Electrical power contactor provided with an optical protection device

Abstract

The invention relates to an electrical power contactor (13) comprising: - a quenching chamber (15), - at least one fixed contact (16.1, 16.2) placed inside the quenching chamber (15), and - a movable contact (17) able to move between: - a closed position in which the movable contact (17) makes contact with the fixed contact (16.1, 16.2), - an open position in which the movable contact (17) is moved away from the fixed contact (16.1, 16.2), - an optical detector (20) placed inside or near the quenching chamber (15), - an electrical quenching member (21), and - a control device (25) configured to activate the electrical quenching member (21) when a duration of an electric arc detected by the optical detector (20) is greater than a response time to nominal opening of the electrical power contactor (13).

Description

DESCRIPTION TITLE: POWER ELECTRICAL CONTACTOR EQUIPPED WITH AN OPTICAL PROTECTION DEVICE

[0001] The present invention relates to a power electrical contactor equipped with an optical protection device. The invention finds a particularly advantageous, but not exclusive, application in the field of aeronautics with contactors used with aircraft propulsion electric motors operating at high DC voltage levels of several hundred volts.

[0002] As is well known, a power electrical contactor with a bidirectional DC breaking chamber generally comprises: - two fixed contacts, and - a movable contact designed to move between: a closed position in which the movable contact is in contact with the fixed contacts, and an open position in which the movable contact is away from the fixed contacts.

[0003] Such a breaking chamber is called "double breaking" because the moving contact separates from two fixed contacts.

[0004] When the breaking chamber opens, an electric arc occurs between the moving contact and each contact zone. These electric arcs can generate a fire if the contactor fails to extinguish them when the circuit is opened.

[0005] Furthermore, during a high-voltage short circuit, the electrical contacts of a contactor are subjected to significant repulsive forces that can cause the moving contact to separate from the fixed contacts. This phenomenon, known as "moving contact levitation," can cause a soldering of contacts leading directly, or during the operation of opening the contactor, to a fire starting.

[0006] Indeed, during a short circuit, Laplace forces oppose the spring that maintains pressure between the contacts, causing them to separate. This leads to the creation of an electric arc with a current density so high that the contact materials melt and fuse together. If the short circuit persists, the heat destroys the contact area, leading to a fire. The problem can also arise when the contactor is subsequently opened, because if the contactor's return spring can only partially separate the contacts, the electric arc will ignite and cannot be extinguished, also resulting in a fire.

[0007] Figure 1 shows an electrical circuit 10 comprising an electrical voltage source 11 having a high-voltage (HV+) terminal and a high-voltage (HV-) terminal. The electrical voltage source 11 is connected to an electrical load 12. A single-pole contactor 13 is electrically connected in series with the electrical load 12. A short circuit likely to cause a fault can be detected by monitoring the voltage 14 downstream of the contactor 13 beyond its nominal opening time. If the fault is confirmed, it must be possible to identify and clear it (also called "resolve") with a very short response time, typically on the order of ten milliseconds. Clearing or "resolving" a fault means activating, after the fault is detected, an electrical switching device connected in series with the contactor.

[0008] Figure 2 shows an electrical circuit 10 comprising electrical voltage sources 11.1, 11.2 electrically connected to a common ground and having an HV+ terminal and an HV- terminal. A double-pole contactor 13 is suitable for establishing or breaking the electrical connection with the two terminals of the electrical circuit 10. For such a circuit, voltage monitoring 14 is more complex, because if one of the power contacts is faulty but the second is operational, there is a hidden fault, since during opening, the functional contact will interrupt the circuit current and thus mask the fault in the other contact. faulty. This is due to the fact that the two power contacts are mechanically interdependent. This characteristic necessitates a significant number of voltage measurements to obtain a complete picture of the contact condition, resulting in complex wiring and associated monitoring.

[0009] Therefore, there is a need for a simple and robust solution for detecting a failure related to the presence of an electric arc that could cause a fire, allowing for the detection of a fault and the implementation of a backup solution, all in a very short time.

[0010] The invention aims to effectively meet this need by proposing a power electrical contactor comprising: - a cut-off chamber, - at least one fixed contact located inside the breaking chamber, and - a mobile contact capable of moving between: - a closed position in which the moving contact is in contact with the fixed contact, - an open position in which the moving contact is away from the fixed contact, - an optical detector located inside or near the cut-off chamber, - an electrical disconnect device, and - a control device configured to activate the electrical disconnect device when the duration of an electric arc detected by the optical detector is greater than the nominal opening response time of the power electrical contactor.

[0011] The invention thus enables, through the optical monitoring function of the breaking chamber, the detection of a contactor fault and effective protection separate from the main switching function. Indeed, the electric arc generates a broad-spectrum flash of light with a high amplitude and a duration sufficiently distinct to allow the electric arc to be detected by the optical sensor. The invention also has the advantage of being simple and robust to implement.

[0012] According to one embodiment of the invention, the nominal opening response time is on the order of 30ms.

[0013] According to one embodiment of the invention, the electrical cutting-off device is a pyrotechnic switch.

[0014] According to one embodiment of the invention, the optical detector is chosen from a phototransistor, a photosensitive resistor, a photodiode or an optical fiber.

[0015] According to one embodiment of the invention, the control device is configured to implement a function of monitoring the proper functioning of a detection chain going from the optical detector to the control device.

[0016] According to one embodiment of the invention, the control device is configured to emit a fault signal in the event that no electric arc is detected by the optical detector when the contactor is opened.

[0017] According to one embodiment of the invention, said electrical power contactor includes a means for emitting artificial light disposed near the optical detector.

[0018] According to one embodiment of the invention, said electrical power contactor is of the electromechanical type.

[0019] The invention also relates to an electrical circuit comprising an electrical voltage source, an electrical load and a power electrical contactor as previously defined.

[0020] According to one embodiment of the invention, the electrical switching device is electrically mounted in series with the electrical contactor.

[0021] The present invention will be better understood, and other features and advantages will become apparent, upon reading the following detailed description, which includes embodiments given by way of illustration with reference to the accompanying figures, presented by way of non-limiting examples, which may to serve to complete the understanding of the present invention and the description of its implementation and, where appropriate, to contribute to its definition, on which:

[0022] [Fig.1] Figure 1, already described, is an electrical diagram illustrating an arc interruption fault in the case of a single-pole type electrical contactor;

[0023] [Fig.2] Figure 2, already described, is an electrical diagram illustrating an arc interruption fault in the case of a bipolar type electrical contactor;

[0024] [Fig. 3] Figure 3 is a diagram of an electrical circuit comprising a single-pole type electrical power contactor equipped with an optical protection device according to the present invention;

[0025] [Fig. 4] Figure 4 is a detailed functional schematic representation of the control device capable of controlling an electrical switching device according to the present invention;

[0026] [Fig. 5] Figure 5 is a detailed functional schematic representation of a variant of a control device for an optical protection device according to the invention incorporating a function for detecting the proper functioning of the detection chain;

[0027] [Fig. 6] Figure 6 is an electrical diagram illustrating an alternative embodiment of a single-pole, single-contact electrical power contactor equipped with an optical protection device according to the present invention.

[0028] It should be noted that, in the figures, structural and / or functional elements common to the different embodiments may have the same reference numbers. Thus, unless otherwise stated, such elements have identical structural, dimensional, and material properties.

[0029] Figure 3 shows an electrical circuit 10 comprising an electrical voltage source 11 having an HV+ terminal and an HV- terminal and connected to an electrical load 12. In this case, the electrical voltage source 11 is a high voltage direct current source.

[0030] A power electrical contactor 13 is electrically connected in series with the electrical load 12. The power electrical contactor 13 has a breaking chamber 15, and separable contacts, in the example two fixed contacts 16.1, 16.2 and a moving contact 17. The two fixed contacts 16.1, 16.2 are arranged inside the breaking chamber 15. The moving contact 17 is able to move between a closed position in which the moving contact 17 is in contact with the fixed contacts 16.1, 16.2, respectively in the first and second contact zones, and an open position in which the moving contact 17 is away from the fixed contacts 16.1, 16.2.

[0031] The electrical power contactor 13 can be of the electromechanical type. In this case, the movement of the moving contact 17 is controlled by a control element, such as a coil associated with a paddle or an electric motor.

[0032] Furthermore, an optical detector 20 is positioned inside or near the cutoff chamber 15. Indeed, the electric arc may be visible through the material of the cutoff chamber 15 or, if the chamber is not airtight, through a gap, such as a space within the cutoff chamber 15 or a space specifically designed for this purpose. In this case, the optical detector 20 is positioned outside and near the cutoff chamber 15 so as to detect the illumination of the electric arc.

[0033] The optical detector 20 is selected from among: a phototransistor, a photosensitive resistor, a photodiode, or an optical fiber. In particular, bare optical fiber is a naturally omnidirectional sensor with the advantage of offering a large detection area that is relatively insensitive to fouling phenomena, such as soot deposits or metallic spatter. The optical detection chain, from the optical detector to the control device, enables the capture and detection of the electrical flash within a time frame compatible with the expected time for the fault to occur in contactor 13.

[0034] An electrical cut-off device 21 is also planned, advantageously taking the form of a pyrotechnic switch called a "pyroswitch". According to Anglo-Saxon terminology, when the pyrotechnic switch 21 is activated, a pyrotechnic charge opens the electrical circuit 10, specifically the electrical connection between the voltage source 11 and the electrical load 12, quickly and efficiently. The pyrotechnic switch 21 is electrically connected in series with the electrical contactor 13. Activation of the pyrotechnic switch 21 is achieved via a tripping resistor 23 electrically connected to a control device 25, described in more detail below, which belongs to an electrical circuit separate from the circuit 10. Alternatively, the electrical breaking element 21 can take the form of an additional contactor, such as an electromechanical contactor.

[0035] The control device 25 is configured to activate the electrical disconnect device 21 when the duration of an electric arc exceeds the nominal opening response time of the contactor 13. To this end, as shown in Figure 4, the control device 25 includes a shaping module 25.1 for processing, in particular filtering, the electrical signal generated by the optical detector 20 to isolate the signal corresponding to the electric arc generated by the contactor 13. Furthermore, a monitoring module 25.2 is capable of comparing the duration of the electric arc detection with the nominal opening response time of the contactor 13. A control module 25.3 is capable of generating a current flowing through the tripping resistor 23, activating the pyrotechnic switch 21 when necessary, particularly if the duration of the electric arc detection exceeds the nominal opening response time of the contactor 13.

[0036] The nominal operating condition of the power electrical contactor 13 is described below. When closed, the contactor 13 electrically connects the voltage source 11 to the electrical load 12. The contactor 13 is capable of withstanding current flows, as specified in its datasheet. When the contactor 13 opens, electrical arcs occur between the fixed contacts 16.1, 16.2 and the moving contact 17, lasting for a few milliseconds. When the combined back electromotive force (EMF) of these arcs reaches the value of the network voltage then the current is zero and the electrical circuit 10 is said to be open.

[0037] In the event of a fault, when the contactor 13 opens, electric arcs occur between the fixed contacts 16.1, 16.2 and the moving contact 17. However, internal damage to the contactor 13 prevents the electric arcs from reaching the back electromotive force (EMF) value required to cancel the current. If the optical detector 20 detects that the duration of the electric arc is greater than the nominal opening response time of the contactor 13, typically on the order of 30 ms, then the device 25 triggers the pyrotechnic switch 21 by generating a current through the tripping resistor 23. "On the order of" means a variation of plus or minus 10% from the specified value.

[0038] The control device 25 can also be configured to implement a function of monitoring the proper operation of a detection chain going from the optical detector 20 to the control device 25.

[0039] The control device 25 is configured to emit a fault signal in the event that no electric arc is detected when the contactor 13 is opened.

[0040] For this purpose, as illustrated in Figure 5, the control device 25 includes an ET gate 27 which receives as input an opening signal SO from the contactor 13 and a signal generated by the optical detector 20. The signal generated by the optical detector 20 can be shaped, in particular filtered, by module 25.1. Alternatively, the signal generated by the optical detector 20 is applied directly to the input of the ET gate 27. A monitoring module 28 generates a fault signal if no signal is generated by the optical detector 20 while an opening signal SO from the contactor 13 is generated. The ET gate 27, modules 25.1, 25.2, 25.3, and the monitoring module 28 can be either electronic or software modules.

[0041] The fault signal can be sent to a maintenance module (not shown) which reports the presence of an anomaly to the user via a human-machine interface, such as a screen, or a fault indicator or an audible signal.

[0042] The contactor 13 may also include a means 30 for emitting artificial light, such as a light-emitting diode, positioned near the optical detector 20 so as to illuminate it. The emitting means 30 is capable of generating artificial light when the electrical circuit 10 is energized in order to verify the integrity of the detection chain. If the artificial light generated by the emitting means 30 is detected by the optical detector 20, then the detection chain is considered to be functional. If the artificial light generated by the emitting means 30 is not detected by the optical detector 20, then the detection chain is considered to be faulty.

[0043] Although the invention has been described for implementation with a single-pole power electrical contactor 13, it can also be implemented with a two-pole power electrical contactor.

[0044] In the embodiment of Figure 6, the electrical power contactor 13 comprises a single fixed contact 16.1 disposed inside the breaking chamber 15 and a movable contact 17 designed to move between a closed position in which the movable contact 17 is in contact with the fixed contact 16.1 and an open position in which the movable contact 17 is away from the fixed contact 16.1. The various elements previously described, namely the optical detector 20, the electrical breaking element 21, and the control device 25, remain unchanged.

[0045] Of course, the different features, variants and / or embodiments of the present invention can be combined with each other in various ways as long as they are not incompatible or mutually exclusive.

[0046] Furthermore, the invention is not limited to the embodiments described above and provided solely by way of example. It encompasses various modifications, alternative forms, and other variations that a person skilled in the art may envision within the scope of the present invention, and in particular all combinations of the different modes of operation described above, which may be considered separately or in combination.

Claims

CLAIMS 1. Electrical power contactor (13) comprising: - a breaking chamber (15), - at least one fixed contact (16.1, 16.2) arranged inside the breaking chamber (15), and - a movable contact (17) designed to move between: - a closed position in which the movable contact (17) is in contact with the fixed contact (16.1, 16.2), - an open position in which the movable contact (17) is distant from the fixed contact (16.1, 16.2), characterized in that said electrical power contactor (13) further comprises: - an optical detector (20) arranged inside or near the breaking chamber (15), - an electrical cut-off device (21), and - a control device (25) configured to activate the electrical cut-off member (21) when a duration of an electric arc detected by the optical detector (20) is greater than a nominal opening response time of the electrical power contactor (13), - the control device (25) being configured to emit a fault signal in the case where no electric arc is detected by the optical detector (20) when the contactor (13) opens, said control device (25) comprising an AND gate (27) receiving as input an opening signal from the contactor (13) and a signal generated by the optical detector (20), and a monitoring module (28) generating a fault signal if no signal is generated by the optical detector (20) while a signal for opening the contactor (13) is generated.

2. Electrical power contactor according to claim 1, characterized in that the nominal opening response time is of the order of 30 ms.

3. Electrical power contactor according to claim 1 or 2, characterized in that the electrical cut-off member (21) is a pyrotechnic switch.

4. Electrical power contactor according to any one of claims 1 to 3, characterized in that the optical detector (20) is chosen from a phototransistor, a photosensitive resistor, a photodiode or an optical fiber.

5. Electrical power contactor according to any one of claims 1 to 4, characterized in that the control device (25) is configured to implement a function of monitoring the correct operation of a detection chain going from the optical detector (20) to the control device (25).

6. Electrical power contactor according to claim 5, characterized in that it comprises a means (30) for emitting artificial light arranged near the optical detector (20).

7. Electrical power contactor according to any one of claims 1 to 6, characterized in that it is of the electromechanical type.

8. Electrical circuit (10) comprising an electrical voltage source (11), an electrical load (12) and an electrical power contactor (13) defined according to any one of the preceding claims.

9. Electrical circuit according to claim 8, characterized in that the electrical cut-off member (21) is electrically mounted in series with the electrical contactor (13).

Images