EP1811536B1 - Magnetic actuator with permanent, reduced-volume magnet - Google Patents

Description

TECHNICAL AREA

The present invention relates to a permanent magnet magnetic actuator in particular for operating vacuum bulbs of medium and high voltage circuit breakers. It also relates to a contact control mechanism of one or more vacuum interrupter bulbs which is provided with such an actuator.

STATE OF THE PRIOR ART

Among the magnetic permanent magnet actuators, those known as "planar geometry", for example that described in the patent application, are known. WO 96/32734 which is illustrated in section on the figure 1 . The expression "planar geometry" means that different sections made in several substantially parallel planes of the magnetic circuit of the actuator lead to substantially isometric sections, they are superimposable. This "flat geometry" expression is used to differentiate itself from axyl-symmetric actuators. The disadvantage of axyl-symmetric actuators such as that described in the patent application EP-A-1,225,609 and even in the patent application FR-A-2,504,718 which relates to a self-maintained solenoid is that they are difficult to modulate so as to have ranges of actuators having forces different load bearing. The main parts of the cylinder head, the frame and the permanent magnets can not be reused. The magnets are in an arc which is not easy to achieve. In contrast, in the so-called "planar geometry" actuators, it is possible to easily have a range of actuators with different load-bearing forces, by reusing certain parts such as the yoke, the armature and the permanent magnet. They will keep the same section, only their thickness will vary and this thickness can be obtained by joining several basic elements.

The actuator of the patent application WO 96/32734 is able to maneuver one or more vacuum interrupter bulbs. This actuator comprises a magnetic circuit 1 cooperating with two spaced coaxial coils 2. This magnetic circuit takes the form of two E 3 arranged face to face and a leg 4 between the two E. Each E has a lateral leg 3.4 and three transverse bars 3.1, 3.2, 3.3, two extremes 3.1, 3.3 and an intermediate 3.2, the extreme transverse bars 3.1, 3.3 being longer than the intermediate transverse bar 3.2. The leg 4 is housed in part in a space delimited by the two E and magnetically joins the two extreme transverse bars 3.1, 3.3 of the same E 3. Its displacement is between the two extreme transverse bars 3.1, 3.3 of a even E 3.

The magnetic circuit 1 is materialized by a fixed yoke 5 associated with one or more pairs of permanent magnets 6 also fixed and a movable armature 7. The armature 7 corresponds to the leg 4 of the magnetic circuit 1, it extends along an axis x-x '. The yoke 5 and the pairs of magnets 6 correspond to E. Each magnet 6 is housed in an intermediate transverse bar 3.2 of E between two breech sections 5.

A sectional view of an axyl-symmetric magnetic actuator would be similar, but in fact, in this architecture, the magnetic circuit would comprise two concentric cylinders placed one inside the other, the outer cylinder being closed at its ends by lids .

A disadvantage of the actuator of the figure 1 is that a magnetic flux, which is established in the magnetic circuit due in particular to the presence of the magnets 6, joins the frame 7 to the yoke 5 transversely to the axis x-x '. A small lateral asymmetry of this magnetic flux causes a lateral shift and a rotation along the axis xx 'of the armature 7 towards the intermediate bar 3.2 of one of the E, which reinforces the lateral asymmetry of flux and therefore of 'efforts. These transverse parasitic forces generate friction which must be overcome when controlling the displacement of the armature to move it from one of its stable positions to its other stable position. It is necessary to provide guide parts of the armature, of low friction material, these parts are inserted between the armature and the free end of the intermediate transverse bar E. These parts require mounting a precise positioning, which is delicate.

Another disadvantage of this actuator is that it is bulky and uses a lot of material for a given bearing strength.

Yet another disadvantage of this actuator is that the stroke of its armature is limited since it is between the extreme cross bars of the same E.

In the other two patent applications cited, at certain times depending on the position of the armature, the actuator is also subject to radial parasitic forces and friction that must be taken into account.

Patent Abstract of Japan, vol 2005, No. 12, December 5, 2003, (2003-12-05) shows the preamble of claim 1.

STATEMENT OF THE INVENTION

The present invention aims to provide a permanent magnetic magnet actuator "flat geometry" does not have the limitations and difficulties above. This object is achieved by proposing an actuator in which the configuration of the magnetic circuit is such that the incoming magnetic flux and the magnetic flux exiting the armature are oriented along the axis of the intermediate leg and that the two flows are used. which makes it possible to increase the bearing force of the actuator for the same section of the intermediate leg and the armature. It is recalled that the bearing force of the actuator is the force exerted on the armature during a translation movement, it is expressed in an approximate manner by F = 40.B ² .A with B induction of the coil in Tesla, and has surface gaps between the armature and the rest of the magnetic circuit in cm ² . Force F is expressed in Newton.

• trois jambes dont deux sont extérieures et latérales à la bobine et une intermédiaire traverse la bobine, ces jambes étant sans contact mécanique direct les unes avec les autres,
• ainsi que deux flasques en vis-à-vis reliant magnétiquement entre elles les trois jambes,
• caractérisé en ce que le circuit magnétique se décompose en une armature mobile comportant au moins l'un des flasques et en une partie fixe incluant une culasse englobant au moins l'autre des flasques et au moins un aimant permanent, l'aimant permanent étant placé à une extrémité de la jambe intermédiaire du côté du flasque de la culasse.

More precisely, the actuator according to the invention is in accordance with the object of claim 1. It comprises at least one coil surrounded by a magnetic circuit having:

• three legs, two of which are external and lateral to the reel, and one intermediate passes through the reel, these legs being without direct mechanical contact with each other,
• as well as two flanges vis-à-vis magnetically connecting the three legs,
• characterized in that the magnetic circuit is broken down into a movable armature comprising at least one of the flanges and in a fixed part including a yoke including at least the other of the flanges and at least one permanent magnet, the permanent magnet being placed at one end of the intermediate leg on the flange side of the cylinder head.

The frame and the fixed part have substantially complementary shapes at the level of the three legs.

It is preferable for a good circulation of the magnetic flux that the fixed part further comprises a flux guide piece inserted into the intermediate leg between the magnet and the armature.

The flow guide piece will preferably be made of iron.

The flux guide piece can be broken down into two parts, one with a substantially constant section extending inside the coil and the other with increasing section extending from the coil to the magnet.

The reinforcement can take the form of a plate, a T, a U or an E.

The cylinder head can take the form of a plate, a T, a U or an E.

The frame and / or the breech may at least partially encompass the intermediate leg and / or the outer lateral legs.

In a closed position of the actuator, the armature comes into mechanical contact against the cylinder head, at least at the level of the two outer lateral legs.

It is possible that the cylinder head and / or the frame are laminated, this facilitates the modularity of realization of the actuator.

The cylinder head and / or the frame and / or the permanent magnet are formed of several adjoining pieces.

When the yoke is U-shaped, it can be formed of two L-shaped pieces next to each other.

When the frame is T-shaped, it can be formed of two L-shaped pieces placed back to back.

It is interesting that the flange of the cylinder head has a groove opposite the magnet, to facilitate the attachment of the actuator on a support.

The actuator may be provided with one or more fastening vanes integral with the cylinder head.

The present invention also relates to a contact control mechanism of one or more vacuum interrupter bulbs which comprises an actuator thus defined.

BRIEF DESCRIPTION OF THE DRAWINGS

• la figure 1 représente un actionneur de l'art antérieur ;
• les figures 2A, 2B montrent en coupe premier exemple d'actionneur selon l'invention en position fermée et en position ouverte ;
• les figures 3A à 3F montrent six nouveaux exemples d'actionneur selon l'invention ;
• les figures 4A, 4B montrent un exemple de mécanisme de commande de contacts d'ampoules à vide doté d'un actionneur selon l'invention, cet actionneur étant en position fermée sur la figure 4A et ouverte sur la figure 4B ;
• les figures 5A, 5B permettent de faire une comparaison des dimensions d'un actionneur de l'art antérieur et d'un actionneur selon l'invention.

The present invention will be better understood on reading the description of exemplary embodiments given, purely by way of indication and in no way limiting, with reference to the appended drawings in which:

• the figure 1 represents an actuator of the prior art;
• the Figures 2A, 2B show in section first example of actuator according to the invention in the closed position and in the open position;
• the Figures 3A to 3F show six new examples of actuator according to the invention;
• the Figures 4A , 4B show an example of a control mechanism of vacuum lamp contacts with an actuator according to the invention, this actuator being in the closed position on the Figure 4A and open on the Figure 4B ;
• the Figures 5A, 5B allow a comparison of the dimensions of an actuator of the prior art and an actuator according to the invention.

The different variants must be understood as not being exclusive of each other. Identical, similar or equivalent parts of the different figures described below bear the same numerical references so as to facilitate the transition from one figure to another. The different parts shown in the figures are not necessarily in a uniform scale, to make the figures more readable.

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

We will now describe a first configuration example for the actuator according to the invention.

We refer to Figures 2A, 2B which show sections of a first example of a magnetic actuator according to the invention in two stable positions. This actuator is bistable. On the Figure 2A it is in a stable position under the action of magnetic coupling forces, it is the closed position. On the Figure 2B , it is in the other stable position through the action of springs tending to separate armature and yoke, developing a greater force than that from the magnetic coupling in this position, it is the open position.

By bistable, it means that the actuator has two stable positions in the absence of current in the coil. One could consider that the actuator is not bistable. For example, it could be expected to maintain the closed position if there still circulates a small residual current in the coil. The removal of this current would switch the balance of forces and cause the opening of the actuator.

The actuator comprises at least one coil 14 surrounded by a magnetic circuit 10 having three legs 11, 12.1, 12.2 of which two 12.1, 12.2 are lateral and external to the coil 14 and 11 is intermediate and passes through the coil 14 at least in the closed position. It comprises two flanges 17, 18 vis-à-vis magnetically connecting the legs 12.1, 12.2, 11 between them to close the magnetic circuit 10 especially when the actuator is in the closed position. The legs 12.1, 12.2, 11 are without direct mechanical contact between them. The two outer lateral legs 12.1, 12.2 are oriented substantially perpendicularly to the two flanges 17, 18. When the actuator is in the stable open position, the magnetic circuit 10 is open and three gaps g1, g2, g3 are arranged therein, each leg 12.1, 12.2, 11 cooperating with an air gap g1, g2, g3 respectively. These air gaps g1, g2, g3 extend in the direction of the movement of the armature 21. The coil 14 serves to generate a magnetomotive force which will strengthen or reduce the magnetic field created by the permanent magnet 13 according to which one wish to open or close the actuator.

The magnetic circuit 10 is embodied by a fixed part 200 comprising at least one yoke 22, associated with at least one permanent magnet 13, and with a movable part or frame 21. The yoke 22 includes at least one of the flanges 17 while the armature 21 includes the other flange 18. The permanent magnet 13 is at one end of the intermediate leg 11 on the side of the flange 17 of the cylinder head 22. The permanent magnet 13 may be of the rare earth type for example to neodymium iron boron base.

The movable portion 21 and the fixed portion 200 have substantially complementary shapes so that the magnetic circuit 10 can be closed, minimizing the air gap distances, at least in the closed position of the magnetic actuator.

The arrows drawn on the Figure 2A show the magnetic flux that enters and leaves the armature 21. This flow is directed in the direction of movement of the armature 21 but does not necessarily have the same meaning as the force that applies to the armature 21 and therefore that the displacement of the armature 21. This flux has no moment of component transverse displacement. This characteristic did not exist in the prior art.

It is preferable that the fixed part 200 further comprises a magnetic flux guide piece 15, inserted between the permanent magnet 13 and the armature 21. This flow guide piece 15 is a part of the intermediate leg 11. It is used to concentrate the magnetic flux from the magnet 13 to the frame 21. This flow guiding piece 15 contributes to delimiting one of the air gaps g3. This flux guide piece 15 will preferably be made of steel, because this material has a maximum induction whose value is approximately double that of the rare earth permanent magnet. The attraction force or bearing force being proportional to the square of the induction as explained above, it is advantageous to work at a maximum level of induction at the gap g3.

On the example of Figures 2A and 2B , the armature 21 is T-shaped and the yoke 22 U-shaped. The T comprises a main bar 21.4 and a crossbar. The main bar 21.4 is a part of the intermediate leg 11 and the crossbar is the flange 18. The U has two sides and a bottom. The sides of the U are the outer lateral legs 12.1, 12.2 and the bottom of the U is the flange 17. The intermediate leg 11 is formed from the flange 17 of the yoke 22: the magnet 13, the flow guide piece 15 and the main bar 21.4 of the armature 21. The permanent magnet 13 is substantially parallelepipedal and the flow guide piece 15 also. Other shapes would be possible for the flow guiding part 15 as illustrated in FIGS. figures 3 .

The gaps g1 and g2 are located between the free ends of the sides of the U of the yoke 21 and the ends facing the transverse bar 18 of the T of the armature 21. The third gap g3 is located between the free end of the yoke 21. 21.4 main bar of the frame 21 and the flow guide piece 15. The coupling between the air gap g3 and the coil 14 is good which reduces the electrical or mechanical power required for opening.

When the actuator is closed as on the Figure 2A the armature 21 is in abutment with the bolt 22, and the mechanical contact is preferably between the flange 18 of the armature 21 and the ends of the two sides of the U of the bolt 22 rather than between the armature 21 and the flow guide part 15. On thus avoiding possible shocks at the magnet 13 which is fragile. In any case, the flux guide piece 15, if present, serves as protection for the magnet 13. When the contact is made between the frame 21 and the yoke 22, the gap g3 is as small as possible . It could even be nil. The gaps g1 and g2 determine the travel of the frame 21.

The breech 22 can be made using several pieces contiguous. These pieces can be parallelepipedic. It may be in the example of Figures 2A, 2B flange 17 and two outer lateral legs 12.1, 12.2. These parts 17, 12.1, 12.2 can be massive or laminated, that is to say formed of a stack of plates. Alternatively, it is possible that the yoke 22 is formed of a pair of L-shaped parts placed face to face to form the U. These L-shaped parts are then symmetrical with respect to a plane of symmetry xoz of the T of the armature 21. These L-shaped pieces can be massive or laminated.

In the same way, the armature 21 may be formed of several parallelepipedal parts contiguous. In the example it is the flange 18 and the main bar 21.4 T. These parts can be massive or laminated. Alternatively, the frame 21 may be formed of a pair of L-pieces placed back to back. These L-shaped parts are then symmetrical with respect to the plane of symmetry. These L-shaped pieces can be massive or laminated. The advantage of using for the cylinder head and the frame of the laminated pieces is that it can be stacked more or less to form a range of several actuators.

Regarding the magnet 13, it may be formed of a block or several contiguous, these blocks being parallelepipedic. This characteristic is not seen on the figures 2 the pieces could be following each other in the plane of the sheet. It is schematized on the Figure 5B .

In this way, several actuators having different load-bearing forces can be made by adjusting the stacking thickness of the L-shaped parts of both the armature and the cylinder head.

It is possible to provide in a middle portion of the flange 17 of the yoke 22, a groove 16, opposite the magnet 13. This groove 16 may allow to fix the actuator to an external device. Alternatively or in combination can be fixed one or more fins 42 on the cylinder head 22. These fins 42 may be placed at the outer lateral legs at the end of the stack (if the cylinder head is laminated). These fins 42 provide the rigidity of the actuator and allow its attachment. The fins 42 are visible on the Figures 4A , 4B .

We will see now by referring to Figures 3A to 3F other variants of an actuator according to the invention.

On the figure 3A , the yoke 22, the frame 21 and the magnet 13 have shapes similar to those shown on the Figures 2A, 2B . The flow guide piece 15 has a non-constant section: its face facing The screw of the permanent magnet 13 is larger than that facing the armature 21 to efficiently concentrate the magnetic flux to the armature 21. Its section decreases continuously from the magnet 13 to the armature 21. The faces opposite the armature 21 and the flow guide part 15 are substantially equal in the described configuration. It's not an obligation.

On the figure 3B , the armature 21 is plate-shaped, which corresponds to the flange 18. The fixed part 200 comprises the U-shaped yoke 22, the permanent magnet 13 and the flux-guiding portion 15. The yoke 22 in the form of a plate of U is similar to that of Figures 2A, 2B . The intermediate leg 11 is formed only of the permanent magnet 13 and the flux guide piece 15. With regard to the flow guide piece 15, it comprises two parts 15.1, 15.2 which meet while they are end-to-end, a first portion 15.1 having a substantially constant section and a second portion 15.2 having a decreasing section between the magnet 13 and the armature 21. The second part with decreasing section 15.2 is between the magnet 13 and the reel 14. The two parts 15.1, 15.2 do not have the same section at the junction. The second part 15.2 has a larger section than that of the first part 15.1. The second part 15.2 of the flow guide piece can thus serve as a support for the coil 14.

The gaps g1 and g2 are located between the free ends of the sides of the U of the yoke 22 and the flange 18 of the frame 21. gap g3 is located between the free end of the flow guide piece 15 and the flange 18 of the frame 21.

On the figure 3C , the frame 21 has a U-shape, it includes the two outer lateral legs 12.1, 12.2 and the flange 18. The fixed part 200 comprises the plate-shaped yoke 22 which corresponds to the flange 17, the permanent magnet 13 and the flow guiding member 15. The intermediate leg 11 is formed only of the permanent magnet 13 and the flux guide piece 15. This flow guide piece 15 is similar to that of the figure 3B . The gaps g1 and g2 are located between the free ends of the sides of the U of the frame 21 and the flange 18 of the yoke 22. The third air gap g3 is located between the free end of the flow guide piece 15 and the flange 18 of the frame 21.

On the 3D figure , the armature 21 is E-shaped, it includes two end sections 21.1, 21.2, an intermediate section 21.3 and the flange 18. Each end section 21.1, 21.2 is a first section of one of the outer lateral legs 12.1, 12.2, the intermediate section 21.3 is a first section of the intermediate leg 11. The fixed part 200 comprises the U-shaped yoke 22, the permanent magnet 13 and the flux guide piece 15. The yoke 22 includes a second section 22.1, 22.2 of each of the outer lateral legs 12.1, 12.2 and the flange 18. The intermediate leg 11 is formed, from the flange 17 of the yoke 22, the permanent magnet 13, the flow guide piece 15 and the intermediate portion 21.3 of the armature 21. This flow guiding piece 15 is similar to that of the Figures 2A, 2B but its length is less because of the presence of the intermediate portion 21.3 of the armature 21. The air gaps g1 and g2 are located between the free ends of the sides of the U of the yoke 22 and the ends of the end sections 21.1, 21.2 of the The third gap g3 is located between the free end of the flow guide piece 15 and the intermediate section 21.3 of the movable armature 21.

On the figure 3E , the armature 21 is similar to that shown on the 3D figure . The fixed part 200 comprises the E-shaped yoke 22, the permanent magnet 13 and the flux guide piece 15. The yoke 22 includes two end sections 22.1, 22.2, an intermediate section 22.3, and the flange 18. Each section 22.1, 22.2 is a second section of one of the outer lateral legs 12.1, 12.2. The intermediate section 22.3 of the yoke 22 is a second section of the intermediate leg 11 which further comprises, from this second section, the magnet 13, the flow guide piece 15 and the intermediate section 21.3 of the frame 21. The flow guide piece 15 is similar to that of the 3D figure but its length is less because of the presence of the intermediate portion 22.3 of the yoke 22. The gaps g1 and g2 are located between the ends of the end sections 22.1, 22.2 of the yoke 22 and the ends of the end sections 21.1, 21.2 of the 21. The third gap g3 is located between the free end of the flow guiding part 15 and the intermediate section 21.3 of the frame 21.

On the figure 3F , the armature 21 is similar to that shown on the figure 3C it is U-shaped. The fixed part 200 comprises the T-shaped yoke 22, the permanent magnet 13 and the flux guide piece 15. The T-shaped yoke 22 has a main bar 22.4 and a transverse bar which is the flange 17. The main bar 22.4 is a part of the intermediate leg 11. The U-shaped frame 21 has two sides and a bottom. The sides of the U form the outer lateral legs 12.1, 12.2 and the bottom of the U is the flange 18.

The intermediate leg 11 is formed from the flange 17 of the yoke 22: the main bar 22.4 of the yoke 22, the magnet 13 and the flux guide piece 15. The air gaps g1 and g2 are located between the bar transverse 17 of the yoke 22 and the ends of the outer lateral legs 12.1, 12.2 of the armature 21. The third gap g3 is located between the free end of the flow guide piece 15 and the flange 18 the frame 21. One or more coils 14 surround the assembly of the intermediate leg 11.

We will now be interested in referring to Figures 4A , 4B , to a control mechanism in which the actuator according to the invention takes place. On the Figure 4A , the actuator is closed and on the Figure 4B It is open.

This control mechanism can be used for the control of medium vacuum circuit breakers and high tension. These circuit breakers comprise one or more pairs of contacts 32 placed in a vacuum interrupter 35, among these contacts 32, a 32.1 is mobile and the other 32.2 is fixed.

This control mechanism comprises a first bar 27 to rigidly connect to the armature 21 at its flange 18. This first bar 27 is integral with a pair of substantially perpendicular axes 28, placed towards its ends on the side and side. other of the actuator. These axes 28 are integral with as many levers 34 as vacuum bulbs 35 via a second bar 30. These levers 34 are intended to transmit a movement, depending on the movement of the armature 21, to each movable contact 32.1. a vacuum interrupter 35 of the circuit breaker. These pins 28 serve as guides to the opening springs 29. On this first bar 27 is also connected an external guide system 41 anti-torsion bar type, the first bar 27 being able to pivot laterally around the anti-torsion bar. 41. The first bar 27 is mounted substantially parallel to the anti-torsion bar 41. Because of this movement around the guide system 41, the first bar 27 is caused to drive the frame 21 in a circular arc motion instead of a true translational movement. The actuator is not subject to a radial flow, this movement of the frame 21 is not a disadvantage. Contact springs 33 are mounted, each on an axis 40 which connects a lever 34 to the movable contact 32.1 of the circuit breaker.

The operation of the control mechanism is as follows. It is assumed that the actuator is in the open position. The contacts 32 of each vacuum interrupter 35 are held in the open position by means of the opening springs 29 which are in extension. They are intended to overcome the force, due to the atmospheric pressure, being exerted on the contacts 32 of the vacuum interrupter 35, this force being greater than the magnetic force exerted between the armature 21 and the cylinder head 22. To obtain closing the actuator and thus closing the contacts 32 of the vacuum interrupters 35, a current is injected into the coil 14. This current may come from the discharge of a capacitor (not shown) mounted across the coil 14 This current strengthens the magnetic field created in the gaps g1, g2, g3 by the permanent magnet 13. The attractive force that applies to the armature 21 increases and becomes greater than the mechanical forces that oppose the movement. of the armature 21. The armature 21 begins to move causing the movable contacts 32.1 of the vacuum bulbs 35. The attractive force of the armature 21 towards the flux guide piece 15 follows a complex law which depends on the length of the gaps g1, g2 which define the travel of the armature 21 and the amplitude of the current flowing in the coil 14. The force which opposes the displacement of the armature 21 varies during the stroke of the actuator, especially when touching the contacts 32 Vacuum bulbs 35. Modern calculation means make it possible to completely simulate the behavior of the system and to optimize it.

The actuator and the contacts 32 of the vacuum bulbs 35 are kept closed by the magnetic force exerted by the armature 21, it comes from the magnetic field created by the permanent magnet (not visible on the figures 4 ) in the gap g3 minimum. There is no longer any need for current flow in the coil 14. At this stage, the contact springs 33 and the opening springs 29 are compressed.

The opening of the actuator and therefore of the contacts 32 of the vacuum bulbs 35 is initiated by a current flow in the coil 14. This current flow is in the opposite direction that when the actuator closes, it creates a magnetic field that opposes the magnetic field of the magnet. This flow of current comes from the discharge of the capacitor associated with a polarity inverter, or the discharge of another capacitor (not shown) or even the electrical network, because the required energy is low.

When there are several coils 14, one can be used for opening the actuator and the other for closing. If there is only one, it must be traversed by a current in one direction or the other depending on whether you want the opening or closing of the actuator. On the Figures 3A to 3D , there are two coils represented and on figures 3E and 3F There is only one.

The magnetic bearing force decreases and becomes smaller than the mechanical forces applied to the armature 21 via the pins 28 and the first bar 27. The armature 21 accelerates under the action of the springs of contact 33 and opening 29 which are decompressed. The separation of the contacts 32 from the vacuum bulbs 35 must be done with a sufficient speed so as to cut off any arcing that may occur. Unlike other architectures of the prior art, the actuator provides virtually no energy during opening and the springs must be dimensioned accordingly.

The guide of the armature 21 is made using the anti-torsion bar 41 and the levers 34 which transmit the movement to the movable contacts 32.1 of the vacuum bulbs 35.

It is possible to dispense with the current in the coil 14 to obtain the opening by applying an external mechanical force on the first bar 27 or on a part (not shown) rigidly connected to the movable armature 21, this effort being sufficient to to oppose the magnetic force that applies to the armature 21. The speed of separation of the contacts of the vacuum bulbs is the same during an electric maneuver and a manual emergency maneuver. The coil does not provide power, but accordingly sized aperture springs must be provided.

The Figures 5A, 5B allow a dimensional comparison between two magnetic actuators, one being in accordance with that described in the patent application WO 96/32734 ( Figure 5A ) and the other being in accordance with the invention ( Figure 5B ). The actuator of the Figure 5A has a bearing force of 20 000N and that of the Figure 5B a bearing force of 22,000N. The overall dimensions of the actuator of the Figure 5A are L = 166mm, H = 221mm, P = 400mm, while those of the actuator of the Figure 5B are L = 197mm, H = 205mm, P = 220mm. The smaller size of the actuator according to the invention is not questionable.

It has been seen that the architecture of the actuator which takes into account the inflows and outflows of the armature 21 makes it possible to double the load-bearing force for an identical section of the intermediate leg. The amount of material used by this architecture is reduced compared to that used in the architecture described in the patent application. WO 96/32734 . Such an actuator will have a favorable balance in environmental terms. The section of the breech is about 130% of that of the intermediate leg because the flow through the breech is the same as that through the intermediate leg. For the same number of turns and the same resistance, the section of the coil can be reduced compared to that of the patent application WO 96/32734 because the length of a turn of the coil is proportional to the perimeter of the section of the intermediate leg. The force-position characteristic of the actuator according to the invention makes it particularly suitable for controlling vacuum circuit-breakers.

The drawbacks associated with the parasitic forces that can be applied to the armature do not exist in the structure of the actuator according to the invention. Guiding parts with a low coefficient of friction that are difficult to install are superfluous. The actuator is much less subject to effort parasitic magnetic in case of defective positioning of the armature. The stroke of the frame can easily be adjusted, the breech does not limit this race as in the actuator of the patent application WO 96/32734 .

An appreciable advantage of the actuator according to the invention compared to that described in the patent application EP-A-1,225,609 That is, multiple actuators having different load-bearing forces can be easily obtained by using more or fewer parts to construct the yoke, the frame, and the magnet. These pieces are simple in shape, there are no arc-shaped pieces as found in the patent application EP-A-1,225,609 . The assembly of these parts is simple. The gap g3 between the frame 21 and the flow guide piece 15 is easily controllable because the string of ribs has fewer elements than in the configuration of the patent application. EP-A-1,225,609 . No adjustment is necessary, which was not the case previously where adjustment threads were used.

Although several embodiments of the present invention have been shown and described in detail, it will be understood that various changes and modifications can be made without departing from the scope of the invention.

Claims (16)

1. A magnetic actuator comprising at least one coil (14) surrounded by a magnetic circuit (10) and possessing:

   three legs (12.1, 12.2, 11), comprising two outer legs on either side of the coil (14) and an intermediate leg passing through the coil, these legs having no direct mechanical contact with one another; and

   two facing end plates (17, 18) magnetically interconnecting the three legs (12.1, 12.2, 11);

   the magnetic circuit breaking down into a moving armature (21) comprising at least one of the end plates (18), and a stationary portion (200) including a yoke (22) having at least the other one of the end plates (17) and at least one permanent magnet (13), the permanent magnet (13) being placed at one end of the intermediate leg (11) beside the end plate (17) of the yoke (22), a magnetic flux becoming established between the armature (21) and the stationary portion (200), characterized in that the two outer legs (12.1, 12.2) are parallelepipeds which are substantially orthogonal to the end plates (17, 18) so that said magnetic flux extends along an axis which is an axis along which the armature (21) moves.
2. A magnetic actuator according to claim 1, wherein the armature (21) and the stationary portion (200) are substantially complementary in shape with respect to the three legs (12.1, 12.2, 11).
3. A magnetic actuator according to claim 1 or claim 2, wherein the stationary portion (200) further includes a flux guide part (15) inserted in the intermediate leg (11) between the magnet (13) and the armature (21).
4. A magnetic actuator according to claim 3, wherein the flux guide part (15) is made of an iron-based material.
5. A magnetic actuator according to one of claims 3 or 4, wherein the flux guide part (15) comprises two portions (15.1, 15.2), one of the portions (15.1) being of substantially constant section and extending inside the coil (14), and the other portion (15.2) being of increasing section and extending from the coil (14) towards the magnet (13).
6. A magnetic actuator according to one of claims 1 to 5, wherein the armature (21) is in the form of a plate, a T-shape, a U-shape, or an E-shape.
7. A magnetic actuator according to one of claims 1 to 6, wherein the yoke (22) is in the form of a plate, a T-shape, a U-shape, or an E-shape.
8. A magnetic actuator according to one of claims 6 or 7, wherein the armature (21) and/or the yoke (22) include, at least in part, the intermediate leg (11) and/or the outside legs (12.1, 12.2).
9. A magnetic actuator according to one of claims 1 to 8, wherein when the actuator is in the closed position, the armature (21) comes mechanically into contact with the yoke (22), at least via the two outside legs (12.1, 12.2).
10. A magnetic actuator according to one of claims 1 to 9, wherein the yoke (22) and/or the armature (21) are laminated.
11. A magnetic actuator according to one of claims 1 to 10, wherein the yoke (22) and/or the armature (21) and/or the permanent magnet (13) are built up of a plurality of touching parts.
12. A magnetic actuator according to claim 11, wherein the yoke (22), when U-shaped, is made up of two L-shaped parts touching face to face.
13. A magnetic actuator according to one of claims 11 or 12, wherein the armature (21), when it is T-shaped, is made up of two L-shaped parts touching back to back.
14. A magnetic actuator according to one of claims 1 to 13, wherein the end plate (17) of the yoke (22) includes a groove (16) in its face remote from the magnet (13).
15. A magnetic actuator according one of the preceding claims, wherein it is provided with a plurality of fastening flanges (42) secured to the yoke (22).
16. A mechanism for controlling the contacts (32) of one or more circuit breaker vacuum chambers (35), wherein it includes an actuator according to one of the preceding claims.

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