Normally closed power contactor

Abstract

The invention relates to a power contactor comprising a fixed part and a mobile part able to move in translation relative to the fixed part under the activation of a linear actuator (12) and in a direction of displacement, between a contact position and a breaking position, the contact position forming a normally closed rest position of the contactor, the displacement of the mobile part carrying along a mobile contact (24) so as to separate it from a fixed contact (26) facing it in an extinguishing chamber (22), by compressing a contact compression spring (28) and a core return spring (30), characterized in that, in order to avoid any rebounding of the mobile part when the linear actuator returns to its rest position, a magnetic holding member fixes this mobile part in the contact position before it rebounds due to the springs.

Description

[0001] Description

[0002] Title of the invention: Normally closed power contactor

[0003] Technical Field

[0004] The present invention relates to the field of power switching components and more particularly concerns a normally closed spring electromechanical power contactor.

[0005] Prior art

[0006] A power contactor is an electromechanical device comprising, in the case considered here, a linear actuator acting via an operating rod on the movement of movable contacts towards fixed contacts, both facing each other in a breaking chamber of the contactor. The movement of the operating rod from a rest position in which the movable contacts and the fixed contacts are in mechanical contact (we are talking here about a so-called "normally closed" contactor in which an electric current can flow between the power contacts thus closed when the actuator is not activated) to a cut-off position (after a stroke of the order of <3 mm), in which the movable contacts separate from the fixed contacts, preventing the flow of current, is carried out by the electrical supply of a coil.The coil returns a movable core carrying the operating rod towards a yoke and against both a contact pressure spring acting on the movable contacts and a core return spring mounted between the armature and the core secured to a flux return yoke receiving the coil.

[0007] When the actuator's power supply is cut off, the moving contacts will return to their initial rest position and close on the fixed contacts. The moving core, the operating rod and the moving contacts then together form a mass suspended from the core return spring which, due to this deactivation, undergoes a shock with the fixed contacts and then oscillations linked to the damping coefficient of this spring, causing the moving contacts to bounce and significantly reducing the performance of the contactor, possibly leading to the contacts sticking together, rendering the contactor inoperative.

[0008] A common solution to avoid these bounces is to increase the stiffness of the springs, particularly the core return spring. However, this solution, while seemingly simple to implement, requires a much more powerful and therefore larger and heavier actuator, which is not acceptable for use in aeronautical electrical circuits.

[0009] Statement of the invention

[0010] The main aim of the present invention is therefore to propose a power contactor which can overcome the usual bounces when returning to its initial rest state and therefore improve the closing power (maximum current for which the contacts can close without welding). Another aim is to obtain this result without modifying the actuator, the breaking chamber or the mechanical properties of the contactor and in particular those of these springs.

[0011] These aims are achieved by a power contactor comprising a fixed part and a part movable in translation relative to the fixed part under the activation of a linear actuator and in a direction of movement, between a contact position and a cut-off position, the contact position forming a normally closed rest position of the contactor, the movement of the movable part carrying a movable contact to separate it from a fixed contact facing it in a cut-off chamber, by crushing a contact pressure spring and a core return spring, characterized in that, to prevent any rebound of the movable part when the linear actuator returns to its rest position, a magnetic effect holding member fixes this movable part in the contact position before it rebounds due to the springs.

[0012] Thus, the addition of a magnetic retainer prevents sticking between contacts and increases the breaking capacity under short-circuit current. Rebounds are eliminated without modifying the elastic properties of the springs in place. Preferably, the magnetic retainer is mounted outside the arc chute.

[0013] Advantageously, the magnetic effect holding member comprises two magnets each framed by two plates and a magnetic return, the magnetic return being integral with the moving part and the direction of magnetization of each of the two magnets is configured to each exert a magnetic force in the direction of movement.

[0014] Preferably, the plates and magnetic return are made of pure iron or low alloy steel.

[0015] Advantageously, the magnetic force exerted jointly by the two magnets is less than 5 Newtons.

[0016] Preferably, the pads are positioned between a low stop and a high stop with a maximum clearance Jb, Jb being greater than a mechanical clearance Ja existing between the pads and the magnetic return.

[0017] Depending on the embodiment envisaged, the contactor may be multi-pole, typically bipolar or tripolar, then either a single magnetic effect holding member retains the moving part of all the poles or the power contactor comprises a magnetic effect holding member per pole.

[0018] Brief description of the drawings

[0019] Other characteristics and advantages of the present invention will emerge from the description given below, with reference to the appended drawings which illustrate an exemplary embodiment thereof without any limiting character and in which:

[0020] [Fig. 1] Figure 1 illustrates a power contactor according to the invention,

[0021] [Fig. IA] Figure IA details the magnetic effect holding member of the contactor of Figure 1, and

[0022] [Fig. 2] Figure 2 is a side view of the magnetic effect holding member of Figure 2 mounting the clearance compensation device. Description of Embodiments

[0023] As explained in the preamble, in a normally closed spring-loaded power contactor, bounces on closing are a recurring problem. The principle of the invention is based on the addition of a magnetic effect holding member which makes it possible to eliminate these bounces without modifying the mechanical properties of the contactor. This freezes the moving masses in the closed position before these masses bounce due to the springs. More precisely, the magnetic effect holding member makes it possible to prevent bounces of the moving part of the contactor and, consequently, the unwanted transmission of bounces to the moving contact.

[0024] The mechanical properties of the contactor are not affected because neither the breaking chamber nor the contactor actuator, which constitute the critical elements, are modified.

[0025] Figure 1 illustrates a normally closed power contactor in the rest position according to the invention.

[0026] Such a power contactor 10 conventionally comprises a fixed part and a part movable in translation relative to the fixed part under the action of a linear actuator 12 and in a direction of movement, between a contact position and a cut-off position, the contact position forming the normally closed rest position of the contactor. The linear actuator is mounted in a pot-shaped body 14 closed at one end by a yoke 16 and in which is guided a movable core 18 emerging from the body at its other end, the movable core carrying at its end an operating rod 20 penetrating a breaking chamber 22 closed by a cover 22A. On the operating rod is mounted a movable contact 24 supporting the movable contact pads 24A.These movable contact pads face in the breaking chamber fixed contact pads 26A connected to a fixed contact 26 and held in contact by a contact pressure spring 28 bearing between the movable contact and an internal wall of the breaking chamber. Between the yoke 16 and the movable core 18 is mounted a core return spring 30. According to the invention, the magnetic effect holding member 40 is mounted on the operating rod 20 between the body 14 receiving the actuator 12 and the breaking chamber 22, in order to create a sufficient magnetic force to approach the movable part, comprising the movable contact 24, the operating rod 20 and the movable core 18, when the contactor closes and prevents this movable part from rebounding by its elastic deformation when it reaches the stop.This magnetic force must not, however, be too strong so as not to disturb the dynamics during opening and it is calibrated to be less than the force exerted by the contact pressure spring 28 which allows the moving contacts 24A to be detached from their closed positions. It is in any case absorbed by the motor because the forces required are not in its critical zone of use.

[0027] Figure 1A details more precisely the magnetic effect holding member which is formed of a fixed part comprising two magnets 42, four plates 44 framing a magnet two by two, a lower stop 46 and an upper stop 48 to limit between them the position of the plates and a movable part comprising a magnetic return 50 secured to the operating rod 20 via a plate 52 and fixing screws 54 passing through this plate and the magnetic return. The direction of magnetization of each of the two magnets which makes it possible to have a force in the direction of movement of the operating rod 20 is illustrated by the magnetic field loop 56. The magnetic return and the plates are advantageously made of pure iron or low-alloy steel.

[0028] As illustrated, in the rest position of the power contactor, that is to say with the movable contacts 24A in contact with the fixed contacts 26A, the four fixed plates 44 are in contact with the movable magnetic return 50 which is pressed against them under the effect of the attraction of the two magnets 42.

[0029] When the power contactor is opened, the actuator 12, which has a magnetic force that is largely sufficient to counter the magnetic forces generated by the two magnets 42, will cause, in the direction of the yoke 16, the movement of the operating rod 20 and, with it, that of the magnetic return 50 with which it is integral, detaching the latter from the plates 44. When the power contactor is closed (and therefore its return to the rest position by deactivation of the linear actuator 12), the magnetic forces of the magnets 42 will counter any mechanical rebounds transmitted by the contact pressure spring 28 and the core return spring 30 to the operating rod 20 and thus prevent any recoil force.

[0030] Depending on the tolerances of the parts making up the power contactor, a greater or lesser clearance may exist between the plates 44 and the magnetic return 50, and this clearance, called an air gap, influences the magnetic forces. However, with the invention, it is preferable to have a force that is always constant.

[0031] Figure 2 illustrates the clearance compensation device then put in place to allow possible correction in the position of the pads.

[0032] Ja represents the possible mechanical play between the plates 44 and the magnetic return 50. The plates 44 can be positioned between the lower stop 46 and the upper stop 48 following a maximum travel Jb. By choosing Jb greater than Ja, the device allows compensation for mechanical play without deteriorating its magnetic performance.

[0033] It will be noted that if the preceding figures essentially show a single-pole contactor, the person skilled in the art will be perfectly capable of substituting a multi-pole contactor, for example bipolar or tripolar, without demonstrating inventive activity. In these multi-pole configurations, a single magnetic effect holding member can be used which holds the moving masses of all the poles or else a magnetic effect holding member per pole. The principle of the invention remains the same and is always to counter the recoil forces caused by the rebounds of these moving masses.

Claims

Claims

1. Power contactor comprising a fixed part and a part movable in translation relative to the fixed part under the activation of a linear actuator (12) and in a direction of movement, between a contact position and a cut-off position, the contact position forming a normally closed rest position of the contactor, the movement of the movable part carrying a movable contact (24) to separate it from a fixed contact (26) facing it in a cut-off chamber (22), by crushing a contact pressure spring (28) and a core return spring (30), characterized in that, to prevent any rebound of the movable part when the linear actuator returns to its rest position, a magnetic effect holding member (40) fixes said movable part in the contact position before it rebounds due to the springs,and characterized in that the magnetic effect holding member (40) comprises two magnets (42) each framed by two plates (44) and a magnetic return (50), the magnetic return being integral with the moving part and the direction of magnetization of each of the two magnets is configured to each exert a magnetic force in the direction of movement.,

2. A power contactor according to claim 1, wherein the magnetic effect holding member (40) is mounted outside the breaking chamber (22).

3. A power contactor according to claim 2, wherein the plates (44) and the magnetic return (50) are made of pure iron or low alloy steel.

4. Power contactor according to one of claims 2 or 3, in which the magnetic force exerted jointly by the two magnets (42) is less than 5 Newton.

5. A power contactor according to any one of claims 2 to 4, wherein the plates (44) are positioned between a low stop (46) and a high stop (48) with a maximum travel Jb, Jb being greater than a mechanical clearance Ja existing between the plates (44) and the magnetic return (50).

6. A power contactor according to any one of claims 1 to 5, wherein the contactor is multi-pole, typically bipolar or tripolar.

7. Power contactor according to claim 6, in which a single magnetic effect holding member retains the movable part of the set of poles.

8. Power contactor according to claim 6, comprising a magnetic effect holding member per pole.

9. Use of a power contactor according to any one of claims 1 to 8 to ensure the cutting of an aeronautical electrical circuit.

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