FR3152080A1 - ELECTRIC POWER CONTACTOR EQUIPPED WITH AN OPTICAL PROTECTION DEVICE - Google Patents

Abstract

The invention relates to an 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) capable of moving 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), - an optical detector (20) arranged inside or near the breaking chamber (15), - an electrical cut-off member (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). Figure for short: Figure 3

Description

ELECTRIC POWER CONTACTOR EQUIPPED WITH AN OPTICAL PROTECTION DEVICE

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

As is known per se, an electrical power contactor having a cut-off chamber for bidirectional direct current 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 moving contact is away from the fixed contacts.

Such an extinguishing chamber is called "double-breaking" because the moving contact separates from two fixed contacts.

When the arc chute opens, an electric arc occurs between the moving contact and each contact zone. These electric arcs are likely to cause a fire if the contactor fails to extinguish them when the circuit is opened.

Furthermore, during a high-value short circuit, the electrical contacts of a contactor are subjected to significant repulsion forces which can cause the moving contact to separate from the fixed contacts. This phenomenon, known as "moving contact levitation", can cause the contacts to weld, leading directly, or during the opening operation of the contactor, to a fire.

In fact, during a short circuit, the Laplace forces oppose the spring that holds the contacts under pressure, so that the contacts move apart from each other. This leads to the creation of an electric arc with a current density such that the contact materials melt and stick together. If the short circuit continues, the heating destroys the contact area leading to a fire. When the contactor is subsequently opened, the problem can also arise in that if the contactor's return spring can only partially move the contacts apart from each other, the electric arc sets in and cannot be interrupted, which also causes a fire.

There shows an electrical circuit 10 comprising an electrical voltage source 11 having an HV+ terminal and an 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. It is possible to detect a short circuit likely to generate a failure by monitoring the voltage 14 downstream of the contactor 13 beyond a nominal opening time of the contactor 13. If the failure is confirmed, then the fault must be able to be identified and eliminated (also called clarified) with a very short response time, typically of the order of ten milliseconds. By "eliminating" or "clarifying" a fault, we mean the act of activating, following detection of the fault, an electrical cut-off device provided in series with the contactor.

There 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 bipolar contactor 13 is capable of establishing or breaking the electrical connection with the two terminals of the electrical circuit 10. For such a circuit, voltage monitoring 14 is more delicate, 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 cut off the current from the circuit and thus mask the problem of the faulty contact. This is due to the fact that the two power contacts are mechanically dependent. This particularity requires a significant number of voltage measurements in order to obtain a complete image of the state of the contacts, which induces a complexity of wiring and associated monitoring.

There is therefore a need for a simple and robust solution for detecting a fault linked to the presence of an electric arc likely to cause a fire, allowing the detection of a fault and the implementation of a backup solution, all in a very short time.

The invention aims to effectively meet this need by proposing an electrical power contactor comprising:
- a cut-off chamber,
- at least one fixed contact arranged 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 moved away from the fixed contact,
- an optical detector located inside or near the interrupting chamber,
- an electrical cut-off device, and
- a control device configured to activate the electrical cut-off device when the duration of an electrical arc detected by the optical detector is greater than a nominal opening response time of the electrical power contactor.

The invention thus makes it possible, thanks to the optical monitoring function of the breaking chamber, to guarantee the detection of a fault in the contactor and effective protection distinct from the main switching function. Indeed, the electric arc generates a broad spectrum light flash having a high light amplitude as well as a duration sufficiently discriminating for the electric arc to be detectable by the optical detector. The invention also has the advantage of being able to be implemented in a simple and robust manner.

According to one embodiment of the invention, the nominal response time upon opening is of the order of 30ms.

According to one embodiment of the invention, the electrical cut-off member is a pyrotechnic switch.

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

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

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 opens.

According to one embodiment of the invention, said electrical power contactor comprises a means for emitting artificial light arranged near the optical detector.

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

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

According to one embodiment of the invention, the electrical cut-off member is electrically mounted in series with the electrical contactor.

The present invention will be better understood and other characteristics and advantages will become apparent upon reading the detailed description which follows, comprising embodiments given for illustrative purposes with reference to the appended figures, presented as non-limiting examples, which may serve to complete the understanding of the present invention and the description of its embodiment and, where appropriate, contribute to its definition, in which:

There , already described, is an electrical diagram illustrating an arc-breaking fault in the case of a single-pole type electrical contactor;

There , already described, is an electrical diagram illustrating an arc-breaking fault in the case of a bipolar type electrical contactor;

There is a diagram of an electrical circuit comprising a single-pole type electrical power contactor provided with an optical protection device according to the present invention;

There is a detailed functional schematic representation of the control device capable of controlling an electrical cut-off device according to the present invention;

There is a detailed functional schematic representation of a variant of a control device of an optical protection device according to the invention integrating a function of detecting the correct operation of the detection chain;

There is an electrical diagram illustrating an alternative embodiment of a single-pole, single-contact power electrical contactor provided with an optical protection device according to the present invention.

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

There 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.

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

The electrical power contactor 13 may be of the electromechanical type. In this case, the movement of the movable contact 17 is controlled by a control member, such as a coil associated with a vane or an electric motor.

In addition, an optical detector 20 is arranged inside or near the extinguishing chamber 15. Indeed, the electric arc can be visible through the material of the extinguishing chamber 15 or, when the latter is not hermetic, through a gap constituted for example by a clearance in the extinguishing chamber 15 or a space provided for this purpose. In this case, the optical detector 20 is arranged outside and near the extinguishing chamber 15 so as to be able to capture the illumination of the electric arc.

The optical detector 20 is chosen from: a phototransistor, a photosensitive resistor, a photodiode or an optical fiber. In particular, the bare optical fiber is a naturally omnidirectional sensor having the advantage of having a large detection surface that is not very sensitive to fouling phenomena, such as soot deposits or metal projections. The optical detection chain, going from the optical detector to the control device, makes it possible to capture and detect the electric flash in a time compatible with the expected time for the fault in the contactor 13 to appear.

An electrical cut-off member 21 is also provided, advantageously taking the form of a pyrotechnic switch called a "pyroswitch" according to English terminology. When the pyrotechnic switch 21 is activated, a pyrotechnic charge makes it possible to open the electrical circuit 10, in particular the electrical connection between the electrical voltage source 11 and the electrical charge 12 quickly and efficiently. The pyrotechnic switch 21 is electrically connected in series with the electrical contactor 13. The activation of the pyrotechnic switch 21 is carried out via a trigger resistor 23 electrically connected to a control device 25 described in more detail below belonging to an electrical circuit distinct from the circuit 10. As a variant, the electrical cut-off member 21 can take the form of an additional contactor, such as an electromechanical contactor.

The control device 25 is configured to activate the electrical cut-off member 21 when the duration of an electric arc is greater than a nominal opening response time of the contactor 13. For this purpose, as can be seen in the , the control device 25 comprises a shaping module 25.1 intended to process, in particular filter, the electrical signal generated by the optical detector 20 to isolate the signal corresponding to the electric arc generated by the contactor 13. In addition, a supervision module 25.2 is able to perform a comparison between the duration of the detection of the electric arc and the nominal opening response time of the contactor 13. A control module 25.3 is able to generate a current flowing through the trigger resistor 23 activating the pyrotechnic switch 21 if necessary, in particular if the duration of detection of the electric arc is greater than the nominal opening response time of the contactor 13.

The nominal operating case of the electrical power contactor 13 is described below. When it closes, the contactor 13 makes it possible to electrically connect the electrical voltage source 11 with the electrical load 12. The contactor 13 is capable of withstanding current flows, as specified in its technical data sheet. When the contactor 13 opens, electric arcs occur between the fixed contacts 16.1, 16.2 and the movable contact 17 having a duration of a few milliseconds. When the counter-electromotive force value of these added arcs reaches the value of the network voltage, then the current is canceled and the electrical circuit 10 is said to be open.

In the event of a fault, when the contactor 13 opens, electric arcs occur between the fixed contacts 16.1, 16.2 and the movable contact 17. However, internal deterioration of the contactor 13 does not allow the electric arcs to reach the counter-electromotive force value allowing the current to be cancelled. 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 of the order of 30 ms, then the device 25 controls the activation of the pyrotechnic switch 21 via the generation of a current through the trigger resistor 23.

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.

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

For this purpose, as illustrated in the , the control device 25 comprises an AND gate 27 receiving as input an opening signal from the contactor 13 and a signal generated by the optical detector 20 shaped by the module 25.1. A monitoring module 28 generates a fault signal if no signal is generated by the optical detector 20 while an opening signal from the contactor 13 is generated.

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 light or an audible signal.

The contactor 13 may also comprise a means 30 for emitting artificial light, such as a light-emitting diode, arranged 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 powered up in order to check 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.

Although the invention has been described for implementation with a single-pole electrical power contactor, it may also be implemented with a two-pole electrical power contactor.

In the embodiment of the , the electrical power contactor 13 comprises a single fixed contact 16.1 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 and an open position in which the movable contact 17 is distant from the fixed contact 16.1. The various elements previously described, namely the optical detector 20, the electrical breaking member 21, and the control device 25 remain unchanged.

Of course, the various features, variants and/or embodiments of the present invention may be combined with each other in various combinations to the extent that they are not incompatible or mutually exclusive.

Furthermore, the invention is not limited to the embodiments described above and provided solely as examples. It encompasses various modifications, alternative forms and other variants that may be envisaged by those skilled in the art within the scope of the present invention and in particular any combinations of the different modes of operation described above, which may be taken separately or in association.

Claims (10)

Electric power contactor (13) comprising:
- a cut-off 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 moved away 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 interrupting 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 electrical arc detected by the optical detector (20) is greater than a nominal opening response time of the electrical power contactor (13). Electrical power contactor according to claim 1, characterized in that the nominal opening response time is of the order of 30 ms. Electrical power contactor according to claim 1 or 2, characterized in that the electrical cut-off member (21) is a pyrotechnic switch. 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. 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). Electrical power contactor according to claim 5, characterized in that the control device (25) is configured to emit a fault signal in the event that no electric arc is detected by the optical detector (20) when the contactor (13) opens. Electrical power contactor according to claim 5 or 6, characterized in that it comprises a means (30) for emitting artificial light arranged near the optical detector (20). Electrical power contactor according to any one of claims 1 to 7, characterized in that it is of the electromechanical type. 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. Electrical circuit according to claim 9, characterized in that the electrical cut-off member (21) is electrically mounted in series with the electrical contactor (13).