EP1655755B1 - Electromagnetic actuator with movable coil - Google Patents

Abstract

The actuator has a moving vane (20) mechanically connected to a moving coil (30) and including an air gap surface for forming a magnetic air gap of thickness variable with an air gap surface corresponding to a fixed yoke (20). A residual magnetic air gap of constant thickness is formed by two airgap surfaces. An electric current controlling unit controls the position and the speed of the coil and the vane. An independent claim is also included for an electric switch device including an electromagnetic actuator.

Description

The present invention relates to an electromagnetic actuator intended to be used in a switch electrical appliance, in particular in a relay, contactor or contactor-circuit breaker type apparatus.

These electrical switches are usually used to switch the supply circuit of a load or an electric receiver, for example an electric motor, connected downstream of the device. For this, the switch device comprises fixed contacts cooperating with moving contacts and an electromagnetic actuator which moves the movable contacts between a closed position in which they are pressed against the fixed contacts to circulate the supply current in the electric charge. , and an open position in which they are separated from the fixed contacts, thereby cutting off power to the load.

The actuators can use various types of actuation systems based on different magnetic and / or electromagnetic properties. For example, an electromagnet reluctant system is an actuating system frequently used in contactors. It comprises a fixed excitation coil traversed by an electric control current and a variable inductance ferromagnetic circuit comprising a fixed part and a movable part. It can also be polarized by the addition of a permanent magnet.

A reluctant system mainly generates a magnetic force that results from the change in reluctance due to the variation of the gap thickness of the magnetic circuit between the open and closed positions. This force is inversely proportional to the thickness of the magnetic gap. In the closed position, when the thickness of the gap is minimal, the motor force generated is therefore maximum. A low holding current in the coil is then sufficient to oppose the resisting force of the return means (such as return springs and contact pressure springs) and maintain the system in the closed position with a pressure of sufficient contact. Nevertheless, a reluctant system is capable of providing this important motor force only over a very short stroke, generally less than a few millimeters.

Indeed, in the open position, the thickness of the air gap of the magnetic circuit is maximum. To start the closing stroke bringing the movable contacts from the open position to the closed position, a high inrush current in the coil is necessary to create a sufficient motor force capable of attracting the moving part of the magnetic circuit. This can then lead to oversize the entire system (magnetic circuit and coil) with respect to this need for a high inrush current in the coil.

There are already some solutions that can reduce the power consumption of an electromagnet, differentiating the stages of call and maintenance. For example, it is possible to apply a inrush current that is different from the holding current, thanks to resistances that may or may not be present in the electrical control circuit of the coil. One or two coils can also be used to vary the number of ampere-turns according to the steps. Nevertheless, these systems do not allow significant gain in compactness and offer little possibility of adjustment; in particular, they offer no possibility of controlling the speed, the stroke or the force of the actuator.

An electromechanical voice coil actuation system, also called an electrodynamic system, is characterized by a fixed ferromagnetic circuit, a fixed magnet assembly and a voice coil. In this case, the magnetic force is mainly a Laplace force that results from the variation of the mutual inductance between the magnet assembly and the coil. It is proportional to the coil current and the magnetic induction generated by the magnet assembly. Such a system therefore provides a motor force having a good linearity throughout the race between the open and closed positions, for a magnetic flux and a given coil current.

Conversely, this system does not provide a significant additional motor force near the closed position to ensure a good contact pressure of the movable contacts on the fixed contacts of the switch device. It is then necessary to greatly increase the coil current in the closed position, resulting in a significant electrical consumption as well as possible thermal problems.

There are also electromechanical actuating systems with a moving magnet having a fixed ferromagnetic circuit, a fixed coil and a set mobile magnet. In this type of system, it is necessary to permanently ensure a good guidance of the moving magnet which can generate significant friction.

The document US-A-352 5963 discloses an actuator according to the preamble of claim 1.

The invention therefore proposes to improve the existing devices by combining in the same actuator a reluctant system of the electromagnet type with a voice coil system, so as to combine the advantages of these two technologies. This will in particular improve the dynamics of closing movement of an electromagnet through the action of a voice coil system. Conversely, it will also improve the contact pressure of the moving contacts of a voice coil system by the action of an electromagnet.

This is why the invention describes an electromagnetic actuator according to claim 1.

According to one feature, the fixed yoke comprises two lateral flanks and a fixed central core and the magnet assembly is composed of two magnets attached to the lateral flanks symmetrically with respect to the axis of movement of the coil.

According to another characteristic, the actuator comprises control electric current control means for controlling the force applied to the voice coil.

The invention also relates to an electrical switch device comprising one or more fixed contacts cooperating with one or more movable contacts to switch the supply of an electrical load connected downstream of the apparatus and comprising at least one such electromagnetic actuator to actuate the or mobile contacts.

Thanks to the invention, the profile of the curve of the motor force of the actuator is much more suited to the profile of the curve of the resisting force of the moving contacts in a contactor type device. Indeed, the voice coil system provides the necessary motor force during the approach stroke of the movable contacts and the electromagnet provides the additional motor force needed at the end of stroke to press and hold the movable contacts against the fixed contacts. The proposed solution is simple, easy to implement and allows to optimize performance, dimensions and consumption compared to an existing actuator for given characteristics of a device.

• la figure 1 représente une coupe longitudinale simplifiée d'un premier mode de réalisation d'un actionneur conforme à l'invention et en position ouverte,
• la figure 2 montre l'exemple de la figure 1 en position fermée,
• les figures 3 & 4 schématisent deux variantes de la figure 1,
• la figure 5 représente une coupe longitudinale simplifiée d'un second mode de réalisation d'un actionneur en position ouverte,
• la figure 6 montre l'exemple de la figure 5 en position fermée,
• la figure 7 schématise une variante de la figure 6.

Other features and advantages will appear in the detailed description which follows with reference to an embodiment given by way of example and represented by the appended drawings in which:

• FIG. 1 represents a simplified longitudinal section of a first embodiment of an actuator according to the invention and in the open position,
• FIG. 2 shows the example of FIG. 1 in the closed position,
• FIGS. 3 & 4 schematize two variants of FIG.
• FIG. 5 represents a simplified longitudinal section of a second embodiment of an actuator in the open position,
• FIG. 6 shows the example of FIG. 5 in the closed position,
• FIG. 7 schematizes a variant of FIG.

Referring to the first embodiment corresponding to FIGS. 1 & 2, an actuator of a switchgear comprises a fixed yoke 10 of ferromagnetic material which has a U-shape with two lateral flanks 12, 13 and a base 14, as well as a central core 15 which rests on the base 14. The central core 15 is wholly or partially surrounded by an excitation coil 30 which is movable in translation along a longitudinal displacement axis X when a current flows through it electrical control.

The actuator comprises a movable ferromagnetic element, consisting of a movable vane 20 in FIGS. 1 & 2, which is mechanically connected to the coil 30 by connecting means 35. Various conventional connecting means not detailed here can easily be used to secure the moving pallet 20 with the spool The mobile contact (s) of the device are coupled with this mobile arrangement "coil + pallet". The pallet 20 and the coil 30 thus move along the longitudinal axis X between an open position and a closed position in order to actuate movable contacts of the switch device.

The actuator also comprises a magnet assembly which is composed of two magnets 32,33 fixed on the inner wall of the lateral flanks 12, 13, respectively, symmetrically with respect to the longitudinal axis X of the coil. The magnetization axes of the magnets 32, 33 are perpendicular and symmetrical with respect to the X axis, and they are indifferently directed either towards the X axis or opposite the X axis.

The magnetic circuit of the actuator thus comprises a fixed part composed of the fixed yoke 10 and a movable part composed of the moving vane 20. In this first embodiment, the circuit consists of two halves symmetrical with respect to the axis X that generate a magnetic flux B2 when a current flows in the coil 30.

Each magnetic circuit half has a magnetic gap of variable thickness E1 which is formed between the surface of the end of the lateral flanks 12, 13 and the corresponding gap surfaces of the pallet 20 located opposite the end of the flanks 12.13. Each half of the magnetic circuit also has a residual magnetic gap of substantially constant thickness E2 formed between the central core 15 and the pallet 20 by surfaces parallel to the X axis and facing each other. . This residual gap makes it possible not to saturate the magnetic circuit in closed position.

The global air gap of each half of the magnetic circuit is therefore equal to E1 + E2 in the open position and equal to E2 in the closed position, if the pallet 20 is pressed against the sidewalls 12, 13 in the closed position. The path of the magnetic flux B2 is as follows (see FIG. 2): central core 15, base 14, flanks 12, 13, gaps E1 between flanks 12, 13 and pallet 20, airlocks E2 and central core 15. Flow B2 generates an attractive force F _A which is applied to the movable pallet 20 so as to decrease the gap E1.

In addition, each magnet 32,33 creates a magnetic flux B1 (see FIG. 1) which passes through the coil 30, the central core 15, the base 14 and the flanks 12,13 before loop back into the magnets 32,33. Given the axis of magnetization of the magnets 32,33, the flow B1 passes through the coil 30 substantially perpendicular to the longitudinal axis X. Thus, when a control current passes through the coil 30, then it creates a Laplace F _{L force} which tends to move the coil along the X axis. This force F _L is proportional in particular to the control current and does not depend on the position of the coil 30, which causes a regular movement of the coil . This effort can be further easily controlled and regulated by varying the direction and intensity of the control current.

When the actuator is in the open position (FIG. 1) and a control current flows in the coil 30, a force F _L is created which drives the coil 30 in its closing movement. On the other hand, since the thickness of the gap E1 is maximum, the attraction force F _A created by the flow B2 on the pallet 20 is minimal since inversely proportional to the thickness of the gap of the magnetic circuit. Starting the closing movement of the mobile arrangement "coil + pallet" is therefore mainly caused by the force F _L.

As the coil 30 will move closer to the closed position by driving the mobile pallet 20 through the connecting means 35, the air gap E1 will decrease and the force F _A will then increase. When the actuator is in the closed position (FIG. 2), the global air gap of the magnetic circuit is at a minimum and the force F _A applied to the paddle 20 is maximum and is added to the force F _L applied to the coil. .

Thanks to this device, it thus very simply combines a voice coil actuator, for example of the Voice-coil type, capable of providing a smooth movement over the entire travel of the coil with an electromagnet-type actuator capable of providing additional effort. important in the vicinity of the closed position. It is therefore no longer necessary to provide in the coil either a large holding current in the closed position to ensure a satisfactory contact pressure as with a simple voice coil actuator, or a large inrush current in the open position to start the closing movement of the mobile pallet as with a simple electromagnet.

The value E1 of the variable magnetic air gap is, for example, chosen so that the force F _A intervenes substantially during the closing stroke before the movable contacts of the apparatus come into contact with the fixed contacts. This effectively overcomes the increase in the resisting force occurring at this time and can then apply to the movable contacts a sufficient contact pressure, relative to the desired characteristics of the device. The value E2 of the residual air gap is chosen to minimize the saturation of the magnetic circuit in the closed position.

To perform the opening movement (closed position to open position), the actuator may comprise known return means (such as a return spring not shown in the figures) and may additionally send a reverse control current in the coil to better control this movement (for example to accelerate it).

Figure 3 shows a first variant of the first embodiment of the actuator, in the open position. In this variant, replacing the pallet 20, the moving part of the magnetic circuit is now composed of a movable core 21 of ferromagnetic material which is mechanically connected to the voice coil 30. The fixed yoke 10 of the magnetic circuit comprises a base 14 carrying a fixed central core 16 and two lateral flanks 12,13 and a fixed pallet 18 placed transversely on the ends of the flanks 12,13. The pallet 18 comprises a central opening for passing the movable core 21. The variable air gap E1 of the magnetic circuit is formed between the surface of one end of the movable core 21 and the surface of a corresponding end of the fixed central core 16. Preferably, the coil 30 then surrounds the variable gap E1. A residual gap E2 of the magnetic circuit is formed between the movable core 21 and the pallet 18 by their air gap surfaces parallel to the longitudinal axis X vis-à-vis each other.

Moreover, to increase the size of the gap surfaces of the movable core 21 and the fixed core 16 and thus to increase the force F _A , FIG. 3 shows an end of the movable core 21 whose surface 29 is not perpendicular to the axis of displacement X, but which has non-orthogonal inclined shapes with respect to the axis X. The fixed core 16 then obviously has shapes complementary to this air gap surface 29.

Figure 4 shows a second variant of the first embodiment of the actuator, in the closed position. In this variant, the moving part of the magnetic circuit is now composed of a mobile pallet 22 full. The central core 17 of the fixed yoke 10 no longer crosses the pallet 22. The gap of the magnetic circuit is formed between the surfaces of the ends of the lateral flanks 12, 13 and the central core 17 with corresponding surfaces of the pallet 22. maintain a residual air gap in the closed position, non-magnetic shims 23 may for example be placed on the ends of the cylinder head 10.

Various other variants of a magnetic circuit structure could also make it possible to obtain an actuator according to the invention.

The cross section, that is to say in a plane orthogonal to the longitudinal axis X, of the coil 30 may be of substantially circular shape allowing in particular to lighten the structure of the coil, or of substantially rectangular shape in particular to improve the efficiency of the Voice-coil effect.

Figures 5 & 6 show a second embodiment of the invention. In this mode, the electromagnetic actuator of the switch device no longer has two halves of magnetic circuit on either side of the longitudinal axis of displacement X but only one half. The magnetic circuit now comprises a fixed yoke 40 and a movable member 45. A magnetic gap of variable thickness E1 is formed between an air gap surface of the movable member 45 and a corresponding surface of the yoke 40. In the example FIGS. 5 to 7, these gap surfaces are substantially perpendicular to the X axis. A fixed residual magnetic gap is formed between an air gap surface of the movable element 45 parallel to the X axis and a screw surface. to the corresponding screw of the bolt 40.

The fixed magnetic assembly is composed of a magnet 52 which is placed against the fixed yoke 40 and whose magnetization axis is perpendicular to the longitudinal axis X. A coil 50 movable in translation along the X axis is linked Mechanically to the movable member 45. The coil 50 may surround the variable gap E1 (Figures 5 & 6) to better use the effect produced by the coil, but could also surround the magnet 52 (Figure 7). The operation of this actuator is the same as before. In open position (Figure 5), the movement of the coil 50 is obtained mainly by a force F _L generated by the flow B1 of the magnet 52 when a current flows in the coil 50. In the vicinity of the closed position (Figure 6) , the decreasing gap E1 causes the increase of a magnetic force F _A which is added to the force F _L.

Advantageously, the actuator may also have means for regulating the electric control current making it possible to control and regulate the motor force applied to the voice coil so as to be able to control the position and the speed of the mobile part of the actuator. These regulation means can be coupled to means for measuring the power current flowing in the contacts of the device so as to be able to switch the contacts at a predefined time.

For example, following receipt of an order to open the mobile contacts of the apparatus, the regulation means may choose to delay the opening movement until the current flowing in the contacts is less than one. predetermined threshold (switching to zero current). A switch device powered by alternating current and comprising an actuator for each power pole can thus actuate the movable contacts of each pole at different times.

The regulating means also make it possible to slow down the end of the closing movement (possibly by sending an inverted control current in the coil) in order to minimize the risks of bouncing of the movable contacts against the fixed contacts. Other functions for regulating the position and the speed of the arrangement "moving coil + moving element of the magnetic circuit" are obviously possible.

Finally, if a fault occurs during the closing stroke, the regulating means may allow to go back without closing the contacts by reversing the direction of the control current in the coil, which would be impossible with a conventional electromagnet.

It is understood that one can, without departing from the scope of the claims, imagine other variants and refinements of detail.

Claims (15)

1. Electromagnetic actuator for an electrical switch device, comprising:

   - a fixed ferromagnetic yoke (10, 40);

   - a fixed magnetized assembly (32, 33, 52);

   - a coil (30, 50) which can move along an axis of displacement (X) between a first position and a second position under the action of the magnetized assembly (32, 33, 52) when an electrical control current flows through the coil; and

   - a moving ferromagnetic member (20, 21, 22, 45) that is mechanically linked to the moving coil (30, 50) and forms a magnetic gap with the fixed yoke (10, 40), said magnetic gap comprising:

   • a first gap of variable width (E1) between at least one gap surface of the moving member (20, 21, 22, 45) and a corresponding gap surface of the fixed yoke (10, 40) and

   • a second, residual gap of substantially constant width (E2) between a gap surface of the moving member (20, 21, 22, 45) parallel to the axis of displacement (X) and a corresponding gap surface of the fixed yoke (10, 40),

   characterized in that the magnetic gap has a maximum width in the first position of the moving coil (30, 50) and the magnetic gap has a minimum width in the second position of the moving coil (30, 50).
2. Electromagnetic actuator according to Claim 1, characterized in that the fixed yoke comprises two lateral sidewalls (12, 13) and a fixed central core (15, 16, 17) and in that the magnetized assembly is composed of two magnets (32, 33) fixed to the lateral sidewalls symmetrically with respect to the axis of displacement (X) of the coil (30).
3. Electromagnetic actuator according to Claim 2, characterized in that the moving magnetic member is composed of a moving core (21), the first variable gap (E1) being formed between a surface of the moving core and a corresponding surface of the central core (16) of the yoke (10).
4. Electromagnetic actuator according to Claim 3, characterized in that the moving coil (30) surrounds the first variable gap (E1).
5. Electromagnetic actuator according to Claim 2, characterized in that the moving magnetic member is composed of a moving blade (20), the first variable gap (E1) being formed between at least one surface of the moving blade and at least one corresponding surface of the lateral sidewalls (12, 13) of the yoke (10).
6. Electromagnetic actuator according to Claim 5, characterized in that the moving blade (20) has a central opening for passage of the central core (15).
7. Electromagnetic actuator according to Claim 1, characterized in that the magnetized assembly is composed of a magnet (52) placed against the fixed yoke (40).
8. Electromagnetic actuator according to Claim 7, characterized in that the moving coil (50) surrounds the magnetized assembly (52).
9. Electromagnetic actuator according to Claim 7, characterized in that the moving coil (50) surrounds the first variable gap (E1).
10. Electromagnetic actuator according to Claim 1, characterized in that the coil (30, 50) has a cross section of substantially circular shape.
11. Electromagnetic actuator according to Claim 1, characterized in that the coil (30, 50) has a cross section of substantially rectangular shape.
12. Electromagnetic actuator according to Claim 1, characterized in that the gap surface of the moving member (20, 22) is perpendicular to the axis of displacement (X) of the coil (30).
13. Electromagnetic actuator according to Claim 1, characterized in that the gap surface (29) of the moving member (21) is inclined to the axis of displacement (X) of the coil (30).
14. Electromagnetic actuator according to Claim 1, characterized in that the actuator includes means for regulating the electrical control current for controlling the position and the speed of both the moving coil (30, 50) and the moving member (20, 21, 22, 45) .
15. Electrical switch device, which includes fixed contacts cooperating with moving contacts in order to switch the power supply for an electrical load, characterized in that it comprises at least one electromagnetic actuator according to one of the preceding claims in order to actuate the moving contacts.

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