Hybrid switch and control device

Abstract

The present invention relates to a hybrid switch and control device for extinguishing an electric arc and interrupting the electric current in an electrical circuit, said device comprising, on the one hand, a hybrid switch (1, 2) comprising an electromechanical switch (1) and, in parallel, an electronic switch (2) for assisting in extinguishing the electric arc and interrupting the electric current resulting from said arc, said electromechanical switch (1) comprising at least one electrical contact (1a) to the terminals of which said electronic switch (2) is connected and, on the other hand, an electronic control circuit (3) capable of controlling said electronic switch (2) when said electric arc occurs and until the interruption of the electric current.The electronic control circuit (3) consists of a semiconductor-based analog electronic control circuit (Q2) and is configured to detect the occurrence of an electric arc across the terminals of the electrical contact (1a) and to deliver to an output (S) of said electronic control circuit (3) an output signal capable of controlling said electronic switch (2) according to a multi-phase time sequence of arc extinction and current interruption. Figure to be published with the abbreviation: Fig. 3.

Description

Title of the invention: Hybrid switch and control device

[0001] The present invention relates to the field of switches and safety protection circuits connected in an electrical circuit and capable of generating electric arcs, and more particularly, to hybrid switches and their control device enabling the extinguishing of such an electric arc and the interruption of the electric current in said electrical circuit. Its object is a hybrid switch and control device.

[0002] Hybrid switches are known to comprise an electromechanical switch and an electronic switch. The electromechanical switch, based on electromechanical commutation, includes at least one electrical contact and provides a low voltage drop across its terminals in the closed state and good galvanic isolation in the open state, but has the disadvantage of generating electric arcs when the electrical contact opens under load. The electronic switch, on the other hand, is free of electric arcs but has a much higher voltage drop in the conducting state and does not provide galvanic isolation in the open state.

[0003] Hybrid switches are essentially designed to take advantage of the respective strengths of both types of switches by compromising on their respective weaknesses.

[0004] The combination of these two switches, namely the electromechanical switch and the electronic switch, forming the hybrid switch, can be arranged in series or in parallel, or in series and / or parallel combinations. The series combination, which can be implemented with or without arcing during opening under load depending on the synchronization of the opening commands, ensures galvanic isolation in the open state but has a high voltage drop in the on state. The parallel combination, which can be implemented with or without arcing during opening under load depending on the synchronization of the opening commands, has a low voltage drop in the on state but does not ensure galvanic isolation in the open state.

[0005] The electronic switch is controlled by an electronic control device and consists of an analog electronic circuit comprising a varistor in parallel with a power semiconductor such as a power transistor, generally a field-effect transistor or an insulated-gate transistor. The varistor and the semiconductor are connected in parallel directly to the terminals of the electromechanical switch contact.

[0006] The electronic switch generally comprises two parallel branches, at The circuit consists of a first branch comprising the varistor and a second branch comprising the semiconductor. The branch of the hybrid switch's electrical circuit comprising the electrical contact is parallel to these first and second branches of the electronic switch.

[0007] In operation, among the known sequences, one can distinguish the temporal sequence of extinction of the electric arc and interruption of the electric current in several phases, and more particularly according to the following three successive phases:

[0008] - in a first phase, when the contact of the electromechanical switch opens, for example following the detection of an electrical fault, an electric arc appears;

[0009] - in a second phase the semiconductor of the electronic switch is commanded to be switched to the saturated ON state, the electric current then switches completely into the second branch of the electronic switch, resulting in the extinction of the electric arc.

[0010] - then, in a third phase, the semiconductor is commanded to be When switched to the OFF state, the abrupt interruption of current in the semiconductor generates a voltage surge that activates the varistor, causing the electrical current to completely flow into the first branch of the electronic switch. The voltage established across the varistor is sufficient to limit the electrical current and bring it to a complete halt.

[0011] However, regardless of the sequence used, the control of the electronic switch, particularly the power semiconductor, uses complex, digital electronics based on a microprocessor or microcontroller, requiring a stable external power supply. US patent 2019 / 0252143 discloses such control / driving electronics, including an electronic control unit based on a microcontroller or microprocessor.

[0012] It is also known, in an alternating current application, or in an application with a bidirectional DC supply, for example in a battery charging or producing an electric current, to incorporate a diode bridge between the varistor and the semiconductor in order to interrupt the current in both directions.

[0013] The present invention aims to overcome these drawbacks by proposing a hybrid switch and control device implementing less complex control electronics that do not require an external power supply.

[0014] To this end, the hybrid switch and control device, according to the present invention, allows the extinguishing of an electric arc and the interruption of the electric current in an electrical circuit, said device comprising, on the one hand, a hybrid switch comprising an electromechanical switch and, in parallel, an in electronic arc extinguishing assistance switch and interruption of the resulting electric current, said electromechanical switch comprising at least one electrical contact capable of being actuated in the closing position to allow the passage of electric current in the electrical circuit and in the opening position to interrupt said passage, said electronic switch being configured to be able to extinguish an electric arc occurring upon the opening of said electrical contact and then interrupt the electric current and consisting of an analog electronic circuit based on a power semiconductor connected to the terminals of the electrical contact and, on the other hand, an electronic control circuit capable of controlling said electronic switch when said electric arc occurs and until the interruption of the electric current,is essentially characterized in that the electronic control circuit consists of a semiconductor-based analog electronic control circuit and in that said electronic control circuit is configured to detect the appearance of an electric arc occurring at the terminals of the electrical contact and to deliver, at an output of said electronic control circuit, an output signal capable of controlling said electronic switch according to a time sequence of extinguishing the electric arc and interrupting the electric current in several phases.

[0015] In a first embodiment of the electronic control circuit, the latter is configured to detect the appearance of the electric arc by its characteristic arc voltage by being able to deliver, as a function of the voltage across the terminals of the electrical contact, at the output of said electronic control circuit, an output signal capable of controlling said electronic switch according to the time sequence of extinction of the electric arc and interruption of the electric current in several phases.

[0016] In a second embodiment of the electronic control circuit, the latter can be configured to detect the appearance of the electric arc by its characteristic emitted light by being able to deliver, as a function of said emitted light, at the output of said electronic control circuit, the output signal able to control said electronic switch according to the time sequence of extinction of the electric arc and interruption of the electric current in several phases.

[0017] The invention will be better understood from the following description, which relates to at least one preferred embodiment, given by way of non-limiting example, and explained with reference to the accompanying schematic drawings, in which:

[0018] [Fig. 1] shows the diagram of the hybrid switch and control device, according to the present invention, connected in an electrical circuit, with the electronic switch and the electronic control circuit in block diagram form,

[0019] [Fig. 2] shows the electrical diagram of the hybrid switch and control device command, according to the present invention, shown in [Fig. 1] in a mode of rea- preferential use of the electronic switch,

[0020] [Fig.3] shows the electrical diagram of the device, according to the present invention, re presented in [Fig.2], in the first embodiment of the electronic control circuit, with a control transistor of the bipolar transistor type,

[0021] [Fig.4] shows the electronic control circuit shown in [Fig.3] and eliminating the need for capacitors,

[0022] [Fig.5] shows the electronic control circuit shown in [Fig.3] in a variant with a field-effect transistor control transistor,

[0023] [Fig.6] shows the electronic control circuit shown in [Fig.5] in a variant without capacitors,

[0024] [Fig.7] shows the device, according to the present invention, represented in Figures 3, 4, 5 and 6, without the electronic control circuit 3 and in an embodiment where the electronic switch is configured to operate in a bidirectional configuration, with a diode bridge,

[0025] [Fig.8] shows the device, according to the present invention, represented in [Fig.2], in which the electromechanical switch is of the disconnector circuit breaker type and further includes a second electrical contact equipped with a displacement and arc-fractionating breaking chamber and mounted in series with the first electrical contact to the terminals of which the electronic switch is connected.

[0026] The figures show a hybrid switch and control device, according to the present invention, allowing the extinction of an electric arc and the interruption of the electric current in an electrical circuit C.

[0027] Such a device, according to the present invention, comprises:

[0028] - on the one hand, a hybrid switch 1, 2 suitable for being connected to said electrical circuit C and comprising an electromechanical switch 1 and, in parallel, an electronic switch 2 for assisting in arc extinguishing and interrupting the electric current, said electromechanical switch 1 comprising at least one electrical contact la capable of being actuated in the closing position to allow the passage of electric current in the electrical circuit C and in the opening position to interrupt said passage. The electronic switch 2 is configured to be able to extinguish an electric arc occurring during the opening of said electrical contact la and then interrupt the electric current and consisting of a power semiconductor-based analog electronic circuit Q1 connected to the terminals of the electrical contact la and

[0029] - on the other hand, an electronic control circuit 3 capable of controlling said in electronic switch 2 when said electric arc occurs and until the electric current is interrupted.

[0030] According to the present invention, the electronic control circuit 3 consists of a semiconductor-based analog electronic circuit Q2. Furthermore, said electronic control circuit 3 is configured to detect the occurrence of an electric arc occurring at the terminals of the electrical contact la and to deliver, to an output S of said electronic control circuit 3, an output signal capable of controlling said electronic switch 2 according to a time sequence of extinction of the electric arc and interruption of the electric current in several phases.

[0031] If we refer more particularly to figures 3, 4, 5, 6, 7 and 8, we can see that, in a first embodiment of the device according to the present invention, the electronic control circuit 3 is configured to detect the appearance of the electric arc by its characteristic arc voltage by being able to deliver, as a function of the voltage across the terminals of the electrical contact, to the output S of said electronic control circuit 3, the output signal able to control said electronic switch 2 according to said time sequence of extinction of the electric arc and interruption of the electric current in several phases.

[0032] Referring to Figures 2, 3, 4, 5, 6, 7 and 8, it can be seen that, in a preferred embodiment of the electronic switch 2, it can comprise a parallel association of two branches connected to the terminals of the electrical contact la, namely a first branch comprising a varistor RV and a second branch comprising a power transistor Q1, called arc-quenching assistance transistor Q1, such as an insulated-gate bipolar transistor, a field-effect transistor (Figures 2, 3, 4, 5, 6, 7 and 8) or a bipolar transistor.It can also be seen that the output S of the electronic control circuit 3 is connected to the gate or base of the arc-extinguishing transistor Q1 so that the output signal can be applied to the gate or base of the arc-extinguishing transistor Q1 to control the electronic switch 2 by switching the arc-extinguishing transistor Q1, in its saturated ON or blocked OFF state, through several switching phases. These switching phases allow for the execution of the arc-extinguishing and current-interrupting phases of the time sequence.

[0033] In a manner well known of the operation of transistors, it is recalled that the blocked state OFF corresponds to a state where the transistor is not conducting and the saturated state ON corresponds to a state where the transistor is conducting.

[0034] In operation, the multi-phase arc extinction time sequence may comprise three phases, phase 1, phase 2 and phase 3, starting from an initial phase in which the electrical contact la is closed so that the electric current flows in the electrical circuit C, the electronic switch 2 and the electronic control circuit 3 being then inactive while the arc extinction assistance transistor Q1 is controlled to the blocked OFF state:

[0035] - phase 1: the electrical contact is opened and an electric arc appears at the level of said open electrical contact,

[0036] - phase 2: the output signal of the electronic control circuit 3 applied to the The gate or base of the arc-extinguishing assist transistor Q1 has the effect of switching the arc-extinguishing assist transistor Q1 from the OFF blocked state to the ON saturated state, the electric current then switching in the second branch of the electronic switch 2 comprising said arc-extinguishing assist transistor Q1 and resulting in the extinction of the electric arc, then

[0037] - phase 3: the output signal of the electronic control circuit 3 applied to the The gate or base of the arc-quenching transistor Q1 switches the arc-quenching transistor Q1 from its saturated ON state to its blocked OFF state. This interrupts the current in Q1, generating a voltage surge that activates the varistor RV of the first branch, causing the current to switch to that first branch. The voltage across the varistor RV is sufficient to limit the current and achieve current extinction.

[0038] At the end of phase 3, the electrical contact is open and the electric current is zero.

[0039] The hybrid switch and control device, according to the present invention, is therefore adapted, following the appearance of the electric arc due to the opening of the electrical contact, to detect said appearance of electric arc and to carry out a sequence of extinguishing the electric arc and interrupting the electric current by acting on the control voltage of the transistor Q1 assisting the extinguishing of the electric arc, that is to say by piloting / controlling the latter, to switch it from the blocked state OFF to the saturated state ON and vice versa according to several switching phases, for example according to the two switching phases mentioned above.

[0040] Referring now to Figures 3, 4, 5 and 6, it can be seen that the electronic control circuit 3 can comprise, in the first embodiment, a switching transistor Q2, called the control transistor Q2, such as a bipolar transistor (Figures 3 and 4) or, in a variant, a field-effect transistor ([Fig. 5] and 6) and a parallel connection of two branches, namely a first branch comprising a first resistor RI in series with a first capacitor Cl and a second branch comprising a second resistor R2 in series with a second capacitor C2. The control transistor Q2 can be connected, by its collector (Figures 3 and 4) or drain ([Fig. 5] and 6), to the first branch at a first junction point forming the output of the electronic control circuit 3 and being located between the first resistor RI and the first capacitor CL. Furthermore, the control transistor Q2 can be connected, by its base ([Fig.3]) or grid ([Fig.5]), at the second. branch at a second junction point located between the second resistor R2 and the second capacitor C2.

[0041] The phase-by-phase operation of the device, according to the present invention, in this first embodiment of the electronic control circuit 3 can be as follows, starting from an initial phase where the electrical contact la is closed and the electric current flows in the electrical circuit C, the electronic switch 2 and the electronic control circuit 3 being inactive and the first and second capacitors Cl and C2 being discharged:

[0042] - phase 1: the electrical contact is opened and an electric arc The voltage across the electrical contact, which is detected by the device according to the present invention, is equal to the arc voltage and simultaneously charges the first and second capacitors C1 and C2 via the first and second resistors R1 and R2. When the voltage across the first capacitor C1, which forms the output signal of the electronic control circuit 3, exceeds a certain threshold VG(TH), an intrinsic characteristic of the arc-extinguishing transistor Q1, the latter is switched to the saturated ON state. This causes the electric current to flow from the electrical circuit C to the second branch of the electronic switch 2, which includes the arc-extinguishing transistor Q1, and consequently extinguishes the electric arc.

[0043] - phase 2: the voltage across the electrical contact is equal to the drain voltage / source VDS (figures 3 and 5) or collector / base, intrinsic characteristic voltage of the arc-quenching assistance transistor Q1 and this voltage continues to charge the second capacitor C2. When the voltage across capacitor C2 exceeds a certain threshold, for example about 0.7 V in the case of a silicon transistor, a non-negligible electric current begins to flow in the base ([Fig.3]) or a switching voltage is applied to the gate ([Fig.5]) of the control transistor Q2 which is then switched to the saturated ON state, which has the effect of discharging the first capacitor Cl through said control transistor Q2 and, as soon as the voltage across the first capacitor Cl falls below the VG(TH) threshold, switching the arc-quenching assistance transistor Q1 to the blocked OFF state.The sudden interruption of the electric current in the latter generates a sufficient overvoltage to activate the varistor Rv and the electric current then switches completely into the first branch containing said varistor Rv.

[0044] - phase 3: the electric current passes through the first branch of the switch Electronic circuit 2, including the varistor RV, and the voltage across the electrical contact, is equal to the limiting voltage of the varistor Rv. The arc-quenching assist transistor Q1 is kept in the OFF state because an electric current continues to flow in the base ([Fig. 3]) or a com voltage mutation is always applied to the gate ([Fig.5]) of the control transistor Q2 via the second resistor R2.

[0045] Thus, at the end of the aforementioned sequence, the electric arc is completely extinguished and the electric current completely interrupted despite the appearance of said electric arc.

[0046] Preferably the working voltage of the varistor RV can be chosen so as to cause a rapid drop in the intensity of the electric current until extinction.

[0047] Preferably, more particularly in the case where the arc-quenching assistance transistor Q1 is a field-effect transistor (Figures 2, 3, 4, 5, 6, 7 and 8) or an insulated-gate bipolar transistor, the choice of said transistor may be such that:

[0048] - VG(TH) (grid voltage) < 50V, preferably less than 10V, at the different values ​​of electric current intensity, this to ensure that the arc voltage is sufficient to activate the gate of the arc-extinguishing assist transistor Q1,

[0049] - VDS (drain / source voltage) < 50 V, preferably less than 10 V, at the dif different values ​​of electric current intensity, because when the arc extinction assist transistor Q1 is switched to the saturated ON state, its impedance must be lower than that of the electric arc to divert all of the electric current.

[0050] The values ​​of the first resistor RI and the first capacitor Cl are chosen to adjust the charging time constant tl of the first capacitor Cl and therefore the time before the arc-quenching assist transistor Q1 switches, i.e., the time it takes to transition from the OFF blocked state to the ON saturated state. Such a time constant tl can be chosen, for example, preferably to be less than 100 ms, more preferably between 0 and 5 ms.

[0051] Similarly, the choice of values ​​for the second resistor R2 and the second capacitor C2 is determined to adjust the time constant t2 of the charging of the second capacitor C2 and therefore the time before the switching of the control transistor Q2, that is, the time to switch it from the blocked OFF state to the saturated ON state. Such a time constant t2 is preferably chosen to be less than 100 ms, more preferably between 0 and 5 ms.

[0052] The value of the first resistor RI also affects the current limiting in the control transistor Q2, particularly in phase 3. It should be noted that the arc voltage intrinsically decreases as the current increases. Thus, as the current increases, the time (duration) for the first capacitor Cl to charge to the threshold value VG (TH) of the gate of the arc-quenching transistor Q1 increases. Therefore, the switching of the arc-quenching transistor Q1 to the saturated state is delayed as the current increases.

[0053] It should be noted that the duration of the passage of the electric current in the control transistor Q2 decreases slightly when the intensity of the electric current increases.

[0054] It should also be noted that an interesting property of the electronic control circuit 3 is its self-inhibition beyond a certain current threshold. The duration of phase 1 increases as the electric current increases, and the duration of phase 2 decreases. Indeed, it has been observed that beyond a certain current, the voltage across the second capacitor C2 exceeds the threshold voltage of the control transistor Q2 (for example, a threshold voltage of approximately 0.7V) before the voltage across the first capacitor C1 reaches the threshold voltage VG(TH) of the arc-quenching transistor Q1, so that the latter is not switched to the saturated state and the function is thus inhibited.

[0055] The time required to reach or exceed the threshold voltage value depends essentially on the values ​​of the first and second resistors RI, R2 and the first and second capacitors Cl and C2. It is also the result of a compromise between the energy dissipated by the electric arc and that dissipated by the transistor Q1.

[0056] Referring now to Figures 4 and 6, it can be seen that, compared to the first embodiment of the electronic control circuit 3 comprising resistors RI, R2 and capacitors Cl, C2, in a second embodiment of the electronic control circuit 3, the first branch is configured to omit the first capacitor (Cl) and / or the second branch is configured to omit the second capacitor (C2). Thus, the first branch comprises only the first resistor RI and / or the second branch comprises only the second resistor R2, and it is possible, according to the present invention, to omit only the second capacitor C2 of the second branch and / or only the first capacitor Cl of the first branch.

[0057] It will be understood that, in this second embodiment of the electronic control circuit 3, the values ​​of the time constants t1 and t2 will then depend on the values ​​of the resistances RI, R2 and / or the parasitic capacitance of the arc-extinguishing assistance transistor Q1 (case without the first capacitor Cl) and / or the parasitic capacitance of the control transistor Q2 (case without the second capacitor C2).

[0058] In this second embodiment of the electronic control circuit 3 without capacitors Cl and / or C2, the extinction of the electric arc will then be almost immediate.

[0059] Depending on the type of arc-quenching assistance transistor Ql used, i.e., a field-effect transistor (Figures 2, 3, 4, 5, 6, 7 and 8) or an insulated-gate bipolar transistor, the electronic control circuit 3 may exhibit the same electrical diagram, only the values ​​of the components (RI, R2, Cl, C2) will then be adapted.

[0060] The present invention can also provide, for an alternating electric current, that the electronic control circuit 3 is connected to an electronic switch 2 configured to operate in a bidirectional configuration. Figure 7 shows an example of such a configuration in which the electronic switch 2 includes for this purpose a diode bridge D. The diode bridge D is more particularly connected to the terminals of the varistor Rv.

[0061] The present invention may further provide that the electronic control circuit 3 can be connected to a hybrid switch 1, 2 requiring galvanic isolation and comprising for this purpose an additional electrical contact 1b upstream or downstream of the electrical contact 1a. In this case, the synchronization of the two electrical contacts 1a and 1b does not affect the operation of the device according to the present invention.

[0062] The self-inhibition function described above can be used in an application ([Fig. 8]) where the management of electric currents above a certain threshold is handled by another device, for example, in the case of a disconnector-type circuit breaker comprising two electrical contacts 1a and 1b, and where one of the two electrical contacts 1b is equipped with a displacement-operating arc interruption chamber known from the prior art. The interruption chamber manages the extinction of the electric arc for currents whose intensity exceeds a certain threshold Is, and the device according to the present invention, in which the hybrid switch 2, 3 is connected in parallel with the other electrical contact 1a, can then manage the extinction of the electric arc occurring at said electrical contact 1a and the interruption of the electric current below said threshold Is.

[0063] The control transistor Q2, such as a bipolar or field-effect transistor, can be a PNP or NPN bipolar transistor, a MOSFET (N-type or P-type), or a JFET. It will be understood that, depending on the type of transistor used, the electronic control circuit 3 can have the same electrical diagram; only the values ​​of the components (RI, R2, Cl, C2) will need to be adjusted.

[0064] The present invention may also provide, in another embodiment of the first embodiment of the electronic control circuit 3, not shown in the accompanying figures, that the first capacitor Cl and / or the second capacitor C2 is replaced by an inductance, that is to say an electronic component such as for example a coil or an inductor.

[0065] In a second embodiment of the electronic control circuit 3, it can be configured to detect the appearance of the electric arc by its characteristic emitted light and be capable of delivering, depending on said emitted light, to the output S The output signal of said electronic control circuit 3 is capable of controlling said electronic switch 2 according to the time sequence of arc extinction and interruption of the electric current in several phases. In a preferred embodiment, the electronic control circuit 3 may include a photosensitive component such as an LDR, phototransistor, or photodiode to detect the electric arc and to perform the time sequence of arc extinction and interruption of the electric current in several phases.

[0066] Thus, such a sequence of electric arc extinction and current interruption, or any other sequence of this type using the device according to the present invention, more particularly in its first and second embodiments described above, makes it possible to detect the appearance of an electric arc, and more particularly the voltage of the electric arc or the light emitted by the latter, at the terminals of the electrical contact 1a, and to directly control (or drive) the arc extinction assist transistor Q1 of the electronic switch 2, or any other power semiconductor of such an electronic switch 2 performing this arc extinction assist function, only from an analog electronic circuit based on a semiconductor (the electronic control circuit 3), that is to say, without using complex electronics, in particular based on a microprocessor or microcontroller,as is the case with known systems of the prior art.

[0067] Of course, the invention is not limited to the embodiment described and shown in the accompanying drawings. Modifications remain possible, particularly with regard to the composition of the various elements or by substitution of technical equivalents, without departing from the scope of protection of the invention.

Claims

Claims

1. Hybrid switch and control device for extinguishing an electric arc and interrupting the electric current in an electric circuit (C), said device comprising, on the one hand, a hybrid switch (1, 2) comprising an electromechanical switch (1) and, in parallel, an electronic switch (2) for assisting in extinguishing the electric arc and interrupting the electric current resulting from said arc, said electromechanical switch (1) comprising at least one electrical contact (1a) capable of being actuated in closing to allow the passage of the electric current in the electric circuit (C) and in opening to interrupt said passage,said electronic switch (2) being configured to be able to extinguish an electric arc occurring when said electrical contact (la) is opened and then interrupt the electric current and consisting of an analog electronic circuit based on a power semiconductor (Ql) connected to the terminals of the electrical contact (la) and, on the other hand, an electronic control circuit (3) capable of controlling said electronic switch (2) when said electric arc occurs and until the electric current is interrupted, said electronic control circuit (3) consisting of an analog electronic control circuit (3) based on a semiconductor (Q2) and being configured to detect the occurrence of an electric arc occurring at the terminals of the electrical contact (la) and to deliver, to an output (S) of said electronic control circuit (3),an output signal capable of controlling said electronic switch (2) according to a time sequence of extinction of the electric arc and interruption of the electric current in several phases, characterized in that said electronic control circuit (3) is configured to detect the appearance of the electric arc by its characteristic emitted light by being capable of delivering, as a function of said emitted light, to the output (S) of said electronic control circuit (3), the output signal capable of controlling said electronic switch (2) according to the time sequence of extinction of the electric arc and interruption of the electric current in several phases.,

2. Device according to claim 1, characterized in that the electronic control circuit (3) comprises a photosensitive component of the LDR, phototransistor or photodiode type in order to detect the electric arc and to carry out the time sequence for extinguishing the arc. electrical and interruption of the electric current in several phases.

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