EP0813218A2 - Trip device for overload circuit breaker - Google Patents

Abstract

The device has a release-armature (1) which actuates a switch lock (20). The armature (1) is actuated by a coil (3) through which the current to be monitored flows. The armature (1) is actuated by a magnetic armature (5) which is moved directly by the coil (3). The magnetic armature (5) is connected to the trigger armature (1) by means of at least on elastic coupling member (4) and preferably one or more auxiliary armatures (11). The trigger armature (1) is held in its rest position with a predetermined holding force, which is preferably a force generated in a mechanical manner. The force may be e.g. a friction force which can be generated by components in contact with the trigger armature (1) e.g. a snap spring.

Description

The invention relates to a tripping device for an overcurrent shutdown device, such as Miniature circuit breaker, comprising a trigger armature which actuates a switch lock and which can be actuated by a coil through which a current to be monitored flows. Fuses are essentially used on overcurrent switch-off devices - they can only be used for a single switch-off process - and on the other hand reusable circuit breakers that can therefore be used several times are used.

In an electrical system, an overload protection of the above-mentioned designs is normally provided in the supply line before this supply line is divided into a plurality of circuits connected in parallel with one another. Each of these circuits has its own protective devices - usually consisting of personal protection (RCCBs or the like) and system protection (circuit breakers, fuses or the like). If necessary, these circuits can in turn be subdivided into further sub-circuits that are also protected by protective devices.

Such a circuit structure results in a series connection of the protective devices of the feed line, circuit and sub-circuit.

If an impermissibly high current now occurs in a sub-circuit, it is desirable if only the circuit breaker assigned to this sub-circuit trips and thus disconnects its sub-circuit from the mains, but all upstream circuit breakers are switched on and thus all fault-free circuits and sub -Circuits remain connected to the network. Only when the overcurrent occurring is so great that it can no longer be switched off by the circuit breaker of the sub-circuit, should the higher-level switch respond. Such a time-delayed switching of the upstream switch is referred to as "selectivity".

In the case of fuses, this selectivity is determined by the heating power required for melting the fuse wire, which is proportional to the square of the current and the duration of the overcurrent.

In the field of miniature circuit breakers, two tripping devices are usually provided. A first device is provided for switching off overcurrents which are only slightly above the nominal system current and act over longer periods of time. The second, so-called short-circuit current triggering is usually implemented by a coil through which the current to be monitored flows and with a movable armature which effects the shutdown. In order to simulate the heating output and thus the current and time-dependent delay explained in connection with the fuses, thermal bimetal strips through which the current to be monitored flow are used, which bimetal strips deform in a manner analogous to the fuse wires in proportion to the square of the current and the time and by this deformation enable the switching action of the short-circuit current release with a time delay.

These bimetallic strips are components that on the one hand have to be mechanically adjusted precisely and on the other hand require additional electrical connections. In summary they bring with it a significant complication of the circuit breaker structure and thus a deterioration in the functional reliability and a more complicated manufacture. The object of the invention is to provide a triggering device of the type mentioned at the outset which has a selective triggering behavior, but for which it has only a few, insensitive and easy-to-install components to be added to the conventional triggering coil.

Further objects of the invention are to provide the simplest possible ways of generating said holding force, possibilities for adjusting the selectivity, and functionally reliable design examples of the triggering device according to the invention that can be implemented in practice. This is achieved by the measures listed in the subclaims.

With a tripping device for an overcurrent shutdown device, such as Miniature circuit breakers, comprising a tripping armature that actuates a switch lock and can be actuated by a coil through which a current to be monitored flows, the object is achieved according to the invention in that the tripping armature indirectly by means of at least one elastic coupling element and optionally one or more auxiliary anchors connected to the trigger armature, directly movable from the coil magnetic armature and that the trigger armature is held in its rest position with a predetermined holding force.

It is thus possible to delay the switching action by means of electromechanical measures or arrangements, which is considerably more functionally negligible than electrothermal-mechanical solutions.

According to a first variant of the invention it can be provided that the holding force is a force generated mechanically, which leads to a robust and compact design of the triggering device according to the invention.

In this connection it can be provided that the holding force is a static friction force which can be generated by components in contact with the release armature. The holding force can be adjusted particularly easily by changing the contact pressure exerted by the components on the release armature.

According to another embodiment of the invention, it can be provided that the holding force by resilient components acting on the release armature, such as e.g. a snap spring can be generated.

Relatively large holding forces and thus severe time delays can thus be implemented in a simple manner.

According to a preferred embodiment of the invention it can be provided that the holding force is a magnetic force generated by at least one permanent or electromagnet acting on the release armature.

Such systems have relatively precisely predictable magnetic properties which are constant with respect to environmental influences, so that the triggering devices provided with them have almost constant time delays over their service life.

It can be advantageous that the holding force acting on the release armature can be changed, because the time delay of the release process can thus be changed and with a switching device provided according to the invention can be adjusted to the protective devices connected downstream of it.

In this context, it can be particularly advantageous if it is provided that the holding force can be changed depending on the strength of the current to be monitored. An adaptive behavior of the triggering device can thus be implemented; depending on the size of the short-circuit current, the relative switch-off delay increases automatically.

In a further development of the invention it can be provided that the holding force can be generated by an electromagnet which is flowed through by a current which is directly proportional to the current to be monitored.

This allows a particularly simple and functionally reliable implementation of the current-dependent holding force change described above.

Another feature of the invention can be that the at least one elastic coupling member is formed by a helical spring, because such components require little space, but at the same time have good and constant elasticity.

According to a particularly preferred embodiment of the invention it can be provided that the magnetic armature is arranged at least in sections inside the coil. The magnetic armature can thus be moved in a precisely predictable manner by the magnetic forces of the current to be monitored.

In a further development of the above preferred embodiment it can be provided that the trigger armature is also arranged inside the coil, the trigger armature being formed from non-magnetizable material.

This results in a relatively compact size of the triggering device.

Furthermore, it can be provided that the magnet armature is designed as a tube piece closed on one side and that the trigger armature and the at least one coupling member are at least partially arranged within the cavity formed by the magnet armature. This allows a further geometric downsizing of the triggering device according to the invention, it is essentially only dependent on the size of the coil, outside of which there are no more moving components.

In a further embodiment of the invention, it can be provided that the release armature has a shoulder which extends through the magnet armature and preferably runs parallel to the longitudinal axis of the coil and on which shoulder the holding force acts.

Thus, the components introducing the holding force can be arranged outside the coil, so that they in no way hinder the freedom of movement of the components arranged inside the coil.

• Fig.1 eine schematische Schnitt-Darstellung einer erfindungsgemäßen Auslöse-Einrichtung im Aufriß;
• Fig.2 die Auslöse-Einrichtung nach Fig. 1 mit einem zusätzlichen Hilfsanker;
• Fig.3a,b die Auslöse-Einrichtung nach Fig.1 mit Bauteilen zur mechanischen Aufbringung der Haltekraft;
• Fig.4 eine mögliche konkrete Ausführung der Erfindung im Aufriß im Schnitt;
• Fig.5 eine andere mögliche Ausführung der erfindungsgemäßen Auslöse-Einrichtung im Aufriß im Schnitt und
• Fig.6 die Ausführung nach Fig.5 ergänzt um zwei mögliche Varianten der elektrischen Beschaltung der Auslöse-Einrichtung.

The invention is explained below with reference to the accompanying drawings. Show:

• 1 shows a schematic sectional view of a release device according to the invention in elevation;
• 2 shows the release device according to FIG. 1 with an additional auxiliary anchor;
• 3a, b the release device according to Fig.1 with components for mechanical application of the holding force;
• 4 shows a possible concrete embodiment of the invention in elevation on average;
• 5 shows another possible embodiment of the release device according to the invention in elevation on average and
• 6 shows the embodiment according to FIG. 5 supplemented by two possible variants of the electrical wiring of the triggering device.

The trigger device shown in Fig. 1 for an overcurrent shutdown device, such as Circuit breaker, has a magnet armature 5 consisting of a magnetizable material such as iron, which magnet armature 5 is directly movable by a coil 3. The current flowing through the coil 3 is the current to be monitored and, if necessary, to be switched off. Furthermore, a tripping armature 1 is provided which can actuate a switch lock 20, which switch lock 20 opens the contacts 21 through which the current to be monitored flows. As shown in the drawing, this actuation can take place via a release pin 2 molded onto the release anchor 1, but alternatively can also be carried out directly from the release anchor 1 itself.

Trigger armature 1 and magnet armature 5 are mechanically connected to one another by an elastic coupling member 4, which in the simplest case is formed by a helical spring. The trigger armature 1 is not freely movable, but is held in its rest position with a predeterminable holding force F _H. In order to be able to bring the trigger armature 1 back into its rest position after the triggering has taken place, a return spring 6 is provided, which is supported on the one hand on the trigger armature 1 and on the other hand on a housing part 7, shown only symbolically.

With this arrangement, a time-delayed tripping is achieved when an inadmissibly high overcurrent to be switched off occurs.

Said tripping can be divided into two tripping phases, which are described below. In a first tripping phase immediately following the occurrence of the overcurrent, the overcurrent generates a magnetic field proportional to its strength via the coil 3, which moves the magnet armature 5 in the direction of the tripping armature 1. This movement is transmitted via the elastic coupling member 4 to the release armature 1, which, however, temporarily remains in its rest position due to the holding force F _H acting on it. As the deflection of the magnetic armature 5 continues, the coupling member 4 is increasingly biased, as a result of which the force acting on the release armature 1 increases. In this tripping phase, magnet armature 5 and coupling element 4 represent an oscillation system which is excited by the magnetic force generated by the overcurrent. The time required for the magnetic armature 5 to pretension the coupling member until the holding force F _{H is} exceeded and the trigger armature 1 can be deflected from its rest position results in the time delay and the selectivity of the triggering device according to the invention.

If the force generated by the overcurrent exceeds the holding force F _H , the second tripping phase occurs. The tripping armature 1 suddenly starts moving, as a result of which the switching lock 20 is actuated and the contacts 21 of the overcurrent protection device are subsequently opened. In this tripping phase, the now coupled masses of magnet 5 and tripping armature 1, in cooperation with the return spring 6, represent the vibration system. This functions like a conventional magnetic trigger, which is formed solely from a coil and armature, the excitation force resulting from the result of the force system Current force holding force F _H results.

In summary, the triggering is therefore not initiated by an armature that is actuated directly by the overcurrent, but takes place indirectly by the movement of the magnetic armature 5 that is directly movable by the coil 3 and that is connected to the trigger armature 1 by means of the elastic coupling element 4.

The time delay for triggering is essentially created in the first trigger phase. It is determined by the mechanical properties of the vibration system - magnet armature mass, spring rate of the coupling member 4 and magnet armature stroke - and by the current force. As is known, the current force is proportional to the current square, and consequently also the movement of the magnet armature 5. The delay is therefore also proportional to the current square, just as in the known, electrothermally functioning delay devices mentioned at the beginning.

Although this would complicate the construction of the triggering device according to the invention, it is also conceivable, as shown in FIG. 2, to arrange a — optionally also several — auxiliary armature 11 between the magnet 5 and the trigger armature 1. These auxiliary anchors 11 are mechanically connected to one another via further elastic coupling members 40 and are subjected to holding forces F _H in their rest positions analogous to the release anchor 1. Such a mechanical series connection of several armatures results in an addition of their holding forces F _H and an increase in the deflection path to be traveled by the magnet armature 5 and thus in an extension of the delay time.

The described holding forces F _H can in principle be generated in any way. 3a and 3b show examples of the generation of the holding force by mechanical means. According to FIG. 3a, the holding force F _{H is} a static friction force which is generated by components 8 which are in contact with the release armature 1 and which clamp the release armature 1 between them.

The alternative according to FIG. 3b provides for the holding force F _{H to be} generated by resilient components 9, such as a snap spring, acting on the release armature 1. This snap spring 9 is designed as a leaf spring clamped on both sides and biased against the direction of movement of the release armature 1. If the force acting on it is large enough, it bends against its pretensioning direction and thus allows the release armature 1 to move.

A type of holding force formation that is contrary to these mechanical solutions is that the holding force F _{H is} a magnetic force generated by at least one permanent or electromagnet acting on the release armature 1. Examples are 4, 5 and 6. These drawings represent variant embodiments of the invention that can be used in practice.

Here, the coil 3 is arranged on a non-magnetic winding body 10, the magnetic armature 5 being arranged in sections inside the coil 3. Furthermore, a yoke 23 made of magnetizable material is provided, which for the most part extends outside the coil 3 and has an extension 24 which projects into the coil 3 at the end of the coil 3 closer to the switching mechanism 20. The magnetic field generated by a coil current closes via the yoke 23, the magnet armature 5, the working air gap a and the yoke attachment 24.

This structure corresponds to the conventional, common version of a magnetic release. The trigger armature 1 is also arranged in the interior of the coil 3, but must be made of non-magnetizable material, such as e.g. Aluminum or plastic may be formed so that it is not moved by the magnetic forces generated by the coil 3.

The magnet armature 5 is designed as a tube piece closed on one side, the release armature 1 and the coupling member 4 being arranged within the cavity formed by the magnet armature 5.

The trigger armature 1 has a trigger pin 2 extending from the coil 3 and can be brought into its rest position by a return spring 6 analogously to the illustration according to FIG.

In order to be able to have the holding force act on the release armature 1, this has an extension 12 which extends through the magnet armature 5 and preferably runs parallel to the longitudinal axis of the coil 3. This has freely accessible and therefore loadable sections.

The approach 12 is not mandatory, in the sense of the invention it is also possible to let the holding forces F _{H act} directly on the release armature 1. For this purpose, however, the components required for this would have to be arranged in the interior of the coil 3 and, if necessary, recesses should be provided for them in the magnet armature 5 so that its freedom of movement is not hindered.

As already indicated, the holding force F _{H is} generated magnetically in this exemplary embodiment, specifically by means of a permanent magnet 13. For this purpose, an anchor 26 is fixed at the upper end of the extension 12. Together with the yoke 25, which according to FIG. 4 also serves as a mechanical holder for the permanent magnet 13, and the permanent magnet 13, the armature 26 forms a magnetic circuit for the magnetic field generated by the permanent magnet 13. Due to the resulting holding forces between the armature 26 and the yoke 25, the tripping armature 1 is held in the rest position shown.

In said magnetic circuit - formed from armature 26, yoke 25 and permanent magnet 13 - there are air gaps 27 between armature 26 and yoke 25 and an air gap 28 between permanent magnet 13 and armature 26. The resulting holding forces F _H can be changed by changing the size of these air gaps 27, 28 can be changed. Said air gap change can be made, for example, by choosing the height of the permanent magnet 13, through inserts of different thicknesses arranged between the yoke 25 and the armature 27 non-magnetizable material, by changing the length of the yoke legs or similar measures.

When a short-circuit current occurs, the strength of the magnetic field prevailing in the working air gap a between the magnet armature 5 and the yoke attachment 24 increases, and thereby the attraction forces acting between the magnet armature 5 and the attachment 24, as a result of which the magnet armature 5 moves in the direction of the attachment 24. After the trigger armature 1 is still stationary, the distance d between the magnet armature 5 and the trigger armature 1 is reduced, the spring 4 being compressed. As soon as the forces transmitted to the release armature 1 via the spring 4 exceed the holding force F _{H of} the permanent magnet 13, the release armature 1 is also set in motion and, as a result, the switch 20 is triggered.

If the entire distance d from the magnet armature 5 is passed without a movement of the trigger armature 1 having been achieved, the magnet armature 5 strikes the trigger armature 1 and takes it along in its further downward movement. This knocking results in a shock process in which the magnetic armature 5 is deprived of kinetic energy, which in turn delays the switching action and thus contributes to the selective shutdown behavior of the arrangement.

The dimensioning of the distances a, b, c, d is important for the correct functioning of the arrangement described. In particular, the distance d between the magnet 5 and the tripping armature 1 must be smaller than the distance a between the magnet armature 5 and the yoke attachment 24, so that it is ensured that at the end of the possible path of movement of the magnet armature 5 it meets the yoke attachment 24 on the release armature 1 has actuated the switch lock 20. In this context, it is necessary that the path of movement of the release armature b is long enough to actuate the switching mechanism 20. Furthermore, it must be excluded that the armature 26 strikes the winding body 10 during the movement of the trigger armature 1 and thus holds the trigger armature 1 in place. This is achieved in that the distance c is larger than distance b.

In summary, the following relationships can be given for the ratios of the distances a, b, c, d: a> b and a> d, and c> b.

The particularly preferred exemplary embodiment according to FIG. 5 largely corresponds to that of FIG. 4, but here the permanent magnet 13 is replaced by an electromagnet formed from winding 15 and yoke 25. As above, an armature 26 is provided which is connected to the projection 12 and which forms a magnetic circuit with the yoke 25. A separate component 14 is provided for the mechanical mounting of the electromagnet. For the dimensioning of the distances, what has been said in the course of the description of FIG. 4 applies.

The change in the holding force F _H can also take place here again by adjusting the lengths of the air gaps 27, 28. It is particularly expedient not to provide the air gaps 27, that is to say to leave the armature 26 on the yoke 25 and to make the section 25 ′ of the yoke 25 running inside the winding 15 displaceable in the longitudinal direction of the winding 15. The holding force F _H can thus be adjusted mechanically.

In addition to this mechanical changeability, the holding force F _{H can} also be changed by changing the current flowing through the winding 15. The variability of the holding force F _H is in no way limited to a magnetic force generation. The components 8 indicated in FIG. 3a can also be arranged displaceably, as a result of which the contact pressure on the release armature 1 and thus the holding force F _H can be changed.

It is particularly favorable if the holding force F _{H can be changed} as a function of the strength of the current to be monitored. In the construction variant according to FIG. 5, this can be implemented particularly simply in that the current flowing through the winding 15 is directly proportional to the current to be monitored.

In order to have the lowest possible circuit complexity, the proportionality mentioned is most easily achieved in that the overcurrent itself flows through the winding 15 of the electromagnet. For this purpose, as shown in FIG. 6 with solid connecting lines 16, 17, the coil 3 and the winding 15 are connected in series with one another. For the same purpose, however, coil 3 and winding 15 could also be connected in parallel - cf. Dashed connecting lines 18, 19; 15 series impedances can be switched in the branch of the winding in order to adjust the current flowing through the winding 15 and thus the holding force F _H generated.

Although this would entail a relatively high additional outlay, it is also possible in the sense of the invention to apply a current electrically isolated from the winding 15 to the winding 15 and, if necessary, to change this proportionally by means of corresponding control circuits by 7 .mu.m overcurrent

A preferred area of application of the tripping device according to the invention described is in use in circuit breakers, which should not, however, preclude use in other devices which cut off overcurrent.

Claims (14)

Tripping device for an overcurrent switch-off device, such as a circuit breaker, comprising a tripping armature (1) which actuates a switch lock (20) and can be actuated by a coil (3) through which a current to be monitored flows, characterized in that the tripping -Anchor (1) can be actuated indirectly by means of at least one elastic coupling member (4) and optionally one or more auxiliary anchors (11) connected to the release armature (1) and directly movable by the coil (3) magnetic armature (5) and that the trigger armature (1) is held in its rest position with a predeterminable holding force (F _H ). Tripping device according to claim 1, characterized in that the holding force (F _H ) is a force generated mechanically. Release device according to claim 2, characterized in that the holding force (F _H ) is a static friction force which can be generated by components (8) in contact with the release armature (1). Tripping device according to claim 2, characterized in that the holding force (F _H ) can be generated by resilient components (9) acting on the tripping armature (1), such as a snap spring. Tripping device according to claim 1, characterized in that the holding force (F _H ) is a magnetic force generated by at least one permanent or electromagnet (13; 14, 25) acting on the tripping armature (1). Tripping device according to one of claims 1 to 5, characterized in that the holding force (F _H ) acting on the tripping armature (1) can be changed. Tripping device according to claim 6, characterized in that the holding force (F _H ) can be changed as a function of the strength of the current to be monitored. Tripping device according to Claim 7, characterized in that the holding force (F _H ) can be generated by an electromagnet which is flowed through by a current which is directly proportional to the current to be monitored. Tripping device according to one of claims 1 to 8, characterized in that the at least one elastic coupling member (4) is formed by a helical spring. Tripping device according to one of claims 1 to 9, characterized in that the magnetic armature (5) is arranged at least in sections inside the coil (3). Tripping device according to claim 10, characterized in that the tripping armature (1) is also arranged in the interior of the coil, the tripping armature (1) being formed from non-magnetizable material. Tripping device according to claim 11, characterized in that the magnet armature (5) is designed as a tube piece closed on one side and that the tripping armature (1) and the at least one coupling member (4) are at least partially inside the magnet armature ( 5) formed cavity are arranged. Tripping device according to claim 10, 11 or 12, characterized in that the tripping armature (1) has a shoulder (12) which extends through the magnet armature (5) and preferably runs parallel to the longitudinal axis of the coil (3) which approach (12) acts the holding force (F _H ). Use of a tripping device according to one of the preceding claims as a short-circuit current tripping device in a circuit breaker.

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