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 concerns a normally closed spring electromechanical power contactor. Prior art

[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 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 (here we are talking 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.

[0003] When the power supply to the actuator 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 rebounds of the moving contacts and significantly reducing the performance of the contactor, possibly leading to the contacts sticking together, 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, this solution, although it seems simple to implement, requires having a much more powerful and therefore larger and heavier actuator, which is not acceptable for use in aeronautical electrical circuits. Statement of the invention

[0005] The main aim of the present invention is therefore to propose a contactor of power that can overcome the usual rebounds 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 its springs.

[0006] 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.

[0007] 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.

[0008] Preferably, the magnetic effect holding member is mounted outside the cutting chamber.

[0009] 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.

[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 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.

[0013] 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. Brief description of the drawings

[0014] 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:

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

[0016] [Fig.lA] [Fig.lA] details the magnetic effect holding member of the contactor of [Fig.l], and

[0017] [Fig.2] [Fig.2] is a side view of the magnetic effect holding member of the [Fig.2] mounting the clearance compensation device. Description of the embodiments

[0018] 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.

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

[0020] [Fig.l] 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 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 cutting 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 yoke 16 and the . movable core 18 is mounted a return spring core 30.

[0022] 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 moving part, comprising the moving contact 24, the operating rod 20 and the moving core 18, when the contactor closes and to prevent this moving part from rebounding by its elastic deformation when it reaches the stop. This magnetic force must however not 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 makes it possible to detach the moving contacts 24A 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.

[0023] [Fig. 1 A] 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 the position of the plates between them and a mobile 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 allows 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.

[0024] 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.

[0025] 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.

[0026] When the power contactor closes (and therefore returns it to the rest position by deactivating 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.

[0027] Depending on the tolerances of the parts making up the power contactor, a more or less significant clearance may exist between the plates 44 and the magnetic return 50, and this clearance, called the air gap, influences the magnetic forces. However, with the invention, it is better to have a constant effort always.

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

[0029] 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.

[0030] It will be noted that if the preceding figures essentially show a single-pole contactor, a 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.

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

3. Power contactor according to claim 1 or claim 2, in which 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.

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

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

6. Power contactor according to any one of claims 3 to 5, in which 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).

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

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

9. Power contactor according to claim 7, comprising a magnetic effect holding member per pole.

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

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