Electrical cut-off system

Description

[0001] The invention relates to an electrical device and an electrical system for interrupting an electric current.

[0002] The invention is particularly applicable to the field of electrical protection.

[0003] For a long time, fuses have been used to effectively protect electrical equipment and installations against electrical faults.

[0004] Fuses typically consist of a fusible blade housed in a casing filled with a material such as silica. The blade is designed to melt when the current flowing through the fuse exceeds a predetermined value for a specified duration.

[0005] Some modern applications now require the ability to interrupt high-intensity electrical currents with a very fast response time. This is the case, for example, with applications related to electric vehicles or photovoltaic panels.

[0006] In this regard, it has been proposed to combine a pyrotechnic circuit breaker with a conventional fuse, in order to increase breaking performance.

[0007] WO 2018 / 167169 A1 describes an example of such an electrical device, in which a fuse is connected in parallel with a pyrotechnic circuit breaker.

[0008] In this example, the pyrotechnic circuit breaker is configured to trip with a very short reaction time in the event of an electrical fault, and the fuse is configured to ensure total interruption of the current, for example to prevent any reformation of an electrical arc in the pyrotechnic circuit breaker.

[0009] In other words, the fuse helps to interrupt an electrical current that the circuit breaker alone could not have stopped safely and effectively.

[0010] However, the fuse should only be connected in parallel with the circuit breaker when the circuit breaker is triggered, to prevent the fuse from being constantly traversed by an electric current, as this could lead to premature aging of the fuse.

[0011] Furthermore, some known devices do not allow the circuit to be opened when the currents have a low intensity or even (temporarily) zero, which may nevertheless be required for certain applications.

[0012] To achieve this, it is generally necessary to modify the internal architecture of the pyrotechnic circuit breaker, as proposed by WO-2020 / 260382 A1 (or FR-3 098 006-A1), which can however be complicated to carry out industrially.

[0013] Therefore, there is a need for an electrical disconnect device that addresses the above drawbacks.

[0014] In general, the invention relates to an electrical system according to claim 1.

[0015] According to advantageous but not mandatory aspects, such an electrical system may incorporate one or more of the features defined in the dependent claims, the features being taken in isolation or in any technically permissible combination.

[0016] The invention will be better understood and other advantages thereof will become more apparent in the light of the following description of an embodiment of a device for interrupting an electric current, given solely by way of example and with reference to the accompanying drawings, in which: [ Fig 1 ] there figure 1 schematically represents a device for interrupting an electric current comprising an electrical switching element, but not part of the invention; Fig 2 ] there figure 2 schematically represents two alternative switching elements to the electrical switching element of the device. figure 1 : [ Fig 3 ] there figure 3 schematically represents a first state of operation of the device. figure 1 ; Fig 4 ] there figure 4 schematically represents a second operating state of the device. figure 1 ; Fig 5 ] there figure 5 schematically represents a third operating state of the device. figure 1 ; Fig 6 ] there figure 6 schematically represents another embodiment of the device of the figure 1 according to the invention [ Fig 7 ] there figure 7 schematically represents two examples of the construction of an electrical switching element, respectively for the switching device of the figures 1 And 6 (insert a) and for the shut-off device of the figure 8 (insert b), not forming part of the invention; [ Fig 8 ] there figure 8 schematically represents another possible implementation of the device. figure 1 , not being part of the invention.

[0017] There figure 1 represents an electrical system 2 configured to interrupt an electric current, for example to protect an electrical load or an electrical installation.

[0018] Device 2 includes a circuit breaker 4 having terminals 6 and 8, allowing the circuit breaker 4 to be connected to an electrical circuit, for example between an electrical load and a generator.

[0019] Device 2 also includes an electrical device 10 and a fuse 12 electrically connected in parallel with the circuit breaker 4 between terminals 6 and 8.

[0020] For example, fuse 12 is a fuse cartridge containing one or more fuse blades F2.

[0021] In general, the circuit breaker 4 can be switched from an electrically conductive state to an electrically blocking (or open) state.

[0022] The circuit breaker 4 may be a pyrotechnic circuit breaker. For example, the circuit breaker 4 may contain an explosive charge configured to, when triggered, physically sever an electrical conductor extending between terminals 8 and 6 of the circuit breaker 4.

[0023] In the illustrated example, the circuit breaker 4 comprises a body 20 and a breaking element 22 (such as a piston) configured to move by translation in the body 20, for example following the triggering of a pyrotechnic charge (not illustrated).

[0024] The breaking element 22 is configured to sever an internal electrical conductor housed inside the body 20, this electrical conductor connecting terminal 6 to terminal 8.

[0025] On the figure 1 The circuit breaker 4 is shown in a triggered position. The electrical conductor, cut by the breaking element 22, is divided into a first portion 24 which extends the first terminal 6, a second portion 26 of conductor which extends the second terminal 8, and an intermediate portion 28 located between the first and second portions 24, 26 of the electrical conductor.

[0026] An electrode 29, whose role will be specified below, is arranged in the cutting chamber, such that its free end is placed opposite and at a distance from one or the other of the portions 24 or 26.

[0027] The electrode 29 can be made of any conductive material, for example aluminum, tungsten, or preferably copper (particularly for cost reasons). The electrode 29 can be directly overmolded into the body 20 (to improve sealing).

[0028] The circuit breaker 4 can be a fuse cartridge, or an electromechanical device, such as for example an electromagnetic contactor, or a semiconductor switch, or any other suitable device.

[0029] The electrical device 10 comprises a body 30 delimiting a closed internal volume, a first electrode E1, a second electrode E2 and a third electrode E3.

[0030] Electrodes E1, E2, and E3 can be made of any electrically conductive material, for example, aluminum, tungsten, or preferably copper (particularly for cost reasons). Electrodes E1, E2, and E3 can each be made of a different material to optimize costs. Electrodes E1, E2, and E3 can be directly overmolded into the body 30 (to improve sealing).

[0031] The body 30 is preferably made of an electrically insulating material, for example plastic, or thermosetting polymer, for example polyamide PA6.6.

[0032] Electrodes E1, E2 and E3 are configured such that a free end of each electrode opens into the volume delimited by body 30.

[0033] The said free ends of each electrode E1, E2, E3 are arranged, within the internal volume defined by the body 30, at a distance from each other and opposite each other with respect to the other electrodes.

[0034] In the illustrated example, the body 30 has a rectangular shape. Electrodes E1, E2, and E3 open into the body 30 from different faces of the body 30.

[0035] In this example, electrode E1 is connected to terminal 8 by an electrical conductor 14. The end 29 of electrode E2 (or of any electrode connected to electrode E2) opens into the breaking chamber of the circuit breaker 4. The third electrode E3 is connected to one terminal of the fuse 12, the other terminal of the fuse being connected to terminal 6.

[0036] Other examples are possible. In practice, however, the electrical device 10 is connected in series with the fuse 12, the fuse and the electrical device being connected together in parallel with the circuit breaker 4 via the first electrode and the third electrode, the second electrode opening into a breaking chamber of the circuit breaker.

[0037] In general, device 10 is configured to: prohibit the flow of current between the first electrode E1 and the third electrode E3 when the electric current or electric voltage between the first electrode E1 and the second electrode E2 remains below a predefined threshold value; allow the flow of an electric current between the first electrode E1 and the third electrode E3 as soon as the electric current or electric voltage between the first and second electrodes exceeds a predefined threshold value.

[0038] In an example not forming part of the invention, the device 10 comprises an electrically conductive fusible element F1, such as a copper or silver wire, connecting the first electrode E1 to the second electrode E2, the fusible element being configured to melt when the current flowing through it exceeds said threshold value. The electrically conductive fusible element F1 may also be a ribbon, strip, or mat of cables or wires, or any other suitable connection structure, the electrically conductive fusible element F1 preferably being made of metal. For the fabrication of the fusible element, those skilled in the art may refer to the known prior art in the fabrication of fuses for electrical circuit protection.

[0039] In this case, device 10 is specifically configured for: allow the flow of an electric current between the first electrode E1 and the second electrode E2 as long as the current remains below a predefined threshold value (while preventing the flow of current between the first electrode E1 and the third electrode E3); when said current exceeds said threshold value, also allow the flow of current between the first electrode E1 and the third electrode E3, and possibly interrupt the flow of current between the first electrode E1 and the second electrode E2.

[0040] In other words, device 10 allows the electric current coming from the first electrode E1 to be diverted from the second electrode E2 to the third electrode E3, depending on the value of the intensity of the electric current.

[0041] Thus, when the energy released by the current flowing through F1 is less than the threshold value, the current flows from the first electrode E1 to the second electrode E2. When the energy released by the current flowing through F1 exceeds the threshold, the fusible element F1 melts. This leads to the formation of an electric arc A between the first electrode E1 and the second electrode E2. The arc A is then diverted to form between the first electrode E1 and the third electrode E3.

[0042] It is therefore understandable that the arrangement, dimensions, and spacing of electrodes E1, E2, E3, and their free ends are chosen accordingly. For example, the distance D1 separating E1 and E2 can be defined to be greater than the distance D2 separating E1 and E3, typically D1 greater than or equal to 1.2 times D2. This has the effect of favoring the deflection of arc A from E2 to E3.

[0043] For example, the first and third electrodes E1 and E3 have their respective terminal ends aligned with each other. The terminal end of the first electrode is curved here and has an L-shape.

[0044] For example, the tip of electrode E3 can be conical and pointed to promote the attraction of arc A.

[0045] In practice, the first electrode E1, the second electrode E2 and the third electrode E3 are spaced apart and separated by a volume of gas, such as air.

[0046] Optionally, the volume delimited by the body 30 may include one or more energy-absorbing elements 32, 34, such as metallic foam or a ball of stainless steel wire, or silica, or any suitable material, which help to cool the inside of the body 30 and attenuate the electric arc in the event of exceeding the current threshold.

[0047] Inserts (a) and (b) of the figure 2 illustrate two possible variants of device 10.

[0048] The insert (a) represents an alternative example 10a of the device 10 of the figure 1 .

[0049] Device 10a is broadly identical to device 10 and has a similar function, except that the terminal ends 40, 42 of electrodes E1 and E2, respectively, are curved and have an L-shape.

[0050] In addition, the free ends 40, 42 of the first electrode and the second electrode are partially separated by an electrically insulating barrier 44.

[0051] For example, the insulating barrier 44 is made of the same material as the body 30.

[0052] The fusible element F1 then has a U-shaped form. This makes it easier to deflect the electric arc towards the third electrode E3.

[0053] The insert (b) represents a second alternative example 10b of the device 10 of the figure 1 .

[0054] In this example, the fusible conductive element F1 is omitted and replaced by a gap (“air gap”), for example filled with air.

[0055] In this case, the threshold is an electrical voltage threshold. Dielectric breakdown in air between electrodes E1 and E2 is caused when the voltage generated by the electric arc A1 (described below) established between conductors 26 (connected to E1) and 28 (connected to E2) exceeds a threshold value.

[0056] In this example, the device is arranged so that the breakdown voltage between the first electrode and the second electrode E2 is less than the breakdown voltage between the first electrode E1 and the third electrode E3.

[0057] This characteristic can be achieved by adjusting the positioning of the second electrode E2 relative to electrodes E1 and E3. Another way to obtain this characteristic is to interpose a fusible wall (analogous to the fusible wall 62 described below) between the first electrode E1 and the second electrode E2, and / or between the second electrode E2 and the third electrode E3, the properties of these walls being chosen accordingly to melt above a specific voltage (and therefore energy) threshold. These solutions can also be combined.

[0058] According to one possible implementation, the body 50 of the device 10b has a tubular or cylindrical shape. The first electrode E1 and the third electrode E3 are aligned with each other and with the tubular body, opening onto opposite faces of the tubular body. The second electrode E2 opens into the body 50 through the cylindrical wall of the body, in an off-center (or asymmetrical) position relative to the first electrode E1 and the third electrode E3. In other words, the second electrode E2 is off-center (or asymmetrical) relative to the first electrode E1 and the third electrode E3. In this case, preferably, the distance between electrodes E1 and E3 is greater than 1.2 times the distance between electrodes E1 and E2.

[0059] For example, the end faces 52, 54 of the body 50 may have a conical or trapezoidal shape. Optionally, the inner wall of said faces may have electrically conductive studs.

[0060] For example, according to one variant, the fusible conductive element F1 can be replaced by a bimetallic strip, or more generally by an electrical conductor made of shape memory material, connecting the first electrode E1 to the second electrode E2.

[0061] The bimetallic strip is configured to deform and interrupt the electrical contact between the first electrode E1 and the second electrode E2 when the current passing through it exceeds said threshold value.

[0062] This then allows the current to flow from the first electrode E1 to the third electrode E3, for example by the formation of an electric arc, or by direct contact of the bimetallic strip with the third electrode E3.

[0063] It is thus understood that, in many possible examples, including the method of implementation of the figure 1 , the device 10 includes an electrically conductive element connecting the first electrode E1 to the second electrode E2, the electrically conductive element being configured to be modified when the current through it exceeds said threshold value.

[0064] For example, if the electrically conductive element is the fusible element F1, the modification consists of melting the fusible element F1. If the electrically conductive element is a deformable shape-memory material, such as a bimetallic strip, the modification consists of deformation.

[0065] Each of these examples can be implemented independently of the previous examples.

[0066] In this description, the operation of system 2 is described only with reference to the examples of device 10 based on the fusible conductor F1. However, it is understood that these explanations can be transposed to the other examples of device 10, in particular the alternative examples shown above.

[0067] In general, device 10, as well as its variants, can be used independently of electrical system 2.

[0068] An example of the operation of electrical system 2 is illustrated by means of the figures 3 , 4 And 5 .

[0069] There figure 3 represents a first state of system 2 immediately after the tripping of the circuit breaker 4. The internal conductor has been cut into portions 24, 26 and 28 by the cutting element 22. The electric current C1 from terminal 8 continues to flow through the circuit breaker, because electric arcs, noted A, have formed on the one hand between the conductor portions 24 and 26 and on the other hand between the conductor portions 26 and 28.

[0070] There figure 4 represents a second state of system 2 subsequent to the first state. The electric current C1 continues to flow through the circuit breaker 4 due to the presence of the electric arcs A1 and A2.

[0071] In parallel, since electrode E1 is connected to terminal 8, part of the electric current flows between the first electrode E1 and the second electrode E2, passing through the fusible conductor element F1. This current also flows between the second electrode E2 and the central conductor portion 28, due to the formation of another electric arc A3 between these two elements. Preferably, the arrangement of end 29 near conductor 28 favors the extinction of arc A1 in favor of arc A3.

[0072] The energy supplied by the electric current flowing through the fusible element F1 increases during the time it takes the circuit breaker to oppose the current flow, thanks to the voltage generated by the electric arcs A1 and A2, then A2 and A3. Depending on the value of the current C1 flowing through the circuit breaker 4 when it is tripped, two scenarios are possible: In the first case, if the energy supplied by the current flowing through the fusible element F1 is less than the melting energy of the fusible element, then the fusible element F1 does not melt. This means that the voltage generated by the electric arcs A1 and A2, then A2 and A3, was sufficient on its own to oppose the current flow and cancel it out. In this case, the current C1 is canceled while the fuse F1 is simply heated by Joule heating, but is not melted.The final electrical insulation is ensured in the circuit breaker by the distances between the free ends of the conductors, and in the device 10 by the distance in the air between the electrodes E1 and E3 (or the wall 62 if present).

[0073] In a second case, if the energy supplied by the passage of current in F1 exceeds the threshold of fusion energy (I 2< t) specific to the fusible conductive element F1, then this causes the fusible conductive element to melt and causes the appearance of an electric arc (not illustrated) between the first electrode E1 and the second electrode E2 in place of the fusible element F1.

[0074] There figure 5 represents a third state of system 2, subsequent to the second state. After the melting of the fusible conductive element F1, the electric arc A established between the first electrode E1 and the second electrode E2 is deflected to establish itself between the first electrode E1 and the third electrode E3 (electric arc A on the figure 5 ).

[0075] Indeed, the air surrounding the ends of the electrodes is ionized by the electric arc A. The electric arc A is attracted to the third electrode E3, which is at the same potential as terminal 6. The potential difference between the first electrode E1 and the second electrode E2 is less than the potential difference between the first electrode E1 and the third electrode E3.

[0076] The entire current C1 from terminal 8 is then diverted by device 10 and ceases to flow through the circuit breaker 4, causing the extinction of the electric arcs A2 and A3 in the circuit breaker 4.

[0077] Next, fuse 12 melts to interrupt the flow of electric current C1. The flow of current in electrical system 2 is then interrupted.

[0078] The final electrical insulation is ensured in the circuit breaker by the distances between the free ends of the conductors, and by the F2 fuse.

[0079] Since fuse 12 is not constantly subjected to the electric current flowing between terminals 6 and 8 of the circuit breaker 4 under normal conditions (fuse 12 is protected from this current by device 10), the service life of fuse 12 can be extended. This increases the reliability of electrical system 2.

[0080] Preferably, the characteristics of fuse 12 (in particular, current rating, breaking capacity and voltage rise profile) are chosen according to the cooling time of the ionized gases in the housing 30.

[0081] It is understood that in practice, device 10 is a passive device, that is to say that the deflection of the electric arc by device 10 does not require actuation of device 10 by an external action, such as a trigger or a manual control, unlike the circuit breaker 4 for example.

[0082] There figure 6 represents an embodiment 2a of the electrical system 2 of the figure 1 .

[0083] Electrical system 2b is broadly identical to system 2 and has a similar operation, except that the second electrode E2 is now connected to the central conductor portion 28, instead of opening freely into the breaking chamber.

[0084] In other words, the second electrode is connected to an internal electrical conductor (the central portion 28) of the circuit breaker 4, this internal conductor being coupled to at least one of the terminals 6, 8 of the circuit breaker 4.

[0085] The second electrode E2 can either be connected directly to the central portion 28, or be connected indirectly via a gap (air gap), for example by being placed at a distance of at least 0.1 mm from the central portion 28. This latter variant avoids in particular premature wear of the fusible element F1 by preventing the circulation in the fusible conductive element F1 of a weak current, derived from the current C1 when the circuit breaker is in the closed position (conducting state).

[0086] In one variant (not illustrated), the central portion 28 can be mobile or deformable over a stroke greater than or equal to the distance separating it from the electrode 29. In practice, the central portion 28 can be moved by the piston 22 until it comes into contact with the electrode 29.

[0087] In one variant (not shown), the electrode 29 opens into a space located between the central portion 28 and the piston 22, the piston 22 being positioned between the electrode 29 and the end 26. This facilitates the extinction of arc A1 and the formation of arc A3. The current C1 is thus completely diverted into the fusible conductive element F1.

[0088] In another variant, the central portion 28 is the only moving part inside the circuit breaker, with portions 24 and 26 remaining fixed. The central portion 28 can thus move until it contacts the electrode 29.

[0089] In preferred variants, as seen on the figure 6 , the second electrode E2 is connected to the internal electrical conductor (at the central portion 28) via an insulating element 60, such as a discharge tube suppressor (“ gas arrestor (in English). This element can also be a varistor (MOV) or any other element preventing the flow of a weak current.

[0090] Preferably, if the insulating element 60 is a voltage suppressor, its voltage threshold can be low, for example, on the order of 10 volts. This prevents the flow of electric current in the device 10 as long as no electric arc is present in the circuit breaker 4, while allowing current to flow in the fusible conductive element F1 very quickly after the circuit breaker trips and the electric arc A1 appears.

[0091] Alternatively, the insulating element 60 could be connected to a different location.

[0092] Alternatively, the insulating element 60 can also have a high voltage threshold, for example, close to the nominal voltage of the system being protected. This has the effect of delaying the flow of current through the fusible conductive element F1, in order to allow time for the electric arcs A1 and A2 to oppose the flow of current C1.

[0093] In one variant, the circuit breaker 4 consists of a series assembly of several circuit breakers, for example, two circuit breakers: the circuit breaker described previously, and an additional circuit breaker connected in series with said circuit breaker, the connection being made via the respective terminals 6 or 8 of the two circuit breakers. In this case, electrode E2 or electrode 29 does not open into the breaking chamber itself, but preferentially opens at the junction point between the two circuit breakers. In other words, the second electrode E2, 29 is connected to the junction between said circuit breakers.

[0094] According to the invention, within the volume delimited by the body 30 of the device 10, the free end of the third electrode E3 is separated from the free ends of the first electrode E1 and the second electrode E2 by a fusible wall 62, shown in dotted lines on the figure 6 .

[0095] For example, the fusible wall 62 is configured either to melt under the heat generated by the electric arc A3 or to rupture under the pressure inside the device 10. The fusible wall 62 can, for example, be made of plastic or any other electrically insulating material. The wall reduces the distance between electrodes E1 and E3 because its electrical insulating properties are greater than those of air. Once this wall ruptures, the arc forming between the first electrode E1 and the third electrode E3 is shorter, and therefore the energy it releases is reduced.

[0096] In practice, however, the device 10 described above (or any of its variants) can be used. Such a partition can also be used in all or some of the variants of device 10 described above.

[0097] Inserts (a) and (b) of the figure 7 illustrate two possible variants of encapsulating all or part of the elements of system 2 in a common body.

[0098] The insert (a) represents a first embodiment of a cartridge 70 in which the device 10 and the fuse 12 are integrated.

[0099] A tubular (or cylindrical) body 72 delimits a first region 74 (or compartment) corresponding to the fuse 12 and a second region 76 (or compartment) corresponding to the device 10.

[0100] Preferably, the tubular body 72 is made of electrically insulating material, for example plastic, or ceramic, or a composite material comprising glass fibers embedded in a resin matrix, or any suitable material.

[0101] The first region 74 and the second region 76 are separated by an electrically conductive wall, so as to bring components present in these two regions into contact. Advantageously, the terminal ends of the body 72 have caps 78, which may be metal caps crimped onto the tubular body 72.

[0102] For example, the first region 74 includes one or more fusible blades F2 immersed in a siliceous material, such as sand.

[0103] The second region 76 includes electrodes E1 and E2 (opening outside the cap 78) and electrode E3 (for example, integrated within a metallic contact piece which here forms the partition separating regions 74 and 76, to ensure an electrical connection with the fusible blades F2). If applicable, the second region also includes the fusible conductive element F1.

[0104] Preferably, the second region 76 comprises an electrically insulating body, for example formed of plastic, which covers the internal walls of the second region 76 and which serves to hold the electrodes E1 and E2 in position.

[0105] Optionally, region 76 includes absorbing elements 32, 34 and, where applicable, voltage suppressor element 60.

[0106] Depending on whether the voltage suppressor element 60 is present or not, the fusible conductive element F1 connects the first electrode E1 to the voltage suppressor element 60 or directly to the second electrode E2.

[0107] The insert (b) of the figure 7 represents a cartridge 80 in which at least some of the components of the device 10 are integrated. This embodiment is particularly applicable to the embodiment of the electrical system 2b illustrated in the figure 8 .

[0108] This system differs in particular from other 2a systems in that the device 10 is made in the form of an assembly 90 in which the fuse element F1 is associated with a second circuit breaker 92 comprising a pyrotechnic charge 94, a moving contact 96 and connection terminals 98.

[0109] One of the terminals 98 is connected to fuse 12, while the other terminal 98 is connected to a first electrode 100A, which is connected to terminal 8. A second electrode 100B connects the fuse element F1 to the central portion 28 via the voltage suppressor element 60 and a third electrode 100C. Alternatively, it is possible to omit the voltage suppressor element; in this case, electrode 100C is connected directly to electrode 100B.

[0110] The pyrotechnic charge 94 is connected to electrode 100B and electrode 100A, so that it is triggered when the fusible element F1 has melted. This system diverts the current arriving from terminal 8 of the circuit breaker 4 to fuse 12.

[0111] This solution allows for the interruption of very high intensity currents (no arc A, no energy dissipated in the device 10).

[0112] On the insert (b) of the figure 7 The cartridge 80 comprises a tubular or cylindrical body 82 which delimits a region 84 comprising a fusible blade F1 immersed in a silica material, such as sand, and extending between the electrodes 100A and 100B. Preferably, the tubular body 82 is made of an electrically insulating material, for example plastic, or ceramic, or a composite material comprising glass fibers embedded in a resin matrix, or any suitable material.

[0113] Advantageously, the terminal ends of the body 82 have caps 86. The electrode 100A is disposed at one end of the body 82, while the electrodes 100B and 100C are disposed at the other end of the body 82. Preferably, the inside of the tubular body 82 has, on the end which carries the electrodes 100B and 100C, an electrically insulating body which serves to hold the electrodes 100C and 100B in position.

[0114] However, other examples are possible.

[0115] In some systems not part of the invention and not illustrated, the device 10 can be integrated inside the circuit breaker 4. For example, the electrodes E1 and E2 are arranged in the breaking member 22, emerging from the breaking member 22, the latter being electrically conductive, while the electrode E3 is arranged in the body 20 of the circuit breaker 4, so as to be opposite and aligned with the electrode E1 when the breaking member 22 is in the deployed position.

[0116] Thanks to the invention, fuse 12 is only connected in parallel with circuit breaker 4 when the circuit breaker 4 is tripped and only if the energy flowing through the circuit breaker has exceeded a threshold value. This prevents fuse 12 from being continuously subjected to an electric current, as this could lead to premature aging of the fuse. The invention also ensures rapid opening of the circuit even when the current flowing through it at the time of tripping is low or zero.

[0117] Compared to other technical solutions, the threshold value determined by the rating of the F1 fusible element offers numerous practical advantages and ease of industrial production. In particular, the threshold value is easy to adjust during product development and can be readily controlled during high-volume production. Furthermore, this threshold value is stable over time, exhibiting low sensitivity to aging (unlike a plastic membrane, for example) and being insensitive to ambient pressure. In addition, the threshold value tends to be relatively independent of the installation's inductance.

Claims

1. An electrical system (2) for interrupting an electrical current, including a circuit breaker (4), a fuse (12) and an electrical device (10, 10b), the electrical device (10b) including a body (30) delimiting a closed internal volume, a first electrode (E1), a second electrode (E2) and a third electrode (E3), a free end of each electrode opening into the internal volume, said free ends of each electrode being arranged inside the internal volume, at a distance from each other and opposite with respect to the other electrodes, wherein the first electrode (E1), the second electrode (E2) and the third electrode (E3) are spaced apart and separated by a volume of gas, such as air, the breakdown voltage between the second electrode (E2) and the first electrode (E1) being lower than the breakdown voltage between the second electrode (E2) and the third electrode (E3), wherein within the volume, the free end of the third electrode (E3) is separated by a fuse wall (62) from the free ends of the first electrode (E1) and of the second electrode (E2), the electrical device being configured for: - prohibiting the flow of current between the first electrode and the third electrode when the electric current or the electric voltage between the first electrode (E1) and the second electrode (E2) stays below a predefined threshold value; - letting the current flow between the first electrode and the third electrode when said electric current or said electric voltage exceeds said threshold value, wherein: - the electrical device being connected in series with the fuse (12), the fuse and the electrical device being connected together in parallel with the circuit breaker (4) by means of the first electrode (E1) and of the third electrode (E3), the second electrode (E2) opening into a breaking chamber of the circuit breaker (4), - current flow is made through an electric arc (A), initially established between the first electrode (E1) and the second electrode (E2), said arc (A) being then diverted to be established between the first electrode (E1) and the third electrode (E3).

2. The electrical system (2) according to claim 1, wherein the second electrode (E2) is connected to an internal electrical conductor (28) of the circuit breaker (4) before or after actuating the circuit breaker, the internal conductor being coupled to at least one of the terminals (6, 8) of the circuit breaker (4).

3. The electrical system (2) according to claim 2, wherein the second electrode (E2) is connected to the internal electrical conductor (28) through an insulating member such as a voltage suppressor element (60) or a varistor.

4. The electrical system (2) according to claim 1, wherein the system includes an additional circuit breaker connected in series with said circuit breaker (4) by the respective terminals (6, 8) thereof, the second electrode (E2, 29) being connected at the junction between said circuit breakers.

5. The electrical system according to claim 1, wherein the second electrode (E2, 29) is arranged in the breaking chamber opposite to and at a distance from one of the terminals (6, 8) of the circuit breaker (4).

6. The electrical system (2) according to any one of claims 1 to 4, wherein the fuse (12) and the electrical device (10;10b) are integrated within the same body (70).

7. The electrical system (2) according to any one of claims 1 to 4, wherein the circuit breaker (4) and the electrical device (10; 10b) are integrated within the same body.

8. The electrical system (2) according to any one of claims 1 to 6, wherein the circuit breaker (4) is a pyrotechnic circuit breaker.

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