DE10219022B3 - Contact arrangement for current-limiting circuit breakers - Google Patents

Abstract

The invention relates to a contact arrangement for current-limiting circuit breakers in the low-voltage range, in particular for current-limiting circuit breakers. A rotary contact bridge (10) is connected to a switching shaft (6) via four contact force tension springs (18) arranged symmetrically in pairs on both sides of the contact bridge (10). In order to delay the release of the contact bridge (10), which is electrodynamically repelled by stationary contacts (16), spring elements (36) mounted in the control shaft (10) have a braking effect against control cams (34) formed on the contact bridge (10).

Description

The invention relates to a contact arrangement for current-limiting Circuit breakers in the low-voltage range, especially for current-limiting ones Circuit breaker, according to the preamble of claim 1.

From the publication EP-0314540-B1 Such a contact arrangement for a multipole low-voltage circuit breaker with an insulating housing is known, which has a switching shaft which can be rotated about a fixed transverse axis by means of slide bearings formed in the housing, the axis being perpendicular to the longitudinal center plane of each pole. Each pole comprises two fixed contacts connected to connecting rails, a rotary contact bridge that extends along the central plane in a play-related receptacle of the selector shaft and has opposing contact pieces that cooperate with the fixed contacts in the switched-on position, and two tension springs attached inside the selector shaft that act on the contact bridge and thus ensure a fixed contact pressure of the contact pieces on the fixed contacts, one of the ends of each tension spring cooperating with a driver element of the selector shaft. The two springs are mounted in the contact bridge receptacle with the other end of each spring attached to a contact bridge fastener. The two fastening elements or driver elements of the two springs are point-symmetrical with respect to an imaginary axis of rotation of the contact bridge or the fixed transverse axis of the switching shaft. This arrangement of the springs ensures free movement of the imaginary axis of rotation of the contact bridge in relation to the fixed transverse axis of the selector shaft and at the same time enables a moment of force for uniform distribution of the contact pressure as well as an elastic positioning of the contact bridge with two translational degrees of freedom, the contact bridge due to the self-centering effect of the Springs are held in an equilibrium position on the median plane. The connecting rails with the fixed contacts are loop-shaped, so that, when a short-circuit current flows through them, they generate an electrodynamic force that repels the contact bridge against the force of the tension springs in the direction of a repulsion position. With a contact arrangement of this type there is a risk that the movable contact bridge spun open in the event of a short circuit by electrodynamic forces will damage its stop or fall back too quickly, which can lead to undesired re-ignitions of arcs and / or contact welds.

From the publication EP-0560697-B1 is known a low-voltage circuit breaker with a contact arrangement per pole, which is equipped on both sides of the contact bridge, which extends in the central plane of the pole, with two symmetrically arranged pairs of tension springs. The tension springs of each pair are arranged on both sides of the axis of rotation of the contact bridge and each have an end mounted on the contact bridge via a common holding rod. To slow down and, if necessary, hold the contact bridge electrodynamically repelled by the fixed contacts, an opposite end of the springs mentioned is mounted on the ends of a slide which is slidably displaceable in a notch in the selector shaft and is designed as a transverse axis, and the contact bridge has a pair of point-symmetrically arranged control cams. which are designed such that they cooperate with one of the rods in the end section of the repulsion stroke of the contact bridge in order to brake the movement of the contact bridge. The rods are mounted to be displaceable to a limited extent in the locking notches, the locking notches lying opposite one another in a point-symmetrical manner running approximately along the effective line of the associated springs. The springs ensure elastic positioning of the contact bridge in the cutout of the selector shaft and thereby define a fictitious axis of rotation of the contact bridge in relation to the selector shaft. The profile of the control cams arranged with respect to the movable contact pieces causes a displacement of the rods in the notch and a continuous tension of the springs corresponding to the pivoting movement of the contact bridge in the direction of the push-off position with a storage of the energy in the springs. The profile of the control cams can be designed so that the contact bridge locks in the push-off position; wherein the rotatably mounted switching shaft is actuated by an actuating mechanism of the circuit breaker and the opening stroke of the contact bridge is limited so that the rotation of the switching shaft during the opening movement causes the rods to lift off the control cams. During the pivoting movement of the contact bridge in the direction of the repulsion position, the line of action of each spring shifts and thereby shortens the lever arm, as a result of which the restoring force moment exerted by the springs on the contact bridge is reduced. Disadvantages of this contact arrangement are the additional requirement for the rods to be movably supported and the inadequate braking effect at high repulsive forces due to the small friction surfaces and friction coefficients between the steel rods and the copper contact bridge.

With a contact arrangement according to the publication EP-0978858-A2 grip four tension springs responsible for contact pressure between notches on the rotary contact bridge and on the switching shafts hinged tabs, which can pivot in such a way that the electrodynamically flung-on contact bridge cannot automatically fall back into the closed position. In a contact arrangement according to document WO-9962092-A1, four tension springs responsible for contact pressure engage between four rods. Two of the rods are mounted in the shafts of the selector shaft and act directly on the rotary contact bridge. The other two rods are slidably guided in slots in the selector shaft and engage in hinges connected to the contact bridge, which also prevent the electrodynamically flung-on contact bridge from falling back into the closed position on its own. The disadvantage of these two solutions is that, on the one hand, tabs which are expensive to connect to the control shaft are required and, on the other hand, due to the forced retention of the contact bridge in the flung-on position, a circuit breaker equipped with such contact arrangements is not suitable for selective switch arrangements.

From the publication EP-0406130-A1 a contact arrangement for a multi-pole current-limiting circuit breaker is known. A control shaft is rotatably mounted in an insulating housing around a fixed transverse axis. A rotary contact bridge extends in a playful receptacle of the switching shaft along the center plane of the pole and has point-symmetrically opposite contact pieces which cooperate with fixed contacts in the switched-on position. The rotary contact bridge has two retaining pins arranged perpendicular to the center plane and arranged in a symmetrical manner. A torsion spring system with first spring ends fixed to the contact bridge and second spring ends fixed to the switching shaft extends in the interior of the switching shaft on both sides of the contact bridge, the first spring ends being symmetrically opposite one another. Two connection rails, each connected to one of the fixed contacts, cause an electrodynamic transition of the contact bridge from the switch-on position to a repulsion position at very high currents. Electromagnetic contact locks each include a U-shaped magnetic circuit encompassing the associated connecting rail and an armature articulated on an axis. The armature is acted upon by a tension spring against the pole face of the magnetic circuit and interacts with one of the retaining pins via a locking bevel formed on it. In the event of electrodynamic repulsion of the contact bridge, the pin separates the armature from the pole face and, after overcoming a bending projection, reaches the locking bevel, as a result of which the rotary contact is blocked in the repulsion position. An independent return of the rotary contact to the switch-on position is prevented in any case. The anti-return devices require a large number of additional mechanical and magnetic parts.

From the publication EP 889 498 A2 a contact system is known with a rotary contact bridge mounted via an elongated hole in a switching shaft, in which a contact force tension spring is arranged on each side of the contact bridge. The tension springs are suspended on both sides in spring bolts, which are guided in recesses of the selector shaft that extend parallel to the elongated hole and act on control cams of the contact bridge arranged in a point-symmetrical manner via rollers. The control curves can be designed in such a way that there is an inhibition of movement of the electrodynamically opening contact bridge. With this contact system, even if the contact pieces' height decreases asymmetrically, which occurs as a result of the erosion or other wear of these contact pieces, there is a compensating displacement of the axis of rotation within the elongated hole. The disadvantage is that if the opposite contact pieces wear unevenly due to the displacement of the contact bridge, the contact force springs engage the rotary contact with different lever arms and thus cause different contact forces between the connected contact pieces. This has the effect that the contact pressure is reduced on the side of the most worn contact pieces and thus self-reinforcing further wear of the contact pieces is caused on this side. Another disadvantage is that the two functions of contact force and movement inhibition cannot be optimized independently of one another.

The object of the invention is therefore in a simplified contact arrangement with improved delay behavior the electrodynamically flung rotary contact bridge.

Starting from a contact arrangement of the type mentioned in the introduction, the object is achieved by the characteristics of the independent Claim solved, while the dependent claims advantageous developments of the invention can be found.

In the case of very high current flows through the contact system as a result of a short circuit in the electrical system to be protected by the circuit breaker, control cams formed on the electrodynamically repelled contact bridge engage in a force-locking operative connection with spring elements mounted in the switching shaft, as a result of which the contact bridge is effectively braked or inhibited in its movement , When the contact bridge falls back towards the switch-on position due to the contact force tension springs and possibly additionally due to the repulsion from an end stop the positive connection described above also inhibits the movement of the contact bridge. This results in a delay of the contact bridge overall in such a way that the contact bridge is prevented from falling back into the switch-on position in good time before the contact arrangement is finally opened by triggering protective devices. The inhibiting function can be influenced in a conventional manner by constructive design and / or dimensioning of the control cams and the spring elements in a variety of ways - for example in the sense that the inhibiting function influences the falling back into the switch-on position more than the transition to the push-off position. The proposed contact arrangement does not require any technologically complex parts to be produced and fastened in order to effect the braking or inhibiting effect mentioned. Circuit breakers equipped with such contact arrangements are advantageously suitable for current-limiting circuit breakers which either switch off themselves in the event of an excessively high current, in particular a short-circuit current, in connection with triggering protective devices or within a switch arrangement from circuit breakers which are selectively staggered with regard to their short-circuit current carrying capacity by another circuit breaker be separated from the short-circuit current. The spring elements are designed as leaf springs, which have one end in the selector shaft, cooperate with the control cams at the free end and are supported with an intermediate area against the selector shaft.

An advantageous inhibitory behavior for the electrodynamically sloughed Contact bridge arises if by means of constructive design customary in the field and / or dimensioning of the control cams and / or the spring elements between Switch-on position and push-off position or in the opposite direction by a maximum of the inhibiting torque the contact bridge to overcome is. With a design and / or dimensioning of the control curves and / or the spring elements can also latched connections between the control cams braked or is inhibited. Falling back the contact bridge in the direction of the switch-on position due to the contact force tension springs and if necessary additionally as a result of the repulsion of one end stop acts the positive connection described above also inhibits the movement of the contact bridge. This will delay the Contact bridge overall achieved in such a way that the contact bridge falls back into the Switch-on position in good time before the contact arrangement is finally opened by triggering Protective organs is prevented. The inhibitory function is more common Way through constructive design and / or dimensioning of the control curves and the spring elements in diverse Sensible influence - for example in the sense that the inhibiting function has a greater influence on falling back into the switch-on position than the transition in the push-off position. The proposed contact arrangement is required to effect the aforementioned Braking or inhibiting effect no technologically complex to produce and parts to be fastened. Equipped with such contact arrangements Circuit breakers are advantageously suitable for current-limiting circuit breakers, when an excessive current occurs, especially a short-circuit current in connection with triggering protective devices either switch off yourself or within a switch arrangement selectively staggered with regard to their short-circuit current carrying capacity Circuit breakers by another circuit breaker from the short circuit current be separated. The spring elements are designed as leaf springs, which have one end in the selector shaft, the free end with the Control curves interact and oppose each other with an intermediate area support the selector shaft.

An advantageous inhibitory behavior for the electrodynamically sloughed Contact bridge arises if by means of constructive design customary in the field and / or dimensioning of the control cams and / or the spring elements between Switch-on position and push-off position or in the opposite direction by a maximum of the inhibiting torque the contact bridge to overcome is. With a design and / or dimensioning of the control curves and / or the spring elements can also snap connections between the control cams and the spring elements at the end of the push-off movement will be realized. As a result, the contact bridge is flung open Reaching their rejection position, until after release the circuit breaker when the Contact arrangement is released from this locking position.

It is expedient for one to be nose-shaped or arc convex formation of the opposing control curves and free ends of the spring elements. That is technologically advantageous common storage of two second spring ends of a pair of tension springs and the bound end of one of the spring members around pins that in turn parallel to the transverse axis in second notches in the selector shaft to store.

The formation of the tension spring pairs takes place as a U-shaped Double tension springs with a connecting piece between the first spring ends of the individual tension springs. Avoiding handrails for hanging the first one Spring ends store the tension springs in a simple manner with the connecting pieces Notches in the contact bridge.

To ensure safe movements of the contact bridge, it is provided with an elongated hole through which a fixed bearing axis running in the transverse axis of the selector shaft is guided. Due to the pole-wise composition of the switching shafts from pole-wise assigned switching shaft segments, the contact arrangement for mo Dularly assembled circuit breakers are suitable.

More details and advantages The invention will become apparent from the following, based on figures explained Embodiment. Show it

1 : an embodiment of the contact arrangement according to the invention shown in perspective in the switched-on position;

2 : a sectional view along the central plane xy according to 1 , wherein the contact arrangement is in the on position;

3 : a sectional view along the central plane xy according to 1 , wherein the contact arrangement is in the push-off position;

4 : a perspective view of a spring element as a detail 1 to 3 ,

The contact arrangement according to the invention 2 according to 1 to 3 is provided for one pole of a multi-pole low-voltage circuit breaker, not shown. The circuit breaker comprises a multi-part insulating housing 4 , a switch lock to be operated by hand or by a motor drive, feeding and outgoing connection elements as well as release devices for overload and short circuit. In the case 4 is a selector shaft around a fixed transverse axis z 6 rotatably supported, the transverse axis z perpendicular to the central plane xy of the pole. The shift shaft 6 is composed of shift shaft segments assigned in poles. The shift shaft 6 has side recesses 8th , engage in the mechanical connection means, not shown, to the driving switch lock. A rotary contact bridge 10 extends along the central plane xy in a playful recording 12 the control shaft 6 and has opposing contact pieces 14 on that outside the shift shaft 6 in the on position with fixed contacts 16 interact. The contact bridge 10 has an elongated hole 11 with which they are on a fixed, in the transverse axis z of the selector shaft 6 extending bearing axis 7 is stored. In the recording 12 are on both sides of the contact bridge 10 or the middle plane xy two tension springs 18 arranged which the required contact force between the contact pieces 14 and the fixed contacts 16 muster.

The tension springs 18 have a on the contact bridge 10 mounted first spring end 21 and one on the shift shaft 6 mounted second spring end 22 on. On each side of the contact bridge 10 are the first spring ends 21 with respect to the point symmetry axis of the contact bridge 10 and the second spring ends 22 of the respective tension springs 18 with respect to the transverse axis z of the selector shaft 6 point symmetrical opposite. The tension springs 18 are arranged symmetrically with respect to the central plane xy. Two first spring ends each on opposite sides of the central plane xy 21 are in one piece over transversal connectors 20 connected, and two second spring ends located on opposite sides of the central plane xy 22 are in transverse pens made of steel 23 hooked. The connectors 20 form with the associated pairs of tension springs 18 U-shaped double tension springs and lie non-positively in the first notches 25 the contact bridge 10 , The steel pins 23 lie in corresponding second notches 27 the control shaft 6 , With each of the two fixed contacts 16 is a loop-shaped connection rail 24 connected. The loop shape causes the contact bridge when a short-circuit current flows 10 through electrodynamic forces against the force of the tension springs 18 from the on position according to 2 towards a push-off position 3 is pushed back. The contact arrangement 2 is still at both ends by in the case 4 specified arc extinguishing units 30 and through from the connecting rails 24 Slotted electromagnetic slot motors isolated 32 completed.

Furthermore, according to the invention are on the contact bridge 10 Point-symmetrically opposite two control curves 34 molded and over the steel pins 23 in the control shaft 6 two spring elements 36 stored. The control curves 34 are on opposite narrow sides of the contact bridge 10 at a short radial distance from the elongated hole 11 nose-shaped. How closer in 4 you can see the spring elements 36 designed as leaf springs. They are arranged in the central plane xy and are cut vertically by their surface. The spring elements 36 are with one end, ie the bound end 38 to the steel pins 23 between the second spring ends 22 of the double tension springs. At the other end, ie the free end 39 , are the spring elements 36 arched and stand with their raised side the control curves 34 in pairs opposite. The intermediate areas 40 between the ends 38 . 39 are opposite on the inner wall of the selector shaft 6 just trained abutments 42 slightly convex.

The control curves arrive at short-circuit currents 34 the electrodynamically repelled contact bridge 10 in operative connection with the free ends 39 the spring elements 36 , The one with its tied ends 38 in the control shaft 6 stored spring elements 36 support each other with their intermediate areas 40 against the abutments 42 in the selector shaft. The one between the free ends 39 and the control curves 34 transmitted spring forces and occurring frictional forces act on the rest of the contact bridge 10 acting acceleration forces. At the transition of the contact bridge 10 from the in 2 shown switch-on position in the 3 repulsion position shown, these acceleration forces are caused by the electrodynamic repulsive forces that there with the contact pressure forces of the tension springs 18 counteracting. When the contact bridge falls back 10 from the in 3 shown repulsion position towards the on position 2 call the contact pressure forces of the tension springs 18 and if necessary, that by breaking the contact bridge 10 against the housing 4 be recoil impulse the said acceleration forces, which counteract any existing electrodynamic repulsive forces. In both directions, the interaction of the control curves 34 with the spring elements 36 a motion-inhibiting torque on the contact bridge 10 exercised. This torque is determined in detail by the structural shape, arrangement and material design of the control cams and spring elements and is adapted in a customary manner to the requirements. The adaptation can be done, for example, with the purpose that the inhibiting torque at the transition of the contact bridge 10 passes through a maximum from the switch-on to the switch-off position.

In the contact system described above 2 becomes the falling back of the repelled contact bridge 10 delayed until the safe switch-off via the triggered switch lock. Another possibility is that the control curves 34 are designed in such a way that they reach the spring elements after reaching the push-off position 36 enter into a latching connection. When the circuit breaker is switched off by the subsequent triggering process, the control shaft 6 after the representation of 3 moved clockwise, passing through the stop of the contact bridge 10 on the housing 4 the locking connections between the control curves 34 and the spring elements 36 be solved again.

Claims (9)

Contact arrangement for at least single-pole, current-limiting circuit breakers in the low-voltage range with an insulating housing ( 4 ), comprehensive - one in an insulating housing ( 4 ) shift shaft rotatably mounted about a fixed transverse axis (z) ( 6 ), - a rotary contact bridge ( 10 ), which are in a game-laden recording ( 12 ) the selector shaft ( 6 ) extends along the median plane (xy) of the pole and both contacts ( 14 ), which in the switch-on position with fixed contacts ( 16 ) interact as well as control curves ( 34 ), - two inside the selector shaft ( 6 ) arranged pairs of each on opposite sides of the contact bridge ( 10 ) existing contact force tension springs ( 18 ) with at the contact bridge ( 10 ) specified first spring ends ( 21 ) and on the selector shaft ( 6 ) specified second spring ends ( 22 ), with on each side of the contact bridge ( 10 ) the first spring ends ( 21 ) and the second spring ends ( 22 ) face each other symmetrically, and - two each with one of the fixed contacts ( 16 ) connected connecting rails ( 24 ) which, at very high currents, causes an electrodynamic transition of the contact bridge ( 10 ) from the switch-on position to a push-off position, characterized in that in the selector shaft ( 6 ) point symmetrical to the transverse axis (z) additional spring elements designed as leaf springs ( 36 ) are arranged in the area of the central plane (xy), each with a bound end ( 38 ) in the selector shaft (6), - with an intermediate area ( 40 ) against an abutment ( 42 ) in the selector shaft ( 6 ) support and - in the area of a free end ( 39 ) over the control curves extending along the central plane (xy) ( 34 ) with electrodymanic repulsion in a movement-inhibiting connection with the contact bridge ( 10 ) to step. Contact arrangement according to the preceding claim, characterized in that between the switch-on position and the repulsion position or vice versa, a maximum braking torque between the spring elements ( 36 ) and the contact bridge ( 10 ) occurs. Contact arrangement according to one of the preceding claims, characterized in that the control cams ( 34 ) and the spring elements ( 36 ) are designed in such a way that they enter into a releasable locking connection after reaching the push-off position. Contact arrangement according to one of the preceding claims, characterized in that the control cams ( 34 ) nose-shaped and the free ends ( 39 ) compared to the control curves ( 34 ) are convexly curved. Contact arrangement according to one of the preceding claims, characterized in that the second spring ends ( 22 ) of said pairs of tension springs ( 18 ) and the bound ends ( 38 ) the spring elements ( 34 ) around pens ( 23 ), which in turn parallel to the transverse axis (z) in second notches ( 27 ) in the selector shaft ( 6 ) to store. Contact arrangement according to one of the preceding claims, characterized in that the first spring ends ( 21 ) of said pairs of tension springs ( 18 ) via connecting pieces running parallel to the transverse axis (z) 20 ) are integrally connected. Contact arrangement according to the above An saying, characterized in that the connecting pieces ( 20 ) in first notches ( 25 ) at the contact bridge ( 10 ) to store. Contact arrangement according to one of the preceding claims, characterized in that the contact bridge ( 10 ) with an elongated hole ( 11 ) on a fixed, in the transverse axis (z) of the selector shaft ( 6 ) running bearing axis ( 7 ) is stored. Contact arrangement according to one of the preceding claims, characterized in that the switching shaft ( 6 ) consists of switching shaft segments assigned in poles.