Device and method for initiating an electric arc on electronic equipment, particularly power equipment.

Abstract

The invention relates to a device for initiating an electric arc (9) in electronic equipment (10) with a view to testing its behavior under the effect of this electric arc and / or under the effect of an electric fire generated by it, the initiating device (9) comprising: - a transistor (19) comprising two power pins (22a, 22b) and a control pin (21), the power pins being able to be electrically connected to a first electrical track and to a second electrical track of said equipment (10), and - a control circuit (20) of the transistor configured to apply to the control pin (21) of the transistor (19) a control signal able to cause the irreversible closing of the transistor (19) and to cause the short-circuiting of the transistor (19) while the first track (13a) and the second track (13b) are energized, and thus to generate an electric arc. Figure for the abstract: Fig. 2

Description

Title of the invention: Device and method for initiating an electric arc on electronic equipment, particularly power equipment. Technical field

[0001] The present invention relates to the field of testing the behavior of electronic equipment under the effect of electric arc, electric short circuit and electric fire generated by them.

[0002] It relates more particularly to a device for initiating an electric arc in electronic equipment, in particular power equipment.

[0003] It also relates to a method of initiating an associated electric arc.

[0004] The invention finds particularly advantageous application in the aeronautical field, but also applies to any other electrical field. STATE OF THE ART

[0005] Climate change is a major concern for many legislative and regulatory bodies around the world. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies both to new types of aircraft and those in circulation requiring the implementation of technological solutions in order to make them compliant with current regulations. Civil aviation has been mobilizing for several years now to make a contribution to the fight against climate change.

[0006] Technological research efforts have already made it possible to significantly improve the environmental performance of aircraft. The Applicant takes into consideration the impact factors in all phases of design and development to obtain less energy-intensive, more environmentally friendly aeronautical components and products whose integration and use in civil aviation have moderate environmental consequences with the aim of improving the energy efficiency of aircraft.

[0007] Consequently, the Applicant is constantly working to reduce its negative climate impact by using methods and operating virtuous development and manufacturing processes and minimizing greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity.

[0008] This sustained research and development work covers both new generations of aircraft engines, the lightening of aircraft, in particular through the materials used and the lightened on-board equipment, the development of the use of electric technologies to ensure propulsion, and, essential complements to technological progress, aeronautical biofuels.

[0009] Particularly in the aeronautical field, the trend is towards the electrification of aircraft with architectures that can use high voltage direct current (HVDC) power sources and / or high voltage alternating current power sources, to power propulsive and / or non-propulsive loads. These architectures integrate a number of electronic power conversion devices (AC / AC, AC / DC, DC / DC, DC / AC), which should be able to be qualified. More generally, since aircraft carry a number of electronic devices integrated into architectures using high voltage networks, it is appropriate to qualify the electronic equipment in the conditions of their use. This is also the case for electronic equipment in other fields, particularly in the tertiary or automotive fields.

[0010] In particular, operational safety requirements of electronic equipment must be verified.

[0011] In particular, the performance and reaction of electronic equipment when an electric arc occurs, which could cause an electrical fire, must be certified with regard to such requirements.

[0012] To facilitate such electronic equipment qualification activities, it is necessary to be able to initiate an electric arc in a reliable, reproducible and safe manner for test operators.

[0013] Devices and methods for striking an electric arc have thus been developed.

[0014] [Fig.l] illustrates in particular a device 1 for striking an electric arc usually used to strike an electric arc under laboratory conditions.

[0015] The device 1 comprises an electrical circuit 2 connecting an electrical power source 3, a power contactor 4 actuable using an actuator 5 (for example, an auxiliary electrical circuit) and connected directly in series downstream of the source 3, a pair of electrical bars 6 and 7, the first bar 6 being arranged in series upstream of the source 3 and the second bar 7 being arranged in series downstream of the contactor 4. The device 1 also comprises a fuse wire 8 connecting the two electrical bars 6 and 7 together, which is a wire of small dimensions compared to the other electrical conductors (the electrical bars 6 and 7 for example) of the device, sized to fulfill a fuse function from a certain level of current passing through it.

[0016] The fusible wire 8 forms a portion of electrically conductive material, for example copper, tin, iron or any electrically conductive material.

[0017] Before activation of device 1, the entire circuit 2 is initially de-energized because the contactor 4 occupies an open position of the electrical circuit 2.

[0018] When the device 1 is activated, the contactor 4 moves to the closed position due to the activation of the actuator 5 and the source 3 then energizes the electrical circuit 2, and in particular the electric bars 6 and 7. The fusible wire 8 then sees a short-circuit current flow, generating joule losses in the fusible wire 8 leading the wire 8 to a melting point quickly. When the molten fusible wire 8 breaks and opens, the short-circuit current is not interrupted instantly and the electrons passing through the medium (air or vacuum) between the two electric bars 6 and 7 ionize this medium, initiating an electric arc which forms a conductive path between these two bars. The electric arc maintained by the source 3 only stops when the contactor 4 opens.

[0019] Nevertheless, the application of this fuse wire technique for testing or qualifying electronic equipment such as it should be on board, for example in an aircraft, has several drawbacks and is difficult to envisage.

[0020] Indeed, the electric bars 6 and 7 of the arc striking device are then for example two electric tracks of an electronic card of the equipment, or two busbars of the electronic equipment to be tested, brought to different potentials when the equipment is energized. The placement of a fuse wire inside such equipment thus requires a manual operation of dismantling the casing of the electronic equipment, laying and fixing a fuse wire, for example between two electric tracks, then reassembling the casing. This complex manual operation proves to be very delicate in practice while its proper execution is essential to the proper conduct and success of the test. Indeed, if this operation is poorly performed, for example, if the wire is poorly laid or fixed, the wire can be expelled before reaching the melting point under the effect of the electromotive forces induced by the short-circuit current, and there will be no electric arc.

[0021] Also, electronic power equipment, such as power converters, for example inverters for motor control, or power supplies, are composed of power switches (in particular field effect transistors (MOSFET, IGBT, etc.) or bipolar transistors used in high voltage switches; and power capacitors, generally used for filtering currents, connected to the terminals of the high direct voltage supply HDVC (from the Anglo-Saxon "High Direct Voltage Current") with which such power equipment operates. These power capacitors pose various problems for the proper conduct of the test.

[0022] Furthermore, we have seen that the test using the fusible wire technique begins at zero voltage. The capacitors are thus discharged. Since they prevent large voltage variations at their terminals, they tend to maintain a near-zero voltage, which prevents the formation of an arc. And even if an electric arc were to form, it would not occur under conditions representative of reality. Indeed, during operational operation, the electronic equipment is energized, and these power capacitors are pre-charged. In the event of a short-circuit of these capacitors, for example due to an electric arc, the energy stored in these power capacitors becomes a source of strong discharge currents in the equipment. That is to say, during operational operation of the equipment, these capacitors are charged and they play an active role in the dynamics of the short circuit, which the fuse wire technique conceals.

[0023] An existing alternative method is that of drip irrigation, which consists of flowing an ionized liquid over a stripped portion of a conductor or an electrical circuit which will dissolve under the action of successive droplets. However, this solution is difficult to integrate inside power electronics equipment, and its control is hazardous. In particular, control by a solenoid valve is complex and expensive to carry out because of the risks of destruction by the electric arc produced. EXPOSED

[0024] An aim of the present invention is to overcome the aforementioned drawbacks, by proposing a device for striking an electric arc in electronic equipment with a view to testing its behavior under the effect of this electric arc and / or under the effect of an electric fire generated by it. In particular, an aim of the invention is to propose such a device which is reliable, which makes it possible to easily strike an electric arc under conditions faithful to reality (i.e. with initial test conditions in which the electronic equipment is already energized), which is applicable to power electronic equipment comprising power capacitors, and which is safe for the operator.

[0025] To this end, according to a first aspect, a device is proposed for initiating an electric arc in electronic equipment with a view to testing its behavior under the effect of this electric arc and / or under the effect of an electric fire generated by it, a power supply being provided for powering up said equipment establishing a supply voltage between a first electrical track or at a first electrical potential point and a second electrical track or a second electrical potential point of said equipment,

[0026] the initiating device comprising:

[0027] - a transistor having two power pins and one control pin of a gate of the transistor, the two power pins being able to be electrically connected one to the first electrical track or to the first electrical potential point and the other to the second electrical track or second electrical potential point of said equipment, said transistor being able to withstand a voltage between its power pins greater than or equal to said supply voltage and calibrated to pass a current

[0028] between its two lower power pins of the order of 5 to 15 times a current delivered by said power supply,

[0029] - a transistor control circuit electrically isolated from the power supply of power and configured to apply a trigger control signal to the control pin capable of causing irreversible closing of the transistor by avalanche effect while the equipment and therefore the first track or the first potential point on the one hand and the second track or the second potential point on the other hand are energized, so as to generate an electric arc under the effect of said current delivered by the power supply.

[0030] Advantageously, the power supply of the priming device comprises a power supply source and a power contactor capable of:

[0031] - to be activated on closing to allow the equipment to be powered up electronics prior to the application of the ignition control signal capable of causing the transistor to close and initiating an electric arc, and

[0032] - to be activated in opening for switching off said equipment, so as to cut off the power supply to the electric arc later.

[0033] Preferably, the electronic equipment comprises at least one capacitor between the first and second electrical tracks or first and second electrical potential points, the switching on of the electronic equipment allowing the charging of said capacitor.

[0034] Advantageously, the power supply further comprises a pre-charging circuit capable of limiting the inrush current when charging the capacitor when the electronic equipment is powered up.

[0035] Advantageously, the transistor gate control circuit comprises:

[0036] - a resistive divider bridge comprising a high resistance and a low resistance, a midpoint of the resistive divider bridge between the high resistance and the low resistance forming an output of the control circuit providing said trigger control signal on the control pin of the gate of the transistor,

[0037] and

[0038] - a control contactor connected in series with the resistive divider bridge, for control the switching on of said resistive divider bridge in a controlled closed state by an activation signal, to establish a trigger control signal capable of causing the irreversible closing of the transistor by avalanche effect.

[0039] Advantageously, the resistive divider bridge of the control circuit is powered by the power supply source.

[0040] Preferably, the control contactor is mounted in series with the resistive divider bridge between, on the one hand, the power contactor which is connected to the positive pole of the power supply source and, on the other hand, to the negative pole of said source.

[0041] The invention also relates to a method for initiating an electric arc on electronic equipment with a view to testing its behavior under the effect of this electric arc and / or under the effect of a fire generated by it, in which the following steps are implemented:

[0042] - positioning on the electronic equipment of a transistor comprising two power pins and a gate control pin, by electrically connecting one of the two power pins to a first electrical track or a first electrical potential point (13a) and the other of the two power pins to a second electrical track or a second electrical potential point of said equipment,

[0043] - powering up the power equipment and therefore said first and second tracks and / or said first and second potential points by a power supply, establishing a supply voltage between the power pins, then,

[0044] - initiation of an electric arc between the two power pins of the transistor by applying to the gate control pin of the transistor a control signal capable of causing the transistor to close by avalanche effect such that an electric arc can start between the two power pins passing a current delivered by said power supply of the equipment.

[0045] Advantageously, the powering up comprises the charging of a capacitor that the electronic equipment comprises between the first and second electrical tracks or first and second electrical potential points.

[0046] Advantageously, the capacitor is precharged when powered up or beforehand by a dedicated precharge device.

[0047] The invention also relates to a use of a device for striking an electric arc as defined above for testing the behavior of electronic equipment under the effect of an electric arc and / or under the effect of a fire generated by the latter, in which the striking method as defined above is implemented on one or more samples of electronic equipment whose behavior is to be tested.

[0048] Advantageously, the electronic equipment is power equipment equipping or intended to equip aircraft. DESCRIPTION OF FIGURES

[0049] Other characteristics, aims and advantages of the invention will emerge from the following description, which is purely illustrative and non-limiting, and which must be read in conjunction with the appended drawings in which:

[0050] [Fig.l] schematically illustrates a device for striking an electric arc under laboratory conditions according to the prior art;

[0051] [Fig.2] schematically illustrates a device for initiating an electric arc in electronic equipment according to the invention and according to a first embodiment;

[0052] [Fig.3] schematically illustrates the device for striking an electric arc in electronic equipment of [Fig.2] with a possible embodiment of the control circuit; and

[0053] [Fig.4] schematically illustrates the different stages of the method according to the invention.

[0054] Throughout the figures, similar elements bear identical references. DETAILED DESCRIPTION

[0055] [Fig.2] illustrates a device 9 for testing electronic equipment 10 in that the device 9 is capable of ensuring the ignition of an electric arc in said electronic equipment 10.

[0056] In the following, the electronic equipment 10 considered is power electronics equipment.

[0057] Said electronic equipment 10 comprises an electronic card 12 having various electrical components, in particular one or more power capacitors 14, and several electrical tracks. In [Fig.2], only a power capacitor 14 connected between two electrical tracks 13a, 13b has been shown in a simplified manner, that is to say in parallel between these two electrical tracks 13a and 13b. The two electrical tracks 13a and 13b are provided to distribute the power supply to the various elements of the electronic equipment 10, and more particularly of the electronic card 12.

[0058] The priming device 9 comprises a power supply circuit 15 (or power supply 15) and a priming means 11, which comprises a transistor 19 and a circuit 20 for controlling the transistor 19.

[0059] Transistor 19 is a field effect transistor such as a MOSFET transistor, or an IGBT transistor, voltage controllable. Transistor 19 includes a control pin 21 or gate and two power pins (also called control pins conduction) 22a, 22b, corresponding respectively to the drain and source pins of a MOSFET transistor, or respectively to the emitter and collector pins of an IGBT transistor. In the following, we consider the case where transistor 19 is a MOSFET transistor.

[0060] Control pin 21 is controlled by control circuit 20.

[0061] The power supply circuit 15 comprises a power source 16 and a contactor of power 17.

[0062] The power supply source 16 powers the electronic card 12 via a connection interface.

[0063] Galvanic and physical isolation is provided between the power source 16 and the control circuit 20. This isolation is intended to ensure the safety of people.

[0064] This power supply source 16 may be a direct voltage source; it comprises a positive pole and a negative pole corresponding respectively to a positive voltage and to a negative or zero voltage.

[0065] As indicated previously, the electronic card 12 comprises a first electrical track 13a and a second electrical track 13b. The first track 13a of the electronic card 12 is connected to the negative pole of the power supply source 16. The power contactor 17 is connected between the positive pole of the power supply source 16 and the second track 13b of the electronic card 12, which is therefore connected to this positive pole.

[0066] The power pin 22a, respectively the power pin 22b, is connected to the first electrical track 13a, respectively to the second electrical track 13b. The power pin 22a therefore corresponds to the source of the transistor 19 when the transistor 19 is a MOSFET transistor, or to the collector of the transistor 19 when the transistor 19 is an IGBT transistor. The power pin 22b therefore corresponds to the drain of the transistor 19 when the transistor 19 is a MOSFET transistor, or to the emitter of the transistor 19 when the transistor 19 is an IGBT transistor.

[0067] Alternatively, the electronic card 12 may comprise, instead of the tracks 13a, 13b, electrical potential points brought respectively to the high and low voltages delivered by the power supply source 16 when the equipment 10 and therefore the card 12 are powered on. Such potential points are, for example, busbars.

[0068] The transistor 19 is arranged on the electronic card 12 in a zone Z inside the electronic equipment 10 in which it is desired to initiate an electric test arc. In the example illustrated, this zone Z includes the power capacitor 14 arranged nearby and itself connected to the tracks 13a and 13b.

[0069] The power supply source 16 is sized to provide between its positive pole and its negative pole a so-called short-circuit current corresponding to the conditions of the experiment, for example 400 volts.

[0070] The power contactor 17 makes it possible to control the powering up of the tracks 13a, 13b and therefore of the electronic card 12. When the contactor 17 is closed, the electronic card 12 is powered up by the source 16, the first electrical track 13a being brought to the low voltage delivered by the negative pole of the source 16, and the second electrical track 13b being brought to the high voltage delivered by the positive pole of the source 16.

[0071] The open or closed state of the power contactor 17 is controlled by an actuator 18. This actuator 18 may comprise a coil 18a, a power source 18c and a control means 18b, which is for example a switch arranged in series between the power source 18c and the coil 18a. The power source 18c has a first terminal connected to an electrical ground of the circuit of the actuator 18 and a second terminal connected to the control means 18b.

[0072] When the control means 18b distributes the energy produced by the power source 18c to the coil 18a, the coil 18a produces a magnetic field causing the power contactor 17 to close, which allows said power contactor 17 to power up the electronic card 12. Conversely, when the control means 18b does not distribute the energy produced by the power source 18c to the coil 18a, the power contactor 17 remains or goes into the open position, which cuts off the powering up of the electronic card 12.

[0073] Preferably, the power supply circuit 15 further comprises a circuit 17P for precharging the capacitors 14. Such a precharging circuit 17P makes it possible to protect against any electromagnetic disturbance likely to disturb the control of the transistor 19 for the ignition of an electric arc between its power pins 22a, 22b.

[0074] It allows to control the priming conditions in a robust manner.

[0075] The precharging circuit 17P is for example connected in parallel to the power contactor 17. Such a precharging circuit 17P conventionally comprises, for example, a current limiting resistor and a switch in series or in parallel. When the power supply circuit 15 is switched on (Power ON), it makes it possible to limit the inrush current linked to the charging of the capacitor 14. Once the charging of the capacitor 14 is complete (which is detected by monitoring the current level), the power contactor 17 can be activated.

[0076] The control circuit 20 of the transistor 19 comprises a trigger control stage 20a providing a trigger control signal S20 at output, applied to the gate 21 of the transistor 19. This trigger control stage 20a comprises the following elements connected in series between the terminal of the contactor 17 furthest from the power supply source 16 and the negative pole of said source 16, corresponding respectively to the positive and negative voltage lines 30b and 30a in [Fig.2]: - a control switch 25, and - a high resistor 24 and a low resistor 23 forming a resistive divider bridge 31 between the positive and negative voltage lines 30b and 30a, the midpoint of which, which is the connection point between the high resistor 24 and low resistor 23, provides the control signal S20.

[0077] The control contactor 25 is thus connected between the positive voltage line 30b and the high resistor 24. The low resistor 23 is connected between the high resistor 24 and the negative voltage line 30a.

[0078] The gate 21 of the transistor 19 is connected to the midpoint of the divider bridge 31 by a connecting wire. Said midpoint of the resistive divider bridge 31 thus defines a voltage output S2o for the gate control of the transistor 19.

[0079] Also, the control circuit 20 comprises an actuator 26 capable of actuating the closing of the control contactor 25, upon receipt of an activation signal E20. The actuator 26 may comprise a coil 26a, a power source 26b for the coil 26a and a control means 26c such as a switch arranged in series between the power source 26b and the coil 26a. This switch is for example switched from an open state to a closed state via a push button by the test operator. Its closing allows the circulation of a current in the coil 26a which triggers the closing of the contactor 25. The actuator 26 is galvanically and physically isolated from the rest of the control circuit 20, in order to guarantee the safety of an operator activating or deactivating the actuator 26.

[0080] As long as the activation signal E20 is not emitted, the control contactor 25 is in an open state, isolating the high resistance 24 from the positive voltage line 30b. The gate 21 of the transistor 19 is then anchored, that is to say pulled to the potential of the negative voltage line 30a of the power supply source 16, by the low resistance 23 of the divider bridge 31. This makes it possible to robustify the device 9 preventing accidental triggering under the effect of possible electromagnetic disturbances at the level of the internal parasitic capacitances of the transistor 19 during the power-up phase.

[0081] When the operator switches the control means 26c to supply the coil 26a, the control contactor 25 adopts a closed position which causes the resistive divider bridge 31 to be energized.

[0082] The source 16 is sized according to the electronic card 12, and the desired test conditions. The low and high resistors 23, 24 are sized accordingly. The source 16 and the resistors 23, 24 of the divider bridge 31 are chosen so that the level of the trigger control signal S20 then applied to the control pin 21 of the transistor 19 is well above the control level normally used to control the transistor 19 in the on (closed) state. This level of the trigger control signal S20 then causes the transistor 19 to avalanche and to close irreversibly. The irreversible nature of the closing prevents the influence of electromagnetic disturbances brought by the wiring wires, which could cause the transistor 19 to open. This irreversible closing results in the short-circuiting of said transistor 19 and the triggering of an electric arc by its explosion.

[0083] In other words, the high resistance 24 of the resistive divider bridge 31 is dimensioned so that, at the step of applying the gate control signal S2o, the voltage between the gate (control pin 21) and the source of the transistor 19 (power pin 22a) has a value well above the maximum gate-source voltage denoted Vgsmax, recommended by the specifications of the manufacturer of the transistor 19 in question, in particular a value 5 to 10 times higher, in order to ensure the avalanche of the transistor 19. If we take the example of a MOSFET type transistor 19, we can for example choose a MOSFET transistor suitable for power electronics applications, the maximum gate-source voltage Vgsmax of which is between 20V and 30V, for example equal to 25V

[0084] The high resistor 24 also makes it possible to limit the current flowing through the control contactor 25 when a fault produced by the electric arc engages a connection of the control pin 21 to the low potential of the control circuit 20. Such a fault can occur in particular when an electrical path to the track 13a is established (for example, when the connection wire between the output S2o of the control circuit 20 and the control pin 21 breaks and comes to rest in contact with the track 13a) while the electric arc is produced between the tracks 13b and 13a. This is then referred to as a fault returning to the control circuit 20. In other words, the high resistor 24 limits the current rating of the control contactor 25.

[0085] Also, the high resistance 24 is sized to be able to be connected in parallel with the power source 16. Indeed, a high resistance 24 that is too high would risk limiting the control dynamics.

[0086] For example, in the case of an application to a field effect transistor, for example a MOSFET, the high resistance 24 is such that its electrical resistance does not exceed the order of magnitude of ten times the value of the equivalent resistance between drain and source of the transistor 19 when it is in the on state, usually noted Rdson. This is a characteristic value of the transistor, indicated in the technical data sheet by the manufacturer.

[0087] The control contactor 25 is sized to withstand the voltage applied by the power supply source 16. The control contactor 25 is also sized to withstand a maximum current that can flow through the high resistance 24.

[0088] The low resistance 23 makes it possible to anchor the control pin 21 to the low potential of the negative voltage line 30a, during the power-up phase of the equipment 10 controlled by the activation of the power contactor 17 until the voluntary activation of the ignition command by the activation signal E20. This setting to low potential allows the evacuation of any voltage at the intermediate point of the resistive divider bridge during the power-up phase of the equipment 10. This prevents any accidental start of the ignition of the electric arc by the device 9 after power-up.

[0089] The low resistor 23 has a value between 1 kilo-Ohm and 10 kilo-Ohm. In addition, the low resistor 23 is sized so as not to be damaged in the case where the control pin 21 of the transistor 19 (and therefore the wire between the control circuit 20 and this pin 21) is inadvertently brought to the positive voltage of the power supply circuit 15 during a fault feedback case as previously described. In other words, it is sized to withstand a certain level of voltage and current without damage.

[0090] The control signal S2o applied to the control pin 21 is at a level such that it generates the irreversible closing of the transistor 19, which causes heating of the transistor 19 via the circulation in the semiconductor part of said transistor 19, between the power pins 22a and 22b, of the current desired in the context of the test and generated by the power supply source 16. This current supplied by the power supply source 16 when the ignition control signal S20 is applied to the control pin 21 is called short-circuit current in the remainder of the text.

[0091] This heating causes the explosion of the transistor 19 and its case 19a, and thus generates the electric arc between the two power pins 22a and 22b.

[0092] The explosion of the transistor 19 starts the electric arc, the plasma of which forms and propagates between the pins 22a, 22b then between the tracks 13a, 13b which are energized. The tracks 13a, 13b then act as electrodes of the arc. The power source 16 connected to the tracks 13a, 13b therefore supplies the electric arc with energy.

[0093] At the end of the test, when the operator opens the control contactor 17 again, the connection between the power supply source 16 and the tracks 13a, 13b is cut, and the electric arc is then no longer powered.

[0094] In more detail, the level of the boot control signal S2o is such that the voltage between the control pin 21 and the power pin 22b connected to the positive pole of the power supply source 16 is greater than the maximum gate-source voltage Vgsmax (characteristic of the transistor 19). This causes the channel of the transistor 19 to be avalanche-fed: the transistor 19 becomes conductive (closes) irreversibly. The process is similar with a transistor 19 of the IGBT transistor type: the control signal S2o causes the channel of the MOSFET transistor, which constitutes the input stage of the IGBT transistor 19, to be avalanche-fed.

[0095] The transistor 19 is then equivalent to a short circuit which then allows all the current delivered by the power source 16 (so-called short-circuit current calibrated by the power source 16) to pass between its power pins 22a and 22b, causing extremely rapid heating leading to the explosion of the transistor 19 and its case 19a. This explosion opens the electrical path, in the semiconductor part of the transistor 19, between the two power pins 22a and 22b.Since the circulating short-circuit current cannot be interrupted instantly upon explosion of the case 19a, the electrons then cross the medium, air or vacuum, between the two power pins 22a, 22b and ionize said medium, resulting in the creation of an electric arc which initially catches between the power pins 22a and 22b of the transistor 19, forming the electrodes of the arc, and which generates a plasma which can extend to the tracks 13a and 13b, themselves becoming in a second time the electrodes of the arc, and more generally which can extend to the entire equipment 10 under test. The electric arc thus initiated and maintained only stops with the opening of the power contactor 17, which cuts off the power supply. The ignition mechanism will be similar regardless of the type of transistor 19, MOSFET or IGBT. .

[0096] The priming is preferably carried out while the power capacitor 14 has been previously charged and the electronic equipment 10 and the power pins 22a and 22b are already powered, so as to reproduce the real operational conditions of the equipment 10 under test.

[0097] Thus the sequence for initiating a short circuit is as follows: - by the action of the control contactor 17 and the power supply source 16, a power-up of the electronic equipment 10 (more precisely of the electronic card 12) under test is carried out, including the charging of the power capacitor 14, and the voltage polarization of the power pins 22a, 22b of the transistor 19; - then, by the action of the contactor 25 via the actuator 26 galvanically isolated from the rest of the control circuit 20, a power supply of the divider bridge 31 is implemented, making it possible to generate a trigger command S20 on the control pin 21 of the transistor 19.

[0098] The electric arc ignition control as proposed has several advantages. As will be understood, with the assembly which has just been described, the control contactor 17 must first be activated so that the control stage 20a driving the control pin 21 of the transistor 19 can be activated by the actuation of the control contactor 25. In this way, it is avoided to inadvertently apply an ignition control signal to the control pin 21 of the transistor 19 before the start of the test, that is to say before the electronic card 12 is powered up, and in particular before the charging of the power capacitor 14 and the polarization of the power pins 22a, 22b of the transistor 19.

[0099] The use of the control contactor 25 as described allows segregation and electrical isolation between the test operator and the source 16, which guarantees the safety of people. The control contactor 25 associated with the resistive divider bridge 31 constitutes a simple and robust control element compared to traditional transistor gate control circuits (called “drivers” according to English terminology).

[0100] The control circuit 20 as described contributes to the robustness of the electric arc control circuit; unlike conventional control circuits, it makes it possible by construction to avoid untimely disturbances (due for example to discharges of the capacitor 14 once charged) likely to cause electromagnetic disturbances likely to cause the controlled striking of the arc to fail.

[0101] In particular, the use of the control contactor 25 and the correctly sized resistors 23 and 24 ensure that the control circuit 20 is not destroyed due to possible current surges in the control circuit 20 during use of the ignition device 9. As a result, the control circuit 20 is reliable and safe. It is also reusable, under the same experimental conditions, for another card, equipped with a new transistor 19. Finally, the ignition of the electric arc is very rapid, of the order of a few microseconds to a millisecond, making the control circuit 20 insensitive to the bounces of the control contactor 25. In practice, the person skilled in the art chooses the high and low resistances of the divider bridge 31 according to the type and technical characteristics of the transistor 19 chosen and for the experimental conditions (short-circuit voltage and current).

[0102] As indicated previously, the device 9 can advantageously comprise a precharging circuit 17P of the power capacitor 14 so as to limit the inrush current. Thus, electromagnetic disturbances are limited in the downstream electronics and the risks of an untimely electric arc striking are avoided.

[0103] The transistor 19 is sized to support between its power pins 22a and 22b, a voltage equal to or greater than that delivered by the source 16 between the electrical tracks 13a and 13b. Thus sized, the transistor 19 cannot fail, in particular find itself in a short-circuit simply because the tracks 13a, 13b are powered up, thus avoiding a risk of accidental ignition by triggering an untimely short-circuit at the level of the transistor 19.

[0104] Transistor 19 is also chosen with a current rating at least ten times lower than the short-circuit current targeted in the experiment, making it possible to ensure the heating conditions allowing the electric arc to strike.

[0105] Also, the transistor 19 conventionally comprises a semiconductor chip encapsulated in a package 19a. Preferably, the package 19a is a dry package, i.e., one devoid of a substance or gel which could cause a bias in the ignition of the electric arc. For example, the package 19a is a TO220 or TO247 type package. Its size will be chosen according to the conditions of the experiment to ensure a sufficiently rapid explosion favorable to the ignition of the arc, while generating sufficient pollution ensuring the development of the electric arc,

[0106] Alternatively, as illustrated in [Fig. 3] (the elements common to the previous embodiment bear the same references), the control circuit 20 comprises a power source 27 which is specific to it, for example an auxiliary power supply such as a battery. The control circuit 20 is then electrically independent of the power supply source 16.As before, the actuator 26 does not have a common electrical reference with the control circuit 20, so as to guarantee galvanic and physical isolation for the safety of the operator. In this embodiment, the power source 27 applies a positive voltage to a terminal of the control contactor 25 opposite the resistive divider bridge 31 and a negative or zero voltage to a terminal of the resistive divider bridge 31 opposite the control contactor 25. This voltage must be high enough so that the control signal applied to the control pin 21 of the transistor 19 causes the definitive closing of the transistor 19 as described with reference to the embodiment illustrated in [Fig.2].In this alternative embodiment, the power pins 22a and 22b of the transistor 19 remain biased by the power source 16 which provides the short-circuit current necessary to initiate the electric arc to heat and explode the transistor 19 when it is permanently closed.

[0107] Furthermore, in this embodiment, the precharge circuit 17P is also necessary, in particular when the power capacitor 14 is a high-value capacitor (several hundred microfarads, for example).

[0108] [Fig.4] illustrates the different steps of a method of striking an electric arc in electronic equipment such as electronic equipment 10.

[0109] In a first step E1, the parameters of the bootstrap circuit are chosen to correspond to the test that one wishes to conduct. More precisely, one chooses the electrical transistor 19 and the resistors 23 and 24 according to the voltage that one wishes to see applied between its pins by the source 16 and the short-circuit current targeted for the experiment: typically, the choice will relate to the nature of the transistor 19 (MOSFET, IGBT), its type of package 19a, and its electrical characteristics, in particular its current and voltage rating specified by the manufacturer, that is to say the maximum current that it can conduct (in normal operating mode) and the maximum voltage applicable between its power pins. In the case of a MOSFET transistor, these characteristics are noted Idsmax, Vdsmax.

[0110] In particular, the transistor 19 is chosen with a dimensioning making it possible to prevent it from disturbing the operation of the equipment 10 as long as the ignition of the electric arc is not triggered. More precisely, the transistor 19 is chosen so as to withstand the voltage applied by the power supply source 16 between the tracks 13a and 13b.

[0111] Furthermore, and to guarantee the ignition of the electric arc, the transistor 19 is chosen so that its nominal current (or current rating) is at least ten times lower than the short-circuit current targeted for the experiment and supplied by the power supply source 16 (or by the power supply source 27 specific to the control circuit 20 where appropriate).

[0112] Also, the choice of the package 19a of the transistor must be made in relation to the conditions defined for the ignition of the electric arc. In particular, the package must not be too large so as not to take too long to explode, nor too small to generate sufficient pollution when exploding to ensure the proper development of the electric arc.

[0113] For example, for an electric arc test targeting a continuous power supply voltage of 540VDC and a short-circuit current of 400A, a MOSFET type transistor is chosen with Vdsmax values ​​of 600V, Idsmax of 15A and Vgsmax of 25 Volts and in a TO220 type package.

[0114] The resistors 23 and 24 of the control circuit 20 are sized according to the chosen transistor 19, in particular so that the voltage at gate 21 and source 22a of the transistor 19 has a value between 5 and 10 times higher than the maximum gate-source voltage Vgsmax specified for the transistor 19 by its manufacturer. The high resistor 24 is also sized so as not to exceed the order of magnitude of ten times the equivalent resistance at drain 22b and source 22a of the transistor 19 when it is in the on state, noted Rdson (indicated by the manufacturer of the transistor 19). The resistor low 23 is of a value between 1 kilo-Ohm and 10 kilo-Ohm. The control contactor 25 is sized to withstand the voltage applied by the source 16, and also to withstand a maximum current that can flow through the high resistor 24.

[0115] Taking the example above, of a MOSFET type transistor 19 in a TO220 type package with a voltage and current rating of 600V and 15A, and a power supply sized to provide a direct voltage of 540VDC and a short-circuit current of 400A as indicated above, the following choices can for example be made:

[0116] - for the low resistance 23, a resistance of 1 kilo Ohm capable of supporting a minimum voltage of 600V and a power of 300W during the duration of use of the device 9;

[0117] - for the high resistance 24, a resistance of 150 Ohm, which corresponds to approximately ten times the apparent on-state resistance, usually denoted RDson of such a transistor 19.

[0118] The voltage at the midpoint of the divider bridge 31 obtained by such a high resistor 24 and such a low resistor 23 is 470 Volts, while the value Vgsmax for the transistor considered is 25 Volts, which ensures good avalanche switching of the channel of the transistor 19.

[0119] In this example, the control contactor 25 will be calibrated in current and voltage to hold at least 600V and 4 A.

[0120] In a step E2, the device 9 for initiating an electric arc is mounted on the electronic equipment 10. More precisely, the transistor 19 of the initiating means 11 is placed on said electronic equipment 10 by fixing the two power pins 22a, 22b on the two tracks or two points of electrical potentials 13a, 13b of said electronic equipment 10.

[0121] The pins 22a and 22b of the transistor 19 of the ignition device are for example fixed by soldering on the tracks 13a, 13b. This allows a mechanically robust fixing, as well as a good electrical connection. This avoids the risk of ejection of the transistor (detachment from the card), due for example to the electrodynamic forces generated by the striking of an arc between the power pins 22a and 22b. Other fixing methods are of course conceivable.

[0122] In a third step E3, the electronic power equipment 10 is powered up by the power supply circuit 15, by closing the power contactor 17. The control contactor 25 is then in the open position of the control circuit 20, the control pin 21 then not being used. Preferably, a precharge circuit 17P of the capacitor 14 is provided, making it possible to limit the inrush current, and it is activated before the power contactor 17. During this step of precharging and powering up the card 12 / the equipment 10, the control circuit 20 is not activated. The control pin 21 of the transistor 19 is pulled to the potential of the negative voltage line 30a by the low resistance 23 of the resistive divider bridge 31 of the control circuit 20.

[0123] After this third step E3, the generation of the activation signal E20 applied to the input of the control circuit 20, causes the control contactor 25 to close, leading to a fourth step E4. In this fourth step E4, the control circuit 20 applies a triggering control signal S2o to the control pin 21, causing the transistor 19 to close, allowing the circulation of a short-circuit current triggering the electric arc. The power contactor 17 and the control contactor 25 are then in the closed position.

[0124] Suitable instrumentation (visualization systems (fast cameras for example), cost and voltage measurements at different points of the electronic equipment, etc.) makes it possible to monitor the behavior of the electronic equipment under the effect of the electric arc and, where appropriate, under the effect of the fire generated by it.

[0125] The priming device and the sample to be tested are, for example, placed in a protective enclosure for the test. This enclosure may also be equipped with a smoke evacuation system.

[0126] Several samples of the same equipment can be tested at different supply voltages. These can also vary depending on the equipment tested.

[0127] Furthermore, in a final step E5, the power contactor 17 is opened. This cuts the electric arc when the experiment is not stopped beforehand by damage caused to the equipment itself during the test. This also allows an operator to intervene in the enclosure safely in order to recover the equipment and, if necessary, make additional observations on it.

[0128] In the description, the electronic equipment 10 considered was a power electronics equipment. The invention is not limited to such an embodiment, and also applies to any other type of electronic equipment. In other words, the control circuit 20 and the transistor 19 are sized to correspond to the supply voltage levels of the electronic equipment 10 considered and the short-circuit current targeted by the experiment.

Claims

Claims

1. Device for initiating an electric arc (9) in electronic equipment (10) in order to test its behavior under the effect of this electric arc and / or under the effect of an electric fire generated by it, a power supply (15) being provided for powering up said equipment establishing a supply voltage between a first electrical track or a first electrical potential point and a second electrical track or a second electrical potential point (13a, 13b) of said equipment, the initiating device (9) comprising: - a transistor (19) comprising two power pins (22a, 22b) and a control pin (21) of a gate of the transistor, the two power pins (22a, 22b) being able to be electrically connected one to the first electrical track or to the first electrical potential point and the other to the second electrical track or second electrical potential point (13a, 13b) of said equipment (10),said transistor being capable of withstanding a voltage between its power pins greater than or equal to said supply voltage and calibrated to pass a current between its two power pins (22a, 22b) lower than the order of 5 to 15 times a current delivered by said power supply (15), and - a control circuit (20) of the transistor electrically isolated from the power supply (15) and configured to apply a trigger control signal (S20) to the control pin (21) capable of causing irreversible closing of the transistor (19) by avalanche effect while the equipment and therefore the first track or the first potential point (13a) on the one hand and the second track or the second potential point (13b) on the other hand are energized, so as to generate an electric arc under the effect of said current delivered by the power supply (15).,

2. Device (9) according to claim 1, in which the power supply (15) of the priming device (9) comprises a power supply source (16) and a power contactor (17) capable: - of being activated in closing to allow the electronic equipment (10) to be powered up prior to the application of the ignition control signal (S20) capable of causing the transistor (19) to close and ignite an electric arc, and - to be activated in opening for switching off said equipment, so as to subsequently cut off the power supply to the electric arc.

3. Device according to claim 2, wherein the electronic equipment (10) comprises at least one capacitor (14) between the first and second electrical tracks (13a and 13b) or first and second electrical potential points, the switching on of the electronic equipment (10) allowing the charging of said capacitor (14).

4. Device (9) according to claim 3, wherein the power supply (15) further comprises a pre-charging circuit (17P) capable of limiting the inrush current when charging the capacitor (14) when switching on the electronic equipment (10).

5. Device (9) according to one of claims 1 to 4, in which the control circuit (20) of the gate of the transistor comprises: - a resistive divider bridge (31) comprising a high resistor (24) and a low resistor (23), a midpoint of the resistive divider bridge between the high resistor (24) and the low resistor (23) forming an output of the control circuit (20) supplying said trigger control signal (S20) on the control pin (21) of the gate of the transistor (19), and - a control contactor (25) connected in series with the resistive divider bridge (31), to control the switching on of said resistive divider bridge in a closed state controlled by an activation signal (E20), to establish a trigger control signal (S20) capable of causing the irreversible closing of the transistor (19) by avalanche effect.

6. Device (9) according to claim 5 in combination with claim 2, wherein the resistive divider bridge (31) of the control circuit (20) is powered by the power supply source (16).

7. Device (9) according to claim 6, in which the control contactor (25) is connected in series with the resistive divider bridge (31) between on the one hand the power contactor (17) which is connected to the pole positive of the power supply source (16) and on the other hand to the negative pole of said source (16).

8. Method for striking an electric arc on electronic equipment (10) with a view to testing its behavior under the effect of this electric arc and / or under the effect of a fire generated by it by means of an electric arc striking device (9) according to one of claims 1 to 7, in which the following steps are implemented: - positioning (E2) on the electronic equipment (10) of a transistor (19) of the electric arc striking device (9), by electrically connecting one of the two power pins (22a, 22b) of the transistor (19) to a first electrical track or a first electrical potential point (13a) of said electronic equipment (10) and the other of the two power pins (22a;22b) of the transistor (19) on a second electrical track or a second electrical potential point (13b) of said equipment (10), - powering up (E3) the electronic equipment (10) and therefore said first and second tracks and / or said first and second potential points (13a, 13b) by a power supply (15), establishing a supply voltage between the power pins (22a and 22b), then, - striking (E4) an electric arc between the two power pins (22a, 22b) of the transistor (19) by application to the gate control pin (21) of the transistor (19), by the control circuit of the electric arc striking device (9), of a control signal (S20) capable of causing irreversible closing of the transistor (19) by avalanche effect such that an electric arc can strike between the two power pins passing a current delivered by said power supply (15) of the equipment.;

9. A method according to claim 8, wherein the powering up (E3) comprises charging a capacitor (14) that the electronic equipment (10) comprises between the first and second electrical tracks (13a, 13b) or first and second points of electrical potential.

10. A method according to claim 9, wherein the capacitor (14) is precharged upon power-up or beforehand by a dedicated precharge device (17P).

11. Use of an electric arc initiating device (9) according to one of claims 1 to 7 for testing the behavior of electronic equipment (10) under the effect of an electric arc and / or under the effect of a fire generated by it, in which the initiating method according to one of claims 8 to 10 is implemented on at least one electronic equipment (10) whose behavior is to be tested.

12. Use according to claim 11, in which the electronic equipment (10) is power equipment equipping or intended to equip aircraft.

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