DE102018200714B4 - RCDs and procedures - Google Patents

Abstract

Residual current circuit breaker (FI) for a low-voltage circuit, having: - several conductors (L1, L2, L3, N) of the low-voltage circuit to be protected, which can be opened or closed by contacts (K1, K2, K3, KN), - a mechanism (M ) for opening and closing the contacts (K1, K2, K3, KN),- a holding magnet release (A) connected to the mechanism (M), for opening the contacts (K1, K2, K3, KN),- a first Summation current transformer (W1), the primary side of which is formed by the conductors (L1, L2, L3, N) and which has a first secondary winding (SW1),- a first connection (V1) between a first connection of the first secondary winding (SWA1) and a first connection (AA1) of the holding magnet release (A), - a second connection (V2) between a second connection of the first secondary winding (SWA2) and a second connection (AA2) of the holding magnet release (A), - a second summation current transformer ( W2), the primary side of which is also formed by the conductors (L1, L2, L3, N) and which has a second secondary winding (SW2),- an evaluation unit (E2) connected to the second secondary winding (SW2), with at least two outputs, in which a first output is connected to the first connection (AA1) and a second output is connected to the second connection (AA2) of the holding magnet release (A), the first or second connection having a switching contact (SK), characterized in that the first and second connection (V1, V2) between the first secondary winding (SW1) and the holding magnet release (A) has a storage circuit (E1).

Description

The invention relates to a residual current circuit breaker for a low-voltage circuit according to the preamble of patent claim 1 and a method for a residual current circuit breaker for a low-voltage circuit according to the preamble of patent claim 8.

Residual current circuit breakers for electrical circuits, in particular for low-voltage circuits or systems, are well known. Residual current circuit breakers are also referred to as residual current circuit breakers or residual current devices, RCD for short.

Low voltage means voltages up to 1000 volts AC and/or 1500 volts DC. Low voltage means, in particular, voltages that are greater than extra-low voltage, with values of 25 volts or 50 volts AC and 60 volts or 120 volts DC.

By circuits, particularly for low voltage, is meant circuits for currents up to 6300 amps, more specifically currents up to 1600 amps, 1200 amps, 630 amps, 125 amps or 63 amps. The current values mentioned refer in particular to nominal and/or cut-off currents, i.e. the maximum current that is normally carried through the circuit or at which the electrical circuit is usually interrupted, for example by a protective device such as a miniature circuit breaker or circuit breaker.

Residual current circuit breakers are used in particular for rated current ranges of or up to 16, 25, 40, 63, 80 or 125 amperes.

Residual current circuit breakers determine the total current in an electrical circuit, which is normally zero, and interrupt the electrical circuit if a residual current value is exceeded, i.e. a total current that is not equal to zero and exceeds a specific (differential) current value or residual current value.

Almost all previous residual current circuit breakers have a summation current transformer whose primary winding is formed by the conductors of the circuit and whose secondary winding delivers the total current, which is used directly or indirectly to interrupt the electrical circuit.

For this purpose, two or more conductors, mostly outgoing and return conductors or external and neutral conductors in a single-phase AC network, all three external conductors or all three external conductors and the neutral conductor in a three-phase AC network, are connected by a core usually made of ferromagnetic material, led current transformer. Only the differential current, i.e. a current deviating from the outward and return current, from the conductors is converted. Normally, i.e. in a fault-free or fault-free state, the total current in an electrical circuit is zero. In this way, fault currents can be detected.

If, for example, a current flows to earth on the energy sink side or consumer side, this is referred to as a residual current. A fault occurs, for example, when there is an electrical connection from a phase conductor of the electrical circuit to ground. For example, when a person touches the phase conductor. Then a part of the electrical current does not flow back via the neutral conductor or zero conductor as usual, but via the person and the earth. This residual current can now be detected with the help of the summation current transformer, since the sum of the current flowing in and flowing back is not equal to zero. A relay or a holding magnet trigger, for example with a connected mechanism, causes the circuit to be interrupted, for example at least one, part or all of the lines. Residual current circuit breakers for detecting AC residual currents are generally known from the publication DE 44 32 643 A1 known.

The main function of residual current circuit breakers is to protect people from electrical currents (electric shock), as well as systems, machines or buildings from fire caused by electrical insulation faults.

If the residual current circuit breaker or its summation current transformer is designed in such a way that the energy on the secondary side is sufficient to actuate a tripping unit or an interruption unit or a trigger, then such residual current circuit breakers are called mains voltage-independent; otherwise depending on the mains voltage.

Residual current circuit breakers are generally designed to be independent of the mains voltage.

If a power pack is provided for the power supply of a residual current detection system, it is a mains voltage-dependent residual current circuit breaker. These are required, for example, to detect residual currents in DC voltage networks and mixed DC/AC networks or in circuits with high frequencies.

A residual current circuit breaker essentially consists of the functional groups summation current transformer, tripping circuit, holding magnet release, mechanics and contacts. Furthermore, a test circuit with test button and test resistor is usually provided. The functionality of the residual current circuit breaker or the residual current protective device can be checked using the test button.

There are different types of residual current circuit breakers, which are designated by letters or letter combinations, such as AC, A, F, G, K, S, B, B+. Each type captures a specific type of fault current. Residual current circuit breakers with 2 poles for phase and neutral conductors (L+N), 3 poles for three phase conductors (L1, L2, L3) and 4 poles for three phase conductors and neutral conductors (L1, L2, L3, N) are currently known.

For example, type AC only detect purely sinusoidal fault currents. Type A detects both pure sinusoidal alternating currents and pulsating DC residual currents. Type F are mixed-frequency sensitive residual current protective devices. They record all types of fault currents, such as type A. They are also suitable for detecting fault currents that consist of a mixture of frequencies up to 1 kHz. Type K includes the characteristics of type A, but there is a short delay in its switch-off behavior. Type S are selective residual current circuit breakers, which can be graded in terms of the rated residual current and the tripping time.

Type B residual current protective devices are used not only to detect type F residual current types, but also to detect smooth DC residual currents. They are also suitable for residual currents with frequencies up to 2 kHz.

The same conditions apply to type B+ residual current protective devices as to type B residual current protective devices. Only the frequency range for detecting residual currents applies to an extended range of up to 20 kHz. The triggering takes place within this frequency range below 420 mA.

Residual current circuit breakers with a mains-voltage-independent and a mains-voltage-dependent part within one device have recently become available. For example, devices of type B or B+ can have such a configuration.

On the one hand, it is problematic if an existing residual current does not lead to the tripping or interruption of the circuit, and on the other hand, if undesired early tripping occurs.

In systems with frequency converters, in addition to protection against AC and DC insulation faults, the system availability should be high. This means that false triggering, e.g. as a result of technically related leakage currents, should be avoided.

Especially with type B and B+ RCCBs, there are often two independent detection circuits, e.g. early triggers) can become.

The German Offenlegungsschrift DE 10 2012 111 615 A1 discloses a residual current circuit breaker according to the preamble of claim 1. In a residual current circuit breaker (1) with a sensor arrangement (2) for detecting a fault current independently of the mains voltage, and a tripping circuit (3) independent of the mains voltage, the sensor arrangement (2) having a summation current transformer (4) with a secondary winding ( 5), which secondary winding (5) is connected to the tripping circuit (3) in terms of circuitry, it is proposed that the residual current circuit breaker (1) also has: an electrical mains voltage output (6), an electrical input (7) which is connected to the tripping circuit ( 3) is connected in terms of circuitry, and an electrical circuit breaker interface (8), which is connected in terms of circuitry to a tertiary winding (9) arranged on the summation current transformer (4). Furthermore, a tripping module for connection to the residual current circuit breaker is proposed.

The object of the present invention is to improve a residual current circuit breaker of the type mentioned at the outset, in particular to avoid premature tripping.

This object is achieved by a residual current circuit breaker having the features of patent claim 1 and by a method according to patent claim 7 .

• - mehrere Leiter (mit mehrere Leiter sind mindestens zwei Leiter gemeint) eines zu schützenden Niederspannungsstromkreises, die durch Kontakte öffenbar bzw. schließbar sind,
• - eine Mechanik zum Öffnen und (oder) Schließen der Kontakte,
• - einen mit der Mechanik verbundenen Haltemagnet-Auslöser, zum Öffnen der Kontakte,
• - einen ersten Summenstromwandler, dessen Primärseite durch die Leiter gebildet ist und der eine erste Sekundärwicklung aufweist,
• - eine erste Verbindung zwischen ersten Anschluss der ersten Sekundärwicklung und ersten Anschluss des Haltemagnet-Auslösers,
• - eine zweite Verbindung zwischen zweiten Anschluss der ersten Sekundärwicklung und zweiten Anschluss des Haltemagnet-Auslösers,
• - einen zweiten Summenstromwandler, dessen Primärseite ebenfalls durch die Leiter gebildet ist und der eine zweite Sekundärwicklung aufweist,
• - eine mit der zweiten Sekundärwicklung verbundenen Auswerteeinheit, mit mindestens zwei Ausgängen, bei der ein erster Ausgang mit dem ersten Anschluss und ein zweiter Ausgang mit dem zweiten Anschluss des Haltemagnet-Auslösers verbunden ist.

According to the invention, a residual current circuit breaker for a low-voltage circuit is provided, having:

• - several conductors (with several conductors at least two conductors are meant) of a low-voltage circuit to be protected, which can be opened or closed by contacts,
• - a mechanism for opening and (or) closing the contacts,
• - a holding magnet trigger connected to the mechanism to open the contacts,
• - a first summation current transformer, the primary side of which is formed by the conductors and which has a first secondary winding,
• - a first connection between the first connection of the first secondary winding and the first connection of the holding magnet release,
• - a second connection between the second connection of the first secondary winding and the second connection of the holding magnet release,
• - a second summation current transformer, the primary side of which is also formed by the conductors and which has a second secondary winding,
• - An evaluation unit connected to the second secondary winding, with at least two outputs, in which a first output is connected to the first connection and a second output is connected to the second connection of the holding magnet release.

The first or (and) second connection has a switching contact.

This has the advantage that a detection circuit, in particular a detection circuit with a large detection tolerance band, can be switched off.

The connections between the first secondary winding and the holding magnet release feature a memory circuit.

This has the advantage that the energy of the first summation current transformer is stored when fault currents are present, and when a threshold value is reached, all of the energy is sent to the holding magnet release in order to reliably trip the residual current circuit breaker.

Advantageous refinements of the invention are specified in the dependent claims.

In an advantageous embodiment of the invention, the evaluation unit receives an energy supply through at least part of the conductors, for example through a power pack, in particular a switched-mode power pack.

This has the particular advantage that a simple energy supply is available, so that a detection circuit that is independent of the mains voltage and a detection circuit that is dependent on the mains voltage can be implemented.

In an advantageous embodiment of the invention, the evaluation unit has a microprocessor.

This has the particular advantage that a simple microprocessor-based evaluation is made possible, which enables a variety of functions.

In an advantageous embodiment of the invention, a trigger control is provided, which is in particular part of the evaluation unit.

This has the particular advantage that reliable tripping in a residual current circuit breaker is made possible.

In an advantageous embodiment of the invention, the switching contact is an opener that can be actuated by the evaluation unit.

This has the particular advantage that both detection circuits are active when the residual current circuit breaker is switched on or when the voltage is switched on to the conductors of the low-voltage circuit. Only when the second detection circuit is fully available, for example the mains voltage-dependent detection circuit, which can have greater accuracy, i.e. a more precise detection tolerance band, due to a power supply, is the first detection circuit switched off.

• - ein erster und ein zweiter Detektionskreis vorgesehen ist,
• - jeder Detektionskreis einen Differenzstrom der Leiter ermittelt,
• - bei Überschreitung eines Differenzstromschwellwertes (insbesondere eines Detektionskreises) ein Auslösesignal zu den Anschlüssen eines Haltemagnet-Auslösers zur Unterbrechung der Leiter des Niederspannungsstromkreises gesendet wird,
• - dass bei Vorliegen der Funktionalität des zweiten Detektionskreises der erste Detektionskreis inaktiv geschaltet wird.

According to the invention, a corresponding method for a residual current circuit breaker for a low-voltage circuit with several conductors is also claimed, in which:

• - a first and a second detection circuit is provided,
• - each detection circuit detects a differential current of the conductors,
• - if a differential current threshold (in particular a detection circuit) is exceeded, a trip signal is sent to the terminals of a holding magnet trip to interrupt the conductors of the low-voltage circuit,
• - that when the functionality of the second detection circuit is present, the first detection circuit is switched to inactive.

In particular, the first detection circuit is a line voltage-independent detection circuit and the second detection circuit is a line voltage-dependent detection circuit.

All of the configurations, both in dependent form referring back to claim 1 or 7 and also referring back only to individual features or feature combinations of patent claims, bring about an improvement in a residual current circuit breaker, in particular to avoid false or premature tripping.

The characteristics, features and advantages of this invention described and the manner in which they are achieved will become clearer and more clearly understood in connection with the following description of the exemplary embodiments, which are explained in more detail in connection with the drawing.

• 1 eine erste Darstellung eines Fehlerstromschutzschalters,
• 2 eine zweite Darstellung eines Fehlerstromschutzschalters,
• 3 eine dritte Darstellung eines Fehlerstromschutzschalters,
• 4 eine vierte Darstellung eines Fehlerstromschutzschalters,
• 5 eine fünfte Darstellung eines Fehlerstromschutzschalters,
• 6 eine sechste Darstellung eines Fehlerstromschutzschalters.

The drawing shows:

• 1 a first representation of a residual current circuit breaker,
• 2 a second representation of a residual current circuit breaker,
• 3 a third representation of a residual current circuit breaker,
• 4 a fourth representation of a residual current circuit breaker,
• 5 a fifth representation of a residual current circuit breaker,
• 6 a sixth representation of a residual current circuit breaker.

• - mehrere Eingangsanschlüsse 1, 3, 5, NE, für den energiequellenseitigen Anschluss des Fehlerstromschutzschalters an eine Energiequelle, beispielsweise einen Niederspannungsstromkreis bzw. ein Niederspannungsnetz;
• - mehrere Ausgangsanschlüsse 2, 4, 6, NA für den energiesenkenseitigen Anschluss des Fehlerstromschutzschalters an eine Energiesenke, beispielsweise einen Verbraucher;
• - mehrere Leiter L1, L2, L3, N eines zu schützenden Niederspannungsstromkreises, wobei ein erster Leiter L1 zwischen erstem Eingangsanschluss 1 und ersten Ausgangsanschluss 2 geschaltet ist, dito ein zweiter Leiter L2 zwischen zweitem Eingangsanschluss 3 und zweitem Ausgangsanschluss 4, ein dritter Leiter L3 zwischen drittem Eingangsanschluss 5 und drittem Ausgangsanschluss 6 geschaltet ist, ein vierter Leiter N, z.B. Neutralleiter, zwischen vierten Eingangsanschluss NE und vierten Ausgangsanschluss NA geschaltet ist;
• - wobei z.B. die ersten bis dritten Leiter L1, L2, L3 Phasenleiter und der vierte Leiter N ein Neutralleiter bzw. Nullleiter eines beispielsweise Dreiphasenwechselstromkreises sind;
• - mehrere, z.B. erste bis vierte Kontakte K1, K2, K3, KN mit denen die ersten bis vierten Leiter L1, L2, L3, N elektrisch

geöffnet oder geschlossen werden können, wobei ein Kontakt einem Leiter zugeordnet ist;

• - eine mit den Kontakten K1, K2, K3, KN verbundene Mechanik M, zum Öffnen und Schließen der Kontakte K1, K2, K3, KN;
• - einen mit der Mechanik M verbundenen Haltemagnet-Auslöser A, der im Wesentlichen eine Öffnung der Kontakte K1, K2, K3, KN bewirkt;
• - einen ersten Summenstromwandler Wl, dessen Primärseite durch die Leiter L1, L2, L3, N gebildet ist, wobei die Leiter durch den Summenstromwandler W1 hindurchgeführt sind, der Summenstromwandler beispielsweise als Ringkern, z.B. aus ferromagnetischen Material ausgeführt ist, und der eine erste Sekundärwicklung SW1 aufweist, die beispielsweise mehrere Windungen n aufweist;
• - eine erste Verbindung V1 zwischen ersten Anschluss der Sekundärwicklung SWA1 und ersten Anschluss AA1 des Haltemagnet-Auslösers A;
• - eine zweite Verbindung V2 zwischen zweiten Anschluss der Sekundärwicklung SWA2 und zweiten Anschluss AA2 des Haltemagnet-Auslösers A.

1 shows a schematic representation of a residual current circuit breaker FI, having:

• - Several input connections 1, 3, 5, NE, for the energy source-side connection of the residual current circuit breaker to an energy source, for example a low-voltage circuit or a low-voltage network;
• - Several output terminals 2, 4, 6, NA for the energy sink side connection of the residual current circuit breaker to an energy sink, such as a consumer;
• - Several conductors L1, L2, L3, N of a low-voltage circuit to be protected, a first conductor L1 being connected between the first input terminal 1 and the first output terminal 2, ditto a second conductor L2 between the second input terminal 3 and the second output terminal 4, a third conductor L3 between third input terminal 5 and third output terminal 6 is connected, a fourth conductor N, eg neutral conductor, is connected between fourth input terminal NE and fourth output terminal NA;
• - Wherein, for example, the first to third conductors L1, L2, L3 are phase conductors and the fourth conductor N is a neutral conductor or zero conductor of, for example, a three-phase alternating current circuit;
• - Several, eg first to fourth contacts K1, K2, K3, KN with which the first to fourth conductors L1, L2, L3, N electrically

can be opened or closed, with a contact associated with a conductor;

• - A mechanism M connected to the contacts K1, K2, K3, KN for opening and closing the contacts K1, K2, K3, KN;
• - A holding magnet trigger A connected to the mechanism M, which essentially causes the contacts K1, K2, K3, KN to open;
• - A first summation current transformer Wl, the primary side of which is formed by the conductors L1, L2, L3, N, the conductors being passed through the summation current transformer W1, the summation current transformer being designed, for example, as a toroidal core, for example made of ferromagnetic material, and which has a first secondary winding SW1 has, for example, has a plurality of turns n;
• - A first connection V1 between the first connection of the secondary winding SWA1 and the first connection AA1 of the holding magnet release A;
• - A second connection V2 between the second connection of the secondary winding SWA2 and the second connection AA2 of the holding magnet release A.

It is essential that the secondary winding SW1 is connected to the holding magnet release A, so that a fault current induced in the secondary winding SW1 which, for example, exceeds a fault current value, causes the holding magnet release to be triggered, for example by energizing the holding magnet, for example as a relay so that a trip, i.e. an interruption of at least one, part or all of the contacts, is effected so that the electrical circuit is broken. The interruption can be supported by a mechanism M, as shown.

The first summation current transformer SW1 is designed together with the holding magnet release A in the form of a mains voltage-independent residual current circuit breaker, i.e. there is a first detection circuit in the form of a mains voltage-independent detection circuit.

Furthermore, a test circuit, having a series connection of a key T and a resistor R, is located. The series circuit is connected to one conductor before the summation current transformer, in the example the fourth conductor N, and after the summation current transformer to another conductor, in the example the third conductor L3; where the series circuit is routed past the summation current transformer. With the series connection or the test circuit, a functional test of the summation current transformer or residual current circuit breaker FI can be carried out by pressing the T button to generate an artificial fault current (total current of the conductors through the summation current transformer is not equal to zero).

2 shows a representation according to 1 , with the difference that a second summation current transformer W2 is provided, the primary side of which is also formed by the conductors L1, L2, L3, N and which has a second secondary winding SW2. An evaluation unit E2 connected to the second secondary winding SW2 with at least two outputs is provided, in which the first output is connected to the first connection V1 - or to the first connection (AA1) of the holding magnet release A - and the second output is connected to the second connection V2 - or with the second terminal (AA2) of the holding magnet release A - is connected in parallel to the terminals or inputs of the holding magnet release A and parallel to the terminals of the first secondary winding SW1. An output or connection could also be realized by a ground connection or ground line, GND for short.

The second summation current transformer SW2 can, for example, be designed for a different type of fault current than the first summation current transformer SW1. The second summation current transformer SW2 can be designed, for example, together with the evaluation unit E2 in the form of a mains voltage-dependent residual current circuit breaker. In the example, a second detection circuit is formed here in the form of a line voltage-dependent detection circuit. For example, the evaluation unit E2 can carry out an evaluation in the case of smooth DC fault currents.

In the example according to 2 the evaluation unit E2 is connected to the first to fourth conductors L1, L2, L3, N inside the residual current circuit breaker, for example to supply energy to the evaluation unit E2. For this purpose, the evaluation unit can have a power pack, in particular a switched-mode power pack.

In the example of 2 a consumer or energy sink ES is connected to the first to fourth output terminals 2, 4, 6, NA. Furthermore, to the first to fourth input terminals 1, 3, 5, NE, a power grid or energy source EQ. Furthermore, a further conductor PE, for example a protective conductor, can be provided, as shown.

Likewise, the mains or energy source EQ can be grounded, as shown.

3 shows a representation according to 2 , with the difference that a storage circuit E1 is connected between the first secondary winding W1 and holding magnet release A, ie the first and second connection V1, V2 between the first secondary winding W1 and holding magnet release A has the storage circuit E1. In this case, the evaluation unit E2 is connected to the output of the memory circuit E1 on the holding magnet release side.

4 shows a representation according to 3 , with the difference that details of the evaluation unit E2 are shown. The evaluation unit E2 has a power pack PS which is connected to at least some of the conductors, in particular to the first to fourth conductors L1, L2, L3, N. The power pack is used to supply energy to at least some of the units of the residual current circuit breaker.

The evaluation unit E2 has a microprocessor MCU as the central control and evaluation unit. The microprocessor MCU is connected to the second secondary winding SW2, for example, via a signal processing unit SA.

The evaluation unit E2 has a trigger control Trip connected to the microprocessor MCU, which in turn provides at least one output of the evaluation unit E2, i.e. is connected to at least the first or second connection V1, V2. In the example with the first connection V1.

The second output or connection of the evaluation unit E2 can be a common ground connection, as in 4 implied. Alternatively, it can also be connected directly to trip trigger control.

A monitoring unit Sense can be provided, which is connected directly to at least one connection V1, V2 and on the other hand via a common ground connection; alternatively directly connected to the first and second connection V1, V2. For example, parallel to the connections of the trip trigger control.

In the example according to 4 the monitoring unit Sense is part of the evaluation unit E2. However, it can also be configured as a separate unit. The power supply can be provided by an additional power pack or by an existing power pack of the residual current circuit breaker.

The monitoring unit Sense monitors the voltage, in particular the voltage over time, ie the signal curve, between the first and second connection V1, V2. For example, it can have an operational amplifier for impedance matching, for example for matching to an analog/digital converter or microprocessor input. Furthermore, it can have an analog/digital converter for digitizing the voltage. You can also have a transistor circuit point, with which the monitoring function is implemented. Furthermore, it can have its own microprocessor, particularly if it is designed as an independent unit.

5 shows a representation according to 3 , with the difference that an inventive switching contact SK is provided. This switching contact can be provided in the first and/or second connection V1, V2. If there is a storage circuit, it can be provided before or after the storage circuit, ie on the summation current transformer side or on the holding magnet release side.

The switching contact SK is advantageously switched by the evaluation unit E2. For example, it can be designed as a relay contact.

6 shows a representation according to 4 , with the difference that a switching contact SK according to 5 is provided, and the evaluation unit has a unit REL, for example with an output for controlling a relay contact as a switching contact SK for interrupting or activating the first detection circuit / mains voltage-independent tripping circuit.

The switching contact SK is designed, for example, as an opener, i.e. the switching contact SK is closed in the idle state or in the de-energized state.

The invention is explained in more detail below in other words.

A line voltage dependent RCD circuit as in 2 represented by the second summation current transformer W2 and evaluation unit E2, can offer advantages in connection with frequency converter systems as a result of a single electronic detection circuit with high measuring accuracy and good flexibility through digital signal processing using a microprocessor MCU. By using digital filters or applying methods to break down the signals into frequency components, a certain robustness of a residual current circuit breaker in relation to the false triggering resistance can be generated, so that tripping at the maximum permissible residual current according to the standard and/or the maximum permissible delay time according to the standard can be done.

The second, mains voltage-dependent detection circuit, with the evaluation unit E2, can switch off the first, mains voltage-independent detection circuit by means of a switching contact, e.g. a relay contact.

The second detection circuit is designed in such a way that it functionally has all the detection properties of the first detection circuit, formed by the first summation current transformer W1, possibly storage circuit E1, in conjunction with the holding magnet release A. For example, a type B residual current circuit breaker remains fully functional.

• ein Fehler im zweiten Detektionskreis auftritt. Beispielsweise falls das Netzteil ausfällt schließt der Schaltkontakt automatisch. Somit wird eine Grundfunktionalität durch den ersten Detektionskreis zur Verfügung gestellt.

Switching over/switching off can be carried out by the (microprocessor-controlled) evaluation unit 2, for example after its activation and a successfully completed self-test. The first detection circuit then remains switched off until, for example:

• an error occurs in the second detection circuit. For example, if the power supply fails, the switch contact closes automatically. A basic functionality is thus provided by the first detection circuit.

Likewise, an error in the cyclically recurring internal self-test from the second detection circuit can lead to the closing of the switching contact SK.

• Mikroprozessor MCU für z.B. die digitale Signalverarbeitung, beispielsweise mit digitalen Filtern und/oder Frequenzbetrachtung.

In 6 an example of the second detection circuit is shown in more detail:

• Microprocessor MCU for, for example, digital signal processing, for example with digital filters and/or frequency analysis.

Release control TRIP for separating the contacts via the holding magnet release A.

REL unit, e.g. as an output for controlling the switching contact SK / relay contact for interrupting or activating the first detection circuit / mains voltage-independent tripping circuit. The REL unit, for example, is designed to be protected against wire breakage, e.g. as an opener, i.e. in the event of an error, the first detection circuit becomes active and takes over the (co-)monitoring.

Signal processing SA for signal acquisition of converter signals on the secondary side with amplification and, if necessary, antialiasing filter.

Power pack PS as e.g. integrated power pack.

A special feature is the function when the residual current circuit breaker / device is switched on, since in this case both detection circuits work. This is particularly helpful as the second circuit, which is dependent on the mains voltage or is active, needs more time to be activated, i.e. until it is ready for use. In particular due to the start-up of the power pack PS or the microprocessor MCU.

With regard to the case of switching on and the simultaneous occurrence of a higher differential error In this way, a short tripping time (e.g. <= 40ms) can be ensured by the mains voltage-independent (first) detection circuit.

The advantage of the present invention lies in ensuring the full monitoring function of a residual current circuit breaker while at the same time improving the triggering behavior, particularly in connection with frequency converters. The solution requires two detection circuits and an additional switching contact / relay contact to interrupt a circuit. This can be controlled by the second circle. During the switch-on process, the first (mains voltage-independent) detection circuit helps with residual currents that suddenly occur, as long as the second (mains voltage-dependent) detection circuit is not yet ready for use (e.g. in the start-up phase).

The invention has the advantage that the functional safety is increased with at the same time little additional outlay in terms of production costs.

Claims (8)

Residual current circuit breaker (FI) for a low-voltage circuit, having: - several conductors (L1, L2, L3, N) of the low-voltage circuit to be protected, which can be opened or closed by contacts (K1, K2, K3, KN), - a mechanism (M ) for opening and closing the contacts (K1, K2, K3, KN), - a holding magnet release (A) connected to the mechanism (M), for opening the contacts (K1, K2, K3, KN), - a first Summation current transformer (W1), the primary side of which is formed by the conductors (L1, L2, L3, N) and which has a first secondary winding (SW1), - a first connection (V1) between a first connection of the first secondary winding (SWA1) and a first connection (AA1) of the holding magnet release (A), - a second connection (V2) between a second connection of the first secondary winding (SWA2) and a second connection (AA2) of the holding magnet release (A), - a second summation current transformer ( W2), the primary side of which is also formed by the conductors (L1, L2, L3, N) and which has a second secondary winding (SW2), - an evaluation unit (E2) connected to the second secondary winding (SW2), with at least two outputs, in which a first output is connected to the first connection (AA1) and a second output is connected to the second connection (AA2) of the holding magnet release (A), the first or second connection having a switching contact (SK), characterized in that the first and second connection (V1, V2) between the first secondary winding (SW1) and the holding magnet release (A) has a storage circuit (E1). Residual current circuit breaker (FI) after Claim 1 , characterized in that the evaluation unit (E2) receives an energy supply through at least part of the conductors (L1, L2, L3, N). Residual current circuit breaker (FI) according to one of the preceding patent claims, characterized in that the evaluation unit (E2) has a microprocessor (MCU). Residual current circuit breaker (FI) according to one of the preceding patent claims, characterized in that a power pack (PS) is provided for the energy supply, in particular for the evaluation unit (E2). Residual current circuit breaker (FI) according to one of the preceding patent claims, characterized in that a triggering control (Trip) is provided, which is in particular part of the evaluation unit (E2). Residual current circuit breaker (FI) according to one of the preceding patent claims, characterized in that the switching contact (SK) is an opener which can be actuated by the evaluation unit (E2). Method for a residual current circuit breaker (FI) for a low-voltage circuit with several conductors (L1, L2, L3, N), in which: - a first and a second detection circuit is provided, - each detection circuit determines a residual current in the conductors, - when a residual current threshold value is exceeded a triggering signal is sent to the terminals of a holding magnet trigger for interrupting the conductors of the low-voltage circuit, characterized in that when the functionality of the second detection circuit is present, the first detection circuit is switched to inactive. procedure after Claim 7 , characterized in that the first detection circuit is a mains voltage independent and the second detection circuit is a mains voltage dependent detection circuit.

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