EP3852125B1 - Triggerable fuse for low voltage applications - Google Patents

Description

The invention relates to a triggerable fuse for low-voltage applications for protecting devices that can be connected to a supply network, in particular overvoltage protection devices, consisting of at least one fuse conductor located between two contacts and arranged in a housing and with a trigger device for the controlled disconnection of the fuse conductor in the event of malfunctions or overload conditions connected device, with an extinguishing agent being introduced into the housing.

Conventional fuses are used in large quantities and in many applications to ensure overcurrent or short-circuit protection for cables and lines but also for connected equipment.

In addition, fuses are used as backup protection for surge arresters in the so-called shunt branch. An appropriate fuse must ensure protection in the event of a short circuit.

Due to the increasing use and integration of renewable energy sources in supply sets, increasingly volatile short-circuit values occur at the installation locations of the equipment, depending on the feed-in situation. This can have the consequence that the required melting or switching off integrals of the fuses have to be varied over a wide range. Under certain circumstances, the selected fuse can no longer ensure protection under all conceivable feed-in conditions. In principle, the use of circuit breakers with tripping characteristics is an alternative, but these switches are significantly more expensive than fuses and are therefore not suitable for all applications for cost reasons.

The special properties of a fuse generally only allow very limited design options in terms of varying or adjusting the protection area of the fuse.

In order to be able to adapt and expand the range of uses of fuses, it has already been proposed to cut the current conductor of an electrical fuse element using a pyrotechnically operated cutting device. The DE 42 11 079 A1 shows such a solution in which a pyrotechnic charge is ignited when the current flowing through the current conductor of the fuse and detected by a current detection device has a strength that is greater than a predeterminable threshold value.

The DE 10 2008 047 256 A1 discloses a high-voltage fuse with a controllable drive for a shear rod, which destroys several bottlenecks. The control can be carried out depending on the residual current from a separate controller.

The DE 10 2014 215 279 A1 discloses a fuse for a device to be protected, which is connected in series with the fuse.

Refers to the dimensioning of fuses DE 10 2014 215 279 A1 to the melting integral I ² t. Accordingly, the melting of a fusible conductor is determined by its material and geometric properties, so that depending on the material and/or geometry of the fusible conductor, a respective amount of heat Q is necessary to evaporate the fusible conductor.

Special requirements apply in the case in which the device to be protected by the fuse is a surge protection device, because this is intended to allow high currents to pass for a short time without the fuse tripping, but at the same time also with low-permanent spring currents, such as those caused by damage of the overvoltage protection device or as a mains follow current, switch it off early. The first of the requirements mentioned often leads to high rated current values of the fuse. The second of the requirements mentioned can only be meaningfully implemented with low nominal current values.

Taking this problem into account, the DE 10 2014 215 279 A1 on a further development of a fuse in such a way that additional contacts are provided, one of the additional contacts representing a trigger contact in order to activate the fuse element directly or indirectly by initiating a Short circuit to cause melting. In addition, the fusible conductor can have a predetermined breaking point in the area of one of the further contacts. In one embodiment, the fusible conductor is surrounded at least in sections with an extinguishing medium, in particular with sand.

The DE 10 2015 112 141 A1 shows a circuit breaker with a connecting element which is axially tensile-loaded via two springs and can be cut or torn. The additional axial tensile load ensures a rapid increase in the separation distance after the connecting element has been separated by a separating device.

From the DE 10 2015 114 279 A1 a circuit breaker is known which comprises two sections of connecting elements connected electrically in series, which are separated either by a mechanical movement of a release element or electrically when the circuit breaker is triggered.

Regarding the state of the art, please refer to CH 410137 A , the US 2,400,408 A and the WO 2014/158328 A1 referred.

From the above, it is the object of the invention to provide a further developed triggerable fuse for low-voltage applications for the protection of devices that can be connected to a supply network, in particular surge protection devices, the fuse being in addition to the melting integral value based on the fuse rating when required and depending on expected currents, in particular Short-circuit currents can be triggered specifically. In this case, a known destruction of the fusible conductor due to the action of mechanical forces should be used.

The triggering, i.e. the control to disconnect the fusible conductor in the event of a malfunction, should either be carried out by a higher-level control unit and, in the event that the fuse is integrated as backup protection in surge protection devices, by the surge protection device. The triggerable fuse should also be able to trip based on measured network impedance values.

The structure of the fuse to be created should be inexpensive, the fuse should have a high switching capacity and a small design. By specifying values for the formation of additional bottlenecks, the possibility of a specifically adjustable safety-protection characteristic curve can be realized.

The object of the invention is solved by a triggerable fuse according to claim 1, the subclaims comprising at least expedient refinements and further developments.

To solve the problem, a triggerable fuse is used, which is particularly suitable for low-voltage applications to protect devices that can be connected to a supply network, in particular surge protection devices. The fuse consists of at least one fuse conductor located between two contacts and arranged in a housing. Furthermore, a trigger device is provided for the controlled separation of the fusible conductor in the event of malfunctions or overload conditions of the connected device, with an extinguishing agent being introduced into the housing.

The fuse according to the invention has at least one fusible conductor with several narrow points in series, which ensures the passive function of a conventional electrical NH fuse. In addition, the fuse has at least one additional, special bottleneck per fuse conductor, which does not affect the passive function of the fuse and which can be activated by triggering regardless of the current load. This special bottleneck is destroyed by mechanical tearing, cutting, punching or punching out or cutting a solder connection.

According to an inventive idea, an area free of extinguishing agent is formed in the housing such that the at least one fusible conductor is exposed in at least one section.

A mechanical separating element can be introduced into the extinguishing agent-free area via an access in the housing in order to mechanically destroy the at least one fusible conductor independently of its fusible integral, depending on the trigger device.

In one embodiment of the invention, the separating element is designed as a blade or cutting edge.

The separating element itself can be driven in the direction of the fusible conductor by a bridge igniter.

The mechanical energy for moving the separating element can also be provided by a shape memory alloy or other media that change shape or volume.

The trigger device has a detection and evaluation unit as well as a control for the exemplary bridge igniter and a power supply and has at least one control input.

The passive characteristic of the fuse element of the fuse can be interrupted at any time, approx. > 10 ms, by the detection and evaluation device. Only the area of adiabatic melting remains unaffected. The associated I ² t value is coordinated with the consumer to be protected via the fuse conductor dimensioning in a known manner.

The solution according to the invention also enables the interruption of very small currents far below the passive nominal current strength of the fusible conductor and also a current-free interruption. This means that an interruption can occur independently of the current flow, for example when there is a measured change in impedance.

Due to the continuous measurement and when designed as a learning system, the evaluation and recording unit can take changes in the network into account when determining the current protection characteristic. This is advantageous when there is a changing number of consumers or a changing network output from energy producers.

Well-known basic functions for triggering such as current, voltage, their increases or their time-dependent behavior, but also external control signals can be used in addition to the impedance evaluation to control the trigger function. When protecting surge protection devices, voltage time areas can also be used in combination with a Electricity evaluation and temporal developments in performance or energy turnover can also be used as trigger criteria.

Criteria such as pressure, temperature, light, magnetic fields, electric fields or similar can be fed in and taken into account via additional sensors at additional inputs.

As explained, the triggerable fuse according to the invention is particularly suitable as an arrester back-up fuse for series connection with surge arresters in low-voltage applications.

The fuse according to the invention is designed in particular for use with spark gaps and can be designed according to these special features. In principle, the proposed principle is suitable for both DC and AC voltage applications and also allows use, for example, in the series branch.

Due to its small design, the controllable fuse can be used in a common housing of a surge protection device in series with a spark gap or a varistor.

The fuse protects the surge protection device before, during or even after an overload and isolates it from the network.

According to a further basic idea of the invention, a triggerable fuse is proposed, which aims at a defined mechanical cutting of a special, additional constriction of a fuse fuse element after activation of a trigger.

According to the invention, the additional bottleneck is structurally coordinated with existing passive current bottlenecks, that is, classic safety bottlenecks. Quartz sand, for example, is suitable as an extinguishing medium, particularly for high switching powers.

The variant described below solves the problem of creating a fuse that combines the advantages of a classic current-limiting fuse with those of an activatable, quasi-intelligent fuse with only one cutting blade, a small size and a simple activator. When functioning passively, the fuse does not increase the protection level of the downstream arrester and, when activated, does not generate any voltage above the designated protection level of the respective connected surge protection device.

The solution in this regard is based on one or more parallel fuse fuse conductors, which are arranged within an extinguishing medium.

The fuse conductors have several conventional electrical, i.e. current bottlenecks in series, the number of which corresponds to the usual design for the corresponding nominal voltage of the fuse.

According to known NH fuses, the fusible conductors extend primarily in a straight line axially through the fuse body. The structure and functionality of such a fuse and the bottlenecks correspond to those of conventional fuses with high short-circuit currents or virtual melting times of approx. < 10 ms.

The at least one fusible conductor preferably has at least one further special mechanical constriction between the usual current constrictions mentioned, which can be severed by at least one actuator and a cutting blade or a similar means.

The cutting blade as a separating element is preferably made of an insulating material or provided with an insulating coating. This insulating cutting blade leads to an extension of the isolating distance between the interrupted fusible conductor. The resulting isolating distance is capable of achieving a dielectric strength of at least 2.5 kV, preferably 4-6 kV.

The additional bottleneck according to the invention according to further embodiments of the invention differs from known, usual bottlenecks by the measures described below.

The geometric or mechanical additional bottleneck has a residual cross-section that is higher than that of the usual bottlenecks. The melting integral value (I ² t value) of the bottleneck is dimensioned so that it is equal to or minimally higher than the switch-off integral of the fuse. This design means that the bottleneck does not respond to short-circuit currents.

However, the area of the additional bottleneck is available to extend the arcs.

The geometric constriction and the cutting blade are located in an area without extinguishing medium.

This area is preferably separated from the areas with extinguishing medium and the electrical bottlenecks with thin webs on both sides.

The width of this area is essentially limited to the blade width and twice the fusible conductor thickness.

The fusible conductor or conductors are guided through the insulation web in such a way that preferably no further sealing to the separation area is necessary in order to prevent the penetration of an extinguishing medium, for example quartz sand.

The insulating bars can be made of ceramic, vulcanized fiber or polymers with or without gas release (POM). The wall thickness is preferably <1 mm.

The width of the cutting blade is preferably higher than the fusible conductor width, but at least wider than the additional mechanical constriction.

The blade has a stroke that goes beyond the expansion range of the fusible conductor when cutting. The distance of the shortest connection between a fuse conductor cut without current is ≥ 4 mm. In the event of an arc switch-off, the distance is extended due to the fusible conductor erosion. Measures to extend the sliding distance can be provided on the blade. The blade can form an insulating gap with a fixed or deformable counterpart.

When the shutdown is active, the arc can extend quite quickly from the cutting area into the area with extinguishing agent. The pressure development and thus the housing load in the cutting area is therefore low. With passive function, the high extinguishing capacity is guaranteed by the narrow areas in the two areas with extinguishing agent, for example compacted quartz sand.

The material of the additional constriction in the cutting area is available to extend the arc. Through the choice of material for the blade and the insulation webs or web walls, comparatively good cooling of the arc can also be achieved in this area.

Small sizes can be achieved thanks to the space-saving design and the low influence on the passive safety behavior. The fuse conductor routing and the impedance do not differ from conventional fuses, which means that the voltage drop in pulse currents can be limited. Due to the passive behavior of the additional bottleneck in the event of a short circuit, the voltage level of the fuse can be limited and it is possible to maintain the protection level of the arrester.

Due to the possibility of quickly extending the arc when cutting just one bottleneck in the area with compacted extinguishing agent or so-called "stone sand", the fuse can be activated even with high short-circuit currents, which ensures both passive and active functionality.

If only one bottleneck is separated, the above allows the fuse to be activated even at high currents with virtual melting times < 10 ms. This means that the fuse can be interrupted after a short time in a practically de-energized state, with small currents well below the rated current and even with high residual currents in the kA range. Likewise, almost any time/current characteristic curve can be implemented according to the respective requirements.

In an embodiment variant with several fusible conductors, it is possible to separate the fusible conductors simultaneously with greater effort or one after the other with less effort using a single actuator. The direction of movement can be straight or circular or eccentric. The blades can also be designed differently to suit this type of movement.

Alternatively, it is possible to separate the fusible conductors separately, each with a blade and an actuator. This also allows the blade to move in opposite directions or overlapping, whereby the blades can also serve to form gaps.

In order to implement a quick shutdown if necessary, a suitable actuator is implemented along with rapid error detection.

In order to avoid ignition devices or gas generators relevant to explosives, the invention proposes using a simple igniter, that is, a so-called bridge igniter, without its own explosive power. In order to still achieve a sufficient force effect, the pressure wave that arises during ignition is used in the manner of a piston/cylinder principle to separate the mechanical or geometric bottleneck of the fusible conductor or conductors.

For this purpose, for example, the blade shaft itself can be guided in the piston or connected to the piston or attached to a projectile guided in the piston.

The blade can therefore be arranged very close to the fusible conductor. However, a distance can also be selected to increase the impulse of the blade if there is sufficient space or the drive is located outside. The piston and also the blade can preferably be additionally guided. The mentioned projectile sits loosely in the butt. In the piston cavity there is an igniter or bridge igniter, which fills the piston cavity. The cavity is sealed from the projectile over a distance in the direction of movement, which corresponds at least to the movement path until the fusible conductor or conductors are severed. This ensures that the seal to the projectile in the piston is only removed after the bottleneck has been severed.

As is usual with passive fuses, the fuse fuse conductors are preferably rigidly attached to the fuse housing with a bottom cap and an end cap. The isolation of the cutting area from the extinguishing agent area on both sides serves as additional guidance for the fusible conductors in the narrow cutting area.

The guide in the bushings of the sealing plates is designed in such a way that the fusible conductor or conductors, when positioned transversely to the blade, are allowed to deform slightly in the direction of the blade movement when the blade hits it. It has been shown that this slight deformation requires less effort than a rigid fuse conductor guide. When separating the fusible conductors are bent on both sides between the insulation and the blade. Alternatively, punching is also possible with appropriate blade design and necessary force.

The force effect of the actuator is essentially based on the thermal expansion of the gas surrounding the bridge igniter. After opening the piston, this minimally heated amount of gas can easily relax within a very small volume, i.e. possibly directly in the cutting area, so that no reinforcement of the fuse housing, the caps or a vent or similar need to be provided.

If longer switch-off times are sufficient in the protection concept for the surge protection device used or the connected consumers, actuators with slower response times can also be used. For example, shape memory alloys or other volume-changing materials are conceivable here. The highest requirements for coordination between the force required to cut or separate a bottleneck are tied to the required pulse current carrying capacity, at which no separation of the fuse fuse element should be caused.

The loads on varistor-based arresters are lower than on lightning surge current arresters based on spark gaps. In general, a maximum load of 100 kA 10/350 µs is assumed for lightning rods. In standard alternating current networks, this means a load of 25 kA 10/350 µs for the individual spark gap. The fuse element of a fuse should meet the above requirement in the application described. This applies to both the usual electrical bottlenecks and the additional mechanical or geometric bottlenecks described.

For a standard NH fuse, this requirement corresponds approximately to a fuse with a rated current of 315 A. With regard to the rated voltage of the fuse, a voltage in the range of the line-to-line voltage of the network in which the arresters are used is often selected. This means that the fuse should be suitable for a voltage of 400 volts in a standard 230/400 volt network. When the arrester is switched off, the arrester back-up fuse does not generate an arc voltage that is above the protection level of the arrester. When designing the bottlenecks of NH fuses, one can be used for each bottleneck A voltage of approx. 300 volts can be expected. These requirements result in a minimum of three and a maximum of five known known bottlenecks for such a fuse, which means that a typical protection level of approx. 1.5 kV is generally not exceeded.

A further solution variant according to the invention is based on a controllable fuse, in particular for use as an arrester backup fuse, with this variant causing a defined tearing of a fuse fuse conductor using a special, additional bottleneck.

This approach is therefore aimed at a space-saving and cost-effective embodiment of a triggerable fuse, which is based on the defined tearing of a special additional bottleneck of a fuse fuse element in the extinguishing medium after activating a trigger. The remaining properties of an otherwise passive, fully functional backup are not affected. The special features of this solution approach lie in the simplicity of the trigger and the coordination of the additional, geometric bottlenecks with the classic, well-known safety bottlenecks.

When tensile forces are exerted on one or more fusible conductors, all existing bottlenecks, i.e. the entire fusible conductor band and the fastening of the band, are stretched. For fusible conductors with a length of 5-8 cm, the stretch length can easily be several millimeters until they break, especially for copper fusible conductors.

If a separation distance of approx. 3 mm is to be created, the necessary stroke distance can already be well over 10 mm, which leads to an undesirable increase in the size of such a component.

In order to limit the expansion, it is possible to partially fix the fusible conductor in relation to the housing or the extinguishing agent (sand). Alternatively, it is possible to partially solidify the extinguishing agent.

In contrast to the measures explained above, according to the teaching according to the invention, the expansion of the fusible conductor occurs predominantly at an additional mechanical, i.e. geometric, predetermined breaking point.

The entire extension is therefore only slightly above the necessary elongation at break of the predetermined breaking point and the desired separation distance.

The additional mechanical predetermined breaking point, also known as a tension point, must be coordinated and dimensioned in conjunction with the known electrical bottlenecks.

So that the mechanical bottleneck has a significantly lower tensile strength, the cross section of this is smaller than that of the electrically relevant bottlenecks. However, it must be ensured that despite the smaller cross-section with the same current load, the mechanical bottleneck does not respond before the electrical bottlenecks under all current loads, including transient loads, but rather with a time delay or at higher loads.

The relevant embodiment of the invention is therefore based on one or more parallel fuse fuses in an extinguishing medium. The fuse conductors have several conventional constrictions in series, the number of which corresponds to a usual design for the corresponding nominal voltage of the fuse.

According to conventional NH fuses, the fusible conductors extend primarily in a straight line axially through the fuse body. The fusible conductor or conductors preferably have at least one further, special narrow point between the known constrictions mentioned, which can be torn by an actuator.

The actuator used also requires a defined extension of the interrupted fusible conductor. The resulting total isolating distance achieves a dielectric strength of at least 2.5 kV.

The additional bottleneck differs from the usual bottlenecks in the following features.

The additional mechanical or geometric bottleneck has a residual cross-section that is significantly smaller than that of the usual bottlenecks. The melting integral value of the constriction is equal to or even greater than that of the usual known constrictions during the period of transient pulse current loads, in particular the current pulse form 8/20 µs and 10/350 µs.

In addition, the mechanical strength relative to the direction of force of the actuator is significantly smaller than the mechanical strength of the other known bottlenecks.

The force of the actuator therefore acts almost exclusively on the additional bottleneck according to the invention. The expansion of the usual, well-known bottlenecks as a result of the force exerted by the actuator is negligible.

The mechanical bottleneck is designed in comparison to the electrical bottlenecks in such a way that it generally does not respond to mains frequency loads. However, the area of the bottleneck is available for extending the arcs from the normal bottlenecks.

The dimensions of the mechanical bottleneck are therefore significantly smaller than the known bottlenecks. In band-shaped fusible conductors, the constriction is designed in such a way that uneven current distribution can be largely avoided, even with steep current increases. For this purpose, the bottleneck is ideally designed as a tapering of the band on both sides over the entire width with a length of < 500 µm, optimally < 100 µm. In such a design with usual punched outs or continuous recesses, these are realized in such a way that the recesses are similarly short and the width of the recesses does not exceed twice the length.

In principle, other design variants are also possible. The aim of the proposed measures is to ensure that the current density distribution in the fusible conductor and the constrictions is as uniform as possible, even under pulse current loads, with very good and almost distortion-free heat dissipation from the area of the geometric constriction.

The above ensures, even with rapid current pulse loads of up to <1 ms, a lower temperature increase within the mechanical constriction with a smaller cross-section than in the usual electrical constrictions with a higher cross-section.

• Fig. 1 ein Blockschaltbild einer Grundanordnung, bestehend aus Erfassungs- und Bewertungseinheit, Ansteuerung, Energieversorgung und triggerbarer Sicherung;
• Fig. 2 einen beispielhaften Aufbau einer triggerbaren Sicherung im Schnitt;
• Fig. 3 eine beispielhafte Zeit/Strom-Kennlinie einer erfindungsgemäßen triggerbaren Sicherung;
• Fig. 4 einen beispielhaften Schmelzleiter für eine Kapselsicherung mit Engstellen, welche zur Erzielung kurzer Schmelzzeiten bei kleinen Überströmen länger als bekannte, übliche Engstellen ausgestaltet sind;
• Fig. 5 eine Bauform mit nicht geradlinigem Schmelzleiter, sondern mit einer winkeligen Führung des Schmelzleiters mit den Anschlüssen A und B;
• Fig. 6 eine prinzipielle Anordnung mit zwei Schmelzleitern und gegenläufigen Klingen mit jeweils einem Aktor;
• Fig. 7 einen Teilbereich der Anordnung gemäß Fig. 2 nach einer Trennung ohne Lichtbogeneinwirkung;
• Fig. 8a eine Anordnung, bei welcher die Schmelzleiter gleichzeitig und quer geschnitten werden;
• Fig. 8b eine Darstellung des gleichzeitigen Schneidens der Schmelzleiter mit vertikaler Ausrichtung zum Schmelzleiter;
• Fig. 9 ein Schneidelement mit zwei versetzten Klingen im Querschnitt, welches das Schneiden von zwei Schmelzleitern quer mit kurzem Hubweg ermöglicht;
• Fig. 10 jeweils Klinge und Aktor zum Schneiden eines Schmelzleiters mit kurzen Hubwegen und gegenläufiger Bewegung der Klingen;
• Fig. 11 ein Schneidelement mit zwei Klingen und rotatorischer Bewegung, welche durch eine entsprechende Führung und nur einem Aktor erzwungen werden kann;
• Fig. 12 eine Ausführungsform, bei welcher ein weiterer Sicherungsschmelzleiter, welcher beispielsweise drahtförmig ausgeführt werden kann, durch die Trenneinrichtung nicht unterbrochen wird;
• Fig. 13 eine Alternative zu einem Draht mit einem Schmelzleiter auf einem Träger;
• Fig. 14 eine Schneidanordnung parallel zu einer Hörnerfunkenstrecke, welche mit einem Sicherungsdraht geringer Nennstromstärke kurzgeschlossen ist, und wobei beim Durchtrennen des Hauptschmelzleiters der Strom auf den Sicherungsdraht kommutiert, welcher die Hörnerfunkenstrecke zündet, die dann den Strom in einer Löschkammer löscht;
• Fig. 15 eine Weiterbildung einer Schneid- und Trennklinge;
• Fig. 16 eine Anordnung mit einem Aktor mit kurzem, jedoch variablen Hubweg;
• Fig. 17 einen Schmelzleiter mit bekannten Engstellen in Form von länglichen Ausnehmungen, wobei zwischen den bekannten Engstellen ein Bereich mit unvermindertem Querschnitt vorgesehen ist und innerhalb dieses Bereiches eine Zusatzengstelle in Form mehrerer rautenförmiger Ausnehmungen mit kurzer Gesamtlänge ausgeführt ist;
• Fig. 18 einen Schmelzleiter für eine Kapselsicherung mit Engstellen, welche zur Erzielung kurzer Schmelzzeiten bei kleinen Überströmen anders gestaltet sind als übliche, bekannte Engstellen;
• Fig. 19 eine Ausführungsform, bei welcher zwischen üblichen, bekannten Engstellen die erfindungsgemäße zusätzliche mechanische Engstelle 4 eingebracht ist;
• Fig. 20a-c verschiedene Gestaltungsvarianten der zusätzlichen, erfindungsgemäßen mechanischen Engstelle;
• Fig. 21a und b ein beispielhafter Aufbau einer NH-Sicherung in Kapselbauform (ausschnittsweise) mit A im Normalzustand und B ausgelöst;
• Fig. 22a und b eine Ausführungsform für eine Verwendung von Formgedächtnislegierungen mit spezieller Nutzung der Zugkraft;
• Fig. 23 eine Ausführungsform, bei der die Zugkraft an einer Lotstelle wirkt, welche beispielsweise durch eine Reaktionsfolie mit exothermer Reaktion innerhalb kürzester Zeit, das heißt im Millisekunden-Bereich, gelöst werden kann.

The invention will be explained in more detail below using exemplary embodiments and with the help of figures. Show here:

• Fig. 1 a block diagram of a basic arrangement, consisting of a detection and evaluation unit, control, energy supply and triggerable fuse;
• Fig. 2 an exemplary structure of a triggerable fuse in section;
• Fig. 3 an exemplary time/current characteristic of a triggerable fuse according to the invention;
• Fig. 4 an exemplary fusible conductor for a capsule fuse with constrictions, which are designed to be longer than known, usual constrictions in order to achieve short melting times with small overcurrents;
• Fig. 5 a design with a not rectilinear fusible conductor, but with an angled guide of the fusible conductor with connections A and B;
• Fig. 6 a basic arrangement with two fusible conductors and opposing blades, each with an actuator;
• Fig. 7 a portion of the arrangement Fig. 2 after a separation without arc exposure;
• Fig. 8a an arrangement in which the fusible conductors are cut simultaneously and transversely;
• Fig. 8b a representation of the simultaneous cutting of the fusible conductors with vertical orientation to the fusible conductor;
• Fig. 9 a cutting element with two offset blades in cross section, which enables the cutting of two fusible conductors transversely with a short stroke;
• Fig. 10 Each blade and actuator for cutting a fusible conductor with short strokes and opposite movement of the blades;
• Fig. 11 a cutting element with two blades and rotational movement, which can be enforced by an appropriate guide and only one actuator;
• Fig. 12 an embodiment in which a further fuse fuse conductor, which can be designed in the form of a wire, for example, is not interrupted by the separating device;
• Fig. 13 an alternative to a wire with a fusible conductor on a support;
• Fig. 14 a cutting arrangement parallel to a horn spark gap, which is short-circuited with a fuse wire of low nominal current, and wherein when the main fusible conductor is severed, the current commutates to the fuse wire, which ignites the horn spark gap, which then extinguishes the current in a quenching chamber;
• Fig. 15 a further development of a cutting and separating blade;
• Fig. 16 an arrangement with an actuator with a short but variable stroke path;
• Fig. 17 a fusible conductor with known constrictions in the form of elongated recesses, an area with an undiminished cross-section being provided between the known constrictions and an additional constriction in the form of several diamond-shaped recesses with a short overall length being designed within this area;
• Fig. 18 a fuse conductor for a capsule fuse with constrictions, which are designed differently than usual, known constrictions to achieve short melting times with small overcurrents;
• Fig. 19 an embodiment in which the additional mechanical bottleneck 4 according to the invention is introduced between usual, known bottlenecks;
• Fig. 20a-c different design variants of the additional mechanical bottleneck according to the invention;
• Fig. 21a and b an exemplary structure of an NH fuse in capsule design (partial) with A in the normal state and B triggered;
• Fig. 22a and b an embodiment for using shape memory alloys with special use of tensile force;
• Fig. 23 an embodiment in which the tensile force acts on a soldering point, which can be solved, for example, by a reaction film with an exothermic reaction within a very short time, that is to say in the millisecond range.

The Fig. 1 shows a basic arrangement of an embodiment according to the invention, which consists of a detection and evaluation unit 1, a control 2, a power supply 3 and the triggerable, controllable fuse 4.

The control unit 2 has an additional external control input 5.

The detection and evaluation unit 1 has several measuring inputs 8 and an input for current measurement 6 and for voltage measurement 7.

Additional sensors can be connected to inputs 8.

It is also possible to provide a communication input for external measuring devices.

The signal to the fuse 4 can be wired or wireless with a separate supply to the ignition device (bridge igniter).

The Fig. 2 shows an exemplary structure of a triggerable fuse with cutting element 13 in section.

In terms of the fuse, this representation corresponds to the classic structure of known NH fuses with an extinguishing agent in the form of quartz sand and an additional area for activating a bridge igniter 14.

The fuse 4 according to the invention has two connection caps 9, two fusible conductors 10, two areas 11 with an extinguishing agent, for example quartz sand, and an area 12 free of extinguishing agent. A cutting pawl 13 can be inserted into the extinguishing agent-free area 12 to separate the fusible conductors 10.

When the bridge igniter 14 is activated, the cutting blade 13 is accelerated in the direction of the fusible conductor 10 and cuts it.

A stop area can be provided in the area free of extinguishing agent in the path of movement of the cutting blade 13. This stop area serves to dampen the Impact and thus protection of the housing wall and the blade. In addition, this area can be used for gap-like arc constriction. The stop area can be realized, for example, by a soft or elastic or porous plastic with or without gas release. Alternatively, damping is also possible in a tapering, gap-like area made of insulation material.

The bridge igniter 14 is activated via control lines 15, which are connected to the control 2 (see Fig. 1 ) can be connected directly.

The bridge igniter 14 is located in a housing 16, the housing 16 having a piston 17 driven by the bridge igniter 14, which is connected to a separating element 13.

The extinguishing agent-free area 12 is designed as a channel that is sealed off from the extinguishing agent 11. The channel has side walls 18, which can also serve to guide the separating element 13.

The Fig. 3 shows an example of the time/current characteristic of an arrangement according to the invention.

For reasons of clarity, the characteristic curves are only shown in a simplified manner in the time range of approx. 4 ms to 10 s. In addition, the basic course in the time range up to approx. 4 ms was shown.

The adiabatic heating of the fuse conductors of the gG fuses can be up to > 5 ms depending on the fuse conductor design. The passive fusible conductor of fuse A, for example, has a nominal current of approx. 315 A. Fuse B has a significantly lower nominal current of 100 A, but with almost the same adiabatic melting integral (I ² t value).

Due to this value, the pulse current carrying capacity, which is important for use in combination with a surge protection device, for example, is comparable for both fuses. In order to achieve such a characteristic curve, the fusible conductor B must be designed accordingly or additionally aged.

In the adiabatic time range, the behavior of the proposed protective device is determined by the passive melting behavior of the fuse's fuse conductor.

With smaller currents and theoretically longer passive melting times of the respective fuse A or B, the time until the fuse conductor is actively interrupted can be limited as desired, for example from 10 ms to the passive melting time. The time/current characteristic curve can therefore be designed in any way below the passive time/current characteristic curve of the fuses. This means that it is also possible to set maximum current flow durations and maximum current flow levels within a wide range. The exemplary area with a variable characteristic is limited by the dashed lines below the passive characteristics of the fusible conductors A and B. This makes it possible to adapt well to various protection tasks.

The Fig. 4 shows a fusible conductor 1A for a capsule fuse with constrictions 2A, which are designed to be longer than known electrical constrictions in order to achieve short melting times with small overcurrents. This leads to an advantageous reduction in the rated current of the fuse. The length of the constrictions corresponds approximately to the distance of the immediate cross section of the fusible conductor 1A between the constrictions. Between the bottlenecks there is an additional bottleneck 3A for cutting the fusible conductor with a lower degree of modulation than the bottlenecks 2A.

In order to achieve optimal extinguishing properties with a simple quartz sand filling as an extinguishing agent, it is advantageous to divide the fusible conductor into several fusible conductors when the pulse currents have to be controlled and the associated high metal content is present. For the requirements relevant to the invention, two fusible conductors of the same design are advantageous.

In principle, the size, the geometry of the fuse housing, the number of fuse conductors, etc. can be varied as desired. In addition to a straight fuse conductor guide and connection on both sides to opposite end faces, the connections A and B can of course also be on one side of the housing 6A according to Fig. 5 lay.

In addition to housings made of insulating material, electrically conductive housings with one or two insulated entries for the fusible conductor or conductors can also be implemented.

The fusible conductor design can use strips, wires, tubes or the like.

The routing of the fusible conductors and the positioning of the connections must be designed in such a way that the forces, the current levels and, in particular, the protection level of the entire arrangement are maintained when exposed to transient pulses. The inductive voltage drop across the fuse arrangement must be limited to values < 300 V, if possible < 200 V for loads greater than 25 kA. To reduce the inductance, it is possible to design the fusible conductor guide in a bifilar manner.

Fig. 6 shows a basic arrangement of two fusible conductors 1A with two opposing blades 4A, each with an actuator (not shown for simplicity).

The housing also serves as connection A. The other connection B is led out of the housing 6A in isolation. The coaxial arrangement reduces the inductive voltage drop.

Fig. 7 represents a portion of the arrangement accordingly Fig. 2 after a separation without the effects of arcing.

In the Fig. 7 the sideways folding of the fusible conductor areas 12A between the blade 4A and the insulation plates can be seen. Due to the close guidance of these parts, the clamping of the parts can also be used to brake the blade 4A and to form gaps if they are designed accordingly.

The Fig. 8a shows an arrangement in which the fusible conductors are cut simultaneously and crosswise. The Fig. 8b shows a simultaneous cutting of the fusible conductor with a vertical orientation to the fusible conductor. According to Fig. 8a The actuator 5a and the cutting blade are integrated directly into the fuse housing to save space.

In Fig. 9 A cutting element with two offset blades 4A is shown in cross section, which enables the cutting of two fusible conductors 1A with a short stroke.

According to Fig. 10 a blade 4A or an actuator 5A is used to cut a fusible conductor 1A. This enables short stroke paths, a counter-rotating movement of the blades and, if designed appropriately, a partial gap formation directly between the blades 4A if no additional insulation section with or without an extinguishing function or an area with extinguishing agent is provided.

In Fig. 11 a cutting element with two blades 4A and rotary movement is shown, which can be enforced by an appropriate guide and with only one actuator. The blade 4A can be guided in one part in such a way that a good gap formation is possible.

The Fig. 12 shows an embodiment in which a further fuse fuse conductor 13A, which can also be designed in wire form, for example, is not interrupted by the separating device.

The wire can be contacted at the main connections or directly or indirectly at the main fusible conductors.

The wire is preferably surrounded by an erasing medium 14A. If the main fusible element is interrupted, the current commutates to the wire, which means that arcing in the cutting area can be largely avoided and a high dielectric strength can be achieved after complete separation.

The interruption occurs through another fusible conductor, which has a very low nominal current strength, in particular below the nominal current strength of the network.

The wire-shaped fusible conductor 13A, for example, can be interrupted directly or indirectly with a time delay, if necessary with the same cutting edge, in order to enable current to pass through at 0 A. Indirect interruption is possible in the event of a mechanical displacement or destruction of a carrier on or by the wire. As an alternative to a wire, it is possible to use a fusible conductor on a carrier 15A accordingly Fig. 13 to carry out. It is also possible to move an SMD fuse.

The basic arrangement explained is suitable, with further modifications, for interrupting high short-circuit currents.

The cutting or separating arrangement according to the invention can be located in parallel with a horn spark gap 16A, which is short-circuited, for example, with a fuse wire 17A of low current rating. When the main fusible conductor is severed, the current commutates on the fuse wire 17A, which ignites the horn spark gap 16A, which in turn extinguishes the current in a quenching chamber 18A in a current-limiting manner.

Such an arrangement is in the Fig. 14 shown as an example.

The requirements regarding current commutation and the risk of reignition are lower here than with a parallel connection to a fuse with a small nominal current. It is also possible to ignite an arc directly below the inlet area or directly in an arc chamber. In this case, the requirements regarding current commutation and restriking are already higher than with the classic horn spark gap, but lower than with a parallel fuse of a rated current. With such arrangements, the extinguishing agent-filled areas adjacent to the cutting device can be dispensed with, which reduces the impedance and the space requirement in the main path.

In a further embodiment, the cutting device 4A can be located directly in the ignition area of a horn spark gap 16A. The horn spark gap 16A is short-circuited by a safety tape 1A, if necessary with a bottleneck or a defined I ² t value, and is located directly in the main path.

The securing tape can be guided outside the cutting area between the diverging electrodes.

The cutting or separating blade is designed in such a way that the arc that arises when the strip is interrupted is moved in the direction of the extinguishing chamber and an insulation gap corresponding to the desired dielectric strength is created in the horn spark gap Fig. 15 arises.

For this purpose, the blade is at least predominantly made of insulating material or is held or embedded in insulating material.

After cutting the fusible conductor, the blade is moved forward for several millimeters, so that the distance between the cut fusible conductor remains is greater than 3 mm, but preferably more than 5 mm.

The blade can also be guided laterally next to the diverging electrodes of the horn spark gap in grooves 19A made of insulating material, thereby avoiding a lateral arc flashover.

In addition to the activation by the actuator 5A, it can also be provided that the fusible conductor is thermally separated or moved out of the area between the two electrodes in such a way that an isolating path is created. The blade can also be provided with a mechanical pretension, which allows penetration into the area of the diverging electrodes even without activating the actuator. Such embodiments are known from the field of separation devices, among other things for varistors.

The arrangements and embodiments explained can also be actuated with other internal or external actuators.

Arrangements with spring accumulators are also possible here.

Fig. 16 shows an arrangement with an actuator 5A with a short but variable stroke. For example, piezoceramics or similar can be used as an actuator here.

In this case, the fusible conductor 1A is guided transversely in two insulation parts 20A, which are designed like a punch. By moving the actuator, it is possible to carry out a defined modulation of the constriction 3A of the fusible conductor even after installation and thus to optionally change the characteristic curve of the fuse. It is also possible to completely cut through the fusible conductor if the signal to the actuator 5A is appropriate.

If there are several fusible conductors, the constriction can be cut and embossed by several actuators according to the number of fusible conductors or for several constrictions per fusible conductor. This makes it possible to modify identical fuses for different applications after they have been manufactured. The stamped or embossed parts are preferably made of a material that supports arc extinction, for example Ceramic, polymer or similar. For very fine granular extinguishing agents, the punching area can also be sealed off from the extinguishing agent area by insulation plates 9A. With thinner fusible conductors 1A, this insulation is not absolutely necessary if the extinguishing agent has the appropriate grain size.

The activation of the fuse according to the invention depends on the actuators selected. For example, activation of shape memory alloys or bridge detonators can take place via a current. The electricity can be obtained, for example, from the nearby network or a separate energy storage device. With bridge igniters, the small amount of energy required can also be provided galvanically isolated by a transformer.

The trigger level for activating the fuse is designed so that activation is possible using several criteria. Actively controllable switches can be used here, which have internal evaluation electronics or an external control option. In the simplest case, these switches can also be means that react directly to physical variables and are provided in parallel to the controllable switch. Such switches can react to limit values or changes in temperature, pressure, current, voltage, optical signals, volume or the like or combinations thereof. Electronic, mechanical, voltage-switching and also impedance-changing components can also be used as switches.

The Fig. 17 A further embodiment of the invention shows a fusible conductor 1B with usual constrictions 2B in the form of elongated recesses. Between these usual recesses there is an area with an undiminished cross section 3B, which in this case is of a similar length to the recesses. An exemplary embodiment of an additional mechanical bottleneck 4B is formed within this area. This bottleneck 4B is realized as a diamond-shaped recess with a short overall length.

Such a design has the advantage, particularly when using the fuse according to the invention in the cross branch, that in the event of a short-circuit load, there is no additional arc voltage due to simultaneous arc formation with respect to the additional and the known ones Constrictions are caused, which means that the voltage load on the consumer to be protected remains controllable.

The short bottleneck can be implemented without any significant lengthening of the fusible conductor and without a relevant reduction in the material of the fusible conductor, which is necessary for controlled arc extension. Due to the explained design, the bottleneck does not lead to additional pressure or temperature stress on the fuse housing.

The relatively central position of the additional mechanical constriction surrounded by extinguishing medium, for example common quartz sand, leads to a comparatively high extinguishing capacity when the constriction is destroyed, since in addition to the good cooling and the mechanical extension, the arc is also extended on both sides into the normal range Constrictions can occur quite quickly due to arc burn-off.

In principle, the mechanical pull constriction can also be provided at other positions of the fusible conductor, for example immediately in front of the first electrical constriction in the pull direction of the actuator. However, it should be noted that the free fusible conductor length in the area filled with extinguishing agent may need to be extended in accordance with the desired actively switchable short-circuit currents. The mechanical bottleneck therefore does not necessarily have to be located in the middle of the fusible conductor.

The above allows the activation of the fuse even at high currents with virtual melting times < 10 ms, even if only one bottleneck is separated. The fuse according to the invention can therefore be interrupted practically in a current-free state, at small currents well below the rated current and even high fault currents in the kA ampere range after a short time. Almost any time/current characteristic curve can also be implemented depending on the requirements.

As an alternative to a free fusible conductor guide and a tensile effect on the entire fusible conductor, strain relief on the fusible conductor or partial fixation of the fusible conductor in the so-called "stone sand" is also possible. This allows the force to be directed specifically to a single bottleneck.

When using coarse or angular extinguishing sand, it may make sense to provide the usual, normal electrical bottlenecks between the actuator and the mechanical tension bottleneck with an insulating film, for example, so that the additional friction is reduced.

The Fig. 18 shows a fusible conductor 1B for a capsule fuse with constrictions 2B, which are designed to be longer than usual constrictions in order to achieve short melting times with small overcurrents. In this case, however, the distance of the undiminished cross section 3B of the fusible conductor between the constrictions corresponds at least to the length of the constriction.

This already leads to an advantageous reduction in the rated current of the fuse. With active securing, the expansion of these constrictions increases under a tensile load and the demands on the mechanical, additional constriction increase. In order to achieve optimal extinguishing properties with a simple quartz sand filling, it is advantageous to divide the fusible conductor into several fusible conductors when there are high pulse currents to be controlled and the associated high metal content. Two identically designed fusible conductors are an advantage here.

Figure 19 shows an embodiment in which the further mechanical bottleneck 4B according to the invention is introduced between the normal bottlenecks 2B. With a length of ideally a few 10 µm, this constriction is unsuitable as a usual constriction and does not support its passive function when switching off short circuits. Despite its smaller cross-section, the bottleneck does not respond to these loads, which means that no additional arc voltage is generated. The function is therefore limited to the active control of the fuse.

The length of the bottleneck is at least a factor of 4, but ideally greater than 10, less than the length of the usual, known bottlenecks.

For a mechanical bottleneck with a maximum length of, for example, 500 µm, the usual known bottlenecks are longer than 4 mm. Better conditions result from a length of < 150 µm to lengths of > 2 mm for common, known bottlenecks.

The cross section of the constriction according to the invention is at least a factor of 20% smaller, ideally more than 50% smaller than the normal constriction. The usual, normal bottlenecks have a degree of modulation of approx. 2 to the undiminished cross section. This relatively low degree of modulation makes sense in small sizes due to the small metal content required.

For small fuse designs, due to the limitation of the ratio of fusible conductor material and extinguishing medium for the fusible conductor, copper or copper alloys are usually used.

The tensile force required to tear the bottlenecks is a maximum of 80%, but ideally < 60%, based on the forces that cause normal bottlenecks to tear.

Until the mechanical constriction is torn, the overall fusible conductor for soft copper is stretched by at most 3 mm, preferably less than 1 mm. This corresponds to <5% of the total length of the fusible conductor.

With copper, an elongation of approx. 40% is required to tear the mechanical bottleneck in a diamond-shaped design. The usual constrictions only expand by a total of <8%, even with an individual length of 4 mm, while the undiminished cross section of the fusible conductor only expands by a value of <1%. In the case of shorter constrictions, the expansion can be limited even more to the mechanical constriction despite the force acting on the total length of the fusible conductor. This allows complete integration into a standard, small fuse size, even with unfavorable materials.

The possible stroke distance within the safety device is limited to at least twice the distance required to safely tear the mechanical bottleneck and is designed accordingly. However, the path can also be made longer to achieve sufficient dielectric strength.

By limiting the tensile force to only one area of the fusible conductor with the mechanical bottleneck, the expansion can be further reduced.

The 20a to 20c show design variants of the additional mechanical bottleneck.

In Fig. 20a a fusible conductor 1B with four normal constrictions 2B with a modulation degree of 2 is shown. The length of the constrictions is 4 mm, which means that the nominal current can be reduced to approx. 160 A. The heating of the bottlenecks at a load of 25 kA 10/350 µs is approx. 700°C, although there is still sufficient aging stability. The mechanical predetermined breaking point 4B is dimensioned so that it can be produced using the simplest punching processes and at the same time as the normal, known bottlenecks. The length is, for example, 0.5 mm. However, the cross section of the transversely arranged elongated holes is reduced by 20% compared to the normal narrow areas. Under impulse loads, the temperature of this constriction is the same as the temperature of the other constrictions.

In Fig. 20b A bottleneck 4B is shown with the same overall length, but with a diamond-shaped geometry. The diamonds significantly shorten the area of the minimum remaining cross-section compared to the total length. The remaining cross section can be reduced to 60% of the remaining bottlenecks at the same temperature. The reduction in the force required to destroy the mechanical bottleneck is in the same range. The design of such bottlenecks or similar bottlenecks is limited solely by the technology and costs for reproducible production.

According to Fig. 20c a bottleneck design 4B can take place, which is limited to thickness modulation. The fusible conductor 1B is not shown in this illustration in a top view of the width of the fusible conductor. The view refers to the thickness of the fusible conductor 1B in side view. With a uniform, two-sided modulation over a total short constriction length 4B, for example of only 50 - 150 µm, the cross section and the required force can be reduced to approx. 40% compared to the normal constrictions in the case of pulse currents with the same heating. In the one shown Fig. 20c The remaining thickness in the constriction area, which is uniform across the width of the fusible conductor, is approximately only a third of the total length of the constriction.

The variant according to Fig. 20c discloses a design which allows a sufficiently uniform current density distribution for pulse currents with very strong cooling of the bottleneck. The heating of the bottleneck in the case of pulse currents can therefore be achieved despite the smaller residual cross-section and sufficiently Force reduction can also be well below normal constrictions if this is beneficial for the overall function. The assumed same temperature increase for pulse currents, in which the response of the bottlenecks is to be avoided, leads to higher temperatures at the normal bottlenecks for line-frequency currents, whereby the formation of arcs can be avoided with passive behavior at the pulling bottleneck. When loaded with a short-circuit current of approx. 4 kA and a virtual melting time of approx. 10 ms, the temperature at the drawing or drawing constriction is only 211°C (T0 = 22°C) when the melting temperature is reached at the usual, known constrictions .

In Fig. 21a and b an exemplary structure of an NH fuse in capsule design is shown in detail. The Fig. 21a shows the normal state and the Fig. 21b the triggered state.

The fuse preferably has an insulating housing 5B, two main fusible conductors 1B, and a metal end cap 6B on both sides for connection, on which the fusible conductors 1B are contacted.

With a small size, the fuse has a version for at least one or two control connections 8B for activating the igniter 7B. The control connections 8B can be led out axially or radially from the housing or the end caps of the fuse. Wireless activation is also possible for larger versions.

The ignition device, designed for example as a bridge igniter 7B, is located in a small cavity 9B surrounded by a projectile 10B, which is guided in a type of piston 11B. In this case, two fusible conductors 1B are firmly connected to the projectile 10B, each with a central mechanical constriction 4B.

The connection can be positive or non-positive, for example by soldering, welding or clamping.

The fusible conductors are preferably clamped under pressure between a conical region of the projectile 10B and a further conical part 12B. When the projectile 10B is subjected to a force when the bridge detonator 7B is actuated, the clamping force increases further, so that the clamping force can be released Clamp connection is not possible. If the installation space is small, the parts can be cylindrical and the fusible conductors can be shaped as half-shells.

Below the piston 11B, the fusible conductors are located in a space 13B filled with extinguishing agent. Quartz sand is the preferred extinguishing agent. Preferably all bottlenecks in the fusible conductors are surrounded by the extinguishing agent.

The piston 11B is located in an intermediate part 14B, which delimits the space with extinguishing agent from a cavity 15B above the projectile 10B.

The intermediate part 14B can consist of an insulating part or partially or completely made of electrically conductive material.

The intermediate part 14B can be cup-shaped and rest on the housing part 5B with an edge.

Between the intermediate part 14B and the end cap 6B, a substantially annular part 16B can be provided, on which the fusible conductors 1B are contacted by the end cap 6B.

If necessary, a current flow between the fusible conductors 1B and the end cap 6B via the intermediate part 14B can be prevented by a suitable choice of material or an insulation layer.

The end cap 6B and the parts 5B and 14B as well as 16B are designed in such a way that the fuse is finally closed by pressing on the end cap 6B.

In the area of the part 14B below the piston 11B there is an effective seal against the extinguishing agent, which does not allow the extinguishing medium to de-densify even when the fusible conductors move.

The two fusible conductors 1B are implemented above the piston 11B and the projectile 10B in the extinguishing agent-free space 15B with areas angled relative to the axis.

When the projectile 10B moves into the extinguishing agent-free space 15B, the sealing guidance between the projectile 10B and the piston 11B is only removed after the fusible conductor has been severed at the mechanical bottleneck 4B.

Shows the separated state Fig. 21b .

The angled areas of the fusible conductors are bent in the opposite direction with minimal effort when moving in the extinguishing agent-free space. Bending the bands does not require pressure equalization in a small volume without extinguishing agent, as the air is not displaced into a closed space. The advantage of this embodiment is that no additional interruption or contacting of the fusible conductor or conductors is necessary for contacting the fusible conductor and the isolating distance extension.

The fusible conductor strips used as examples can be guided through the fuse over a short distance with very low impedance and without additional deflections or movements. Overall, a very low-resistance fusible conductor material is used despite the relatively high elongation at break of such materials. The impedance of the arrangement is low, so that even with high current gradients and high currents, the ohmic and inductive voltage drop across the fuse and thus the influence on the protection level of the arrangement is small. With 25 kA 8/20 µs pulses, the voltage drop is <300 V, preferably less than 200 V.

As an alternative to the arrangement explained, the projectile can also be connected directly or indirectly to the connection caps using a transverse connection tape, a flexible cable, a multiple contact system or similar. In this case, the fusible conductor area ends at the projectile.

When using shape memory alloys or volume-changing materials, a similar structure as described above can be used, whereby the seal between the projectile and piston can be dispensed with. In the case of using shape memory alloys, an embodiment corresponding to the tensile force is also used Fig. 22a and b possible.

In the Fig. 22a and 22b Only one segment of the structure is shown in detail for explanation purposes. The position of the segment within the outlined fuse 17B in capsule design is illustrated with dashed areas.

For simplicity, the functionality is described in accordance with Fig. 22a and 22b only explained using a fusible conductor 1B. The fusible conductor 1B has an im Substantially U-shaped section 18B. The fusible conductor itself is guided through two plate-like bushings 19B and 20B.

The feedthrough is implemented, for example, as a first fixed plate 19 and is located in the area of the U-shaped section of the fusible conductor. The second plate 20B is movable and is located in the transition area to an axial fusible conductor area. Between the two plates, the fusible conductor runs at an acute angle to the second plate 20B.

After the U-shaped area and the second plate 20B and a further plate 21B for sealing off the extinguishing agent, there is the additional mechanical bottleneck 4B. There is no extinguishing agent and no bottleneck in the fuse between the two plates.

When the second plate 20B is subjected to a tensile force in the direction of the U-shaped deflection, the tensile force acts directly as a tearing force on the mechanical bottleneck 4B. The tensile force can be realized via a shape memory element 22B attached directly or indirectly to the second plate, for example by heating it directly or indirectly.

The plates 21B and 19B seal off the U-shaped area of the fusible conductor with the movable plate 20B from the penetration of extinguishing agent.

Areas 23B and 24B are filled with extinguishing agent.

The majority of the usual constrictions of the fusible conductor are located in area 23B. The mechanical bottleneck 4B is located in area 24B. The Fig. 22a shows the described arrangement in normal operation and Fig. 22b the condition after the bottleneck is interrupted.

When you pull on the plate 19B, it presses on the area of the U-shaped fusible conductor guide. The fusible conductor is clamped between the plates and further movement leads to an immediate load on the mechanical bottleneck with a sufficient tensile force, which overloads the mechanical bottleneck 4B.

The activation of the fuse depends on the selected actuators. For example, activation can take place using shape memory alloys or on the bridge igniters via a current. The electricity can come from the adjacent network but also from a separate storage. Here too, with a bridge igniter it is possible to provide the required energy in a galvanically isolated manner using a transformer.

The trigger circuit for activation is designed so that this can be done using several criteria. As already explained, actively controllable switches or switches that react directly to physical variables can be used.

Applying a tensile force to the fusible conductor, which is located in the extinguishing agent to the quartz sand, is also possible with permanent spring force. In one embodiment according to Fig. 23 Now, not a tensile force is applied to a mechanical bottleneck, but rather a tensile force to a soldering point, which can be released, for example, by a reaction film (exothermic reaction) within 1 ms. The extension requires a stroke that includes the length of the soldering path and the required separation distance.

According to Fig. 23 The fuse has a housing 5B with connection caps 6B. The fusible conductor 1B is divided into two areas, which are connected to one another by a solder 25B. A reaction film 26B with exothermic heat generation is arranged in the area of the connection. The reaction of the foil can be triggered via an auxiliary fuse or a spark generator 27B. The control takes place via one or two connecting lines 8B. The connection point is in the area of the fuse with extinguishing agent 13B. This area is separated from an extinguishing agent-free area 15B by a feedthrough 28B. In this area there is a spring 29B, which mechanically biases the fusible conductor 1B. After loosening the solder connection 25B, the fusible conductor 1B is bent in the area 15B (dashed position) and pulled through the area 15B, so that there is a sufficiently long separation distance between the two remaining fusible conductor parts.

Claims (14)

1. A triggerable fuse (4) for low-voltage applications for the protection of devices adapted to be connected to a power supply system, consisting of at least one fuse element (10) located between two contacts and arranged within a housing (6A), and

   comprising a triggering device for the controlled disconnection of the fuse element (10) in the event of malfunctions or overload conditions of the respectively connected device,

   an extinguishing agent (11) being introduced in the housing (6A),

   the at least one fuse element (10) including a multitude of electrical constrictions (2B, 3B), which are designed for the rated load of a respective fuse (A, B),

   characterized in that

   at least one further, additional geometric constriction (4B) is provided which, when subjected to tensile stress, is adapted to be disconnected by rupturing as a function of the triggering device, and

   wherein the at least one further, additional geometric constriction (4B), despite a smaller cross-section at an identical current load, will not respond before the electrical constrictions (2B, 3B) at all current loads, but in a time-delayed manner or at higher loads.
2. The triggerable fuse according to claim 1, characterized in that the at least one geometric constriction has a residual cross-section which is smaller than the residual cross-section of the electrical constrictions.
3. The triggerable fuse according to claim 1 or 2, characterized in that the triggering device controls an actuator.
4. The triggerable fuse according to claim 3, characterized in that the actuator consists of a piston the movement of which is triggered by a bridge igniter, in particular wherein the bridge igniter is located in a cavity and surrounded by a projectile which is guided in the piston, preferably wherein two fuse elements are firmly connected to a respective central geometric constriction at the projectile.
5. The triggerable fuse according to claim 3 or 4, characterized in that the actuator causes a defined extension of the interrupted fuse element, so that a resulting total isolating distance realizes a dielectric strength of at least 2.5 kV.
6. The triggerable fuse according to any of the preceding claims, characterized in that the fuse element has a plurality of conventional electrical constrictions in series, the number of which corresponds to the usual design for the respective rated voltage of the fuse.
7. The triggerable fuse according to any of the preceding claims, characterized in that the at least one further, additional geometric constriction is provided between the electrical constrictions.
8. The triggerable fuse according to any of the preceding claims, characterized in that the triggerable fuse is based on a defined rupturing of the at least one further, additional geometric constriction of the fuse element in the extinguishing agent after activation of a trigger.
9. The triggerable fuse according to any of the preceding claims, characterized in that the at least one further, additional geometric constriction is a geometric predetermined breaking point, in particular wherein the at least one further, additional geometric constriction is a tensile constriction.
10. The triggerable fuse according to any of the preceding claims, characterized in that the melting integral value of the at least one further, additional geometric constriction in the time period of transient pulse current loads is equal to or even greater than that of the electrical constrictions, in particular wherein the at least one further, additional geometric constriction has a residual cross-section which is distinctly smaller than that of the electrical constrictions.
11. The triggerable fuse according to any of the preceding claims, characterized in that the mechanical strength of the at least one further, additional geometric constriction in relation to the direction of force of the actuator is distinctly smaller than the mechanical strength of the electrical constrictions.
12. The triggerable fuse according to any of the preceding claims, characterized in that the at least one further, additional geometric constriction is configured to be distinctly smaller in terms of its dimensions than the electrical constrictions.
13. The triggerable fuse according to any of the preceding claims, characterized in that the length of the at least one further, additional geometric constriction is configured to be less than the length of the electrical constriction by at least a factor of 4, in particular greater than a factor of 10.
14. The triggerable fuse according to any of the preceding claims, characterized in that the at least one further, additional geometric constriction is unsuitable as an electrical constriction.

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