DE102016116517A1 - Method and device for disconnecting an AC voltage circuit in case of undervoltage - Google Patents

Abstract

A method and an apparatus (A) for disconnecting a protected circuit (K) supplied with a polyphase alternating voltage (U1 ... U3) in case of undervoltage are disclosed. The device (A) comprises a microprocessor / microcontroller (μC) for carrying out the method. In this case, an actual voltage curve is determined for each phase (L1... L2), including a plurality of measuring points (MP) per period. In consequence, the actual voltage profile (U1... U3) is compared with a desired voltage profile and / or an actual parameter derived from the actual voltage profile with a desired parameter. If the deviation between the actual voltage curve (U1... U3) and the desired voltage curve or the deviation between the actual parameter and the desired parameter exceeds a threshold value in the direction of undervoltage, then the protected circuit (K) is replaced by the alternating voltage (U1). .U3) separately.

Description

TECHNICAL AREA

The invention relates to a method and a device for disconnecting an electrical, supplied with a polyphase AC voltage, protected circuit in case of undervoltage. Furthermore, the invention relates to a switching device with a device of the type mentioned and a controlled by this device and lying between the protected circuit and the AC power switch.

STATE OF THE ART

Said device is basically known from the prior art, in particular under the term "undervoltage release". For example, the DE 299 24 660 U1 An undervoltage release that monitors all three phases of an AC network. The phases are connected to a bridge rectifier, and the rectified voltage is fed to a special electromagnetic trip unit.

The CN 102013660 A also discloses an undervoltage release in which all three phases of an AC network are monitored. The disclosed circuit contains RC networks as well as an electronic evaluation.

The CN 203826924 U finally discloses another all-pole undervoltage release with an RC network.

A problem with the known arrangements or tripping methods is the fact that the conditions for tripping are difficult to parameterize and adapt. In addition, the known arrangements and tripping methods are relatively slow. That is, the time between the occurrence of undervoltage and the actual disconnection of the protected circuit is relatively long.

DISCLOSURE OF THE INVENTION

An object of the invention is therefore to provide an improved method and an improved device for disconnecting an electrical, supplied with a polyphase AC voltage protected circuit in case of undervoltage. In particular, the arrangement or the triggering method should be easy to parameterize and adapt, and the separation of the protected circuit should be able to be done quickly.

• – Messen eines Ist-Spannungsverlaufs für jede Phase, wobei jeweils mehrere Messpunkte pro Periode ermittelt werden,
• – Vergleichen des Ist-Spannungsverlaufs mit einem Soll-Spannungsverlauf und/oder zumindest eines vom Ist-Spannungsverlauf abgeleiteten Ist-Parameters mit zumindest einem Soll-Parameter und
• – Trennen des geschützten Schaltkreises von der Wechselspannung, wenn die Abweichung zwischen Ist-Spannungsverlauf und Soll-Spannungsverlauf einen ersten vorgebbaren Schwellwert und/oder die Abweichung zwischen dem zumindest einen Ist-Parameter und dem zumindest einen Soll-Parameter einen zweiten vorgebbaren Schwellwert in Richtung Unterspannung überschreitet.

The object of the invention is achieved by a method of the type mentioned above, comprising the steps:

• Measuring an actual voltage profile for each phase, wherein in each case a plurality of measuring points per period are determined,
• - Comparing the actual voltage curve with a desired voltage profile and / or at least one of the actual voltage profile derived actual parameter with at least one desired parameter and
• - Disconnect the protected circuit of the AC voltage when the deviation between the actual voltage waveform and target voltage waveform a first predetermined threshold and / or the deviation between the at least one actual parameter and the at least one desired parameter, a second predetermined threshold in the direction of undervoltage exceeds.

Furthermore, the object of the invention with a device of the type mentioned above, comprising a

• - Microprocessor or microcontroller, which is adapted to measure for each phase an actual voltage waveform, each containing a plurality of measurement points per period, or to capture the actual voltage waveform with a desired voltage waveform and / or at least one derived from the actual voltage waveform Actual parameter to compare with at least one desired parameter, and to trigger a separation of the protected circuit of the AC voltage when the deviation between the actual voltage waveform and target voltage waveform a first predetermined threshold and / or the deviation between the at least one actual parameter and the at least one desired parameter exceeds a second predefinable threshold in the direction of undervoltage.

Finally, the object of the invention is achieved with a switching device which has a device of the abovementioned type and a switch driven by this device and located between the protected circuit and the alternating voltage supply. In particular, said device can be housed in the housing of the switching device. That is, the device may be integrated in the switching device.

The proposed measures, the method and apparatus for separating an AC circuit can be easily parameterized and adapted to different conditions and specifications. In addition, the separation of the protected circuit can be done comparatively quickly. This is through digital processing Method also robust against temperature fluctuations and age-related degradation.

"Microprocessors" are semiconductor chips in which an algorithm is processed. "Microcontroller" semiconductor chips are referred to, which contain a processor and at the same time peripheral functions. In most cases, the work and program memory is partially or completely on the same chip. The demarcation between microprocessor and microcontroller is difficult or hardly possible. In the context of the invention, the two terms are therefore used synonymously and are therefore interchangeable.

A "switch lock" is a pawl-like mechanical device in electrical components, which allows the switching off of a circuit with a comparatively small force on a small path. A switch lock is usually used in switchgear, for example in residual current circuit breakers, circuit breakers, motor protection switches as well as in under-voltage releases. To turn off the force of a spring is released, which was tensioned when switching on a spring mechanism, after which the switch jumps back into its open position. Often, the triggering takes place via an electromagnetic coil, which releases the pawl either with appropriate energization or even in the absence of energization and thus triggers the separation of the protected circuit from a power supply.

Further advantageous embodiments and modifications of the invention will become apparent from the dependent claims and from the description in conjunction with the figures.

It is particularly advantageous if one or more members of the group: effective value of the voltage profile, mean value of the voltage profile, peak value of the voltage profile and / or voltage gradient of the voltage profile are used as parameters derived from the voltage profile. In particular, it can be provided that the parameter used is adjustable, that is, for example, it is possible to select whether the undervoltage release should be based on the rms value of the voltage profile or the voltage gradient of the voltage profile. As a result, the separation of the protected circuit can be made slower or less sluggish. For example, the evaluation of the voltage gradient of the voltage curve ensures a rapid evaluation result, whereas the evaluation based on the peak value of the voltage curve leads to a relatively slow triggering. The latter is due to the fact that such a peak value occurs only once per period, for example in the case of a sinusoidal course.

In a favorable variant of the presented method, the protected circuit is disconnected when the first and / or second threshold value is exceeded for at least one, in particular for exactly one phase voltage. This procedure is particularly suitable for consumers who are no longer operational in case of failure with only one phase voltage.

In a further favorable variant of the presented method, the protected circuit is disconnected when the first and / or second threshold value for all phase voltages is exceeded. This procedure is particularly suitable for consumers who are still operable or at least partially operable in case of failure of a phase voltage or even in the absence of two phase voltages.

In particular, it can be provided that it is adjustable whether the protected circuit is disconnected when the first and / or second threshold value for at least one (in particular a single) phase voltage is exceeded or if the first and / or second threshold value for all phase voltages is exceeded ,

It is furthermore advantageous if the protected circuit is disconnected after a specifiable, in particular adjustable, delay time after exceeding the first and / or second threshold value. For certain types of consumers, this may be cheaper than immediate disconnection.

Moreover, it is advantageous in the above context if the protected circuit is only disconnected if, after the delay time has elapsed, there is still an exceeding of said first and / or second threshold value in the direction of undervoltage. In this way it is avoided that the protected circuit is disconnected from the AC voltage after only one or short-term events. This variant of the presented method is therefore comparatively stable.

In particular, it can be provided that it is adjustable whether the protected circuit is disconnected after the delay time in each case from the AC voltage, or only if after expiry of the delay time still exceeded the said first and / or second threshold in Direction undervoltage is present.

It is also favorable if the measuring points are determined on the rectified actual voltage curve. Similarly, it is advantageous if the presented device has a rectifier which is connected between the input of the microprocessor / microcontroller and the AC input of the device. As a result, the measured value acquisition with a digital circuit, in particular with a microprocessor or microcontroller, is generally simpler. For rectification, a full bridge is advantageously used, since changes in the first and / or second threshold value can be detected rapidly in this way. Of course, it is also possible to use a half-bridge. The structure of the circuit is then easier.

It is also favorable if the measuring points are determined on the filtered actual voltage curve. Similarly, it is advantageous if the presented device has a filter which is connected between the input of the microprocessor / microcontroller and the AC input of the device. In this way it is avoided that interference and / or high-frequency voltage fluctuations have an (excessive) influence on the separation of the protected circuit. In particular, low-pass filters are used for this purpose. The filters can be designed as digital filters or as analog filters. A digital filtering can in particular also be realized by a software running in the microprocessor / microcontroller.

It is advantageous if the protected circuit is disconnected from all poles, in particular involving any existing neutral conductor. This avoids that the circuit powered by the AC voltage is still (partially) under voltage after a tripping.

It is also advantageous if data concerning a separation of the protected circuit is stored, in particular in a non-volatile memory and / or if the device for disconnecting the protected circuit comprises a wired and / or wireless interface. The proposed measures a separation of the protected circuit can be documented or logged, such as in a log file. For example, the date and time as well as the phase which led to the separation of the protected circuit can be stored. The data can be wired (for example, via a USB interface - "Universal Serial Bus"), optically via an infrared interface or wirelessly via a radio interface (for example, via a Bluetooth or Wi-Fi interface - "Wireless Fidelity") read become. Via this interface (s), the device can also be parameterized in an advantageous embodiment and adapted to different requirements. For example, an application can be started on a mobile phone or tablet computer, with the aid of which the device for disconnecting the protected circuit can be set as required.

It is advantageous if the current flow through a coil, which maintains a latch in a switch lock of a lying between the protected circuit and the AC power supply switching device when energized, for the separation of the protected circuit from the AC power supply under a holding current is reduced or prevented. As a result, no electrical energy is required after disconnecting the protected circuit from the AC voltage per se, whereby the switching state no longer changes even with total failure of the AC voltage.

Moreover, it is particularly advantageous if the coil is controlled to maintain the latching with a pulse width modulated signal. In this way, the holding current can be adjusted well, in particular to a value that is just needed to maintain the latch. As a result, the power consumption of the presented device can be kept low and electrical energy can be saved. For switching on, the pulse-pause ratio can be increased (in particular to 100%) whereby the coil generates a short-term stronger magnetic field to prevent inadvertent separation of the protected circuit from the AC voltage during transient processes.

It is also particularly advantageous if a temperature in a region thermally influenced by the coil is measured and a pulse-pause ratio of the pulse-width-modulated signal is increased with increasing temperature. In this way, the increase of the coil resistance can be compensated for heating.

In addition, it is advantageous if a temperature is measured inside a housing of a switching device in which the coil is arranged, and the protected circuit is disconnected from the AC voltage supply when the temperature exceeds a threshold value. As a result, the protected circuit can be disconnected from the AC voltage not only in the presence of an undervoltage but also under thermal overload.

It is also advantageous if the presented device has a power supply for powering the device that of the multi-phase AC power supply is supplied. This can be dispensed with a separate source of energy in the device. A failure of the AC voltage or a drop in voltage level is unproblematic in that the protected circuit is usually disconnected before the voltage (completely) collapses and the device for disconnecting the protected circuit has fulfilled its function before it fails.

However, it is also advantageous if the disclosed device has a capacitor, a battery and / or an accumulator for supplying energy to the device. In this way, the device for separating the protected circuit can be operated autonomously or at least in the short term autonomously. Particularly advantageous is the use of an autonomous energy source when the device separates the protected circuit only after a delay time after exceeding a first and / or second threshold value of the AC power supply.

Finally, it is advantageous if the device for separating the protected circuit has a temperature sensor for determining a temperature of a triggering mechanism for disconnecting the protected circuit. In this way, the influence of temperature on the tripping behavior can be determined, or subsequently compensated. The temperature sensor may for example be part of the microprocessor / microcontroller or be arranged as a discrete component on a circuit board of the device.

It should be noted at this point that the variants disclosed for the presented method and the resulting advantages relate equally to the presented method and vice versa.

BRIEF DESCRIPTION OF THE FIGURES

The present invention will be explained in more detail with reference to the exemplary embodiments indicated in the schematic figures of the drawing. It shows:

1 a schematic diagram of an exemplary device for disconnecting a protected circuit in case of undervoltage;

2 a schematic time course of the processes when an undervoltage occurs and the subsequent separation of the protected circuit;

3a . 3b a flowchart for a first example of the running in the course of the presented method operations and

4a . 4b a flowchart for a second example of the running in the course of the presented process operations.

DETAILED DESCRIPTION OF THE INVENTION

1 shows an exemplary device A for disconnecting a protected circuit K when an undervoltage occurs. The device A comprises an AC voltage input L1 ... L3, which is designed here three-phase and without neutral. Of course, the AC voltage input L1 ... L3 could also have a connection for a neutral, and it could also be provided a different number of phases.

The device A further comprises a rectifier G connected to the AC voltage input L1... L3, three filters F1... F3 connected on the output side to the rectifier G, three measuring circuits M1... M3 connected to the filters F1 On the output side connected to the measuring circuits M1 ... M3 microcontroller μC, one connected to the microcontroller μC (non-volatile) memory RAM, a man-machine interface HMI, a wireless interface WI with antenna, a connected to the microcontroller μC temperature sensor TS , a supply circuit PS, which is connected via diodes D2 ... D4 to the rectifier G and an energy storage C.

1 further shows a controlled by the microcontroller μC, first switch S1 and a lying in series with the first switch S1 coil L including freewheeling diode D1. This circuit part can basically be regarded as belonging to the device A or be formed as part of a switching device for disconnecting the protected circuit K.

The protected circuit K, which is disconnected from the AC voltage at low voltage, is in the right area of the 1 shown. The protected circuit K comprises in this example only a symbolically represented consumer R, and the leads to a second switch S2, which is controlled by the coil L. The combination of the coil L and the switch S2 may be part of a switching relay. But the coil L can also form those electromagnets which maintains a latch in a switching mechanism. The switching mechanism and the coil L are then part of a lying between the protected circuit K and the AC power supply L1 ... L3 switching device.

The in the left part of the 1 shown drive circuit for the coil L can be housed in the same housing as the switch lock and thus be integrated in the switching device. It is also conceivable that a separate housing is provided for the said drive circuit or for the device A.

The function of in the 1 The arrangement shown is as follows: The rectified AC voltage U1 ... U3 reaches the supply circuit PS via the rectifier G and the diodes D2... D4, which on the one hand ensures the electrical supply of the coil L as well as of the microcontroller .mu.C. If necessary, of course, the filters L1 ... L3, the measurement circuits M1 ... M3 and other modules can be electrically powered.

With the aid of the filters F1... F3, in particular high-frequency components of the alternating voltage U1... U3 can be filtered out. As a result, the filtered voltage is fed to the measuring circuits M1... M3 which perform the actual voltage measurement or process the filtered voltage at least for the measurement. The measuring circuits M1... M3 can, for example, have voltage dividers, amplifier circuits and analog-to-digital converters (ADCs) for this purpose. In the microcontroller μC the measured voltage is further processed.

• – Vergleichen des Ist-Spannungsverlaufs U1...U3 mit einem Soll-Spannungsverlauf und/oder zumindest eines vom Ist-Spannungsverlauf U1...U3 abgeleiteten Ist-Parameters mit zumindest einem Soll-Parameter und das
• – Trennen des geschützten Schaltkreises K vom Wechselspannungseingang L1...L3, wenn die Abweichung zwischen dem Ist-Spannungsverlauf U1...U3 und dem Soll-Spannungsverlauf einen ersten vorgebbaren Schwellwert und/oder die Abweichung zwischen dem zumindest einen Ist-Parameter und dem zumindest einen Soll-Parameter einen zweiten vorgebbaren Schwellwert in Richtung Unterspannung überschreitet.

Specifically, in the microcontroller μC the

• - Comparing the actual voltage waveform U1 ... U3 with a desired voltage waveform and / or at least one of the actual voltage waveform U1 ... U3 derived actual parameter with at least one desired parameter and the
• - Disconnecting the protected circuit K from the AC voltage input L1 ... L3, if the deviation between the actual voltage curve U1 ... U3 and the desired voltage waveform a first predetermined threshold and / or the deviation between the at least one actual parameter and the at least one desired parameter exceeds a second predefinable threshold in the direction of undervoltage.

In general, however, the measuring circuits M1... M3 and also the filters F1... F3 can be part of the microcontroller .mu.C, as a result of which

• - Measuring an actual voltage waveform U1 ... U3 for each phase L1 ... L3, including in each case a plurality of measuring points MP per period, in the microcontroller μC done.

The filters F1... F3 can in particular also be realized by a software running in the microcontroller .mu.C.

Accordingly, the microcontroller .mu.C is designed to measure or record an actual voltage profile U1... U3, containing in each case a plurality of measuring points MP per period, for each phase L1... L3, the actual voltage profile U1 a target voltage profile and / or at least one of the actual voltage curve U1 ... U3 derived actual parameter to compare with at least one desired parameter, and to trigger a separation of the protected circuit K from the AC voltage input L1 ... L3, if the deviation between the actual voltage curve U1... U3 and the desired voltage curve, a first predefinable threshold value and / or the deviation between the at least one actual parameter and the at least one desired parameter exceeds a second predefinable threshold value in the direction of undervoltage.

In general, the actual voltage curve U1... U3 can be directly compared with a desired voltage curve in order to determine whether the protected circuit K must be disconnected from the alternating voltage U1... U3 or not. A possible deviation of the actual voltage curve U1... U3 from the desired voltage curve can be detected quickly. For example, it can be determined that even the deviation of a measuring point MP from a setpoint point beyond a threshold value is sufficient enough for a separation of the protected circuit K from the alternating voltage network L1... L3. Of course, it is also conceivable that such a deviation must be present for a plurality of measuring points MP before the protected circuit K is disconnected from the alternating voltage network L1... L3.

Another possibility is to compare an actual parameter derived from the actual voltage profile U1... U3 with a desired parameter. For example, the rms value of the voltage profile U1... U3, the peak value of the voltage profile U1... U3, the voltage gradient of the voltage profile U1... U3 or any combination of the parameters mentioned can be used for this purpose become. In particular, it can be provided that the parameter used is adjustable, that is, for example, it is possible to select whether the undervoltage triggering should be based on the rms value of the voltage profile U1... U3 or the voltage gradient of the voltage profile U1. As a result, the separation of the protected circuit K carrier can be made less sluggish or less. For example, the evaluation of the voltage gradient of the voltage curve U1... U3 ensures a rapid evaluation result, whereas the evaluation based on the peak value of the voltage profile U1... U3 leads to a relatively slow triggering. The latter is due to the fact that such a peak value occurs only once per period, for example in the case of a sinusoidal course.

Furthermore, it is conceivable that the protected circuit K is disconnected from the AC voltage input L1 ... L3 when the first and / or second threshold value for at least one, in particular a single, phase voltage U1 ... U3 is exceeded, or if the first and / or or second threshold for all phase voltages U1 ... U3 is exceeded. The first case is particularly suitable for consumers R, which are no longer operable in case of failure with only one phase voltage U1 ... U3, the second for consumer R, in case of failure of a phase voltage U1 ... U3 or even in the absence of two phase voltages U1 ... U3 are still operational or are at least partially operational. In particular, an adjustment possibility can be provided for which of the two types of protected circuit K is disconnected from the AC voltage input L1... L3.

Another possibility is that the protected circuit K is separated after a predetermined, in particular adjustable, delay time after exceeding the first and / or second threshold. It is advantageous in this context, in particular, if the protected circuit K is only disconnected if, after the delay time has elapsed, the said first and / or second threshold value is still exceeded in the direction of undervoltage. In this way it is avoided that the protected circuit K is disconnected after only one or short-term events from the AC voltage input L1 ... L3. This variant of the presented method is therefore comparatively stable. Again, an adjustment can be provided for which of the two types of protected circuit K is disconnected from the AC voltage input L1 ... L3, or after which delay time the separation takes place.

With the aid of the capacitor C, the device A for the separation of the protected circuit K can be operated autonomously or at least in the short term independently, so that a long delay time can be bridged. Instead of a capacitor C, for example, a battery and / or an accumulator may be provided, with the help of which the device A shown can be operated practically independent of the AC voltage U1 ... U3. In principle, however, the use of an energy store C or an energy source is optional. The latter are only necessary if the device A does not have a power supply PS connected to the AC voltage U1... U3 (or else to another voltage network).

In the present example, the evaluation takes place at the rectified with the full-bridge rectifier G AC voltage U1 ... U3, whereby the evaluation in the microcontroller μC can be done in a relatively simple manner. Alternatively, the use of a half-bridge or the evaluation directly of the AC voltage U1 ... U3 is conceivable.

In the presented device A, the filters F1 ... F3 are connected between the input of the microcontroller μC and the output of the rectifier G, whereby the measuring points MP are determined at the filtered actual voltage curve U1 ... U3. This is advantageous, but not mandatory. Rather, it is also conceivable that the measuring points MP are determined at the unfiltered actual voltage curve U1... U3 and that the filters L1... L3 are therefore missing. The filters F1 ... F3 can of course also be arranged in front of the rectifier G.

In the optional memory RAM, data concerning a separation of the protected circuit K can be stored. For example, the date and time as well as the phase L1... L3, which led to the separation of the protected circuit K, can be stored.

This data can be read out via the optional wireless interface WI and / or via the (here wired) human-machine interface HMI. In addition, the device A can also be parameterized via this interface (s) in an advantageous embodiment and adapted to different requirements. For example, to an application can be started on a mobile phone or tablet computer, with the aid of which the operation of the device A for disconnecting the protected circuit K can be adjusted as needed. Specifically, it can be set whether the actual voltage profile U1... U3 is to be compared directly with a desired voltage profile, or whether the evaluation is based on the effective value of the voltage profile U1... U3, the mean value of the voltage profile U1 , the peak value of the voltage curve U1 ... U3 and / or the voltage gradient of the voltage curve U1 ... U3 should occur. In addition, a delay time can be set and also whether it is to be checked after expiry of the delay time whether there is still an exceeding of said first and / or second threshold value.

In the in 1 As shown, the current flow through the coil L, which maintains a latch in a switch lock of a lying between the protected circuit K and the AC power supply L1 ... L3 switching device when energized, for the separation of the protected circuit K from the AC voltage supply U1. .U3 reduced or prevented under a holding current. This is after the separation of the protected circuit K of the AC voltage U1 ... U3 in itself no electrical energy required, whereby the switching state no longer changes even with total failure of the AC voltage U1 ... U3. In principle, however, with the appropriate construction of the latch, it can also be provided that the protected circuit K is then disconnected from the AC voltage input L1... L3 when the coil L is sufficiently energized.

In the 1 is indicated that the microcontroller .mu.C can output a pulse width modulated signal to the first switch S1. In this optional embodiment, therefore, the coil L is driven to maintain the latching with a pulse width modulated signal, whereby the holding current is easily adjustable. In particular, a value can be set that is just needed to maintain the latch. As a result, the power consumption of the presented device A can be kept low and electrical energy can be saved. For switching on the pulse-pause ratio can be increased (especially to 100%) whereby the coil L short-term generates a stronger magnetic field to prevent inadvertent separation of the protected circuit K from the AC input L1 ... L3 in transient processes.

In a further optional embodiment, the temperature is measured with the aid of the temperature sensor TS in a region thermally influenced by the coil L. As a result, a pulse-pause ratio of the pulse width modulated signal can be increased with increasing temperature. In this way, the increase of the coil resistance can be compensated for heating.

It is also conceivable that with the aid of the temperature sensor TS, a temperature inside a housing of a switching device, in which the coil L is arranged, is measured and the protected circuit K is disconnected from the AC voltage input L1 ... L3 when the temperature is a threshold value exceeds. As a result, the protected circuit K can be disconnected not only in the presence of an undervoltage from the AC input L1 ... L3, but also in thermal overload.

The optional temperature sensor TS can be part of the microcontroller μC, for example, or can also be arranged as a discrete component on a printed circuit board of the device A.

2 now shows a schematic time course of the processes when an undervoltage occurs and the subsequent separation of the protected circuit K. Specifically, the voltage U is shown in the diagram as a function of time t. The diagram shows the three phase voltages U1... U3 in a time interval in which the second phase voltage U2 falls below a nominal value. Purely by way of example, the peak value of the nominal voltage is slightly above 600 V. Of course, however, what has been said also applies mutatis mutandis to any other nominal value.

At time t1, a drop of the second phase voltage U2 is detected. As a result, a trigger signal TS is generated, which on the one hand further evaluated internally in the device A and / or can also be forwarded via an interface or a switching output of the device A (not shown).

At a time t2, the switching signal SS has a negative edge. As a result, the energization of the coil L is set (or decreased), thereby disconnecting the protected circuit K from the AC input L1 ... L3. Between the first time t1 and the second time t2 is the (in particular adjustable) delay time.

It should be noted at this point that the voltage scale indicated on the vertical axis for the trigger signal TS and the switching signal SS does not apply, but the amplitude of the signals mentioned is significantly lower. Furthermore, it is noted that the switching signal SS is shown continuously, even if the first switch S1 is controlled pulse width modulated. The switching signal therefore indicates only the digital state of the protected circuit K "not disconnected" / "disconnected".

In the 2 In a period, some measuring points MP are also explicitly illustrated by way of example in order to indicate or visualize that the voltages U1... U3 are measured at discrete points in time. Of course, the measuring points MP are not only determined in the period shown, but continuously. In principle, it would be conceivable to monitor only one or more of the phase voltages U1... U3. As a rule, however, all phase voltages U1... U3 are monitored. That means that in the 2 Measuring points MP on all phase voltages U1 ... U3 and over the entire period shown mentally can be considered as existing.

It can also be seen from the arrangement of the measuring points MP that they do not necessarily have to be detected synchronized with the phase voltage U2, although this can, of course, be provided. In addition, it can also be seen that the peak value of the phase voltage U2 is not explicitly measured in this example. Nevertheless, this can be calculated from the other measuring points MP. It is conceivable but also that the peak value is measured explicitly.

It should also be noted that in the 2 not the rectified voltage is shown, but the voltage applied to the rectifier G AC voltage U1 ... U3. The lower half-waves are therefore mentally "fold up". It should also be noted that the method presented is, of course, applicable not only to sinusoidally running voltages U1... U3, but also to other voltage profiles, such as, for example, trapezoidal or triangular curves.

The 3a and 3b now show a flowchart for a first example of the running in the course of the presented process operations. Specifically, in a first step 301 turning it on and in a second step 302 the initialization of the presented device A. In one step 303 Information is read in via the human-machine interface HMI. In a further step 304 switch-on conditions are determined. In one step 305 a check is made as to whether the supply voltage is at a sufficient level. If so, the coil L becomes one step 306 switched on, that is energized. If this is not true, then it becomes a step 303 branched. After the step 306 gets in one step 307 queried the machine interface HMI, and in one step 308 the switch-off conditions are determined. If a phase voltage U1... U3 is below a threshold value, then in one step 310 the separation of the protected circuit K from the AC input L1 ... L3 triggered. On the other hand, if the phase voltage U1... U3 is not below the threshold value, then the step 307 branched. The separation of the protected circuit K becomes one step 311 additionally signaled. The next step is the step 302 and the process starts again.

The 4a and 4b show a flowchart for a second example of the running in the course of the presented process operations, the in the 3a and 3b presented procedure is very similar. The steps 401 ... 409 correspond to the steps 301 ... 309 and the steps 413 ... 414 correspond to the steps 310 ... 311 , Only the one between the step 409 and the step 413 inserted steps 410 ... 412 are different.

In step 410 a delay time is determined or awaited. In the following step 412 shutdown conditions are determined. If the phase voltage U1 ... U3 is still below the preset / set threshold value after expiry of the delay time, then in step 413 the separation of the protected circuit K from the AC input L1 ... L3 triggered. On the other hand, if the phase voltage U1... U3 is not below the threshold value, then the step 407 branched.

In general, the protected circuit K can be single-pole or - as in the 1 shown - are all poles separated from the AC voltage U1 ... U3, in particular involving any existing neutral conductor. The all-pole separation avoids, in particular, that the protected circuit K is still (partially) under voltage after a tripping.

Finally, it is further noted that the disclosed in the figures device A and their components are shown purely schematically. Furthermore, the device A may also comprise more or fewer components than shown. Location information (for example, "top", "bottom", "left", "right", etc.) are based on the respective figure described in each case and are adapted in a change in position of the device A mutatis mutandis to the new situation. Finally, it is noted that the above refinements and developments of the invention can be combined in any desired manner.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 29924660 U1 [0002]
• CN 102013660 A [0003]
• CN 203826924 U [0004]

Claims (22)

 Method for separating an electrical, protected with a polyphase AC voltage (U1 ... U3), protected circuit (K) in case of undervoltage, comprising the steps Measuring an actual voltage profile for each phase (L1... L2), wherein in each case a plurality of measuring points (MP) per period are determined, - Comparing the actual voltage waveform (U1 ... U3) with a desired voltage waveform and / or at least one of the actual voltage profile derived actual parameter with at least one desired parameter and - Disconnecting the protected circuit (K) of the AC voltage (U1 ... U3), when the deviation between the actual voltage waveform (U1 ... U3) and the desired voltage waveform a first predetermined threshold and / or the deviation between the at least one actual parameter and the at least one desired parameter exceeds a second predefinable threshold in the direction of undervoltage. Method according to Claim 1, characterized in that one or more members of the group: effective value of the voltage profile, mean value of the voltage profile, peak value of the voltage profile and / or voltage gradient of the voltage profile are used as parameters derived from the voltage profile. A method according to claim 1 or 2, characterized in that the protected circuit (K) is disconnected when the first and / or second threshold for at least one, in particular for exactly one phase voltage (U1 ... U3) is exceeded. A method according to claim 1 or 2, characterized in that the protected circuit (K) is disconnected when the first and / or second threshold for all phase voltages (U1 ... U3) is exceeded. Method according to one of claims 1 to 4, characterized in that the protected circuit (K) after a predeterminable, in particular adjustable, delay time after the exceeding of the first and / or second threshold value is disconnected. Method according to Claim 5, characterized in that the protected circuit (K) is only disconnected if, after the delay time has elapsed, the said first and / or second threshold value is still exceeded in the direction of undervoltage. Method according to one of claims 1 to 6, characterized in that the measuring points (MP) at the rectified actual voltage curve (U1 ... U3) are determined. Method according to one of claims 1 to 7, characterized in that the measuring points (MP) are determined on the filtered actual voltage curve (U1 ... U3). Method according to one of claims 1 to 8, characterized in that the protected circuit (K) is disconnected all poles, in particular involving any existing neutral conductor. Method according to one of claims 1 to 9, characterized in that data concerning a separation of the protected circuit (K) are stored, in particular in a non-volatile memory (RAM). Method according to one of claims 1 to 10, characterized in that the current flow through a coil (L), which is a latch in a switch lock of between the protected circuit (K) and the AC power supply (L1 ... L3) lying switching device (S2 ) is maintained under energization, for the separation of the protected circuit (K) from the AC power supply (L1 ... L3) is reduced or prevented under a holding current. A method according to claim 11, characterized in that the coil (L) is controlled to maintain the latching with a pulse width modulated signal. A method according to claim 12, characterized in that a temperature in one of the coil (T) thermally influenced area is measured and a pulse-pause ratio of the pulse width modulated signal is increased with increasing temperature. Method according to one of claims 1 to 13, characterized in that a temperature is measured inside a housing of a switching device in which the coil (L) is arranged, and the protected circuit (K) from the AC power supply (L1 ... L3 ) is disconnected when the temperature exceeds a threshold. Device (A) for disconnecting an electrical, supplied with a polyphase AC voltage (U1 ... U3), protected circuit (K) at low voltage, comprising a - microprocessor or microcontroller (μC), which is adapted for each phase (L1 ... L3) an actual voltage curve (U1 ... U3), containing in each case a plurality of measuring points (MP) per period, to measure or to detect the actual voltage curve (U1... U3) with a desired voltage curve and / or at least one actual curve derived from the actual voltage curve (U1... U3). Compare parameters with at least one desired parameter, and to trigger a separation of the protected circuit (K) of the AC voltage (U1 ... U3), if the deviation between the actual voltage waveform (U1 ... U3) and the setpoint Voltage curve exceeds a first predetermined threshold and / or the deviation between the at least one actual parameter and the at least one desired parameter exceeds a second predetermined threshold in the direction of undervoltage.  Device (A) according to claim 15, characterized by a rectifier (G) which is connected between the input of the microprocessor / microcontroller (μC) and the AC voltage input (L1 ... L3) of the device (A).  Device (A) according to claim 15 or 16, characterized by a filter (F1 ... F3) connected between the input of the microprocessor / microcontroller (μC) and the AC input (L1 ... L3) of the device (A) ,  Device (A) according to one of Claims 15 to 17, characterized by a power supply unit (PS) for supplying power to the device (A) which is supplied by the multiphase AC voltage network (L1 ... L3).  Device (A) according to one of claims 15 to 18, characterized by a capacitor (C), a battery and / or a battery for supplying power to the device (A).  Device (A) according to one of claims 15 to 19, characterized by a wired interface (HMI) and / or wireless interface (WI).  Device (A) according to one of Claims 15 to 20, characterized by a temperature sensor (TS) for determining a temperature of a triggering mechanism for disconnecting the protected circuit (K).  Switching device, characterized by a device (A) according to one of Claims 15 to 21 and a switch (S2) controlled by said device (A) and located between the protected circuit (K) and the AC voltage supply (L1 ... L3).

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