Electrical apparatus with means for switching series electric arcs
Patent Information
- Application Number
- EP2023821715
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-11-25
- Filing Date
- 2023-11-20
- Publication Date
- 2025-10-01
AI Technical Summary
The detection and mitigation of series electric arcs in aircraft electrical systems pose significant challenges due to their potential to cause structural damage and require complex dedicated components, especially in high-voltage systems used in vertical take-off and landing and conventional aircraft with electric or hybrid propulsion.
An electrical installation with a parallel branch connected between two points of a power line, featuring an auxiliary contact that opens early and closes late relative to the power contactor, and a device that opens one of the power lines in response to a current in the branch, effectively cutting the series electric arc by applying voltage between these points and preventing unwanted current flow.
This solution allows for the detection and immediate cessation of series electric arcs, preventing damage to aircraft structures and ensuring safe operation by using a pyrotechnic switch and current suppression device to manage voltage and current thresholds, thereby avoiding unintended triggering of the current interruption system.
Smart Images
Figure 1.1
Abstract
Description
Description TITLE: ELECTRICAL INSTALLATION WITH SERIES ELECTRIC ARC CUTTING MEANS Technical field of the invention
[0001] The present invention relates to an electrical installation with series electric arc breaking means, as well as to an aircraft comprising such an electrical installation. Technological background
[0002] Vertical take-off and landing (VTOL) 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 carried out by one or more electric motors, the number varying depending on the aircraft architecture. These electric propulsion systems use ever 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 the latter is not stopped.
[0005] In an apparatus using propulsive electric 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 (also referred to by the acronym BMS) intended to manage the charging and discharging of the battery cells, equipment for distributing and protecting the power supply chain, and a propulsion converter assembly intended to transform the electrical energy into mechanical energy.
[0006] Detecting series arcs in an on-board power supply chain, particularly at 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 series electric arc breaking means, which makes it possible to overcome at least some of the aforementioned problems and constraints. Summary of the invention
[0008] There is therefore proposed an electrical installation of an aircraft, comprising: an electrical source; an electrical load; first and second power supply lines connecting the electrical load to the electrical source to electrically supply the electrical load; and a power contactor located on the first power supply line; characterized in that it further comprises: a branch parallel to the first power supply line, connected between two points of the first power supply line, these two points surrounding the power contactor; on this branch, an auxiliary contact connected to the power contactor to open early and close late relative to the power contactor; and a device for opening, as a function of a current flowing in the branch, one of the power supply lines.
[0009] The invention thus makes it possible to detect the appearance of a series electric arc between the two points of the first power supply line, and in particular on the power contactor. Indeed, the series electric arc presents a voltage drop leading to the appearance of a current flowing in the parallel branch. In response to this current, the opening device opens one of the power supply lines, which cuts the series electric arc, i.e. stops it. Furthermore, when the power contactor is open the auxiliary contact is also open, thus preventing a flow of current which could inadvertently cause the current interruption system to be triggered. Indeed, with the power contactor open, the electrical source applies a voltage between the two points which, without the auxiliary contact open, would cause unwanted current flow in the parallel branch.
[0010] The invention may further comprise one or more of the following optional features, in any technically possible combination.
[0011] Preferably, the opening device comprises a pyrotechnic switch located on one of the supply lines, the pyrotechnic switch comprising a resistor located on the branch, in series with the auxiliary contact.
[0012] Also preferably, the pyrotechnic switch is designed to cut the first supply line outside the two points.
[0013] Also preferably, the auxiliary contact is designed to close late with respect to the power contactor.
[0014] Also preferably, the opening device comprises a power contactor located on the first electrical line or on the second electrical line.
[0015] Preferably also, the electrical installation further comprises a time delay resistor located on the branch, in series with the auxiliary contact.
[0016] Also preferably, 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 trigger threshold and to allow current flow when the voltage is above this trigger threshold.
[0017] Also preferably, the trigger threshold is less than a voltage that the electrical source is designed to provide.
[0018] Also preferably, the electrical load comprises an electric machine for driving a fan of the aircraft. An aircraft comprising an electrical installation according to the invention is also proposed. Brief description of the figures
[0019] The invention will be better understood with the aid of the following description, given solely by way of example and with reference to the appended drawings in which: Figure 1 is an electrical diagram of an example of an electrical installation according to the invention, Figure 2 is a block diagram of an example of an operating method of the installation of Figure 1, Figure 3 reproduces the electrical diagram of Figure 1 in the case of the appearance of a series electric arc following the melting of a fuse of the electrical installation, and Figure 4 reproduces the electrical diagram of Figure 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
[0020] With reference to Figure 1, an example of an electrical installation 100 according to the invention will now be described.
[0021] The electrical installation 100 is designed to be part of an aircraft.
[0022] The electrical installation 100 firstly comprises an electrical source 102, for example a continuous electrical source such as a battery. The electrical source 102 is thus designed to provide a voltage U, which may be continuous.
[0023] The electrical installation 100 further comprises an electrical load 104 designed to receive a voltage V, for example direct current. For example, the electrical load 104 comprises a stage 106 for smoothing the direct current voltage V, a direct current / alternating voltage converter 108 for converting the smoothed voltage V into an alternating voltage and an electrical machine 110 for driving a fan 112 of the aircraft (for example a propeller) from the alternating voltage.
[0024] The electrical installation 100 further comprises 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.
[0025] The electrical installation 100 further comprises a power contactor 118 located on one of the supply lines 114, 116. The power contactor 118 comprises at least one fixed contact and one movable contact designed to come into contact with the one or more fixed contacts when the power contactor 118 is closed, and to move away from it when the contactor 118 is open. For example, as in the example illustrated, the power contactor 118 is double-break and comprises two fixed contacts 118F and a movable blade 118M serving as a movable contact designed to come into contact with the two fixed contacts 118F.
[0026] The electrical installation 100 further comprises a fuse 120 located on one of the supply lines 114, 116.
[0027] The electrical installation 100 further comprises a pyrotechnic switch 122 (from the English “pyroswitch”) located on one of the supply lines 114, 116. The pyrotechnic switch 122 comprises a guillotine 124, an initialization resistor 126 and a pyrotechnic element (not shown) designed to be triggered under the effect of the heat released by the initialization resistor 126.
[0028] The purpose of triggering the pyrotechnic element is to propel the guillotine 124 so that the latter mechanically cuts the power supply line (the first power supply line in the illustrated example). The initialization resistor 126 is thus designed to be crossed by a current to heat up and thus provide the heat necessary to trigger the pyrotechnic element.
[0029] The electrical installation 100 further comprises a device 128 for detecting a series electric arc.
[0030] The detection device 128 comprises 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, the points A, B are preferably located as close as possible to the electrical source 102 and the electrical load 104 respectively. Thus, 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 the points A and B, for example appearing following a blown fuse 120. The pyrotechnic switch 122 may be designed to cut the power supply line 114 outside the two points A, B as illustrated in FIG. 1, but this is not mandatory.
[0031] In the case where the electrical load 104 comprises the electrical machine 110 coupled to the blower 112, the pyrotechnic switch 122 is preferably designed to cut the first power supply line 114 as close as possible to the electrical machine 110. Indeed, the latter can become a generator when it is disconnected from the electrical source 102 and can thus repower other loads connected between the power supply lines 114, 116.
[0032] The detection device 128 further comprises, in series on the branch 130: an auxiliary contact 132, a current suppression device 134, a delay resistor 136 and the initialization resistor 126 of the pyrotechnic switch 122. The order of these elements on the branch 130 can be arbitrary, as long as the initialization resistor 126 is the last, that is to say the closest to point B. The current suppression device 134 in the branch 130 is 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. This is for example a varistor or a transient voltage suppression device (TVS).
[0033] The auxiliary contact 132 is connected to the power contactor 118 to open and close with the power contactor 118, and more precisely to open early and close late relative to the power contactor 118. The connection between the auxiliary contact 132 and the power contact 118 is preferably only mechanical.
[0034] When the elements of the first power supply line 114 have a negligible voltage drop (as in the example illustrated, 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 electric arc between these two points A and B, the voltage drop VAB is mainly due to the voltage drop of the first power supply line 114 between the two points A and B. The triggering threshold of the current suppression device 134 is therefore chosen to be greater than the voltage drop VAB expected in normal operation, for example greater than at least 5 V to avoid false detections. For example, the triggering threshold is chosen to be equal to or less than the sum of the voltage drop VAB expected in normal operation and the voltage at which an electric arc appears. series. For example, if the expected voltage drop in normal operation is at most 5 V and the voltage at which a series electric arc occurs is 17 V, their sum is 22 V. Thus, the trigger threshold is preferably chosen between 5 V and 22 V, for example 20 V. With the voltage drops generally observed in power supply lines used in aeronautics, the trigger threshold of the varistor is preferably at most 30 V.
[0035] The delay resistor 136 limits the current flowing through the initialization resistor 126 and therefore slows down the heating of the latter. This makes it possible to avoid triggering the pyrotechnic switch 122 for a transient series electric arc which spontaneously disappears very quickly after its occurrence. In certain cases, in particular when the delay inherent in the initialization resistor 126 is deemed sufficient, the delay resistor 136 may be omitted.
[0036] With reference to FIG. 2, an example method 200 of operating the electrical installation 100 will now be described.
[0037] 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 untimely triggering of the pyrotechnic switch 122. Indeed, if the auxiliary contact 132 were not present, the voltage U present between the points A and B would cause a current to flow in the branch 130 and therefore in particular in the initialization resistor 126 which would lead to the triggering of the pyrotechnic switch 122.
[0038] During a step 202, the power contactor 118 is closed. The electrical source 102 electrically supplies the electrical load 104 so that a current flows in the power supply lines 114, 116.
[0039] During a step 204, after closing the power contactor 118, the auxiliary contact 132 closes.
[0040] In the absence of a series arc, the voltage drop on the first power supply line 114 is very low. More specifically, the voltage drop of the power contactor 118 is for example less than 150 mV, the voltage drop of the fuse 120 is for example less than 150 mV and the voltage drop of 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 less than the trigger voltage of the current suppression device 134. The latter is therefore in the open state and prevents current flow in the branch 128 and therefore triggering of the pyrotechnic switch 122.
[0041] During a step 206, a series electric arc appears on the first power supply line 114, between points A and B. The series electric arc for example follows a blowing of the fuse 120 and appears in place of the fuse 120, as illustrated in FIG. 3. Alternatively, the series electric 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 movable blade 118M, the series electric arc then extending into this gap, as illustrated in FIG. 4.
[0042] 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 presents at its appearance a voltage drop of a few volts, for example at least 15 V to 20 V.
[0043] The voltage drop of the series 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 arc increases (for example, when the molten material of the fuse falls or otherwise disintegrates), the voltage drop of the series arc may increase, and therefore also the voltage drop VAB between points A and B.
[0044] During a step 208, the device 134 becomes conductive 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 initialization resistor 126 which begins to heat up. This current increases over time due to the increase in the voltage drop of the series electric arc.
[0045] During a step 210, the heat released by the initialization resistor 126 becomes high enough to trigger the pyrotechnic switch 122 which cuts the first power supply line 114 and thus stops the series electric arc.
[0046] The suppression by the pyrotechnic switch 122 of the electric arc originating from a triggering of the fuse 120 makes it possible to avoid reinjecting energy into the network (effect referred to in English as “windmilling”) if the pyrotechnic switch 122 is located near the electrical load 104, in particular the electrical propulsion machine 110.
[0047] Particularly when the length between points A and B is not too long, the varistor 132 could be omitted. Indeed, in this case, the voltage drop due to the line length between points A and B becomes low, for example a few hundred millivolts. Thus, the voltage drop VAB between points A and B, in the absence of a series electric arc, is low, for example less than 1 V. This voltage drop VAB certainly creates a current flowing in the branch 130, but too low 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 the branch 130 leads to the triggering of the pyrotechnic switch 122.
[0048] In conclusion, it will also be noted that the invention is not limited to the embodiments described above. It will indeed appear to those skilled in the art that various modifications can be made to the embodiments described above, in light of the teaching which has just been disclosed to them.
[0049] 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.
[0050] Furthermore, the current suppression device 134 could be implemented by an electronic measuring system, instead of the varistor or TVS.
[0051] Furthermore, the auxiliary contact 132 could be an electronic or electromechanical switching device.
[0052] In the detailed presentation of the invention given above, the terms used should not be interpreted as limiting the invention to the embodiments set forth in this description, but should be interpreted to include all equivalents which can be predicted by a person skilled in the art by applying his general knowledge to the implementation of the teaching which has just been disclosed to him.
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 a device for opening, as a function of a current flowing in the branch (130), 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, in which 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 supply. [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.