WO2005086309A1

WO2005086309A1 - Method and circuit arrangement for activating low-voltage power switches

Info

Publication number: WO2005086309A1
Application number: PCT/DE2005/000382
Authority: WO
Inventors: Marc Liebetruth; Andreas Pancke; Wolfgang Röhl; Manfred Schiller
Original assignee: Siemens Aktiengesellschaft
Priority date: 2004-03-04
Filing date: 2005-03-02
Publication date: 2005-09-15
Also published as: DE102004011027A1

Abstract

The inventive method and circuit arrangement for activating low-voltage power switches are provided with energy converters for a triggering energy for switching-off the low-voltage power switch of a network (5) monitored thereby, an excess-current tripping device and at least two trigger magnets (9) which act together on a latching unit such as, for example a tripping shaft. According to said invention, the trigger magnets (9) are controlled in a temporally graduated manner. In the corresponding circuit arrangement, a time stage (102, 10n) is disposed between the excess-current tripping device and the second tripping magnet and each following tripping magnet (92...9n). The advantage of the temporal graduation lies in that in order to activate the second tripping magnet or the following tripping magnet (92...9n), the energy is still supplied via the energy converters as far as a switching motion is produced only after the activation of the last tripping magnet (92...9n).

Description

description

Method and circuit arrangement for tripping low-voltage circuit breakers

The invention relates to a method for tripping low-voltage circuit breakers with energy converters, which relate the tripping energy for the opening process of the low-voltage circuit breaker from the network monitored by it, an overcurrent release and at least two tripping magnets. The invention further relates to an associated circuit arrangement.

Low-voltage circuit breakers, with which consumers downstream of the circuit breaker are monitored for short-circuit currents and overcurrents, have an overcurrent release whose switch-off command acts on a tripping magnet, with which a latch is released and then the opening movement of the main current contacts in via a spring drive and a gear Gear is set. A force is added to the force of the drive spring, which is caused by the current due to the loop effect on the main current contacts. This force is desirable with regard to the opening effect at the main current contacts. At the same time, however, the inhibition on the latch is increased, which requires an increased release force of the release magnet to overcome the inhibition. There is a certain relationship (squared depending on the current) between the short-circuit current and the release force of the release magnet.

Since the tripping force of a tripping magnet, based on its construction volume, cannot be increased arbitrarily and thus an otherwise possible increase in the permissible short-circuit current If measures were to be made impossible, measures have already been considered which should nevertheless make it possible to increase the release force. For example, it has already been suggested (technology report from Siemens AG, vol. 99, October 2003) to use at least two release magnets that act together on the latch, for example a release shaft. The advantage of the arrangement is that there is no need to develop a release magnet with increased release force, which would result in a changed switch design. Two tripping magnets are usually easier to accommodate in the volume of the circuit breaker than a single large one. With many switches, the construction volume is also available for another trigger magnet. The arrangement can be supplemented by the fact that, with a low switch-off current, in which only a limited amount of energy is available via the energy converters and, on the other hand, only a small release force is required, only one release magnet is actuated.

However, the switch-off continues with the available energy, which is now only distributed to at least two trigger magnets. The current low-voltage circuit breakers work without the supply of external energy, which means that they draw their energy directly from the monitored network via energy converters. The energy is buffered, however, if the circuit breaker is opened after the main power contacts are opened, no more energy is supplied due to the current interruption. It is also not possible to increase the energy by increasing the power of the energy converter and / or the capacitance of the buffer capacitor without increasing the construction volume of these components and thus necessarily changing the switch design. A trigger is also known from US Pat. No. 5,369,542 A, the trigger magnet of which is fed directly, that is to say without intermediate buffering of the energy, by a current converter and has two windings. One winding has relatively few turns with a large cross section, the other, however, has a relatively large number of turns with a smaller cross section. Depending on the respective flowing secondary current of the current transformer, one or the other winding of the tripping magnet is driven by an automatic control. However, the solution requires correspondingly large current transformers and special tripping magnets, which also have a large construction volume.

The invention has for its object to provide a way to change the triggering, with which an inhibition due to a high short-circuit current at the latch of the trigger can be controlled.

According to the invention, the object is achieved by a method having the features of claim 1. A suitable circuit arrangement for carrying out the method is specified in claim 8. Appropriate configurations are the subject of the subclaims.

The at least two existing release magnets are then controlled in a staggered manner in time. When the first release magnet is actuated, the element which inhibits the manual transmission, for example a profiled release shaft, which interacts with an edge of a release lever, is triggered, which initially overcomes the static friction and only sliding friction is effective. With the actuation of the second or even further trigger magnet, this element then moved to a point where the latch is released and the gearbox movement is started.

The electronic overcurrent release of the circuit breaker is expediently provided with at least two outputs. They each control a trigger magnet. The trigger magnets work mechanically coupled, for example on a trigger shaft. They can be arranged mechanically next to one another or one behind the other.

In a variant according to the invention it can be provided that the delay time for the at least two tripping magnets present is adjusted as a function of the level of the current to be switched off in the network, in order, for example, to switch off quickly in the event of high short-circuit currents. The time constant of the buffer capacitor must be taken into account for a minimum delay time.

The staggering over time has the advantage that energy is still supplied for the actuation of the second or further trigger magnet via the energy converters, since the switching movement takes place only after the last trigger magnet has been actuated and a primary current continues to flow as long. The switch can remain largely unchanged mechanically, that is to say in particular with regard to the power and design of the current transformers and the tripping magnets.

If necessary, an additional measure can be provided. If not all magnets are actuated in the event of a sudden interruption in the short-circuit current, for example due to the faster opening of an upstream circuit breaker, and the tripping system is designed in such a way that generally only the force of several tripping magnets is triggered for safe tripping is sufficient, it makes sense to use the triggering of a trigger magnet as an occasion for the compulsory triggering of the further trigger magnet or magnets. This forced release takes place immediately after the activation current returns.

In all circuits, the microprocessor of the overcurrent release should be put into sleep mode after activation of the time stages. This means that its current consumption is drastically reduced so that the release magnets and the time stages can be supplied with the small amount of energy available ,

A corresponding circuit arrangement for performing the method provides that a time stage is connected between the overcurrent release and the second and further release magnets.

The additional measure for forced tripping described above after a loss of the mains voltage can be implemented in that the tripping magnets each have an input of a

Circuit for inductance measurement are connected, the outputs of which correspond to the number of release magnets are led to a logic circuit with which a release signal for the release magnets is generated if a release has been reported for the upstream release magnets by the inductance measurement.

Alternatively, a non-volatile memory which is independent of the mains voltage and stores the switch-off command of the overcurrent release can be arranged between the overcurrent release and the first release magnet and the time stages. The invention will be explained in more detail below using exemplary embodiments. In the accompanying drawings: FIG. 1 shows a basic circuit diagram of the trigger circuit;

2 shows a basic circuit diagram of the trigger circuit with additional forced triggering and FIG. 3 shows a basic circuit diagram of the trigger circuit with a further variant of the additional forced triggering.

FIG. 1 shows the overcurrent release of a low-voltage circuit breaker in a basic circuit diagram. Current converters 1 serve as energy suppliers for an electronic overcurrent release, the outputs of which are led to a microprocessor 4 of the overcurrent release 1 via bridge rectifiers 2, which are only indicated here, and a storage capacitor 3. The currents in the network 5 are monitored via current sensors 6, for example Rogowski coils, the outputs of which are led to the microprocessor 4 via measuring amplifiers 7. The microprocessor 4 compares the current mains currents with preset values and, if necessary, brings about an instantaneous or delayed tripping of the circuit breaker.

The output of the microprocessor 4 is connected via a first switching transistor 8χ to a first trigger magnet 9 _τ and with the interposition of a time stage 10 ₂ to a second switching transistor 8 ₂ and a second trigger magnet 9 and, if appropriate, in the same way via further time stages 10 _n and switching transistors 8 _n a trigger magnet 9 _n switched. For the setting of the delay time of the time stages 10ι ... l0 _n , the charging capacity and the time constant of the storage capacitor 3 must be taken into account. Due to their staggered actuation, the release magnets 9χ ... 9 _n guarantee a safe overcoming of the inhibition of the gearbox and thus ensure a safe switch-off even with higher currents in the network 5.

An improvement compared to the trigger circuit according to FIG. 1 results with the circuit according to FIG. 2. Only the circuit part on which a trigger pulse of the microprocessor 4 acts is shown in FIG. 2. If sufficient energy is available in the storage capacitor 3, it makes sense to control the next trigger magnet 9 ₂ immediately after triggering the trigger magnet 9χ in order to trigger the trigger as quickly and as energy-efficiently as possible. This is done by querying the switching status of all tripping magnets, here the tripping magnets 9χ ... 9 ₃ . One way of querying the status is, for example, to monitor the inductance of the tripping magnets 9χ ... 9 ₃ according to the circuit shown in FIG. As soon as a trigger magnet 9 ... 9 ₃ is activated and the plunger in the trigger magnet 9χ ... 9 ₃ has moved, the inductance of the trigger magnet 9χ ... 9 _{3 changes} . The change in inductance can be detected with an active circuit for inductance measurement 11. Such a circuit is known per se. It is based on the fact that a short voltage pulse is given to the tripping magnets 9ι --- 9 ₃ , the voltage level of which is selected so that there is no unwanted tripping of the low-voltage circuit breaker. The current caused by the voltage pulse has a typical course (time constant) for the inductance in the respective operating state, which is detected with the circuit for inductance measurement 11. Depending on the level of inductance, the circuit for inductance measurement 11 outputs a high or low signal for the respective release magnet 9χ ... 9 ₃ to a logic circuit 12 with the logic modules 12χ ... l2 ₃ . The logic circuit 12 works in the following way:

As soon as a switch-off command is issued by the microprocessor 4 of the overcurrent release, the triggering of the triggering magnet 9 wird is excited via the first logic module 12 sofern, provided that the inductance measurement 11 for the triggering magnets 9 ₂ and 9 ₃ shows that these are not activated. After the time stage 10 ₂ has elapsed, the trigger signal for the trigger magnet 9 _{2 is} output, provided the trigger magnet 9χ, but not the trigger magnet 9 ₃ , has triggered. After the time stage 10 ₃ has elapsed, the trigger magnet 9 _{3 is} activated. Previously, the state of the release magnets 9χ and 9 _{2 was} queried.

The procedure is expediently monitored by the microprocessor 4. If an error occurs during the process, an error signal should be sent to the microprocessor 4, which must then react to it, for example with a new switch-off command.

If, during this sequence, the voltage in the network 5 disappears because, for example, an upstream circuit breaker has already switched, the microprocessor 4 must query the state of the release magnets 9χ ... 9 ₃ after the voltage has returned to “all release magnets 9χ ... 9 ₃ triggered ? ". If this is not the case, a new switch-off command is issued. If the trigger magnet 9χ has already triggered, the trigger magnet 9 is actuated - as described above - after the time step 10 _{2 has} elapsed and then the trigger magnet 9 ₃ . Have the training loose magnets 9χ and 9 _{2 are} already triggered, the trigger magnet 9 _{3 is} activated after the time step 10 ₃ .

The circuit according to FIG. 3 represents a compromise between the trigger circuits according to FIG. 1 and FIG. 2. Here the triggering of the trigger magnets 9χ... 9 _{3 is registered} in a voltage-independent, non-volatile memory 13. When the low-voltage circuit breaker has been initiated but has been aborted, the trip magnets 9χ ... 9 ₃ are triggered immediately after the voltage in the network 5 returns by the trigger signal stored in the non-volatile memory 13, staggered by the time stages 10χ, 10 ₂ . The memory 13 is reset via a time stage 10 _r . For safety reasons it can be provided that the triggering of the tripping magnets 9χ ... 9 _{3 is} repeated until the current is interrupted by the switching of the circuit breaker.

Claims

claims

1. Method for triggering low-voltage circuit breakers with energy converters, which draw the release energy for the opening process of the low-voltage circuit breaker from the network monitored by it, an energy buffer and an overcurrent release and at least two release magnets, characterized in that the release magnets (9) can be controlled in a staggered manner.

2. The method of claim 1, d a d u r c h g e k e n n z e i c h n e t that the delay time between the staggered tripping pulses of the tripping magnets (9) is adjusted depending on the amount of current to be switched off in the monitored network (5).

3. The method according to claim 1 or 2, characterized in that the tripping magnets (9) are monitored for their operating state and, when one of the tripping magnets (9) is switched, a forced triggering of the low-voltage power switch is initiated by actuating the remaining tripping magnets (9) ,

4. The method of claim 3, d a d u r c h g e k e n n z e i c h n e t that the monitoring of the operating state of the tripping magnets

(9) by monitoring their inductance.

5. The method according to claim 3, characterized in that the trip command of the overcurrent release is stored in a non-volatile memory (13) which is independent of the line voltage and after a voltage failure in the monitored network (5) the store (13) forcibly triggers the low-voltage circuit breaker by actuating the release magnets ( 9) is initiated.

6. The method according to any one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that the forced release is repeated until the low-voltage circuit breaker has tripped.

7. The method according to any one of the preceding claims, characterized in that the overcurrent release is built up using a microprocessor (4), between the microprocessor (4) and the second and further release magnets (9) a time stage (10) is switched and after a the microprocessor (4) has been commanded to switch off and the

Time stages (10) of the microprocessor (4) is put into a sleep mode.

8. Circuit arrangement for triggering low-voltage circuit breakers with energy converters (1), which draw the release energy for the opening process of the low-voltage circuit breaker from the network (5) monitored by it, an energy buffer (3) and an overcurrent release and at least two release magnets (9χ ... 9 _n ) for carrying out the method according to one of the preceding claims, characterized in that that a time step (10 ₂ ... 10 _n ) is connected between the overcurrent release and the second and further release magnets (9 ₂ ... 9 _n ).

9. Circuit arrangement according to claim 8, characterized in that the release magnets (9χ ... 9 _n ) are each connected to an input of a circuit for inductance measurement (11), the outputs of which correspond to the number of release magnets (9χ ... 9 _n ) a logic circuit (12) are guided, with which a trigger signal for the trigger magnets (9 ₂ - .. 9 _n ) is generated if for the upstream trigger magnets (9χ ... 9 _n -ι) by the inductance measurement (11) Tripping is reported.

10. The circuit arrangement according to claim 8, characterized in that between the overcurrent release and the first release magnet (9 _α ) and the time stages (10 ₂ ... 10 _n ) a non-volatile, independent of the mains voltage, storing the switch-off command of the overcurrent release Memory (13) is arranged.

11. Circuit arrangement according to claim 10, characterized in that between the last time stage (10 _n ) and the reset input of the memory (13) a time stage triggering a reset (10 _re s) is arranged when this time stage (10 _n ) has expired.