EP3279907B1 - Electromagnetic actuator for an electric contactor - Google Patents

Description

The present invention relates to an electromagnetic actuator for an electrical contactor.

FR-A-2 792 108 discloses an electromagnetic actuator intended to be integrated into a direct current contactor. This actuator comprises a fixed part and a movable part. The fixed part comprises a coil, which is arranged on an insulating casing and which generates a magnetic field when supplied with current. The mobile part is designed to move in translation under the effect of the magnetic field generated by the coil. It comprises a magnetic core of generally cylindrical shape and armatures in the form of pallets. The pallets are arranged at two ends of the core and are integral with the latter. A contact carrier is linked in translation with the mobile part. The contacts of this contact carrier are connected with fixed contacts of the contactor when moving the moving part, which has the effect of closing the contactor circuit. One or more springs make it possible to return the movable part to the open position when the coil is no longer supplied with current.

A first drawback of this actuator is that the movable part is heavy because it comprises a core and two vanes. The opening and closing time is therefore relatively long. Besides, the moving part has a lot of copper, so this actuator is relatively expensive to manufacture.

On the other hand, the stroke of the movable part depends on several dimensions and in particular on the distance between the two pallets. However, this distance varies significantly over a batch of products. Thus, a second drawback of this product is that the stroke of the movable part between its open position and its closed position is poorly controlled. The corresponding opening and closing times therefore vary from one product to another.

FR 3 026 222 A1 discloses an electromagnetic actuator, a movable part of which, which is movable along an axis with respect to two fixed cores while being arranged axially opposite the latter, consists of a flat rectangular pallet.

US 2010/0245002 A1 discloses an electromagnetic actuator which, at its movable part, is similar to that of FR 3 026 222 A1 .

In this context, the invention proposes an electromagnetic actuator having a movable part which, while being economical to manufacture, makes it possible to better control the opening and closing times.

To this end, the subject of the invention is an electromagnetic actuator for an electrical contactor, as defined in claim 1.

Thanks to the invention, the mobile part is much lighter than that of the electromagnetic actuator according to FR-A-2 792 108 . The mechanical force required to return the movable part to the open position is therefore less. In addition, less raw material is used for the manufacture of the moving part. This therefore has a lower manufacturing cost. Furthermore, the fact that the movable part is constituted by a flat part, cut from a rolled sheet, makes it possible to obtain reduced tolerance margins with regard to the thickness of the flat part. The amplitude of the travel of the movable part between the open position and the closed position is therefore better controlled. When the contactor is closed, the peripheral parts of the flat part are crossed by the magnetic flux at the start of movement (increase in the take-up surface). The induction level of this zone remains low (less than 1 Tesla). The more the air gap (the distance between the fixed part and the moving part) decreases, the more the field lines are channeled towards the center of the pallet. The strong inductions are concentrated in the center of the palette. The outside of the pallet is very lightly stressed. Thus, there is no need to have as much thickness on the edges of the flat part as in the center. The fact that the second floor has a solid section smaller than that of the first floor makes it possible to lighten the room at the level of at least one of its edges. The idea is to remove material that does not conduct the magnetic flux when closing the contactor to lighten the flat part as much as possible, without however altering the closing capacities of the actuator.

FR 2 586 324 A1 discloses an electromagnet in which the movable part is formed by two magnetic plates arranged symmetrically on either side of a coil axis. US 5,235,303 discloses an electromagnetic actuator in which the movable part comprises a guide rod, a movable pole, a demagnetizing wedge and an upper disc-shaped frame. It is therefore understood that, in each of these two documents, the moving part is not constituted by a single flat part.

The subject of the invention is also an electrical contactor, as defined in claim 7.

Advantageous but not mandatory aspects of the invention are specified in the other claims.

• la figure 1 est une coupe d'un contacteur électrique conforme à l'invention, représenté en position ouverte et comprenant un actionneur électromagnétique avec une partie fixe et une partie mobile, conforme à l'invention,
• la figure 2 est une coupe analogue à la figure 1, dans laquelle le contacteur est représenté en position fermée, et
• les figures 3 et 4 sont des vues en perspective représentant une partie mobile de l'actionneur des figures 1 et 2.

The invention and other advantages thereof will emerge more clearly in the light of the following description of an embodiment of an electromagnetic actuator in accordance with its principle, given solely by way of example and made in reference to the accompanying drawings in which:

• the figure 1 is a sectional view of an electrical contactor according to the invention, shown in the open position and comprising an electromagnetic actuator with a fixed part and a movable part, according to the invention,
• the figure 2 is a cut analogous to the figure 1 , in which the contactor is shown in the closed position, and
• the figures 3 and 4 are perspective views showing a movable part of the actuator of the figures 1 and 2 .

On the figures 1 and 2 an electric contactor 2 is shown, making it possible to selectively interrupt the flow of current in a power circuit, for example between a power source and an electric load. To the figure 1 , the contactor 2 is shown in an open position, in which it blocks the flow of current. The contactor 2 comprises a number of movable contacts 12 and a corresponding number of fixed contacts 14. In the example, this number is equal to two but this number may vary depending on the type of device.

The movable contacts 12 belong to a contact holder 10 which is movable along an axis X10 between the open position shown in figure 1 , in which the movable contacts 12 and the fixed contacts 14 are separated by an isolation distance and a closed position shown in figure 2 , wherein the movable contacts 12 and the fixed contacts 14 are in contact and connected. The contact carrier 10 is moved in translation along the axis X10 by means of an electromagnetic actuator 4.

The electromagnetic actuator 4 comprises a fixed part 6 and a part 8 movable along the axis X10 between the open position shown in figure 1 and the closed position shown in figure 2 . The stroke of the movable part 8 is represented by the distance c from the figure 1 .

The contact carrier 10 and the movable part 8 of the actuator 4 are linked in translation along the axis X10. In the example, the part 8 of the actuator is assembled on the contact carrier 10 so as to make it integral with the contact carrier.

The fixed part 6 comprises a frame 60 having a U-shaped architecture. The frame 60 therefore comprises a base and two cores 61 which extend, from the base, parallel to the axis X10. A coil 62 is wound around each of the cores 61. When they are supplied with electric current, the coils 62 generate a magnetic field which attracts the movable part 8 of the actuator 4 towards the fixed part 6.

The electromagnetic actuator 4 comprises means for returning the movable part 8 to the open position. In the example, these return means are formed by two helical springs 24, which extend between the fixed part 6 and the movable part 8. The springs 24 are compression springs. For clarity of the drawings, the springs 24 are not shown in figure 2 .

The contactor 2 comprises a base 16 and an arc box 18 fixed to the base 16. The base 16 surrounds the fixed part 6 of the actuator 4. In the open position, a part of the contact holder 10 bears against the box. arc 18, while in the closed position, the movable part 8 is in contact with the fixed part 6 of the actuator 4.

The contactor 2 also comprises holding means for maintaining the fixed part 6 of the actuator 4 in contact with the arcing box 18. More precisely, the fixed part 6 of the actuator is held in contact with tabs 180 belonging to the box. arc 18. The tabs 180 are distributed around the axis X10. There are 4 in the example.

The aforementioned holding means comprise at least one elastic element 22, preferably two elastic elements 22. In the example, the elastic elements 22 are elastomeric stoppers. Each plug 22 extends from the base 16 and passes through an electronic card 20 via through holes made in the card 20 for this purpose. The electronic card 20 is therefore placed between the base 16 and the fixed part 6 of the actuator 4. It comprises a support in polychlorinated biphenyls (PCB).

The holding means 22 make it possible to “reference” or “polarize” the fixed part 6 of the actuator 4. This means that, on a batch of products, the fixed part 6 of the actuator 4 has the same position as it does. whatever the contactor of the batch considered. Thus, the end point of the stroke c of the movable part 8 between the open position and the closed position is therefore well defined. This contributes to improving the control of the amplitude of the stroke c of the moving part 8 between the open position and the closed position and therefore, consequently, to improving the control of contact crushing as well as a repeatability of the times of opening and closing.

As visible to figures 3 and 4 , the movable part 8 of the electromagnetic actuator 4 consists of a flat part made of sheet metal. By the use of the verb “constitute” is meant here that the movable part comprises only one part, which is the flat sheet metal part. By flat part is meant that it is a part obtained from a rolled sheet.

The flat part 8 is stepped: it comprises a first stage 80 intended to be turned towards the fixed part 6 of the electromagnetic actuator 4 and a second stage 82 intended to be turned, on the opposite side, towards the arc box 18. The second stage 82 is contiguous to the first stage 80 along the axis X10. This means that the first stage 80 and the second stage 82 are perpendicular to the axis X10 and that there is no void between the first stage 80 and the second stage 82. A solid section of the second stage 82, measured in a plane perpendicular to the axis of movement X10 of the mobile part 8, is less than a solid section of the first stage 80. The solid section is the area delimited by the contours in the section plane. Thus, any holes in the first stage 80 or in the second stage 82 are not taken into account in the calculation of the area. This therefore means that the area delimited by the contour of a section of the second stage 82 in a section plane perpendicular to the axis of displacement X10 of the mobile part 8 is less than the area delimited by the contour of a section of the first stage 80 in a section plane perpendicular to the axis of movement X10 of the mobile part 8.

Typically, the two stages 80 and 82 of the flat part 8 are made of ferromagnetic material, in particular of ferromagnetic sheet.

The ratio between the solid section of the second stage 82 and the solid section of the first stage 80 is dimensioned by simulation as a function of the flux to be passed and of the ferromagnetic material used. It is between 25% and 75%, preferably equal to 50%. This means that the ratio between the area delimited by the contour of a section of the second stage 82 in a section plane perpendicular to the axis of displacement of the movable part and the area delimited by the contour of a section of the first stage 80 in a section plane perpendicular to the axis of movement of the mobile part, is between 25% and 75%, preferably equal to 50%.

In the example, the flat part 8 only has two floors. As a variant not shown, the flat part may have a number of stages strictly greater than two. A floor corresponds to a part of the flat part 8 having a solid section different from at least another part of the flat part.

The first stage 80 delimits a surface S80 intended to be oriented towards the fixed part 6 of the electromagnetic actuator 4. In the example, the surface S80 is intended to come into contact with the fixed part 6 of the actuator 4. However, , alternatively, a part could be interposed between parts 6 and 8 in the closed position. The second stage 82 defines a surface S82 opposite to the surface S80. The surface S82 faces the arcing case 18 of the contactor 2 in the assembled configuration. The surfaces S80 and S82 are substantially planar.

The second stage 82 is disposed substantially centrally. In other words, the second stage 82 covers only a central part of the first stage 80, which makes it possible to maintain a sufficient passage section in the center of the pallet. On the other hand, at least one of the edges of the part 8 is delimited exclusively by the first stage 80 and has a thickness less than a maximum thickness of the part.

The thickness of the flat part 8 is therefore not homogeneous. In the example, the saving in terms of mass compared to a pallet with a homogeneous thickness is of the order of 15%. This does not or almost does not affect the magnetic performance since, when the contactor 2 is closed, most of the magnetic flux generated by the coils 62 passes through the central part of the flat part 8. The induction level on the coils edges of the flat part 8 is therefore not very high. The thickness of the edges can therefore be reduced without however causing magnetic saturation which can modify the magnetic behavior of the flat part 8 on closing. In other words, only the material which does not or only slightly conducts the magnetic flux when the contactor is closed is removed. This makes it possible to obtain a light moving part.

Advantageously, the flat part is a rectangular pallet comprising two small sides and two large sides. The two small sides form two opposite edges B1 and B2 of the mobile pallet 8. The two large sides form two opposite edges B3 and B4. The edges B1 and B2 have a reduced thickness compared to a central zone of the pallet 8 where the thickness is maximum. The edges B1 and B2 are delimited exclusively by the first stage 80 of the pallet 8, while the edges B3 and B4 are jointly delimited by the two stages 80 and 82. The surface S80 has a length, measured parallel to the long edges B3 and B4, which is greater than the length of the surface S82.

Thanks to the lightening of material, the opening time of the contactor 2 is shorter than when using a non-lightened moving part. Furthermore, the closing time is substantially identical since the magnetic behavior of the lightened pallet 8 is not or only slightly affected.

In the example, the thickness of the first stage 80 is identical to the thickness of the second stage 82. The thickness of the edges B1 and B2 is therefore equal to half the maximum thickness of the part 8. More generally, the thickness of the first stage 80 must be dimensioned according to the admissible saturation in the edges with respect to the maximum thickness of the pallet 8. In practice, the thickness of the first stage 80 is between 25% and 75% of the maximum thickness of the pallet 8, in particular between 35% and 55%.

Advantageously, the two floors of the flat part 8 are formed by two pieces of superimposed sheet metal 80 and 82. The sheet metal part 82 is shorter than the sheet metal part 80, the length being measured parallel to the long sides B3 and B4 of the pallet 8. In the example, the two pieces of sheet 80 and 82 are welded to one another, in particular by means of a laser welding process.

Advantageously, the second stage 82 has a length L82 at least equal to the length L61 of the fixed part 6, this length being measured at the level of the cores 61. The lengths L82 and L61 are measured in a direction perpendicular to the axis X10. and included in the plan of the figure 1 . Thus, the second stage 82 comprises parts which are axially facing the cores 61 of the fixed part 6.

In the assembled configuration within the electrical contactor, the sheet metal part 80 is oriented on the side of the fixed part 6 of the actuator 4, while the sheet metal part 82 is oriented on the side of the arc housing 18, that is, i.e. on the side opposite to the fixed part 6 of the actuator 4.

Advantageously, the flat part 8 comprises at least one magnetic flux concentrator, preferably at least three magnetic flux concentrators.

In the example, the flat part includes four magnetic flux concentrators. These four flow concentrators are placed at the four corners of the pallet 8.

Each flow concentrator is a relief 80.2 formed on a face S80 of the pallet 8 oriented towards the fixed part 6 of the actuator 4. The reliefs 80.2 form bearing surfaces of the mobile part 8 on the fixed part 6. Advantageously , each relief 80.2 is formed by stamping sheet metal. The reliefs 80.2 arranged on the side of the edge B3 are oblong and round: they extend parallel to the edges B1 and B2 of the pallet 8. The reliefs 80.2 arranged on the side of the edge B4 are circular in shape.

The reliefs 80.2 channel the magnetic flux generated by the coils 62. In fact, approximately 95% of the magnetic flux passes through the reliefs 80.2. This makes it possible, on the one hand, to optimize the magnetic force which maintains the movable part 8 in the closed position and thus to limit the consumption of the coils 62 and, on the other hand, to potentially limit the residual effects, that is to say that is to say the capacity of the pallet 8 to retain its magnetization.

Advantageously, each magnetic flux concentrator 80.2 is arranged so as to be axially facing one of the cores 61 of the fixed part 6. This promotes the passage of the magnetic flux through the flux concentrators 80.2.

As a variant not shown, an effect of the same type can be obtained by using a part made of non-magnetic material interposed between the fixed and mobile parts, respectively 6 and 8, of the actuator 4.

The sheet metal part 80 delimits two through holes 80.1 for the passage of one end of the return springs 24. The springs 24 bear against the lugs 82.1 of the second sheet metal part 82, which is arranged above the part. sheet 80.

According to another variant not shown, the first stage 80 and the second stage 82 are in one piece. The movable part of the actuator is then formed by a one-piece flat part.

The rectangular pallet 8 is manufactured as follows. The two sheet metal pieces 80 and 82 are cut separately from rolled sheet. The sheet metal part 80 is then stamped for the formation of the reliefs 80.2 and drilled for the formation of the holes 80.1. The two sheet metal pieces 80 and 82 are then welded together, for example using a laser welding process. Advantageously, the weld beads are produced at the level of the orifices 80.1 and on part of the edge B3.

As a variant, an electrical spot welding process can also be used to join the two pieces of sheet metal 80 and 82. In this case, the weld spots are formed at the level of reliefs arranged on the face of the piece of sheet metal. 82 which is in contact with the sheet metal part 80. Four welding points are then sufficient.

The two sheet metal pieces 80 and 82 can also be glued, riveted or screwed together.

The features of the embodiment and of the variations contemplated above may be combined with each other to generate new embodiments of the invention, as long as they are included within the scope of the appended claims.

Claims (9)

1. Electromagnetic actuator (4) for an electrical contactor (2), the electromagnetic actuator comprising a fixed part (6) and a movable part (8) which is movable relative to the fixed part along an axis of movement (X10), the fixed part comprising two cores (61), which extend parallel to the axis of movement (X10), and two coils (62), one of which is wound around one of the cores while the other coil is wound around the other core,

   the movable part (8) being

   formed of a flat piece

   (8), for example cut from rolled sheet metal, the flat piece being a rectangular pallet, which delimits two long edges (B3, B4) and two short edges (B1, B2), and comprising:

   - a first stage (80), which is made of ferromagnetic material, in particular ferromagnetic sheet metal, and which faces the fixed part (6) along the axis of movement (X10), being arranged opposite the cores (61) along the axis of movement, and

   - a second stage (82), which is made of ferromagnetic material, in particular ferromagnetic sheet metal, and which is adjacent to the first stage in the direction of the axis of movement (X10), being oriented away from the cores (61),

   the area delimited by the contour of a section of the second stage (82) in a sectional plane perpendicular to the axis of movement (X10) being smaller than the area delimited by the contour of a section of the first stage (80) in a sectional plane perpendicular to the axis of movement, and the second stage (82) having a length, measured parallel

   to the long edges (B3, B4), which is less than the length of the first stage (80).
2. Actuator according to claim 1, characterized in that the ratio between the area delimited by the contour of a section of the second stage (82) in a sectional plane perpendicular to the axis of movement (X10) and the area delimited by the contour of a section of the first stage (80) in a sectional plane perpendicular to the axis of movement is between 25% and 75%.
3. Actuator according to one of the preceding claims, characterized in that the first and second stages of the flat piece (8) are formed by two superimposed sheet-metal pieces (80, 82).
4. Actuator according to one of the preceding claims, characterized in that the flat piece (8) comprises at least one magnetic flux concentrator (80.2) which is arranged so as to face one of the cores (61).
5. Actuator according to the preceding claim, characterized in that each flux concentrator is a relief (80.2) formed on a surface (S80) of the flat piece (8) facing the fixed part (6).
6. Actuator according to one of the preceding claims, characterized in that the second stage (82) has a length (L82) at least equal to the length (L61) of the fixed part, measured at the level of the cores (61).
7. Electrical contactor (2) comprising an actuator according to the preceding claim.
8. Electrical contactor (2) according to the preceding claim, comprising an arcing box (18) and means (22) for holding the fixed part (6) of the actuator (4) in contact with the arcing box, these means comprising for example at least one resilient member (22).
9. Contactor according to the preceding claim, characterized in that these means comprise at least one resilient member (22) and in that each resilient member (22) extends from a base (16) of the contactor and passes through an electronic board (20) disposed between the base (16) and the fixed part (6) of the actuator.

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