EP0025375B1 - Circuit breaker with magnetic blow-out means and rotating arc - Google Patents

Description

The invention relates to a magnetic blow switch in rotation of the arc as defined in the preamble of claims 1 and 3.

Known with rotary arc switches (FR-A-2 339 244 by the applicant) which have the advantage over self-blowing switches of not requiring significant efforts to control opening. The commercial success of these switches has confirmed the validity of this technique and the present invention relates to improvements allowing an increase in performance, in particular the breaking capacity of these switches.

It is also known (GB-A-479 097) to reinforce the magnetic blowing field in rotation of the arc by a ferromagnetic core inserted in the blowing coil. To ensure the proper functioning of the switch, it is essential to guide the movement of the arc to keep it in the optimal magnetic blowing zone, the arc being substantially perpendicular to the blowing field. To do this, the arc must be maintained on a relatively narrow migration path from the opposite arc root and attached to the end face of the coil. The switch described in the aforementioned document GB-A-479 097 comprises a wide disc-shaped track covering the coil and the core and the arc can migrate towards the central zone with reduced blow. The core is permanently connected in series with the coil which decreases the intensity of the current in the coil.

To avoid striking the arc on the neighboring nucleus of the annular electrode, it has been proposed to cover this nucleus with an insulating cap (US-A-2,439,952). The presence of an insulating material in the arc zone is detrimental to deionization.

Another known switch (FR-A-2 285 700) comprises a circular arc track externally surrounding a main contact with the interposition of an insulating screen between the main contact and the arc track. A magnetic core is arranged inside the blowing coil coming in slight projection from the latter on the side of the arc track, the core of which is spaced. The core is electrically connected to the main contact and in case of arcing on the core the coil is short-circuited.

The document FR-A-2 414 786 relates to a switch having a blowing coil with a front face entirely covered by a circular electrode in the shape of a disc. This wide electrode has the aforementioned drawbacks of migration from the arc to the weak magnetic blowing zone. This part is capped with an insulating material harmful to the extinction of the arc. The magnetic core at the back of the electrode is away from the arc area.

The object of the present invention is to remedy these drawbacks and as characterized in claims 1 and 3.

• - un empilage de disques conducteurs annulaires fendus, formant chacun une spire de la bobine et d'intercalaires isolants, assurant l'isolation électrique entre les disques successifs, les fentes des disques successifs étant décalées angulairement en hélice,
• - des ponts de contact insérés entre les disques successifs en étant encadrés par les fentes des disques adjacents, et
• - des tiges de serrage dudit empilage pour assurer par pression le contact électrique entre les disques et lesdits ponts de contact. L'effort de répulsion entre les disques et l'électrode d'arc est repris par des tirants en forme de tige, qui traversent des orifices ménagés dans l'empilage constitutif de la bobine. Ces tirants sont solidarisés à l'une de leurs éxtrémités à l'électrode annulaire appliquée contre la face frontale de la bobine. Ils sont reliés mécaniquement et électriquement par leurs extrémités opposées au support du noyau ferromagnétique et ils appartiennent à la liaison électrique entre l'électrode annulaire et le noyau pour porter ces derniers au même potentiel. Des fourreaux isolants entourent les tiges au passage de la bobine.

The presence of a ferromagnetic core, forming a yoke, allows an increase in the magnetic blowing field of the arc drawn between the contacts and an accelerated rotation of the roots of the arc avoiding any erosion of the contact tracks. The core is spaced and at the potential of the arc track avoiding migration and anchoring of the arc on the core. In the event of ignition on this core, the magnetic blowing by the coil is maintained, permitting a break in the arc. The blowing coil is connected directly in series with the arcing contacts and it is traversed by the fault current, in particular short-circuit. The electrodynamic forces exerted on the successive turns are in this case very important and can cause the coil to burst. According to an embodiment of the present invention, the coil comprises:

• - a stack of split annular conductive discs, each forming a turn of the coil and of insulating spacers, ensuring electrical insulation between the successive discs, the slots of the successive discs being angularly offset helically,
• contact bridges inserted between the successive discs, being framed by the slots of the adjacent discs, and
• - Clamping rods of said stack to ensure by pressure the electrical contact between the discs and said contact bridges. The repulsion force between the discs and the arc electrode is taken up by rod-shaped tie rods, which pass through orifices formed in the stack constituting the coil. These tie rods are secured at one of their ends to the annular electrode applied against the front face of the coil. They are mechanically and electrically connected by their opposite ends to the support of the ferromagnetic core and they belong to the electrical connection between the annular electrode and the core to bring the latter to the same potential. Insulating sleeves surround the rods as the coil passes.

According to another development of the invention, a cylinder head externally surrounds the blowing coil, so as to increase the magnetic blowing field in the zone of formation and extinction of the arc. The combined action of the inner core and the outer cylinder head provides a sufficient blowing field even during a low current cut.

• la figure 1 est une vue schématique en coupe axiale partiellement arrachée d'un pôle d'un interrupteur selon la présente invention, la vue de gauche représentant l'interrupteur en position fermée et la vue de droite représentant l'interrupteur en position ouverte;
• la figure 2 est une vue éclatée en perspective de l'empilage constitutif de la bobine de soufflage selon la fig. 1;
• la figure 3 est une coupe suivant la ligne III-III de la fig. 1.

Other advantages and characteristics of the invention will emerge more clearly from the description which follows of an embodiment of the invention, given by way of example and shown in the appended drawings, in which:

• Figure 1 is a schematic sectional view axial partially torn from a pole of a switch according to the present invention, the left view representing the switch in the closed position and the right view representing the switch in the open position;
• Figure 2 is an exploded perspective view of the stack constituting the blowing coil according to FIG. 1;
• Figure 3 is a section along line III-III of FIG. 1.

In the figures, a switch includes an elongated waterproof insulating envelope 10 filled with sulfur hexafluoride under pressure, for example a few bars. Inside the casing 10 are housed a set 12 of fixed contacts and a set of movable contacts 14 mounted for axial sliding and controlled by an oscillating arm 15 for controlling a control mechanism (not shown in FIG. 1), but which may be of the type described in the aforementioned document FR-A-2 339 244, to which reference will advantageously be made for further details.

The movable contact assembly 14 comprises a movable main contact 16 in the form of a cup, the annular end 18 of which faces the fixed contact assembly 12 is arranged in the migration path of an arc root. The bowl 16 is fixed at its base to a sliding control rod 20 secured by a slide 22 to the control arm 15. Inside the bowl contact 16 is semi-fixed an arcing contact 24 having an annular electrode 26 forming an annular arc migration track. The arcing contact 24 is biased in the abutment position against a collar 28 in the direction of the set of fixed contacts 12 by a spring 30. In the abutment position the annular electrode track 26 of the arcing contact 24 is substantially at level of the annular end 18 of the movable main contact 16.

The set of fixed contacts 12 is secured to the bottom 32 of the insulating casing 10 by a bracket 34 having a fixing plate 36, which has a central orifice for the passage of a ferromagnetic core 38 and orifices distributed over a circumference surrounding the core 38. The set of fixed contacts 12 essentially comprises a fixed arcing contact 42 in the form of an annular track capable of cooperating by abutment with the movable arcing contact 24 of the same configuration, a tubular blowing coil 44 and a fixed main contact 46 having an annular contact face capable of cooperating by abutment with the main movable contact 16. Inside the main fixed contact 46 in the form of a cup is disposed a yoke 48 made of ferromagnetic material, which matches the shape of the contact main 46 by laterally surrounding the coil 44. The end face 50 of the core 38 is substantially at the level of the fixed arcing contact 42, the ends of the main fixed contact 46 and of the yoke 48 being slightly set back relative to the fixed arcing contact 42. It is easy to see that the yoke 48 and the core 38, which passes through it, constitute a magnetic sheathing circuit of the tubular coil 44 having an air gap in the contact zone between the movable arcing contact 24 and the fixed arcing contact 42.

The coil 44 is constituted by a stack, described in detail below with reference to FIGS. 2 and 3, crossed by the clamping rods or tie rods 40. The latter are fixed by one of their ends to the annular track, for example by welding and successively pass through orifices formed in a phase shift ring 52, in the coil 44, in the cylinder head 48, in the fixed main contact 46, in the clamp 34 and in a plate 54 for supporting the core 38. Nuts 56 screwed onto the threaded ends of the tie rods 40 keep the constituent parts of the fixed contact assembly 12 assembled. The phase-shifting ring 52 of large section covers almost all of the front face of the coil 44 against which it is applied by being inserted between this front face and the annular track. The outer edge 58 of the phase shift ring 52 is chamfered to limit the risk of arcing on the adjacent main contact 46. The tie rods 40 and the support plate 54 are electrically isolated from the coil 44, from the fixed main contact 46 and from the stirrup 34 by insulating sleeves 60 with flange 62 threaded on the tie rods 40.

The insulating casing 10 has at its upper part a connection bushing 64 electrically connected to the stirrup 34 and at its lower part a bushing 66 electrically connected by a flexible conductor 68 to the set of movable contacts 14. Braids 70, described below, electrically connect the movable arcing contact 24 to the movable main contract 16.

• En position fermée, représentée sur la demi-vue dé gauche de la fig. 1, l'ensemble de contacts mobiles 14 est maintenu au contact de l'ensemble de contacts fixes 12, les pistes annulaires d'arc étant aboutées ainsi que les contacts principaux 16, 46. Le courant entrant par exemple par la traversée 64 parcourt l'étrier 34, le contact principal 46, pressé par les tirants 40 contre l'étrier 34, le contact principal 16, le conducteur souple 68 et la traversée 66. Parallèlement, aux contacts principaux 46, 16, le courant peut parcourir un circuit dérivé constitué par la bobine 44, l'anneau de déphasage 52, le contact mobile d'arc 42, le contact semi-fixe d'arc 24, les tresses 70 pour aboutir au contact principal 16. L'impédance de ce circuit dérivé étant notablement supérieure à celle du circuit principal, la quasi-totalité du courant parcourt ce dernier circuit principal en fonctionnement normal. L'ouverture de l'interrupteur est commandée par un dispositif de déclenchement usuel ne faisant pas partie de la présente invention et pouvant être du type décrit dans le document FR-A-2 339 244. Le pivotement du bras de commande 16 vers le bas sur la fig. 1 provoque le coulissement de la tige 20 qui entraîne dans son déplacement l'ensemble des contacts mobiles 14. En une première phase les contacts principaux 16, 46 se séparent en tirant un arc de commutation, les contacts d'arc 24, 42 restant temporairement en aboutement sous l'action du ressort 30. La séparation des contacts principaux 16, 46 provoque la commutation du courant dans le circuit dérivé à travers la bobine 44, qui engendre un champ magnétique de soufflage. Le champ magnétique radial engendré par la bobine 44 dans la zone de séparation des contacts principaux 16, 46 provoque une rotation de l'arc de commutation facilitant son extinction. Dans une deuxième phase d'ouverture de l'interrupteur le contact d'arc mobile 24 vient en butée du collet 28 et est entraîné vers le bas, de manière à séparer les pistes annulaires en tirant un arc entre ces dernières (demi-vue de droite de la fig. 1 ). L'arc tiré entre les pistes s'étend dans l'entrefer ménagé entre la culasse 48 et le noyau 38 et est soumis à un champ de soufflage particulièrement intense qui provoque une rotation rapide sur les pistes annulaires. L'anneau de déphasage 52, disposé dans cet entrefer et à proximité immédiate de la piste (contact d'arc 42), entretient ce champ magnétique au passage au zéro du courant pour favoriser l'extinction de l'arc à cet instant. Dès l'interruption du courant, la bobine 44 n'est plus alimentée.

The switch according to the invention operates as follows:

• In the closed position, shown in the left half-view of FIG. 1, the set of movable contacts 14 is kept in contact with the set of fixed contacts 12, the annular arcing tracks being abutted as well as the main contacts 16, 46. The current entering for example by the crossing 64 runs through the caliper 34, the main contact 46, pressed by the tie rods 40 against the caliper 34, the main contact 16, the flexible conductor 68 and the bushing 66. At the same time, at the main contacts 46, 16, the current can flow through a branch circuit constituted by the coil 44, the phase shift ring 52, the movable arcing contact 42, the semi-fixed arcing contact 24, the braids 70 to lead to the main contact 16. The impedance of this branch circuit being notably greater than that of the main circuit, almost all of the current flows through the latter main circuit in normal operation. The opening of the switch is controlled by a usual tripping device which is not part of the present invention and may be of the type described in document FR-A-2 339 244. The pivoting of the control arm 16 downward in FIG. 1 causes the rod 20 to slide, which causes all of the movable contacts to move in its displacement. In a first phase, the main contacts 16, 46 separate by drawing a switching arc, the arcing contacts 24, 42 remaining temporarily abutting under the action of the spring 30. The separation of the main contacts 16, 46 causes the switching of the current in the branch circuit through the coil 44, which generates a magnetic blowing field. The radial magnetic field generated by the coil 44 in the separation zone of the main contacts 16, 46 causes a rotation of the switching arc facilitating its extinction. In a second phase of opening the switch, the movable arcing contact 24 abuts the collar 28 and is driven downwards, so as to separate the annular tracks by drawing an arc between them (half-view of right of Fig. 1). The arc drawn between the tracks extends into the air gap formed between the cylinder head 48 and the core 38 and is subjected to a particularly intense blowing field which causes rapid rotation on the annular tracks. The phase shift ring 52, disposed in this air gap and in the immediate vicinity of the track (arcing contact 42), maintains this magnetic field when the current crosses zero to promote the extinction of the arc at this instant. Upon interruption of the current, the coil 44 is no longer supplied.

The core 38, mechanically and electrically secured by the plate 54 and the tie rods 40 to the annular track, is at the same potential of the latter and in the event of arcing on the end face 50 of the core 38 the current borrows a circuit constituted by the core 38, the plate 54, the tie rods 40, the arcing contact track 42 and the coil 44, keeping the latter energized. Any initiation of the arc on the core 38 keeps the blowing in rotation of the arc favoring its extinction. The chamfer 58 of the phase shift ring 52 prevents any migration of the arc to the main contact 46 and any ignition thereon. The coil 44 generates both a blowing field of the switching arc drawn between the main contacts 16, 46 and of the cutting arc drawn between the annular tracks (arcing contacts 26, 42).

The presence of iron, due to the core 38, inside the coil 44 increases the efficiency of the latter. The presence of the cylinder head 48 externally sheathing the coil 44 increases this action and is particularly advantageous during the breaking of low current.

Referring more particularly to FIGS. 2 and 3, which show the coil 44, we recognize the annular track, the phase shift ring 52 and the tie rods 40, on which are insulated inserts 72 and split conductive discs 74 alternately. The inserts 72 and the slotted discs 74 have holes for the passage of the tie rods 40 and they are placed so as to angularly offset the slots 76 of the successive conductive discs 74. In the example shown in FIG. 2, the coil 44 is crossed by six tie rods 40 distributed regularly and each conductive disc 74 is angularly offset by a sixth of a turn, in this case 60 ° relative to the adjacent disc 74. In each insulating insert 72 is inserted a metal washer 78 capable of ensuring a contact bridge between the adjacent conductive discs 74. The washers 78 of the successive inserts are offset by the same angle as the offset of the slots 76, a washer 78 being always framed by the slots 76 of the two adjacent conductive discs 74. It can be seen that in the assembled and compressed position of the discs 74 and spacers 72 the current flows from a disc 74 to the next disc by the washers 78 forming a contact bridge, this current describing a propeller whose successive turns are each formed by one of the conductive discs 74. The coil 44 may include any number of discs 74 and spacers 72. The washers 78 and in particular the washer interposed between the last disc 74 and the phase shift ring 52 can have a certain elasticity, imparted by their Belleville type structure. The elasticity of the Belleville washers makes it possible to compensate for thermal expansions, in particular the elongation of the tie rods 40 and avoids any interruption in the electrical continuity between the successive discs 74. The production of such a coil is particularly simple and the - tie rods 40 effectively oppose the repulsion forces which are exerted between the turns and the phase shift ring 52 when the coil 44 is traversed by an intense current, in particular a short circuit.

Fig. 3 illustrates the mode of electrical connection between the movable arcing contact 24 and the movable main contact 16 in the form of a bowl. The connection braids, in the example shown in fig. 3, the pair of braids 70, are on the one hand fixed by one of their ends to the internal wall of the bowl 16, for example by screws 80, the opposite end being fixed to a finger 82 carried by the movable contact 24. The braids 70 extend along the periphery of the bowl 16 with sufficient clearance for the relative movement of the movable arcing contact 24. It is easy to see that the braids 70 come to be applied under the loop effect against the internal wall of the main contact 16, when they are traversed by a current, the contact 16 limiting the deformation of these braids 70. The contact 16 constitutes a hoop preventing any excessive deformation.

The switch disconnection assembly according to the invention is particularly simple and its manufacturing and mounting cost is low. The addition of main contacts ensures reliable electrical contact.

Claims (6)

1. Switch with magnetic blow-out in arc rotation comprising:

- a pair of separable contacts (24, 42) each having a ring-shaped electrode forming a rotation track of the root of an arc drawn when said contacts are separated,

- a tubular coil (44) coaxial to said electrodes and having a terminal side (52) coupled to one of said ring-shaped electrodes on the opposite side of said track, said coil (44) being electrically connected on the one hand to one of the switch terminals (64, 66), and on the other hand to the coupled electrode so as to be electrically supplied in series of an arc tied on the coupled electrode and to generate a radial magnetic field in the extension zone of said arc.

- a conducting ferromagnetic core (38) coaxially extending inside the coil (44) to intensify the magnetic field of the arc blow-out,

the front side (50) of the core (38) being adjacent and separated from said coupled electrode by a free gap, characterized in that said core (38) is electrically connected to said coupled electrode.

2. Switch according to claim 1, characterized by support rods (40) of said coupled electrode extending parallel to the axis of the coil (44) and of the electric and mechanical connection means (54) of the loose terminals of these rods (40) and said core (38) opposite to the arc zone.

3. Magnetic blow-out switch comprising a pair of separable contacts (24, 42), a ring-shaped electrode associated to one of said contacts and a tubular coil (44) coaxially disposed and adjacent to said ring-shaped electrode characterized by the fact that said coil (44) comprises:

- a stacking of slit ring-shaped conducting disks (74) each making a turn of the coil and of insulating insertions (72) ensuring the electric insulation between the successive disks (74), the slits (76) of the successive (74) disks being angularly helical shifted,

- contact bridges (78) inserted between the successive disks (74) by being enclosed by the slits (76) of the adjacent disks and

- tightening rods (40) of said stacking going through aligned apertures accommodated in said disks (74) and insertions (72) and circumferentially distributed to ensure the electric contact between the disks (74) and said contact bridges (78) by pressure.

4. Switch according to claim 3, characterized in that said contact bridges (78) comprise washers named Belleville, threaded on the tightening rods and showing a resilience to compensate the thermal or mechanical expansions, said washers being inserted in an aperture with a corresponding section of the insertion (72).

5. Switch according to claim 1 and claim 3 or 4, characterized by rods (40), one of the leads of which is secured. to a ring-shaped electrode applied on the end side of the coil (44), said rods (40) going through said stacking by apertures and being connected to said ferromagnetic core (38) by their opposite end, so as to constitute rods to support the electrode and to tight the constituent stacking of the coil (44).

6. Switch according to claim 5, characterized in that a magnetic yoke (48) surrounds said coil (44) on the outside by being fastened with the core (38) and the coil (44) to a support (36) by said rods (40).

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