Normally closed power contactor

Abstract

Normally Closed Power Contactor. A power contactor comprising a fixed part and a moving part that translates relative to the fixed part under the activation of a linear actuator (12) and along a direction of movement, between a contact position and a breaking position, the contact position forming a normally closed rest position of the contactor, the movement of the moving part carrying a moving contact (24) to separate it from a fixed contact (26) facing it in a breaking chamber (22), by compressing a contact pressure spring (28) and a core return spring (30), characterized in that, to prevent any rebound of the moving part during the return of the linear actuator to its rest position, a magnetic retaining element fixes this moving part in the contact position before it rebounds due to the springs. Figure for the abbreviation: Fig. 1.

Description

Title of the invention: Normally closed power contactor technical field

[0001] The present invention relates to the field of power switching components and more particularly to a normally closed electromechanical spring-loaded power contactor. Previous technique

[0002] 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 moving 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 moving and fixed contacts are in mechanical contact (this is referred to as a "normally closed" contactor in which an electric current can flow between the closed power contacts when the actuator is not activated) to a breaking position (after a stroke of <3 mm), in which the moving contacts separate from the fixed contacts, preventing the flow of current, is effected by the electrical supply of a coil.The coil returns a movable core carrying the operating rod towards a breech and against both a contact pressure spring acting on the movable contacts and a core return spring mounted between the armature and the core attached to a flux return breech receiving the coil.

[0003] 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. Due to this deactivation, the core is subjected to an impact with the fixed contacts and then to oscillations related to the damping coefficient of this spring, causing the moving contacts to rebound and significantly reducing the contactor's performance, possibly even leading to the contacts sticking together and rendering the contactor inoperative.

[0004] A common solution to avoid these rebounds is to increase the stiffness of the springs, and in particular the core return spring. However, while this solution may seem simple to implement, it requires a much more powerful, and therefore larger and heavier, actuator, which is unacceptable for use in aeronautical electrical circuits. Description of the invention

[0005] The main objective of the present invention is therefore to provide a power contactor that eliminates the usual rebound upon returning to its initial rest state and thus improves its closing capacity (maximum current at which the contacts can close without welding). Another objective is to achieve this result without modifying the actuator, the breaking chamber, or the mechanical properties of the contactor, and in particular those of its springs.

[0006] These goals are achieved by a power contactor comprising a fixed part and a moving part in translation relative to the fixed part under the activation of a linear actuator and along a direction of movement, between a contact position and a breaking position, the contact position forming a normally closed rest position of the contactor, the movement of the moving part carrying a moving contact to separate it from a fixed contact facing it in a breaking chamber, by compressing a contact pressure spring and a core return spring, characterized in that, to avoid any rebound of the moving part during the return of the linear actuator to its rest position, a magnetic retaining element fixes this moving part in the contact position before it rebounds due to the springs.

[0007] Thus, the addition of magnetic retention prevents sticking between contacts and increases the breaking capacity under short-circuit current. Bouncing is eliminated without altering the elastic properties of the springs in place.

[0008] Preferably, the magnetic retaining element is mounted outside the cutting chamber.

[0009] Advantageously, the magnetic holding element 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.

[0010] Preferably, the plates and the magnetic return are made of pure iron or low alloy steel.

[0011] Advantageously, the magnetic force exerted jointly by the two magnets is less than 5 Newtons.

[0012] Preferably, the pads are positioned between a lower stop and an upper stop with a maximum travel Jb, Jb being greater than a mechanical play Ja existing between the pads and the magnetic return.

[0013] Depending on the envisaged embodiment, the contactor can be multi-pole, typically bipolar or tripolar, then either a single magnetic holding element retains the moving part of all the poles or the power contactor includes a magnetic holding element per pole. Brief description of the drawings

[0014] Other features and advantages of the present invention will become apparent from the description given below, with reference to the accompanying drawings which illustrate an example of an embodiment without being limiting in any way and on which:

[0015] [Fig-1] [Fig.1] illustrates a power contactor according to the invention,

[0016] [Fig.1A] [Fig.1A] details the magnetic retaining element of the contactor of [Fig.1], and

[0017] [Fig.2] [Fig.2] is a side view of the magnetic retaining element of the [Fig.2] setting the game compensation mechanism. Description of the implementation methods

[0018] As explained in the preamble, in a normally closed spring-loaded power contactor, rebound upon closing is a recurring problem. The principle of the invention is based on the addition of a magnetic retaining element that eliminates this rebound without altering the mechanical properties of the contactor. This element holds the moving masses in the closed position before they can rebound due to the springs. More precisely, the magnetic retaining element prevents the moving part of the contactor from rebounding and, consequently, the unwanted transmission of rebound to the moving contact.

[0019] The mechanical properties of the contactor are not impacted because neither the breaking chamber nor the contactor actuator, which constitute its critical elements, are modified.

[0020] Fig. 1 illustrates a normally closed power contactor in the rest position according to the invention.

[0021] Such a power contactor 10 conventionally comprises a fixed part and a moving part that translates relative to the fixed part under the action of a linear actuator 12 and along a direction of movement, between a contact position and a breaking 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 a movable core 18 protruding from the body at its other end is guided. The movable core carries at its end an operating rod 20 that penetrates a breaking chamber 22 closed by a cover 22A. A movable contact 24 supporting the movable contact pads 24A is mounted on the operating rod.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 cutting chamber. Between the breech 16 and the movable core 18 is mounted a return spring core 30.

[0022] According to the invention, the magnetic retaining element 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 magnetic force sufficient to hold the moving part, comprising the moving contact 24, the operating rod 20, and the moving core 18, against the contactor when it closes, and to prevent this moving part from rebounding due to its elastic deformation when it reaches its stop. This magnetic force must not, however, be too strong so as not to disrupt the dynamics during opening, and it is calibrated to be less than the force exerted by the contact pressure spring 28, which separates the moving contacts 24A from their closed positions. In any case, it is absorbed by the motor because the forces required are not within its critical operating range.

[0023] Figure 1A details more precisely the magnetic retaining element which is consisting of a fixed part comprising two magnets 42, four plates 44 framing a magnet in pairs, a lower stop 46 and an upper stop 48 to limit the relative position of the plates, and a movable part comprising a magnetic return 50 attached 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 allows for a force to be applied 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.

[0024] As illustrated, in the rest position of the power contactor, i.e. with the moving contacts 24A in contact with the fixed contacts 26A, the four fixed plates 44 are in contact with the moving magnetic return 50 which is pressed against them under the effect of the attraction of the two magnets 42.

[0025] When the power contactor is opened, the actuator 12, which has a magnetic force more than sufficient to counter the magnetic forces generated by the two magnets 42, will cause the operating rod 20 to move towards the cylinder head 16, and with it the magnetic return 50 to which it is attached, detaching the latter from the plates 44.

[0026] When the power contactor is closed (and therefore returns to the rest position by deactivating the linear actuator 12), the magnetic forces of the magnets 42 will counteract 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.

[0027] Depending on the tolerances of the components of the power contactor, a greater or lesser degree of play may exist between the plates 44 and the magnetic return 50, and this play, called the air gap, affects the magnetic forces. However, with the invention, it is preferable to have a constantly constant force.

[0028] Fig. 2 illustrates the play compensation device then put in place to allow a possible correction in the position of the plates.

[0029] Ja represents the possible mechanical play between the pads 44 and the magnetic return 50. The pads 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 of mechanical play without degrading magnetic performance.

[0030] It should be noted that while the preceding figures essentially show a single-pole contactor, a person skilled in the art will readily substitute a multi-pole contactor, for example, a bipolar or tripolar one, without having to enter into any inventive step. In these multi-pole configurations, a single magnetic retaining element can be used to hold the moving masses of all the poles, or alternatively, a magnetic retaining element for each pole. The principle of the invention remains the same and is still to counteract the recoil forces caused by the rebound of these moving masses.

Claims

Demands

1. Power contactor comprising a fixed part and a moving part in translation relative to the fixed part under the activation of a linear actuator (12) and along a direction of movement, between a contact position and a breaking position, the contact position forming a normally closed rest position of the contactor, the movement of the moving part carrying a moving contact (24) to separate it from a fixed contact (26) facing it in a breaking chamber (22), by compressing a contact pressure spring (28) and a core return spring (30), characterized in that, to prevent any rebound of the moving part during the return of the linear actuator to its rest position, a magnetic retaining member (40) fixes said moving part in the contact position before it rebounds due to the springs,and characterized in that the magnetic retaining element (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. Power contactor according to claim 1, in which the magnetic holding member (40) is mounted outside the breaking chamber (22).

3. 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 any one of claims 2 or 3, wherein the magnetic force exerted jointly by the two magnets (42) is less than 5 Newtons.

5. Power contactor according to any one of claims 2 to 4, wherein the pads (44) are positioned between a lower stop (46) and an upper stop (48) with a maximum travel Jb, Jb being greater than a mechanical clearance Ja existing between the pads (44) and the magnetic return (50).

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

7.

8.

9. Power contactor according to claim 6, in which a single magnetic retaining element retains the moving part of the set of poles. Power contactor according to claim 6, comprising a magnetic holding element per pole. Use of a power contactor according to any one of claims 1 to 8 to ensure the breaking of an aeronautical electrical circuit.

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