SU797617A3 - Fusible conductor - Google Patents

Abstract

In the case of the melting conductor it is intended that the fuse be capable of being stressed continuously up to the limit of its rated load capacity without any instabilities occurring in the melting material in this limiting-load region. In the case of relatively high currents in the lower overload region, the fuse is, however, nevertheless intended to be capable of burning through in a short time. In order to achieve this object, the fuse has a plurality of sections (14) of narrowed cross-section. In this case, at least one of these sections (15) is placed on a part along the melting conductor where the operating temperature is in the relatively low temperature range of the operating temperature distribution (17) along the melting conductor, and the cross-section of this section (15) is smaller, but its length is in contrast greater, than in the case of the other sections (14). <IMAGE>

Description

one

The invention relates to electrical engineering, in particular to the design of fused conductors of electrical fuses.

Electrical fuse conductors are known having sections of reduced section TI.

The disadvantage of this device is considerable inertia at elevated currents.

The closest to the present invention is a fusible conductor for low voltage electrical fuses, made in the form of a metal strip with portions of the narrowed section G2.

The disadvantage of this device. It is impossible to change the response time at insignificant current surges, as well as increase the service life at nominal load.

The purpose of the invention is to reduce the response time at minor current surges and increase the service life under the load rating.

The goal is achieved due to the fact that the famous fusible conductor

contains one narrowed section, the cross section of which is smaller, and the length is greater than the other sections with a narrowed section, with the specified section located closer to the end of the fused conductor, moreover, at the ends of the section with the smallest section and the greatest length, a metal may be applied or a metal alloy having a heat capacity and a melting point lower than the heat capacity and melting point of the fusible conductor, and the specified narrowed portion in the fusible conductor can

twice as long as

section in two) aza smaller than the length and width of the remaining narrowed sections.

FIG. G presents the fusible conductor; 2, the distribution of heat in the low-melting conductor (the ratio of the heating of the sections of the fusible conductor).

The fusible conductor 1 has sections of narrowed section, so-called bridges 2. These narrowed sections have a small length. At the end of the low-melting conductor there is a narrowed section 3, the names are two times smaller

.section and twice the length,

than the rest narrowed in 1astek. It should be noted that in the area with a greater length with the passage of current, a greater amount of heat occurs than in the area with a larger cross section and shorter length.

The presence of several short sections 2 of the narrowed cross section improves the cooling condition of the fusible element in such a way that itpvt is the largest current value that does not cause melting of the fusible element, the temperature distribution in the constricted areas differs little from the temperature distribution in the non-constricted areas. The presence of a section of a narrow section of a large length provides for the release of a large amount of heat on it and provides a large temperature difference in the sections of different sections 2 and 3.

In the cold state, the resistance of section 3 is four times the resistance of other areas, and in the state of thermal equilibrium, occurring at the highest but not yet melting melting current conductor, the resistance still increases due to the absolute temperature. With this curve 4, small temperature increases in areas 2 are shown, and thermal equilibrium of section 3 can occur only with a large temperature difference.

. .In the proposed melting edement

section 3 is made from the end of the fusible conductor 1, at a distance of 20-25% of the total length, i.e. at the end of the fusible conductor 1 so that the outside air temperature does not cause

. would dissipate heat. Thus, the heating curve 5 of this area is in the region of low temperatures. In this case, the thermal equilibrium of region 3 arises in the immediate vicinity of the unstable state, i.e. a rather small increase in temperature occurs, and a regime occurs in which the heat removal from the area becomes less than the formation of heat. Then a temperature peak occurs (curve 6) and the fusible element 3 melts.

The proposed device allows to bring together two critical values, namely the greatest current, but not yet causing the melting of the fusible element, and the lowest overload current, which causes the melting of the fusible element, in a short time. High short circuit currents cause thermal overturning. balance in all areas of the constricted cross section at the same time and in all areas there is a multiple short arc arc. The advantage of the occurrence of a multiple electric arc is that simultaneously in several places channels of molten fusible material appear that not only limit the passage of current, but also increase the limiting value of the voltage. Increases .c also intensity-hash-arc.

The heating characteristic of section 3 and the thermal regime can be varied over a wide range by depositing on the constricted section 3. at the points at which this section comes into contact with the greatest surface of an ox5, a binding, a metal, such as silver or a metal alloy, having a heat capacity and a melting point than the fusible conductor itself. You can also use 0 glass bead. The presence of this metal or alloy retards heating of region 3 and, thus, any melting characteristic can be achieved.

Claims (2)

1. A hot-melt conductor for low-voltage electrical fuses, made in the form of a metal strip with sections of a narrowed section, is about. u with the fact that, in order to reduce the response time at minor current surges and increase the service life at nominal load, it contains one narrowed section, the cross section of which is smaller and longer than the other sections with narrowed section, and closest to the end of the fuse conductor. 2. A conductor according to claim 1, characterized in that at the ends of the section with the smallest cross section and the greatest length there is applied a metal or metal alloy having a heat capacity and melting point lower than the heat capacity and melting point of the fusible conductor. , 3 Conductor on PP ;. 1 and 2, characterized in that said narrowed portion is twice as long, and the cross section is two times smaller than the length and width in the remaining sections with narrowed cross section. Sources of information, pr 5: s taken into account in the examination 1. The patent of Germany No. 1281539, cl. 21 C 70, 1968. 2. The patent of France 1 .2062960, cl. H 01 and 85/00, 1971. а о а а а d О About 1 P