaching an overload detector. After the overcurrent is cut off by the series switching device, the indicator spring 15 will not be able to return the indicator spring 13 even if the temperature drops thereafter, based on the characteristics of the unidirectional shape memory alloy, because the insulating chain 12 and 14 is provided to ensure that the current after the main fusible body 7 is blown out passes through the above-mentioned path and flows to the display spring 15.

Next, different embodiments of the power fuse of the present invention shown in FIGS. 4 and 5 will be described with reference to the reference numerals corresponding to the differences from the embodiment shown in FIG. 1 described above. First, the difference between the embodiment shown in FIG. 4 is that the insulating chain 12 and 14 shown in FIG. The surface of the display spring 15 is coated with an insulating material except for the connection part with the display bottle 13, which is the lower end of the display spring 15, and the connection part with the conductive sleeve 6, which is the lower end of the display spring 15. Therefore, since there is no functional difference from the embodiment shown in FIG. 1, a detailed explanation of the operation will be omitted. The difference between the embodiment shown in FIG. 5 is that the overcurrent display device is provided coaxially with the outer side of the hollow insulating cylinder 3 that houses the main fusible body 7 and the display fusible body 10. In this case, the effect of heat will change slightly due to the melting and ignition of the main fusible body 7 when a large current such as a short-circuit current flows, but the operation after commutation and the operating characteristics during overload will change. Since there is no such thing, the following explanation will be omitted.

7.i' In all of the above embodiments, the overload display device is installed above the main body, but it goes without saying that it may be installed below the main body, that is, for inversion. According to these embodiments, there is also the advantage that there is no need for a connecting wire for keeping the display spring (compression spring) in a compressed state, which is essential in any conventional fuse blowout display device.

〔Effect of the invention〕

According to this invention, by using a unidirectional shape memory alloy as the material of the display spring of the overcurrent display device included in the fuse, the main fusible body itself can not only cut off the current 'lf;
Since it is possible to display an indication even in an overload region, it is possible to provide a power fuse equipped with an overcurrent display device that can be maintained through a series switching device.

[Brief explanation of drawings]

1 to 3 are diagrams showing an embodiment of the power fuse according to this invention, in which FIG. 1 is a longitudinal sectional view, and FIG. 2 is a side view showing a state where the main part is below the recovery temperature. Fig. 3 is a side view showing a state in which the recovery temperature of the main part is exceeded; Figs. 4 and 5 are views showing different embodiments of the power fuse according to this invention; Figure 5 is a vertical cross-sectional view, Figure 6
The figure is a diagram for explaining the operating characteristics of a conventional power fuse. 3...Hollow insulating cylinder, 4.5...Conductive cap, 6.
... Conductive sleeve, 7... Main fusible body, 8... Insulator, 10... Display fusible body, 13... Display pin, 15...
-・Display spring. Figure 2 Figure 3 Figure 5 Figure 6

Claims (1)

[Scope of Claims] 1) A main fusible body stretched between both conductive caps in a hollow insulating part whose both ends are sealed with a first conductive cap and a second conductive cap having a conductive sleeve coaxially; A display fusible body provided between the conductive caps and having one end connected to the first conductive cap, and a display supported movably forward and backward via an insulator on the conductive sleeve that comes into contact with and separates from the other end of the display fusible body. pin, an indicator spring made of a unidirectional shape memory alloy that has one end fixed to the indicator pin and the other end connected to the conductive sleeve and operates the indicator pin by capturing a temperature rise caused by an overcurrent in the main fusible body. A power fuse characterized by comprising an overcurrent indicating device. 2) The power fuse according to claim 1, wherein the display spring is a coil spring, and the display spring expands when the temperature reaches a shape recovery temperature or higher. 3) The power fuse according to claim 1 or 2, characterized in that the display spring is electrically connected in series with the display fusible body and electrically connected in parallel with the main fusible body. and power fuse. 4) In the power fuse according to claims 1 to 3, the indicator spring is used as a tension spring below the shape recovery temperature to apply contact pressure to the contact portion between the indicator fusible body and the indicator pin. A power fuse characterized by: