EP2864995B1 - Switching device with electromagnetic latching mechanism - Google Patents

Description

The invention relates to a switching device according to the preamble of claim 1. The invention relates in particular to a remotely operable motor output with switching and protective function, in particular to an integrated solution that both the operational switching at normal load and the switching off in overload or short circuit using a device.

Conventional switching devices of this type are usually equipped with two drives, one of which is provided for the operational switching and the shutdown in case of overload, while the other drive is used for rapid shutdown in the event of a short circuit. For operational switching and off in case of overload in particular an electromagnetic reluctance drive is provided. For rapid shutdown in case of short circuit, however, serves a mechanical switch lock, which is provided with one or more springs as energy storage. The maximum permissible switch-off times in the event of a short circuit, which are typically set at 5 ms today, must be observed only with such a switch lock.

Disadvantageously, the presence of two drives in a conventional compact feeder leads to a comparatively large space of the switching device and large mass and high production costs. In particular, an additional magnetic release is needed to trigger the switching mechanism. Another disadvantage is that the mechanical switch lock after triggering manually and directly on the device must be tightened. The switching device can thus not be reset to the operating state by remote maintenance after the rapid shutdown. Although it is in principle possible to provide for the tensioning of such a switching mechanism another drive (eg a stepper motor with gear). However, this would disadvantageously further increase the manufacturing costs, the mass and the installation space of such a switch.

A circuit breaker according to the preamble of claim 1 is DE 103 39 214 B4 known. However, this document does not disclose means for rapid shutdown in the event of a short circuit.

Out EP 0 483 591 A2 a low-voltage switching device is known which comprises a single- or multi-pole contact system with a corresponding number of fixed contacts and movable contacts. The movable contacts are movable by means of a magnet armature. The low-voltage device has at least one magnetic coil and a desired switching trigger, wherein the magnet armature operates bistable. Furthermore, the low-voltage switching device is provided with an overcurrent protection circuit, which causes an overcurrent above a limit overcurrent to at least one switched pole after one with a minimum possible time delay, a DC excitation of the solenoid.

WO 2007/079767 A1 discloses a method of operating a switching device comprising at least one electromagnetic drive. The electromagnetic drive in this case has a movable armature which is designed to open and close at least one main contact of the switching device. The electromagnetic drive includes an excitation coil adapted to generate a magnetic field that causes movement of an armature. The armature is further provided at one end with a return spring which exerts a force on the armature.

Out GB 2 350 724 A For example, a solenoid actuator is known that includes two solenoids that are capable of moving an armature between an open and a closed position. The armature can by magnetic forces, which exerts a permanent magnet on the armature, in operation at the attacks of his Stroke be held so that the Magnetaktuator is bistable as a whole.

The invention has for its object to provide a switching device that allows both the operational switching on and off, as well as the shutdown in case of overload and the emergency shutdown in the event of short circuit, but at the same time is particularly simple and compact feasible. Desirable characteristics of the specified switching device further consist in that the rapid shutdown should be vornehmbar in the event of a short circuit by an electrical signal that the switching device should be reset automatically or by remote action in the operating state after the rapid shutdown, and that the switching device "failsave" (ie also error operate safely) should be.

The above object is achieved by the features of claim 1. The switching device according to the invention therefore has a main contact system, an electromagnetic drive unit and a coupling member. The main contact system is used for reversible closing and disconnecting a current path and for this purpose comprises at least one fixed contact and at least one associated moving contact, wherein the moving contact between two switching positions, namely a closed position and an open position relative to the fixed contact is movable. Preferably, the main contact system in per se conventional design two via a jumper together firmly connected moving contacts, each moving contact with an associated fixed contact corresponds and wherein the moving contacts can be brought together and simultaneously with the associated fixed contacts in plant and lifted from them. The switching device can also be within the scope of the invention also be designed multipolar. The main contact system may accordingly have a plurality of fixed contacts and moving contacts provided for simultaneously closing or disconnecting the current paths.

The electromagnetic drive unit is a bipolar magnet system whose magnetic circuit comprises both one or more permanent magnets and magnet coils. Concretely, the drive unit has a movable armature and a first fixed magnetic coil and a second stationary magnetic coil. By energizing the magnetic coils, the armature can be reversibly moved between two anchor layers, wherein the armature is stabilized in each of the two anchor positions by the one or more permanent magnets of the bipolar magnet system. Thus, the drive unit is a bistable magnet system.

Finally, the coupling member serves to transmit a control force from the drive unit to the moving contact. The coupling member is for this purpose movable between an operating position and a release position, wherein the operating position of the coupling member corresponds to the closed position of the moving contact, and the release position of the coupling member with the open position of the moving contact. In other words, the coupling member is in the closed (applied to the fixed contact) moving contact regularly in its operating position and open (lifted from the fixed contact) moving contact in the release position. The coupling member is connected in an expedient embodiment of the invention, in particular fixed to the armature of the drive system and linearly displaceable together with this between the operating position and the release position. In this case, the coupling member is designed in particular as a plunger.

According to the invention, the main contact system, the drive unit and the coupling element are in operative relationship such that the moving contact is de-energized (ie at least substantially de-energized) magnetic coils - in spite of the bistable ones Design of the drive unit - monostable held in the open position. Thus, the moving contact also returns from any other contact position back to the open position, if and as long as the solenoid coils are de-energized.

According to the switching device is further designed such that by selective excitation of the first magnetic coil, the moving contact is movable into the closed position. In other words, the current path is closed as intended by the fact that the first magnetic coil is energized (ie, energized), while the second magnetic coil is de-energized or left in a de-energized state. This switching function corresponds essentially to the functioning of a contactor. The first magnetic coil used to close the main contact system is therefore also referred to below as a "contactor coil".

By contrast, the second magnetic coil serves to rapidly shut down the switching device in the event of a short circuit in the current path. Accordingly, the switching device is designed such that by selective energization (ie energization) of the second solenoid, the moving contact within a permissible for a short circuit in the current path Maximalausschaltzeit in the open position is movable, so that the current flow is interrupted in the current path. The said maximum switch-off time is in particular 5 ms. The second solenoid coil used for the quick shutdown is also referred to below as the "short-circuit release coil".

To support the above-described operative relationship between the main contact system, the drive unit and the coupling member, the switching device in a preferred embodiment additionally comprises at least one contact spring which biases the moving contact in the direction of one of its two switching positions. In alternative embodiments of the invention, the moving contact can be biased by the contact spring either in the manner of a circuit breaker by the contact springs in the direction of its closed position or in the manner of a Contactor be biased towards the open position.

In addition or as an alternative to the contact spring, the switching device preferably has at least one return spring, which biases the coupling member in the direction of the release position.

In embodiments of the switching device containing the contact spring (s) and the return spring (s), the monostable bearing of the moving contact is achieved in particular by the interaction of the contact spring (s), return spring (s) and the drive unit to the moving contact forces exerted.

The switching device according to the invention has the particular advantage that both the operational switching and the overload shutdown and the quick shutdown occurs in the event of a short circuit by means of a single electromagnetic drive, which allows a compact, lightweight and efficient production of the switching device. Another advantage of the switching device is that it goes in case of failure by itself in the off state, from which it can be switched on again electrically without further action. In particular, no manual reset operations are required after a quick circuit in the event of a short circuit. The high switching speed, which is required for the rapid shutdown in the event of a short circuit, is largely supported by the fact that the switching device automatically strives for this in the off state due to the monostability of the open position.

The high shutdown speed is also supported by the optionally existing return spring (s) and optionally by the optional contact spring (s).

The switching device is preferably an electronic switching device, i. to a switching device with an electronic control and electronic power monitoring, in particular an electronic trigger detection in case of overload and short circuit. Accordingly, the switching device comprises an electronic control circuit for controlling the first magnetic coil and / or the second magnetic coil.

In order to limit the holding force of the drive unit with closed switching device as possible to a required minimum size and thus to keep the power consumption of the switching device low, the control circuit is preferably adapted to teilzuerregen after closing the switching device, the first solenoid coil by a clocked holding current (ie to comparatively low level to excite), so that the moving contact - especially just safe - is held in the closed position. The clocked partial excitation takes the control circuit in this case in particular by a pulse width modulation of the voltage applied to the contactor coil operating voltage.

Furthermore, the control circuit is preferably configured to further reduce the turn-off time in the event of a short circuit by means of circuitry measures. For this purpose, the control circuit comprises in a preferred embodiment, a de-energizing circuit which ensures in case of a short circuit in the current path an accelerated de-energizing - to be switched off in this case - contactor coil. The excitation circuit comprises in a simple and effective embodiment, in particular as a substantial part of a Zener diode and a freewheeling diode connected in series thereto, over which the contactor coil is bridged after switching off.

Likewise for further acceleration of the quick shutdown in the event of a short circuit, the control circuit preferably comprises an electrical energy store, in particular a capacitor, via which the short-circuit release coil can be excited quickly and effectively in the event of a short circuit in the current path. The energy storage device is in turn charged in normal operation of the switching device, so that its performance in case of short circuit is available immediately and in full.

In terms of effective operation of the switching device, the short-circuit release coil is used exclusively for the rapid shutdown in the event of a short circuit, but not for the operational shutdown of the current path or the overload shutdown. In the latter cases, preferably only the contactor coil is deenergized (turned off) by the control circuit while leaving the short-circuit release coil deenergized. The moving contact in this case returns automatically, possibly supported by the return spring (s) and / or the contact spring (s) in the monostable open position.

As a further measure for accelerating the quick shutdown in the event of a short circuit, the coupling element in its operating position is preferably in a state decoupled from the moving contact. In particular, the coupling member is arranged in its operating position with a certain distance to the moving contact and the associated parts. By this decoupling of the coupling member of the moving contact is achieved that the coupling member is accelerated at a short circuit in the current path - and corresponding excitation of the Kurzschlussauslöserspule - initially without physical contact to the moving contact, so that the coupling element already indirectly with a non-zero pulse immediately encounters the moving contact. The moving contact is thereby accelerated particularly fast by the coupling member, which favors the collapse of the current flow in the current path.

As a safety measure, furthermore, at least one of the two magnetic coils is expediently also in a de-energized state not completely energized. Rather, the contactor coil and / or the short-circuit release coil are also applied in a de-energized state with a low quiescent current. The monitoring of the quiescent current, which is chosen so low that it does not significantly affect the force relationships in the drive kinematics, allows a conclusion on the functionality of the solenoid coils. In particular, a possible line break in one of the magnetic coils is detected early on the basis of the quiescent current, which likewise collapses in this case, by the control circuit.

The permanent magnets of the bipolar magnetic drive system are preferably arranged stationarily on a yoke of the magnet system. In principle, however, they could also be mounted on the movable armature within the scope of the invention.

• dass in entregtem Zustand der Magnetspulen das Kräftegleichgewicht aus Permanentmagneten, Kontaktfeder(n) und Rückdruckfeder(n) das Hauptkontaktsystem offenhält und für jeden Zustand, den die Komponenten des Schaltgeräts im Rahmen der Konstruktion einnehmen können, das Öffnen statisch sicher erzwingt,
• dass das betriebsmäßige Schließen des Hauptkontaktsystems durch Erregung der Schützspule erfolgt,
• dass das betriebsmäßige Geschlossenhalten des Hauptkontaktsystems durch getaktete Erregung der Schützspule erfolgt,
• dass ein betriebsmäßiges Öffnen des Hauptkontaktsystems durch Entregung (d.h. Abschalten der Spannung an) der Schützspule erfolgt,
• dass die Schnellabschaltung im Kurzschlussfall durch Abschalten der Spannung an der Schützspule und Erregung der Kurzschlussauslösespule realisiert wird,
• dass die Kurzschlussauslöserspule in diesem Fall aus einer separaten Energiequelle, beispielsweise einem Kondensator erregt wird, und
• dass im Kurzschlussfall die Schützspule mittels einer elektronischen Entregungsschaltung schnell entregt wird.

In a particularly preferred embodiment of the invention, the switching device is characterized in particular by a bipolar, bistable electromagnetic drive unit with two stationary magnetic coils (namely a contactor coil and a short-circuit release coil), stationary permanent magnets and a moving armature. Furthermore, the switching device comprises an electronic assembly for controlling the bipolar magnet system. The switch further comprises a main contact system, which is kept closed by contact springs either without interaction with the drive as in a typical circuit breaker, or which is open without interaction with the drive as in a contactor and is closed by the drive. The contact system, the magnet system and usually at least one other spring act together in such a way,

• that in the de-energized state of the magnetic coils, the force balance of the permanent magnet, contact spring (s) and return spring (s) keeps open the main contact system and statically reliably forces the opening for each state which the components of the switching device can assume within the framework of the construction;
• that the operational closing of the main contact system takes place by energizing the contactor coil,
• that the operational keeping closed of the main contact system by clocked excitation of the contactor coil,
• that a normal opening of the main contact system by deenergizing (ie switching off the voltage on) of the contactor coil,
• in the event of a short circuit the quick shutdown is realized by switching off the voltage at the contactor coil and energizing the short circuit tripping coil,
• that the short-circuit release coil is energized in this case from a separate power source, such as a capacitor, and
• that in case of short circuit, the contactor coil is quickly de-energized by means of an electronic de-energizing circuit.

• der Anker und ein diesen und die Magnetspulen umgebendes Joch in geblechter oder ungeblechter Ausführung hergestellt werden,
• planare oder konzentrische Querschnitte für den Anker und den Gesamtausbau gewählt werden,
• die Permanentmagnete konzentrisch oder nur segmentweise im Koppelzweig oder an den Koppelzweigen des Magnetkreises angeordnet werden, und/oder
• das Koppelglied durch eine integrierte Übersetzungs- und Umlenkmechanik ergänzt werden.

In further embodiments of the invention can

• the armature and a yoke surrounding it and the magnet coils are produced in a non-braided or non-braided design,
• planar or concentric cross-sections are chosen for the anchor and the overall configuration,
• the permanent magnets are arranged concentrically or only in segments in the coupling branch or on the coupling branches of the magnetic circuit, and / or
• the coupling link is supplemented by an integrated translation and deflection mechanism.

Furthermore, in addition to the normal energization of the solenoid coils for the contactor coil and the contactor operation, a current from a capacitor charge is possible. Furthermore, instead of the linearly displaceable plunger, the coupling member can also be constructed as a rotary system in order to obtain further advantages in terms of friction and dynamics. Finally, the optionally existing contact spring can also be connected to the coupling member via a running counter-bearing to reduce the total force level of the drive.

• dass nach einer Kurzschluss- oder Überlastauslösung eine Wiederinbetriebnahme aus der Ferne möglich ist,
• dass mit der bipolaren Antriebseinheit sehr kleine Abschaltzeiten im Kurzschlussfall zu erzielen sind,
• dass die Antriebseinheit so ausgelegt werden kann, dass die Halteleistung im eingeschalteten Zustand des Schaltgeräts sehr klein ist,
• dass das Schaltgerät sehr kompakt realisiert werden kann, und
• das die elektronische Kurzschlussauslöserfunktion ohne zusätzlichen Antrieb oder Aktor (zum Beispiel Magnetaktor oder Piezoaktor) erreicht wird.

With the switching device according to the invention and its design variants in particular the advantages are achieved

• that after a short-circuit or overload trip a reminder is possible from a distance,
• that with the bipolar drive unit very short turn-off times can be achieved in the event of a short circuit,
• that the drive unit can be designed so that the holding power in the switched-on state of the switching device is very small,
• that the switching device can be realized very compact, and
• that the electronic short-circuit release function without additional drive or actuator (for example, magnetic actuator or piezoelectric actuator) is achieved.

FIG 1

in einem grob schematischen Längsschnitt ein Schaltgerät mit einem Hauptkontaktsystem, einer bipolaren elektromagnetischen Antriebseinheit mit einem ortsfesten Joch, zwei darin ortsfest gehaltenen Magnetspulen und einem verschiebbaren Anker sowie mit einem Koppelglied in Form eines Stößels zur Übertragung einer Stellkraft von der Antriebseinheit auf das Hauptkontaktsystem bei geschlossenem Hauptkontaktsystem,

FIG 2

in Darstellung gemäß FIG 1 das dortige Schaltgerät bei geöffnetem Hauptkontaktsystem,

FIG 3

in einem schematisch vereinfachten elektrischen Schaltbild einen Steuerschaltkreis zur Ansteuerung der beiden Magnetspulen des Schaltgeräts gemäß FIG 1,

FIG 4

in Darstellung gemäß FIG 1 eine alternative Ausführungsform des Schaltgeräts bei geschlossenem Hauptkontaktsystem,

FIG 5

in Darstellung gemäß FIG 1 das Schaltgerät gemäß FIG 4 bei geöffnetem Hauptkontaktsystem, und

FIG 6

in einem schematischen Längsschnitt eine weitere Ausführungsform des Hauptkontaktsystems.

Exemplary embodiments will be explained in more detail based on the invention with reference to a drawing. Show:

FIG. 1

in a roughly schematic longitudinal section, a switching device with a main contact system, a bipolar electromagnetic drive unit with a stationary yoke, two stationary held therein magnetic coils and a movable armature and with a coupling member in the form of a plunger for transmitting a force from the drive unit to the main contact system with the main contact system .

FIG. 2

in illustration according to FIG. 1 the local switching device with the main contact system open,

FIG. 3

in a schematically simplified electrical circuit diagram according to a control circuit for controlling the two magnetic coils of the switching device FIG. 1 .

FIG. 4

in illustration according to FIG. 1 an alternative embodiment of the switching device with the main contact system closed,

FIG. 5

in illustration according to FIG. 1 the switching device according to FIG. 4 with main contact system open, and

FIG. 6

in a schematic longitudinal section, a further embodiment of the main contact system.

Corresponding parts and sizes are always provided with the same reference numerals in all figures.

The 1 and 2 show roughly schematically simplified a first embodiment of a switching device 1, which is a so-called compact branch for supplying an electric motor with a supply current. The switching device 1 allows in a single device both the operational switching on and off under normal load as well as an overload shutdown and an emergency shutdown in the event of a short circuit.

The switching device 1 comprises a main contact system 2, a drive unit 3 and a coupling member 4.

For this purpose, it comprises two fixed contacts 11 and 12 and two moving contacts 13 and 14. The fixed contact 11 is in this case attached to the end of a power supply busbar 15, while the fixed contact 12 at the end of a Stromabführenden busbar 16 is attached. The two moving contacts 13 and 14 are mounted in juxtaposition to each other at the ends of a switching bridge 17. The switching bridge 17, together with the moving contacts 13 and 14 mounted therein between an in FIG. 1 shown closed position and a in FIG. 2 displaced opening position shown. In the closed position according to FIG. 1 lie while the moving contact 13 on the fixed contact 11 and the moving contact 14 on the associated fixed contact 12, so that on the busbar 15, the fixed contact 11, the moving contact 13, the switching bridge 17, the moving contact 14, the fixed contact 12 and the busbar 16 created an electrically conductive connection and the current path 10 thus closed is. In the open position according to FIG. 2 are both moving contacts 13 and 14 lifted from their respective associated fixed contacts 11 and 12, so that the current path 10 is interrupted.

The switching bridge 17 is acted upon by means of a contact spring 18 in the direction of the busbars 15 and 16, so that the moving contacts 13 and 14 are each biased in the direction of their closed position.

The drive unit 3 is formed by a bipolar magnet system. It comprises a circumferential yoke 20 in which two magnetic coils are accommodated. The remote from the main contact system 2 magnetic coil is hereinafter referred to as (contactor) coil 21. On the other hand, the magnetic coil facing the main contact system 2 is referred to as a (short-circuit release) coil 22. Between the two aligned in series coils 21 and 22 a plurality of permanent magnets 23 are arranged. At the mutually remote end faces of the coils 21 and 22, the yoke 20 has a respective acting as a pole piece 24 projection with which the yoke 20 protrudes slightly into the interior of the respective adjacent coil 21 and 22 respectively. Inside the coils 21 and 22, and thus in the axially bounded by the pole pieces 24 space, a cylindrical armature 25 is received in soft iron. The armature 25 has a space between the pole pieces 24 substantially undershooting length and is thus parallel to the axis of the coils 21 and 22 reversibly displaceable between two anchor positions. In an in FIG. 1 As shown, the first anchor position, the anchor 25 emerges primarily in the contactor coil 21 and is located on the front side of the remote from the main contact system 2 pole piece 24 of the yoke 20 at. In the in FIG. 2 shown other anchor position of the anchor 25 dives against it decisively in the short-circuit release coil 22 and is the end face of the main contact system 2 facing pole piece of the yoke 20 at.

In the drive unit 3 is a bistable magnet system in itself, in which the armature 25 as a result of the magnetic flux generated by the permanent magnet 23 in its two anchor layers according to FIG. 1 and according to FIG. 2 is stabilized as long as the coils 21 and 22 are de-energized, that is, are substantially de-energized. The armature 25 is replaced by a return spring 26 in the main contact system 2 facing armature position (according FIG. 2 ).

With regard to the drive unit 3 underlying magnetic operating principle is on DE 103 39 214 B4 and DE 101 46 899 A1 refer where similar magnetic systems are described in detail.

The coupling member 4 serves to transmit a control force from the drive unit 3 to the switching bridge 17, and thus to the movement of the moving contacts 13 and 14 between the closed position and the open position.

The coupling member 4 here consists of a plunger 28 which is fixedly connected to the armature 25 and thus moved with this. In a position hereinafter referred to as the "operating position" of the plunger 28, the in FIG. 1 is shown, the plunger 28 is retracted together with the armature 25 relative to the main contact system 2, so that the free end of the plunger 30 is arranged at a distance from the switching bridge 17. The moving contacts 13 and 14 are thereby moved under the action of the pressing on the switching bridge 17 contact spring 18 in its closed position.

According to FIG. 2 However, the plunger 28 is advanced together with the armature 25 in a "release position" against the switching bridge 17, so that the plunger 28 lifts the moving contacts 13 and 14 of the respectively associated fixed contacts 11 and 12.

In the FIG. 2 illustrated release position of the plunger 28 thus corresponds to the open position of the moving contacts 13 and 14th

The contact spring 18 and the return spring 26 are dimensioned and arranged with additional consideration of the forces generated by the permanent magnet 23 such that the plunger 28 together with the armature 25 in de-energized coils 21 and 22 always in FIG. 2 shown triggering position occupies. This position is monostable in the sense that the plunger 28 moves automatically from any other position in the release position, as long as the coils 21 and 22 are de-energized. Thus, the moving contacts 13 and 14 are always in their de-energized coils 21 and 22 in their - also monostable - open position.

To close the switching device 1, thus for moving the moving contacts 13 and 14 in its closed position, the contactor coil 21 is acted upon by an operating voltage and thus excited. As a result, the armature 25 is overcome by overcoming the forces exerted by the return spring 26 and the permanent magnet 23 forces in the armature position FIG. 1 deflected. The plunger 28 is taken with the armature 25 in its operating position. Under the retraction of the plunger 28, in turn, the moving contacts 13 and 14 are moved under the action of the contact spring 18 in its closed position.

In order to effectively hold the switching device 1 in its closed state, and in particular to limit the holding force of the drive unit 3 to a required minimum, the contactor coil 21 is constantly energized only to attract the armature 25 for a predetermined period of time (tightening time). Rather, the contactor coil 21 is only partially energized in a holding phase after the closing time by the contactor coil 21 is subjected to a pulse width modulated, and thus temporally clocked voltage. The pulse width ratio of this clocked holding voltage is such chosen that the anchor 25 just barely in the in FIG. 1 represented anchor position is held.

For operational shutdown of the switching device 1 and for forced shutdown in the event of overload (ie an overcurrent flowing through the switching device 1), the contactor coil 21 is de-energized by switching off the holding voltage. The armature 25 and the plunger 28 are here under the action of the return spring 26 in the release position according to FIG. 2 pressed, whereby the moving contacts 13 and 14 are moved back into its open position.

In the event of a short circuit in the current path 10 closed by the switching device 1, the contactor coil 21 is simultaneously deenergized and the short-circuit release coil 22 is energized. Under the action of the forces acting on the armature 25 by the short-circuit release coil 22 and the return spring 26, the plunger 28 is moved particularly rapidly into its release position for rapid shutdown of the switching device 1.

The switching device 1 is in this case designed such that it can be switched off within 5 ms in the event of a short circuit.

FIG. 3 shows an electronic control circuit 30 of the switching device 1. This control circuit 30 includes a first circuit portion 31 for controlling the contactor coil 21, a second circuit portion 32 for controlling the short-circuit release coil 22 and a common control unit 33rd

The circuit part 31 is essentially formed by a voltage source 34 and a semiconductor switch 35, which are connected in series with the contactor coil 21. An in FIG. 3 Registered resistor 36 illustrates in the manner of an equivalent circuit diagram, the ohmic resistance of the contactor coil 21. Parallel to the contactor coil 21 in the circuit part 31, a de-energizing circuit 37 is connected, which consists of a (in the reverse direction in the potential difference generated by the voltage source 34 connected) freewheeling diode 38 and an antiparallel connected thereto Zener diode 39 is formed.

The circuit part 32 also comprises a voltage source 40 and a semiconductor switch 41, which are connected together with a charging resistor 42 in series with the short-circuit release coil 22. An in FIG. 3 Registered resistor 43 again illustrates in the manner of an equivalent circuit diagram the ohmic resistance of the short-circuit release coil 22. The circuit part 32 further comprises, as an electronic energy store, a capacitor 44, which is connected in parallel with the voltage source 40 and the charging resistor 42.

The semiconductor switches 35 and 41 are driven by the control unit 33, which is formed in particular by a microcontroller with a control software implemented therein.

To energize or de-excite the contactor coil 21 of the semiconductor switch 35 is controlled by the control unit 30 (closed or electrically switched) or controlled (open or locked). In the hold phase, the semiconductor switch 35 is clocked up and closed by the control unit 33 with the preset pulse width ratio.

When switching off the contactor coil 21 causes the de-energizing circuit 37 accelerated de-energizing the contactor coil 21, that is an accelerated collapse of the current flowing through the coil 21 by the coil 21 after opening the semiconductor switch 35 via the Zener diode 39, the freewheeling diode 38 for discharging the Coil current is bridged.

In normal operation of the switching device 1, the capacitor 44 in the circuit part 32 with open semiconductor switch 41 via charged the charging resistor 42. In the case of a short circuit, the semiconductor switch 41 is closed by the control unit 33, so that the capacitor 44 is discharged via the short-circuit release coil 22. Due to the electrical energy stored in the capacitor 44, the coil 22 is energized much faster than would be possible by direct connection of the voltage source 40.

For particularly rapid separation of the moving contacts 13 and 14 of the supplied fixed contacts 11 and 12 - in particular in the case of short circuit - further contributes also that the plunger 28 in its operating position according to FIG. 1 is mounted at a distance from the switching bridge 17. As a result, the armature 25 and the plunger 28 namely when released initially accelerated by the switching bridge 27 and acting on this contact spring 18 and thereby hit already at high speed on the contact bridge 17. By impulse transmission, the moving contacts 13 and 14 are particularly fast in this shifted their open position, which favors a rapid collapse of the current flowing through the current path 10.

As a safety measure both coils are energized in the de-energized state by the control circuit 30 with a low voltage, under the effect of which a low quiescent current always flows through the coils. The control unit 33 continuously monitors these quiescent currents and, in the event of a breakdown of the quiescent current-for example, as a result of a power failure in one of the coils 21 and 22-causes the disconnection of the switching device.

A second embodiment of the switching device 1 is in the 4 and 5 shown in the closed position or open position of the main contact system 2. This embodiment of the switching device 1 differs from the embodiment according to 1 and 2 in that the switching bridge 17 is mounted directly on the plunger 28 via the contact spring 18. The coupling member 4 includes for this purpose as with the plunger 28 entraining Abutment for the contact spring 18, a bearing plate 50, the freiendseitig on the - here by the switching bridge 17 projecting plunger - 28 is mounted.

In the embodiment of the switching device 1 according to 4 and 5 Thus, the contact spring 18 and the return spring 16 act in the same direction on the plunger 28th

In FIG. 6 Furthermore, an alternative embodiment of the main contact system 2 is shown. This differs from the above embodiments in that the switching bridge 17 is not linearly displaceable, but about an axis 60 between the (in FIG. 6 shown by solid lines) closed position and the (in FIG. 6 indicated by dashed lines) opening position of the moving contacts 13 and 14 is pivotable.

The object of the invention is not limited to the embodiments described above. Rather, other embodiments of the invention may be derived by those skilled in the art from the foregoing description. In particular, the individual features of the invention described with reference to the various exemplary embodiments and their design variants can also be combined with one another in a different manner.

Claims (9)

1. Switching device (1)

   - with a main contact system (2), which has at least one fixed contact (11,12) and at least one associated movable contact (13,14), wherein the movable contact (13,14) can be moved in a reversible manner in respect of the fixed contact (11,12) to close and isolate a current path (10) between two switch positions, namely a closed position and an open position,

   - with a bipolar electromagnetic drive unit (3), which has a movable armature (25) as well as a first stationary magnet coil (21) and a second stationary magnet coil (22) for reversibly moving the armature (25) between two permanently magnetic stabilised armature positions, and

   - with a coupling member (4) for transmitting an actuating force from the drive unit (3) to the movable contact (13,14), wherein the coupling member (4) can be moved between an operating position corresponding with the closed position of the movable contact (13,14) and a trip position corresponding with the open position of the movable contact (13,14),

   - wherein the movable contact (13,14) can be moved into the closed position through selective excitation of the first magnet coil (5), and the movable contact (13,14) can be moved into the open position through selective excitation of the first magnet coil (22) within a minimum switch-off time permissible for a short circuit in the current path (10),

   characterised in that

   - with de-excited magnet coils (21,22) the movable contact (13,14) is held in the open position in a monostable manner, and

   - the switching device (1) comprises at least one back pressure spring (26) which pretensions the coupling member (4) in the direction towards the trip position.
2. Switching device (1) according to claim 1,
   with at least one contact spring (18) which pretensions the movable contact (13,14) in the direction towards one of its two switch positions.
3. Switching device (1) according to one of claims 1 to 2,
   with an electronic control circuit (30) for controlling the first magnet coil (21) and/or the second magnet coil (22).
4. Switching device (1) according to claim 3,
   wherein the control circuit (30) is designed to partially excite the first magnet coil (21) through a clocked holding current, so that the movable contact (13,14) is held in the closed position.
5. Switching device (1) according to claim 3 or 4,
   wherein the control circuit (30) has a de-excitation circuit (37) for the accelerated de-excitation of the first magnet coil (21) in the event of a short circuit in the current path (10).
6. Switching device (1) according to one of claims 3 to 5,
   wherein the control circuit (30) has an electrical energy store (44), in particular a capacitor, for the excitation of the second magnet coil (22) in the event of a short circuit in the current path (10).
7. Switching device (1) according to claims 3 and 6, wherein the control circuit (30) is designed to de-excite both magnet coils (21,22) or leave them in a de-excited state in order to switch off the current path (10) in an operationally-correct manner with normal load or in the event of overload in the current path (10).
8. Switching device (1) according to one of claims 1 to 7,
   wherein the coupling member (4) is decoupled from the movable contact (13,14) in its operating position, and wherein the coupling member (4) can be accelerated by the drive unit (3) in the direction towards its trip position in the event of a short circuit in the current path (10), so that it only hits the movable contact (13,14) indirectly or directly with a non-zero pulse.
9. Switching device (1) according to one of claims 1 to 8,
   wherein a low rest current is applied to the first magnet coil (21) and/or the second magnet coil (22) in a de-excited state.

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