Power contactor comprising a pyrotechnic actuator

Abstract

The invention relates to a power contactor (100) comprising: - a fixed portion; - a movable portion that is able to come into contact with the fixed portion and to move between an open position and a closed position of the contactor, the movable portion comprising at least one power contact (110); - an auxiliary contact (120) and a pyrotechnic actuator (130), the auxiliary contact and the pyrotechnic actuator being positioned in parallel with the power contact, and the pyrotechnic actuator being configured to trip when the contactor is lifted in such a way as to move the contactor to the open position; and - a motor configured to actuate the movable portion and bring it into contact with the fixed portion, characterised in that the power contact and the auxiliary contact are desynchronised such that, when the contactor is closed, the power contact comes into contact with the fixed portion before the auxiliary contact and, when the contactor is open, the auxiliary contact opens before the power contact.

Description

Technical Field

[0001] The present invention relates to the general field of electrical protection devices, such as electromechanical contactors and electrical contactors, and more particularly to the opening triggering of these protection devices. Prior art

[0002] Power contactors are electrical protection devices generally made up of a fixed part and a moving part which may or may not be in contact with the fixed part.

[0003] To close a contactor, and therefore put the moving part in contact with the fixed part so that an electric current can flow between the fixed part and the moving part, the contactor motor is powered which will allow a force to be applied to the moving part, and thus allow the flow of an electric current between the moving part and the fixed part.

[0004] When the current flowing between the two parts exceeds the defined threshold, electromagnetic repulsion forces will be applied to the moving part and compensate for, or even exceed, the force applied by the motor to the moving part. This leads to levitation of the contactor, i.e. an unwanted opening of the contactor between the fixed and moving parts. In addition, during this phase, i.e. during the application of the repulsion forces before levitation, the contact resistance between the fixed and moving parts of the contactor increases and creates local heating (proportional to the squared contact resistance multiplied by the current) which can lead to the destruction of the moving part, irreversible damage to the contactor and / or welding of the moving part to the fixed part if the moving part falls back onto the fixed part.

[0005] Currently, to avoid damage to contactors in the event of overcurrent or short circuits, several solutions exist: Measurements of the current flowing in the circuit are made and a processing means detects currents above a predetermined threshold to open the contactor before it levitates. However, the measurement acquisition, processing and action times are not always compatible with the current dynamics which can be extremely fast depending on the impedance of the source or the short circuit. The contactor can include a disconnecting element but this complicates the structure of the contactor. The opening of the contactor can be triggered by a fast actuation means, for example of the pyro-switch type, but the actuation and current detection system can also be too slow depending on certain current dynamics.

[0006] It is therefore desirable to have a new power contactor with accelerated opening triggering and reduced risks of damage in the event of overcurrent.

[0007] Document FR 3 101 478 A1 discloses a power contactor according to the preamble of claim 1. Statement of the invention

[0008] The invention relates to a power contactor comprising: a fixed part; a movable part capable of coming into contact with the fixed part and of moving between an open position and a closed position of the contactor, the movable part comprising at least one power contact; an auxiliary contact and a pyrotechnic actuator, the auxiliary contact and the pyrotechnic actuator being placed in parallel with the power contact, and the pyrotechnic actuator being configured to be triggered during levitation of the contactor so as to move the contactor into the open position, and a motor configured to actuate the movable part and bring it into contact with the fixed part, characterized in that the power contact and the auxiliary contact are desynchronized so that when the contactor closes, the power contact comes into contact with the fixed part before the auxiliary contact and when the contactor opens, the auxiliary contact opens before the power contact.

[0009] The presence of the pyrotechnic actuator allows the power contact to be opened quickly, for example in less than 2 milliseconds, in the event of the contactor levitating.

[0010] By desynchronizing the power contact and the auxiliary contact, the pyrotechnic actuator can be powered via the auxiliary contact without the risk of triggering or melting the pyrotechnic actuator during nominal operation of the contactor. Thus, it is possible to use the contactor of the invention with a high voltage source, for example a source delivering a voltage of 800 V.

[0011] According to a particular characteristic of the invention, the contactor also comprises a transient voltage suppression diode in parallel with the pyrotechnic actuator.

[0012] The transient voltage suppression diode, also called transil diode or transzorb diode, limits the voltage at the terminals of the pyrotechnic actuator and protects it in cases where the voltage increases too quickly at the terminals of the power contact.

[0013] According to another particular characteristic of the invention, the pyrotechnic actuator comprises an igniter and a piston, the igniter being configured to trigger the pyrotechnic actuator by melting and release the piston to open the contactor.

[0014] Another object of the invention is a method of closing a power contactor in the open position according to the invention, comprising bringing the power contact into contact with the fixed part and then bringing the auxiliary contact into contact with the fixed part.

[0015] Another object of the invention is a method of opening a power contactor in the closed position according to the invention, comprising opening the contact between the auxiliary contact and the fixed part, then opening the contact between the power contact and the fixed part.

[0016] Thanks to the closing method of the invention, when the power contact is closed, the current flows in this contact and not in the pyrotechnic actuator. The voltage in the branch comprising the power contact is equal to the voltage drop of the power contact (of the order of a hundred millivolts). Then when the auxiliary contact closes, a small part of the current flows in the pyrotechnic actuator, because the voltage is imposed by the parallel branch comprising the power contact. This current is therefore not sufficient to trigger the pyrotechnic actuator.

[0017] When the contactor opens, the auxiliary contact opens first to isolate the pyrotechnic actuator, then the power contact opens and electric arcs are created. The voltage gradually increases in the two branches parallel to the voltage of the electrical source connected to the contactor, but the voltage across the pyrotechnic actuator remains low.

[0018] When the contactor is closed, i.e. the power and auxiliary contacts are closed, and the electrical current is too high, it is possible for the contactor to levitate, i.e. the power contact to lift. Electric arcs can be created and an arc voltage appears. The current in the branch containing the pyrotechnic actuator increases and triggers the pyrotechnic actuator which will open the power contact. By opening the power contact when the contactor is levitating, we prevent, among other things, the power contact from closing and welding to the fixed part due to the local heating created by the increase in current, which limits damage to the contactor. Brief description of the drawings

[0019] Other characteristics and advantages of the present invention will emerge from the description given below, with reference to the appended drawings which illustrate exemplary embodiments thereof which are not limiting in nature. [ Fig. 1A ] There figure 1A represents, schematically and partially, a power contactor in the open position according to an embodiment of the invention. Fig. 1B ] There figure 1B represents, schematically and partially, a power contactor between an open position and a closed position according to an embodiment of the invention. Fig. 1C ] There figure 1C represents, schematically and partially, a power contactor in the closed position according to an embodiment of the invention. Fig. 1D ] There figure 1D represents, schematically and partially, a power contactor in the open position according to one embodiment. Fig. 2 ] There figure 2 represents, schematically and partially, a power contactor in the open position following the triggering of the pyrotechnic actuator according to an embodiment of the invention. Fig. 3 ] There figure 3 schematically represents a method of closing a power contactor according to one embodiment of the invention. Fig. 4 ] There figure 4 schematically represents a method of opening a power contactor according to one embodiment of the invention. Description of the embodiments

[0020] THE figures 1A, 1B , 1C, 1D And 2 represent, schematically and partially, a power contactor 100 in different positions: in the open position, during nominal operation of the contactor, in figures 1A And 1D , in the closed position in figure 1C , between an open and closed position in figure 1B and in the open position in figure 2 following the triggering of the pyrotechnic actuator 130. In these figures, the objects are designated by the same numerical reference.

[0021] The power contactor 100 comprises a fixed part 108 and a movable part 109 capable of coming into contact with the fixed part and of moving between an open position and a closed position of the contactor 100. The movable part of the contactor 100 comprises a movable power contact 110, an auxiliary contact 120. The contactor 100 also comprises a pyrotechnic actuator 130 comprising an igniter. The auxiliary contact 120 and the pyrotechnic actuator 130, and more particularly the auxiliary contact 120 and the igniter (i.e. the trigger) of the pyrotechnic actuator 130 are placed in parallel with the movable power contact 110. In addition, the movable part may also comprise a resistor 140 placed in series between the auxiliary contact 120 and the pyrotechnic actuator 130.

[0022] The pyrotechnic actuator 130 is configured to trigger during levitation of the contactor 100, i.e. during the formation of electric arcs between the moving part and the fixed part and the lifting of the moving part when the electric current passing through the contactor 100 is too high, so as to directly strike the entire moving part 109 or the moving power contact 110 alone to open the contactor 100. For example, the pyrotechnic actuator 130 can be configured to trigger at currents greater than or equal to 10 A.

[0023] The contactor 100 also includes a motor 170, shown in the figure 1D , configured to actuate the moving part and bring it into contact with the fixed part. The motor is, for example, a linear displacement mechanical motor.

[0024] An electrical load 160 can be connected to the contactor 100. The contactor 100 can be placed between a voltage source 150 and a load 160. The voltage source 150 can be a high voltage source which delivers, for example, a voltage of 800 V.

[0025] In the open position in nominal operation of the contactor 100, shown in figure 1A , the fixed part and the moving part are not in contact and no electric current flows between the two. In other words, the auxiliary contacts 120 and power 110 are open and no electric current can flow between the source 150 and the load 160. The voltage ΔU in the two branches (the one comprising the power contact 110 and the one comprising the auxiliary contact 120 and the pyrotechnic actuator 130) of the contactor 100 is equal to that of the voltage source 150.

[0026] When the contactor 100 closes, the power 110 and auxiliary 120 contacts do not close at the same time. More particularly, the power contact 110 comes into contact with the fixed part of the contactor 100 before the auxiliary contact 120 when the contactor 100 closes. Similarly, when the contactor 100 opens, the power 110 and auxiliary 120 contacts do not open at the same time. More particularly, the auxiliary contact 120 opens before the power contact 110. In other words, the power 110 and auxiliary 120 contacts are out of sync. This state of the contactor 100, between opening and closing, is illustrated in the figure 1B .

[0027] The desynchronization of the power contact 110 and the auxiliary contact 120 is for example achieved by placing these contacts at different distances from the fixed part 108. In the open position of the contactor, the power contact is for example placed at a distance d1 from the fixed part and the auxiliary contact is placed at a distance d2 from the fixed part, the distance d2 being greater than the distance d1.

[0028] In the closed position of the contactor 100, shown in figure 1C , the fixed part and the moving part are in contact so that an electric current flows between the two parts. In other words, the auxiliary contacts 120 and power contacts 110 are closed and the electric current flows in the two branches of the contactor 100.

[0029] When the contactor 100 closes, the voltage in the branch comprising the power contact 110 is equal to the voltage drop of the power contact 110, i.e. of the order of a hundred millivolts. Then the auxiliary contact 120 closes and the voltage in the branch comprising the pyrotechnic actuator 130 is also around a hundred millivolts. The value of the resistor 140 is chosen so that the current flowing in the pyrotechnic actuator 130 remains lower than the trigger threshold current of the pyrotechnic actuator 130. For example, the resistor 140 is 2 Ohms.

[0030] When the contactor 100 opens, the auxiliary contact 120 opens first and isolates the igniter from the pyrotechnic actuator 130. Then the power contact 110 opens, electric arcs are created on this contact 110 and the voltage gradually increases in the two branches of the contactor 100 until it reaches the voltage of the voltage source 150. Thus the voltage at the terminals of the pyrotechnic actuator 130 and the current passing through it are zero thanks to the preliminary opening of the auxiliary contact 120.

[0031] Thanks to the desynchronization of the contacts 110 and 120, the igniter of the pyrotechnic actuator 130 is never subjected to the voltage of the voltage source 150, and it is thus protected and does not risk catching fire or triggering falsely.

[0032] When the contactor 100 is closed and the current becomes too high, for example reaches 2 kA, the power contact 110 can lift and levitate the contactor 100. This creates electric arcs and an arc voltage appears. The voltage in the two parallel branches of the contactor 100 increases, as does the current flowing in the igniter of the pyrotechnic actuator 130. This has the effect of triggering the pyrotechnic actuator 130 which will open or prevent the closing of the power contact 110. The triggering of the opening of the contactor 100, in the event of levitation, is thus faster than the prior art, because it does not require any means of measuring current or voltage. The triggering of the opening presents for example a speed gain of one millisecond compared to the prior art.

[0033] In this exemplary embodiment, the pyrotechnic actuator 130 comprises an igniter 132 and a piston 131. When the current flowing through the pyrotechnic actuator 130 increases, the igniter 132 melts and triggers the pyrotechnic actuator 130 by releasing the piston 131. Being released, the piston 131 prevents the power contact 110 from closing, as illustrated in the figure 2 This prevents the power contact 110 from falling back onto the fixed part and from being welded to the fixed part following the levitation of the contactor 100. This prevents damage to the contactor 100.

[0034] The contactor 100 may also include a transient voltage suppression diode (also called a transil diode or transzorb diode), placed in parallel with the pyrotechnic actuator 130 and the resistor 140. This diode makes it possible to limit the voltage to protect the igniter 132 and the resistor 140, in particular if the voltage increases too quickly at the terminals of the power contact 110.

[0035] Furthermore, the contactor 100 has been described with a single power contact 110 and a single auxiliary contact 120, but it may comprise two or more power contacts which will always be out of sync with the auxiliary contact 120. In this case, the auxiliary contact 120 is always connected to the same pyrotechnic actuator 130 and the pyrotechnic actuator 130 actuates the different power contacts in a synchronized manner.

[0036] There figure 3 schematically represents a method 300 for closing a power contactor according to an embodiment of the invention.

[0037] The contactor is initially in the open position 310, so the fixed and moving contacts are not in contact and no electric current flows between these two parts.

[0038] In order for the contactor to move to the closed position 320, the motor is powered so as to apply a pressure force to the moving part of the contactor, and the power contact is first brought into contact with the fixed part (step 301), then the auxiliary contact is brought into contact with the fixed part (step 302).

[0039] There figure 4 schematically represents a method 400 for opening a power contactor according to one embodiment of the invention.

[0040] The contactor is initially in the closed position 410, so the fixed and moving parts are in contact and an electric current flows between these two parts.

[0041] For the contactor to move to the open position 420, the motor power supply is cut off and the auxiliary contact opens first (step 401). So it is no longer in contact with the fixed part of the contactor, then the power contact opens (step 402).

Claims

1. A power contactor (100) comprising: - a fixed part; - a movable part able to come into contact with the fixed part and to move between an open position and a closed position of the contactor, the movable part comprising at least one power contact (110); - an auxiliary contact (120) and a pyrotechnic actuator (130), the auxiliary contact being in series with the pyrotechnic actuator, the auxiliary contact and the pyrotechnic actuator being placed in parallel with the power contact, and the pyrotechnic actuator being configured to be triggered during a levitation of the contactor in such a way as to move the contactor into the open position, and - a motor configured to actuate the movable part and to put it in contact with the fixed part, characterized in that the power contact and the auxiliary contact are desynchronized in such a way that during the closure of the contactor, the power contact comes into contact with the fixed part before the auxiliary contact and during the opening of the contactor, the auxiliary contact opens before the power contact.

2. The power contact as claimed in claim 1, also comprising a transientvoltage-suppression diode in parallel with the pyrotechnic actuator.

3. The power contact as claimed in any of claims 1 or 2, wherein the pyrotechnic actuator (130) comprises an igniter (132) and a piston (131), the igniter being configured to trigger the pyrotechnic actuator by melting and release the piston to open the contactor.

4. A method (300) for closing (320) a power contactor in the open position (310) as claimed in any of claims 1 to 3, comprising the putting (301) of the power contact in contact with the fixed part then the putting (302) of the auxiliary contact in contact with the fixed part.

5. A method (400) for opening (420) a power contactor in the closed position (410) as claimed in any of claims 1 to 3, comprising the opening (401) of the contact between the auxiliary contact and the fixed part, then the opening (402) of the contact between the power contact and the fixed part.

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