EP0693765B1 - Electromagnetic actuator for a low tension circuit breaker - Google Patents

Abstract

The circuit breaker electromagnetic propellant mechanism includes an electromagnetic body (7) and a paddle mounted to pivot about a hinge (21). There is a fixed contact (3) and a mobile contact support arm (5) mounted pivotally about a hinge (22). A hammer (9) is formed by an elongated piece inserted between the paddle (8) and the mobile contact support arm. The hinge (21) of the paddle (8) and the hinge (22) of the mobile contact arm (5) are situated on the same side w.r.t. the electromagnetic body (7). The hammer (9) is connected to the paddle (8) at an intermediate point between the hinge (21) of the paddle and the end region of the paddle, at a level which may be magnetically attracted to the electromagnetic body (7). <IMAGE>

Description

The present invention relates generally to a propellant electromagnetic low voltage circuit breaker.

In low voltage circuit breakers (e.g. mains voltage 220 V and 50 Hz) designed to pass a relatively intense current (for example example a nominal current of 125 A), it has been observed for a very long time that there was a problem with the difficulty in getting the contacts off the ground reliably when the circuit breaker trips.

The circuit breaker trips automatically, separating a movable contact from a fixed contact when the intensity of the current that crosses the circuit breaker exceeds a predetermined threshold value.

(a) Le déclenchement doit s'effectuer toutes les fois où l'intensité dépasse la valeur de seuil.

(b) Le déclenchement doit s'effectuer toujours très rapidement après que l'intensité a dépassé la valeur de seuil,

(c) Le déclenchement doit s'effectuer indépendamment de l'intensité du courant de défaut, après dépassement dudit seuil.

The reliability of tripping of the circuit breaker is generally assessed as follows.

(a) The trigger must be made whenever the intensity exceeds the threshold value.

(b) The triggering must always take place very quickly after the intensity has exceeded the threshold value,

(c) Tripping must be carried out independently of the intensity of the fault current, after the said threshold has been exceeded.

A well known phenomenon which is likely to affect the reliability of the tripping of the circuit breaker lies in the fact that various phenomena physical or chemical can occur at the point of contact between the mobile electrical contact and the fixed electrical contact and can cause "bonding" effect of electrical contacts.

To increase the reliability of tripping of the circuit breaker, it has been long proposed to arrange a propellant in the circuit breaker electromagnetic. There are a large number of electromagnetic thrusters for low voltage and high current circuit breakers. Such a propellant electromagnetic is for example described in patent DE-A-942,455 or the Patent EPA-0 410 257.

un corps électromagnétique incluant un noyau entouré par une bobine et deux flancs parallèles conduisant le flux magnétique et présentant chacun des première et deuxième extrémités opposées;

une palette montée de façon pivotante afin de pouvoir prendre une position de repos dans laquelle elle est écartée par rapport auxdites premières extrémités des deux flancs et une position d'actionnement dans laquelle elle est attirée magnétiquement jusqu'à venir en contact avec lesdites premières extrémités des deux flancs;

un contact fixe situé dans ou au voisinage d'un entrefer formé entre lesdites secondes extrémités des deux flancs ;

un bras de support de contact mobile monté de façon pivotante afin de se déplacer dans l'entrefer en déplaçant le contact mobile lié à lui entre ladite position de repos dans laquelle le contact mobile est en contact avec le contact fixe, et ladite position d'actionnement dans laquelle le contact mobile est écarté du contact fixe ; et

un percuteur constitué par une pièce allongée interposée entre la palette et le bras de support de contact mobile.

Such a known electromagnetic propellant comprises:

an electromagnetic body including a core surrounded by a coil and two parallel flanks conducting the magnetic flux and each having first and second opposite ends;

a pallet pivotally mounted so as to be able to assume a rest position in which it is spaced relative to said first ends of the two sides and an actuating position in which it is magnetically attracted until it comes into contact with said first ends of the two sides;

a fixed contact located in or in the vicinity of an air gap formed between said second ends of the two sides;

a movable contact support arm pivotally mounted in order to move in the air gap by moving the movable contact linked to it between said rest position in which the movable contact is in contact with the fixed contact, and said position of actuation in which the movable contact is moved away from the fixed contact; and

a striker consisting of an elongated piece interposed between the pallet and the mobile contact support arm.

More specifically, in document DE-A-942 455, as is shown here in Figures 1A and 1B which schematically illustrate the art anterior, we see that the pallet (v) includes a central zone in which produces the effect of electromagnetic attraction, one end at which is arranged a joint (w) used to rotate the pallet and a another opposite end at which a striker (f) is fixed. An arm of movable contact (d) is arranged in a substantially parallel manner and it comprises at one end a joint (p) and in the vicinity of its other end opposite a movable contact. If we consider a median plane longitudinal (25) passing through the electromagnetic body (e), we see that the joint (p) is located opposite the joint (w) with respect to this plane longitudinal median (25). In addition, the free end of the striker (f) is intended to come into contact with a central zone of the movable contact arm (d), that is, the striker (f) pushes the movable contact arm (d) in one point located between the joint (p) and the movable contact. In addition, the striker (f) is located opposite the joint (w) relative to this median plane longitudinal (25).

It follows from this that the displacement of the striker (f) is greater than the displacement of the central area of the pallet (v) at which the effect of electromagnetic attraction takes place. The palette (v) therefore constitutes a lever arm which amplifies the movement at the striker (f). Through therefore, the force at the striker (f) is less than the force electromagnetic attraction at the central area of the pallet (v). In in addition, the striker (f) pushes the movable contact arm (v) in a zone central, which makes the displacement at the movable contact more greater than the movement of the striker (f) due to the fact that the movable contact arm (d) behaves like a lever arm which amplifies the movement of the striker (f). It results from these two combined lever arm phenomena motion amplifier at the level of the pallet (v) and at the level of the arm of mobile contact (d) only a very small displacement at the level of the area of attraction movement of the pallet (v) produces relatively displacement important in terms of mobile contact. Of course, there is also a reduction of the release force at the movable contact which is in the same report as the amplification report of the movement.

Such an arrangement does not in practice make it possible to obtain a reliable tripping of the circuit breaker since the release force is not sufficient at the level of the mobile contact during the action of trigger. In addition, due to this amplification of the movement, for obtain a sufficient release force from the movable contact, it is necessary that the attraction force of the pallet (v) is relatively large. To get a relatively large attraction force of the palette, it is necessary either to increase the intensity of the magnetic flux is to decrease the distance separating the pallet (v) from electromagnetic body (e). The manufacture of such a propellant electromagnetic is complicated, and has a large footprint incompatible with the volume of the circuit breaker box.

An object of the present invention is to provide a propellant electromagnetic for a low voltage circuit breaker with greater reliability of the operation of its trigger.

Another object of the present invention is to provide such a electromagnetic thruster providing greater threshold accuracy intensity of electric current which causes its triggering.

Another object of the present invention is to provide such a electromagnetic propellant which can be arranged in a more compact manner.

According to a characteristic of the invention, a propellant is proposed electromagnetic for low voltage circuit breaker, this thruster electromagnetic comprising: an electromagnetic body including a core surrounded by a coil and two parallel sides leading the magnetic flux and each having first and second opposite ends; a pallet pivotally mounted around a joint so that it can take a rest position in which it is moved away from said first ends of the two sides and an actuation position in which it is magnetically attracted until it comes into contact with said first ends of the two sides; a fixed contact located in or near a air gap formed between said second ends of the two sides; an arm of movable contact support pivotally mounted around a joint in order to move in the air gap by moving the mobile contact linked to it between said rest position in which the movable contact is in contact with the fixed contact and said actuating position in which the movable contact is removed from the fixed contact; and a striker consisting of an elongated piece interposed between the pallet and the movable contact support arm; in which the pallet joint and the movable contact arm joint are located on the same side with respect to the electromagnetic body and in which the striker is connected to the pallet at a connection point located in an area intermediate between the pallet joint and an opposite end zone from the pallet at which it is magnetically attractive towards said first ends of the two sides.

According to a particular embodiment of the invention, the striker is arranged so that its longitudinal direction makes an angle of 90 ° ± 30 ° with the longitudinal direction of the pallet and also makes an angle of 90 ° ± 30 ° with the longitudinal direction of the movable contact arm.

les figures 1A et 1B sont des mêmes vues schématiques d'un propulseur électromagnétique de disjoncteur basse tension de l'art antérieur tel qu'il a été décrit et commenté précédemment, la figure 1A représentant le dispositif dans une position de repos et la figure 1B représentant le même dispositif dans une position d'actionnement;

les figures 2A et 2B sont des mêmes vues schématiques d'un percuteur électromagnétique de disjoncteur basse tension selon la présente invention, la figure 2A représentant le dispositif dans une position de repos et la figure 2B représentant le dispositif dans une position d'actionnement;

la figure 3 est une vue de côté simplifiée d'un mode de réalisation particulier d'un propulseur électromagnétique selon la présente invention et du disjoncteur basse tension dans lequel il est monté, certaines parties ayant été ôtées par souci de clarté ;

la figure 4 est une vue en perspective des pièces essentielles du propulseur électromagnétique représenté sur la figure 3 ;

la figure 5 est une vue de côté du propulseur électromagnétique de la figure 4 ; et

la figure 6 est une vue de dessus du propulseur électromagnétique de la figure 4.

These objects, characteristics and advantages, as well as others of the present invention will be better understood during the detailed description of an exemplary embodiment which will follow, illustrated by the appended figures among which:

FIGS. 1A and 1B are the same schematic views of an electromagnetic low voltage circuit breaker thruster of the prior art as it has been described and commented on previously, FIG. 1A representing the device in a rest position and FIG. 1B representing the same device in an actuating position;

FIGS. 2A and 2B are the same schematic views of an electromagnetic striker of a low-voltage circuit breaker according to the present invention, FIG. 2A representing the device in a rest position and FIG. 2B representing the device in an actuating position;

FIG. 3 is a simplified side view of a particular embodiment of an electromagnetic thruster according to the present invention and of the low-voltage circuit breaker in which it is mounted, certain parts having been removed for the sake of clarity;

Figure 4 is a perspective view of the essential parts of the electromagnetic propellant shown in Figure 3;

Figure 5 is a side view of the electromagnetic thruster of Figure 4; and

FIG. 6 is a top view of the electromagnetic thruster of FIG. 4.

Referring to FIG. 3, a particular embodiment of a electromagnetic low voltage circuit breaker booster according to the invention is represented. The circuit breaker 1 comprises a box 2 which contains a fixed contact 3, a movable contact 4 which is mounted at the end of a movable contact arm 5, a switching chamber 6 and various elements of electrical connections (not shown) for connecting the fixed and mobile contacts to terminals (not represented). All these elements are well known in the prior art and do not no further description is required here. The object of the present invention relates more particularly to the circuit breaker sub-assembly which constitutes this commonly known as an "electromagnetic propellant". The electromagnetic propellant is used to cause tripping of the circuit breaker, i.e. the opening of the electrical contact when the current intensity electric exceeds a predetermined threshold. The electromagnetic propellant is used to provoke this trigger in a brutal way, that is to say very fast separation of fixed and mobile contacts 3, 4.

The electromagnetic propellant according to the present invention consists of essentially by an electromagnetic body 7, a pallet 8 mounted so swivel, and a striker 9.

If we refer in particular to Figures 4, 5 and 6, we see that the body electromagnetic 7 generally includes a core 10 of cylindrical shape surrounded by a coil (not shown) or at least one turn, and two sides 11, 12 which are arranged parallel to each other, which extend perpendicular to the longitudinal axis of the core 10 and which are arranged substantially respectively at one and the other of the ends of the core 10. The sidewall 11 has a first end 13 directed towards the pallet 8 and a second opposite end 14 and in the same way the side 12 has a first end 15 directed towards the pallet 8 and a second opposite end 16. The first ends 13 and 15 form flat faces which are coplanar and which are directed towards the pallet 8. The second ends 14 and 16 form flat faces which face each other while being separated one on the other from a certain distance in order to constitute an air gap between them 17. The pallet 8 has a flat face 18 which faces the ends 13 and 15 of the electromagnetic body 7.

When the electromagnetic thruster is at rest, the vane 8 is located at a certain distance from the electromagnetic body 7, that is to say that its face 18 is located at a certain distance from the faces of the ends 13 and 15 thereby thereby forming a gap 19 and a gap 20 respectively. When an electric current flows in the coil (not shown) which surrounds the central part of the core 10, a first magnetic flux is established in closed loop by successively crossing the core 10, a side portion 11, the air gap 19, the pallet 8, the air gap 20 and part of the sidewall 12. So simultaneous, a second magnetic flux is established by crossing successively the core 10, the other part of the sidewall 11, the air gap 17 and the other part of the sidewall 12.

The pallet 8 is mounted in an oscillating manner thanks to a hinge 21 and the movable contact arm 5 is also mounted in an oscillating manner thanks to a articulation 22. As can be seen in particular in FIGS. 3 and 5, the fixed contact 3 is mounted in the air gap 17 or close to it and at least part of the movable contact arm 5 extends through the air gap 17. The striker 9 is in the form of an elongated part, one end of which is connected via a hinge 23 to the pallet 8 and the other of which free end 24 is located near the movable contact arm 5.

The electromagnetic striker according to the present invention as described previously in relation to FIGS. 3 to 6 operates in a manner which will be explained now with reference to Figures 2A and 2B. On the face 2A, we can schematically distinguish the same essential elements as those which have been described previously. For this reason, the same indexes of references were used in Figures 2A and 2B compared to Figures 3 to 6 of the particular embodiment, this in order to facilitate the understanding of the operation of the device. In FIG. 2A, there is shown by a line in mixed lines 25 the trace of a longitudinal median plane of the body electromagnetic 7. This median plane 25 is oriented so as to correspond to a plan including the loops of the magnetic fluxes which have been described previously. (We have carried over in the same way the same median plane 25 on the FIGS. 1A and 1B which represent the prior art and which have been described previously). In FIG. 2A, it can be seen that the articulation 21 of the pallet 8 is located at a certain distance from the plane 25 and that the articulation 22 of the arm of movable contact 5 is located at another distance from the plane 25 but on the same side than that of articulation 21 with respect to this plane 25. We can also say that the articulation 21 of the pallet 8 and the articulation 22 of the movable contact arm 5 are located on the same side with respect to the electromagnetic body 7. We see also that the surface 18 of the pallet 8 which faces the surfaces 13 and 15 of the ends of the sides 11 and 12 of the electromagnetic body 7 is a surface which is located in an end zone 26 of the pallet 8. Furthermore, it can be seen that the joint 23 which connects the striker 9 to the pallet 8 is located in an area center of the pallet 8, that is to say is located between the end zone 26 and the joint 21. On the other hand, it can be seen that the free end 24 of the striker 9 is located near the movable contact arm 5 so as to come to rest against this movable contact arm 5 at a contact point 27 located in an area center of the movable contact arm 5, i.e. in an area between a free end 28 of the movable contact arm 5 which supports the movable contact 4 and the articulation 22 of the movable contact arm 5. In addition, the striker 9 is arranged so that its longitudinal direction is substantially perpendicular to the longitudinal direction of the pallet 8 and also substantially perpendicular to the longitudinal direction of the contact arm mobile 5. The expression "substantially perpendicular" is used here to designate an angle between 60 and 120 °, that is to say an angle of 90 ° ± 30 °. To summarize, we can also say that the general form as seen laterally of the assembly constituted by the pallet 8, the striker 9 and the arm of mobile contact 5 is a shape that resembles that of an H.

When a current flowing in the coil which surrounds the core 10 is below a predetermined threshold value, the electromagnetic striker remains in a rest condition as shown in Figure 2A, that is to say a condition in which the pallet 8 is moved away from the body electromagnetic 7 and in which simultaneously the movable contact arm 5 is brought closer to the electromagnetic body 7 so that the movable contact 4 is in contact with the fixed contact 3. Of course, as is already known, there is generally provided an elastic means (not shown) which pushes in permanently the pallet 8 in a direction which moves the end part 26 away from the pallet 8 of the electromagnetic body 7, that is to say in a direction which moves the face 18 of faces 13 and 15 to delimit said air gap 19, 20.

If the electric current exceeds the predetermined threshold value, the force of attraction which is exerted between the pallet 8 and the electromagnetic body 7 exceeds the elastic pushing force of the elastic means and as a result that the pallet 8 suddenly approaches the electromagnetic body 7 and this pivoting movement causes the striker 9 to move, the end 24 comes to rest on the movable contact arm 5, then pushes this movable contact arm 5 so as to rotate it to bring it into a condition in which the movable contact 4 is moved away from the fixed contact 3. The electromagnetic striker is then brought into a condition of trigger as shown in Figure 2B. In the rest condition shown in Figure 2A, we see that there is a slight space between the end 24 of the striker 9 and the contact area 27 of the movable contact arm 5.

The fact that the striker 9 is connected to the pallet 8 at an area central of the pallet 8 has the consequence that its movement is reduced by relative to the movement of the end zone 26 of the pallet 8, by an effect well known lever arm, which results in the thrust force produced at level of striker 9 is greater than the force of attraction which is established at the level of the end zone 26 of the pallet 8 in the same ratio as the lever arm ratio. Such an architecture makes it possible to obtain a good compromise between the speed of movement of the movable contact 4 during the action trigger, and the driving force of the striker 9.

Claims (3)

1. An electromagnetic propeller for a low voltage circuit breaker, comprising:

   an electromagnetic body (7) including a core (10) surrounded by an excitation coil and two parallel flanks (11, 12) conducting the magnetic flux and each presenting opposite first (13, 15) and second (14, 16) ends ;

   a blade (8) pivotally mounted around an articulation (21) able to occupy a rest position in which it is separated from said first ends of the two flanks and an actuation position in which it is magnetically attracted into contact with said first ends of the two flanks ;

   a stationary contact (3) situated in or near to an air-gap formed between said second ends (14, 16) of the two flanks (11, 12);

   a movable contact support arm (5) pivotally mounted around an articulation (22) so as to move in the air-gap moving the movable contact (4) joined thereto between said rest position in which the movable contact (4) is in contact with the stationary contact (3) and said actuation position in which the movable contact is separated from the stationary contact; and a striker (9) formed by an elongate part interposed between the blade (8) and the movable contact support arm (5),

      characterized in that the articulation (21) of the blade (8) and the articulation (22) of the movable contact arm (5) are located on the same side with respect to the electromagnetic body (7) and that the striker (9) is joined to the blade (8) at a connecting point (23) situated in an intermediate zone between the articulation (21) of the blade (8) and an opposite end zone (26) of the blade (8) at the level of which it is magnetically attractable towards said first ends (13, 15) of the two flanks.
2. The electromagnetic propeller for a low voltage circuit breaker according to claim 1, characterized in that the striker (9) is arranged in such a way that its longitudinal direction makes an angle of 90° ± 30° with the longitudinal direction of the blade (8) and also makes an angle of 90° ± 30° with the longitudinal direction of the movable contact arm (5).
3. The propeller according to claim 3, characterized in that the rotation axes of the blade (8) and of the movable contact (5) are located appreciably on the same perpendicular with respect to their respective planes.

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