Trip device and short-circuit protection system

Abstract

One aspect of the invention relates to a trip device (9) which trips when an electric current flowing in a conductive line (2) reaches a current threshold, the device comprising: - a magnetic armature (20) and a magnetic flap (21) suitable for surrounding a portion of the conductive line (2), the magnetic flap (21) being movable between an open position and a closed position; - a holding mechanism (35) configured to deform when a force (Fmag) applied to the magnetic flap (21) reaches a force threshold; and - an electrical switch (12) that is conductive when the magnetic flap (21) is in the closed position.

Description

DESCRIPTION TITLE: TRIGGER DEVICE AND SHORT CIRCUIT PROTECTION SYSTEM TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of short-circuit protection devices more particularly applied to high direct voltages, for example to protect a power supply line in an electrically powered aircraft. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0002] A short circuit in an aircraft electrical system can cause serious incidents, which is why short circuit protection systems are essential to ensure passenger safety.

[0003] A known protection system includes a fuse sized for a high-intensity short-circuit current. More precisely, the fuse is sized to withstand high-intensity currents over a sufficiently long time. The fuse is intended to open the circuit by melting one or more of its elements when a current exceeding a threshold intensity passes through it, capable of melting it.

[0004] However, a fuse cannot be ordered for intermediate currents. Furthermore, it is not testable in operation.

[0005] Application FR 3 129 027 discloses a protection system for achieving a brief circuit break, for example less than 5 ms. The system comprises, for example, a pyrotechnic actuator configured to apply a tensile force to the fuse and facilitate or accelerate its breaking.

[0006] The actuator, however, must be controlled by a trigger device. The latter may implement probes remote from the main trigger circuit and thus introduce new failure modes. For example, magnetic fields induced by high currents flowing in the circuit can induce a current in the measuring wires and lead to spurious detections. Temperature and / or pressure variations in an aircraft may also have an impact on the robustness of short-circuit detection.

[0007] Therefore, neither of the two aforementioned solutions can guarantee good reliability of protection against a short circuit. SUMMARY OF THE INVENTION

[0008] The invention makes it possible to solve at least part of the aforementioned problems.

[0009] For this, the invention relates to a triggering device when an electric current flowing in a conductive line reaches a current threshold, the device comprising a magnetic circuit and an electric switch.

[0010] The magnetic circuit comprises: a magnetic armature, extending between two ends called "poles", said magnetic armature being adapted to surround a part of the conductive line, and said magnetic armature having an opening between the two poles; a magnetic valve, movable relative to the magnetic armature between: an open position, in which the magnetic valve is distant from at least one of the two poles of the magnetic armature; and a closed position, in which the magnetic valve connects the two poles of the magnetic armature;a mechanism for holding the magnetic valve in the open position, said holding mechanism being configured to deform when a force is applied to the magnetic valve to close the magnetic valve, the holding mechanism allowing the valve to move to the closed position when said force applied to the valve reaches a force threshold, the force threshold being reached when the current threshold is reached.;

[0011] The electrical switch and the magnetic flap are arranged so that the switch is: on when the magnetic flap is in the closed position; and open otherwise.

[0012] When a current flows in the conductive line, it generates a magnetic field around the conductive line. The magnetic circuit, surrounding the line conductive, concentrates the magnetic field lines within it. A magnetic force is exerted on the magnetic flap to press it against the poles of the magnetic armature and close the magnetic circuit.

[0013] The magnetic force applied to the magnetic flap to close it is proportional to the magnetic field generated around the main conductive line and is therefore proportional to the intensity of the current flowing in the main conductive line.

[0014] The holding mechanism establishes a force threshold to be applied to close the magnetic circuit. Since the magnetic force is proportional to the current flowing in the main line, the holding mechanism establishes a current intensity threshold beyond which the intensity is considered abnormal and requires tripping.

[0015] Closing the magnetic circuit causes the electrical switch to close. This switch thus allows the triggering, for example, of an electrical cut-off device.

[0016] The triggering device according to the invention has a number of advantages relating to the reliability of detection and triggering. For example, its simplicity reduces the risk of failure. Indeed, the arrangement of the switch flap, allowing the switch to close when the magnetic flap closes, makes it possible to avoid failures that an electronic reading means could experience. The small number of elements involved also reduces the fragility of the device to vibrations.

[0017] The implementation of a magnetic circuit allows current measurement to be carried out without contact with the conductive line. Thus, the device is not influenced by a potential difference established in the conductive line. The device is therefore compatible with a conductive line operated at a low voltage, for example called "0 volts", or at a high direct voltage, for example 800 V direct. The device can also be used regardless of the direction of current flow. It also does not have a maximum admissible current. It cannot therefore be degraded when a very high amplitude current peak flows in the main conductive line.

[0018] The dimensions of the magnetic circuit can also be adjusted to accommodate different current levels, making it compatible with very high continuous currents of up to 10,000 A. In addition, when sized to detect high currents, the device has the advantage of being relatively insensitive to surrounding electromagnetic disturbances.

[0019] The movement inertia of the valve 21 also makes it possible not to detect transient current peaks that are too rapid, for example less than 1 ms. Indeed, rapid current peaks can be generated during the normal operation of an electrical system without it being necessary to cut the circuit.

[0020] The device is also not sensitive to air pressure. It can therefore be operated under vacuum, in a sealed enclosure maintaining a constant atmosphere, or in an atmosphere whose pressure can vary greatly (as can be the case in an aircraft).

[0021] Note that the closing of the magnetic valve does not involve integration of the current over time, unlike the operating mode of a fuse. Tripping can therefore be achieved in an extremely short time, for example less than 5 ms.

[0022] Advantageously, the electrical switch comprises: a first blade, fixed to the magnetic valve; and a second blade, the first and second blades being arranged to be in contact when the magnetic valve is in the closed position.

[0023] Advantageously, the magnetic valve is fixed on one of the poles and can pivot around said pole.

[0024] Advantageously, the device comprises a member for adjusting the force threshold of the holding mechanism, the adjustment member being, for example, a screw.

[0025] Advantageously, the holding mechanism is compatible with an aeronautical vibration environment. By "compatible with an aeronautical vibration environment", it can be understood that the holding mechanism is for example dimensioned so that the magnetic valve does not close in the presence of vibrations, for example having an amplitude equal to 12 g (where 1 g = 9.80665 ms 2 ), considering an electric current in the conductive line lower than the current threshold.

[0026] Advantageously, the holding mechanism is a spring.

[0027] Advantageously, the magnetic armature is made of ferromagnetic material or paramagnetic material; and the magnetic valve is made of ferromagnetic material or paramagnetic material.

[0028] The invention also relates to a short-circuit protection system, comprising: a conductive line; a triggering device according to the invention, the magnetic armature of the device surrounding the conductive line; a first cut-off device, connected in series with the conductive line; a pyrotechnic actuator, connected to the electrical switch of the triggering device and configured to actuate the first cut-off device when said electrical switch is on.

[0029] Advantageously, the magnetic valve holding mechanism is adapted to be arranged between the magnetic valve and the conductive line, the holding mechanism being adapted to bear against the magnetic valve on the one hand and against the magnetic armature or a base secured to the conductive line on the other hand.

[0030] Advantageously, the system comprises an electrically insulating lining surrounding the conductive line and separating the magnetic armature and the conductive line.

[0031] Advantageously, the first cut-off device is an electromechanical switch.

[0032] Advantageously, the system comprises a second cut-off device, connected in parallel with the first cut-off device, the pyrotechnic actuator also being configured to actuate the second cut-off device when the electrical switch of the triggering device is on.

[0033] Advantageously, the second cut-off device comprises a fuse and for which actuation by the pyrotechnic actuator is a pull of said fuse.

[0034] The invention further relates to a propulsion device of an aircraft comprising an electrical power supply line and a protection system according to the invention, the main conductive line of the protection system being connected to the electrical power supply line. BRIEF DESCRIPTION OF THE FIGURES

[0035] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. The figures are presented for information purposes only and in no way limit the invention. Unless otherwise specified, the same element appearing in different figures has a single reference.

[0036] [Fig. 1] schematically shows a first embodiment of a short-circuit protection system according to the invention.

[0037] [Fig. 2] shows a second embodiment of a short-circuit protection system according to the invention.

[0038] [Fig. 3], [Fig. 4] and [Fig. 5] show an embodiment of a triggering device according to the invention as well as the operating principle of said device.

[0039] [Fig. 6] shows a second embodiment of a short-circuit protection system according to the invention.

[0040] [Fig. 7] shows a mode of operation of the protection system of Figure 2. DETAILED DESCRIPTION

[0041] Figure 1 schematically presents a protection system 1 according to a first embodiment. The system 1 is adapted to be connected to an electrical supply line and to cut off the flow of current flowing in this line when the system 1 detects a short circuit.

[0042] The system 1 comprises a conductive line 2 also called “main conductive line”, adapted to be connected to a power supply line electrical. The system 1 also comprises a first branch 3 and a second branch 5 connected in parallel to each other. The two branches 3, 5 are inserted into the main conductive line 2.

[0043] The first branch 3 comprises a first cut-off device 4. As shown, the first cut-off device 4 is an electromechanical cut-off device. The second branch 5 comprises a second cut-off device 6. As shown, the second cut-off device 6 is a fuse. The current flowing in the main conductive line 2 then flows in the first and second branches 3, 5. The impedance of the second line 5 is advantageously greater than the impedance of the first line 3 to promote the flow of current in the first branch 3, through the first cut-off device 4. The fuse 6 is thus preserved.

[0044] The first and second cut-off devices 4, 6 are configured to cut off the flow of current in the first and second branches 3, 5. They are initially in a conducting state. The first cut-off device 4 is for example closed. The second device 6 is intact. The first cut-off device 4 is for example actuated to open. The second cut-off device 6 can melt under the action of the current flowing in the second branch 5. In the embodiment of FIG. 1, the second device 6 can also be actuated by traction to facilitate and / or accelerate its breaking.

[0045] The system 1 further comprises an actuator 10 configured to sequentially or simultaneously actuate the first and second cut-off devices 4, 6. In one embodiment, the actuator 10 initially actuates the first device 4, opening the first branch 3 and cutting off the flow of current in this branch 3. The opening of the first branch 3 allows the entire current flowing in the main conductive line 2 to be concentrated towards the second branch 5 alone. The increase in the current flowing in the second branch 6 thus allows the second cut-off device 6 to be melted. The actuator 10 actuates the second cut-off device 6 by traction. The traction makes it easier to break the second cut-off device 6.

[0046] Document FR 3 129 027 describes in more detail the operation of the first and second branches 3, 5 as well as that of the first and second cutting devices 4, 6.

[0047] The system 1 also comprises a third branch 13, called the “copy circuit”, comprising a third cut-off device 14. The third cut-off device 14, as illustrated, is an electromechanical device actuated by the actuator 10. It is advantageously actuated simultaneously with the first cut-off device 4. The copy circuit 13 is independent of the main conductive line. 2. It allows the state of the protection system 1 to be known. In fact, the action of the actuator 10 opens the copy circuit 13. Thus, the opening of the latter 13 indicates that the first and second devices 3, 5 have been actuated to open the branches 3, 5.

[0048] The actuator 10 may be electromechanical or pyrotechnic. The system 1 comprises a triggering device 12 for triggering the action of the actuator 10. Figure 1 shows a schematic embodiment of the triggering device 9. In this embodiment, the triggering device 9 comprises a magnetic circuit 11 and an electrical switch 12.

[0049] The switch 12 can take two states: open (called "non-conducting") or closed ("conducting"). It is initially in the open state. Its state depends on a state in which the magnetic circuit 11 is located (discussed below). The switch is connected on the one hand to a power supply 15 and on the other hand to the actuator 10. Closing the switch 12 thus triggers the actuator 10.

[0050] The magnetic circuit 11 is configured to detect a short circuit flowing in the main conductive line 2. It is based in particular on the measurement and comparison of the magnetic field generated by the conductive line 2. Indeed, the magnetic field generated by the conductive line depends on the intensity of the current flowing in said line 2. The higher the intensity of the current, the stronger the magnetic field generated. The magnetic circuit 11, which may also be called a “magnetic clamp”, may have two distinct states that may be called “open” and “closed”. Initially in the open state, it switches to the closed state when the magnetic field generated by the main conductive line 2 exceeds a threshold.

[0051] The magnetic circuit 11 and the switch 12 are connected so that closing the magnetic circuit 11 causes the switch 12 to close. In other words, detecting a magnetic field exceeding a threshold triggers the actuator 10 and therefore cuts off the current in the main line 2.

[0052] Figure 2 shows a second embodiment of the cut-off system 1. This figure shows a more detailed diagram of the system 1 and in particular of its triggering device 9. This system 1 is intended to be integrated into an electrical circuit of an aircraft and more particularly a high voltage direct current circuit (called "HVDC" for "High Voltage Direct Current" in English). It is for example integrated into a propulsion device of the aircraft. The device comprises for example an HVDC transmission line powering an electric motor from a turbogenerator or electric batteries. The system 1 is connected in series with said transmission line to cut off the flow of current to the motor in the event of a short circuit.

[0053] In this embodiment, the system 1 comprises a main line 2 extending parallel to a plane {X; Y}. It has two portions 25, 26 forming input and output terminals. The system 1 also comprises a first branch 3, inserted in series in the main conductive line 2, and a second branch 5, also inserted in series in the main conductive line 3 and connected in parallel with the first branch 3.

[0054] The first branch 3 comprises a first cut-off device 4 which is an electromechanical cut-off device. The second branch 5 comprises a second cut-off device 6 which is a pull-actuated fuse.

[0055] More particularly, the first cut-off device 4 comprises a conductive member 27 and a flexible conductive clamp 28. The conductive member 27 is connected to the main conductive line 2 and, in the present embodiment, on the side of the output terminal 26. The conductive clamp 28 is also connected to the main conductive line 2, on the side of the input terminal 25. The conductive member 27 and the conductive clamp 28 are arranged so that the clamp is engaged on the conductive member 27, gripping the latter and making electrical contact on two faces of the fixed member 27. The first cut-off device 4 also comprises insulating separators 29, 30 which can slide parallel to the plane {X; Y}. They can be pushed to insert themselves between the conductive member 27 and the conductive clamp 28, spreading the fingers of the clamp 28. The insulating separators 29, 30 then break the electrical contact between the conductive member 27 and the conductive clamp 28. The insertion of the insulating separators 29, 30 cuts off the flow of current in the first branch 3.

[0056] The second cut-off device 6 is a pull-actuated fuse. It comprises, for example, a conductive bar of fusible material fixed between two anchor points. Each anchor point is connected to one or other of the input 25 and output 26 terminals. By fusible material, we mean a material capable of melting when it has stored a sufficient quantity of heat. The bar of fusible material extends between the two anchor points parallel to the plane {X; Y}. One of the anchor points can slide parallel to the plane {X; Y}, allowing traction to be applied to the bar of fusible material.

[0057] The fusible material bar can break on its own, under the sole action of a current flowing through it and inducing the melting of the fusible material. The traction of the fusible material bar makes it possible to facilitate or even accelerate the breaking of the bar when the latter, heated by the current flowing through it, has reached sufficient ductility. The traction of the bar also makes it possible to force the breaking of the bar even when the latter has not been sufficiently heated in order to guarantee the cutting of the second branch 5.

[0058] The system 1 comprises an actuator 10 for actuating the first and second cut-off devices 4, 6. In the embodiment of FIG. 2, the actuator 10 is in particular a pyrotechnic actuator. It comprises a cylinder 32 comprising a chamber and a piston 33. The triggering of a pyrotechnic charge in the chamber pushes the piston 33 and makes it possible to actuate the first and second cut-off devices 4, 6. In the example illustrated, the piston 33 communicates a mechanical force to the insulators 29, 30 via an arm 34 mounted on a pivot. The mechanical force developed by the piston 33 is also communicated to the second cut-off device via the rotary arm 34.

[0059] The system 1 comprises a triggering device 9 for the pyrotechnic actuator 10. The device 9 comprises a magnetic circuit 11 and an electrical switch 12.

[0060] The magnetic circuit 11 is arranged near the input terminal 25 of the protection system 1. It could also be arranged near the output terminal 26 of the protection system 1. The magnetic circuit 11 comprises a magnetic armature 20 and a magnetic valve 21. The magnetic armature 20 and magnetic valve 21 are for example made from pure iron. It is expected that the magnetic field lines that can be produced by the main line 2 are concentrated in the armature 20 and in the valve 21. For this, the magnetic armature 20 can be made from a ferromagnetic material or a paramagnetic material. The magnetic valve 21 can also be made from a ferromagnetic material or a paramagnetic material.

[0061] In the embodiment of Figure 2, the magnetic armature 20 partially surrounds the main line 2. The armature 20 in this case forms an open loop (in other words forms a “C”) around the main line 2. The armature 20 extends in particular between a first end 20a and a second end 20b, called “first and second poles”, the first and second poles 20a, 20b being distant from each other.

[0062] The magnetic valve 21 is a part independent of the armature 20. It is movably fixed on the second pole 20b, so as to be able to rotate around the second pole 20b. The valve has a length allowing it, in a so-called "closed" position, to join the first pole 20a. Thus, the valve 21, in its closed position, allows the magnetic circuit 11 to be closed. The magnetic circuit 11 therefore completely surrounds the main line 2.

[0063] The valve, in a so-called "open" position, is distant from the first pole 20a. Thus, the valve 21, in its open position, opens the magnetic circuit 11. The latter no longer completely surrounds the main line 2.

[0064] The axis of rotation of the valve relative to the armature 20 is oriented in the plane {X; Y] and more particularly in the direction X, the direction in which the portion of the main line 2 surrounded by the magnetic circuit 11 extends. In other words, the valve 21 moves in the transverse plane, that is to say {Y; Z} in figure 2.

[0065] For example, the second pole 20b of the armature 20 may have a hinge into which one end of the valve 21 fits.

[0066] The armature 20 is preferably fixed relative to the conductive line 2. However, it can also be mobile relative to the main line 2. It is, more preferably, mobile in rotation or in translation in the transverse plane, i.e. {X; Y} in figure 2. Considering a rotation of the armature 20 and the valve 21, the magnetic circuit 11 can then show a movement resembling a clamp which can close on the main line 2.

[0067] Alternatively, the valve 21 can be mounted so as to be movable in translation relative to the armature 20. It could, for example, move along the Z axis. In its open position, the valve 21 would then be distant from the two poles 20a, 20b. In its closed position, the valve 21 would be pressed against the two poles 20a, 20b. The armature 20 can be fixed relative to the main line 2 or movable relative to this line 2 and also in translation relative to the line 2.

[0068] The magnetic circuit 11 also has a holding mechanism 35, not shown in FIG. 2 but described with reference to FIGS. 3, 4 and 5. The holding mechanism 35 works against the closing of a force applied to the valve 21 and aimed at closing the latter. The holding mechanism 35 is configured to allow the closing of the valve 21 when a force applied to the valve 21 exceeds a threshold.

[0069] In this embodiment, the system 1 comprises a base 31, also called a “support”. Different elements can be fixed to the base 31 so as to be integral with this base 31. For example, the conductive line 2 can be fixed to the base 31 while being electrically insulated from it. The magnetic armature 21 can also be fixed to the base 31.

[0070] The electrical switch 12 is arranged to be: closed when the valve 21 is in the closed position; and open when the valve 21 is in the open position.

[0071] In this embodiment, the switch 12 comprises in particular a first conductive blade 22, fixed on the flap 21, moving with the flap 21. The switch 12 also comprises a second conductive blade 23, fixed relative to the armature 20. In the example of FIG. 2, since the armature 20 is fixed relative to the main line 2, the second blade 23 is also fixed relative to the main line 2. It can bear on the base 31. The first blade 22 can be connected, by means of a conductive sheet, to a power supply (not shown). The second blade 23 is connected to the actuator 10 so as to trigger the latter when a current passes through it. When the valve 21 is in the closed position, the first and second are in contact 24 with each other, allowing the actuator 10 to be triggered.

[0072] According to an alternative embodiment, the armature 20 and the valve 21 form the switch 12. For this, the valve 21 is electrically isolated from the armature 20 when it is in the open position and electrically connected to the armature 20 when it is in the closed position. According to one embodiment, the hinge around which the valve 21 rotates, formed in the second pole 20b, comprises an electrically insulating layer. According to another embodiment, the valve 21 moves in translation relative to the armature 20, being distant from the armature 20 in the open position and pressed against the poles 20a, 20b of the armature 20 in the closed position.

[0073] Thus, the valve 21 can be connected to a power supply by means of a conductive sheet and the armature 20 can be connected to the actuator 10 so as to trigger the latter when an electric current flows through the latter (when the valve 21 is in contact with the armature 20).

[0074] Figures 3, 4 and 5 schematically show the magnetic circuit 11 and the main line 2 in a cross-section of the main line 2 with the valve 21 in its open (Figures 3 and 4) and closed (Figure 5) position. In these examples, the armature 20 partially surrounds the main line 2. The valve 21 is mounted movably on the armature 20. In particular, it can move by rotation around the second pole 20b of the armature 20.

[0075] The circuit 11 comprises a holding mechanism 35. The mechanism 35 has, for example, an elastic mechanical behavior characterized by a predetermined compression force. It is, for example, a spring or a deformable body having said compression force. The holding mechanism 35 is configured to work against a force operating on the valve 21 and aimed at closing the valve 21 (by "closing" is meant moving the valve 21 into its closed position). The force applied to the valve 21 is, for example, a magnetic force Fmag aimed at closing the magnetic circuit 11 and resulting from the magnetic field B circulating in the magnetic circuit 11.

[0076] Indeed, the circulation of a current I in the main line 2 induces a magnetic field B in the vicinity of the main line 2. The magnetic field B is concentrated in the magnetic material of the armature 20 and the valve 21. When the valve 21 is in the open position, a force Fmag is applied to the valve 21 to close the valve 21. This force Fmag of magnetic origin aims to minimize the path of the field lines B outside the magnetic material. The holding mechanism 35 therefore works against this magnetic force Fmag.

[0077] The holding mechanism 35 is however configured to allow the closure of the valve 21 when the magnetic force Fmag reaches a threshold. In the case of a spring, for example prestressed, working in compression against the closure of the valve, a preloading force (resulting for example from the installation of the spring) is dimensioned so that when the magnetic force Fmag reaches the threshold, the spring allows the closure of the valve 21.

[0078] Alternatively, the holding mechanism 35 is a body that can exhibit plastic rather than elastic behavior. It compresses (or stretches) in a non-reversible manner until it allows the valve 21 to close when the magnetic force reaches a threshold Fmag. Alternatively, the holding mechanism 35 is a body, for example a capsule, that can break when the magnetic force reaches the threshold. Thus, when the holding mechanism 35 breaks, nothing prevents the valve 21 from closing. The advantage of irreversible deformation is that it keeps the magnetic circuit 11 in its closed state even if the current intensity in the main line 2 decreases. Conversely, a holding mechanism exhibiting reversible deformation can return to its initial open position after the breaking devices 4, 6 have opened.

[0079] The amplitude of the magnetic force Fmag applied to the valve 21 depends on the amplitude of the magnetic field circulating in the magnetic circuit 11. The higher this amplitude, the higher the force exerted on the valve 21. The amplitude of the magnetic field in the magnetic circuit 11 is directly proportional to the amplitude of the electric current I circulating in the main line 2. Thus, the force threshold Fmag to be applied to the valve 21 to close the latter defines a threshold of current circulating in the main conductive line 2. The holding mechanism 35 therefore makes it possible to directly define the maximum current that can circulate in the main line 2, beyond which the magnetic circuit 11 closes.

[0080] Figures 4 and 5 show two cases where the current I flowing in the main line 2 is respectively lower and higher than a current threshold. The force threshold of the spring 35 (corresponding for example to the preload force) defines a magnetic force threshold to be applied to the valve and therefore directly a current threshold. When the current I flowing in the main line 2 is lower than the current threshold, the magnetic force Fmag exerted on the valve 21 is not sufficient to close the latter (figure 4). On the other hand, as soon as the amplitude of the current I exceeds the current threshold, the magnetic force exceeds the force threshold to be applied and thus allows the valve 21 to close (figure 5).

[0081] The magnetic circuit 11 and its holding mechanism 35 therefore make it possible to define a current threshold beyond which a trigger is made. It thus makes it possible to detect a short circuit circulating in the main line 2.

[0082] Figures 4 and 5 also show the switch 12 and more particularly the latter when it is made from blades 22, 23. These figures also show a conductive sheet 40 connected to the first blade 22 fixed on the valve 21 and capable of conveying a current to the switch 12. In the example of Figure 4, when the current I is too low to induce the closing of the valve 21, the blades 22, 23 remain distant. On the other hand, in the example of Figure 5, when the current I is sufficiently strong (for example a short circuit), the valve 21 is closed and the two blades 22, 23 of the switch 12 are in contact, triggering the actuator 10 and therefore cutting off the flow of current in the two branches 3, 5.

[0083] The magnetic force Fmag applied to the valve 21 depends on several parameters. It depends in particular on the proximity of the magnetic circuit 11 to the main line 2. Indeed, the magnetic field decreases in 1 / r where r is the distance from the main line 2. The further the armature 20 and the valve 21 are from the main line 2, the lower the magnetic force exerted on the valve 21. The magnetic force Fmag also depends on the materials of the armature 20 and the valve 21.

[0084] In order to correctly define the force threshold and therefore the current threshold in the main line 2, the holding mechanism 35 is preferably adjustable. By adjustable, it is meant that it is possible to adjust at least one parameter of the holding mechanism working against the magnetic force applied to the valve 21. For this, the triggering device 9 comprises an adjustment member 52. In the case where the holding mechanism 35 is a spring, the adjustment member 52 adjusts for example the initial opening of the valve (i.e. the angle of the valve in its open position). The greater the opening of the valve 21, the greater the force to be applied to the valve 21 to close the latter must be. Increasing the initial opening of the valve 21 can therefore increase the force threshold to be applied to close the valve 21 and therefore increase the current threshold to be reached to trigger the device 9 accordingly. Alternatively, the adjustment member 52 can modify the preload force of the spring (and therefore the compression force to be applied against the closure of the valve). For example, the adjustment member 52 could be a screw which preloads the spring, increasing or decreasing the preload force of the spring.

[0085] Figure 6 shows an embodiment of the system 1 and in particular of the triggering device 9 inserted into the protection system 1. In this embodiment, the system 1 comprises a lining 50 surrounding the main line 2. The lining 50 separates the main line 2 from the magnetic circuit. In this case, it is an electrically insulating lining 50 making it possible to protect the magnetic circuit 11 and / or the switch 12 from direct electrical contact with the main conductive line 2. This electrical contact could induce parasitic triggering of the actuator 10.

[0086] In this embodiment, the holding mechanism 35 of the magnetic circuit is a spring. It is arranged between the magnetic valve 21 and the main line 2 to work in compression against the closing of the valve 21. On the one hand, it bears in particular on the main line 2 and in particular on the insulating lining 50 surrounding it, and on the other hand it bears on the valve 21.

[0087] Furthermore, in this embodiment, the holding mechanism 35 comprises a ring 51 intended to hold the spring 35 in a fixed position and prevent it from moving or being removed. The spring 35 can thus work freely until the valve 21 closes. The ring 51 can bear on the magnetic armature 20 or on the base 31. It can also bear on the lining 50.

[0088] In an alternative embodiment, the holding mechanism 35 could be an insulating elastic body, such as an elastomer. In this event, the holding mechanism 35 would no longer require the use of the insulating gasket 50 to ensure good insulation between the valve 21 and the line 2.

[0089] In Figure 6, the device 9 comprises an adjustment member 52 for the holding mechanism 30. The member 52 is a screw against which the valve 21 abuts when it is in the open position. The screw 52 makes it possible to adjust the initial opening of the valve 21.

[0090] Figure 7 shows a mode of operation of a protection system 1 as presented with reference to Figure 2. System 1 is operated under a continuous voltage of 800 V. The current threshold, beyond which system 1 is expected to cut off the current flow, is 4000 A. System 1 can preferably be operated under an atmospheric pressure of 572 mbar. This pressure is equivalent, considering an air temperature of 0 -C, to 15,000 feet altitude, or 4,572 meters altitude.

[0091] Figure 7 shows several curves 80, 81, 82, 83, 84 as a function of a common time abscissa 70. This concerns more particularly: the supply voltage 80 applied to the terminals of the system 1; the current 81 flowing in the main line 2; the voltage 82 at the terminals of the first branch 3 and more particularly at the terminals of the first cut-off device 4; the current 83 flowing in the second branch 5 and more particularly in the fuse 6; the current 84 flowing in the pyrotechnic actuator 10.

[0092] The duration 70 considered is approximately 13 ms.

[0093] At a first instant 71, the current 81 flowing in the main line 2 reaches the current threshold of 4000 A. The current 81 induces a magnetic field around the main line 2.

[0094] At a second instant 72, the electrical switch 12 closes, allowing a current 84 to flow in the actuator 10. The interval between the first instant 71 and the second instant 72 corresponds to the time required to detect the short circuit 81 in the main line 2. This time interval takes into account the duration of the movement of the valve 21 to move from its open position to its closed position. This time interval 72 - 71 can last approximately 1.5 ms.

[0095] At a third instant 73, the electromechanical cut-off device 4 starts moving to cut off the flow of current 81 in the first branch 3. The time interval between the second instant 12. and the third instant 73 takes into account the triggering of the pyrotechnic actuator 10. This time interval 73 - 72 can last approximately 0.5 ms. At the end of the opening of the electromechanical cut-off device 4, the current 81 flowing in the main line 2 is entirely directed towards the second branch 5 and more particularly into the fuse 6.

[0096] At a fourth instant 74, the current flow 83 in the fuse is cut off because the fuse 6 has melted and / or has been torn off by the traction of the electromechanical cut-off device 4. The time interval between the third instant 73 and the fourth instant 74 may last less than 1 ms.

[0097] At a fifth instant 75, the flow of current 81 in the first branch 3 and / or the second branch 5 stops. The system has switched to a blocked state to prevent the flow of a short circuit in a power supply line.

[0098] The time interval, called "cut-off time", between the appearance of the short circuit on the main line (first instant 71) and the final cut-off of system 1 (fifth instant 75) can last less than 3 ms.

[0099] Two tests carried out on systems 1 comparable to system 1 in Figure 2 show a first cut-off time of 3.327 ms and a second cut-off time of 2.979 ms. System 1 according to the invention therefore makes it possible to achieve a cut-off in a time of less than 5 ms.

Claims

CLAIMS

1. Device (9) for triggering when an electric current flowing in a conductive line (2) reaches a current threshold, the device comprising a magnetic circuit (11) and an electric switch (12), the magnetic circuit (11) comprising: - a magnetic armature (20), extending between two ends (20a, 20b) called “poles”, said magnetic armature (20) being adapted to surround a part of the conductive line (2), and said magnetic armature (20) having an opening between the two poles (20a, 20b); - a magnetic valve (21), movable relative to the magnetic armature (20) between: - an open position, in which the magnetic valve (21) is distant from at least one of the two poles (20a, 20b) of the magnetic armature (20); and - a closed position, in which the magnetic valve (21) connects the two poles (20a, 20b) of the magnetic armature (20); - a holding mechanism (35) for holding the magnetic valve (21) in the open position, said holding mechanism (35) being configured to deform when a force (Fmag) is applied to the magnetic valve (21) to close the magnetic valve (21), the holding mechanism (35) allowing the valve to move into the closed position when said force applied to the valve reaches a force threshold, the force threshold being reached when the current threshold is reached, the electrical switch (12) and the magnetic valve (21) being arranged so that the switch (12) is: - passing when the magnetic valve (21) is in the closed position; and - open otherwise.

2. Device (9) according to the preceding claim, in which the electrical switch (12) comprises: - a first blade (22), fixed on the magnetic valve (21); and a second blade (23), the first and second blades (22, 23) being arranged to be in contact when the magnetic valve (21) is in the closed position.

3. Device (9) according to one of the preceding claims, in which the magnetic valve (21) is fixed on one of the poles (20a, 20b) and can pivot around said pole (20a, 20b).

4. Device (9) according to one of the preceding claims, comprising a member (52) for adjusting the force threshold of the holding mechanism (35).

5. Device (9) according to one of the preceding claims, in which the holding mechanism (35) is a spring.

6. Device (9) according to one of the preceding claims, in which the magnetic armature (20) is made of ferromagnetic material or paramagnetic material; and in which the magnetic valve (21) is made of ferromagnetic material or paramagnetic material.

7. System (1) for protection against a short circuit, comprising: - a conductive line (2); - a triggering device (9) according to one of the preceding claims, the magnetic armature (20) of the device (9) surrounding the conductive line (2); - a first cutting device (4), connected in series with the conductive line (2); - a pyrotechnic actuator (10), connected to the electrical switch (12) of the triggering device (9) and configured to actuate the first cut-off device (4) when said electrical switch (12) is on. [Claim s] System (1) according to the preceding claim, in which the holding mechanism (35) of the magnetic valve (21) is adapted to be arranged between the magnetic valve (21) and the conductive line (2), the holding mechanism (35) being adapted to bear against the magnetic valve (21) on the one hand and against the magnetic armature (20) or a base (31) secured to the conductive line (2) on the other hand.

9. System (1) according to one of the two preceding claims, wherein the first cut-off device (4) is an electromechanical switch.

10. System (1) according to one of the three preceding claims, comprising a second cut-off device (6), connected in parallel with the first cut-off device (4), the pyrotechnic actuator (10) also being configured to actuate the second cut-off device (6) when the electrical switch (12) of the triggering device (9) is on.

11. System according to the preceding claim, wherein the second cut-off device (6) comprises a fuse and for which an actuation by the pyrotechnic actuator (10) is a pulling of said fuse.

12. A propulsion device for an aircraft comprising an electrical power supply line and a protection system according to one of the five preceding claims, the main conductive line of the protection system being connected to the electrical power supply line.

Images