ELECTRICAL INSTALLATION WITH SERIES ARC EXCURSION DEVICES

Abstract

The installation (100) comprises: - an electrical source (102); - an electrical load (104); - first and second supply lines (114, 116) connecting the electrical load (104) to the electrical source (102) to supply power to the electrical load (104); - a power contactor (118) located on the first supply line (114). The installation (100) further comprises: - a branch (130) parallel to the first supply line (114), connected between two points (A, B) of the first supply line (114), these two points (A, B) surrounding the power contactor (118); - on this branch (130), an auxiliary contact (132) connected to the power contactor (118) to open and close with the power contactor (118); and - an opening device, based on a current flowing in branch (130), of one of the supply lines (114, 116). Figure for the abbreviation: Fig. 1

Description

Title of the invention: ELECTRICAL INSTALLATION WITH SERIES ARC CUTTING MEANS Technical field of the invention

[0001] The present invention relates to an electrical installation with means for cutting off a series electric arc, as well as to an aircraft comprising such an electrical installation. Technological background

[0002] Vertical take-off and landing (VTOL) aircraft and conventional take-off and landing (CTOL) aircraft with electric or hybrid propulsion constitute a future market with significant prospects and demand in intra-urban and inter-urban transport for goods or people.

[0003] The propulsion of these different platforms is achieved by one or more electric motors, the number varying according to the aircraft architectures. These electric propulsion systems use increasingly higher voltage levels.

[0004] The failure modes of these systems show that the appearance of a series electric arc can have serious consequences on aircraft structures if it is not stopped.

[0005] In an apparatus using propulsive electrical power, one or more of the following functions may be used to provide power to the aircraft: - an energy storage system, for example in the form of batteries, - a battery management system (from the English "Battery Management") System (also known by the acronym BMS) designed to manage the charging and discharging of battery cells, - equipment for distributing and protecting the power supply chain, and - a propulsion converter assembly designed to transform electrical energy into mechanical energy.

[0006] The detection of series electric arcs in an on-board power supply chain, particularly at the level of a contactor, often requires the use of components dedicated to this function, which can be complex.

[0007] It may therefore be desirable to provide an electrical installation with means of series arc interruption, which makes it possible to overcome at least some of the aforementioned problems and constraints. Summary of the invention

[0008] An electrical installation for an aircraft is therefore proposed, comprising: - an electrical source; - an electric charge; - the first and second power lines connecting the electrical load to the power source to electrically supply the electrical load; and - a power contactor located on the first supply line;

[0009] characterized in that it further comprises: - a branch parallel to the first power line, connected between two points of the first power line, these two points surrounding the power contactor; - on this branch, an auxiliary contact connected to the power contactor to open and close with the power contactor; and - an opening device, depending on a current flowing in the branch, of one of the supply lines.

[0010] The invention thus makes it possible to detect the occurrence of a series electric arc between the two points of the first power supply line, and in particular at the power contactor. Indeed, the series electric arc exhibits a voltage drop resulting in a current flowing in the parallel branch. In response to this current, the opening device opens one of the power supply lines, which interrupts the series electric arc, i.e., stops it. Furthermore, when the power contactor is open, the auxiliary contact is also open, thus preventing a current flow that could unintentionally trigger the current interruption system. In fact, with the power contactor open, the electrical source applies a voltage between the two points which, without the auxiliary contact open, would result in an unwanted current flow in the parallel branch.

[0011] The invention may further include one or more of the following optional features, according to any technically possible combination.

[0012] Preferably, the opening device includes a pyrotechnic switch located on one of the supply lines, the pyrotechnic switch having a resistor located on the branch, in series with the auxiliary contact.

[0013] Preferably also, the pyrotechnic switch is designed to cut off the first supply line outside of the two points.

[0014] Preferably also, the auxiliary contact is designed to close later than the power contactor.

[0015] Preferably also, the opening device includes a contactor power located on the first power line or on the second power line.

[0016] Preferably also, the electrical installation further includes a time delay resistor located on the branch, in series with the auxiliary contact.

[0017] Preferably also, the detection device further comprises a current suppression device in the branch, located on the branch in series with the auxiliary contact and designed to prevent current flow in the branch when it has a voltage below a certain tripping threshold and to allow current flow when the voltage is above this tripping threshold.

[0018] Preferably also, the trigger threshold is lower than a voltage that the electrical source is designed to supply.

[0019] Preferably also, the electrical load includes an electric drive machine for a blower of the aircraft.

[0020] An aircraft comprising an electrical installation according to the invention is also proposed. Brief description of the figures

[0021] The invention will be better understood with the aid of the following description, given solely by way of example and made with reference to the accompanying drawings in which: - [Fig. 1] is an electrical diagram of an example of an electrical installation according to the invention, - [Fig.2] is a block diagram of an example of the operating process of the installation of [Fig.1], - Figure 3 reproduces the electrical diagram of Figure 1 in the case of the occurrence of a series electric arc following the melting of a fuse in the electrical installation, and - [Fig.4] reproduces the electrical diagram of [Fig.1] in the case of the appearance of a series electric arc in a power contactor of the electrical installation. Detailed description of the invention

[0022] With reference to [Fig.1], an example of an electrical installation 100 according to the invention will now be described.

[0023] The electrical installation 100 is designed to be part of an aircraft.

[0024] The electrical installation 100 comprises, firstly, an electrical source 102, by For example, a DC power source such as a battery. The power source 102 is thus designed to provide a voltage U, which can be DC.

[0025] The electrical installation 100 further includes an electrical load 104 designed to receive a voltage V, for example direct current. For example, the electrical load 104 includes a stage 106 for smoothing the DC voltage V, a DC / AC voltage converter 108 for converting the smoothed voltage V into an AC voltage and an electric machine 110 for driving a fan 112 of the aircraft (for example a propeller) from the AC voltage.

[0026] The electrical installation 100 further includes first and second supply lines 114, 116 each connecting the electrical load 104 to the electrical source 102 to electrically supply the electrical load 104 from the electrical source 102.

[0027] The electrical installation 100 further includes a power contactor 118 located on one of the supply lines 114, 116. The power contactor 118 has at least one fixed contact and one moving contact designed to make contact with the fixed contact(s) when the power contactor 118 is closed, and to move away from them when the contactor 118 is open. For example, as in the illustrated example, the power contactor 118 is double-break and has two fixed contacts 118F and a moving contact 118M serving as a fixed contact designed to make contact with the two fixed contacts 118F.

[0028] The electrical installation 100 further includes a fuse 120 located on one of the supply lines 114, 116.

[0029] The electrical installation 100 further includes a pyrotechnic switch 122 located on one of the supply lines 114, 116. The pyrotechnic switch 122 includes a guillotine 124, an initializing resistor 126 and a pyrotechnic element (not shown) designed to be triggered by the heat released by the initializing resistor 126.

[0030] The purpose of triggering the pyrotechnic element is to propel the guillotine 124 so that it mechanically cuts the power supply line (the first power supply line in the illustrated example). The initializing resistor 126 is therefore designed to carry a current through it in order to heat up and thus provide the heat necessary to trigger the pyrotechnic element.

[0031] The electrical installation 100 further includes a device 128 for detecting a series electric arc.

[0032] The detection device 128 includes a branch 130 connected between two points A, B of the first power supply line 114. It is between these two points A, B that the detection device 128 is designed to detect a series electric arc. Thus, to monitor the greatest possible length of the first power supply line 114, points A, B are preferably located as close as possible, respectively, to the power source 102 and the power load 104. Therefore, it is possible to detect a series electric arc appearing on the power contactor 118 or a series electric arc caused by cable damage in any section between points A and B, for example appearing as a result of a melting of fuse 120. The pyrotechnic switch 122 can be designed to cut the supply line 114 outside of the two points A, B as illustrated in [Fig.1], but this is not mandatory.

[0033] In the case where the electrical load 104 includes the electric machine 110 coupled to the blower 112, the pyrotechnic switch 122 is preferably designed to cut off the first supply line 114 as close as possible to the electric machine 110. Indeed, the latter can become a generator when it is disconnected from the electrical source 102 and can thus re-supply other loads connected between the supply lines 114, 116.

[0034] The detection device 128 further comprises, in series on branch 130: an auxiliary contact 132, a current suppression device 134, a delay resistor 136, and the initializing resistor 126 of the pyrotechnic switch 122. The order of these elements on branch 130 can be arbitrary, as long as the initializing resistor 126 is the last, i.e., the one closest to point B. The current suppression device 134 in branch 130 is designed to prevent current flow in branch 130 when the voltage is below a certain tripping threshold and to allow current flow when the voltage is above this tripping threshold. For example, it may be a varistor or a transistor voltage suppression device (TVS).

[0035] The auxiliary contact 132 is connected to the power contactor 118 to open and close simultaneously. The connection between the auxiliary contact 132 and the power contact 118 is preferably purely mechanical. Furthermore, the auxiliary contact 132 is preferably designed to close later and open earlier than the power contactor 118.

[0036] When the elements of the first supply line 114 exhibit a negligible voltage drop (as in the illustrated example, where the main contactor 118 has a very low voltage drop), the voltage of the current suppression device 134 is substantially equal to the voltage drop VAb between the two points A and B. In the absence of a series arc between these two points A and B, the voltage drop VAB is primarily due to the voltage drop of the first supply line 114 between the two points A and B. The tripping threshold of the current suppression device 134 is therefore chosen to be higher than the expected voltage drop VAb under normal operation, for example, at least 5 V higher to avoid false alarms. For example, the tripping threshold is chosen to be equal to or lower than the sum of the expected voltage drop VAB under normal operation and the voltage at which a series arc occurs.For example, if there is a voltage drop. The expected voltage during normal operation is at most 5 V, and since the voltage at which a series electric arc appears is 17 V, their sum is 22 V. Thus, the tripping threshold is preferably chosen between 5 V and 22 V, for example, 20 V. Given the voltage drops generally observed in power lines used in aeronautics, the varistor's tripping threshold is preferably at most 30 V.

[0037] The delay resistor 136 limits the current flowing through the initial resistor 126 and thus slows down the heating of the latter. This prevents the pyrotechnic switch 122 from tripping due to a transient series electric arc that disappears spontaneously very quickly after its occurrence. In certain cases, particularly when the inherent delay of the initial resistor 126 is considered sufficient, the delay resistor 136 can be omitted.

[0038] With reference to [Fig.2], an example of a method 200 for operating the electrical installation 100 will now be described.

[0039] The power contactor 118 is initially open, as is the auxiliary contact 132. Thus, the electrical load 104 is disconnected from the electrical source 102, so that its voltage V is zero and no current flows in the supply lines 114, 116. Furthermore, the open state of the auxiliary contact 132 prevents the pyrotechnic switch 122 from tripping unintentionally. Indeed, if the auxiliary contact 132 were not present, the voltage U between points A and B would cause a current to flow in branch 130 and therefore in particular in the initializing resistor 126, which would lead to the tripping of the pyrotechnic switch 122.

[0040] During a step 202, the power contactor 118 is closed. The electrical source 102 supplies electrical power to the electrical load 104 so that a current flows in the supply lines 114, 116.

[0041] During a step 204, after the closing of the power contactor 118, the auxiliary contact 132 closes.

[0042] In the absence of a series arc, the voltage drop on the first supply line 114 is very low. More precisely, the voltage drop across the power contactor 118 is, for example, less than 150 mV, the voltage drop across the fuse 120 is, for example, less than 150 mV, and the voltage drop across the wiring of the first supply line 114 between points A and B is, for example, less than 5 V. Thus, there is a voltage VAb of a few volts at most between points A and B, resulting mainly from the voltage drop in the first supply line 114 between points A and B. In any case, the voltage VAb is lower than the tripping voltage of the current suppression device 134. The latter is therefore in the open state and prevents current flow in branch 128 and thus a triggering of the pyrotechnic switch 122.

[0043] During a step 206, a series arc appears on the first supply line 114, between points A and B. The series arc may, for example, result from the fuse 120 blowing and may appear in place of the fuse 120, as illustrated in [Fig. 3]. Alternatively, the series arc may appear in the power contactor 118 if it is not properly closed. For example, a gap may remain between one of the fixed contacts 118F and the moving contact 118M, and the series arc may then extend into this gap, as illustrated in [Fig. 4].

[0044] As explained in André Thibault's thesis entitled "Study of the maintenance and propagation mechanisms of a short-circuit electric arc between damaged cables in aircraft electrical networks", available on the HAL platform with the identifier tel-01804832, the series electric arc exhibits at its appearance a voltage drop of a few volts, for example of at least 15 V to 20 V.

[0045] The voltage drop of the series electric arc is added to that of the first supply line 114 between points A and B (the other elements having a negligible voltage drop). Furthermore, as the length of the series electric arc increases (for example, when the molten material of the fuse falls or disintegrates), the voltage drop of the series electric arc can increase, and therefore also the voltage drop VAb between points A and B.

[0046] During a step 208, the device 134 becomes conducting because the voltage drop VAb between points A and B exceeds the trigger voltage of the device 134. A current thus flows in the branch 130 and in particular in the initializing resistor 126, which begins to heat up. This current increases over time due to the increasing voltage drop of the series electric arc.

[0047] During a step 210, the heat given off by the initializing resistor 126 becomes high enough to trigger the pyrotechnic switch 122 which cuts off the first supply line 114 and thus stops the series electric arc.

[0048] The suppression by the pyrotechnic switch 122 of the electric arc from a tripping of the fuse 120 makes it possible to avoid reinjecting energy into the network (an effect referred to in English as "windmilling") if the pyrotechnic switch 122 is located near the electrical load 104, in particular the electric propulsion machine 110.

[0049] In particular, when the length between points A and B is not too great, the varistor 132 could be omitted. Indeed, in this case, the voltage drop due to the line length between points A and B becomes small, for example, a few hundred millivolts. Thus, the voltage drop VAB between points A and B, in the absence of a series arc, is small, for example, less than 1 V. This voltage drop VAB certainly creates a current flowing in branch 130, but too small to trigger the pyrotechnic switch 122. On the other hand, in the event of the appearance of a series electric arc between points A and B, the voltage drop VAb becomes high, and the resulting current in branch 130 leads to the triggering of the pyrotechnic switch 122.

[0050] In conclusion, it should also be noted that the invention is not limited to the embodiments described above. It will indeed be apparent to those skilled in the art that various modifications can be made to the embodiments described above, in light of the information just disclosed to them.

[0051] For example, the opening of the first supply line 114 to suppress the series arc could be carried out, for example instead of or in addition to the triggering of the pyrotechnic switch 122, by opening the power contactor 118.

[0052] In addition, the current suppression device 134 could be implemented by an electronic measuring system, instead of the varistor or the TVS.

[0053] In addition, the auxiliary contact 132 could be an electronic or electromechanical switching device.

[0054] In the detailed presentation of the invention given above, the terms used shall not be interpreted as limiting the invention to the embodiments set forth in this description, but shall be interpreted as including all equivalents which can be foreseen by a person skilled in the art by applying their general knowledge to the implementation of the teaching which has just been disclosed to them.

Claims

Claims

1. Electrical installation (100) of an aircraft, comprising: - an electrical source (102); - an electrical load (104); - first and second power supply lines (114, 116) connecting the electrical load (104) to the electrical source (102) to electrically power the electrical load (104); and - a power contactor (118) located on the first power supply line (114); characterized in that it further comprises: - a branch (130) parallel to the first power supply line (114), connected between two points (A, B) of the first power supply line (114), these two points (A, B) surrounding the power contactor (118); - on this branch (130), an auxiliary contact (132) connected to the power contactor (118) to open early and close late relative to the power contactor (118);and - an opening device, depending on a current flowing in the branch (130), of one of the supply lines (114, 116).;

2. Electrical installation (100) according to claim 1, in which the opening device comprises a pyrotechnic switch (122) located on one of the supply lines (114), the pyrotechnic switch (122) comprising a resistor (126) located on the branch (130), in series with the auxiliary contact (132).

3. Electrical installation (100) according to claim 2, wherein the pyrotechnic switch (122) is adapted to cut the first supply line (114, 116) outside the two points (A, B).

4. Electrical installation (100) according to any one of claims 1 to 3, in which the auxiliary contact (132) is designed to close later than the power contactor (118).

5. Electrical installation according to any one of claims 1 to 4, wherein the opening device comprises a power contactor (118) located on the first electrical line (114) or on the second electrical line (116).

6. Electrical installation (100) according to any one of claims 1 to 5, further comprising a time delay resistor (136) located on the branch (130), in series with the auxiliary contact (132).

7. Electrical installation (100) according to any one of claims 1 to 6, in which the detection device (126) further comprises a device (134) for suppressing current in the branch (130), located on the branch (130) in series with the auxiliary contact (132) and designed to prevent current flow in the branch (130) when it has a voltage below a certain trigger threshold and to allow current flow when the voltage is above this trigger threshold.

8. Electrical installation (100) according to claim 7, wherein the trigger threshold is lower than a voltage (U) that the electrical source (102) is designed to provide.

9. Electrical installation (100) according to any one of claims 1 to 8, in which the electrical load (104) comprises an electrical machine (110) for driving a fan (112) of the aircraft.

10. Aircraft comprising an electrical installation (100) according to any one of claims 1 to 9.

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