Electrical apparatus, electrical cut-off system comprising such an apparatus

Abstract

Electrical apparatus (10) comprising a body (30) delimiting a closed interior volume, a first electrode (E1), a second electrode (E2) and a third electrode (E3), a free end of each electrode opening into the interior volume, said free ends of each electrode being arranged, inside the interior volume, at a distance from each other and facing each other with respect to the other electrodes, the electrical apparatus being configured to: - prohibit the flow of current between the first electrode and the third electrode when the electric current or the electric voltage between the first electrode and the second electrode remains below a predefined threshold value; - when said electric current or said electric voltage exceeds said threshold value, authorize the flow of current between the first electrode and the third electrode.

Description

[0001] The invention relates to an electrical apparatus 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 fuse blade placed in a housing filled with a material such as silica. The blade is configured to melt when the current flowing through the fuse exceeds a predetermined value for a certain period of time.

[0005] Some contemporary applications today require the ability to interrupt a high-intensity electrical current with a very rapid response time. This is the case, for example, in 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 the cutting 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 trigger 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 re-formation of an electric arc in the pyrotechnic circuit breaker.

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

[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 permanently crossed 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 low or even (temporarily) zero intensity, which may however 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, which can however be complicated to achieve industrially.

[0013] There is therefore a need for an electrical cut-off device that overcomes the above drawbacks.

[0014] In general, the invention relates to an electrical device comprising a body delimiting a closed interior volume, a first electrode, a second electrode and a third electrode, a free end of each electrode opening into the interior of the interior volume, said free ends of each electrode being arranged, inside the interior volume, at a distance from each other and facing each other with respect to the other electrodes, the electrical device being configured to: 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 and the second electrode remains below a predefined threshold value; when said electric current or said electric voltage exceeds said threshold value, authorizing the flow of current between the first electrode and the third electrode.

[0015] In particular, the invention relates to an electrical apparatus as defined in claim 1.

[0016] According to advantageous but not mandatory aspects, such an apparatus may incorporate one or more of the features defined in the dependent claims, as defined below, the features being taken in isolation or in any technically admissible combination: the apparatus comprises an electrically conductive element connecting the first electrode to the second electrode, the fusible element being configured to change when the current passing through it exceeds said threshold value; the apparatus comprises an electrically conductive fusible element, such as a wire, connecting the first electrode to the second electrode, the fusible element being configured to melt when the current passing through it exceeds said threshold value; the apparatus comprises a deformable conductive element with shape memory connecting the first electrode to the second electrode, the conductive element being configured to deform and interrupt the electrical contact between the first electrode and the second electrode when the current passing through it exceeds said threshold value; the free ends of the first electrode and the second electrode are partially separated by an electrically insulating barrier;inside the volume, the free end of the third electrode is separated from the free ends of the first electrode and the second electrode by a fusible wall; the first electrode, the second electrode and the third electrode are spaced from each other and separated by a volume of gas, such as air, the electrical breakdown voltage between the second electrode and the first electrode being lower than the electrical breakdown voltage between the second electrode and the third electrode. ; the second electrode is off-center with respect to the first electrode and the third electrode; the body has a tubular shape, the first electrode and the third electrode being aligned with each other and opening onto opposite faces of the tubular body, the second electrode opening into the body through the cylindrical wall of the body, off-center with respect to the first electrode and the third electrode. ;

[0017] According to another aspect, the invention relates to an electrical system for interrupting an electric current, comprising a circuit breaker, a fuse and an electrical apparatus according to any one of the preceding claims, the electrical apparatus being connected in series with the fuse, the fuse and the electrical apparatus being connected together in parallel with the circuit breaker via the first electrode and the third electrode, the second electrode opening into an extinguishing chamber of the circuit breaker.

[0018] According to advantageous but not mandatory aspects, such an electrical system may incorporate one or more of the following characteristics, taken in isolation or in any technically admissible combination: the second electrode is connected to an internal electrical conductor of the circuit breaker before or after actuation of the circuit breaker, this internal conductor being coupled to at least one of the terminals of the circuit breaker; the second electrode is connected to the internal electrical conductor via an insulating element such as a voltage suppressor element or a varistor; the system comprises an additional circuit breaker connected in series with said circuit breaker by their respective terminals, the second electrode being connected to the junction between said circuit breakers; the second electrode is arranged, in the breaking chamber, opposite and at a distance from one of the terminals of the circuit breaker; the fuse and the electrical device are integrated within the same body; the circuit breaker and the electrical device are integrated within the same body; the circuit breaker is a pyrotechnic circuit breaker.

[0019] The invention will be better understood and other advantages thereof will appear more clearly in the light of the following description of an embodiment of an apparatus for cutting an electric current given solely by way of example and with reference to the appended drawings, in which: [ Fig 1 ] there figure 1 schematically represents an apparatus for interrupting an electric current comprising an electrical breaking element in accordance with embodiments of the invention; [ Fig 2 ] there figure 2 schematically represents two alternative embodiments of the electrical cut-off element of the device of the figure 1 ; [ Fig 3 ] there figure 3 schematically represents a first operating state of the device of the figure 1 ; [ Fig 4 ] there figure 4 schematically represents a second operating state of the device of the figure 1 ; [ Fig 5 ] there figure 5 schematically represents a third operating state of the device of the figure 1 ; [ Fig 6 ] there figure 6 schematically represents another embodiment of the apparatus of the figure 1 ; [ Fig 7 ] there figure 7 schematically represents two examples of construction of an electrical cut-off element, respectively for the cut-off device of the figures 1 And 6 (insert a) and for the cut-off device of the figure 8 (insert b); [ Fig 8 ] there figure 8 schematically represents another embodiment of the apparatus of the figure 1 .

[0020] There figure 1 represents an embodiment of an electrical system 2 configured to interrupt an electric current, for example in order to protect an electrical load or an electrical installation.

[0021] The device 2 comprises 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.

[0022] The apparatus 2 also comprises an electrical apparatus 10 and a fuse 12 electrically connected in parallel with the circuit breaker 4 between terminals 6 and 8.

[0023] For example, fuse 12 is a fuse cartridge comprising one or more F2 fuse blades.

[0024] Generally, the circuit breaker 4 can be switched from an electrically conductive state to an electrically blocking (or open) state.

[0025] The circuit breaker 4 may be a pyrotechnic circuit breaker. For example, the circuit breaker 4 may include an explosive charge configured to, when triggered, physically sever an electrical conductor extending between the terminals 8 and 6 of the circuit breaker 4.

[0026] In the illustrated example, the circuit breaker 4 comprises a body 20 and a cut-off member 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).

[0027] The cutting member 22 is configured to cut an internal electrical conductor housed inside the body 20, this electrical conductor connecting the terminal 6 to the terminal 8.

[0028] On the figure 1 , the circuit breaker 4 is illustrated in a triggered position. The electrical conductor, cut by the cut-off member 22, is divided between 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.

[0029] An electrode 29, the role of which 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 other of the portions 24 or 26.

[0030] The electrode 29 can be made of any conductive material, for example aluminum, tungsten, or preferably copper (in particular for cost reasons). The electrode 29 can be overmolded directly into the body 20 (to improve sealing).

[0031] According to alternative embodiments, the circuit breaker 4 may be a fuse cartridge, or an electromechanical device, such as for example an electromagnetic contactor, or a semiconductor switch, or any other suitable device.

[0032] The electrical device 10 comprises a body 30 delimiting a closed interior volume, a first electrode E1, a second electrode E2 and a third electrode E3.

[0033] The electrodes E1, E2, E3 can be made of any electrically conductive material, for example aluminum, tungsten, or preferably copper (in particular for cost reasons). The electrodes E1, E2, E3 can each be made of a different material to optimize costs. The electrodes E1, E2, E3 can be overmolded directly into the body 30 (to improve sealing).

[0034] The body 30 is preferably made of an electrically insulating material, for example plastic, or thermoset polymer, for example polyamide PA6.6.

[0035] The electrodes E1, E2 and E3 are configured such that a free end of each electrode opens inside the volume delimited by the body 30.

[0036] Said free ends of each electrode E1, E2, E3 are arranged, inside the interior volume defined by the body 30, at a distance from each other and opposite the other electrodes.

[0037] In the illustrated example, the body 30 has a block shape. The electrodes E1, E2 and E3 open into the body 30 via different faces of the body 30.

[0038] 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 circuit breaker 4. The third electrode E3 is connected to one terminal of fuse 12, the other terminal of the fuse being connected to terminal 6.

[0039] Other examples are possible. In practice, however, the electrical apparatus 10 is connected in series with the fuse 12, the fuse and the electrical apparatus being connected together in parallel with the circuit breaker 4 via the first electrode and the third electrode, the second electrode opening into an extinguishing chamber of the circuit breaker.

[0040] Generally, the device 10 is configured to: prohibiting the flow of current between the first electrode E1 and the third electrode E3 when the electric current or the electric voltage between the first electrode E1 and the second electrode E2 remains below a predefined threshold value; authorizing the flow of an electric current between the first electrode E1 and the third electrode E3 as soon as the electric current or the electric voltage between the first electrode and the second electrode exceeds a predefined threshold value.

[0041] In a preferred embodiment, the apparatus 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 passing through it exceeds said threshold value. The electrically conductive fusible element F1 may also be a ribbon, or a strip, or a sheet of cables or wires, or any other suitable connection structure, the electrically conductive fusible element F1 preferably being made of metal. To produce the fusible element, a person skilled in the art may refer to the known state of the art in the production of electrical circuit protection fuses.

[0042] In this case, the device 10 is more particularly configured to: allowing 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 allowing the flow of current between the first electrode E1 and the third electrode E3, and possibly interrupting the flow of current between the first electrode E1 and the second electrode E2.

[0043] In other words, the device 10 makes it possible to divert the electric current coming from the first electrode E1 to send it from the second electrode E2, to the third electrode E3, depending on the intensity value of the electric current.

[0044] Thus, when the energy released by the current flowing in F1 is lower 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 in F1 exceeds the threshold, the fusible element F1 melts. This leads to the appearance of an electric arc A between the first electrode E1 and the second electrode E2. The arc A is then deflected to establish itself between the first electrode E1 and the third electrode E3.

[0045] It is therefore understood that the arrangement, dimensioning and spacing of the electrodes E1, E2, E3 and their free ends is 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 promoting the deflection of the arc A from E2 to E3.

[0046] 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 here curved and has an L shape.

[0047] For example, the end of electrode E3 can be conical and pointed in order to promote the attraction of arc A.

[0048] In practice, the first electrode E1, the second electrode E2 and the third electrode E3 are spaced from each other and separated by a volume of gas, such as air.

[0049] Optionally, the volume delimited by the body 30 may comprise one or more energy-absorbing elements 32, 34, such as a metal foam or a ball of stainless steel wire, or silica, or any suitable material, which contribute to cooling the interior of the body 30 and attenuating the electric arc in the event of the current threshold being exceeded.

[0050] Inserts (a) and (b) of the figure 2 illustrate two possible variants of the device 10.

[0051] Insert (a) represents a first alternative embodiment 10a of the apparatus 10 of the figure 1 .

[0052] The apparatus 10a is generally identical to the apparatus 10 and has a similar operation, except that the terminal ends 40, 42 of the electrodes E1 and E2, respectively, are curved and have an L-shape.

[0053] Furthermore, the free ends 40, 42 of the first electrode and the second electrode are partially separated by an electrically insulating barrier 44.

[0054] For example, the insulating barrier 44 is made of the same material as the body 30.

[0055] The fuse element F1 then has a U shape. This facilitates the deflection of the electric arc towards the third electrode E3.

[0056] Insert (b) represents a second alternative embodiment 10b of the apparatus 10 of the figure 1 .

[0057] In this embodiment, the fusible conductive element F1 is omitted and replaced by a spacer (“air gap” in English), for example filled with air.

[0058] In this case, the threshold is an electrical voltage threshold. Dielectric breakdown in the 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.

[0059] In this embodiment, the apparatus is arranged such that the breakdown voltage between the first electrode and the second electrode E2 is lower than the breakdown voltage between the first electrode E1 and the third electrode E3.

[0060] This characteristic can be obtained by varying the positioning of the second electrode E2 relative to the 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 from a specific voltage (and therefore energy) threshold. These solutions can also be combined.

[0061] According to a 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 and open 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) manner 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 the electrodes E1 and E3 is greater than 1.2 times the distance between the electrodes E1 and E2.

[0062] For example, the end faces 52, 54 of the body 50 may have a conical or trapezoidal shape. Optionally, the internal wall of said faces may comprise electrically conductive pads.

[0063] Other embodiments, not illustrated, are nevertheless possible.

[0064] For example, according to a 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.

[0065] 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.

[0066] This then allows the current to flow from the first electrode E1 to the third electrode E3, for example by forming an electric arc, or by bringing the bimetallic strip into direct contact with the third electrode E3.

[0067] It is thus understood that, in many possible embodiments, including the embodiment of the figure 1 , the apparatus 10 comprises 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 passing through it exceeds said threshold value.

[0068] For example, in the case where the electrically conductive element is the fusible element F1, said modification consists of a melting of the fusible element F1. In the case where the electrically conductive element is a deformable shape memory material, such as a bimetallic strip, the modification consists of a deformation.

[0069] Each of these embodiments may be implemented independently of the previous embodiments.

[0070] In this description, the operation of the system 2 is described only with reference to the embodiments of the apparatus 10 based on the fusible conductor F1. However, it is understood that these explanations can be transposed to the other embodiments of the apparatus 10, in particular to the alternative embodiments set out above.

[0071] Generally, the apparatus 10, as well as its variants, can be used independently of the electrical system 2.

[0072] An example of the operation of the electrical system 2 is illustrated by means of the figures 3 , 4 And 5 .

[0073] There figure 3 represents a first state of the system 2 immediately after the circuit breaker 4 has been triggered. The internal conductor has been cut into portions 24, 26 and 28 by the cut-off member 22. The electric current C1 coming from the terminal 8 continues to flow through the circuit breaker, because electric arcs, denoted 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.

[0074] 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.

[0075] In parallel, as the electrode E1 is connected to the terminal 8, a portion of the electric current flows between the first electrode E1 and the second electrode E2, passing through the fusible conductive element F1. This current also flows between the second electrode E2 and the central conductor portion 28, due to the appearance of another electric arc A3 between these two elements. Preferably, the arrangement of the end 29 near the conductor 28 promotes the extinction of the arc A1 in favor of the arc A3.

[0076] The energy supplied by the electric current flowing in the fusible conductive element F1 increases during the time taken by the circuit breaker to oppose the passage of current, this thanks to the voltage generated by the electric arcs A1 and A2 then A2 and A3. Depending on the value of current C1 flowing in the circuit breaker 4 when it is triggered, two scenarios are possible:

[0077] In the first case, if the energy supplied by the current flow in the fusible conductive element F1 is less than the melting energy of the fusible conductive element, then the fusible conductive element F1 does not melt. This means that the voltage generated by the electric arcs A1 and A2 then A2 and A3 was sufficient in itself to oppose the flow of current and to cancel it. In this case, the current C1 is canceled while the fuse F1 is simply heated by the Joule effect, 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).

[0078] In a second case, if the energy provided by the passage of current in F1 exceeds the fusion energy threshold (I 2 < t) specific to the fusible conductive element F1, then this causes the fusion of the fusible conductive element and results in the appearance of an electric arc (not shown) between the first electrode E1 and the second electrode E2 in place of the fusible element F1.

[0079] 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 ).

[0080] In fact, the air surrounding the ends of the electrodes is ionized by the electric arc A. The electric arc A is attracted by 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.

[0081] All of the current C1 from terminal 8 is then diverted by the device 10 and ceases to flow through the circuit breaker 4, causing the electric arcs A2 and A3 to extinguish in the circuit breaker 4.

[0082] Then, fuse 12 blows to interrupt the flow of electric current C1. The flow of current in electrical system 2 is then interrupted.

[0083] The final electrical insulation is ensured in the circuit breaker by the distances between the free ends of the conductors, and by the fuse F2.

[0084] Since the fuse 12 is not permanently crossed by the electric current flowing between the terminals 6 and 8 of the circuit breaker 4 under normal circumstances (the fuse 12 is protected from this current by the device 10), then the service life of the fuse 12 can be extended. This increases the reliability of the electrical system 2.

[0085] Preferably, the characteristics of the fuse 12 (in particular, the current rating, the breaking capacity and the voltage rise profile) are chosen as a function of the cooling time of the ionized gases in the housing 30.

[0086] It is understood that in practice, the device 10 is a passive device, that is to say that the deflection of the electric arc by the device 10 does not require actuation of the device 10 by an external action, such as a trigger or a manual control, unlike the circuit breaker 4 for example.

[0087] There figure 6 represents a first alternative embodiment 2a of the electrical system 2 of the figure 1 .

[0088] The electrical system 2b is generally identical to the 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 extinguishing chamber.

[0089] 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.

[0090] The second electrode E2 can either be connected directly to the central portion 28, or be connected indirectly via a spacer (air gap), for example by being placed at a distance of at least 0.1 mm from the central portion 28. This latter variant in particular avoids premature wear of the fusible element F1 by preventing the circulation in the conductive fusible element F1 of a weak current, derived from the current C1 when the circuit breaker is in the closed position (on state).

[0091] In a variant (not illustrated), the central portion 28 can be movable or deformable over a travel greater than or equal to the distance which separates 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.

[0092] In a 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. Thus, this facilitates the extinction of the arc A1 and the appearance of the arc A3. The current C1 is thus diverted completely into the fusible conductive element F1.

[0093] In another variant, the central portion 28 is the only moving part inside the circuit breaker, the portions 24 and 26 remaining fixed. The central portion 28 can thus move until it comes into contact with the electrode 29.

[0094] 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.

[0095] Preferably, if the insulating element 60 is a voltage suppressor element, its voltage threshold may be low, for example of the order of 10 Volts. This makes it possible to prevent the passage of electric current in the device 10 as long as no electric arc is present in the circuit breaker 4, while allowing the current to pass into the conductive fusible element F1 very quickly after the circuit breaker has been triggered and the electric arc A1 has appeared.

[0096] Alternatively, the insulating element 60 could be connected at a different location.

[0097] Still as a variant, the insulating element 60 may also have a high voltage threshold, for example close to the nominal voltage of the system to be protected. This has the effect of delaying the flow of current in the fusible conductive element F1, in order to allow time for the electric arcs A1 and A2 to oppose the flow of current C1.

[0098] In a variant, the circuit breaker 4 is composed of a series assembly of several circuit breakers, for example two circuit breakers: the circuit breaker described above, and an additional circuit breaker connected in series with said circuit breaker, the connection being made by the respective terminals 6 or 8 of the two circuit breakers. In this case, the electrode E2 or the electrode 29 does not open into the breaking chamber strictly speaking, but preferentially opens at the junction point between the two circuit breakers. In other words, the second electrode E2, 29 being connected to the junction between said circuit breakers.

[0099] In optional variants, inside 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 .

[0100] For example, the fusible wall 62 is configured, for example, to melt under the effect of the temperature released by the electric arc A3 or to rupture under the effect of the pressure inside the device 10. The fusible wall 62 may, for example, be made of plastic or any other electrically insulating material. The wall makes it possible to reduce the distance between the electrodes E1 and E3, because its electrical insulating power is greater than that of air. Once this wall is broken, the arc forming between the first electrode E1 and the third electrode E3 is of reduced length, therefore the energy it releases is reduced.

[0101] In practice, however, the apparatus 10 previously described (or any of its variants) may be used. Such a wall may also be used in all or part of the variants of the apparatus 10 previously described.

[0102] Inserts (a) and (b) of the figure 7 illustrate two possible variants of encapsulation of all or part of the elements of system 2 in a common body.

[0103] The insert (a) represents a first embodiment of a cartridge 70 in which the device 10 and the fuse 12 are integrated.

[0104] 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.

[0105] 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.

[0106] 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 comprise caps 78, which may be metal caps crimped onto the tubular body 72.

[0107] For example, the first region 74 comprises one or more fuse blades F2 immersed in a silica material, such as sand.

[0108] The second region 76 comprises the electrodes E1 and E2 (opening outside the cap 78) the electrode E3 (for example integrated within a metal contact part which here forms the wall separating the regions 74 and 76, to ensure an electrical connection with the fuse blades F2). Where appropriate, the second region also comprises the fusible conductive element F1.

[0109] Preferably, the second region 76 comprises an electrically insulating body, for example formed from plastic, which covers the internal walls of the second region 76 and which serves to hold the electrodes E1 and E2 in position.

[0110] Optionally, region 76 comprises the absorbing elements 32, 34 as well as, where appropriate, the voltage suppressor element 60.

[0111] 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.

[0112] Insert (b) of the figure 7 represents a second embodiment of a cartridge 80 in which at least some of the components of the device 10 are integrated. This embodiment is especially applicable to the embodiment of the electrical system 2b illustrated in the figure 8 .

[0113] This embodiment differs in particular from the other embodiments of the system 2a in that the device 10 is produced 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 movable contact 96 and connection terminals 98.

[0114] One of the terminals 98 is connected to the fuse 12 while the other terminal 98 is connected to a first electrode 100A connected to the 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 not to use a voltage suppressor element, in this case the electrode 100C is connected directly to the electrode 100B.

[0115] The pyrotechnic charge 94 is connected to the electrode 100B and the electrode 100A, so as to be triggered when the fuse element F1 has melted. Thus, the system allows the current arriving from the terminal 8 of the circuit breaker 4 to be diverted to the fuse 12.

[0116] This solution makes it possible to interrupt very high intensity currents (no arc A, no energy dissipated in the device 10).

[0117] 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 fuse blade F1 immersed in a siliceous material, such as sand, and extending between the electrodes 100A and 100B. Preferably, the tubular body 82 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.

[0118] Advantageously, the terminal ends of the body 82 comprise caps 86. The electrode 100A is arranged at one end of the body 82, while the electrodes 100B and 100C are arranged at the other end of the body 82. Preferably, the interior of the tubular body 82 comprises, 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.

[0119] Other examples are possible, however.

[0120] In certain embodiments, not illustrated, the apparatus 10 can be integrated inside the circuit breaker 4. For example, the electrodes E1 and E2 are arranged in the cut-off member 22, emerging from the cut-off 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 cut-off member 22 is in the deployed position.

[0121] By virtue of the invention, the fuse 12 is only connected in parallel with the circuit breaker 4 when the circuit breaker 4 is triggered and only on condition that the energy passing through the circuit breaker has exceeded a threshold value, this to prevent the fuse 12 from being permanently crossed by an electric current, since this could lead to premature aging of the fuse. The invention also makes it possible to guarantee rapid opening of the circuit even when the current passing through it when it is triggered is low or zero.

[0122] Compared to other technical solutions, the threshold value determined by the fuse element rating F1 has many advantages in practical terms and in terms of ease of industrial production. In particular, the threshold value is easy to adjust during product development and can be easily controlled during large-scale production. This threshold value is also stable over time, being relatively insensitive to aging (unlike a plastic membrane, for example) and insensitive to ambient pressure. In addition, the threshold value tends to be relatively independent of the inductance value of the installation.

[0123] Any feature of one of the embodiments or variations described above may be implemented in the other embodiments and variations described.

Claims

1. Electrical apparatus (10b) comprising a body (30) delimiting a closed interior volume, a first electrode (E1), a second electrode (E2) and a third electrode (E3), a free end of each electrode opening into the interior volume, said free ends of each electrode being arranged, inside the interior volume, at a distance from each other and facing each other with respect to the other electrodes, in which the first electrode (E1), the second electrode (E2) and the third electrode (E3) are spaced from each other and separated by a volume of gas, such as air, an electrical breakdown voltage between the second electrode (E2) and the first electrode (E1) being lower than an electrical breakdown voltage between the second electrode (E2) and the third electrode (E3),the electrical apparatus being configured to: - prohibit the flow of current between the first electrode and the third electrode when the electrical voltage between the first electrode (E1) and the second electrode (E2) remains below a predefined threshold value, the threshold value being equal to the breakdown electrical voltage between the first electrode (E1) and the second electrode (E2); - when said electrical voltage exceeds said threshold value, authorize the flow of current between the first electrode and the third electrode, in which the flow takes place in the form of an electric arc previously established between the first electrode (E1) and the second electrode (E2), this arc then being diverted to establish itself between the first electrode (E1) and the third electrode (E3)., 2. Electrical apparatus (10b) according to claim 1, wherein, inside the volume, 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).

3. Electrical apparatus (10b) according to claim 1, wherein the second electrode (E2) is off-center relative to the first electrode (E1) and the third electrode (E3).

4. Electrical apparatus (10b) according to claim 3, in which the body (50) has a tubular shape with a cylindrical wall, the first electrode (E1) and the third electrode (E3) being aligned with each other and opening onto opposite faces of the body (50), the second electrode (E2) opening into the body (50) through the cylindrical wall, off-center relative to the first electrode (E1) and the third electrode (E3).

5. Electrical system (2) for interrupting an electric current, comprising a circuit breaker (4), a fuse (12) and an electrical apparatus (10, 10b) according to any one of the preceding claims, the electrical apparatus being connected in series with the fuse (12), the fuse and the electrical apparatus being connected together in parallel with the circuit breaker (4) via the first electrode (E1) and the third electrode (E3), the second electrode (E2) opening into a breaking chamber of the circuit breaker (4).

6. Electrical system (2) according to claim 5, wherein the second electrode (E2) is connected to an internal electrical conductor (28) of the circuit breaker (4) before or after actuation of the circuit breaker, this internal conductor being coupled to at least one of the terminals (6, 8) of the circuit breaker (4).

7. Electrical system (2) according to claim 6, wherein the second electrode (E2) is connected to the internal electrical conductor (28) via an insulating element such as a voltage suppressor element (60) or a varistor.

8. Electrical system (2) according to claim 5, wherein the electrical system comprises an additional circuit breaker connected in series with said circuit breaker (4) by their respective terminals (6, 8), the second electrode (E2, 29) being connected to the junction between said circuit breakers.

9. Electrical system according to claim 5, in which the second electrode (E2, 29) is arranged, in the cut-off chamber, opposite and at a distance from one of the terminals (6, 8) of the circuit breaker (4).

10. Electrical system (2) according to any one of claims 5 to 8, in which the fuse (12) and the electrical device (10; 10b) are integrated within the same body (70).

11. Electrical system (2) according to any one of claims 5 to 8, in which the circuit breaker (4) and the electrical device (10; 10b) are integrated within the same body.

12. Electrical system (2) according to any one of claims 5 to 10, in which the circuit breaker (4) is a pyrotechnic circuit breaker.

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