EP0080939B1 - Contactor with self-protection means against the repulsive forces between the contacts and his application in a current limiting circuit breaker - Google Patents

Abstract

A contactor capable of having a very high breaking power comprises a movable contact carrier bridge (3) having a central part in the form of a blade (3c) and conducting J-shaped pieces (2a-2b) supporting fixed contacts. A non-magnetic blade bent in the form of a U is mounted slidable inside a hollow movable insulating contact holder (1) and guides and holds at its upper end a magnetic plate (8) cooperating with said blade (3c) and forming an air-gap with another U-shaped magnetic piece (6), disposed between the legs of the bent blade (5) and integral (at 7) with the contact holder (1). A contact pressure spring (4) bears on the basis of the U-shaped magnetic piece (6) and on the bottom of the bent blade (5).

Description

The invention relates to the protection of contactors against the effects of contact separation due to repulsion forces between them.

A contactor is normally provided to support effective currents of the order of 12 In (or 6 In, depending on the ratings), In being the nominal current. Beyond this value, there is a risk of soldering and, at least, of contact wear, caused by various effects which will be analyzed below.

It is known, in particular from patents US-A-3123 691 and FR-A-1 514 069, to associate with a contactor a device for cutting or limiting and interrupting the current flowing in the main contact of the contactor, unit which intervenes only in the event of a short-circuit or significant overload and causes a limitation and a rapid interruption of said current, before the contactor has in principle had the time to suffer damage.

Overloading can occur either when the contactor is closed or during its closing. If it corresponds to currents which would exceed, in the absence of rapid protection means, for example 100 ln, the action of the switch member is very rapid, that is to say that the current which flows in the main contactor of the contactor reaches for example 40 to 50 In peak, then drops back to the value 0, in a time, of the order of 2 ms for example, much less than the duration of a half-cycle of the sector.

However, there are repulsive forces between the contacts. These forces exist, in particular, in contactors comprising fixed contact-carrying conductors folded back in J, as a result of the passage of currents of opposite direction in one of the two branches of J and in the movable contact bridge. Even in contactors having rectilinear fixed contact-carrying conductors, the contact between the fixed and mobile contact pads being effected according to a "spot" of very small diameter through which the current lines pass, these are bent , hence the existence of a repulsion force varying in inverse ratio to the diameter of the contact spot and proportional to the square of the current.

Ultimately, these repulsion forces, as soon as the current reaches a sufficient intensity, overcome the action of the spring of the contactor ensuring the contact pressure, so that the contacts will separate.

When, for very large overloads as specified above, the current very quickly reaches 20 or 30 In, this results in a large repulsion force which is sufficient for the movable contact to be moved away from a relatively large distance from the fixed contact. Given the inertness of the device, the movable contact does not fall back until well after the power has been cut and the risks of welding are very reduced. This alternation of separation and reclosing of the contacts on each overload however results in abnormal wear.

On the other hand, if the overload corresponds to effective currents reaching for example only 15 In, for these intensities, the switch member does not exert any action of significant limitation of the current during half-wave and, consequently, a current greater than 6 ln or 12 In can pass through the contactor. The repulsive forces then manifest themselves in the vicinity of the crest of the current and, as they are much weaker than in the previous case, when they cease, the contact closes again on a still large current. This results in a significant risk of welding. Ultimately, in the combination of a contactor with a device for cutting and limiting overload currents, such as circuit breaker-limiter and even conventional circuit breaker (for overloads not exceeding 50 or 60 In) and fuse, there exists a zone of intensity of the overload current in which a risk of soldering of the contacts of the contactor is added to the other risks of destruction of the device and the inevitable wear of the contacts. It will be noted that, when the overload occurs when the contactor closes, after a time interval during which there is mechanical rebound of the contacts which can themselves cause soldering, an interval which ends with the stabilization of the contacts, is brought back to the case, exposed above, where the overload occurs while the contactor is in the closed state.

The invention proposes to compensate, during the time interval separating the appearance of the overload and the opening of the circuit, the effect of the repulsive forces of electro-dynamic nature which arise between the fixed and mobile contacts d '' a contactor, in order to prevent the contacts from being able to separate inadvertently with the consequences which would ensue (wear, risk of welding) for certain values of the overload current.

It proposes a contactor comprising, in a known manner, in particular by patents US-A-3123691 and FR-A-1 514069, a control electromagnet having a movable part, a contact assembly comprising at least a first part conductive support of at least one movable contact and at least a second piece conductive support of at least one fixed contact, connecting members between the movable part of the electromagnet and the first piece of movable contact support , an elastic member arranged to cooperate with said first movable contact support part in a direction which establishes a certain contact pressure, and means for locally concentrating the flux created by the flow of current in said conductive parts in the vicinity of said first conductive part, to exert on it a force of attraction which tends to cause the closure of the contacts.

According to the invention, this contactor is more particularly characterized in that said means comprise at least one first soft magnetic part rigidly coupled to a contact carrier integral with said movable part of the electromagnet and arranged so that, as soon as appears an overload current reaching the intensity that the standards require of a traditional contactor, that is to say six to fifteen times the nominal current, in said first conductive part said first magnetic part exerts a force of attraction on a part of said first conductive part and / or on a second piece of soft magnetic material integral with said first conductive piece or in direct support on said first conductive piece and subjected to the action of a contact pressure spring, said anchoring force being sufficient to counteract the effect of the repulsive forces which are then exerted between the fixed and mobile contacts, while the tensile force developed between the fixed part and the mobile part of the electromagnet is expected to be sufficient, on the one hand, to withstand the additional tensile force exerted on its movable part when said attraction force is exerted, without detachment of said movable part from said fixed part and, on the other hand, so that, added to said attraction force, it counteracts the effect of said repulsion forces when said overheating occurs before the contactor closes.

It should be clearly understood that, in normal operation of the contactor at its nominal current, the compensation device does not contribute in a appreciable manner to modifying the contact pressure, which it only effectively reinforces when an overload develops forces. of notable repulsion. The contact pressure is therefore provided, in the traditional way, by a pressure spring associated with the support of the movable contacts of the contactor.

As will be explained below, this compensation for the effect of repulsion forces results in a significant increase in the closing power and the breaking capacity of the contactor.

According to a first embodiment, which will be preferred for contactors of large ratings having fixed contact supports folded in the form of J to improve the blowing of the arcs appearing in normal operation, said first magnetic part has the shape of a U the base of which is rigidly coupled to a contact carrier secured to the movable part of the electromagnet, while the second magnetic part is arranged to form a variable air gap with the upper ends of the branches of the U and that said part of the support conductor of the movable contacts has the form of a blade on which said second part is supported and engaging in the opening of the U by forming a narrow gap.

According to a second embodiment, the magnetic part indirectly coupled to the mobile part of the electromagnet has the shape of a U and said part of the conductive support of the mobile contacts has the shape of a blade which engages in the opening of the U by forming a narrow air gap.

According to a third embodiment, said second magnetic piece is held in abutment, by said contact pressure spring associated with the conductive support of the movable contacts, on said part of said support and forms a variable air gap with said first magnetic piece.

Other features, as well as the advantages of the invention, will become apparent in the light of the description below.

• La figure 1 est une vue en perspective de l'ensemble de contact d'un contacteur à pont de contact double coupure, équipé d'un dispositif magnétique de compensation conforme au premier mode d'exécution de l'invention;
• les figures 2 et 3 représentent le même ensemble, respectivement vu de face et du bout, en position d'ouverture;
• les figures 4 et 5 représentent le même ensemble, respectivement vu de face et de bout, en position de fermeture;
• la figure 6 est une vue en perspective de l'ensemble de contact d'un contacteur à pont de contact double coupure, équipé d'un dispositif magnétique de compensation conforme au second mode d'exécution de l'invention;
• les figures 7 et 8 représentant le même ensemble, respectivement vu de face et de bout, en position d'ouverture;
• les figures 9 et 10 représentent le même ensemble, respectivement vu de face et de bout, en position de fermeture;
• la figure 11 est une vue en perspective de l'ensemble de contact d'un contacteur à pont de contact double coupure, équipé d'un dispositif magnétique de compensation conforme au troisième mode d'exécution de l'invention.
• les figures 12 et 13 représentent le même ensemble, vu de face, respectivement en position d'ouverture et en position de fermeture, et
• la figure 14 représente en coupe une vue schématique des pièces magnétiques et du support de contact mobile; pour le premier mode d'exécution.

In the accompanying drawings:

• Figure 1 is a perspective view of the contact assembly of a contactor with double break contact bridge, equipped with a magnetic compensation device according to the first embodiment of the invention;
• Figures 2 and 3 show the same assembly, respectively seen from the front and from the end, in the open position;
• Figures 4 and 5 show the same assembly, respectively seen from the front and end, in the closed position;
• Figure 6 is a perspective view of the contact assembly of a contactor with double break contact bridge, equipped with a magnetic compensation device according to the second embodiment of the invention;
• Figures 7 and 8 showing the same assembly, respectively seen from the front and end, in the open position;
• Figures 9 and 10 show the same assembly, respectively viewed from the front and end, in the closed position;
• FIG. 11 is a perspective view of the contact assembly of a contactor with a double break contact bridge, equipped with a magnetic compensation device in accordance with the third embodiment of the invention.
• FIGS. 12 and 13 represent the same assembly, seen from the front, respectively in the open position and in the closed position, and
• Figure 14 shows in section a schematic view of the magnetic parts and the movable contact support; for the first mode of execution.

In Figures 1 to 5, there is shown a contact holder comprising an insulating part or contact holder 1 secured to the armature of an electromagnet, not shown, and two fixed contacts 20a-20b carried by conductors folded in "J" 2a-2b cooperating with a movable contact bridge 3 with two branches 3a-3b respectively carrying contact pads 30a-30b, on either side of a vertical blade 3c.

A contact pressure spring 4 is housed in a blade of non-magnetic material folded into a U, the lower part of which is arranged so that it can slide inside the part 1, and the upper part of which leaves the part. 1, is provided in the vicinity of its ends with two windows 50-51.

A U-shaped piece of soft magnetic material 6 is placed between the branches of the blade 5, in their upper part, and fixed at its base to the piece 1 by means of a pin 7.

The central vertical blade 3c which connects the two branches 3a -3b of the bridge 3 engages in the central groove 60 which is provided with the upper face of the part 6 and, as shown in FIGS. 2 and 3, when the contacts are open , the blade 3c, in edge support at the bottom of the groove 60, has its upper part which protrudes slightly from the groove, so that a second parallelepeledepiece 8, made of soft magnetic material, engaged by the projections 80- 81 with which its edges are provided, in the windows 50-51 and on the lower face of which the blade 3c is pressed, leaves a small gap between said lower face and the upper face of the part 6.

The spring 4 is pressed, at one end, against the underside of the part 6 and, at its other end, against the base of the part 5.

When, the armature being attracted, the part 1 is driven downwards (arrow F, FIG. 2), the part 6, secured to the part 1 by the pin 7, moves the same distance a. The spring 4, by pressing the bottom of the blade 5, drives the latter down over a smaller distance b, which corresponds to the distance between the pellets 20a and 30a on the one hand, 20b and 30b on the other hand . Indeed, the blade 5 drives the part 8 and the bridge 3, until the contacts are closed. At this time, the blade 5 can no longer move and, the part 6 continuing to descend, the spring 4 is compressed, thus ensuring a certain contact pressure and sufficient for nominal operation.

When a current flows in the bridge (see figure 14), this current induces a magnetic field in parts 6 and 8, so that a magnetic attraction force is exerted between, on the one hand, part 6 and the part 8. The current which circulates in the central strip 3c, cooperates with a leakage flow 0 which is located between the branches of the part 6 which communicates to this strip forces directed towards the bottom of the groove 60.

The arrangement and dimensioning is such that, for current intensities of the order of the nominal value ln, the vector sum of the attractive forces, and of the opposite electro-dynamic forces developed in the conductors folded in "J" , is practically negligible and the contact pressure is only ensured by the spring.

On the other hand, in the event of overload, from a peak current of a few ln (12 to 15 ln for example), the force of attraction linked to the presence of the magnetic parts 6 and 8 becomes significant and reinforces the effect. spring pressure. Beyond 50 or 60 ln, this attractive force reaches a limit value, the magnetic parts 6 and 8 being saturated, but the complementary forces due to the cooperation of the flux ci> 1 and of this current continue to grow.

Tests have shown that a contactor made with the figured device has an exceptionally large breaking and closing capacity, of the order of 40 to 50 ln, that is to say several times greater than that which would be obtained with the sole contact pressure spring. Thus, the breaking or closing capacity may reach, in the described embodiment, which is particularly suitable for the production of large-caliber contactors, effective values of 10 KA to 15 KA instead of 4 KA for a device with a nominal rating of 300 A. This makes it possible to envisage using such a contactor without associating it with a limiter or a fuse when the properties of the installation which it supplies make it possible to be certain that the short-circuit intensities -circuit will not exceed these values. However, current monitoring means (for example magneto-thermal) must be associated with this installation to control the opening of the contactor - within a rapid period which will guarantee that this installation is not damaged.

It will be noted that there can be no question, in practice, of using a spring ensuring alone, the contact pressure which would correspond to such a breaking or closing power, since the electromagnet should be capable, during closure, to successfully compress such an important spring, which is not economically feasible. In the device described, the electromagnet will only have to compress a normal spring and it is only when the current, once established, reaches a peak value corresponding to a significant overload that the accessory holding device will exert additional pressure on the contacts.

Of course, the part 6 will exert, for a closure on a peak current corresponding to an overload, a reaction on the armature in the form of a tensile force tending to tear the armature from the electromagnet. It is therefore important that measures are taken to prevent the armature from becoming detached from the fixed yoke of the electromagnet. To this end, it is advantageous to supply the electromagnet with rectified current during the holding period: the attraction force then never passing through the zero value, the risk of the armature tearing off is reduced. This measure may or may not be combined with a relatively large dimensioning of the electromagnet. A judicious calculation of the characteristics of the U-shaped part and of the electromagnet is necessary so that the latter has, at the time of closing of the contacts causing the apposition of industrial currents of the order of 12 In, a sufficient kinetic energy to overcome the attractive forces mentioned above and the strength of the various springs.

When the overload of the order of 12 ln occurs before closing, at the time of the call, i.e. when the call force of the armature of the electromagnet is far from d 'Having reached its maximum value, it is important that said calling force, added to the additional attractive force exerted by parts 6 and 8, is sufficient to counteract the forces of electro-dynamic repulsion. For this purpose, it is advantageous to use an electromagnet having a small air gap, or a very high inrush current, as is the case in particular in the contactors marketed by the Applicant under the name of series F. In these contactors, the call is made by alternating current and, thanks to an appropriate electronic circuit, the maintenance is made by rectified alternating current with low ripple of reduced amplitude and well controlled.

The surprising result mentioned above (increase in closing or breaking capacity) is due to the fact that the additional holding force eliminates the harmful effect of repulsion phenomena between the contacts, phenomena which normally become sufficient when the peak current reaches 12 to 15 ln, so that, the contacts slightly apart, there is an arc. A significant risk of soldering the contacts or even exploding the housing can result from the absence of these additional holding forces.

The additional holding force also has the effect of reducing the phenomenon of mechanical rebound of the contacts which manifests itself during closing, and therefore of reducing wear, starting from around 8 ln.

In the embodiment illustrated by Figures 6 to 10, to the insulating part 9 secured to the armature (not shown) of the electromagnet is fixed a piece 10 of soft magnetic material, provided at its base with a double hooking tongue 101 which engages between two suitably profiled projections 90-91 of the internal wall of the part 9.

The part 10 has a U-shaped cross section and the double-cut movable contact bridge 11, which carries the two contact pads 110a-110b, has a central blade 110c, which engages in the U as shown in the figure 8. The fixed contacts 120a and 120b are carried here by rectilinear blades 12a, 12b.

The piece 9 is provided, at its upper end, with a hoop 92 to which is fixed, by hooking complementary profiled parts, a piece of insulating material 13 provided with a central stud 130 by which one end of a spring is guided of pressure 14. The other end of the spring cooperates with a recess 150 which is provided with an insulating part 15 which is supported, by its ends 151-152, on the two respective branches of the movable contact bridge 11.

When, the movable armature of the electromagnet being attracted, the part 9 is driven downwards (arrow F _{1 'in} FIG. 7), the parts 10 and 13 undergo the same movement a, and the spring 14 moves the part 15, therefore the contact bridge 11, of the distance b ₁ <a, which causes the movable contacts to come to bear on the fixed contacts. The part 9 continuing its downward movement over a distance a _i -b _i , while the blade 110c is immobilized, it ceases to be in contact with the bottom of the U (Figures 9 and 10) and the spring 14 is compressed to ensure contact pressure.

When a current flows in the bridge, it induces a magnetic field in the part 10, so that an electromagnetic force is exerted on the blade 110c, in the direction of the increase of the pressure forces of the contacts, whatever either the direction of the current.

This force plays the same role as the attractive force due to the magnetic pieces 6-8 in the embodiment of Figures 1 to 5. It is however less important. To give it a usable value, we will advantageously reduce the air gap between the branches of the U precisely, by giving this central part the shape of a blade placed on edge in a narrow groove of the U.

In the embodiment of Figures 11 to 13, the fixed contacts 12a-120a, 12b-120b are rectilinear as in that of Figures 6 to 10 and the insulating part 9, integral with the armature of the electromagnet, cooperates at its upper part with an insulating part 13 identical to that of FIGS. 6 to 10 and also serving to guide and support one end of the spring 14. The latter bears, at its other end, on an insulating part 16 which itself supports, by its central triangular projecting part 160, on a first blade 17 of soft magnetic material, which in turn presses on a movable contact blade 18, provided with contacts 180a-180b. A second blade 19 made of soft magnetic material is fixed, for example by means of a bolt 190, to the lower part of the part 9.

When the electromagnet is open (Figure 12), the three parts 17-18-19 are in mutual contact, their central parts having shapes such that they fit into each other.

When the electromagnet drives the part 9 in the direction of the arrow F, (figure 12), the part 19 separates from the parts 17-18 and, the part 13 undergoing the same displacement, greater than the distance between the contacts , the spring 14 which pressed the part 18 on the part 19 until the establishment of the contacts, is then compressed by an additional quantity to ensure the contact pressure.

When a current flows in the contact blade 18, the magnetic field which it induces in the parts 17-19 has the effect of developing a force of attraction between them. This force contributes to maintaining the contacts and therefore plays a role analogous to that which has been explained with reference to the previous figures. For example, such a device applied to a contactor with a nominal rating of 12 A can withstand effective currents of 5 KA instead of 1.7 KA in the absence of the magnetic holding pieces.

It will be noted that, in the embodiments of FIGS. 6 to 13, which is particularly suitable for the production of small or medium-sized contactors, the support conductors of the fixed contacts are not folded back and do not exert electrodynamic forces. notable repulsion. However, at the contact spot, as explained above, a necking effect appears which ultimately results in repulsion forces that the additional holding force will overcome, up to a certain threshold. current.

It goes without saying that the forms of contact shown in the various figures are not limiting. In particular, in the case where the contact bridge would be of a nature to establish a capacitive circuit, which would cause, during closing, the creation of transients of frequencies ranging from 500 to 1000 Hz for example, with high peak currents , the solutions described would also make it possible to counteract the effect of these transients.

The device could be applied to seedlings single contact breakers. The shape and arrangement of the magnetic piece or pieces could be subject to variants, as well as those of the contact assembly itself.

For the compensating forces to be significant, it is advantageous that all the air gaps remain relatively weak in the closed position; in the embodiments of FIGS. 6 to 10, the active air gaps are defined by the slot of the U.

In a simplified embodiment of the device described in FIGS. 11 to 13 (where the interlocking of the various parts is obtained by a V shape), parts corresponding to those referenced by 17, 18, 19 could have flat or rectilinear shapes, means not described, but obvious to those skilled in the art, moreover making it possible to ensure lateral support of the contact bridge and of the ferromagnetic parts.

• - soit des moyens de détection de courant (par exemple magnéto-thermiques) aptes à commander l'ouverture du contacteur et un appareil n'effectuant que la limitation,
• - soit un disjoncteur-limiteur dont l'ouverture provoque également la commande d'ouverture du contacteur, peut couper sans dommage ni soudure des courants de court-circuit efficaces présumés de l'ordre de 100 KA, à condition que le disjoncteur ou module limiteur limite les courants de crête à une valeur inférieure à 40-50 In.

An assembly, intended for supplying a load for its protection and for the protection of the lines, and comprising in series a contactor in accordance with the invention and,

• - either current detection means (for example magneto-thermal) capable of controlling the opening of the contactor and an apparatus effecting only the limitation,
• - either a circuit breaker-limiter, the opening of which also causes the contactor to open, can cut presumed effective short-circuit currents of the order of 100 KA without damage or welding, provided that the circuit-breaker or limiter module limits peak currents to a value less than 40-50 In.

Such an arrangement is therefore particularly advantageous due to the fact that it is much easier to manufacture a circuit breaker or a limiting stage, which is able to effectively limit the peak currents mentioned above, while it is very difficult to limit the peak currents of the order of 15 to 20 ln for which the faults of traditional contactors appear precisely.

Claims (11)

1. A contactor comprising a control electromagnet having a movable part, a contact assembly comprising at least a first conducting piece (3, 11, 18) supporting at least one movable contact and at least a second conducting piece (2a, 2b, 12a, 12b) supporting at least one fixed contact, means (1, 5, 9, 13, 14, 15) for connecting the movable part of the electromagnet to the first mobile contact supporting piece, a resilient member (4, 14) adapted to cooperate with said first movable contact supporting piece, in a direction which establishes a certain contact pressure, and means for concentrating locally the flux created by the passage of the current throug h said conducting pieces in the neighbourhood of said first conducting piece, for exerting thereon an attraction force tending to induce the contacts to close themselves, characterized in that said means comprise at least a first soft magnetic piece (6, 10, 19) rigidly coupled to contact holding menas integral with said movable part of the electromagnet and adapted when an overload current appears reaching the intensity which standards require of a traditional contact holder, namely six to fifteen times the rated current in said first conducting piece (3, 11, 18) said first magnetic piece exerts a force of attraction on a part (3c, 110c) of said first conducting piece and/or a second piece made from a soft magnetic material (8,17) integral with said first conducting piece or bearing directly on said first conducting piece and subjected to the action of a contact pressure spring said force of attraction being sufficient to counter the effect of the repulsion forces which are then exerted between the fixed and movable contacts, whereas the developped pulling force between the fixed part and the movable part of the electromagnet is provided sufficient, on the one hand, so as to support the additionnal pulling force exerted on its movable part when said attraction force is exerted without said movable part breaking away from the fixed part of the electromagnet, and on the other hand for, added to the said attraction force, countering the effect of said repulsion forces when said overload occurs before the closure of the contactor.

2. The contactor as claimed in claim 1, characterized in that said electromagnet has a small air gap or is supplied by a very strong pulling current, preferably consisting in a rectified small wave AC Current.

3. The contactor as claimed in claim 1, characterized in that said first magnetic piece (6) has the shape of a U whose base is coupled indirectly to the movable part of the electromagnet, whereas the second magnetic piece (8) is arranged to form a first air gap with the upper ends of the legs of the U and that said part (3c) of the movable contact supporting piece (3) has the form of a blade integral with said second magnetic piece (8) and engaging in the opening of the U while forming a second air gap.

4. The contactor as claimed in claim 3, characterized by two conducting pieces supporting the fixed contact and having a J-shaped profile (2a-2b), by a movable contact bridge (3), and by connection members comprising: an insulating piece (1) rigidly coupled to the movable part of the electromagnet, said first magnetic piece (8) being itself rigidly connected (at 7) to said insulating piece, a spring (4) which forms said resilient contact pressure member and bears, on the one hand, on the lower part of said first magnetic piece (6) and, on the other hand, on the bottom of a blade (5) made from a non-magnetic material bent in a U shape slideably mounted in said insulating piece (1), the second magnetic piece (8) being itself integral with the upper part of said blade (5), between the legs of which said two magnetic pieces (6, 8) are disposed opposite one another.

5. The contactor as claimed in claim 1, characterized in that said first magnetic piece (10) has the shape of a U, whereas said part (11 Oc) of the movable contact supporting piece has the shape of a blade which engages in the opening of the U.

6. The contactor as claimed in claim 5, characterized in that said connection members comprise: a first hollow insulating piece or contact holder (9) rigidly coupled to the movable part of the electromagnet and inside which is fixed said first magnetic piece (10), a second insulating piece (13) closing the upper end of the first piece (9), and a spring (14) which forms said resilient contact pressure member and bears, on the one hand, on said second insulating piece (13) and, on the other hand, on a third insulating piece (15) itself bearing on the ends of said movable contact supporting piece (11) and in that said part (110c) is situated between said two ends.

7. The contactor as claimed in claim 1, characterized in that said second magnetic piece (17) is maintained in abutment, by said resilient member (14), against said part of said mobile contact supporting piece (18) and forms an air gap with said first magnetic piece (19).

8. The contactor as claimed in claim 7, characterized in that said connection members comprise: a first hollow insulating piece (9) having a lower bearing portion on which said first magnetic piece (19) is fixed, a second insulating piece (13) closing the upper end of the first insulating piece (9), and a spring (14) which forms said resilient contact pressure member and bears, on the one hand, on said second insulating piece (13) and, on the other hand, on a third insulating piece (16) itself bearing on said second magnetic piece (17).

9. The contactor as claimed in claims 7 or 8, characterized in that said movable contact supporting piece (18) is a blade forming a double break contact bridge (180a-180b) comprising a central V-shaped part, said two magnetic pieces (17, 19) being themselves in the form of blades comprising a central V-shaped part for cooperation with the preceding one.

10. The contactor as claimed in claim 2, characterized in that the electromagnet is energized by a rectified current during the holding phase.

11. A circuit for supplying a load, protecting same and for protecting the lines, comprising, in combination, a contactor member according to one of claims 1 to 10 and an overload current breaking and limiting member, in series with the principal contacts of the contactor member, in which the limiting member limits the peak currents to a value less than fifty times the rated current of the contactor.

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