EP2915178B1 - Device for generating a reliable low-impedance electric short-circuit irrespectively of the operating voltage - Google Patents

Description

The invention relates to a device for operating voltage-independent generating a safe, low-resistance electrical short circuit, comprising two electrical, in particular plate-shaped connecting parts, which lead a different potential, wherein between the connection parts an insulation gap is formed and the desired short circuit via a, at least partially, or a penetration Destroy the isolation route is realized, according to the preamble of claim 1. Such a device is besistentsweise from the document FR 2 884 602 A1 known. The realization of a targeted electrical short circuit is a common method for a variety of electrical devices to ensure a safe switching state.

Application finds this method u.a. in the overload of electrical components to prevent overheating or fires, in the realization of defined impedance ratios to avoid dangerous voltages or to ensure defined shutdown conditions, for example by overcurrent protection devices or to delete faulty arcing.

However, the measure "short-circuit" is an agent that is generally initiated only when normal and normal operation of electrical appliances due to overloading or aging no longer exists. The possibilities and the expense of realizing such an additional measure outside basic functions of the electrical devices are limited per se. Often, a targeted short circuit be available even if no or only an undefined network energy is available. The requirements regarding the safety and effectiveness of the action of a targeted short circuit are therefore very high.

The realization of a short circuit to establish a safe state (fail-safe) is a known and common method of avoiding major damage, e.g. in case of overload of components.

The methods of the prior art for the realization of a short circuit are quite different, as well as the respective intended purpose of protection.

In many cases, mechanically actuated switching devices are used to realize a low-resistance and permanent current-carrying short circuit. However, these switching devices generally require an auxiliary power for the actuation, in particular in the case of the desired activation, and are of very complex design.

The space requirement of such devices is often dependent on the type of operation in addition to the dielectric strength and current carrying capacity. At high current carrying capacity in many cases, the mass to be moved is quite high, whereby the closing time and the effort to operate increase.

In order to reduce these actuation times, further expenditure for an accelerated movement up to drives on the basis of blasting caps is often driven.

The conceptual and physical disadvantages can not be completely eliminated despite various solutions in the prior art.

In the case of passive tripping, in many cases, especially in the case of overload-prone components, the heating is used to trigger the short-circuit. Usual are here, for example, spring-biased movable contacts, which are released by the heating of solder or wax.

As an alternative to purely mechanical drives, the control of semiconductors or of hybrid short-circuiters, which consist of semiconductors and mechanical short-circuiters, is also known.

By using semiconductors, the time to reach the short circuit state can be significantly reduced. However, low cost semiconductors in many cases do not have sufficient current carrying capacity. The realized short circuit is also not low-impedance and it is the effort to control and protect the semiconductor and their EMC-safe use in many applications high.

Furthermore, the use of physical boundaries, e.g. Dielectric strength, voltage and current gradient and more difficult. In addition to these solutions, the use of plasma switches or ignitable spark gaps for the realization of short circuits is already known.

Such solutions have the advantage of a high ignition speed and a high pulse current carrying capacity and a relatively well adjustable dielectric strength. The disadvantage, however, is that no galvanic short circuit can be realized and the continuous current carrying capacity is limited due to the burnup. The effort for the rapid ignition of such solutions is also very high and generally requires an auxiliary energy as energy storage. Since the principle of these known solutions also relies on the use of a switching arc, the short circuit is only limitedly suitable for protection with very low-impedance faults.

From the field of overvoltage protection protective devices are furthermore known in which e.g. heating-expanding materials are used to cause movement of contacts. The targeted control of such materials, for example with an additional heating element is known.

From the foregoing, it is therefore an object of the invention to provide an advanced device for operating voltage independent generating a safe, low-resistance electrical short circuit, which Space-saving, cost-effective and independent of the operating voltage realized the desired short circuit.

On the one hand, the short circuit should be active, that is, it can be deliberately brought about with the help of an external or internal activation, and on the other hand it can also be passive, independently of achieving at least one defined condition. The active control is to be realized by as diverse as possible individual criteria, but also by ORs of these criteria. Furthermore, the short-circuit device to be created should manage without expensive mechanical drive and react very quickly, so that reaction times are similar to those of electronic switching elements. The short circuit to be realized should also enable a selective disconnection of overcurrent protection devices and be suitable for the conduction of continuous currents. Accordingly, it is desired that the device provide a low resistance galvanic connection suitable for persistent currents. Also, the parts required for the short circuit and the control should be executable as a ready-to-connect supplementary unit.

The object of the invention is achieved with the combination of features according to claim 1, wherein the dependent claims comprise at least expedient refinements and developments.

The basic idea of the invention is to distinguish between two, e.g. plate-shaped parts which lead to a different electrical potential, at least in each case an insulating film and an exothermic mass, which is preferably also executable as a film to arrange.

The connecting parts with different potential have a distance of a few 10 microns to a few 100 microns.

The mentioned exothermic mass is preferably close to ground or at ground potential. The mass can now be activated by a voltage pulse, a current pulse, by a mechanical shock or pressure or an intense light pulse or even during or by electrical discharge and diversion processes.

In addition, the exothermic mass is quasi passively subject to activation even when reaching a defined temperature.

The reaction of the exothermic mass leads to melting or to a deformation of the insulating film forming the insulating film within a very short time, whereby the potential separation is canceled and a short circuit between the floating parts can be produced. The realization of the short circuit can be supported by additional design measures and variants described in the embodiments.

In a preferred embodiment, therefore, the connection parts are arranged closely adjacent to the isolation path. The insulation gap can, as already stated, be formed as an insulation film, but also as a film-like coating. In the immediate vicinity of the isolation route is the aforementioned exothermic mass, which releases its exothermic energy when energized and leads to melting or destroying or deforming the insulation section, so that the potential separation between the connection parts is canceled and enters the desired unique short circuit case.

At least one of the connecting parts can be under mechanical prestress, so that when the insulation section is destroyed or deformed, the connecting parts come into contact with each other via a mechanical movement that then occurs.

In one embodiment of the exothermic mass as a film, this can be a sandwich arrangement with the insulation gap, which in turn can also be formed by a film.

The exothermic mass is designed and dimensioned such that sufficient heat is released within a period of about 1 to 10 ms in order to melt or significantly deform the insulation film or insulation layer.

In one embodiment of the invention, the exothermic mass is integrated in one or both of the connecting parts.

Furthermore, arranging of easily melting metals or metal layers can take place in the area of the formation or arrangement of the exothermic mass.

The short-circuiting device therefore consists of two e.g. plate-shaped electrically conductive parts having generally different potential, between which at least one respective insulating film and an exothermic mass, which is preferably also formed as a film is brought. The two electrically conductive parts with generally different potential can be connection or connection elements of the device to be protected by short circuits or else a component of a connection-ready supplementary unit "short-circuiter".

The electrically conductive parts have a distance of a few 10 microns to a few 100 microns. One or both parts can be under a mechanical preload, which in the simplest case is created by the joining of the parts and the material properties. The thickness and the material properties of the electrical insulating film determine the maximum rated voltage and the transient dielectric strength of the short-circuiting device. In addition to the breakdown properties of the film, of course, the flashover properties and the influences of the corresponding environmental conditions must be observed. However, the operating voltage range can be easily selected from the range of the safety extra-low voltage to the low-voltage range without any functional limitations.

The exothermic mass develops after its active or passive activation immediately at the activation site within a period of less than 1 ms so much heat that the insulation film melts. When using the exothermic mass in film form and with active ignition at only one point of the mass, the exothermic reaction within the film continues at high speed, so that even with large required contact surfaces generally one activation point is sufficient. Due to the rapid release of the heat, the influence of the heat capacity and heat conduction of the electrically conductive connection parts (short-circuit contacts) is almost negligible.

The energy input can be considered almost adiabatic and the amount of energy of the exothermic mass must be measured only to melt the film. This allows a very simple integration of the device in numerous existing devices to be protected, since the space required in the usual tolerance range of the items of technical equipment.

The exothermic mass is preferably close to ground or at ground potential. The mass or film can also be integrated in an electrically conductive connection part, so that only the insulation film determines the spacing of the conductive parts. In the formation of the exothermic mass as a film, the film itself may be electrically conductive and similarly thin designed as the insulating film, so that the cost of introducing the exothermic mass is negligible. The insulating film and the exothermic film can also be designed as a composite material in sandwich form with a suitable design of the electrically conductive parts. The insulating film can also be surrounded on both sides by an exothermically reacting mass (foil). This intensifies the melting process of the insulation film.

If large-area electrical connections, for example, be realized for higher continuous currents, it makes sense for the material of the molten insulating film to create one or more areas in which the melt residues can be urged to make the shortest possible low impedance. The cavities or channels can be integrated into the electrically conductive connection plates. In the case of an electrically conductive exothermic mass, it may also be designed to accommodate or specifically displace the melt.

The targeted influence on the melt of the insulating material is useful even at low operating or residual stresses in the fault state, eg in arcs, so that even with the low film thicknesses no minimum air or sliding distance remains despite molten film. The pure displacement effect of the melt of the insulating film is supported by the heat of reaction, the first current flow, possibly with minimal discharge formation, and by a minimum bias of the connecting parts. In addition, in the reaction area also easily melting metals (low heat conduction, low heat capacity, low melting temperature), for example, as a coating of the films, the exothermic film or the connecting parts are used. The resulting molten metal bridges the minimum gap after melting the insulation film.

In many applications, however, it is sufficient to stack only the insulating film and the exothermic mass as a foil only between the electrically conductive connection parts. Even with insufficient displacement of the melt of the reaction film occurs with minimal voltage differences after the reaction of the film, a flashover of the film residues. A point of discontinuity which promotes this slip-over at minimum stress is, for example, the overlapping area between insulation film and exothermic film / n, which is required in any case to ensure a sufficient dielectric strength of the sliding distance of the device to be protected during normal operation, especially in the case of simple stack arrangements.

In addition to the preferred melting of a defined insulation layer, the exothermic reaction can also be used to accelerate thermal processes for melting or moving parts.

The presented arrangement allows the bi-functional use of the exothermic reaction for the preferred realization of a short circuit. The reaction can be triggered on the one hand purposefully and independently of the environmental conditions of the film or the device, for example by a remote control. On the other hand, influence or reference variables of the immediate surroundings of the film or signal quantities of the device can be used directly or indirectly. The application possibilities are therefore almost unlimited.

The purely passive reaction of the film upon reaching a limit temperature can be used, for example, in components or devices in which higher temperatures lead to overloading or a fire hazard. This feature has a redundant effect in many applications where active activation fails. To the passive thermal activation, the film can be placed in direct thermal contact with the component at risk of overload, or the heat via a thermal coupling. The passive thermal reaction of the film can also be used via an additional heating element. Due to the very low heat capacity and low heat conduction, the exothermic reaction can be achieved only with a nearly selective energy coupling and low power. The required power corresponds to only a fraction of thermally sensitive enamel, such as solders, waxes etc.

In addition to the already described pure reaction of the film at a defined temperature, there are also numerous possibilities for active activation. The mass can be activated for example by a voltage pulse, a current flow, by mechanical impact, an intense light pulse or electric discharge or charge processes.

The required activation energy is extremely low. This allows numerous possibilities for the targeted internal activation of the mass as a function of specific functions of the devices to be protected or also for external activation. A voltage pulse can be generated in the simplest case by a defined flashover distance or by means of discrete components which respond to overvoltages. A current flow can be generated by the targeted electronic or mechanical connection, for example, the supply voltage of the device or an available auxiliary voltage source generated in the exothermic mass. For this purpose, the transfer of a capacity, a battery or the like is also sufficient.

In addition to the use of current and voltage or the associated sparking, for example, a laser pulse or a strong mechanical impulse can be used for example directly by a firing pin or by strong vibration. These options therefore allow the use of a simple mechanical or electronic shutter, for example by applying the mass with a current flow or a charge, which may be remotely operated. In addition to the remote control and auxiliary sizes can be used. Components, such as thermal switches, NTC, PTC, GDT's, varistors, Hall sensors, piezo elements, etc., which can react to internal load variables defined, are connected internally or deliberately switched from the outside. Also suitable for igniting the mass is the thermal overload of current bridges, for example, fusible conductors, which can be used both for thermal heating or for spark formation.

For devices or components which do not trigger (or not timely) an activation signal e.g. allow at very fast overload, the ignition of the mass can also be done by the destruction of the components themselves and the device can be spent by the realization of a defined short circuit in a safe state. The rollover or destruction of electrical or electronic components generally generates sparks, arcs or hot ionized gases. The accompanying phenomena could be used directly for an activation of the mass.

In addition to the previously described measures, which are aimed in particular at the melting of an insulating film by the reaction of the mass, a further effect for the realization of a short circuit can be used. In the design of the mass as an electrically conductive film, the exothermic chain reaction within the film leads to sudden deformations. By this effect, the film is pressed into available cavities, similar to a deep-drawing process. The occurring deformation and force development can be used for targeted direct or indirect bridging of insulation distances, which can be realized before the complete melting of an insulating film, a short circuit. The realization of the short circuit can therefore be supported by appropriate additional design measures and design variants of the contacts. Due to the numerous application and execution options, the variants shown can only give a rough and non-limiting overview. The illustrations are limited for clarity also on the execution of the exothermic mass as a film.

The invention will be explained in more detail below with reference to exemplary embodiments which do not restrict the scope of the invention.

Fig. 1

eine prinzipielle Grundanordnung zur Realisierung eines Kurzschlusses mit exothermer Masse;

Fig. 2

eine Anordnung, bei der die Isolationsfolie zwischen zwei Folien aus exothermer Masse befindlich ist;

Fig. 3

eine Anordnung, bei welcher die Anschlussteile bzw. die Folie zusätzlich mit einer elektrisch leitenden Masse mit niedriger Schmelztemperatur beschichtet ist;

Fig. 4

die Anordnung von Hohlräumen oder Kanälen in einem Anschlussteil;

Fig. 5

eine Darstellung ähnlich derjenigen nach Fig. 4, jedoch mit einem größeren Hohlraum, in dem ergänzend ein Dorn angebracht ist;

Fig. 6

eine Anordnung, bei welcher die Isolationsfolie eine Ausnehmung im Bereich eines Hohlraums besitzt,

Fig. 7

eine Anordnung ähnlich derjenigen nach Fig. 6, jedoch nach erfolgter exothermer Reaktion und Verformung;

Fig. 8

eine grundsätzliche Anordnungsvariante, bei der die Aktivierungsteile relativ zentral an der Folie befindlich sind, um bei relativ großen Flächen zu gewährleisten, dass durch die interne Reaktionsgeschwindigkeit innerhalb der Folie an den Randbereichen die notwendige Schmelzwärme für die Folie nahezu zeitgleich zur Verfügung steht;

Fig. 9

eine Anordnung ähnlich derjenigen nach Fig. 8, wobei ein zusätzliches Element z.B. als Impedanz, Funkenstrecke oder Schmelzdraht vorhanden ist;

Fig. 10 und 11

Anordnungen mit einem Gehäuse, welches für eine nachträgliche Anbringung des Kurzschließers an das zu schützende Gerät oder Bauteil geeignet sind, und

Fig. 12 und 13

einen beispielhaften Einsatz der Kurzschließeranordnung mit einem zu schützenden Bauteil in einem gemeinsamen Gehäuse.

The figures show:

Fig. 1

a basic basic arrangement for the realization of a short circuit with exothermic mass;

Fig. 2

an arrangement in which the insulating film between two sheets of exothermic mass is located;

Fig. 3

an arrangement in which the connecting parts or the film is additionally coated with a low-melting-temperature electrically conductive mass;

Fig. 4

the arrangement of cavities or channels in a connection part;

Fig. 5

a representation similar to that after Fig. 4 but with a larger cavity in which a mandrel is additionally attached;

Fig. 6

an arrangement in which the insulating film has a recess in the region of a cavity,

Fig. 7

an arrangement similar to that after Fig. 6 but after the exothermic reaction and deformation;

Fig. 8

a basic arrangement variant in which the activation parts are located relatively centrally on the film to ensure at relatively large areas that the necessary heat of fusion for the film is available almost simultaneously by the internal reaction rate within the film at the edge regions;

Fig. 9

an arrangement similar to that after Fig. 8 in which an additional element is present, for example as an impedance, spark gap or fusible wire;

10 and 11

Arrangements with a housing, which are suitable for subsequent attachment of the short-circuiter to the device or component to be protected, and

FIGS. 12 and 13

an exemplary use of the short-circuiting arrangement with a component to be protected in a common housing.

In Fig. 1 a principle basic arrangement for the realization of a short circuit is shown. The plate-shaped connection parts 1 and 2 can be existing electrically conductive parts of the device to be protected or also additional parts which are inserted into the device. The essential components represent the exothermic mass, for example in film form 3 and the insulating film 4. Both parts each have a thickness of only a few 10 microns. The part shown as a spring element 5 is not mandatory. Due to the short distances, a clamping connection of the parts or even the intrinsic elasticity of the parts is generally sufficient. When integrating the exothermic mass 3 in the connection part 1, for example in a trough-shaped recess, the distance between the connecting parts 1 and 2 can be reduced to the thickness of the insulating film 4. The insulation film 4 and the connection parts 2 are designed so that the electrical voltage resistance between the connection parts 1 and 2 corresponds to the electrical breakdown voltage of the insulation film. In Fig. 1 is realized, for example, only by the appropriate design of the supernatant of the insulation film, so a corresponding dimensioning of the sliding distance of the film 4 of parts 1 to Part 2. Alternatively, of course, all the usual measures to increase the dielectric strength between the parts 1 and 2 can be used.

The Fig. 1 limited to the passive triggering of the exothermic reaction, in the case of heating the film 3 to the reaction temperature. This heating could be done for example by thermal conduction through the connection part 1. Upon reaching the reaction temperature, the Foil 3 within a few microseconds to ms release a sufficient amount of energy to melt the insulating film 4 in the contact area. As a result, the electrical insulation strength of the film between the parts 1 and 2 is repealed and there is a short circuit between the two connection parts. In the arrangement accordingly Fig. 1 the exothermic mass 3 is electrically conductive both before the reaction and after the reaction. However, this is not absolutely necessary due to the small dimensions of the film 3. In general, in a clamp connection, the residual stress of the parts is sufficient to realize a low-resistance metallic connection of the parts 1 and 2 with sufficient current carrying capacity. The melt residues of the film 4 are generally displaced from the contact area by the applied pressure of the clamping connection. In an integration of the mass 3 in the connection part 1, the distance between the electrically conductive parts 1 and 2 is also independent of the properties of the mass. 3

Fig. 2 shows an arrangement in which the insulating film 4 is disposed between two sheets of exothermic mass 3. With this arrangement, the insulating film can be supplied with the required heat of fusion from both sides. This has several advantages. A film 3 may, for. B. are used exclusively for passive triggering by heating and the other film can be actively controlled. If required, both sides can also be used for passive monitoring at the same or different trip temperature. In addition to the advantages of alternative tripping, there is also the advantage that stronger insulation films can be destroyed and that the destruction of the insulation layer can be accelerated. In the reaction of a film 3, such a high radiation intensity is produced that the film is automatically activated on the opposite side of the insulating film, for example in the case of optically transparent insulation films 4.

In Fig. 3 an arrangement is shown in which the connecting parts or the film 3 is additionally coated with an electrically conductive material having a low melting temperature 6, for example low-temperature solder. The solder can also be added as an additional film. This additional material can realize several functions. The material can serve as a defined heat transfer barrier to the terminals to the optimally transfer resulting heat of reaction to the insulation film and the additional material. The resulting melt of the low-melting material can be used for rapid and large-scale bridging of the isolation gap. The melt can also serve for permanent soldering of the terminals 1 and 2 and thus take over a mechanical function after the reaction to realize a permanent short circuit in addition to the electrical function.

The incorporation of channels, grooves or cavities in one or both terminals can be used in particular for larger required contact surfaces between the terminals for receiving melt residues of the insulating film or for their targeted displacement from the contact area.

Fig. 4 shows in the terminal 2, for example, such an arrangement of cavities / channels 7. It should be noted, however, that the real contact surface remains sufficiently large.

In Fig. 5 a similar arrangement with a larger cavity 7 is shown. In addition, a mandrel 8 can be mounted in the cavity. At the onset of the exothermic reaction, the material 3 deforms very strongly, causing a kind of deep drawing process of the material into the cavity 7. In the case of thin or relatively elastic films 4, these are already drawn into the cavity before melting and destroyed on the mandrel 8, so that the short circuit is realized even before complete melting of the insulating film and also before the displacement of the remainder of the film.

Fig. 6 shows a similar arrangement in which the insulating film has a suitable recess 9 in the region of the cavity, whereby a movement of the insulating film 4 by the exothermic film 3 in the reaction is not necessary. The short circuit between the electrically conductive exothermic mass 3 is realized by the contact of the mandrel 8 or also directly of the terminal 2 after the deformation of the film 3.

Fig. 7 shows the arrangement accordingly Fig. 6 after the exothermic reaction and the deformation of the part 3.

The active control of the exothermic mass can, as already described, take place in very different ways. Only a few exemplary and non-limiting embodiments can be shown here.

Fig. 8 shows a possible basic arrangement, wherein the activation point takes place relatively centrally on the film 3. This ensures, in particular for relatively large areas, that the necessary heat of fusion for the film 4 is available almost at the same time due to the internal reaction speed within the film at the two edge regions. In principle, however, the film 3 can also be activated at an edge region or at several points. The activation of the film 3 takes place in the arrangement via an electrically conductive connection line 11.

This line can be soldered to the film 3, clamped or even just hang up. There may also be a minimum distance between the conduit 11 and the part 3. The cable cross-section can be very small << 1mm ² . The requirements of the electrical insulation of the line 11 with respect to the connection part 1 is negligible, as long as the contact or the distance to the part 3 is guaranteed or less. The component 10 in the electrical connection line 11 may be located within the device to be protected or outside. The component 10 itself may be a sensor or a controllable element which responds to requirements within the device to be protected or external conditions or signals. The component 10 may be an electrical switch or mechanical switch. By its operation, a potential is applied to the film 3, which differs from that of the film 3 and the terminal 1, whereby a charge compensation takes place. The film 3 is activated by the current flow or the discharge (sparking by current flow or flashover) in the contact area Part 3 and Part 11. The part 10 may also be designed as NTC, PTC, GDT, varistor, Zener diode, thermal switch, piezoelectric elements, etc. By choosing the sensor a variety of internal or external variables are used for activation. Due to the very low energy requirement for activation, also wireless methods (transmitter-receiver) can be used without restrictions.

In Fig. 9 a similar arrangement is shown. The additional element 12 may be designed, for example, as an impedance, spark gap or else as a fused wire with a defined I ² t value. This allows, regardless of the amount of charge available, a defined generation of sparks, which cause the reaction of the film 3 very effectively and very quickly. The speed of triggering the film can be significantly increased compared to the heating of the film by a current flow without sparking.

Alternatively to the activation accordingly Fig. 8 and 9 Of course, laser or firing pin, for example, act analogously to the fuse on the film 3 and trigger targeted.

The 10 and FIG. 11 show arrangements with a housing, which are suitable for a subsequent attachment of the short-circuiter to a device to be protected / component. In Fig. 10 will be out Fig. 1 known arrangement in a housing 13 made of metal. The connection element 1 is directly connected to the housing. However, the housing 13 can also be used as a connection element 1 itself. The terminal 2 is insulated from the housing 13 led to the outside. The bushing 14 serves for insulation and the part 15 for the outer connection. A further connection 23 can be guided through the housing 13, which can be used to actively activate the film 13 with an outer component 10. The passive activation of the film 3 takes place by the heat transfer from the housing or connection 1 to the film 3.

Fig. 11 shows a similar arrangement, however, the housing 13 is made of insulating material and has two passages for the outer terminals 15, 16 of the connecting elements 1 and 2. The passive heating of the film 3 can take place via the terminal 16. Alternatively, the housing 13 may also have an outwardly directed heat transfer element 24 include. This can be electrically isolated or electrically connected to the connection element 1.

Fig. 12 and Fig. 13 show an exemplary use of the short-circuiting arrangement with a component to be protected in a common housing. The housing has in each case three connections 17, 18, 20, which are all led separately to the outside in a housing made of insulating material 22. This allows separate external wiring of the short-circuiter via the outer terminals. In principle, however, the short-circuiting device can also be wired inside the housing, whereby the outer connection 20 would be omitted. As a component to be protected, a surge arrester, in particular a varistor 19 was selected to explain the function. It is well known that varistors can become very hot or overturn at the risk of overloading. In Fig. 12 is a flashover, which is connected to a spark discharge 21, indicated. In the arrangement of the short-circuiter accordingly Fig. 12 the film 3 is heated directly through the varistor. The connection 1 of the short-circuiter can in this case simultaneously be the connection plate 18 of the varistor. Upon reaching the reaction temperature of the part 3, the insulating film 4 is melted and causes a short circuit between the terminals 18 and 20. If the varistor is bridged by a spark discharge 21, the terminals 18 and 20 are also low-resistance short-circuited after the activation of the film 3 by the flashover, whereby the bursting of the housing 22 due to an open arc can be prevented. The insulating film 4 may be cast in the housing 22 to increase the flashover resistance between the terminal 18 and the terminal 2 or 20.

Fig. 13 shows a similar arrangement as Fig. 12 However, the supernatant of the insulating film 4 between the terminal 1 and the film 3 and the terminal 2 is pronounced as a sliding spark gap. The spark gap can be dimensioned such that, with a corresponding connection of the terminals 17, 18, 20, an undefined flashover of the varistor between the terminals 17 and 18 is avoided and the foil 3 is ignited immediately to realize a short circuit. The endangerment of the housing 22 by the pressure generated in an undefined flashover can be further reduced by this measure. As an alternative to sliding discharge, it is of course also possible to use GDTs or other voltage-switching elements. In addition to these examples for a bi-functional release of the short-circuiter within a device, it goes without saying that further internal or even external sensors can be used for activation. In addition to pure OR operations, AND operations for activating the short-circuiter can also be implemented with discrete components (without logic or PLC units).

The terms used in the description and in the embodiment of an active or passive activation of the exothermic mass are based on the manner of introducing a corresponding activation energy. Passive mechanisms are to be understood here, which result in the usual use of the device to be protected without specific intervention in the risk of overloading or by the overload itself. This can be the case of a varistor, for example, the heating due to a current load. The exothermic mass, e.g. designed as a reaction foil ignites it as a result of the passive heat input at its ignition temperature without additional ignition aid. In this case, the protective mechanism can optionally be triggered against damage to the component to be protected. Under passive activation but also the triggering due to the sparking at an outer rollover of the varistor should be understood, in which case there is already a damage to the actual component and the protective measure is only to mitigate damage, for. to avoid a bursting of a housing.

Active mechanisms are those that are independent of the state of the components. These can be current, voltage, power of the corresponding component, which should be protected accordingly. However, active mechanisms are also those which can be used outside the passively protected component for triggering. For example, the short-circuiting device according to the invention, which is used passively to protect an overvoltage protection device, can also be used to extinguish an external arc due to active activation, which would not actuate the short-circuiting device via the passive triggering mechanisms, eg due to the local distance.

In a purely passive use so no active control, but also no separate ignition device is necessary. With an active ignition, the activation always takes place via a separate ignition device.

The preferred reaction film used as an exothermic mass should have a small thickness and allow a fast, self-propagating exothermic reaction. The film should be both passive and active to their exothermic reaction initiation can be performed, with a pressure to avoid development and primarily to ensure heat development.

As a reaction foil, e.g. the product Nanofoil (registered trademark) can be used.

As insulation film, a known technical insulation film for electrical applications can be applied, which has a high dielectric strength and has a continuous use temperature, which corresponds to the application of the device to be protected. For example, PE, PET, PS, PP, PSU, PA6 and PC films with an electrical breakdown strength of> 30 KV / mm are suitable here.

The reaction film as an exothermic mass and the electrical insulation film can be sandwiched, i. also such that reaction films are located on both sides of the insulating film.

LIST OF REFERENCE NUMBERS

1

first plate-shaped connection part

2

second plate-shaped connection part

3

exothermic mass in foil form

4

insulation blanket

5

elastic or self-sprung mass or spring with minimum stroke

6

easily melting electrically conductive material

7

Cavities or channels

8th

mandrel

9

opening

10

Sensor; switching element

11

electrically conductive connection, contact

12

Impedance, spark gap

13

Metallic housing

14

electrically insulating bushing

15

connecting element

16

connecting element

17

Connection of the overvoltage protection element

18

Connection of the overvoltage protection element

19

Overvoltage protection element e.g. varistor

20

external connection of the second plate-shaped connection part 2

21

Überschlagsweg

22

Housing of the overvoltage protection element

23

Connection for activating the foil 3

24

Heat transfer element

Claims (7)

1. A device for generating a reliable low-impedance electric short-circuit independently of the operating voltage, comprising two electric connection parts (1; 2) which are plate-shaped in particular and which carry a different potential, wherein an insulating section (4) is formed between the connection parts (1; 2), and the desired short-circuit is implemented by at least partly penetrating or destroying the insulating section (4), wherein the connection parts (1; 2) are arranged closely adjacent to each other, and the insulating section (4) is formed as an insulating foil or a foil-like coating, characterized in that the connection parts (1; 2) are arranged in a stacked manner under inclusion of the insulating section (4), and an exothermic mass (3) is located in the direct vicinity of the insulating section (4), said mass releasing its exothermic energy when energy is applied and thus producing the melting or deformation of the insulating section (4), such that the galvanic isolation between the connection parts (1; 2) is removed and the short-circuit event occurs, wherein the exothermic mass (3) is formed as a foil which forms a sandwich assembly with the insulating section (4).
2. A device according to claim 1, characterized in that at least one of the connection parts (2) is under mechanical pretension, such that upon destruction or deformation of the insulating section (4) the connection parts (1; 2) come into mechanical and electrical contact with each other.
3. A device according to one of the preceding claims, characterized in that the connection parts (1; 2), in the short-circuit-free state, have a distance from each other of a few 10 µm up to a few 100 µm.
4. A device according to one of the preceding claims, characterized in that the activation of the exothermic mass (3) occurs by means of voltage pulses, light pulses, current flow, mechanical impact or pressure, by electrical charge reversal processes, and also upon exceeding a limit temperature.
5. A device according to one of the preceding claims, characterized in that the exothermic mass (3) is formed and dimensioned in such a way that within a duration of approximately 1 ms to 10 ms sufficient heat is released in order to melt or relevantly deform the insulation foil or insulation layer (4).
6. A device according to one of the preceding claims, characterized in that the exothermic mass (3) is integrated in one or both of the connection parts (1; 2) or is applied there.
7. A device according to one of the preceding claims, characterized in that easily fusible metals or metal layers are disposed in the region of the formation or arrangement of the exothermic mass (3).

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