EP0406130B1 - Limiting circuit-breaker provided with electromagnetic means for delaying the return movement of the contact - Google Patents

Description

• un système de contacts à répulsion électrodynamique ayant un bras support conducteur équipé d'un premier contact, et un contact mobile ayant au moins un deuxième contact coopérant en position de fermeture avec le premier contact, ledit contact mobile étant propulsé vers la position d'ouverture par des forces électrodynamiques engendrées durant une première phase de répulsion après dépassement par le courant d'un seuil prédéterminé,
• et un verrou électromagnétique anti-retombée susceptible d'occuper une position active pour maintenir temporairement le contact mobile ouvert après répulsion.

The invention relates to a limiting circuit breaker with molded insulating housing, comprising in each pole:

• an electrodynamic repulsion contact system having a conductive support arm equipped with a first contact, and a movable contact having at least a second contact cooperating in the closed position with the first contact, said movable contact being propelled towards the open position by electrodynamic forces generated during a first repulsion phase after the current exceeds a predetermined threshold,
• and an electromagnetic anti-fallout lock capable of occupying an active position to temporarily maintain the movable contact open after repulsion.

An electromagnetic anti-fallout lock for limiting circuit breaker is already known from documents US-A-4 409 573, DE-A-1 463 310 and FR-A-2 272 479. The actuation of the lock towards the active position results from l 'intervention of electromagnetic attraction forces generated by the passage of a strong current in the pole.

According to document US-A-4 409 573, the lock is formed by a hooking blade capable of cooperating with a notch provided at one of the ends of the movable contact arm on the side of the bar. The distance of the lock from the contact parts between which the arc is established requires the installation of a steel ring surrounding the bar to reinforce the effect of electromagnetic attraction on the lock.

The latching effect of the movable contact in the repelled position has the disadvantage of preventing any possibility of selectivity in the circuit. The dropout takes place by the rotation of the bar after triggering of the mechanism.

Another anti-fallout device (see document US-A-4,612,430) uses a different technique implementing the acceleration of the mobile contact during the electrodynamic repulsion to act initially by mechanical effect on the lock, which is then attracted completely. to the active position by magnetic attraction.

The object of the invention is to improve the production of an electromagnetic anti-fallout lock for a limiting circuit breaker.

According to the invention, the electromagnetic lock comprises a magnetic circuit surrounding the support arm in the vicinity of the first and second contacts to obtain maximum electromagnetic attraction from the birth of the arc, causing the lock to move rapidly towards the active position, said circuit magnetic being equipped with support means in the form of ramps urging the lock to an inactive position by the action of returning the movable contact in the closing direction.

The lock is electrically isolated from the support arm by an insulating coating.

In a first embodiment, the electromagnetic lock comprises a magnetic circuit formed by a pair of semi-mobile stirrups arranged symmetrically with respect to the median plane of the pole so as to define a first lower air gap and a second upper air gap, each stirrup being housed in an isolation screen and having an extension shaped as a retaining ramp, on which the mobile contact rests in the restraint, on which the movable contact bears in the active position of said lock.

The arc is pinched in the upper air gap when the lock is in the active position.

After extinction of the arc, the electromagnetic attraction effect disappears, and the bolt is pressed towards an inactive position. The retaining ramp of each stirrup has a predetermined inclination relative to the median plane which contributes to the release of the lock towards the inactive position under the action of the restoring force of the movable contact.

Each stirrup has a first pole face separated from a second pole face by a semi-open notch framing the upper branch of the loop of the support arm when the latch is actuated towards the active position.

According to a second embodiment, the electromagnetic lock comprises a fixed U-shaped magnetic circuit and a pivoting pallet urged by a return spring in engagement against the pole face of the magnetic circuit.

• la figure 1 est une vue schématique en coupe d'un pôle de disjoncteur limiteur à double coupure équipé de deux verrous à accrochage électromagnétique selon l'invention, le disjoncteur étant représenté en position de fermeture;
• la figure 2 est une vue en coupe selon la ligne 2-2 de la figure 1, le verrou étant en position inactive;
• la figure 3 montre une vue identique à celle de la figure 2, en position active du verrou;
• la figure 4 représente une vue partielle du disjoncteur de la figure 1, avec une variante de réalisation du verrou anti-retombée.
• la figure 5 est une vue identique de la figure 3 d'une variante de réalisation, la demi-vue de gauche représentant le verrou en position inactive, et la demi-vue de droite montrant le verrou de position active (traits forts), et dans une position intermédiaire (traits en pointillé).

Other advantages and characteristics will emerge more clearly from the description which follows of the two embodiments given by way of nonlimiting examples, and represented in the appended drawings in which:

• Figure 1 is a schematic sectional view of a double break limiter circuit breaker pole equipped with two latches with electromagnetic latching according to the invention, the circuit breaker being shown in the closed position;
• Figure 2 is a sectional view along line 2-2 of Figure 1, the latch being in the inactive position;
• FIG. 3 shows a view identical to that of FIG. 2, in active position of the lock;
• 4 shows a partial view of the circuit breaker of Figure 1, with an alternative embodiment of the anti-fallout latch.
• FIG. 5 is an identical view to FIG. 3 of an alternative embodiment, the half-view on the left representing the lock in the inactive position, and the half-view on the right showing the lock in the active position (strong lines), and in an intermediate position (dotted lines).

In FIG. 1, a breaking pole 10 of a multipole limiting circuit breaker, with molded insulating housing 12, comprises a rotary contact 14 with double breaking. The central part of the rotary contact 14 is mounted in a housing of a rotary switching bar 1 6, common to all of the poles. The general structure of pole 10 is described in document EP-A-314,540.

The rotary contact 14 comprises a pair of opposite lever arms 18, 20, each having at their ends a contact piece 22, 24 cooperating with a fixed contact 26, 28 conjugated in the form of a pellet.

Each fixed contact 26, 28 is secured to the internal end of an arm 30, 32 of conductive material, having a loop or U shape. The electrical connection of the pole 10 takes place by means of two connection pads 34 , 36 arranged at the outer ends of the support arms 30, 32 passing through the insulating housing 12.

The rotary contact 14, and the two support arms 30, 32 constitute the active parts made of copper.

Two arc extinguishing chambers 38.40 arranged on either side of the bar 16 are associated with the pairs of contacts 22.26; 24.28. A system of springs 42 makes it possible to obtain the contact pressure in the closed position of the movable contact 14.

The rotary bar of insulating material is mounted for rotation about an axis 43 between a first and a second position corresponding respectively to the closing and to a normal opening of the contacts. The axis 43 extends in the central zone of the housing 12, perpendicular to the plane of FIG. 1. The bar 16 serves as a drive member for all of the rotary contacts 14 of the different poles of the circuit breaker, and is coupled to the control mechanism (not shown), which is actuated manually by a joystick, and automatically by a selective trigger.

The operation of such a limiting circuit breaker is well known to specialists, and it suffices to describe it briefly:

The appearance in pole 10 of a short-circuit current whose intensity exceeds a predetermined threshold, generates electrodynamic repulsion forces between the contacts 22,26, 24,28. This results in a rapid displacement of the movable contact 14 towards the open position, before the intervention of the mechanism having received a trip order from the trip device. The bar 16 remains stationary in the first position (Figure 1) during this first phase of electrodynamic repulsion, and only the rotary contact 14 is moved to the open position to draw a double arc between the contacts 22,26; 24.28, making it possible to obtain a significant current limiting effect. The arc is extinguished in a conventional manner in rooms 38.40.

The rotation of the bar 16 to the second position occurs when the response time of the mechanism has elapsed, so as to confirm the definitive opening of the circuit breaker. This rotational movement of the bar 16 takes place during a second phase of mechanical actuation of the mechanism, which takes over from the first repulsion phase.

The first phase is not operational when the intensity of an overload current is below the repulsion threshold. The current limiting effect does not exist in this case, and it will be necessary to wait for the intervention of the bar 16 after tripping of the mechanism, to ensure the normal automatic opening of the circuit breaker.

To prevent automatic reclosing of the movable contact 14 during the first phase of electrodynamic repulsion, it is necessary to provide an anti-fallout system which allows temporary locking of the movable contact 14 in the open position, ie until the extinction of the arc, or until the intervention of the bar 16 after triggering of the mechanism.

According to the invention, the anti-drop system of the movable contact 14 of each pole comprises a pair of electromagnetic latches 44, 46 (FIG. 1), arranged on either side of the bar 16, in the vicinity of the pairs of contacts (22 , 26, 24, 28) corresponding. The structure of the two locks 44, 46 is identical, and only that of the lock 44 will be described in detail with reference to FIGS. 2 and 3.

The electromagnetic latch 44 is made up of two semi-mobile stirrups 48.50 made of ferromagnetic material, in particular steel, cooperating with a spring return leaf 52.

The two stirrups 48.50 have a U or C shape, and are arranged opposite one another, and symmetrically with respect to the vertical median plane of trace 54, so as to surround the upper branch of the support arm 30 at the level of the fixed contact 26. Each stirrup 48.50 has a first pole face 56 vertically separated from a second pole face 58 by a semi-open notch 60 capable of conforming to the lateral configuration of the support arm 30.

Opposite the first pole face 56, each bracket 48.50 is equipped with an extension shaped as a ramp 62 for retaining having a predetermined inclination, relative to the second pole face 58.

The leaf spring 52 extends in the longitudinal direction of the axis 43 of the bar 16 and is supported by its opposite ends on two lugs 64,66 belonging to the two symmetrical stirrups 48.50. The curved middle part of the spring leaf 52 is interposed between the first pole faces 56 and the lower branch of the support arm 30.

The ramp 62 for retaining, the second pole face 58, the notch 60 and the base of each stirrup 48.50 are advantageously covered by a coating 68 of gas-generating insulating material, in particular polyamide. The entire surface of the stirrups 48.50 can be coated with this insulating material, except for the first pole faces 56 delimiting the lower air gap 70.

The semi-movable stirrups 48.50 of the latch 44 extend into housings 72.74 confined by two fixed symmetrical screens 76.78 projecting from the opposite side walls of the housing 12 and coming from molding with the latter. The presence of these 76.78 dust screens prevents the penetration of beads or particles behind the 48.50 stirrups, and contributes to strengthening the dielectric strength of the circuit breaker.

The operation of the electromagnetic lock 44 according to FIGS. 2 and 3 is as follows:

In the closed position of the contacts 22, 26 (FIG. 2), the return leaf spring 52 ensures maximum spacing between the two stirrups 48.50, which are held in abutment against the internal wall of the housing 12, The latch 44 is open and in a stable inactive position, ready to allow free movement of the movable contact 14 in good time.

During manual opening of the circuit breaker by the handle, the latch 44 remains stationary in the inactive position. So is even during an automatic opening by triggering of the mechanism, caused by the detection of an overload current below the repulsion threshold.

The passage in the pole 10 of a strong current, in particular of short-circuit higher than said threshold causes the electrodynamic repulsion of the movable contact 14, which is propelled during the first phase towards the open position, while the bar 16 remains stationary in the first position. The displacement by repulsion of the movable contact 14 is reinforced by the presence of the magnetic circuit constituted by the two stirrups 48, 50 of the latch 44. The direction of flow of the current I in the pole 10 is indicated by way of example in FIG. 3 , and it is noted that this current I generates an electromagnetic field B which closes by the two lower gaps 70 and upper 80, formed respectively between the first pole faces 56, and between the second pole faces 58 of the latch 44. This results in a approximation of the two stirrups 48.50 thanks to the magnetic attraction forces which prevail over the antagonistic force of the leaf spring 52. The coming into engagement on the one hand of the first polar faces 56, and on the other hand of the second faces polar 58 keeps the latch 44 closed in an active position. The two retaining ramps 62 form a V-shaped stop, which temporarily retains the movable contact 14 when it comes to fall by gravity after reduction of the repulsion forces. The latch 44 is arranged to remain in the active position until the arc is extinguished. This then results in the disappearance of the electromagnetic field, causing the automatic separation in scissors of the two stirrups 48.50 by the return action of the movable contact 14. The movable contact 14 can then either close if the fault current was fugitive, or be kept in the open position by the rotation of the bar 16 in the second position, after triggering of the mechanism.

The presence of the latch 44 in the vicinity of the contacts 22, 26 makes it possible to have a large electromagnetic field for the attraction of the two stirrups 48.50 towards the active position. The stirrups 48, 50 are shaped according to a clamp, which is closed in the active position.
The inclination of the ramps 62 for retaining the movable contact 14 contributes to the release of the stirrups 48.50 towards the inactive position of the latch 44. An acute angle is formed between each ramp 62 and the vertical median plane of trace 54. This results in a progressive opening of the clamp towards the inactive position by the action of falling down of the movable contact 14.

The arc is pinched in the upper air gap 80 when the latch 44 is in the active position. The presence of the insulating coating 68 on the two stirrups 48.50 contributes to improving the extinction of the arc in the chamber 38 by gasogenic effect.

The intervention of the two latches 44, 46 delays the reclosing of the movable contact 14 with respect to its natural fall-back time. A deformable insulating protective sheet 90, in particular made of polytetrafluoroethylene, is inserted between the upper branch of the support arm 30 and the notches 60 of the two stirrups 48.50, of the latch 44 to prevent any penetration of balls or other metallic particles into the 'air gap 70 lower.

In the variant of FIG. 4, the same reference numbers will be used to designate parts identical to those of the device in FIGS. 1 to 3. The electromagnetic lock 146 of the movable contact 14 comprises a fixed magnetic circuit 100 in the shape of a U, and a pallet 102 articulated on an axis 104. A spring 106, in particular of traction, urges the pallet 104 into engagement against the pole face of the magnetic circuit 100.

The lever arm 20 of the movable contact 14 is provided with a retaining lug 108 cooperating with a hooking ramp 110 located in the intermediate part of the pallet 102. The oblique ramp 110 has an angle 111 of inclination (approximately 10 degrees) with normal.

In the closed position of the limiting circuit breaker, the pallet 102 is applied against the magnetic circuit 100 by the return force of the spring 106. The contact piece 24 of the movable contact 14 is in engagement with the fixed contact 28. The circuit 100 is covered by an insulating coating 114.

During the electrodynamic repulsion of the movable contact 14, the lug 108 abuts against the pallet 102, and moves it away from the pole face of the magnetic circuit 100 against the restoring force of the spring 106. After passing the neck 112, the lug 108 is housed in the hollow of the ramp 110. The magnetic field B generated by the arc current I then applies the paddle 102 against the magnetic circuit 100 and the movable contact 14 remains blocked by the lug 108 in the open position.

When the circuit breaker closes, the bar 16 rotates counterclockwise, and drives the movable contact 14 in the same direction. The angle 111 of inclination of the ramp 110 allows the pallet 102 to be released under the action of the unlocking torque generated by the relaxation of the spring system 42 of contact pressure. This unlocking torque prevails over the torque implemented by the return spring 106, and the pallet 102 pivots clockwise to allow the displacement of the movable contact 14 towards the closed position.

According to the variant of FIG. 5, the pivoting movement of the stirrups 48, 50 towards the inactive position under the return effect of the movable contact 14 after the arc has been extinguished, is preceded by a downward translation movement (see arrow F) of low amplitude. This translational movement is authorized by the presence of a clearance J between the base of the stirrups, and the lower branch of the support arm 30, and of a second leaf spring 152 having a curved middle part which urges the stirrups 48, 50 against the upper arm 30.

These two movements of the stirrups 48, 50 of the latch 44 make it possible to adjust the fall time of the movable contact 14. It is noted that the shock of the contact 14 on the ramps 62 of the stirrups 48, 50 acts on the whole mass of the latch 44 during the first translational movement (see dotted position), while the second posterior pivoting movement which ensures the unlocking acts on the upper part of the stirrups 48, 50 by involving only a fraction of the mass.

The invention also applies to a modular limiter block that can be coupled and electrically connected to a standard circuit breaker. The mobile contact can also be a single break.

Claims (10)

1. A limiting circuit breaker with a moulded insulating case (12), comprising in each pole :

   - an electrodynamic repulsion contact system having a conducting support arm (30, 32) equipped with a first contact (26, 28), and a movable contact (14) having at least a second contact (22, 24) cooperating in the closed position with the first contact (26, 28), said movable contact (14) being driven to the open position by electrodynamic forces generated during a first repulsion phase after the current has exceeded a preset threshold,

   - and an electromagnetic latch (44, 46, 146) controlled by the flow of current in the pole, and capable of occupying an active position to temporarily keep the movable contact (14) open after repulsion,

   characterized in that the electromagnetic latch (44, 46, 146) comprises a magnetic circuit surrounding the support arm (30, 32) in the vicinity of the first and second contacts (26, 28, 22, 24) to obtain a maximum electromagnetic attraction as soon as the arc originates, causing high-speed movement of the latch (44, 46, 146) to the active position, said magnetic circuit being equipped with bearing means in the form of ramps (62, 110) urging the latch (44, 46, 146) to an inactive position by the return action of the movable contact (14) in the closing direction.
2. The limiting circuit breaker according to claim 1, characterized in that the latch (44, 46, 146) is electrically insulated from the support arm (30, 32) by an insulating coating (68, 114).
3. The limiting circuit breaker according to claim 1 or 2, characterized in that the magnetic circuit of the ferromagnetic latch (44, 46) comprises a pair of semi-mobile brackets (48, 50) arranged symmetrically with respect to the mid-plane of the pole so as to define a first lower air-gap (70) and a second upper air-gap (80), each bracket (48, 50) being housed in an insulating shield (76, 78) and having an extension shaped as a retaining ramp (62), on which the movable contact (14) bears in the active position of said latch.
4. The limiting circuit breaker according to claim 3, an arc being drawn between the first and second contacts (26, 28, 22, 24) during the first repulsion phase, characterized in that the two brackets (48, 50) cooperate with a flexible return device urging the latch (44, 46) to the inactive position when the first and second contacts are in the closed position.
5. The limiting circuit breaker according to claim 4, characterized in that the flexible return device of the latch (44, 46) is formed by a spring blade (52, 152) having a curved middle part, and two opposite ends bearing on the brackets (48, 50).
6. The limiting circuit breaker according to claim 4 or 5, characterized in that the retaining ramp (62) of each bracket (48, 50) has a preset inclination with respect to the mid-plane which facilitates clearing of the latch (44, 46) to the inactive position.
7. The limiting circuit breaker according to claim 3, characterized in that each bracket (48, 50) comprises a first polar face (56) separated from a second polar face (58) by a semi-open notch (60) framing the upper branch of the loop of the support arm (30, 32) when the latch (44, 46) is actuated to the active position, so as to causing a pinching effect of the arc in the second upper air-gap (80).
8. The limiting circuit breaker according to claim 7, characterized in that the second polar face (58) is located between the retaining ramp (62) and the semi-open notch (60), and that the first polar face (56) is arranged inside the loop between the upper and lower branches of the support arm (30, 32), an insulating protective strip being inserted between the upper branch of the support arm (30, 32) and the first lower air-gap (70).
9. The limiting circuit breaker according to claim 1 or 2, characterized in that the U-shaped magnetic circuit (100) of the electromagnetic latch (146) comprises a pivoting blade (102) urged by a return spring (106) in engagement against the polar face of the fixed magnetic circuit (100), and that the movable contact (14) is fitted with a retaining pin (108) cooperating with a latching ramp (110) located in the intermediate part of the blade (102), said ramp (110) having a predetermined inclination enabling the blade (102) to be cleared when closing movement of the circuit breaker takes place.
10. The limiting circuit breaker according to claim 5 or 6, characterized in that the spring blade (152) is shaped in such a way as to provide a predetermined clearance (J) between the base of the brackets (48, 50) and the lower branch of the support arm (30), to enable a first translation movement of the latch (44) before the second pivoting movement to the inactive position due to the return effect of the movable contact (14).

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