EP3264439A1 - Fuse link and overload protection device - Google Patents

Abstract

The fusible conductor (10) according to the invention for an overcurrent protection device (1) has an elongated main body extending in a longitudinal extension direction (L) whose first end (14) has a first contact region for contacting a first contact element (4) of the overcurrent protective device. Protective device (1), and the second end (15) has a second contact region for contacting with a second contact element (5) of the overcurrent protection device (1). Between the first contact region and the second contact region a plurality of bottleneck rows (11) are arranged, each having a plurality of holes (16), which in turn are arranged transversely to the longitudinal direction (L) of the fusible conductor (10). In a center region (12) of the fusible conductor (10) arranged centrally between the first contact region and the second contact region, two of the rows of bottlenecks (11-1, 11-2) have a smaller distance (a 1) than the other rows of bottlenecks (11). Furthermore, the fusible conductor (10) has at least one additional connection conductor (17, 18), which is electrically conductively connected to the fusible conductor, in this middle region (12). With the aid of the additional connection conductor (17, 18), the two bottleneck rows (11-1, 11-2) of the fusible conductor (10) arranged in the central region are specifically thermally pre-stressed by means of a predefined control current. In this way, the tripping characteristic of the fuse conductor (10), and thus the tripping characteristic of the overcurrent protection device (1) can be varied, whereby a more flexible adaptation to the respective conditions of use is possible.

Description

The invention relates to a fuse element for a fuse, for example for a semiconductor protection fuse, so-called HLS fuse, or a low-voltage high-performance fuse, so-called NH fuse. Furthermore, the invention relates to an overcurrent protection device, for example a fuse, which has at least one such fusible conductor.

Conductors, which are traversed by an electric current, heat up. With inadmissibly high currents it can lead to an inadmissibly strong heating of the conductor and consequently to a melting of the insulation surrounding the conductor, which can result in the consequence up to a cable fire. To prevent this risk of fire, if excessive electrical current, i. an overload current or a short-circuit current, this electrical current can be switched off in good time. With the help of a so-called overcurrent protection device this is guaranteed.

An example of such an overcurrent protection device is, for example, a fuse that interrupts the circuit by the melting of one or more fuse links, when the current strength of the circuit protected by the fuse exceeds a certain value over a certain period of time. The fuse consists of an insulating body, which has two electrical connections, which are electrically connected to one another in the interior of the insulating body by one or more fuse elements. The fusible conductor, which has a reduced in cross-section compared to the other conductors of the circuit, is heated by the current flowing through it and melts when the relevant rated current of the fuse for a predetermined period of time is clearly exceeded. Due to its good insulation properties is used as the material for the insulating body mostly ceramic. Such a fuse insert is for example from the European patent EP 0 917 723 B1 known.

Fuses are available in various designs. In addition to simple device fuses, which have a simple glass cylinder in which the fusible conductor is added, there are also designs in which the ceramic body with sand - usually quartz sand - is filled: Here, a distinction between types with solidified and with unconsolidated quartz sand. In a sand-solidified fuse, the melt conductor is surrounded by quartz sand. As a rule, the housing of the fuse is formed by a ceramic body in which the solidified sand, the electrical connections and the fusible conductor are accommodated or held. The quartz sand acts here as an arc extinguishing agent: the rated current of the fuse is clearly exceeded - for example, due to a high short-circuit current - so this leads to a response of the fuse, in the course of which the fusible conductor melts first and then evaporated due to the high temperature development. This creates an electrically conductive plasma, via which the current flow between the electrical connections is initially maintained - it forms an arc. As the metal vapor of the vaporized fusible conductor precipitates on the surface of the silica sand grains, the arc is again cooled. As a result, the resistance in the interior of the fuse link increases in such a way that the arc finally disappears. The to be protected by the fuse electrical line is interrupted.

From the state of the art in the field of fuses low-voltage high-performance fuses, so-called NH fuses, but also semiconductor fuses, so-called HLS fuses, such as those sold under the product name SITOR, in principle already known. NH fuses typically use one or more fuse links in the form of copper tapes. Each of these fusible links has so-called bottleneck rows for selectively switching off the fuse. Furthermore, at least one solder deposit can be applied to one or more of the fuse elements, with the aid of which the overload characteristic of the fuse can be influenced. NH fuses serve, for example, to protect equipment or control cabinets against fire, for example due to overheated connection cables. The let-through energy value I ² t, which is decisive for the turn-off behavior of the fuse, is relatively large for NH fuses, which is why they have a rather sluggish characteristic.

If the fusible conductor is heated by an electrical overload current to a temperature which is above the melting temperature of the solder, this solder diffuses into the fusible conductor material and forms an alloy with it. As a result, the electrical resistance of the fusible conductor increases, which leads to its further heating, whereby the diffusion process is further accelerated until the fusible conductor in the vicinity of the solder deposit is completely dissolved, so that it breaks off, whereby the current flow is interrupted. In the case of a brief, permissible overcurrent, the NH fuse does not prematurely switch off. On the other hand, when a short-circuit current occurs, the fusible conductor ruptures at the bottleneck rows. This results in several small arcs connected in series at the same time, whose voltages add up and thus lead to a faster deactivation of the fuse. NH fuses serve, for example, to protect equipment or control cabinets against fire, for example due to overheated connection cables. The transmission energy value I ² t, which is decisive for the shutdown behavior of the fuse, is relatively large for NH fuses, which is why it has a slower characteristic exhibit. Semiconductor protection is therefore generally not feasible with NH fuses.

Semiconductor fuses which protect high-quality components and components, for example power semiconductors, from the harmful effects of a short circuit are also known from the prior art. Due to their significantly faster turn-off characteristic, semiconductor fuses are used, for example, in the rectifier section and in the DC link of converters, but also in UPS systems and in soft starters for motors. They are usually characterized by a higher power loss, which is why mostly silver is used as the fusible conductor material.

The turn-off characteristics of a fuse are therefore largely determined by the design of the fuse conductor. This has an influence on the switchable voltage, the heating in general, the time-temperature behavior in the melting as well as the extinguishing or switch-off phase, and thus on the melting and the turn-off I ² t value. In this case, a disadvantageous design of the fusible lead to problems in the shutdown of the fuse, for example, due to low arc tension, body tears of the fuse body or bursting of the fuse with subsequent arc leakage due to excessive heating. Furthermore, a disadvantageous design of the fusible conductor can lead to the fuse having excessively high melting or turn-off I ² t values.

Usually, the switching behavior of the fuse by the selection of the fusible conductor material, the design and arrangement of the solder points, the selection of the securing sand and possibly the solidification of the sand, and by partially high-strength ceramics as a fuse body, optimized. In addition, usually the arrangement of the bottleneck rows on the fusible conductor with regard to an optimal turn-off behavior the fuse optimized. In particular, the current-carrying capacity of the fuse is determined essentially by the design of these bottleneck rows.

Fuses are used, for example, for line protection, semiconductor protection, battery protection or even in a photovoltaic system to protect the respective line network. Such fuses have a defined tripping characteristic and respond according to their respective operating characteristic. However, the tripping behavior of such a fuse is also influenced by external influencing variables - for example the ambient temperature, the installation conditions or the possibility for cooling or heating. Due to their design, it is not possible to set the triggering sensitivity of such a fuse to the currently prevailing environmental conditions or selectively switch off the fuse, for example, to disconnect a photovoltaic system directly from the mains. The fuses used must therefore - in order to be able to defy all possible environmental influences (temperature, installation situation, starting currents) - designed to be significantly oversized in order to reliably prevent false triggering. However, there is a risk of too late shutdown, e.g. at low temperatures.

From the state of the art adjustable fuses are known, the tripping characteristic is fixed once fixed during installation to adjust the fuse to a particular application. However, adaptation to changing environmental influences is not possible with such adjustable fuses.

In addition, there are already considerations for so-called triggerable or triggered fuses ("triggered fuses"), which are triggered in addition to their intrinsic tripping characteristic in addition by an external control in order to enable an interruption of the protected circuit in the event of an emergency situation. The triggered triggering can be carried out, for example, by a mechanical severing of the fusible conductor, a severing by pyroelectric charging or by an additional heating resistor. The term "emergency" is to be understood as a predefined operating state, which is still below the tripping characteristic of the fuse, which is why the fuse would not trigger by itself, but in which the fuse protected by the fuse electrical circuit should be interrupted by a To avoid or eliminate dangerous situations. Typical applications are the interruption of the battery circuit in electrically powered vehicles - for example, in the case of an accident - or the separation of photovoltaic systems from the supply network - for example in case of fire.

It is the object of the present invention to provide a fusible conductor and an overcurrent protection device, which are more flexible adaptable to their respective application and the prevailing environmental conditions there.

This object is achieved by the fusible conductor according to the invention and the inventive overcurrent protection device according to the independent claims. Advantageous embodiments are the subject of the dependent claims.

The fuse element according to the invention for an overcurrent protection device has an elongate base body extending in a longitudinal direction, the first end of which has a first contact area for contacting with a first contact element of the overcurrent protection device, and the second end has a second contact area for contacting with a second contact area Contact element of the overcurrent protective device has. There are several between the first contact region and the second contact region Narrow row arranged, each having a plurality of holes, which in turn are arranged transversely to the longitudinal direction of the fusible conductor. In a middle region of the fusible conductor, which is arranged centrally between the first contact region and the second contact region, two of the bottleneck rows are at a smaller distance from one another than the other bottleneck rows. Furthermore, the fusible conductor in this central region has at least one additional connection conductor, which is electrically conductively connected to the fusible conductor.

According to the invention, the two bottleneck rows arranged in the middle region of the fusible conductor have a smaller distance from each other than the remaining bottleneck rows arranged between the middle region and the contact regions, which usually have an equidistant spacing from one another. The middle region is arranged substantially centrally between the first contact region and the second contact region of the fusible conductor. With the help of the additional connecting conductor, the two arranged in the central region, narrower spaced bottleneck rows of the fusible conductor by means of a predefined control current flowing between this additional terminal and the first or second contact, targeted thermally biased. As a result, the tripping characteristic of the fusible conductor is displaced in such a way that an earlier tripping of the fusible conductor and thus of the overcurrent protection device can thereby be realized. The tripping characteristic of the overcurrent protection device is thus selectively influenced in the direction of a more sensitive characteristic, whereby the fusible conductor, and thus the overcurrent protection device, more flexible to their respective application and the prevailing environmental influences - especially ambient temperature, installation situation and start-up currents - are adaptable.

In extreme cases, can also be a cut through the current in case of doubt, or only low over a short surge energized fusible conductor done. Here, the central arrangement of the two rows of bottlenecks with a smaller distance is particularly advantageous so that the resulting arc, which propagates in the further course in both directions of the fusible conductor to the ends - almost simultaneously reaches the first and the second end of the fuse conductor. In this way, false shutdowns of the fuse can be effectively avoided.

In an advantageous development of the fusible conductor, the distance between the two bottleneck rows arranged in the middle region is substantially smaller than the melt conductor width, but larger than the hole spacing of the bottleneck rows.

These geometrical relative size ratios have been found to be particularly advantageous in order to thermally pre-load the middle region of the fusible conductor in a predefined manner via an external circuit. Due to the design of the distance between the two inner bottleneck rows, the necessary height of the control current and the thus realizable displacement of the characteristic can be influenced. It is true on the one hand that with a smaller distance between the two inner rows of bottlenecks, an even smaller control current is required. On the other hand, the characteristic curve can be shifted further, the greater the distance of the two inner bottleneck rows is selected.

In a further advantageous development of the fusible conductor, the distance of the two bottleneck rows arranged in the central region is between 3 mm and 20 mm. This range has proved to be particularly advantageous for the configuration of the tripping characteristic with respect to the desired control current and the desired displacement of the characteristic.

In a further advantageous embodiment of the fuse element is strip-shaped. Under the term "Strip-shaped" is to be understood that on the one hand, the length of the fusible conductor is significantly greater than its width, and on the other hand, its width in turn significantly larger than its thickness. This geometry is particularly suitable for the formation of bottleneck rows and the application of solder points.

In a further advantageous development of the fusible conductor, the additional connection conductor is formed laterally on the fusible conductor.

The fusible conductor can be made by punching from a suitable strip material, wherein the cutting tool is moved in the direction of the thickness of the fusible conductor. In this case, the lateral molding of the additional connection conductor is particularly advantageous because no separate manufacturing step is required for punching the fusible conductor. The term "lateral" is meant to be transverse to the longitudinal direction, i. to look at the broad side of the fuse element strip viewed in the direction of the thickness extension to understand.

In a further advantageous development, the fusible conductor has a solder deposit in the region of the additional connecting conductor. With the help of this solder depot, the overload range of the fuse can be selectively influenced.

In a further advantageous development of the fusible conductor, the two bottleneck rows arranged in the middle region of the fusible conductor are arranged obliquely to one another.

The term "oblique" is to be understood to mean that the two bottleneck rows do not have the same distance from each other over their entire course, but that this distance is less at one end of the bottleneck row than at the other end. By means of this arrangement, a different Response behavior of the characteristic shift can be achieved.

In a further advantageous refinement of the fusible conductor, the latter has a further additional connecting conductor, which is electrically conductively connected to the fusible conductor such that the two bottleneck rows arranged in the middle region of the fusible conductor are arranged between the first additional connecting conductor and the further additional connecting conductor.

With the aid of the first additional connecting conductor and the additional additional connecting conductor, the middle region of the fusible conductor can be electrically conductively connected to an external control device in order to be able to specifically thermally pre-stress it with a defined control current if required by means of a suitable electrical circuit.

In a further advantageous development of the fusible conductor, the two additional connection conductors are arranged symmetrically.

This is to be understood as meaning both an axisymmetric arrangement with respect to the longitudinal extension direction of the fusible conductor, and a point-symmetrical one of the two additional connecting conductors with respect to a center point of the fusible conductor. Due to the point or axisymmetric arrangement, a favorable position of the connection points according to the voltage potentials and the mechanically favorable position of the additional contacts can be realized.

In a further advantageous development of the fusible conductor, the two additional connecting conductors are arranged offset in the longitudinal direction by at least one row of bottlenecks.

Due to the staggered arrangement a uniform preload of all bottlenecks with low tax performance can be realized. Furthermore, this arrangement is also suitable for an odd number of bottleneck rows. The two middle bottleneck rows can also have the same distance as the other bottleneck rows.

In a further advantageous development of the fusible conductor, the two connection conductors can be electrically conductively connected to a control device.

With the aid of the control device, the two bottleneck rows arranged in the central region can be specifically thermally pre-stressed, as a result of which the tripping characteristic of the overcurrent protection device can be changed in a defined manner. The controller may be part of the overcurrent protection device. However, it is also possible to use a higher-level control device, which is electrically conductively connected to a plurality of overcurrent protection devices and interacts with them in such a way that their tripping characteristic can be varied in an individually predefined manner. In particular, the tripping behavior of the fuse can be designed in a similar manner to an electronic trip unit (ETU) customary with circuit breakers. By a correspondingly high current pulse is also a direct, i. immediate triggering of the fuse can be realized.

The overcurrent protection device according to the invention has at least one fusible conductor of the type described above.

With regard to the general advantages of the overcurrent protection device according to the invention, reference is made to the abovementioned advantages of the inventive fusible conductor. For fuses with several electrically connected in parallel Fusible conductors may be formed all, some or only a single one of the plurality of fusible conductors in the manner of the fusible conductor according to the invention. In order to achieve shutdown at an operating current below rated current, it is sufficient to design only one of them according to the invention in the case of a fuse with, for example, two fuse conductors. If this is severed, then the remaining, not according to the invention formed fusible conductor carries twice the current, which is why this fusible element shortly thereafter melts and thus finally triggers the fuse.

In an advantageous development, the overcurrent protection device further comprises a control device with which the at least one additional connection conductor is electrically conductively connected in order to influence the tripping characteristic of the overcurrent protection device by means of the control device in a targeted manner.

With the aid of the control device, the two bottleneck rows arranged in the central region can be specifically thermally pre-stressed, as a result of which the tripping characteristic of the overcurrent protection device can be changed in a defined manner. Furthermore, by a correspondingly high current pulse also a direct, i. immediate triggering of the fuse can be realized.

Figur 1

eine schematische Darstellung zum prinzipiellen Aufbau einer Schmelzsicherung;

Figuren 2A bis 2D

schematische Darstellungen verschiedener Ausführungsformen des erfindungsgemäßen Schmelzleiters;

Figur 3

eine schematische Darstellung verschiedener Auslösekennlinien des erfindungsgemäßen Schmelzleiters bzw. der erfindungsgemäßen Schmelzsicherung.

Exemplary embodiments of the inventive fusible conductor will be explained in more detail below with reference to the attached figures. In the figures are:

FIG. 1

a schematic representation of the basic structure of a fuse;

FIGS. 2A to 2D

schematic representations of various embodiments of the fuse element according to the invention;

FIG. 3

a schematic representation of various tripping characteristics of the fuse element according to the invention or the fuse according to the invention.

In the various figures of the drawing, like parts are always provided with the same reference numerals. The description applies to all drawing figures in which the corresponding part can also be recognized.

FIG. 1 schematically shows the basic structure of a fuse 1. This has a first contact element 4 and a second contact element 5, which consist of an electrically conductive material, such as copper. The contact elements 4 and 5 are mechanically fixed and tightly connected to a fuse body 2, which consists of a solid, non-conductive and highly heat-resistant material, such as a ceramic. The securing body 2 generally has a tubular basic shape and is pressure-tight to the outside, for example by means of two sealing caps 3, closed. The contact elements 4 and 5 each extend through an opening formed in the closure caps 3 in an interior of the fuse body 2. In this interior, a so-called fuse element 10 is arranged, which electrically conductively connects the first contact element 4 and the second contact element 5. For this purpose, a first end 14 of the fusible conductor 10 is electrically conductively connected to the first contact element 4, and a second end 15 is electrically conductively connected to the second contact element 5. The remaining interior of the fuse link 1 is completely filled in the present case with an extinguishing agent 6, which serves to extinguish and cool the fuse 1 in the event of triggering and the fusible conductor 10 completely surrounds. As extinguishing agent 6, for example, quartz sand is used. Instead of in FIG. 1 a fusible conductor 10 shown, it is also possible to arrange a plurality of fusible conductor 10 electrically connected in parallel to each other in the fuse body 2 and to contact with the two contact elements 4 and 5 accordingly.

The fusible conductor 10 is generally made of a highly conductive material such as copper or silver and has its length, i. in its longitudinal direction L, several bottleneck rows 11 and one or more solder deposits 13 - so-called solder points - on. About the bottleneck rows 11 and the solder points 13, the tripping characteristic of the fusible conductor 10 - and thus the fuse 1 - be adapted to the particular application. For currents that are smaller than the rated current of the fuse 1, only so much power dissipation is implemented in the fusible conductor 10 that it can be discharged in the form of heat quickly over the sand, the fuse body 2 and the contacts 4 and 5 to the outside. The temperature of the fusible conductor 10 does not rise above its melting point. If a current flows in the overload range of the fuse 1, the temperature of the fuse 1 continues to rise steadily until the melting point of the fuse conductor 3 is exceeded and this melts through at one of the bottleneck rows 11. At high fault currents - as they occur, for example, due to a short circuit - so much energy is converted in the fusible conductor 10, that this is heated practically over the entire length and as a result melts at all bottleneck rows 11 at the same time.

Since liquid copper or silver still has good electrically conductive properties, the current flow is not interrupted at this time. The melt formed from the fusible conductor 10 is thus further heated until it finally turns into the gaseous state and forms a plasma. This creates an arc around the current flow continue to maintain over the plasma. In the last stage of a safety shutdown, the conductive gases react with the extinguishing agent 6, which in conventional fuses 1 mostly consists of quartz sand. This is melted due to the arc caused by the extremely high temperatures around the arc, resulting in a physical reaction of the molten melt conductor material with the surrounding quartz sand 6. Since the resulting reaction product is electrically non-conductive, the current flow between the first contact element 4 and the second contact element 5 of the fuse 1 drops rapidly to zero. It should be noted, however, that a certain mass of fusible conductor material also requires a corresponding mass of extinguishing agent. This is the only way to ensure that sufficient extinguishing agent 6 is present at the end of the safety shutdown in order to effectively bind the entire conductive plasma.

In the FIGS. 2A to 2D different embodiments of the fuse element 10 according to the invention are shown schematically. In its longitudinal direction L, the fusible conductor 10 according to the invention has a plurality of bottleneck rows 11, which extend transversely to the longitudinal direction L of the fusible conductor 10. In the in the FIGS. 2A to 2C In the cases shown, the bottleneck rows 11 are oriented at right angles to the longitudinal direction L of the fusible conductor 10. However, this is not mandatory, as in FIG. 2D illustrated embodiment shows. About the first end 14 and the second end 15 of the fuse element 10 with the first contact element 4 and the second contact element 5 of the fuse 1 (see Fig.1 ) are electrically connected.

The bottleneck rows 11 are formed from a plurality in a series of holes 16 arranged one behind the other and are usually arranged at an equidistant distance a ₂ spaced from each other. Only in a middle area 12, which is arranged centrally between the first end 14 and the second end 15, the two bottleneck rows 11-1 and 11-2 arranged there have a smaller distance a _{1 from} one another. This distance a ₁ is selected so that it is substantially smaller than the width of the fusible conductor 10 measured in a width direction B, but larger than the space between the individual holes 16 of a bottleneck row 11.

In the middle region 12, at least one additional connection conductor 17 is integrally formed on the fusible conductor 10. The Figures 2A and 2D show in this case embodiments with only one additional connection conductor 17. In the FIGS. 2B and 2C Embodiments with two connection conductors, the first additional connection conductor 17 and the additional additional connection conductor 18 are shown. The additional connection conductors 17 and 18 are thus - depending on the embodiment - connected to one side or both sides of the fuse element 10. Advantageously, the additional connection conductors 17 and 18 are formed from the fusible conductor material and have a similar cross-section as the fusible conductor 10. This cross-section of the additional connection conductors 17 and 18 may only be chosen so large that at a shutdown of the fuse 1, ie when a melting of the fusible conductor 10, the additional connection conductor 17 and possibly the additional additional connection conductor 18 are also separated. With the help of an external circuit, the central region 12 - ie the area between the arranged at a distance ₁ , narrower spaced bottleneck rows 11 - are acted upon by the additional connection conductors 17 and 18 with an electrical control current, whereby the central region 12 specifically thermally biased can be.

In FIG. 2D On the other hand, the two bottleneck rows 11-1 and 11-2 arranged in the central region 12 are arranged obliquely to one another, ie their spacing is in the width direction B is not constant, but continuously increases or decreases. With the distance a ₁ then the smallest distance between the two bottleneck rows 11-1 and 11-2 is designated, in Figure 2D at the respective left end of the bottleneck rows 11-1 and 11-2. With the help of this oblique arrangement, a different response of the characteristic shift can be realized.

A rough control can also be done without external power source: this is for example the in FIG. 2A used fusible conductor 10 and electrically connected such that the realized via the additional terminal conductor 17 control terminal with the main contacts of the fuse 1 - the first contact element 4 and the second contact element 5 - is electrically connected. Since a voltage drop occurs due to the outer bottleneck rows 11 of the fuse 1 under current, this leads to a corresponding control current with a corresponding shift in the tripping characteristic of the fusible conductor 10 or the fuse 1 (see also FIG FIG. 3 ).

It is also possible, by measuring and monitoring the electrical resistance of the central region 12 of the fusible conductor 10 early to detect an aging of the fuse 1. For this purpose, the central region 12 would have to carry only the solder points 13 of the fuse 1 or at least be soldered. A monitoring of the aging state of the fuse 1 would then be possible even during operation. Furthermore, on the basis of a continuous resistance measurement of the central region 12 due to the change in the electrical resistance with temperature change of the fusible material and the operating state of the fuse 1 can be deduced.

In FIG. 3 are various tripping characteristics of the fuse element 10 of the invention or the fuse according to the invention 1 shown schematically. It is the Time t, which is required to melt the fusible conductor 10, applied over the short-circuit current I. The characteristic shown on the right, designated K ₁ , describes, by way of example, the tripping characteristic of a 100 A photovoltaic fuse, as used to protect photovoltaic systems. The curve K _{2 shown} on the left, however, describes the tripping characteristic of a 100A fuse 1 according to the invention with thermal preload of the fuse element 10 according to the invention: the tripping characteristic K ₂ is shifted to the left and - in particular in the upper region - approximates the tripping characteristic of a conventional 63A fuse.

Furthermore, in the diagram of FIG. 3 entered two vertical lines, which mark the electrical currents I ₁ and I ₂ . If there is a short-circuit current I ₁ , a protection by means of a conventional 100 A fuse would lead to no or at most a very protracted triggering. Due to the thermal preloading of the fuse element 10 according to the invention, the original tripping characteristic K _{1 is} now shifted to the characteristic K ₂ : This allows a tripping time t _{12 to} be realized, which is significantly below the original tripping time.

The resulting possible use of the fuse 1 according to the invention is exemplified by the example of a photovoltaic system: would in such a system, which has three strands of 100A, which are each secured with a 100A fuse corresponding to the characteristic K ₁ , a short circuit occur in one of the three strands, the two intact strands would generate 200A to 220A short circuit current under full sunlight. However, if the sun is at an angle during the morning or evening hours or if the weather is cloudy, only a partial flow, eg of 110A, would occur. The photovoltaic system would in this operating state no power to the inverter deliver because the entire system is short-circuited. With the aid of a sunlight-and temperature-dependent control, however, the fusible conductor could be thermally biased according to the characteristic K ₂ , so that a triggering within a reasonable period of time t ₁₂ would be achievable as a result. The photovoltaic system would then continue to run properly with the two remaining strands.

The dependence on solar radiation is explained below with the aid of line I ₂ : if, with 100A fuses in a photovoltaic system, only a short-circuit current I ₂ of, for example, 130A is achieved due to low solar radiation, the trigger would be triggered Fuse and thus a shutdown of the photovoltaic system the period t ₂₁ pass. In reality, this can take well over an hour without electricity getting to the inverter. By means of a suitable irradiation-dependent precontrol by means of thermal preloading of the fusible conductor according to the invention, this value can be reduced to an acceptable time t ₂₂ of only a few minutes. The fuse can thus be dimensioned larger, since it can be adjusted depending on the prevailing environmental parameters to the current operating situation. The fuse therefore does not have to be operated to its power limit, which allows a much more robust operation.

Furthermore, in cold weather, the effect is that the real tripping characteristic of the fuse is shifted to the right due to the low temperatures. In real operation of a photovoltaic system, therefore, with very cold fuses, trigger values can be up to 20% higher than at normal temperatures. Because the characteristics respond to ambient temperature fluctuations, fuses with higher rated currents must be used for high daytime temperatures. If, for example, a 63A fuse is required, its characteristic would become weaker at high ambient temperatures shift left and would be too sensitive. This may require a 100A fuse. Due to the low overcurrents and short-circuit currents in photovoltaic systems would - especially at very cold ambient temperatures, which lead to a shift of the characteristic to the right - the fuse in case of failure or not very late trigger. This can be avoided by the characteristic K _{1 of} the fuse by means of suitable feedforward control again to the left on the characteristic K ₂ , which corresponds to a fuse with 63A characteristic is adjusted.

Finally, it is pointed out that the applications of the inventive fusible conductor 10 and the fuse 1 according to the invention are not limited to the field of photovoltaic systems. The field of photovoltaic systems has been selected only as an example to illustrate the advantages of the inventive fuse element 10 and the fuse 1 according to the invention.

LIST OF REFERENCE NUMBERS

1

Overcurrent protective device / fuse

2

fuse body

3

cap

4

first contact element

5

second contact element

6

extinguishing Media

10

fuse element

11

Engstellenreihe

• 11-1 bottleneck series
• 11-2 bottleneck series

12

middle area

13

solder deposit

14

first end

15

second end

16

holes

17

additional connection conductor

18

additional additional connection conductor

a ₁

distance

a ₂

distance

L

Longitudinal extension

B

Width direction of extension

t _i

time

I _i

Short circuit current

K _i

curve

Claims (13)

Fusible conductor (10) for an overcurrent protection device (1), - which has an elongate main body extending in a longitudinal direction (L), the first end (14) of which has a first contact area for contacting a first contact element (4) of the overcurrent protection device (1), and the second end (15) thereof a second contact region for contacting with a second contact element (5) of the overcurrent protection device (1), in which a plurality of bottleneck rows (11) are arranged between the first contact area and the second contact area, each having a plurality of holes (16) arranged transversely to the longitudinal extension direction (L) of the fusible conductor (10), characterized, in that, in a middle region (12) of the fusible conductor (10) arranged centrally between the first contact region and the second contact region, two of the bottleneck rows (11-1, 11-2) are at a smaller distance from one another than the remaining bottleneck rows (11), - That the fusible conductor (10) in this central region (12) has at least one additional connection conductor (17, 18), which is electrically conductively connected to the fusible conductor (10). Melt conductor (10) according to claim 1,
characterized,
that the distance (a ₁ ) of the two rows of bottoms (11-1, 11-2) arranged in the middle region (12) is substantially smaller than the melt conductor width, but larger than the hole spacing of the bottleneck rows (11-1, 11-2). Melt conductor according to claim 2,
characterized,
that the distance between the two is arranged in the central region Engstellenreihen (11-1, 11-2) is between 3 and 20 mm. Melt conductor (10) according to one of the preceding claims,
characterized,
that the fusible conductor (10) is strip-shaped. Melt conductor (10) according to one of the preceding claims,
characterized,
that the additional connection conductor (17) is formed laterally on the fusible conductor. Melt conductor (10) according to one of the preceding claims,
characterized,
that the fusible conductor in the region of the additional connecting conductor (17) comprises a solder deposit. Melt conductor (10) according to one of the preceding claims,
characterized,
that the two rows of bottoms (11-1, 11-2) arranged in the middle region (12) of the fusible conductor (10) are arranged at an angle to one another. Melt conductor (10) according to one of the preceding claims,
characterized,
in that the fusible conductor (10) has a further additional connection conductor (18) which is connected in an electrically conductive manner to the fusible conductor (10) such that the two bottleneck rows (11-1, 11) arranged in the middle region (12) of the fusible conductor (10) -2) between the first additional connection conductor (17) and the further additional connection conductor (18) are arranged. Melt conductor (10) according to claim 8,
characterized,
that the two additional connecting conductors (17, 18) of the fusible conductor (10) are symmetrically arranged. Melt conductor (10) according to claim 8,
characterized,
in that the two additional connecting conductors (17, 18) are offset in the longitudinal direction (L) by at least one row of bottlenecks. Melt conductor according to one of claims 8 to 10,
characterized,
that the two connecting conductors (17, 18) are electrically conductively connected to a control device. Overcurrent protection device (1),
which has at least one fusible conductor (10) according to one of the preceding claims 1 to 11. Overcurrent protection device (1) according to claim 12,
characterized,
in that the overcurrent protection device (1) furthermore has a control device with which the at least one additional connection conductor (17, 18) is electrically conductively connected in order to specifically influence a tripping characteristic of the overcurrent protection device (1).

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