circuit breaker

Abstract

The invention relates to a circuit breaker (10) with a switch (12) that is actuated depending on a tripping characteristic. The tripping characteristic depends on the direction of an electric current. The invention further relates to a use of a circuit breaker (10).

Description

The invention relates to a circuit breaker and to the use of a circuit breaker.Industrial plants usually have a plurality of actuators, by means of which a creation and / or machining of workpieces takes place. The actuators themselves usually comprise an electric motor which is energized by means of a converter. At least, the actuators are usually operated by means of an electric current. For simplified interconnection, the individual actuators, in particular the converters, are connected in parallel with one another and fed by means of a common DC voltage intermediate circuit, so that a DC circuit is formed. Usually, a DC voltage between 400 V and 650 V is carried by means of the DC voltage intermediate circuit, and this is fed by means of a DC voltage source, for example a rectifier, which is connected to a supply network.Since the actuators are actuated differently, the amounts of energy drawn from the DC voltage intermediate circuit are variable over time, which leads to fluctuations in the electrical voltage present at the DC voltage intermediate circuit. In order that the operation of the respective actuator is not influenced by it, each converter usually has an energy store in the form of a capacitor, by means of which the respectively used electrical voltage is stabilized.In order that, in the event of a fault in an actuator, for example in the event of a short circuit in the electric motor or in the converter, further damage to the respective actuator or to the environment, for example due to a fire which arises, is prevented, each actuator is usually electrically connected to the DC voltage intermediate circuit by means of a circuit breaker. The electrical current supplied to the respective actuator is monitored by means of the circuit breaker, and if this exceeds a specific threshold value, a switch of the circuit breaker is actuated, so that the current flow to the actuator is interrupted.In the event of a short circuit in one of the actuators, it is possible that the electric current flowing to this actuator is not only provided by the DC voltage source, but that an energy store of an actuator connected in parallel therewith is also emptied. Due to the low-resistance connection in the case of the defective actuator, a comparatively large electric current thus flows from the energy store of the parallel-connected actuator via the circuit breaker assigned to the parallel-connected actuator back into the DC voltage intermediate circuit and from there to the defective actuator. Depending on the circuit breaker used, it is possible here that the circuit breaker is actuated on account of the increased electric current, with the result that the actuator connected in parallel is disconnected from the DC voltage intermediate circuit, although said actuator has no malfunction. This results in an unnecessary failure of this actuator, which is why the operating costs of the industrial plant are increased.The object of the invention is to specify a particularly suitable circuit breaker and a particularly suitable use of a circuit breaker, wherein a number of unnecessary solutions is advantageously reduced and / or operational reliability is increased.With regard to the circuit breaker, this object is achieved according to the invention by the features of claim 1 and with regard to use by the features of claim 8. Advantageous refinements and refinements are the subject matter of the respective dependent claims.The circuit breaker serves in particular for protecting a device, and the circuit breaker is, for example, a device circuit breaker. Alternatively or in combination, the circuit breaker serves to protect a line and is thus a line circuit breaker. At least, the circuit breaker is preferably suitable, in particular provided and configured, for being introduced into a circuit and, in the event of a fault, for interrupting a current flow via the latter.The circuit breaker comprises in particular two connections, between which a current path is formed. The circuit breaker has a switch which is expediently a component of the current path. The switch has two different states, i.e. in particular an electrically conductive (closed) and an electrically non-conductive (open). In particular, if the circuit breaker is in the electrically conductive state, the electrical current conducted via the circuit breaker is conducted by means of the switch.For example, the switch is designed as a semiconductor switch, in particular as a power semiconductor switch. For example, the switch is a field effect transistor such as a MOSFET, GTO, or IGBT. Particularly preferably, however, the switch is a mechanical switch and is configured, for example, in the manner of a relay or a contactor. Thus, electrical losses occurring during operation are reduced.The switch is actuated as a function of a triggering characteristic curve. For this purpose, the circuit breaker preferably has an interconnection which is formed, for example, at least partially by means of electrical and / or electronic components. In particular, the interconnection of a plurality of discrete components, on the basis of which the triggering characteristic curve is created, comprises. In summary, the switch, in particular a control input of the possible semiconductor switch and / or of a drive, if the switch is mechanically designed, is expediently connected in such a way that it is actuated as a function of the triggering characteristic curve.In this case, different threshold values / limit values for operating parameters are expediently specified in the triggering characteristic curve, wherein, when said threshold value is exceeded by the respective operating parameter, the switch is actuated, is suitably set into the electrically non-conductive state. For example, the trigger characteristic curve applies to a plurality of operating parameters, so that it is a characteristic diagram. For example, an applied electrical voltage is used as the operating parameter, which is produced, for example, via the switch and / or to ground. Alternatively or in combination therewith, the presence of specific artifacts in a conducted electric current and / or the applied electric voltage is used as operating parameters. Particularly preferably, however, the operating parameter is the electric current which is carried, different limit values being expediently specified for specific periods of time by means of the triggering characteristic curve. If a certain current is present via the switch and the associated time period is exceeded, the switch is actuated in particular. In summary, a level of the electric current and a time period are preferably stored by means of the triggering characteristic curve.The triggering characteristic curve, which is also referred to merely as a characteristic curve, is dependent on a direction of the carried electric current. In other words, the switch is actuated differently, depending on the direction in which the electric current is conducted via the circuit breaker and thus also via the switch. In yet other words, the circuit breaker thus comprises a direction-dependent triggering characteristic curve. In particular, the connection of the circuit breaker is thus such that the switch is actuated depending on the direction of the current carried in accordance with the respectively valid triggering characteristic curve. In this case, for example, in one of the directions, no triggering of the switch takes place at all, independently of the operating parameter realized in each case. Thus, the electric current can be conducted substantially undisturbed in this direction. Alternatively, the threshold values are adapted accordingly, for example. In a further alternative, different operating parameters are used for the two directions, for example.On account of such a configuration of the circuit breaker, it is thus possible by means of which it is possible to monitor in a targeted manner for a fault case of a load energized thereby, such as an actuator, in particular a short circuit in the case of this load. In the event of a short circuit, the electric current is conducted via the circuit breaker only in one of the two directions. Thus, if the electric current occurs in the opposite direction, it is not caused by a short circuit in the load. In particular, the switch is not actuated in this case. It is thus possible to use the corresponding triggering characteristic curve for the respective load which is protected by means of the circuit breaker, so that overloading or damage to the load is avoided. In the opposite direction, a different triggering characteristic curve is used, by means of which a greater electric current flow from the load into a supply network or the like supplying the load is expediently made possible, without triggering of the circuit breaker taking place. Thus, the actuator is still operational, especially as it does not have a malfunction. This triggering characteristic is expediently matched to the possible supply network, so that damage to the latter is also prevented. Consequently, a number of unnecessary solutions are reduced. However, since the trip characteristic curve can be separately adapted to the load and / or the possible supply network, operating reliability is nevertheless increased.In particular, the circuit breaker is used in a direct current circuit, that is to say, for example, between a load and a direct voltage intermediate circuit or the like. In this case, in particular the triggering characteristic curve for a current flow from the DC voltage intermediate circuit to the load is adapted to the load used, so that in the event of a fault in the load, such as the short circuit, the current flow to the load is interrupted. In the case of an opposite current flow, on the other hand, in particular the trip characteristic curve is adapted to the DC voltage intermediate circuit or other components of the respective installation in which the load is used, so that said circuit is likewise protected.Preferably, an electrical DC voltage between 400 V and 650 V is present in the DC voltage intermediate circuit, i.e. in particular a higher DC voltage. In particular, the circuit breaker is used to protect an actuator in an industrial installation. The actuator forms the load in particular. Due to the reduced number of unnecessary solutions, i.e. actuation of the switch, namely the opening of the switch, the number of failures is reduced, and therefore operating costs are reduced. As an alternative to the application in an industrial plant, the circuit breaker is used, for example, in an electric vehicle, such as a motor vehicle, an aircraft or a ship / boat.Preferably, the switch is connected in series with a trigger. In this case, the switch is actuated in particular by means of the trigger, and the switch and the trigger expediently form at least partially, for example completely, a latch which is at least partially mechanically configured. Thus, robustness is increased. Alternatively, the latch lock is, for example, electrohydraulically designed or electromechanical. By means of the trigger, for example, a component of the switch is held in a latch, in particular against an otherwise acting force, for example a spring force. Alternatively or in combination therewith, the latch is actuated by means of the trigger, if necessary, so that the force acts unimpeded on the switch.The trigger is bridged by means of a current direction-dependent component. In particular, the component dependent on the direction of current is connected in parallel with the trigger. The current direction-dependent component is a component which, when an electric current is conducted via the latter, exhibits a different behavior depending on the current direction. By means of the current direction-dependent component, in particular the dependence of the triggering characteristic curve on the direction of the carried electric current is provided, for which reason it is also possible in particular to retrofit an already existing circuit breaker accordingly. In summary, the current-direction-dependent triggering characteristic curve is thus provided in particular on account of the current-direction-dependent component in conjunction with the parallel connection to the trigger.For example, the release is a bimetallic snap disc or a bimetallic strip, by means of which a constituent part of the switch is at least partially formed. In this case, the bimetallic snap disc / bimetallic strip also guides the electrical current which is conducted via the switch. If this is comparatively large, the bimetallic snap disc / strip is heated, so that the latter deforms, for which reason it no longer bears against further components of the switch, so that the current flow is interrupted. Alternatively, the bimetallic snap disc / bimetallic strip acts on further components of the switch, by means of which the current flow via the circuit breaker can be interrupted. More preferably, however, the trigger includes an electrical trip coil electrically connected in series with the switch. In other words, the trigger is thus a magnetic trigger. The trigger is expediently arranged in such a way that the magnetic field thus produced in the event of a comparatively high electric current releases a link by means of which the switch is held in a closed state. In particular, the triggering coil is configured in such a way that the switch is opened when three times the rated current is conducted by means of the circuit breaker. In contrast, at lower electrical currents, the applied magnetic force is too low to release the linking. Due to the current direction-dependent component, the triggering coil acts predominantly in one current direction, whereas in the other current direction an effect of the latter is reduced. It is thus possible to use the circuit breaker for protecting a load in the event of a short circuit in a DC voltage circuit. In contrast, in the opposite direction, in which an excessive current flow is not caused by a short circuit of the load, the trip coil is used to a lesser or different extent to actuate the switch.For example, the circuit breaker or at least the current path formed between the possible connections is formed only by means of the switch and the trigger. At least, however, the latch includes only the switch and the trigger, for example. Manufacturing costs are thus reduced and robustness is increased. Particularly preferably, however, a further trigger is connected electrically in series with the switch. Thus, the further trigger is also electrically connected in series with the trigger and expediently in the assembled state with the load to be secured. The further release is not bridged by means of the current direction-dependent component. For example, the further trigger is bridged by means of another current direction-dependent component, wherein the dependence of the two components on the current direction differs. Particularly preferably, however, the further trigger is not bridged by means of a current direction-dependent component, so that the further trigger operates independently of the current direction. Thus, by means of the further trigger, both protection of the load to be supplied with current and of the supply network, if any, takes place. Particularly preferably, the further trigger has a different triggering characteristic curve than the trigger. Thus, functionality is increased. Preferably, the trip comprises or is formed with the electrical trip coil and the further trip suitably comprises or is formed with a bi-metal snap disc / strip. At least, however, the further release expediently comprises a bimetallic element. At least, however, the further trigger in particular only triggers when a reduced electric current is carried over a longer period of time, which however is in particular greater than the rated current. In contrast, the trigger triggers in the event of an increased electrical current, even if it predominates only for a comparatively short period of time. On account of the further trigger, protection therefore takes place in particular in the case of fault sources which do not correspond to a direct short circuit, whereas the trigger serves to protect against a short circuit. In this case, no two different circuit breakers are required.For example, the current-direction-dependent component comprises a suppressor diode or a zener diode. Depending on the direction of the electric current, these have a different behavior, so that the direction-dependent triggering characteristic curve can be realized by means of these. For example, the current direction-dependent component comprises a plurality of such individual components which are suitably interconnected, for example in parallel and / or in series. This increases flexibility in the creation of the triggering characteristic curve. Particularly preferably, however, the current direction-dependent component comprises a diode, by means of which in particular a current flow is made possible only in a single direction. For example, the current-direction-dependent component comprises further electrical and / or electronic components which are suitably interconnected with one another. Particularly preferably, however, the current direction-dependent component is formed by means of the diode. Manufacturing costs and space requirements are thus reduced. In this way, it is also possible to retrofit an already existing circuit breaker comparatively cost-effectively. Due to the diode, current then coming to be conducted by means of the trigger is thus in one of the two directions, namely the opposite direction to the forward direction of the diode. In the opposite direction, the current flow takes place in particular via the diode, at least when the trigger has a higher internal resistance than the diode. In this case, the switch is thus not actuated by means of the trigger.Alternatively or in combination, the current direction-dependent component comprises a semiconductor switch. This has a reduced internal resistance compared to the diode when it is in the electrically conductive state. It is thus ensured that even in the case of a comparatively low-ohmic trigger, the electric current flows via the current-direction-dependent component when the latter is in the electrically conductive state. For example, a measuring resistor is present, by means of which the current direction is determined, the semiconductor switch being actuated on the basis of the electrical voltage arising above it. Particularly preferably, the semiconductor switch is actuated as a function of an electrical voltage produced via the trigger.Preferably, a comparator is present here, by means of which the sign of the electrical voltage is determined. The comparator is provided, for example, by means of an interconnection of an operational amplifier. In particular, the operational amplifier and / or the semiconductor switch are supplied here by means of an external voltage supply. However, these are particularly preferably supplied during operation by means of the electric current conducted via the switch or at least one electric voltage present at the possible terminals of the circuit breaker, for which purpose in particular series resistors, protective diodes and / or voltage dividers are present. Expediently, an interconnection of the circuit breaker is adapted thereto. Installation of the circuit breaker is thus simplified.In a further alternative, the circuit breaker comprises a drive which acts on the switch. Here, when the drive is energized, in particular a switching position of the switch is changed. Expediently, the switch is a mechanical switch, such as a relay or contactor, or at least comprises the latter. The drive is, for example, an electric coil or comprises at least one electric coil, within which an armature is arranged, which acts on the switch, in particular a contact bridge. Alternatively, the drive acts, for example, on a latch, by means of which the switch is held in a switch position counter to an acting force. In summary, for example, the drive acts directly on the switch, in particular the possible contact bridge, or serves to release a mechanical latch, or serves first to release the mechanical latch and then acts on the contact bridge.The circuit breaker preferably comprises a control unit by means of which the drive is actuated. The control unit comprises, for example, a microcontroller or is formed therewith. The control unit preferably comprises a plurality of discrete electrical components, to which microcontrollers are suitably connected. Alternatively, the control unit is formed only by means of discrete components, in particular electrical components. The circuit breaker preferably comprises one or more sensors for detecting an operating state of the circuit breaker, in particular the possible operating parameter. Suitably, at least one of the sensors is a current sensor by means of which the electric current conducted via the circuit breaker can be measured or determined in another manner. Alternatively or in combination therewith, at least one of the sensors is designed as a voltage sensor, and by means of which it is possible to detect the voltage produced via the switch, the electrical voltage produced via the possible current sensor and / or an electrical voltage with respect to ground. In a further alternative, one of the sensors comprises a reed relay and / or a thermal trigger, such as a bimetal, NTC, PTC or a snap disc, a magnetic and / or a hydraulic trigger. The respective trigger / sensor is used in particular as a signal transmitter for the control unit.The drive is operated, for example, by means of a separate power supply, by means of which a control voltage is thus provided in particular for the drive. It is thus possible to use the circuit breaker even at a wide range of electrical currents / voltages without a mode of operation of the drive being changed. If the separate / external power supply is used, an energy store, such as a capacitor, is provided in particular, by means of which, for example, if a control line or the like breaks off, reliable actuation of the switch is nevertheless made possible for at least a short period of time. In addition, the capacitor in particular stabilizes the electrical control voltage used. For example, the capacitor / the energy store is only charged up to the level of the control voltage. Alternatively, charge pumps, voltage multipliers or other arrangements are provided by means of which the electrical voltage can be increased. It is thus possible to actuate the drive with a comparatively high electrical energy, which shortens a switching process of the switch.In an alternative, the drive is energized at least partially by means of the electric current conducted via the circuit breaker and / or the electric voltage present thereon, in particular on the possible current path. Installation of the circuit breaker is thus facilitated. Here, for example, the drive is continuously energized if the electrical current is conducted by means of the circuit breaker. In particular, in this case, the switch is acted upon by a further force, which is compensated by means of the drive. Alternatively, for example, the drive is energized when opening of the switch is to take place.The drive comprises, for example, a so-called "moving magnet actuator". The moving magnet actuator (moving magnet actuator) has a permanent magnet which is mounted movably. For example, the permanent magnet is rotatably mounted or particularly preferably linearly movable. The permanent magnet is expediently connected to the possible contact bridge or at least operatively connected to the switch, such that when the permanent magnet moves, the switching position of the switch is changed, wherein expediently the contact bridge is preferably moved. In addition, the moving magnet actuator has a drive unit with one or more electrical coils, which are energized when the drive is actuated, so that a magnetic interaction takes place between the latter and the permanent magnet. The electrical coils are held stationary.Since the electric coil(s) is / are held stationary, a construction is simplified and, with the exception of the components required for the bearing, no further movable components or electrical connections are required between the movable components, namely the permanent magnet, and the stationary components of the moving magnet actuator, which is also referred to below merely as actuator. Friction is thus also reduced. Since the number of movable components of the moving magnet actuator, in particular only the permanent magnet, is comparatively small, and these in particular have a comparatively low weight, a dynamic of the actuator is comparatively high. Thus, inertia in operating the switch is reduced.For example, the actuator is configured to be rotational or particularly preferably linear. In this case, the drive unit has two electric coils arranged concentrically on an axis, which are spaced apart from one another along the axis, and between which the permanent magnet is arranged, the two poles of which are opposite one another with respect to the axis, and which is mounted movably along the axis. The two electrical coils are in particular simultaneously energized and are connected electrically in series or particularly preferably electrically in parallel with one another, for example. The connection of the electrical coils is such that, when they are energized, a magnetic field is created by means of the electrical coils, which magnetic field interacts with the magnetic field of the permanent magnet such that it is pulled along the axis toward one of the electrical coils and pressed away from the other. Consequently, a comparatively large force acts on the permanent magnet, and therefore dynamics are further enhanced.Particularly preferably, the actuator also has a (magnetic) short-circuiting plate or the like, by means of which the permanent magnet is held in a specific position when no current is supplied to the electric coil(s). For example, in this case the permanent magnet abuts the short-circuiting plate or is particularly preferably always spaced therefrom. The short-circuiting plate is expediently made of a ferromagnetic material, such as iron, for example, and therefore production costs are reduced. Due to the short-circuit plate, the permanent magnet is stabilized in one position, in particular when the switch is closed. Consequently, the mechanical switch is configured to be at least monostable or bistable.For example, the actuator has only the single drive unit. Particularly preferably, however, the "moving magnet actuator" has two drive units, one of which is formed in particular by means of the two electrical coils or at least comprises these, which are connected electrically in parallel or in series with one another. Suitably, the other drive unit also comprises two electrical coils, also electrically connected in parallel or in series. In this case, in particular each of the electrical coils of the one of the drive units is surrounded in each case by one of the electrical coils of the other drive units, and these are in particular arranged concentrically with respect to one another in each case. A comparatively compact "moving magnet actuator" is thus provided.By means of the two drive units, it is possible to exert a comparatively large force on the permanent magnet, so that the latter is accelerated comparatively strongly. As a result, a switching time of the switch is also accelerated, suitably in the event of a fault. However, it is also possible to actuate the mechanical switch only with one of the drive units, so that an electrical and also mechanical load and an energy requirement are reduced. As a result, an area of use of the circuit breaker is enlarged, and this is also used, for example, during normal operation for interrupting the electric current, wherein only one of the drive units is energized. In the event of a fault, on the other hand, both drive units are used to actuate the switch. Thus, a number of required components is reduced.The two drive units can be supplied with current separately by means of the control unit, for example, and are suitably connected for this purpose. In particular, however, it is also possible to supply current to the two drive units simultaneously. In this case, the separate voltage supply is used in particular for the operation of the drive. In an alternative, one of the drive units is energized by means of the electric current conducted via the switch. The drive unit is electrically connected in series with the switch. In this case, the rated current is in particular not sufficient to generate a magnetic field which moves the permanent magnet. On the other hand, if the electric current supplied through the switch further increases, the strength of the magnetic field is also increased, and it is sufficient to move the permanent magnet. The other drive unit is energized in particular by means of the separate voltage supply or can be energized by means of the latter. Thus, it is also possible to interrupt the current flow independently of an overcurrent or short-circuit current. In a further alternative, an element with a defined, for example constant or controlled / regulated resistor is connected in parallel with this drive unit. In particular, the element is designed in such a way that, in the case of a rated current, its resistance is lower than the resistance provided by means of the drive unit. Thus, in this case, the electric current flows predominantly through the element. If, on the other hand, the overcurrent / short-circuit current is present, the resistance of the trip unit is lower, so that the electric current flows via the trip unit. Consequently, the magnetic field is created, which leads to a movement of the permanent magnet.A circuit breaker having a switch which is actuated as a function of a trip characteristic curve, the trip characteristic curve being dependent on a direction of the carried electric current, is used for safeguarding a load in a direct current circuit. In this case, the electrical current is preferably conducted via the circuit breaker in normal operation only in one of the two directions. This corresponds in particular to a direction of the electric current during the short circuit of the load. Expediently, the direct current circuit comprises a plurality of such loads, which are in particular connected electrically in parallel with one another and are conducted against a direct voltage intermediate circuit of the direct voltage circuit. Due to the circuit breakers, it is thus avoided that, in the event of a short circuit of one of the loads, the circuit breakers which are associated with the other loads are actuated. In particular, the invention also relates to such a direct current circuit, which is in particular a component of an industrial plant. In this case, the load or some of the loads form an actuator, by means of which, for example, a workpiece is machined and / or produced.The developments and advantages explained in connection with the circuit breaker are to be transferred analogously also to the use / the direct current circuit and to one another and vice versa.Exemplary embodiments of the invention are explained in more detail below with reference to a drawing. Shown therein are: FIG. 1 schematically shows a direct current circuit with two loads, each of which is assigned a protective switch, FIGS. 2-4 schematically simplified a circuit diagram of one embodiment of the circuit breaker, FIG. 5 shows a sectional illustration of a detail of a drive of one of the circuit breakers, and FIGS. 6, 7 schematically simplified a circuit diagram of in each case further embodiments of the circuit breaker.Corresponding parts are provided with the same reference numerals in all figures.FIG. 1 schematically shows, in simplified form, a direct current circuit 2 which comprises a direct voltage source 4. By means of this, an electrical DC voltage of 650 V is provided, and by means of this, a DC voltage intermediate circuit 6 is fed. By means of this, two loads 8 are supplied, which are connected in parallel to one another and are guided against the DC voltage intermediate circuit 6 via a respective circuit breaker 10, which are structurally identical to one another.FIG. 2 shows a schematically simplified circuit diagram of the circuit breaker 10. The circuit breaker 10 has a switch 12 which is designed as a mechanical switch. The switch 12 is electrically connected in series with a trigger 14 and a further trigger 16. This series circuit is a component of a current path which is connected between two terminals, not shown in detail, of the circuit breaker 10, one of which is assigned to the DC intermediate circuit 6 and the other to the load 8.The further release 16 is designed as a bimetallic snap disc which, depending on the temperature, has two different shapes. At a normal temperature of the bimetallic snap disc, the latter holds a latching of the switch 12, so that the latter is held in a specific switching state, namely the closed state. The switch 12 is loaded here by means of a further force, such as a spring force, which is designed such that, when the latch is released, the switch 12 changes over into the open state.The trigger 14 is a magnetic trigger and includes a trigger coil 18. The current flows through this by means of the electric current conducted via the switch 12, and an armature, not shown in detail, is arranged in this armature, which also acts on the latching of the switch 12. The trigger 14, the further trigger 16 and the switch 12 are combined to form a common unit, namely a latch 20, which is of electromechanical design, wherein the circuit breaker 10 is a thermal / magnetic circuit breaker. Connected electrically in parallel with the trigger 14 is a current direction-dependent component 22, by means of which the trigger 14 is thus bridged. The current direction-dependent component 22 has a different behavior, depending on the direction of the electric current conducted via the parallel-connected trigger 14. The current direction-dependent component 22 is a diode 24 in this case. the forward direction of the diode 24 is in this case opposite the desired current application direction of the load 8, so that during normal operation the electric current provided by the voltage source 4 is conducted via the trigger 14 to the respective load 8. Only a return current from the load 8 back into the DC voltage intermediate circuit 6 is conducted via the diode 24.In normal operation, i.e. when the load 8 is energized in the desired manner, the electric current flows from the DC voltage intermediate circuit 6 via the closed switch 12, the further trigger 16 and the trigger 14 to the load 8. The magnetic field provided by means of the triggering coil 18 of the trigger 14 is also not sufficient to release the latching of the switch 12, so that the current can be supplied to the load 8 essentially undisturbed via the circuit breaker 10.If the electric current exceeds a certain limit value, such as twice the rated current, the magnetic field provided by the release coil 18 is increased, but not sufficient to release the latching. However, the bimetallic snap disc of the further release 16 is heated up, the longer the increased electric current is conducted. After a certain period of time, which is dependent on the level of the electric current that is conducted, the heating is so great that the bimetallic snap disc is deformed. Consequently, the latch of the switch 12 is released and it is opened due to the acting force. Thus, the energization of the load 8 is interrupted.If a short circuit is present at the load 8, the electric current conducted via the circuit breaker 10 rises rapidly and more strongly and is in particular more than five times the rated current. In this case, the magnetic field provided by means of the triggering coil 18 is sufficient to release the latching, so that the current flow via the circuit breaker 10 is interrupted after a comparatively short period of time. The heating up of the bimetallic snap disc which has hitherto taken place, on the other hand, still leads to no deformation of the latter. On the basis of the trigger 14 and the further trigger 16, a triggering characteristic curve is thus provided, as a function of which the switch 12 is actuated.In the direct current circuit 2, it is possible that a short circuit occurs only in one of the loads 8, which is also referred to below as a defective load 8. Due to the short circuit, a low-ohmic connection is present, wherein it is possible that not only the electric current provided by means of the voltage source 4 flows to the defective load, but also a current provided by means of the load 8 still functioning, for example by means of an energy store thereof. Thus, a comparatively high electric current is fed back into the DC intermediate circuit 6 from the functioning load 8 via the associated circuit breaker 10, at least until the circuit breaker 10 associated with the defective load 8 triggers and interrupts the current flow to the defective load 8.The (reverse) current from the functioning load 8 does not flow via the trigger 14 of the associated circuit breaker 10 but via the diode 24, so that the switch 12 is not actuated despite the comparatively large current. Thus, as soon as the defective load 8 is disconnected from the DC intermediate circuit 6 by means of the associated circuit breaker 10, the functioning load 8 continues to be ready for use. If, however, the (electric) reverse current is present over a comparatively long period of time, the bimetallic snap disc is also heated here, which leads to the latching being released, with the result that the switch 12 is also then actuated. Consequently, in the case of the other current direction via the circuit breaker 10, the triggering characteristic curve is changed and the triggering characteristic curve is therefore dependent on the direction of the electric current carried via the latter. In summary, each of the circuit breakers 10 is used to protect one of the loads 8 in the direct current circuit 2 in each case.FIG. 3 shows a development of the circuit breaker 10 shown in FIG. 2. The variant corresponds substantially to the preceding configuration, wherein, however, the current-direction-dependent component 22 is modified. This circuit includes a semiconductor switch 26 by means of which the trigger 14 is bypassed. Furthermore, an operational amplifier 28 is present, which is connected as a comparator and by means of which the sign of the electrical voltage arising via the trigger 14 is determined. For this purpose, there are also other components, not shown in more detail, such as voltage dividers. The semiconductor switch 26 is actuated by means of the operational amplifier 28. If the electrical current flows from the DC voltage intermediate circuit 6 to the load 8, the semiconductor switch 26 is electrically blocking, i.e. open, whereas, in the case of an opposite current flow, the semiconductor switch 26 is set in the electrically conductive state. In summary, the semiconductor switch 26 is thus actuated as a function of the electrical voltage produced via the trigger 14. In this variant, it is ensured that even with a comparatively low resistance of the triggering coil 18, the electric current is conducted during a current flow from the load 8 to the DC voltage intermediate circuit 6 via the current direction-dependent component 20 and not via the trigger 14.FIG. 4 shows a simplified circuit diagram of an alternative embodiment of the circuit breaker 10. The switch 12 is designed as a double interrupter and has a contact bridge 30 which is mounted movably with respect to a busbar 32 having an opening. In this case, it is possible to bridge the opening of the busbar 32 by means of the contact bridge 30, with the result that the electrical current can be conducted via the busbar 32. By spacing the contact bridge 30 from the busbar 32, on the other hand, the opening is opened, so that a current flow via the busbar 32 is prevented.The contact bridge 30 of the switch 12 is driven by means of a drive 34, so that during operation of the drive 34 the contact bridge 30 is adjusted and thus the switch 12 is closed or opened. Consequently, the drive 34 is operatively connected to the contact bridge 30, namely mechanically coupled thereto, and the drive 34 acts on the switch 12. For energizing the control unit 36, and consequently the drive 34, the control unit 36 has two supply terminals 38 which are electrically contacted with a separate voltage supply, not shown in detail, by means of which a DC voltage of 12 V or 24 V is provided.The control unit 36 has, for example, an energy store in the form of a capacitor, which is charged by means of the voltage supply and which is connected electrically in parallel with a microcontroller of the control unit 36. Thus, by means of the energy store, any fluctuations in the electrical voltage and / or the electrical current of the voltage supply are intercepted, so that damage to the microcontroller is thereby avoided. It is also possible, on account of the energy store, to actuate the drive 34 at least once in the event of a failure of the voltage supply and in this way to open the switch 23. In a variant shown in more detail, the control unit 36 additionally has a charge pump, by means of which it is possible to increase the electrical voltage present at the capacitor in comparison with the electrical voltage provided by means of the voltage supply, with the result that the amount of energy stored by means of the energy store is increased. Safe operation of the drive 34 is thus always possible even if there is a complete failure of the voltage supply or the drive 34 is slightly blocked.The energization of the drive 34 is adjusted by means of the microcontroller, and the microcontroller is connected by signal technology to a current sensor 40, which is electrically connected in series with the switch 12. The current sensor 40 is designed as a shunt. Thus, by means of the current sensor 40, a measurement of the electric current carried by means of the switch 12 is made possible. Furthermore, the circuit breaker 10 has a plurality of voltage sensors 42, it being possible to measure the electrical voltage produced via the current sensor 40 by means of one of these and additionally the voltage produced via the switch 12 by means of another of these. By means of the other two, the electrical voltage on both sides of the switch 12 can be measured against the other pole of the DC intermediate circuit 6. All voltage sensors 42 are connected to the control unit 36 by signal technology.During operation, the microcontroller of the control unit 36 checks the change over time of the electrical voltages measured by means of the voltage sensors 42 and of the electrical current measured by means of the current sensor 40. If the change over time in the measured current corresponds to an increase and exceeds a specific limit value, the drive 34 is actuated by means of the control unit 36, so that the switch 12 is opened. The limit value is selected such that it is exceeded only in the event of a fault, namely in the event of an electrical short circuit of the load 8. The mechanical switch 26 is likewise actuated by means of the control unit 40 if a fault event is concluded on the basis of the electrical voltage detected by means of the voltage sensors 42, that is to say if the electrical voltage reaches a specific limit value. The limit values are different here for the two directions of the current flow, so that here too the triggering characteristic curve is dependent on the direction of the conducted electric current.FIG. 5 schematically shows the drive 34 in a sectional illustration along an axis 44. The drive 34 is designed as a "moving magnet actuator" and thus has two disk-like or drum-like holders 46 which are arranged concentrically with the axis 44 and spaced apart along the latter and are produced from a ferromagnetic material. Positioned between them is an annular short-circuiting plate 48 concentrically with respect to the axis 44, which is likewise produced from a ferromagnetic material. By means of the holders 46 and the short-circuiting plate 48, a hollow cylinder is thus formed, within which a further holder 50 made of a plastic is arranged and is mounted displaceably along the axis 44 by means of a guide, not shown in more detail. A rod 52 extending along the axis 44 is fastened to the holder 50, which is fastened to the contact bridge 30, either directly or via a mechanism not shown in more detail. Embedded in the cylinder-like further holder 50 is a cylindrical permanent magnet 54 which has two magnetic poles 56, each of which forms one of the ends of the permanent magnet 54 in a direction parallel to the axis 44.The drive 34 further has a drive unit 58 which comprises two electrical coils 60. Each of the electric coils 60 that are identical in construction to each other is wound on each of the holders 46, and these are electrically connected in parallel to each other. The drive 34 has a further drive unit 62, which comprises two further electrical coils 64, one of which is wound onto one of the electrical coils 60 and the other onto the remaining electrical coils 60. The two further electrical coils 64 are also electrically connected in parallel with one another. The two drive units 58, 62 are electrically contacted separately with the control unit 36 at least on one side, so that it is possible to separately supply current to the two drive units 58, 62 by means of the control unit 36.If the drive units 58, 62 are not energized, the permanent magnet 54 is pulled into a position substantially within the short-circuiting plate 48 due to the magnetic interaction with the short-circuiting plate 48 and the holders 46, wherein a force of approximately 30 N acts on the permanent magnet 48 and thus also on the further holder 50. With this force, the short-circuiting bridge 30 is thus also held in the desired position, namely in the position in which the switch 12 is closed.According to the respectively used triggering characteristic curve, the two drive units 58, 62 are energized by means of the control unit 36, so that the permanent magnet 54 is pressed away from one of the holders 46 along the axis 44 on account of the additionally created magnetic fields and is drawn toward the remaining holder 46. Thus, comparatively large forces act on the permanent magnet 54 and consequently also on the contact bridge 30 via the further holder 50 and the rod 52, so that the switch 12 is opened comparatively quickly.If the fault case is not present, and, for example, the energization of the load 8 is intended to be interrupted on the basis of a current operating cycle, only one of the drive units 58, 62 is energized by means of the control unit 36, with the result that the switch 12 is opened comparatively slowly. As a result, an electrical and also a mechanical load of the circuit breaker 10 is reduced.FIG. 6 shows a modification of the circuit breaker 10 shown in FIG. 4. In this variant, the construction of the drive 34 is left essentially unchanged. Also, the switch 12 is not changed, and the current sensor 40 and the voltage sensor 42 are still provided. In addition, the control unit 36 is also still present. However, by means of this, only an energization of the drive unit 58 of the drive 34 can take place. The further drive unit 62 is electrically connected in series with the switch 12 and is located between the latter and the current sensor 40. Thus, when the switch 12 is closed, the further drive unit 62 is energized substantially continuously, for which reason the magnetic field is established substantially continuously by means of the further electrical coils 64. The further electrical coils 64 are configured such that the magnetic field is not sufficient to move the permanent magnet 54. This only occurs when the electric current is at least three or five times the rated current, namely from the DC voltage intermediate circuit 6 to the load 8.FIG. 7 shows a further embodiment of the circuit breaker 10. The current sensor 40 and the voltage sensors 42 are again present, which, according to the preceding embodiment, are arranged with respect to the switch 12, which is likewise not changed. The control unit 36 is also present, which has the two supply connections 38. The control unit 36 is in turn used to supply current to the drive unit 58 of the drive 34, which is not modified. In addition, a subunit 66 is assigned to the control unit 36, which subunit can be configured as a separate structural unit, as shown in the example shown, or is integrated into the other components of the control unit 36. By means of the subunit 66, the further drive unit 62 is energized.Connected between the current sensor 40 and the switch 12 is an element 68 which has a variable resistance and which is adjusted by means of the subunit 66. The series circuit of element 68 and current sensor 40 is bridged by a series circuit of further current sensor 70 and subunit 66.If there is no fault, the element 68 is set such that the resistance provided is minimal. As a result, the electric current flows via the current sensor 40 and the element 68. As a result, the electric current no longer flows via the element 68 and the current sensor 40, but via the subunit 66, by means of which the further drive unit 62 is energized. As a result, the switch 12 is opened. Here, in addition, the drive unit 58 is also energized by means of the voltage supply. The trip characteristic curve, as a function of which the switch 12 is actuated, is in turn dependent on the direction of the electric current.The invention is not limited to the above-described embodiments. Rather, other variants of the invention can also be derived from this by the person skilled in the art without departing from the subject matter of the invention. In particular, all the individual features described in connection with the individual exemplary embodiments can also be combined with one another in another manner without departing from the subject matter of the invention.List of reference characters2 DC circuit 4 DC voltage source 6 DC voltage intermediate circuit 8 load 10 circuit breaker 12 switch 14 trigger 16 further trigger 18 trigger coil 20 latch 22 current direction-dependent component 24 diode 26 semiconductor switch 28 operational amplifier 30 contact bridge 32 bus bar 34 drive 36 control unit 38 supply connection 40 current sensor 42 voltage sensors 44 axis 46 holder 48 short-circuiting plate 50 further holder 52 rod 54 permanent magnet 56 pole 58 drive unit 60 electrical coil 62 further drive unit 64 further electrical coil 66 subunit 68 element 70 further current sensor

Claims

Circuit breaker (10) having a switch (12) which is actuated as a function of a trip characteristic curve, wherein the trip characteristic curve is dependent on a direction of a conducted electric current.Circuit breaker (10) according to Claim 1, characterized bya trip device (14) which is connected in series with the switch (12) and is bridged by means of a current-direction-dependent component (22).The circuit breaker (10) of claim 2, characterized in that the trip (14) includes an electrical trip coil (18) electrically connected in series with the switch (12).Circuit breaker (10) according to claim 2 or 3, characterized in that a further trigger (16) is electrically connected in series with the switch (12).Circuit breaker (10) according to one of Claims 2 to 4, 10 characterised in that the current-direction-dependent component (22) comprises a diode (24).Circuit breaker (10) according to one of Claims 2 to 5, characterized in that the current-direction-dependent component (22) has a semiconductor switch (26) which is actuated as a function of an electrical voltage arising via the trip (14).Circuit breaker (10) according to Claim 1, characterized bya drive (34) which acts on the switch (12) and is actuated as a function of the direction by means of a control unit (36).Use of a circuit breaker (10) according to one of Claims 1 to 7 for protecting a load (8) in a direct current circuit (2).

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