Electrical actuation system for motorized valve

Abstract

An electric actuation system (11) for a motorized valve (1) comprises switching means (14) for starting, maintaining, and then cutting off a supply of electrical power to a motor (3) of the valve. The

Description

Title: ELECTRICAL ACTUATION SYSTEM FOR MOTORIZED VALVE Technical field [1] This description relates to an electrical actuation system for a motorized valve, as well as to an assembly for controlling a flow of fluid. Throughout this description, the term "valve" designates both a binary-state mechanism for allowing or blocking a fluid flow, and a continuously open valve for adjusting a flow rate. In addition, the acronym "IGBT" stands for insulated-gate bipolar transistor, which is a semiconductor component that is well known to those skilled in the art. Prior art [2] Some applications use valves that require precautions in order to employ them. This is the case, for example, with valves that are used in an electricity-generating nuclear power plant, in particular valves that are in the primary fluid circuit of the nuclear reactor. As shown in [Fig. 1], such a valve, which is generally designated by reference number 1, comprises a shutter 2 for reversibly closing a pipe 10 that contains the flow of fluid, a servomotor 3, and a mechanical coupling system 4 that transmits the actuation movement produced by the servomotor, to the shutter. The mechanical coupling system itself comprises a fixed support 5, called a yoke, which rigidly connects the stator of the servomotor to the pipe of fluid, and mobile drive elements such as a valve rod 6 and a drive coupler 7 that converts the rotation of the servomotor rotor into movement of the valve rod. [3] When such a valve is electrically actuated in order to close or open it, parts of this valve, in particular its mechanical coupling system, undergo excess force when the rotation of the servomotor stops after a delay relative to the time of the stop command. This delay has several origins, including a delay in opening a contactor used to control the supply of electricity to the valve servomotor, the rotational inertia of the servomotor rotor, as well as the self-inductance of the servomotor coils. The delay in opening the contactor is intrinsic to its electromechanical operation. It is due in particular to the inertia of the contactor's internal moving parts which establish and discontinue the electrical contact, the stiffness of springs internal to the contactor, and the self-inductance of a contactor coil. The diagram of [Fig. 2] shows the variation in the relative intensity of the excess force undergone by the valve when the power to its actuator is cut off, as a function of the contactor opening delay. The vertical axis shows the relative intensity of the excess force denoted T, expressed as a percentage, and the horizontal axis shows the values of the contactor opening delay, denoted R and expressed in seconds (s). Typically, a contactor opening delay of 60 ms (milliseconds) causes an excess force of approximately 14%. The variation in the relative intensity of the excess force as a function of the contactor opening delay is almost linear, with a small additional parabolic component. Successive actuations of the valve, each repeating the excess force, cause premature wear or even breakage of the valve, the breakage most often being in its mechanical coupling system. To reduce the excess force undergone by the valve, at least one stress sensor 8 (see [Fig. 1]) is arranged, usually on critical parts of the valve, for example on its mechanical coupling system 4 and / or on an end-of-travel stop for the shutter 2. It is then important to be able to interrupt a rotation in progress of the servomotor of the valve provided with the stress sensor, with a minimal delay from the time at which an excess force is detected. [4] Reference number 11 in [Fig. 1] designates an electrical power module that is used to power the valve 1 from an electrical voltage source 20. This power module 11 contains the contactor mentioned above and designated by reference number 13, a circuit 15 for controlling this contactor, a protection circuit 16 for protecting the servomotor 3 against overvoltage, as well as a digital card 17 for triggering a cut-off. The power module 11 may be in a power drawer format intended for insertion into an electrical cabinet. A stress amplitude measurement signal is then transmitted by each stress sensor 8 to the control circuit 15, so that the latter triggers a cut-off of the power supply to the servomotor in the event of a measured stress that is too high. [5] To date, the fastest electromechanical contactors have opening delays of around 20 ms. These values are too high for many applications using valves with excess-stress sensors, particularly for such valves when used in a nuclear power plant. It is therefore necessary to increase the frequency of inspection and maintenance of these valves in order to achieve the required level of reliability. Technical problem [6] Based on this situation, one object of the present invention is to increase the service life of a motorized valve that is electrically actuated, in particular a motorized valve having a stress sensor. [7] An additional object of the invention is to reduce the excess force that is undergone by the motorized valve when it is actuated. [8] Another object of the invention is to shorten the electrical power cut-off delay that occurs when controlling a motorized valve. [9] Yet another object of the invention is to dissipate energy contained in a running motor in order to stop rotation of the motor more quickly. Summary of the invention

[10] To achieve at least one of these objects or some other object, a first aspect of the invention provides a novel electrical actuation system for a motorized valve, which comprises switching means for starting, maintaining, and then cutting off a supply of electrical power from an electrical voltage source to a motor of the valve, and control means adapted to activate the switching means. According to the invention, the switching means comprise insulated-gate bipolar transistors, or IGBT transistors, which are arranged to connect electrically, during a use of the actuation system to actuate the valve, the electrical voltage source to power terminals of the valve motor via electrical conduction paths of the insulated-gate bipolar transistors. In addition, electrical outputs of the control means are connected to the gates of the insulated-gate bipolar transistors.

[11] Thus, the control means control the start, maintaining, and terminating of the supply of electrical power to the valve motor from the electrical voltage source, by means of the IGBT transistors instead of the electromechanical contactor used prior to the invention. Thanks to this, the time necessary for cutting off the supply of electrical power to the valve motor depends on the switching speed of the IGBT transistors, and can thus be reduced to a large extent, in particular down to values of around 0.15 ms (millisecond). The power may thus be cut off more quickly upon detecting excess force in the valve, preventing this excess force from persisting before the power is actually cut off. Wear on the valve is thus reduced by the electrical actuation system of the invention, and the service life of the valve is increased accordingly.

[12] In some possible embodiments of the invention, the system of the invention may be adapted for an electrical voltage source of AC-source type , and adapted so that, during use of the system, terminals of the electrical voltage source are connected one by one to the power terminals of the valve motor via the electrical conduction paths of two insulated-gate bipolar transistors which are connected in series but in opposite conduction directions within separate switching branches. For such embodiments, the system further comprises a respective diode for each of both insulated-gate bipolar transistors of each switching branch, this diode being connected in parallel with the corresponding insulated-gate bipolar transistor such that this insulated-gate bipolar transistor and this diode have opposite conduction directions.

[13] Preferably, the system of the invention may be arranged and sized for being inserted into an electrical power distribution cabinet, in particular in the form of a power drawer which is wired to provide the valve motor with three-phase electrical power with 380 V (volts) interphase voltage, suitable for actuating the valve.

[14] In preferred embodiments of the electrical actuation system of the invention, this system may further comprise an electrical dissipation circuit which is arranged to be connected to the power terminals of the valve motor, in parallel with coils of this motor. This electrical dissipation circuit is adapted to electrically absorb at least part of an energy amount that is released by the motor when its supply of electrical power is cut off. In other words, the electrical dissipation circuit allows stopping a rotation of the motor even more quickly, which provides a further reduction in the excess forces.

[15] According to one possible and advantageous composition of the electrical dissipation circuit, the circuit may comprise: - diode-based rectifier bridge branches, one rectifier bridge branch per power terminal of the motor; - a branch having a voltage-limiting function, preferably comprising a Zener diode; - at least one branch having a capacitive braking function, comprising a capacitor; - at least one discharge branch comprising a discharge resistor; and - at least one branch having a resistive braking function, comprising a braking resistor and a controlled switch which is connected in series with the braking resistor in order to control a resistive braking operation.

[16] In general for the invention, the system may further comprise a digital circuit which is adapted to transmit commands for starting and cutting off the supply of electrical power to the control means, and to receive feedback signals relating to an execution of each of these commands, and preferably also signals indicating electrical currents transmitted to the valve motor which are above a limit. When an electrical dissipation circuit is used, the digital circuit may further be adapted to control an operation of the electrical dissipation circuit each time the supply of electrical power to the valve motor is cut off.

[17] Also in general for the invention, the control means may further be adapted to receive stress measurement signals which are transmitted by at least one stress sensor of the valve during use of the system to actuate the valve, and to control the switching means to cut off the supply of electrical power to the valve motor when the measurement signals indicate stresses above a threshold. The occurrence of excess forces in the valve is thus avoided. In particular, the digital circuit may advantageously control operation of the electrical dissipation circuit when the measurement signals indicate that the measured stresses are greater than the threshold.

[18] Again in general for the invention, the control means, and the digital circuit where appropriate, may preferably be made up of non-programmable components and are without any programmable components. Monitoring the qualification of the system is thus simplified, since this can be limited to an initial qualification procedure. Such a precaution is particularly advantageous when the qualification requirement is strict, as it is the case in particular for an application of the invention in the context of a nuclear power plant.

[19] A second aspect of the invention proposes an assembly for controlling a flow of fluid, which comprises: - an electrical voltage source; - a system that is in accordance with the first aspect of the invention; and - a motorized valve comprising a motor, wherein the switching means of the system connect the electrical voltage source to power terminals of the valve motor.

[20] In particular, the motorized valve may comprise at least one stress sensor, and the assembly may then be configured so that, during an actuation of the valve, the system triggers cutting off of the supply of electrical power to the valve motor when the stress sensor produces measurement signals that indicate stresses above a threshold.

[21] In such assembly according to the invention, the electrical voltage source may be of the three-phase type with 380°V interphase voltage, and the system may be arranged and sized for being inserted into an electrical power distribution cabinet.

[22] Finally, an assembly according to the invention may be installed for controlling a circuit for fluid in a power generation facility, in particular of a nuclear power plant. Brief description of figures

[23] The features and advantages of the invention will become more clearly apparent from the following detailed description of some non-limiting exemplary embodiments, with reference to the appended figures in which:

[24] [Fig. 1], already described, represents the main elements of a motorized valve;

[25] [Fig. 2], already described, is a diagram of variation in intensity of an excess force undergone by a valve according to [Fig. 1], as a function of a delay in opening a contactor used to supply power to the valve;

[26] [Fig. 3] is a general diagram of an assembly for controlling a flow of fluid, according to the invention; and

[27] [Fig. 4] is an electrical diagram of a valve actuation system which can be used in the assembly of [Fig. 3], Detailed description of the invention

[28] For clarity, the dimensions of elements shown in these figures do not correspond to actual dimensions nor to actual dimension ratios. Furthermore, some of these elements are only represented symbolically, and identical references indicated in different figures designate identical elements or those having identical functions.

[29] By way of illustration but without limitation, the embodiment of the invention now described in detail uses the assembly structure of [Fig. 1], in the case of a servomotor 3 which is of the three-phase asynchronous type supplied with 380 V (volts) of interphase voltage. The invention consists of replacing the electromechanical contactor 13 with switching means 14 based on IGBTs, as described below, and in addition, optionally using a protection circuit 16 which is enhanced with an energy dissipation function. This energy dissipation function is intended to be effective each time the power to the servomotor 3 of the valve 1 is cut off, and constitutes an electrical brake for the servomotor.

[30] [Fig. 3] shows one embodiment of the invention, in the form of a new power module 11 to be used to actuate the valve 1. This new power module 11 may be of one of the types N660 or N680, for insertion into a Normabloc® electrical cabinet which is well known to those skilled in the art. It constitutes the electrical actuation system for the motorized valve as introduced in the general part of this description, and the association of this power module 11 with the electrical voltage source 20 and the motorized valve 1 constitutes the assembly for controlling a flow of fluid. Reference numbers 21,22, and 23 designate the three terminals of the electrical voltage source 20, which deliver two by two the alternating electrical voltages of 380 V peak value, 120°-offset between the phases, and reference numbers 31, 32 and 33 designate the three power terminals of the servomotor 3 of the valve 1.

[31] In the embodiment of the invention which is described in detail below, the power module 11 contains the following elements: - one or more switching card(s) 14, which carries(carry) the IGBT transistors used to connect each stator coil of the servomotor 3 to one of the outputs 21, 22, 23 of the electrical voltage source 20. Each connection which is thus made between one of the stator coils and one of the outputs 21, 22, 23 of the source 20 is called a switching branch, corresponding to the switching means mentioned in the general part of this description; - one or more control card(s) 15 for controlling the IGBT transistors of each switching card 14, and which constitute(s) the control means mentioned in the general part of this description; - a protection card 16, which also produces the electric braking function for the servomotor 3; and - a digital card 17, which contains a digital circuit for controlling the operation of the protection card 16, in order to produce the electric braking function. In a manner that is customary in this technical field, the signal inputs and outputs of each control card 15 and of the digital card 17 are provided with galvanic isolation interfaces, for example of the electro-optical type and denoted E / O. Furthermore, according to a common design method, at least one pair comprising a switching card 14 and an associated control card 15 is dedicated separately to each switching branch. Thus, the example shown in [Fig. 3] and [Fig. 4] shows a configuration with five switching branches.

[32] The switching card(s) 14 further carries(carry) a shunt resistor SH for each switching branch, which is connected in series with the IGBT transistors of this switching branch. These resistors SH make it possible to monitor the electrical currents that are transmitted to the coils of the servomotor 3, in order to confirm the switching operations of the IGBT transistors and also to detect overcurrents that could occur for these currents.

[33] In each control card 15, LOG15 designates a logic circuit, DR for “driver” designates a control component which is connected to the gate of one of the IGBT transistors of the switching cards 14, AMP1 designates an amplifier which is arranged to amplify an existing electrical voltage at one of the resistors SH, and COMP1 designates a threshold comparator which allows detecting overcurrent situations for the current transmitted by the corresponding switching branch. The logic circuits LOG15 are configured to control the control components DR according to overcurrent protection signals OCP delivered by the comparators COMP1, and according to an instruction on whether or not to supply power, denoted ON / OFF, which is delivered by the digital card 17.

[34] In the digital card 17, LOG17 designates another logic circuit which is configured to transmit the instruction ON / OFF on whether or not to supply power to each control card 15, on the basis of request signals RQ requesting actuation of the valve 1 which are received from an application driver 12, and overcurrent signals OCP. The logic circuit LOG17 also sends to the protection and electric braking card 16 at least one activation signal for the electric braking function.

[35] Preferably, each control card 15 and the digital card 17 are made up solely of non-programmable components such as operational amplifiers, comparators, and analog logic gates, without any use of programmable components or digital devices of limited functionality known by the acronym DDLF and as defined in the IEC 62671 standard of the International Electronic Commission (ISBN 978-2-83220-630-0).

[36] For the application of the invention to a motorized valve having a stress sensor which is described herein, each control card 15 has at least one additional control channel which has its input connected to the output of the stress sensor(s) 8 of the valve 1. This additional control channel comprises an amplifier AMP2 which is configured to amplify the stress measurement signals produced by the stress sensor 8, and a threshold comparator COMP2 which has its input connected to the output of the amplifier AMP2. The output of the threshold comparator COMP2 is connected to the logic circuits LOG15 and LOG17, to produce a signal indicating excess stress, denoted OSP for “over-stress protection”. This OSP signal is then used to trigger a sequence for stopping the rotation of the servomotor 3 when the sensor 8 reveals the existence of stress, at a location on the valve 1, which is greater than the threshold. As explained below, this stopping sequence comprises a discontinuation of the supply of power to the servomotor 3, which is produced by the switching cards 14, and the electrical braking which is produced by card 16. In this manner, the rotation of the servomotor 3 is stopped in a very short time, which reduces or avoids the occurrence of excessive overstresses in the valve 1.

[37] [Fig. 4] is a diagram of some possible electrical circuits for the switching card(s) 14 as well as for the protection and electrical braking card 16. The switching card(s) 14 carries(carry) three switching branches, denoted BC1, BC2 and BC3, for the rotation of the servomotor 3 in one direction, and two additional branches BC4 and BC5 for the reverse direction of rotation of the servomotor 3. Switching branch BC1 connects terminal 21 of the electrical voltage source 20 to terminal 31 of the coil L1 of the stator of the servomotor 3. Similarly, switching branch BC2 (respectively BC3) connects terminal 22 (respectively 23) of the electrical voltage source 20 to terminal 32 (respectively 33) of the coil L2 (respectively L3) of the stator of the servomotor 3. In a manner that is known for an asynchronous motor, its stator coils L1, L2, and L3 are connected in a star-like configuration by their other respective terminals. To enable the direction of rotation of the servomotor 3 to be reversed, switching branch BC4 (respectively BC5) connects terminal 22 (respectively 21) of the electrical voltage source 20 to terminal 31 of coil L1 (respectively 32 of coil L2) of the stator of the servomotor 3. All the switching branches BC1 to BC5 may be identical, and carried by different switching cards 14. Each switching branch BC1,, BC5 comprises two IGBT transistors which are designated IGBT1 and IGBT2, and which are connected in series and in opposite directions within each switching branch: the emitter of the IGBT1 transistor is connected to the emitter of the IGBT2 transistor through an intermediate terminal of the switching branch called the midpoint terminal and designated M. The collector of the IGBT1 transistor is connected to the corresponding terminal 21, 22, 23 of the electrical voltage source 20, and the collector of the IGBT2 transistor is connected to the corresponding power terminal 31, 32, 33 of the servomotor 3. Each switching branch BC 1,..., BC5 further comprises the corresponding shunt resistor SH, its function being to enable the control cards 15 to control the switching operation of this switching branch, and also to detect whether excess current is flowing in this switching branch, as already described above. A diode D1 is connected between the emitter and the collector of each IGBT1 transistor, in the direction from the emitter of the IGBT1 transistor to the collector of the same IGBT1 transistor. Similarly, a diode D2 is connected between the emitter and the collector of each IGBT2 transistor, similarly in the direction from the emitter of the IGBT2 transistor to the collector of the same IGBT2 transistor. The control card 15 which is assigned to one of the switching branches BC1,..., BC5 transmits two control signals to this branch: a first control voltage between the gate of the IGBT1 transistor and the midpoint terminal M of this switching branch, and a second control voltage between the gate of the IGBT2 transistor and the midpoint terminal M of the same switching branch. The first control voltage makes it possible to make the switching branch conducting for the positive alternations of the supply voltage delivered by the corresponding terminal of the electrical voltage source 20 with respect to the common point of the coils L1-L3, and the second control voltage makes it possible to make this same switching branch conducting for the negative alternations of the same supply voltage. Zero values for the two control voltages of the transistors IGBT1 and IGBT2 of a same switching branch suppress the ability to supply power to the servomotor 3 through this switching branch. There are commercially available models of control cards 14 designed to produce this operation with supplying and non-supplying of power.

[38] The circuit of the protection and electrical braking card 16, which has been called the electrical dissipation circuit in the general part of this description, comprises the association of the following branches in parallel between the two nodes A and B: - a separate rectifier bridge branch RD for each of the power terminals 31, 32, and 33 of the servomotor 3. Each branch RD comprises two diodes D3 and D4 that are connected in series and in the same direction, oriented from node B to node A, with an intermediate terminal between both diodes that is connected to the corresponding power terminals 31, 32, 33 of the servomotor 3; - a branch LT with voltage-limiting function, which comprises a Zener diode Z with its cathode connected to node A and its anode connected to node B; - at least one branch with capacitive braking function, comprising a capacitor C_Fr and optionally a load resistor R_Ch connected in series with the capacitor C_Fr, in such case with a controlled switch that is connected in parallel with the load resistor R_Ch; - at least one discharge branch comprising a discharge resistor R_L; and - at least one branch with resistive braking function, comprising a braking resistor R_Fr and another controlled switch that is connected in series with the resistor R_Fr. Both controlled switches may be additional IGBT transistors, respectively denoted IGBT3 for the one in the branch with resistive braking function and IGBT4 for the one in the capacitive braking branch. When the servomotor 3 rotates while being supplied with 380 V of peak interphase voltage, the voltage between nodes A and B is approximately 600 V-DC, being filtered by the combination of the capacitor C_Fr with the resistor R_L which have high values. The controlled switch IGBT3 is then controlled by the digital card 17 to be in its blocked state. The Zener diode Z is selected with a threshold voltage of approximately 650 V, in order to protect against overvoltages above this threshold. During a period of continuous rotation of the servomotor 3 and during the entire following sequence of stopping this rotation, the logic circuit 17 maintains the controlled switch IGBT4 as conducting, so that the load resistor R_Ch does not participate. When the switching branches BC are all cut off simultaneously by the control cards 15, an electromotive force produced by the servomotor 3 at cutoff is possibly clipped by the Zener diode Z, and the corresponding electrical current is absorbed by the capacitor C_Fr then conducted by the braking resistor R_Fr. To do this, the digital card 17 switches the controlled switch IGBT3 to its on-state with a small time delay with respect to the switching of transistors IGBT1 and IGBT2 to cut off power to the servomotor 3. Next, the capacitor C_Fr discharges completely through the resistors R_L and R_Fr. The person skilled in the art will know, from the above description of the operation of the electric 5 braking, how to select the values of the capacitor C_Fr and of the resistors R_L and R_Fr, as well as that of the switching delay of the controlled switch IGBT3, to produce effective electrical braking. This electrical braking is implemented each time the supply of electrical power to the servomotor 3 is cut off, whether this cutoff is caused by the detection of excess force by the or one of the stress sensors 8, or caused by an overcurrent detected via one of 10 the shunt resistors SH, or is produced in response to a request RQ which originates from the application driver 12. The logic circuit LOG17 may then send, back to the application driver 12, a signal RT which confirms that the supply of power has been cut off.

Claims

1. An electrical actuation system (11) for a motorized valve (1), comprising switching means (14) for starting, maintaining, and then cutting off a supply of electrical power from an electrical voltage source (20) to a motor (3) of the valve, and control means (15) adapted to activate the switching means,wherein the switching means (14) comprise insulated-gate bipolar transistors (IGBT1, IGBT2) which are arranged to connect electrically, during a use of the actuation system (11) to actuate the valve (1), the electrical voltage source (20) to power terminals (31, 32, 33) of the valve motor (3) via electrical conduction paths of the insulated-gate bipolar transistors, and wherein electrical outputs of the control means (15) are connected to the gates of the insulated-gate bipolar transistors,characterized in that the control means (15) are further adapted to receive stress measurement signals which are transmitted by at least one stress sensor (8) of the valve (1) during use of the system to actuate said valve, and to control the switching means (14) to cut off the supply of electrical power to the valve motor (3) when the measurement signals indicate stresses above a threshold.

2. The system (11) of claim 1, adapted for an electrical voltage source (20) of the AC-source type, and adapted so that, during use of the system, terminals (21, 22, 23) of the electrical voltage source are connected one by one to the power terminals (31, 32, 33) of the motor (3) of the valve (1) via the electrical conduction paths of two insulated-gate bipolar transistors (IGBT1, IGBT2) which are connected in series but in opposite conduction directions within separate switching branches (BC1,..., BC5), the system further comprising a respective diode (D1, D2) for each of the two insulated-gate bipolar transistors of each switching branch, the diode being connected in parallel with the corresponding insulated-gate bipolar transistor such that said insulated-gate bipolar transistor and said diode have opposite conduction directions.

3. The system (11) of claim 1 or 2, further comprising an electrical dissipation circuit (16) which is arranged to be connected to the power terminals (31, 32, 33) of the motor (3) of the valve (1), in parallel with coils (L1, L2, L3) of said motor, said electricaldissipation circuit being adapted to electrically absorb at least part of an energy amount that is released by the motor when the supply of power to said motor is cut off.

4. The system (11) of claim 3, wherein the electrical dissipation circuit (16) comprises the following circuit branches, which are connected in parallel:- diode-based rectifier bridge branches (RD), one rectifier bridge branch per power terminal (31, 32, 33) of the motor;- a branch having a voltage-limiting function (LT), preferably comprising a Zener diode (Z);- at least one branch having a capacitive braking function, comprising a capacitor (C_Fr);- at least one discharge branch comprising a discharge resistor (R_L); and- at least one branch having a resistive braking function, comprising a braking resistor (R_Fr) and a controlled switch (IGBT3) which is connected in series with the braking resistor in order to control a resistive braking operation.

5. The system (11) of one of the preceding claims, further comprising a digital circuit (17) adapted to transmit commands for starting and cutting off the supply of electrical power to the control means (15), and to receive feedback signals relating to an execution of each of said commands, and preferably also signals indicating electrical currents transmitted to the motor of the valve (1) which are above a limit.

6. The system (11) of claim 5 and claim 3 or 4, wherein the digital circuit (17) is further adapted to control an operation of the electrical dissipation circuit (16) each time the supply of electrical power to the motor (3) of the valve (1) is cut off.

7. The system (11) of one of the preceding claims, arranged and sized for being inserted into an electrical power distribution cabinet.

8. The system (11) of one of the preceding claims, wherein the control means (15), and the digital circuit (17) where appropriate, are made up of non-programmable components and are without any programmable components.

9. An assembly for controlling a flow of a fluid, comprising:- an electrical voltage source (20);- a system (11) that is in accordance with one of the preceding claims; and- a motorized valve (1) comprising a motor (3) and at least one strain sensor (8), wherein the switching means (14) of the system (11) connect the electrical voltage source 5 (20) to power terminals (31, 32, 33) of the motor (3) of the valve (1),and the assembly is configured so that, during an actuation of the valve (1), the system (11) triggers cutting off of the supply of electrical power to the motor (3) of said valve when the stress sensor produces measurement signals that indicate stresses above a threshold.

10. The assembly of claim 9, wherein the electrical voltage source (20) is of the 10 three-phase type with 380 V interphase voltage, and the system is in accordance with claim 8.

11. The assembly of claim 9 or 10, installed for controlling a circuit for fluid in a power generation facility, in particular of a nuclear power plant.A

Images