FR2940500A1 - ELECTROMAGNETIC ACTUATOR WITH DOUBLE CONTROL CIRCUITS - Google Patents

Abstract

Electromagnetic actuator comprising a first magnetic circuit (1) having a first movable armature (10) moving relative to a first magnetic yoke (11) and being separated from said first cylinder head by at least one axial gap (e1, e2). A permanent magnet (16) with radial magnetization generates a polarization flux (φU) opposing the magnetic fluxes (φ12A, Φ12B) generated by a first winding (12A) and a second winding (12B). The actuator comprises a second magnetic circuit (2) magnetically decoupled from said first magnetic circuit and having a second movable armature (20) moving relative to a second magnetic yoke (21) and being separated from the second magnetic yoke (21) by a sliding air gap (e3) constant radial during, the two movable armatures (10, 20) being mechanically linked to move simultaneously between the first and the second position. The second magnetic circuit (2) comprises a third and fourth winding (22A, 22B).

Description

TECHNICAL FIELD OF THE INVENTION The invention relates to an electromagnetic actuator comprising a first magnetic circuit comprising a first movable armature moving relative to a first magnetic yoke. Said first armature, movable between a first and a second position is separated from the first magnetic yoke by at least one axial gap. The first magnetic circuit includes a first coil for generating a control magnetic flux to move the first movable armature from the first to the second position. The first magnetic circuit includes a second coil for generating a control magnetic flux to move the first movable armature from the second to the first position. A permanent magnet with radial magnetization generates a polarization flux opposing the magnetic flux generated by the first and second coils. STATE OF THE PRIOR ART Electromagnetic actuators generally comprise a moving part such as a sliding actuating rod, at least one inducing winding exerting a force which displaces the mobile part, an electromagnetic carcass surrounding the winding, but traversed by the rod, where the lines of the magnetic fields are closed. The bistable function of the electromagnetic actuators is also known. Bistable electromagnetic actuators also commonly called hybrid actuators further comprise at least one permanent magnet to maintain the movable part in at least one stable position. The electromagnetic bistable actuators thus comprise a locking function of the mobile part by the closure of a variable air gap biased by the permanent magnet and a motorization function for unlocking and then tilting of the movable part in another stable position. In order to improve the operation of the electromagnetic actuators, manufacturing efforts have focused on the reduction of the residual air gaps today of the order of a few μm, on the optimization of geometrical quantities such as the thicknesses of the sheets, the width and the thickness of the branches of the magnetic structures, on the shape of the air gaps between moving parts and counter parts. The air gap surface is maximized, in particular using bevelled pieces. In addition, the introduction of permanent magnets with high rare earth coercivity (NdFeB) has made it possible to increase the holding forces of the moving part in a stable position, in other words to obtain significant locking forces. Obtaining latching force of the order of the ton allows the new use of electromagnetic actuators in power applications, for example used in the direct control opening / closing of a medium voltage circuit breaker.

However, despite its simplicity of implementation, the particular electromagnetic actuator bistable results from a compromise between the two antinomic functions it must achieve: a locking function and a motorization function of the movable part. In general, a poor locking is observed, if the mobile air gap is deformed according to its section, and / or a derisory motor efficiency, if the mobile air gap deforms according to its fiber. This compromise results from the general properties of the non-polarized reluctant circuits. In the case of a voltage supply of the inductor winding by a voltage source, the setting in motion of the movable part is accompanied by an increase of the self-inductance of the excitation circuit as seen by the voltage source. As shown in the dashed curve of FIG. 7, this increase in the inductance inductance due to the closure of the air gap causes a decrease in the excitation current in the coil during the movement phase and leads to a reduction in the driving force of the electromagnetic actuator. There are therefore two effects penalizing the energy efficiency of the actuator.

On the one hand, the Joule losses in the windings that vary as the square of the current and on the other hand the loss of traction in the phase of movement that extends the duration of the actuation. SUMMARY OF THE INVENTION The invention therefore aims to remedy the drawbacks of the state of the art, so as to propose an electromagnetic actuator with high energy efficiency. The electromagnetic actuator according to the invention comprises a second magnetic circuit magnetically decoupled from said first magnetic circuit and having a second movable armature moving relative to a second magnetic yoke and being separated from said second magnetic yoke by a radial air gap remaining constant during his displacement. The two movable armatures are mechanically linked to move simultaneously between the first and the second position. A third winding is for producing a control magnetic flux for moving the second movable armature from the first to the second position. A fourth coil is adapted to produce a control magnetic flux for moving the second movable armature from the second to the first position. According to a first particular embodiment, the first winding and the third winding are connected in series and are intended to simultaneously produce magnetic control fluxes for moving the first and second movable armatures from the first to the second position. the second winding and the fourth winding are connected in series and are intended to simultaneously produce magnetic control fluxes for moving the first and second movable armatures from the second to the first position. According to a second particular embodiment, the electromagnetic actuator comprises independent means for supplying the first, second, third and fourth coils, the power supply means being intended to simultaneously control the first coiling and the third coiling to move the first coils. and second movable armatures from the first to the second position. The power supply means are intended to simultaneously control the second winding and the fourth winding to move the first and second movable armatures from the second to the first position.

According to a development mode of the invention, the first magnetic yoke comprises at least first E-shaped portion having two outer arms and an intermediate arm comprising the permanent magnet, each outer arm being connected to the intermediate arm by a first section. The first and second coils are respectively positioned on a first section, the first movable armature moving between the outer arms. According to one embodiment of the invention, the first magnetic yoke comprises at least one E-shaped portion having two outer arms and an intermediate arm, each outer arm being connected to the intermediate arm by a first section, the third and fourth coils being respectively positioned on a first section. The second movable armature moves in front of the free end of said arms and is separated from said ends by the radial sliding air gap. Advantageously, the free end of the outer arms comprises a second section perpendicular to said arms, the second movable armature moving parallel to these second sections and being separated from said sections by the radial sliding air gap. According to one embodiment of the invention, the first and the second magnetic yokes are facing each other so that the ends of the outer and intermediate arms of the first yoke are placed facing the end of the arms. of the second breech. According to another embodiment of the invention, the first magnetic yoke comprises two parts each having an E-shape and being placed facing each other so that free ends of the outer and intermediate arms of the first part are placed vis-à-vis a free end of the arms of the second part. Two permanent magnets with radial magnetization are positioned on the intermediate arms. The first and second coils are positioned around the first movable armature moving between the outer arms of the two parts. The second magnetic yoke comprises two E-shaped portions and being placed facing each other so that free ends of the outer and intermediate arms of the first part are placed opposite a free end of the arms of the second part. The third and fourth coils are positioned around the second movable armature moving within the two E-shaped portions and in front of the end of said arms.

Advantageously, the two movable armatures are connected by a hooking bar whose longitudinal axis coincides with that of the moving armatures, said two movable armatures having a same longitudinal axis corresponding to the axis of displacement of said armatures. According to a preferred embodiment of the invention, the first magnetic yoke has a curved E-shape having two outer arms and an intermediate arm, each outer arm being connected to the intermediate arm by a section developing in a first arc. The first movable armature moves between the outer arms in a circular motion. The second magnetic yoke has a curved E shape having two outer arms and an intermediate arm, each outer arm being connected to the intermediate arm by a section developing along a second arc. The second movable armature moves in front of the end of said arms in a circular motion. Advantageously, the two movable armatures are mechanically linked by a hooking bar. BRIEF DESCRIPTION OF THE FIGURES Other advantages and features will emerge more clearly from the following description of particular embodiments of the invention, given by way of non-limiting examples, and represented in the accompanying drawings, in which: FIG. a block diagram of a first preferred embodiment of an electromagnetic actuator in a first operating position; Figures 2 and 3 show schematic diagrams of an electromagnetic actuator according to Figure 1 in intermediate positions; FIG. 4 represents a schematic diagram of the electromagnetic actuator in a second operating position according to FIG. 1; FIG. 5 represents a diagram of the control circuit of the electromagnetic actuator according to a first particular embodiment; FIG. 6 represents a diagram of the control circuit of the electromagnetic actuator according to a second particular embodiment; FIG. 7 represents a curve of the intensity of the electric current flowing in the coil of the electromagnetic actuator according to FIG. 1; Figure 8 shows a block diagram of a first alternative embodiment of the electromagnetic actuator according to Figure 1; FIG. 9 represents a schematic diagram of a second variant embodiment of the electromagnetic actuator according to FIG. 1; FIG. 10 represents a schematic diagram of another variant embodiment of the electromagnetic actuator according to FIG. 1; Figure 11 shows a block diagram of a second preferred embodiment of an electromagnetic actuator in a first operating position; Figure 12 shows a block diagram of a third preferred embodiment of an electromagnetic actuator in a first operating position. DETAILED DESCRIPTION OF AN EMBODIMENT According to all the preferred embodiments as shown in FIGS. 1-4, 11 and 12, the electromagnetic actuator comprises a first magnetic circuit 1 comprising a first movable armature 10 moving relative to each other. at a first magnetic yoke 11. The first deformable magnetic circuit 1 has a variable axial air gap. Said first movable armature 10 between a first and a second position is separated from the first magnetic yoke 11 by at least one axial air gap el, e2. Said first movable armature 10 moves between an open position K1 and a closed position K2. As an example of operation, the closed position K2 as shown in Figure 4 usually corresponds to at least a first air gap el existing between the movable armature 12 and the fixed yoke 11. Generally, a second air gap e2 between l mobile armature 12 and the fixed yoke 11 is then maximum. The closed position K1 as shown in Figure 1 usually corresponds to the maximum of the first gap e1. The second air gap e2 is then minimum. The first magnetic circuit 1 of the electromagnetic actuator comprises a first winding 12A for generating a control magnetic flux ~ 12A for moving the first movable armature 10 of the first K1 to the second position K2. The first magnetic circuit 1 comprises a second winding 12B for producing a control magnetic flux 1128 for moving the first movable armature 10 of the second K2 to the first position K1. The first magnetic yoke 11 comprises at least one permanent magnet 16 with radial magnetization. Said at least one permanent magnet 16 generates a polarization flux DU which opposes the magnetic flux generated by the first and second windings 12A, 12B. The electromagnetic actuator is a bistable actuator with magnetic latching. The electromagnetic actuator further comprises a second magnetic circuit 2 magnetically decoupled from said first magnetic circuit. Magnetic decoupling between the first and the second magnetic circuits 1, 2 means that the coefficient of mutual induction between the two circuits is substantially equal to zero. This decoupling can be achieved by a magnetic shielding, not shown. The second magnetic circuit 2 comprises a second movable armature 20 moving relative to a second magnetic yoke 21. The second movable armature 20 is separated from the second magnetic yoke 21 by a sliding air gap e3. During the displacement of the second movable armature 20, the sliding air gap e3 is constant in a radial direction perpendicular to that of the displacement of said movable armature. The two movable armatures 10, 20 are mechanically linked to move simultaneously between the first and the second position. The second magnetic circuit 2 of the electromagnetic actuator comprises a third winding 22A for producing a control magnetic flux for moving the second movable armature 20 from the first K1 to the second K2 position. The second magnetic circuit 2 includes a fourth winding 22B for producing a control magnetic flux for moving the second movable armature 20 from the second K2 to the second first K1. When the first movable armature 10 moves from a first position K1 to a second position K2 along the longitudinal axis Y, the displacement force F1 applied to the first armature is inversely proportional to the square of the displacement y. Said displacement force can be expressed with the following equation (1):

(1) F10c12 Y The first inductance L1 of the first magnetic circuit 1 is proportional to the ratio between the number of turns N squared and the reluctance of the circuit. Said first inductance L1 can be expressed with the following equation (2):

(2) L1 = N12 R1 The reluctance R1 of the first magnetic circuit 1 is dependent on the displacement y and the gap section S. Said section of the gap e2 is constant throughout the movement. Said reluctance can be expressed with the following equation (3): (3) 911 = Y, uoS With po equal to the permeability of the air. Thus, the inductance L1 of the first magnetic circuit is inversely proportional to the displacement y. Said first inductance L1 can be expressed with the following equation (4): (4) L1 1 Y io When the second movable armature 20 moves from a first position to a second position along the longitudinal axis Y, the force F2 displacement applied to the second armature is constant. The second inductor L2 of the second magnetic circuit 2 is proportional to the ratio between the number of turns N squared and the reluctance of the circuit. Said second inductor L2 can

Expressing itself with the following equation (5): (5) L2 = The reluctance R2 of the second magnetic circuit 2 is proportional to the ratio between the gap e3 and the displacement y. Said gap e3 is constant throughout the movement. Said reluctance can be expressed with the following equation (6): ## EQU1 ## With po equal to the permeability of the air. Thus, the inductance L2 of the second magnetic circuit is proportional to the displacement y. Said second inductance L2 can be expressed with the following equation (7): (7) L2 ay N22 92, uody The equation of the voltage applied simultaneously to the first 12A and third 22A coils is expressed as (8) next :

(8) U = RI + L I

with U the supply voltage, I the current flowing through the windings 12A, 22A and L the total inductance seen by the voltage source. The total inductance is directly dependent on the inductances L1, L2 of the first winding 12A and the third winding 22A. Given the importance of the transient regimes, the resistive term RI is negligible compared to the term dl / dt. Thus, the equation of tension is expressed as follows: (9) U = L dt

Thus, during operation, when the first movable armature 10 moves from a first position K1 to a second position K2 along the longitudinal axis Y, the gap opening e2 causes an inductance reduction L1 of the first circuit magnetic (equation 4). Simultaneously, when the second moving armature 20 moves from a first position to a second position along the longitudinal axis Y, the inductance L2 of the second magnetic circuit tends to increase (equation 7). Given that the inductance reduction L1 of the first magnetic circuit is more significant than the increase of the inductance L2 of the second magnetic circuit, the electric current I flowing through the windings of the first and second coils 12, 22 will increase at the moment where the movable armatures begin to move. As shown in FIG. 7, for comparison purposes, there is shown a first curve TA representative of the excitation current in a known actuator and a second curve TB representative of the excitation current in the actuator according to the invention. It can be seen that the maximum absolute value of the excitation current according to the second curve TB is much lower than that of the first curve TA. In addition, the initiation of the displacement of the movable part of the actuator is faster with an actuator according to the invention (ta> tb). In other words, this means that the device according to the invention allows a better use of the excitation current that is used to move the moving part while compared to the same time, the current in a known device is used to oppose the flow polarization of the gap by the magnet. To avoid any risk of demagnetization of the magnet 16 at the time of unlocking the first movable armature 10, it will be ensured that the operating point of the magnet does not fall beyond the demagnetization characteristic curve of the magnet . The use of rare earth magnets, including Samarium Cobalt SmCo magnets may be recommended for this application. According to a first particular development mode as shown in FIG. 5, to move the first and second movable armatures 10, 20 from the first K1 to the second position K2, the first winding 12A and the third winding 12A are connected in series. The two coils 12A, 22A are then intended to simultaneously produce magnetic control fluxes. According to this first particular embodiment of the invention, for moving the first and second movable armature 10, 20 from the second position K2 to the first position K1, the second coil 12B and the fourth coil 22B are connected in series. The two coils are then intended to simultaneously produce control magnetic flux 0128, cD22B. Switching means 201 allow the alternating connection of the power supply means 200A on the one hand to the first winding 12A and the third winding 22A and secondly to the second winding 12B and the fourth winding 22B. According to a second particular mode of development as represented in FIG. 6, the electromagnetic actuator comprises independent power supply means 200B of the first and second coils 12A, 12B and third and fourth coils 22A, 22B. On the one hand, the independent supply means 200B are intended to simultaneously control the first winding 12A and the third winding 22A to move the first and second movable armatures 10, 20 of the first K1 to the second position K2. On the other hand, the independent power supply means 200B are intended to simultaneously control the second winding 12B and the fourth winding 22B to move the first and second movable armatures 10, 20 of the second K2 to the first position K1. According to a first preferred embodiment of the invention as represented in FIGS. 1 to 4, the first magnetic yoke 11 is E-shaped having two outer arms 13A, 13B and an intermediate arm 14. Said intermediate arm is substantially parallel to the two outer arms 13A, 13B. Each outer arm 13A, 13B has a first end connected to a first end of the intermediate arm 14 by a first section 15A, 15B.

Said first sections 15A, 15B are substantially perpendicular to the outer arms 13A, 13B and intermediate 14. The first winding 12A and the second winding 12B are respectively positioned on a first section 15A, 15B. The first movable armature 10 moves between the outer arms 13A, 13B, substantially perpendicular to said outer arms. The first movable armature 10 is mounted to slide axially and moves along a longitudinal axis Y of displacement. The permanent magnet 16 with radial magnetization perpendicular to the longitudinal axis Y of displacement is then positioned on the intermediate arm 14. The second magnetic yoke 21 also has an E-shape having two outer arms 23A, 23B and an intermediate arm 24. Said intermediate arm is substantially parallel to the two outer arms 23A, 23B. Each outer arm 23A, 23B has a first end connected to a first end of the intermediate arm 24 by a first section 25A, 25B. The third winding 22A and the fourth winding 22B are respectively positioned on a first section 25A, 25B. The second movable armature 20 moves in front of a second free end of said arms. The second movable armature 20 is mounted to slide axially and moves along a longitudinal axis Y of displacement. The second movable armature 20 is separated from the second free end of the outer and intermediate arms 13A, 13B, 14 by the sliding air gap e3. During the displacement of the second movable armature 20, the sliding air gap e3 is constant in a radial direction perpendicular to the longitudinal axis Y of displacement. The longitudinal axis of the second magnetic yoke 21 is common with the longitudinal axis of the first fixed magnetic yoke 11. Preferably, the first and second magnetic yokes 11, 21 are positioned face to face so that the ends free of the outer arms 13A, 13B and intermediate 14 of the first yoke 11 are placed vis-à-vis the free end of the arms 23A, 23B, 24 of the second yoke 21. The two movable frames 10, 20 are linked mechanically by a latching bar 17. According to a first embodiment of the first preferred embodiment, the second end of the outer arms 23A, 23B may comprise a second section 18A, 18B perpendicular to said arms. As shown in FIG. 8, the second movable armature 20 moves parallel to these second sections 18A, 18B and is separated from said sections by the radial air gap e3. This variant embodiment maximizes the surface of the sliding air gap e3. According to a second embodiment of the first preferred embodiment as shown in Figure 9, the magnetic yokes 11, 21 of the two magnetic circuits are of different size. In addition, the first and the second magnetic yokes are positioned opposite each other, but the free ends of the outer arms of the first yoke 11 are not placed opposite the free end of the arms of the second the yoke 21. The movable armature 20 of the second yoke preferably moves inside the magnetic yoke 21. According to another variant of the first preferred embodiment as shown in FIG. 10, the movable armatures of the two circuits Magnetics are in direct contact and are no longer linked by a snap bar. The electromagnetic actuator is thus more compact.

According to a second preferred embodiment of the invention as represented in FIG. 11, the first magnetic yoke 11 is composed of two portions 11A, 11B each having an E-shape. Each part 11A, 11B has two outer arms and one intermediate arm. The intermediate arm is substantially parallel to the two outer arms. Each outer arm has a first end connected to a first end of the intermediate arm by a section. Said sections are substantially perpendicular to the outer and intermediate arms. The two parts are placed vis-à-vis so that second free ends of the outer and intermediate arms of the first part are placed opposite the free end of the arms of the second part. Two permanent magnets 16 with radial magnetization perpendicular to the longitudinal axis Y are then positioned on the intermediate arms. The first and second coils 12A, 12B are respectively positioned around the first movable armature 10. The first movable armature moves between the outer arms the two E-shaped portions. The first movable armature 10 moves substantially perpendicular to said outer arms. The second magnetic yoke 21 is also composed of two parts 21A, 21B each having an E-shape. Each part has two outer arms and an intermediate arm. Said intermediate arm is substantially parallel to the two outer arms. Each outer arm has a first end connected to a first end of the intermediate arm by a section. Said sections are substantially perpendicular to the outer and intermediate arms. The two parts of the second magnetic yoke are placed facing each other so that second free ends of the outer and intermediate arms of the first part are placed opposite a second free end arms of the second part. The third and fourth coils are respectively positioned around the second movable armature moving inside the two E-shaped portions and in front of the second ends of said arms.

The two mobile armatures 10, 20 preferably have the same longitudinal axis corresponding to the longitudinal axis Y of displacement of said armatures 10, 20. The two armatures 10, 20 are interconnected by a hooking bar whose longitudinal axis is preferably confused with that of the movable armatures.

According to a third preferred embodiment of the invention as shown in FIG. 12, the first magnetic yoke 11 has a curved E shape having two outer arms 13A, 13B and an intermediate arm 14. Each outer arm 13A, 13B is connected to the intermediate arm 14 by a section 15A, 15B. Said section develops in a first arc of circle, first arc having a first radius R1. The first and second coils 12A, 12B are respectively positioned on first and second curved sections 15A, 15B. The first movable armature 10 moves between the outer arms 13A, 13B in a circular motion. The center of rotation O around which the moving armature 10 rotates is preferably coincident with the center of the first arc. A permanent magnet 16 with radial magnetization perpendicular to the longitudinal axis Y of displacement is then positioned on the intermediate arm 14. The second magnetic yoke 21 also has a curved E shape having two outer arms 23A, 23B and an intermediate arm 24. Each outer arm 23A, 23B has a first end connected to the intermediate arm 24 by a first section 25A, 25B. Said sections develop in a second circular arc, said second arc having a second radius R2. The third and fourth 22A, 22B of the second coil 22 are respectively positioned on a first curved section 25A, 25B. The center of rotation O around which the second movable armature 20 rotates coincides with the center of the second arc. The second movable armature 20 is separated from the free end of the horizontal outer arms 13A, 13B by the sliding air gap e3. During the displacement of the second moving armature 20, the sliding air gap e3 is constant in a radial direction. The two mobile armatures 10, 20 are mechanically linked by a latching bar 17. The centers of rotation O of the movable armatures 10, 20 are merged.

According to a first particular embodiment shown in FIG. 12, the second mobile armature 20 preferably moves in front of the second end of said arms in a circular motion. The displacement of said second armature is made in a plane preferably coinciding with that of second magnetic yoke 21.

According to a second particular embodiment, the second movable armature preferably moves above or below said arms in a circular motion. The displacement of the second moving armature is made in a plane parallel to that of the second magnetic yoke. The sliding air gap e3 then corresponds to a substantially constant distance between the plane of the second magnetic yoke 21 and that in which the second movable armature rotates. According to an alternative embodiment, the second movable armature comprises a first and second parts interconnected and arranged on either side of the second magnetic yoke. By way of example, the first part is intended to move above the second magnetic yoke and the second part is intended to move below said second yoke.

Claims (9)

REVENDICATIONS1. Electromagnetic actuator comprising a first magnetic circuit (1) comprising: - a first movable armature (10) moving relative to a first magnetic yoke (11), said first movable armature (10) movable between a first and a second position ( K1, K2), being separated from said first magnetic yoke (11) by at least one axial air gap (el, e2), - a first winding (12A) for generating a control magnetic flux (012A) for moving the first mobile armature (10) from the first (K1) to the second (K2) position, - a second coil (12B) for producing a control magnetic flux (O12B) for moving the first movable armature (10) of the second ( K2) at the first (K1) position, 15 - at least one permanent magnet (16) with radial magnetization, said at least one permanent magnet (16) generating a polarization flux ((DU) opposing the magnetic flux (O12A , 012B) generated by the first and cond coils (12A, 12B), characterized in that it comprises a second magnetic circuit (2) decoupled magnetically from said first magnetic circuit and comprising: a second movable armature (20) moving relative to a second magnetic yoke (21 ) and being separated from said second magnetic yoke (21) by a radial air gap (e3) remaining constant during its displacement, • the two movable armatures (10, 20) being mechanically connected to move simultaneously between the first and the second position, - a third winding (22A) for producing a control magnetic flux (O22A) for moving the second movable armature (20) from the first (K1) to the second (K2) position, 30 - a fourth winding (22B) ) being adapted to produce a control magnetic flux (022B) for moving the second movable armature (20) of the second (K2) to the first (K1) position. 17 2. Electromagnetic actuator according to claim 1, characterized in that the first winding (12A) and the third winding (22A) are connected in series and are intended to simultaneously produce magnetic control fluxes (D12A, cP22A) for moving the first and second movable armatures (10, 20) from the first to the second position. the second winding (12B) and the fourth winding (22B) are connected in series and are intended to simultaneously produce magnetic control fluxes (012B, 022B) for moving the first and second movable armatures (10, 20) from the second to the first position. 3. Electromagnetic actuator according to claim 1, characterized in that it comprises independent means for supplying the first, second, third and fourth coils (12A, 12B, 22A, 22B), the power supply means being intended for simultaneously controlling the first winding (12A) and the third winding (22A) to move the first and second movable armatures (10, 20) from the first to the second position; simultaneously controlling the second winding (12B) and the fourth winding (22B) to move the first and second movable armatures (10, 20) from the second to the first position. 4. Electromagnetic actuator according to one of claims 1 to 3, characterized in that the first magnetic yoke (11) comprises at least first E-shaped portion having two outer arms (13A, 13B) and an intermediate arm (14). comprising the permanent magnet (16), each outer arm (13A, 13B) being connected to the intermediate arm (14) by a first section (15A, 15B), the first and second coils (12A, 12B) being respectively positioned on a first section (15A, 15B), the first movable armature (10) moving between the outer arms (13A, 13B). Electromagnetic actuator according to one of the preceding claims, characterized in that the second magnetic yoke (21) has at least one E-shaped portion having two outer arms (23A, 23B) and an intermediate arm (24), each outer arm (23A, 23B) being connected to the intermediate arm (24) by a first section (25A, 25B), the third and fourth coils (22A, 22B) being respectively positioned on a first section (25A, 25B), the second moving armature (20) moving in front of the free end of said arms and being separated from said ends by the radial sliding gap (e3). 6. Electromagnetic actuator according to claim 5, characterized in that the free end of the outer arms (23A, 23B) comprises a second section (18A, 18B) perpendicular to said arms, the second movable armature (20) moving parallel to these second sections and being separated from said sections by the sliding air gap (e3) radial. Electromagnetic actuator according to one of the preceding claims, characterized in that the first and second magnetic yokes (11, 21) are facing each other so that the ends of the outer (13A, 13B) and intermediate ( 14) of the first yoke (11) are placed opposite the end of the arms (23A, 23B, 24) of the second yoke (21). 8. Electromagnetic actuator according to one of claims 1 to 3, characterized in that: - the first magnetic yoke (11) has two portions (11A, 11B) respectively having a shape of E and being placed vis-à-vis so that free ends of the outer and intermediate arms of the first portion (11A) are placed opposite a free end of the arms of the second portion (11B), two magnets (16) permanent to radial magnetization being positioned on the intermediate arms, the first and second coils being positioned around the first movable armature (10) moving between the outer arms the two parts (11A, 11B), - the second magnetic yoke has two parts (21 A, 21 B) being respectively E-shaped and being placed facing each other so that free ends of the outer and intermediate arms of the first part (21A) are placed facing each other. an extr free arm of the arms of the second part (21 B), - the third and fourth coils being positioned around the second movable armature (20) moving inside the two parts (21A, 21B) E-shaped and in front of the end of said arms. 9. Electromagnetic actuator according to claim 8, characterized in that the two movable armatures (10, 20) are connected by a hooking bar whose longitudinal axis coincides with that of the movable armatures, said two movable armatures having a same longitudinal axis corresponding to the axis of displacement of said armatures, 1O.Electromagnetic actuator according to one of claims 1 to 3, characterized in that: the first magnetic yoke (11) has a curved E-shape having two outer arms ( 13A, 13B) and an intermediate arm (14), each outer arm (13A, 13B) being connected to the intermediate arm (14) by a section (15A, 15B) developing in a first arc, 20 - The first armature movable (10) moving between the outer arms (13A, 13B) in a circular motion, - The second magnetic yoke (21) has a curved E shape having two outer arms (23A, 23B) and an intermediate arm e (24), each outer arm (23A, 23B) being connected to the intermediate arm (24) by a section 25 (25A, 25B) developing along a second circular arc, - The second movable armature (20) moving in front of the end of said arms in a circular motion. 11. Electromagnetic actuator according to claim 10, characterized in that the two movable armatures (10, 20) are mechanically connected by a hooking bar (17).