EP2208215B1 - Switching arrangement and method for controlling an electromagnetic relay - Google Patents

Description

The invention relates to a switching arrangement for driving a relay coil having a relay relay and having electromagnetic relay, wherein in a current path with the relay coil two switching devices are arranged such that a first switching device with a first terminal of the relay coil and a second switching device with a second terminal of the relay coil communicates; a drive device is provided which is set up to close both switching devices in order to establish a current flow through the relay coil and to open both switching devices in order to interrupt a current flow through the relay coil. The invention also relates to a corresponding method for driving an electromagnetic relay.

In electrical devices, electromagnetic relays are often used to perform controlled switching operations. Electromagnetic relays usually consist of a relay coil and at least one pair of electrical relay contacts. If an electric current is applied to the relay coil, a magnetic field is generated around the relay coil, whereby - in the case of self-opening relays - a closure of the relay contacts is effected so that a current flow through the relay contacts is possible. If the current flowing through the relay coil interrupted again, the movable part of the relay contacts is moved back, for example by means of a spring means in its initial position, causing an opening of the relay contacts and interrupts the flow of current through them. For self-closing relays are the contacts closed in the de-energized state of the relay coil and open in the current-carrying state.

Electromagnetic relays are usually used where, by means of a comparatively low current from a drive circuit, a comparatively larger current in a switching circuit to be switched on or off. The electromagnetic relay forms in this case a galvanic decoupling of the drive circuit and the switching circuit.

Electromagnetic relays are used, for example, in electrical protective devices for monitoring electrical energy supply networks in order to trigger a tripping of an electrical circuit breaker in the event of a fault in the electrical energy supply network by closing the relay contacts of a so-called "command relay", thus interrupting the fault current. When using electromagnetic relays in such safety-related areas, it is of utmost importance to reliably prevent unintentional switching on or off in order to ensure a high degree of safety in the event of a fault on the one hand, and to avoid costly false triggering on the other hand.

In order to carry out a monitoring of the state of the relay contacts, it makes sense initially to return their actual state, ie open or closed, to the control device of the relay coil. In case of a deviation between the setpoint and the actual state of the relay contacts, an error in the relay control is concluded.

However, such monitoring is relatively complex, because in this case the achieved by the relay galvanic decoupling between control circuit and switching circuit for feedback of information about the state of the relay contacts must be exceeded. In addition, an error can be detected only if it has already occurred, so the relay contacts have already taken an undesirable state. A predictive monitoring is not possible.

Therefore, efforts have been made to design the drive circuit of the relay coil as fail-safe as possible. Errors can arise in switching devices, for example, by a fusion of the switching contacts by a high switching power or too high temperature, so that the corresponding switching device is permanently short-circuited. In semiconductor switches, such as Transistors, a similar effect is known as a so-called "alloying" of the terminals of the semiconductor switch. Likewise, both mechanical switching devices and semiconductor switches can permanently block the current flow due to an internal fault. Furthermore, an error may also occur in the relay coil itself, e.g. Due to line break, no current flow through the relay coil is possible.

For the most fail-safe configuration of the drive circuit, the relay coil is not only controlled by a possibly error-prone single switching device, but instead via two switching devices located in the current path of the relay coil. The relay coil is only activated when both switching devices are closed at the same time. As soon as a switching device is opened, the current flow through the relay coil is interrupted. This will achieved a relatively high reliability of the control against unintentional activation of the relay coil, as a defective, permanently short-circuited switching device alone can not cause unwanted activation of the relay coil. Such a switching arrangement is for example from the German patent DE 44 09 287 C1 known from which a relay coil emerges, which is located with two switching devices in the form of transistors in a current path.

Another such switching arrangement is from the document EP 0 673 050 A known.

The invention has for its object to provide a circuit arrangement and a method of the type mentioned above, which allow a predictive review of the relay coil and the two switching devices to possibly occurred errors.

This object is achieved with respect to the switching arrangement by a switching arrangement of the type mentioned, in which the drive means for emitting test signals to the first and the second switching means is arranged, wherein the test signals are such that they do not affect the current state of the relay contacts; an input of a conversion device is acted upon by a measurement voltage which is tapped between a connection of the relay coil and one of the switching devices, wherein the conversion device is set up to convert the measurement voltage into a binary response signal; and connected to an output of the conversion device is a monitoring device which evaluates the course of the binary response signal during the transmission of the test signals by the control device and indicates an error in the relay coil or one of the switching devices if the course of the binary response signal deviates from an expected curve.

The particular advantage of the switching arrangement according to the invention is that a comparatively inexpensive examination of the correct function of the relay coil and the two switching devices is already possible if no faulty switching operation of the relay has yet been carried out. In this way, as it were, a forward check of the relay coil and the two switching devices can be performed for possible errors. In this context, "anticipatory" means that a check of the functionality can take place without bringing about a switching action of the relay contacts. For this purpose, only a single measuring signal in the form of the measuring voltage is tapped and monitored in comparatively inexpensive manner. A malfunction of the two switching devices or the relay coil can be advantageously achieved both when switched on and when the relay coil is switched off by the two switching devices are acted upon with test signals that do not affect the current state of the relay contacts.

If an error is detected during monitoring in one of the switching devices or in the relay coil, then an operator of a device in which the electromagnetic relay is installed - for example the operator of a corresponding electrical protection device - can be informed about a corresponding error message, so that he Replacement of the relay and its drive circuit bearing assembly can cause.

According to an advantageous embodiment, it is provided that the two switching devices are semiconductor switches, in particular transistors. Such semiconductor switches can be switched on and off particularly quickly and with low switching power.

A further advantageous embodiment of the switching arrangement according to the invention further provides that in the current path of the relay coil between each terminal of the relay coil and a switching device, a terminal of a respective damping capacitor is arranged. Due to the damping effect of the capacitors, the course of the measuring voltage and thus the course of the binary response signal can be extended in time so that a particularly simple evaluation is possible.

A further advantageous embodiment of the switch arrangement according to the invention further provides that the conversion device has a parallel to the current path of the relay coil arranged voltage divider, the Spannungssteilerabgriff is acted upon on the one hand with the measuring voltage and on the other hand supplied to obtain a binary response signal to a control input of another switching device. In this way, a binary response signal from the measurement voltage can be generated without much circuit complexity.

The further switching device may be, for example, a semiconductor switch, in particular a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). Field-effect transistors are driven by voltages and are therefore particularly well suited in the present case for the conversion of the measurement voltage into a binary response signal.

With regard to the method, the above-mentioned object is achieved by a method for driving an electromagnetic relay having a relay coil and relay contacts, in which both switching devices are closed to establish a current flow through the relay coil and to interrupt a current flow through the relay coil both switching devices are opened, wherein the switching devices are arranged in a current path with the relay coil such that the first switching device is connected to a first terminal of the relay coil and the second switching device to a second terminal of the relay coil, wherein in the inventive method, the drive means test signals delivers to the two switching devices that do not affect the current state of the relay contacts; between a terminal of the relay coil and one of the switching devices, a measuring voltage is tapped; the measuring voltage is converted into a binary response signal; and an error in the relay coil or one of the two switching devices is indicated if the course of the binary response signal deviates from an expected course. With the method described, a check of the drive circuit of the electromagnetic relay can advantageously take place in a forward-looking manner.

As an advantageous development, it is also considered if in the opened state of the relay contacts time-delayed test signals are delivered to the two switching devices, which are shorter than a response time of the relay.

Here, the time is regarded as the response time of the relay, which requires a magnetic field generated by the relay coil to respond to sudden change in a voltage applied to the relay coil voltage with a change in the switching state of the relay contacts.

If, for example, the relay coil is switched off in the case of a completely established magnetic field, the magnetic field only builds up with a certain time delay. Only when the magnetic field strength is no longer sufficient to hold the relay contacts in their previous position, the state of the relay contacts changes. If you switch back on the timely Relay coil, so the magnetic field builds up again and the relay contacts remain in their state without change.

In the opposite case, a magnetic field of the relay coil in a sudden application of a voltage to the - previously de-energized - relay coil requires a certain period of time until its magnetic field strength sufficient to control the relay contacts. If the current flow is interrupted in good time, the state of the relay contacts does not change.

The test signals must therefore be so short in terms of their duration that no change in the state of the relay contacts occurs due to the inertia of the magnetic field of the relay coil which builds up or degrades.

A check of the two switching devices and the relay coil for possible errors can be carried out with the inventive method, both in the currentless as well as in the current-carrying state of the relay coil.

1. a) ein Prüfsignal wird an die zweite Schalteinrichtung abgegeben;
2. b) während einer Signalpause wird kein Prüfsignal abgegeben;
3. c) ein Prüfsignal wird an die erste Schalteinrichtung abgegeben.

Specifically, a check in the de-energized state of the relay coil and the tap of the measuring voltage between the second terminal of the relay coil and the second switching device can be performed, for example, by the test signals are issued in the following sequence:

1. a) a test signal is delivered to the second switching device;
2. b) during a signal pause no test signal is emitted;
3. c) a test signal is delivered to the first switching device.

When tapping the measuring voltage between the first terminal of the relay coil and the first switching device, the distribution of the test signals to the switching devices is to be reversed accordingly.

In the current-carrying state of the relay coil, a check can be carried out according to an advantageous development by the first switching device is permanently driven, while the second switching device is controlled by a pulsed test signal.

The timing of the binary response signal, for example, can be compared continuously with the expected course. A particularly advantageous embodiment of the method according to the invention provides, however, that to determine whether an error is present in the relay coil or one of the switching devices, the binary response signal is compared to the expected course at least two characteristic times, wherein between the characteristic times at least one change with respect to the condition of at least one test signal. In this embodiment, the computing power required for the comparison of the monitoring device is kept relatively low, since the course of the binary response signal and the expected course in the simplest case only have to be compared with each other at two particularly characteristic times and therefore a continuous comparison is not necessary. Since a 100% coincidence of the binary response signal and the expected course will usually be difficult to achieve anyway, there is a further advantage of this embodiment is that with a sensible choice of the time points considered - namely in sufficient order at those times to which a change the test signals takes place - insignificant deviations between the course of the binary response signal and the expected course do not lead to an error message.

In order to be able to continuously monitor the two switching devices and the relay coil for possible errors, the method according to the invention should be repeated at regular time intervals.

Advantageously, different test signals are emitted by the control device depending on the state of the relay contacts.

Figur 1

ein schematisches Blockschaltbild einer allgemeinen Ausführungsform einer Schaltanordnung zum Ansteuern eines elektromagnetischen Relais,

Figur 2

ein Schaltbild einer möglichen Ausführungsform einer Schaltanordnung zum Ansteuern eines elektromagnetischen Relais,

Figur 3

mehrere Diagramme zur Erläuterung von beispielhaften Prüfsignalen und die hierdurch hervorgerufenen Messspannungen und binären Antwortsignale bei einer Überprüfung im stromlosen Zustand der Relaisspule,

Figur 4

ein Verfahrensablaufschema zur Erläuterung eines Ausführungsbeispiels einer Überprüfung im stromlosen Zustand der Relaisspule,

Figur 5

eine Prüfsignalfolge für eine Überwachung im stromdurchflossenen Zustand der Relaisspule,

Figur 6

mehrere Diagramme zur Erläuterung von beispielhaften Prüfsignalen und die hierdurch hervorgerufenen Messspannungen und binären Antwortsignale bei einer Überprüfung im stromdurchflossenen Zustand der Relaisspule und

Figur 7

ein Verfahrensablaufschema zur Erläuterung eines Ausführungsbeispiels einer Überprüfung im stromdurchflossenen Zustand der Relaisspule.

The invention will be explained in more detail below with reference to exemplary embodiments. Show this

FIG. 1

3 is a schematic block diagram of a general embodiment of a switching arrangement for actuating an electromagnetic relay.

FIG. 2

a circuit diagram of a possible embodiment of a switching arrangement for driving an electromagnetic relay,

FIG. 3

several diagrams for explaining exemplary test signals and the resulting measurement voltages and binary response signals during a check in the de-energized state of the relay coil,

FIG. 4

a process flow diagram for explaining an embodiment of a review in the de-energized state of the relay coil,

FIG. 5

a test signal sequence for monitoring in the current-carrying state of the relay coil,

FIG. 6

several diagrams for explaining exemplary test signals and the resulting measurement voltages and binary response signals in a review in the current-carrying state of the relay coil and

FIG. 7

a process flow diagram for explaining an embodiment of a review in the current-carrying state of the relay coil.

FIG. 1 shows a schematic block diagram of an embodiment of a switching arrangement for driving an electromagnetic relay. A drive circuit of the electromagnetic relay comprises in a current path 10 a series connection of a relay coil 11 with a first switching device 12a and a second switching device 12b, the switching devices 12a and 12b in FIG FIG. 1 merely exemplified by mechanical switching devices. The switching devices 12a and 12b may be formed by mechanical switches or semiconductor switches, such as transistors.

With "V +" and "V-" a high or low voltage level is indicated. For example, the high voltage level V + may be at 10V while the low voltage level is V-0V. The first switching device 12a communicates with a first terminal 11a of the relay coil 11 on the high voltage level V + side, while the second low-voltage side switching device 12b connects with a second terminal 11b of the relay coil 11.

The first and second switching devices 12a and 12b are connected to their drive inputs with a drive device 13 in connection. Via the drive device 13, the switching devices 12a and 12b can be switched on or off. The control device 13 is set up for the delivery of test signals to the control inputs of the first and second switching devices 12a and 12b, as will be explained in more detail later.

At the connection of the second terminal 11b of the relay coil 11 with the second switching device 12b, a measuring voltage U _{mess is} tapped off via a branch 14 and fed to a converting device 15. The conversion device 15 is configured to convert the measurement voltage U _mess into a binary response signal BS and to deliver this at its output. The binary response signal BS is supplied to a monitoring device 16, which can exchange information with the drive device 13. The monitoring device 16 can either - as in FIG. 1 represented - form an independent unit or - deviating from the representation in FIG. 1 - Be integrated in the drive device 13. Both the drive device 13 and the monitoring device 16 may include a microprocessor or other logic device (eg, an ASIC) that controls their operation.

Deviating from the illustration in FIG. 1 the measuring voltage U _{mess can} also be arranged at the connection between the first switching device 12a and the first terminal of the relay coil 11. The sequence of the test signals for monitoring the current path 10 described below is correspondingly reversed to the two in such a case Distribute switching devices 12a and 12b, the error cases described below are also adapted accordingly. In the following examples, however, is intended by a tap of the measuring voltage U _mess according to FIG. 1 , So be assumed that between the second switching device 12b and the second terminal of the relay coil 11.

In a possible more concrete embodiment, a switching arrangement for driving an electromagnetic relay, for example, as in FIG. 2 be shown constructed. For the FIG. 1 appropriate components are in FIG. 2 the same reference numerals used.

In FIG. 2 That is, a relay coil 11 connected to a first switching device 12a on the high voltage level V + side with its first terminal 11a, and the second terminal 11b on the low voltage V- side relay coil 11 are connected to a second switching device 12b stands.

By way of example, the switching devices 12a and 12b are shown in FIG. 2 as semiconductor switches in the form of transistors.

By means of a border shown in dashed lines, a group of switching elements is indicated, which correspond to the conversion device 15 FIG. 1 equivalent. The core of the conversion device 15 forms in accordance with the embodiment FIG. 2 a voltage divider 22, which consists of two ohmic resistors 22a and 22b by way of example. Between the two ohmic resistors 22a and 22b is a Spannungssteilerabgriff 23, on the one hand with the branch 14 for the measuring voltage and on the other hand is in communication with a control input of a further switching device 24.

A series circuit 25, which is arranged parallel to the relay coil 11 and the switching device 12a and consists of an ohmic resistor 25a and a diode 25b, serves to intercept overvoltages that may arise when the current flow through the relay coil 11 is interrupted. Another ohmic resistor 26 is used to adjust the voltage level of the binary response signal BS.

At the connection of the first switching device 12a with the first terminal 11a of the relay coil 11, a terminal of a first damping capacitor 27a is connected, which lies with its other terminal at the low voltage level V-. Accordingly, at the connection between the second switching device 12b and the second terminal 11b of the relay coil 11 with its one terminal, a second damping capacitor 27b is connected, whose second terminal is also at the low voltage level V-.

The following is the functioning of the in FIG. 2 illustrated switching arrangement, in particular with regard to the review of the two switching devices 12a and 12b and the relay coil 11 for possible errors, will be explained in more detail. This is except on FIG. 2 also on the FIGS. 3 to 7 Referenced.

The control device 13 initially serves to establish a current flow through the relay coil 1 or to interrupt it by simultaneously opening or closing the switching devices 12a and 12b. By simultaneous closing of the two switching devices 12a and 12b, a current flow through the relay coil 11 is produced, whereby a developed corresponding magnetic field in the relay coil 11 and from a certain magnetic field strength, causing a change in the state of the (not shown) relay contacts of the electromagnetic relay. In order to interrupt the flow of current in the relay coil, the control device 13 opens the two switching devices 12a and 12b, so that the magnetic field generated by the relay coil 11 degrades again. If the field strength generated by the magnetic field is no longer sufficient to hold the relay contacts in their position, they will change to their normal position, for example due to the action of a spring force.

In the event that there is a fault in one of the two switching devices 12a and 12b or the relay coil 11, the proper control of the relay coil 11 and thus of the arranged on the relay contacts switching circuit can no longer be guaranteed. For the exemplary case that it is the electromagnetic relay to a command relay for driving an electric circuit breaker, such a malfunction, for example, an unwanted false tripping of the circuit breaker caused or a deliberate tripping of the circuit breaker can be prevented. Therefore, a check of the existing of the two switching devices 12a and 12b and the relay coil current path 10 takes place. Depending on whether the relay coil 11 in the currentless or current-carrying state, the control devices 13 to the switching devices 12a and 12b different test signals P_A, P_B delivered that have a change in the voltage level at the branch 14 result.

The voltage applied to this branch 14 measuring voltage U _mess is fed to the converting device 15, where they are in a binary Response signal BS is implemented. The course of the binary response signal BS is compared by the monitoring device 16 with an expected course, and an error in the current path 10 is detected if the expected course and the actual course of the binary response signal BS differ from each other. In order to be able to compare the expected course and the actual course of the binary response signal BS, the monitoring device 16 is able to exchange information with the control device 13, for example via the beginning of sending the test signals P_A, P_B to the two switching devices 12a and 12b to be informed.

If the monitoring device 16 detects an error in the current path 10, a corresponding error message can be issued, which informs an operator of a device in which the electromagnetic relay is installed, about the error. The operator of the corresponding device can then replace the corresponding faulty module, even before it can lead to an actual malfunction of the electromagnetic relay.

A check of the current path 10 for possible errors can be carried out both in the currentless and in the current-carrying state of the relay coil and correspondingly switched off or switched relay contacts, without affecting the state of the relay contacts thereby.

The following is supposed to be based on the Figures 2 . 3 and 4 It will be explained how a check of the current path 10 can be carried out with (intentional) currentless relay coil.

In FIG. 3 For this purpose, the curves of the test signals P_A and P_B are shown in the two upper diagrams, while in the The following ten diagrams each on the left side of the measuring voltages applied to the branch 14, shown for the error-free case and for various error cases, while shown on the right side respectively resulting from the respective measurement voltages binary response signals for the error-free case and for various error cases are.

As FIG. 3 is removed, a second test signal P_B is initially supplied to the second switching device 12b to start a test run. This test signal P_B brings the second switching device 12b in its closed state.

The duration of the test signal P_B is in this case such that even in the event that the first switching device 12a should be permanently short-circuited due to an error, the duration of a resulting then by the relay coil 11 current flow has no effect on the state of the relay contacts. The duration of the test signal P_B must therefore be less than the response time of the relay already explained earlier. Usually, the duration of a test signal for this purpose can be selected between a lower and an upper limit, the lower limit indicating the time required to generate a correct binary response signal in the converter 15 and the upper limit at a sufficiently safe distance from the Response time of the relay should be. For example, the possible range for the duration of the test signals may be between about 40 and about 200 μs.

As FIG. 3 can be removed, the delivery of the test signal P_B to the second switching device 12b is terminated after such a short period of time chosen again and there is a signal pause, while no test signal to the switching devices 12a or 12b is delivered. Following the switching pause another test signal P_A is delivered to the first switching device 12a, which causes the switching device 12a to close. Also, the test signal P_A must be so short in terms of its duration that even if the second switching device 12b erroneously should be in a permanently short-circuited state, the state of the relay contacts is not affected. The duration of the test signal P_A must therefore also be below the response time of the relay.

After completion of this test signal sequence of the test run is completed; After any break, another test run can be started. For example, it can be provided that a renewed test run is initiated every 250 μs.

für den Fall, dass sich sowohl die Schalteinrichtungen 12a und 12b als auch die Relaisspule 11 in einem korrekten, also fehlerfreien, Zustand befinden (korr = korrekt). Der Verlauf der Messspannung ${\mathit{U}}_{\mathit{mess}}^{\mathit{korr}}$

soll nun unter Hinzunahme der Figur 2 erläutert werden. Hierzu wird davon ausgegangen, dass die beiden Schalteinrichtungen 12a und 12b einwandfrei funktionieren und sich zunächst beide im gesperrten Zustand befinden.The second line of the FIG. 3 arranged diagrams show the course of the measuring voltage ${\mathit{U}}_{\mathit{mess}}^{\mathit{corr}}$

in the event that both the switching devices 12a and 12b and the relay coil 11 are in a correct, ie error-free, state (corr = correct). The course of the measuring voltage ${\mathit{U}}_{\mathit{mess}}^{\mathit{corr}}$

should now with the addition of FIG. 2 be explained. For this purpose, it is assumed that the two switching devices 12a and 12b work properly and initially both are in the locked state.

auf einem mittleren, durch den Spannungsteiler 22 vorgegebenen Spannungsniveau. Das binäre Antwortsignal BS^korr befindet sich auf einem hohen Pegel, da die Messspannung ${\mathit{U}}_{\mathit{mess}}^{\mathit{korr}}$

ausreicht, um die weitere Schalteinrichtung 24 durchzusteuern. Durch die Abgabe des Prüfsignals P_B an die zweite Schalteinrichtung 12b wird die Schalteinrichtung 12b geschlossen und die Messspannung ${\mathit{U}}_{\mathit{mess}}^{\mathit{korr}}$

am Abzweig 14 wird auf das niedrige Spannungsniveau V-gezogen, da die zweite Schalteinrichtung 12b den unteren Widerstand 22b des Spannungsteilers 22 überbrückt. Dem Verlauf der Messspannung ${\mathit{U}}_{\mathit{mess}}^{\mathit{korr}}$

in Figur 3 kann somit ein sprunghaftes Absinken entnommen werden, sobald das Prüfsignal P_B die Schalteinrichtung 12b schließt. Entsprechend sinkt das binäre Antwortsignal BS^korr auf einen niedrigen Pegel ab, da die weitere Schalteinrichtung aufgrund der niedrigen anliegenden Messspannung ${\mathit{U}}_{\mathit{mess}}^{\mathit{korr}}$

sperrt. Nach Beendigung des Prüfsignals P_B geht die zweite Schalteinrichtung 12b wieder in den gesperrten Zustand über und die zuvor entladenen Dämpfungskondensatoren 27a und 27b werden über den oberen Widerstand 22a des Spannungsteilers 22 aufgeladen. Bei ausreichender Dimensionierung der Dämpfungskondensatoren 27a und 27b und des ohmschen Widerstandes 22a des Spannungsteilers, geschieht dieser Ladungsvorgang jedoch derart langsam, dass ein Anstieg der Messspannung ${\mathit{U}}_{\mathit{mess}}^{\mathit{korr}}$

während der Signalpause kaum bemerkbar ist.First, the measuring voltage is ${\mathit{U}}_{\mathit{mess}}^{\mathit{corr}}$

on a middle, predetermined by the voltage divider 22 voltage level. The binary response signal BS ^korr is at a high level since the measurement voltage ${\mathit{U}}_{\mathit{mess}}^{\mathit{corr}}$

sufficient to durchzusteuern the further switching device 24. By the levy of the test signal P_B to the second switching device 12b, the switching device 12b is closed and the measurement voltage ${\mathit{U}}_{\mathit{mess}}^{\mathit{corr}}$

at the branch 14 is pulled to the low voltage level V-pull, since the second switching device 12b, the lower resistor 22b of the voltage divider 22 bridges. The course of the measuring voltage ${\mathit{U}}_{\mathit{mess}}^{\mathit{corr}}$

in FIG. 3 Thus, a sudden drop can be taken as soon as the test signal P_B closes the switching device 12b. Accordingly, the binary response signal BS ^corr decreases to a low level, since the further switching device due to the low applied measurement voltage ${\mathit{U}}_{\mathit{mess}}^{\mathit{corr}}$

locks. After completion of the test signal P_B, the second switching device 12b again switches to the blocked state and the previously discharged damping capacitors 27a and 27b are charged via the upper resistor 22a of the voltage divider 22. With sufficient dimensioning of the damping capacitors 27a and 27b and the ohmic resistor 22a of the voltage divider, however, this charging process takes place so slowly that an increase in the measuring voltage ${\mathit{U}}_{\mathit{mess}}^{\mathit{corr}}$

during the signal break barely noticeable.

ist zumindest nicht ausreichend, um die weitere Schalteinrichtung 24 der Umsetzeinrichtung 15 in ihren stromdurchlässigen Zustand zu überführen, so dass das binäre Antwortsignal BS^korr während der Signalpause weiter auf dem niedrigen Pegel verharrt. Wenn nach der Signalpause das Prüfsignal P_A auf die erste Schalteinrichtung 12a einwirkt und diese in ihren stromdurchlässigen Zustand bringt, werden die Dämpfungskondensatoren 27a und 27b vergleichsweise schnell aufgeladen, da der obere Widerstand 22a des Spannungsteilers 22 überbrückt ist und das hohe Spannungsniveau V+ direkt an den Dämpfungskondensatoren 27a und 27b anliegt. Diesen schnellen Ladevorgang erkennt man auch am Verlauf der Messspannung ${\mathit{U}}_{\mathit{mess}}^{\mathit{korr}},$

der während der Abgabe des zweiten Messsignals P_A steil ansteigt. Schließlich liegt die Messspannung ${\mathit{U}}_{\mathit{mess}}^{\mathit{korr}}$

auf dem hohen Spannungsniveau V+. Sobald die Messspannung ${\mathit{U}}_{\mathit{mess}}^{\mathit{korr}}$

einen Pegel erreicht hat, der die weitere Schalteinrichtung 24 zum Durchschalten veranlasst, steigt dass binäre Antwortsignal BS^korr sprunghaft auf seinen hohen Pegel an. Wird die Abgabe des ersten Prüfsignals P_A nach Ablauf der entsprechenden Zeitdauer beendet, stellt sich nach Entladung der Dämpfungskondensatoren 27a und 27b über den unteren Widerstand 22b des Spannungsteilers 22 am Abzweig 14 wieder auf das entsprechend des Spannungsteilers 22 vorbestimmte mittlere Spannungsniveau ein.The increase of the measuring voltage ${\mathit{U}}_{\mathit{mess}}^{\mathit{corr}}$

is at least not sufficient to convert the further switching device 24 of the conversion device 15 in its current-permeable state, so that the binary response signal BS ^corr remains during the signal pause remains at the low level. If after the signal pause the test signal P_A acts on the first switching device 12a and brings them into their current-permeable state, the snubber capacitors 27a and 27b are charged comparatively fast, since the upper resistor 22a of the voltage divider 22 is bridged and the high voltage level V + directly across the snubber capacitors 27a and 27b is applied. This fast charging process can also be recognized on the Course of the measuring voltage ${\mathit{U}}_{\mathit{mess}}^{\mathit{corr}}.$

which increases steeply during the delivery of the second measurement signal P_A. Finally, the measurement voltage is ${\mathit{U}}_{\mathit{mess}}^{\mathit{corr}}$

at the high voltage level V +. As soon as the measuring voltage ${\mathit{U}}_{\mathit{mess}}^{\mathit{corr}}$

has reached a level which causes the further switching means 24 to turn on, the binary response signal BS ^korr abruptly rises to its high level. If the delivery of the first test signal P_A is terminated after the corresponding time has expired, the discharge capacitors 27a and 27b are again discharged via the lower resistor 22b of the voltage divider 22 at the branch 14 to the predetermined mean voltage level corresponding to the voltage divider 22.

As already related to FIG. 2 explained, the binary response signal is transmitted to the monitoring device 16, which compares the course of the binary response signal with an expected course. Such a comparison can either be carried out continuously during the entire test run or it can be discontinuous only at certain characteristic points in time to save on the one hand computing capacity of the monitoring device and on the other hand insensitive to insignificant deviations of the binary response signal from the expected course, which is not due to an error in Current path 10 would indicate.

In FIG. 3 For this purpose, two monitoring times t ₁ and t _{2 are} entered, which are indicated in the course of the binary response signals in each case with circles. Consequently, for the correct course of the binary response signal, a low signal level must be set at measurement time t ₁ and a high signal level at measurement time t ₂ . If the monitoring device 16 recognizes the correct course on the basis of the signal levels measured at these times, it closes to one faultless current path 10 and does not take any further action until the next test run is initiated.

In the following, the courses of the respective measuring voltages and the resulting binary response signals for the error cases will be discussed, that one of the two switching devices 12a or 12b is permanently short-circuited or permanently blocked or there is a line break in the relay coil 11.

auf dem durch den Spannungsteiler 22 eingestellten mittleren Spannungsniveau und sinkt nicht, wie nach dem gestrichelt angegebenen Verlauf der korrekten Messspannung ${\mathit{U}}_{\mathit{mess}}^{\mathit{korr}}$

erwartet, auf das niedrige Spannungsniveau V- ab. Entsprechend verharrt auch das binäre Antwortsignal BS ^F1 auf seinem hohen Pegel. Während der Signalpause wird kein Prüfsignal an die Schalteinrichtungen 12a oder 12b abgegeben, so dass sich die Messspannung ${\mathit{U}}_{\mathit{mess}}^{F1}$

und das resultierende binäre Antwortsignal BS^F1 entsprechend nicht ändern. Durch die Abgabe des Prüfsignals P_A an die erste Schalteinrichtung 12a wird diese - da sie korrekt funktioniert - in ihren stromdurchlässigen Zustand gebracht, wodurch sich die am Abzweig 14 anliegende Messspannung nach Aufladung der Dämpfungskondensatoren 27a und 27b auf das hohe Spannungsniveau V+ anhebt. Für den Verlauf des binären Antwortsignals BS ^F1 hat dieses Anheben der Messspannung ${\mathit{U}}_{\mathit{mess}}^{F1}$

auf das hohe Spannungsniveau V+ jedoch keinen Einfluss, da sich das binäre Antwortsignal BS ^F1 bereits auf seinem hohen Pegel befindet. Nach Beendigung des Prüfsignals P_A sperrt die erste Schalteinrichtung 12a wieder und die Dämpfungskondensatoren 27a und 27b entladen sich auf das durch den Spannungsteiler 22 vorbestimmte mittlere Spannungsniveau. Die Überwachungseinrichtung 16 erfasst folglich während des Prüfdurchlaufs ein binäres Antwortsignal BS ^F1 , das dauerhaft auf dem hohen Pegel liegt. Bei diskontinuierlicher Betrachtung zu den Zeitpunkten t₁ und t₂ erkennt die Überwachungseinrichtung 16 zum Zeitpunkt t₁ eine Abweichung des binären Antwortsignals BS^F1 vom erwarteten Verlauf (gestrichelt angegeben), da das binäre Antwortsignal BS ^F1 auf einem hohen Pegel und nicht wie erwartet auf einem niedrigen Pegel liegt. Hieraus schließt die Überwachungseinrichtung 16 auf einen Fehler im Strompfad 10 und gibt ein Fehlersignal ab, um den Betreiber eines das elektromagnetische Relais enthaltenden elektrischen Gerätes zu warnen.First, the error case F1 should be considered that the second switching device 12b permanently blocks due to an error. In this case, the delivery of a test signal P_B to the second switching device 12b has no effect, since the permanently blocking switching device 12b can not be brought into a current-permeable state. Consequently, the corresponding measurement voltage remains ${\mathit{U}}_{\mathit{mess}}^{\mathit{F}1}$

on the set by the voltage divider 22 average voltage level and does not decrease, as indicated by the dashed lines of the correct measurement voltage ${\mathit{U}}_{\mathit{mess}}^{\mathit{corr}}$

expected to depend on the low voltage level V-. Accordingly, the binary response signal BS ^{F 1} remains at its high level. During the signal pause no test signal is delivered to the switching devices 12a or 12b, so that the measuring voltage ${\mathit{U}}_{\mathit{mess}}^{F1}$

and not change the resulting binary response signal BS ^F1 accordingly. As a result of the delivery of the test signal P_A to the first switching device 12a, since it functions correctly, it is brought into its current-permeable state, as a result of which the measuring voltage applied to the branch 14 rises to the high voltage level V + after the damping capacitors 27a and 27b have been charged. For the course of the binary response signal BS ^{F 1} has this raising the measurement voltage ${\mathit{U}}_{\mathit{mess}}^{F1}$

to the high voltage level V + but no influence, since the binary response signal BS ^{F 1 is} already at its high level. After completion of the test signal P_A, the first switching device 12a turns off again, and the damping capacitors 27a and 27b discharge to the mean voltage level predetermined by the voltage divider 22. The monitoring device 16 thus detects during the test run a binary response signal BS ^{F 1} , which is permanently at the high level. When viewed discontinuously at the times t ₁ and t ₂ , the monitoring device 16 detects a deviation of the binary response signal BS ^F1 from the expected curve (indicated by dashed lines) at time t ₁ , since the binary response signal BS ^{F 1 is} at a high level and not as expected low level. From this, the monitoring device 16 detects an error in the current path 10 and outputs an error signal to warn the operator of an electrical device containing the electromagnetic relay.

liegt bereits vor Beginn des Prüfdurchlaufes wegen der kurzgeschlossenen Schalteinrichtung 12b auf dem niedrigen Spannungsniveau V-. Ein Einschalten des Prüfsignals P_B hat hierauf keinen Einfluss, da die Schalteinrichtung sich ohnehin im geöffneten Zustand befindet. Das resultierende binäre Antwortsignal BS ^F2 liegt folglich vor Beginn des Prüfdurchlaufes sowie während der Abgabe des Prüfsignals P_B dauerhaft auf seinem niedrigen Pegel. Während der Signalpause ändert sich der Zustand sowohl der Messspannung ${\mathit{U}}_{\mathit{mess}}^{F2}$

als auch des binären Antwortsignals BS ^F2 nicht, da die kurzgeschlossene Schalteinrichtung 12b den Abzweig 14 dauerhaft auf dem niedrigen Spannungsniveau V- hält. Hieran kann auch die Abgabe des Prüfsignals P_A an die erste Schalteinrichtung 12a nichts ändern; der Abzweig 14 verharrt auch bei geschlossener Schalteinrichtung 12a durch die kurzgeschlossene Schalteinrichtung 12b dauerhaft auf dem unteren Spannungsniveau V-. Aus diesem Fehlerfall F2 wird die Bedeutung der Zeitdauer der Prüfsignale erkennbar, da bei einem zu lang dimensionierten Prüfsignal P_A bei dauerhaft kurzgeschlossener Schalteinrichtung 12b die Ansprechzeit des Relais überschritten würde und somit der Zustand der Relaiskontakte ungewollt verändert werden würde. Nur durch die entsprechend kurze Abgabe des Prüfsignals P_A kann erreicht werden, dass zwar einerseits eine Erfassung des Binärsignals BS^F2 möglich ist, aber andererseits die Ansprechzeit des Relais nicht überschritten wird, so dass sich der Zustand der Relaiskontakte nicht ändert. Der Überwachungseinrichtung 16 wird in diesem Fehlerfall F2 ein dauerhaft auf niedrigem Pegel liegendes binäres Antwortsignal BS ^F2 zugeführt. Bei diskreter Betrachtung des binären Antwortsignals BS ^F2 zu den Zeitpunkten t₁ und t₂ wird eine Abweichung zum Zeitpunkt t₂ erkannt, wo das binäre Antwortsignal AS ^F2 anstelle auf dem erwarteten hohen Pegel auf niedrigem Pegel liegt. Die Überwachungseinrichtung 16 gibt daher ein Fehlersignal zur Anzeige eines Fehlers im Strompfad 10 ab.Next, the fault case F2 is to be considered that the second switching device 12b is permanently short-circuited, so that a current flow through the switching device 12b is constantly possible. The voltage applied to the branch 14 for this case ${\mathit{U}}_{\mathit{mess}}^{F2}$

is already before the beginning of the test run because of the shorted switching device 12b at the low voltage level V-. Switching on the test signal P_B has no influence on this, since the switching device is in any case in the open state. The resulting binary response signal BS ^{F 2} is thus permanently at its low level before the start of the test run and during the delivery of the test signal P_B. During the signal pause, the state of both the measuring voltage changes ${\mathit{U}}_{\mathit{mess}}^{F2}$

and the binary response signal BS ^{F 2} not because the shorted switching device 12b keeps the branch 14 permanently at the low voltage level V-. The delivery of the test signal P_A to the first switching device 12a can not change this; the branch 14 remains permanently at the lower voltage level V- even when the switching device 12a is closed by the short-circuited switching device 12b. From this fault F2 the importance of the duration of the test signals can be seen, since with too long dimensioned test signal P_A at permanently short-circuited switching device 12b the response time of the relay would be exceeded and thus the state of the relay contacts would be changed unintentionally. Only by the correspondingly short output of the test signal P_A can be achieved, that on the one hand a detection of the binary signal BS ^{F2 is} possible, but on the other hand, the response time of the relay is not exceeded, so that the state of the relay contacts does not change. The monitoring device 16 is supplied in this error case F2 a permanently low level lying binary response signal BS ^{F 2} . When the binary response signal BS ^{F 2 is} discretely viewed at the times t ₁ and t ₂ , a deviation is detected at the time t ₂ , where the binary response signal AS ^{F 2 is} at a low level instead of the expected high level. The monitoring device 16 therefore outputs an error signal for indicating an error in the current path 10.

startet in diesem Fall auf dem durch den Spannungsteiler 22 vorbestimmten mittleren Spannungspotential und sinkt bei Abgabe des Prüfsignals P_B aufgrund der dann kurzgeschlossenen zweiten Schalteinrichtung 12b auf das niedrige Spannungsniveau ab. Entsprechend fällt das binäre Antwortsignal BS ^F3 auf seinen niedrigen Pegel. Während der Signalpause laden der Dämpfungskondensator 27b (bei Leitungsbruch in der Relaisspule 11) oder beide Dämpfungskondensatoren 27a und 27b (bei dauerhaft gesperrter erster Schalteinrichtung 12a) über den oberen Widerstand 22a des Spannungsteilers 22 wieder auf, wobei dieser Aufladevorgang wie bereits erwähnt derart langsam geschieht, dass keine Änderung des Zustandes der weiteren Schalteinrichtung 24 erfolgt. Das binäre Antwortsignal BS ^F3 liegt folglich weiter auf niedrigem Pegel. Da in dem hier betrachteten Fehlerfall F3 entweder die erste Schalteinrichtung 12a oder die Relaisspule 11 (oder beide) dauerhaft sperren, kann die Abgabe eines Prüfsignals P_A an die erste Schalteinrichtung 12a keinen Stromfluss durch die Schalteinrichtung 12a und die Relaisspule 11 erzeugen, so dass der Ladevorgang der Dämpfungskondensatoren 27a und 27b über den Widerstand 22a entsprechend langsam fortgesetzt wird, so dass auch während der Abgabe des Prüfsignals P_A die am Abzweig 14 anliegende Messspannung ${\mathit{U}}_{\mathit{mess}}^{F3}$

nicht ausreicht, um die weitere Schalteinrichtung 24 durchzusteuern. Das binäre Antwortsignal BS ^F3 verharrt folglich auf niedrigem Pegel. Der Überwachungseinrichtung 16 wird zu den Zeitpunkten t₁ und t₂ jeweils ein niedriger Pegel des binären Antwortsignals BS ^F3 zugeführt, so dass sie zum Zeitpunkt t₂ eine Abweichung vom erwarteten Verlauf feststellt und ein Fehlersignal abgibt.The next fault F3 includes the two faults that the switching device 12a permanently locks or a line break in the relay coil 11 is present (or both), so that a current flow through the relay coil 11 is not possible. The measuring voltage ${\mathit{U}}_{\mathit{mess}}^{F3}$

starts in this case on the by the Voltage divider 22 predetermined average voltage potential and drops at the delivery of the test signal P_B due to the then shorted second switching device 12b to the low voltage level. Accordingly, the binary response signal BS ^{F 3} falls to its low level. During the signal pause, the damping capacitor 27b (in the case of a line break in the relay coil 11) or both damping capacitors 27a and 27b (with the first switching device 12a permanently locked) re-charge via the upper resistor 22a of the voltage divider 22, this charging process, as already mentioned, occurring so slowly, that no change in the state of the other switching device 24 takes place. The binary response signal BS ^{F 3} is consequently still at a low level. Since in the error case F3 considered here, either the first switching device 12a or the relay coil 11 (or both) permanently block, the delivery of a test signal P_A to the first switching device 12a can not generate a current flow through the switching device 12a and the relay coil 11, so that the charging process the attenuation capacitors 27a and 27b is continued correspondingly slowly via the resistor 22a, so that even during the delivery of the test signal P_A the measuring voltage applied to the branch 14 ${\mathit{U}}_{\mathit{mess}}^{F3}$

is not sufficient to durchzusteuern the further switching device 24. The binary response signal BS ^{F 3} consequently remains at a low level. The monitoring device 16 is supplied at the times t ₁ and t ₂ each have a low level of the binary response signal BS ^{F 3} , so that it detects a deviation from the expected course at time t ₂ and emits an error signal.

in diesem Fall bereits vor Beginn des Prüfdurchlaufs auf dem hohen Spannungsniveau V+. Entsprechend liegt das binäre Antwortsignal BS ^F4 auf dem hohen Pegel. Eine Abgabe des Prüfsignals P_B schließt die zweite Schalteinrichtung 12b und senkt somit das Spannungsniveau am Abzweig 14 auf das niedrige Spannungsniveau V- ab. Diesen Sprung erkennt man entsprechend am Verlauf der Messspannung ${\mathit{U}}_{\mathit{mess}}^{F4}$

und auch an dem daraus resultierenden binären Antwortsignal BS ^F4 . Nach Beendigung des Prüfsignals P_B sperrt die zweite Schalteinrichtung 12b wieder, so dass die Kondensatoren 27a und 27b sehr schnell über die dauerhaft kurzgeschlossene Schalteinrichtung 12a auf das hohe Spannungsniveau V+ aufgeladen werden. Das binäre Antwortsignal BS ^F4 springt folglich schon in der Signalpause wieder auf den hohen Pegel. Eine Abgabe des Prüfsignals P_A an die erste Schalteinrichtung 12a hat folglich keinerlei Effekt mehr auf die Messspannung ${\mathit{U}}_{\mathit{mess}}^{F4}$

und das daraus resultierende binäre Antwortsignal BS ^F4 , da die erste Schalteinrichtung 12a ohnehin dauerhaft kurzgeschlossen ist und sich der Abzweig 14 bereits auf dem hohen Spannungsniveau V+ befindet. Der Überwachungseinrichtung 16 wird in diesem Fehlerfall folglich der in Figur 3 dargestellte Verlauf des binären Antwortsignals BS ^F4 zugeführt. Auch bei diskreter Betrachtung lediglich der Zeitpunkt t₁ und t₂ erkennt die Überwachungseinrichtung 16 eine Abweichung des binären Antwortsignals BS ^F4 vom erwarteten Verlauf zum Zeitpunkt t₁ und gibt ein Fehlersignal ab.Finally, the fault case F4 should be considered that the first switching device 12a permanently short-circuited is. In this case, since the upper resistor 22a of the voltage divider 22 is permanently bypassed, the measurement voltage starts ${\mathit{U}}_{\mathit{mess}}^{F4}$

in this case already at the beginning of the test run at the high voltage level V +. Accordingly, the binary response signal BS ^{F 4 is} at the high level. A delivery of the test signal P_B closes the second switching device 12b and thus lowers the voltage level at the branch 14 to the low voltage level V-. This jump can be recognized according to the course of the measuring voltage ${\mathit{U}}_{\mathit{mess}}^{F4}$

and also on the resulting binary response signal BS ^{F 4} . After completion of the test signal P_B, the second switching device 12b blocks again, so that the capacitors 27a and 27b are charged very quickly via the permanently short-circuited switching device 12a to the high voltage level V +. The binary response signal BS ^{F 4} thus jumps back to the high level already in the signal pause. Consequently, a delivery of the test signal P_A to the first switching device 12a no longer has any effect on the measurement voltage ${\mathit{U}}_{\mathit{mess}}^{F4}$

and the resulting binary response signal BS ^{F 4} , since the first switching device 12a is already permanently short-circuited and the branch 14 is already at the high voltage level V +. The monitoring device 16 is thus in this case, the error in FIG. 3 shown course of the binary response signal BS ^{F 4} supplied. Even with discrete consideration, only the time t ₁ and t ₂ , the monitoring device 16 detects a deviation of the binary response signal BS ^{F 4} from the expected course at time t ₁ and outputs an error signal.

The time sequence of the test run with discontinuous test at the times t ₁ and t ₂ is in FIG. 4 again summarized using a process flow diagram. After the start of the test run ("TEST Start"), the test signal P_B is first output by the drive device 13 to the second switching device 12b according to step 40. According to step 41, a certain period of time, for example 40 μs, is waited for, before the second test signal P_B is switched off again in step 42. In step 43, during the signal pause again a predetermined period of time, for example again 40μs, waited during which no test signal is delivered. After this time has elapsed, it is checked in step 44 whether the binary response signal has reached the expected low level (in FIG. 4 as "0") is located. If this is not the case, an error message is output. However, if the check in step 44 indicates that the binary response signal is at the expected low level, then in step 45, the test signal P_A is turned on to turn on the switching device 12a. The test signal P_A is maintained in step 46 for a predetermined period of time, for example 40μs again, before it is checked in step 47 with the monitoring device 16 whether the binary response signal is at the expected high level (the high level is in FIG. 4 exemplified by "1"). If a deviation of the binary response signal is detected, an error message is again output. If a correct binary response signal is detected, the test signal P_A is turned off in a next step 48 and the test run is successfully completed ("TEST OK").

After a predetermined period of time, the test process can be initiated again with activation of the sequence "TEST Start" to ensure a permanent check of the current path 10.

Based on FIGS. 5 to 7 Now, the monitoring of the current path 10 for the case of a (intentional) current-carrying relay coil 11 is to be displayed. Again, the requirement that the check must have no influence on the state of the relay contacts applies again.

In FIG. 5 First, the turn-on and hold operation of the electromagnetic relay is shown. As is known, a relay coil for driving the relay contacts, for example during switching on of the relay contacts, requires a higher energy input than for holding the relay contacts in their activated position. Consequently, at time t _0, first, the two switching devices 12a and 12b are turned on simultaneously to move the relay contacts. By the simultaneous activation of both switching devices 12a and 12b, a permanently high current flow is ensured by the relay coil 11, so that the contacts can be quickly brought into their activated position. This activation phase of the relay contacts lasts according to FIG. 5 from the start time t ₀ to the time t *, in which the relay contacts have been brought into their activated state.

Thereafter, by a pulsed driving of the second switching device 12b, a so-called pulse-width modulated holding current can be driven through the relay coil 11 which averaged over the time produces a lower power (and thus lower power dissipation in the relay coil) and is sufficient to the relay contacts in their activated To maintain state. Again, the inertia of the electromagnetic relay is exploited, since the magnetic field in the relay coil 11 - as described above - has degraded so far only after a certain response time that the relay contacts would go back to their deactivated state, so that in accordance short pulse this response time always falls below and the relay contacts remain permanently in their activated state.

This approach, by providing a pulse width modulated current flow in the relay coil 11 a total lower holding current for the electromagnetic relay is already known per se.

For monitoring the current path 10, the already pulsed activation of the second switching device 12b is advantageously used as a pulsed test signal P_B for monitoring the corresponding measurement voltage U _mess at the branch 14. For explanation, see FIG. 6 in the upper two diagrams in each case the course of the test signals P_A and P_B during a pulsing of the test signal P_B, as shown in FIG FIG. 5 is highlighted by a border, shown. In this case, the test signal P_A is continuously emitted, while the test signal P_B is delivered pulsed.

sowie des daraus resultierenden korrekten Verlaufs des binären Antwortsignals BS^korr * ist in Figur 6 in den beiden Diagrammen in der zweiten Zeile dargestellt. Der Verlauf der Messspannung ${\mathit{U}}_{\mathit{mess}}^{{\mathit{korr}}^{*}}$

und des binären Antwortsignals BS^korr* soll in Bezug auf Figur 2 erläutert werden.The resulting correct course of the measuring voltage ${\mathit{U}}_{\mathit{mess}}^{{\mathit{corr}}^{*}}$

and the resulting correct course of the binary response signal BS ^corr * is in FIG. 6 shown in the two diagrams in the second line. The course of the measuring voltage ${\mathit{U}}_{\mathit{mess}}^{{\mathit{corr}}^{*}}$

and the binary response signal BS ^corr * should be related to FIG. 2 be explained.

am Abzweig 14 auf das niedrigere Spannungsniveau V-, da hier der untere Widerstand 22b des Spannungsteilers 22 überbrückt wird. Entsprechend sinken sowohl die Messspannung ${\mathit{U}}_{\mathit{mess}}^{{\mathit{korr}}^{*}}$

als auch das resultierende binäre Antwortsignal BS ^korr* sprunghaft ab. Solange das Prüfsignal P_B abgegeben wird, verharren die Messspannung auf dem niedrigen Spannungsniveau V- und das binäre Antwortsignal BS^korr* auf dem niedrigen Pegel. Nach Beendigung des Prüfsignals P_B sperrt die zweite Schalteinrichtung 12b wieder. In der Relaisspule 11 wird durch das plötzlich Unterbrechen des Stromflusses und das sich daher abbauende Magnetfeld eine Überspannung induziert , die sich über einen Stromfluss über den Widerstand 25a und die Diode 25b langsam abbaut. Entsprechend steigt die am Abzweig 14 abgegriffene Messspannung ${\mathit{U}}_{\mathit{mess}}^{{\mathit{korr}}^{*}}$

zunächst über das hohe Spannungsniveau V+ und sinkt dann allmählich wieder auf das hohe Spannungsniveau V+. Bevor der Strom auf einen Wert unterhalb des Haltestromes absinken würde und damit die Magnetfeldstärke nicht mehr ausreichen würde, um die Relaiskontakte in ihrer aktivierten Stellung zu halten, muss das Prüfsignal P_B wieder eingeschaltet werden, um den Strompfad 10 wieder zu schließen.In the event that both the two switching devices 12a and 12b and the relay coil 11 are error-free, the switching device 12a is in its closed state at the beginning of the test sequence, while the switching device 12b is disabled due to the missing test signal P_B. At the branch 14, consequently, the high voltage level V +, which controls the further switching device 24, is established causes and the binary response signal BS ^corr * consequently holds high. When the test signal P_B is output, the then closed switching device 12b pulls the measuring voltage ${\mathit{U}}_{\mathit{mess}}^{{\mathit{corr}}^{*}}$

at the branch 14 to the lower voltage level V-, since here the lower resistor 22b of the voltage divider 22 is bridged. Accordingly, both the measuring voltage decrease ${\mathit{U}}_{\mathit{mess}}^{{\mathit{corr}}^{*}}$

as well as the resulting binary response signal BS ^{korr *} abruptly. As long as the test signal P_B is delivered, the measurement voltage at the low voltage level V and the binary response signal BS ^{corr *} remain at the low level. After completion of the test signal P_B, the second switching device 12b locks again. In the relay coil 11, an overvoltage is induced by the sudden interruption of the current flow and the therefore degrading magnetic field, which degrades slowly via a current flow through the resistor 25a and the diode 25b. Accordingly, the measuring voltage picked up at the branch 14 increases ${\mathit{U}}_{\mathit{mess}}^{{\mathit{corr}}^{*}}$

first over the high voltage level V + and then gradually drops back to the high voltage level V +. Before the current would drop to a value below the holding current and thus the magnetic field strength would no longer be sufficient to hold the relay contacts in their activated position, the test signal P_B must be turned on again to close the current path 10 again.

resultiert folglich ein binäres Antwortsignal BS^korr*, das nach Beendigung der Abgabe des Prüfsignals P_B aufgrund der dann ansteigenden Messspannung ${\mathit{U}}_{\mathit{mess}}^{{\mathit{korr}}^{*}}$

wieder auf seinen hohen Pegel springt.From the in FIG. 6 shown measuring voltage ${\mathit{U}}_{\mathit{mess}}^{{\mathit{corr}}^{*}}$

Consequently results in a binary response signal BS ^{corr *} , after completion of the output of the test signal P_B due to the then increasing measurement voltage ${\mathit{U}}_{\mathit{mess}}^{{\mathit{corr}}^{*}}$

jumps back to its high level.

The monitoring device 16 is the course of the binary response signal BS supplied. As in the de-energized state of the relay coil, a check of the correct course of the binary response signal can be carried out continuously or discontinuously. In FIG. 6 For the discontinuous consideration, two characteristic times t ₃ and t _{4 are} picked out, to which the monitoring device 16 checks the course of the binary response signal. With a correct course of the binary response signal corresponding to BS ^{corr *} , therefore, a low level must be detected at time t ₃ and a high level at time t ₄ .

In the following, the possible recognizable error cases, namely a permanently short-circuited or a permanently locked switching device 12b, a permanently locked switching device 12a or a line break in the relay coil 11 will now be explained.

Since the switching device 12a is permanently held in its closed state by the delivery of a continuous test signal P_A anyway, a state of the first switching device 12a permanently short-circuited by an error can not be detected by means of the test sequence when the relay coil 11 is current-carrying. However, since this would initially lead to any malfunction of the electromagnetic relay - the first switching device 12a should be permanently shorted anyway - the undetectability of such a fault is not a disadvantage of the test run. Such an error would be in the already described above review in the de-energized state of the relay coil can be easily recognized.

am Abzweig 14 unabhängig vom Zustand des Prüfsignals P_B auf dem hohen Spannungsniveau V+. Das hieraus resultierende binäre Antwortsignal BS^F5 verharrt folglich kontinuierlich auf dem hohen Pegel, so dass die Überwachungseinrichtung 16 eine Abweichung des Verlaufs des binären Antwortsignals BS^F5 vom erwarteten Verlauf feststellt. Bei diskontinuierlicher Betrachtungsweise zu den Zeitpunkten t₃ und t₄ stellt die Überwachungseinrichtung 16 beim Zeitpunkt t₃ eine Abweichung des binären Antwortsignals BS^F5 fest, das anstelle auf niedrigem auf hohem Pegel liegt, und kann ein Fehlersignal generieren.First, the error case F5 should be treated so that the second switching device 12b is in a permanently locked state. In such a case, the branch 14 would remain permanently at the high voltage level V + by the intentionally short-circuited switching device 12a. Since a delivery of the test signal P_B due to the faulty permanently locked second switching device 12b has no influence on the switching state of this second switching device 12b, the measuring voltage remains ${\mathit{U}}_{\mathit{mess}}^{F5}$

at the branch 14 regardless of the state of the test signal P_B at the high voltage level V +. The resulting binary response signal BS ^F5 consequently remains continuously at the high level, so that the monitoring device 16 detects a deviation of the course of the binary response signal BS ^F5 from the expected course. In the batchwise approach, at the time points t ₃ and t _4, the monitoring device 16 at time t _3, a deviation of the binary signal BS response ^F5 solid, which is in place at a low to a high level, and may generate an error signal.

am Abzweig 14 durch die dauerhaft kurzgeschlossene Schalteinrichtung 12b kontinuierlich auf dem niedrigen Spannungsniveau V-, so dass sich der Verlauf der Messspannung ${\mathit{U}}_{\mathit{mess}}^{F6},$

wie in Figur 6 gezeigt, ergibt. Die Messspannung ${\mathit{U}}_{\mathit{mess}}^{F6}$

liegt hierbei unabhängig vom Prüfsignal P_B auf dem niedrigen Spannungsniveau V-, so dass auch das resultierende binäre Antwortsignal BS ^F6 dauerhaft auf niedrigem Pegel verharrt. Die Überwachungseinrichtung 16 kann sowohl bei kontinuierlicher als auch bei diskontinuierlicher Überwachung des Verlaufs des binären Antwortsignals folglich eine Abweichung vom erwarteten Verlauf feststellen; bei diskontinuierlicher Betrachtungsweise erkennt die Überwachungseinrichtung 16 zum Zeitpunkt t₄ einen niedrigen Pegel des binären Antwortsignals BS ^F6 anstelle eines erwarteten hohen Pegels, so dass ein Fehlersignal abgegeben werden kann.Next, the error case F6 is to be dealt with that the second switching device 12b is permanently short-circuited. In this case the measuring voltage is ${\mathit{U}}_{\mathit{mess}}^{F6}$

at the branch 14 by the permanently short-circuited switching device 12b continuously at the low voltage level V-, so that the course of the measuring voltage ${\mathit{U}}_{\mathit{mess}}^{F6}.$

as in FIG. 6 shown results. The measuring voltage ${\mathit{U}}_{\mathit{mess}}^{F6}$

This is independent of the test signal P_B at the low voltage level V-, so that the resulting binary response signal BS ^{F 6} remains permanently low level. The monitoring device 16 can monitor both the continuous and the discontinuous monitoring of the course of the binary response signal consequently notice a deviation from the expected course; in a discontinuous view, the monitoring device 16 detects a low level of the binary response signal BS ^{F 6} instead of an expected high level at time t ₄ , so that an error signal can be output.

am Abzweig 14 zunächst bei einem über den Spannungsteiler 22 eingestellten mittleren Spannungsniveau, da auch die zweite Schalteinrichtung 12b den Stromfluss sperrt. Das binäre Antwortsignal BS^F7 startet folglich auf hohem Pegel. Nach Einschalten des Prüfsignals P_B und daraus resultierendem Schließen der zweiten Schalteinrichtung 12b wird die Messspannung ${\mathit{U}}_{\mathit{mess}}^{F7}$

am Abzweig 14 auf das niedrige Spannungsniveau V- gezogen. Daraus resultiert auch ein Absinken des binären Antwortsignals BS^F7 auf den niedrigen Pegel. Die Messspannung ${\mathit{U}}_{\mathit{mess}}^{F7*}$

verharrt auf dem niedrigen Spannungsniveau V-, solange das Prüfsignal P_B die zweite Schalteinrichtung 12b im geschlossenen Zustand hält. Nach Beendigung des Prüfsignals P_B laden sich der Dämpfungskondensator 27b (bei Leitungsbruch in der Relaisspule 11) oder beide Dämpfungskondensatoren (bei dauerhaft gesperrter erster Schalteinrichtung 12a) durch den oberen Widerstand 22a des Spannungsteilers 22 wieder auf das mittleren Spannungsniveau auf.Finally, the fault F7 should be considered that either the relay coil 11 has a line break or the first switching device 12a permanently locks. In this case the measuring voltage starts ${\mathit{U}}_{\mathit{mess}}^{F7}$

at the branch 14 initially at a set via the voltage divider 22 average voltage level, since the second switching device 12b blocks the flow of current. The binary response signal BS ^F7 thus starts at a high level. After switching on the test signal P_B and the resulting closing of the second switching device 12b, the measuring voltage ${\mathit{U}}_{\mathit{mess}}^{F7}$

pulled at the branch 14 to the low voltage level V-. This also results in a lowering of the binary response signal BS ^F7 to the low level. The measuring voltage ${\mathit{U}}_{\mathit{mess}}^{F7*}$

remains at the low voltage level V- as long as the test signal P_B keeps the second switching device 12b in the closed state. After termination of the test signal P_B, the damping capacitor 27b (in the case of a line break in the relay coil 11) or both damping capacitors (with the first switching device 12a permanently locked) recharge to the middle voltage level through the upper resistor 22a of the voltage divider 22.

However, this happens again correspondingly slowly, so that the binary response signal BS ^F7 initially remains at low level. The monitoring device 16 thus detects a Deviation of the binary response signal BS ^F7 from the expected course. In a discontinuous view, the monitor 16 detects a low level at time t ₄ instead of an expected high level of the binary response signal and may issue an error signal.

In FIG. 7 Finally, the sequence of the test procedure is shown in current-carrying relay coil 11 in the event of a discontinuous monitoring of the binary response signal at the times t ₃ and t ₄ . After initiation of the test procedure ("TEST start"), the test signal P_B is turned on in a first step 71. After waiting a short period of time in step 72, a check is made in step 73 as to whether the binary response signal BS has entered a low level ("0").

The time period required in step 72 only has to be dimensioned so long that the response of the binary response signal BS to the second switching device 12b switched on by the test signal P_B can be detected correctly.

If a deviation of the binary response signal BS from the expected low level is detected in step 73 at time t ₃ , an error message is output. If, however, the binary response signal BS corresponds to the expected course in step 73, the test signal P_B is switched off again in step 74 after the expiry of a time period sufficient for the generation of the necessary holding current, and a further short period of time is waited in step 76, which is dimensioned such that a reaction of the binary response signal can be detected. In step 77, it is checked whether the binary response signal BS is at the expected high level. If this is not the case, an error is again output. However, if the binary response signal is at the expected high level, the test run is successfully completed and can be restarted after a predetermined period of time.

The enabled exchange of information between the control device 13 and the monitoring device 16 makes it possible for the monitoring device 16 to include the expected course of the binary response signal matching the respective desired state of the relay coil 11 (either currentless or current flowing through) in its check.

Finally, it should be mentioned that in the discontinuous examination at two characteristic measuring times an exact error differentiation according to the type of error occurred is not consistently possible because usually show several types of errors at the characteristic times corresponding deviations from the desired course of the binary response signal. However, a precise differentiation of the type of fault is often not necessary because the operator of an electrical device in which the electromagnetic relay is used, only interested in whether the relay control is OK or faulty. If one of the possible faults occurs, regardless of the type of fault, the operator will exchange the corresponding switching group with the relay control and the electromagnetic relay in order to ensure the correct functioning of his electrical appliance.

If, nevertheless, a precise error differentiation is desired, then either a continuous monitoring of the binary response signal by means of the monitoring device must be carried out, or the number of measurement times must be correspondingly longer by further characteristic points in time be increased, as this further meaningful deviations of the binary response signal can be specified. In this case, it is possible that the monitoring device also outputs the error type with its error message.

However, even with the described discontinuous approach with only two measurement times, it is conceivable to limit at least the selection of the possible types of errors accordingly. Thus, for example, when checking in the switched-on state the relay coil 11 can be checked when checking the level according to step 77 (cf. FIG. 7 ) are issued at a detected deviation, a more specific error message indicating that either the second switching device 12b is permanently short-circuited or the first switching device 12a permanently locks or the relay coil 11 has a conductor break. Upon checking the level of the binary response signal in step 73 according to FIG FIG. 7 is already a limitation to a permanently locked second switching device 12b possible. Such error messages can be helpful, for example, in repairing a defective relay module or in the search for a systematic error cause.

Claims (13)

1. Switching arrangement for operating an electromagnetic relay which has a relay coil (11) and relay contacts,
   in which

   - two switching devices (12a, 12b) are arranged in a current path (10) with the relay coil such that a first switching device (12a) is connected to a first connection of the relay coil (11) and a second switching device (12b) is connected to a second connection of the relay coil (11); and

   - a control device (13) is provided, which is designed to close both switching devices (12a, 12b) in order to produce a current flow through the relay coil (11), and to open both switching devices (12a, 12b) in order to interrupt a current flow through the relay coil (11); characterized in that

   - the control device (13) is designed to transmit test signals (P_A, P_B) to the first and the second switching devices (12a, 12b), wherein the test signals (P_A, P_B) are created such that they do not influence the instantaneous state of the relay contacts;

   - a measurement voltage (U_meas ) is applied to one input of a conversion device (15) and is tapped off between one connection of the relay coil (11) and one of the switching devices (12a, 12b), wherein the conversion device (15) is designed to convert the measurement voltage (U_meas ) to a binary response signal (BS); and

   - a monitoring device (16) is connected to one output of the conversion device (15), evaluates the profile of the binary response signal (BS) during the transmission of the test signals (P_A, P_B) by the control device (13), and indicates a fault in the relay coil (11) or one of the switching devices (12a, 12b) if the profile of the binary response signal (BS) differs from an expected profile.
2. Switching arrangement according to Claim 1, characterized in that

   - the two switching devices (12a, 12b) are semiconductor switches, in particular transistors.
3. Circuit arrangement according to Claim 1 or 2, characterized in that

   - one connection of in each case one damping capacitor (27a, 27b) is arranged in the current path (10) of the relay coil (11), in each case between one connection of the relay coil (11) and one switching device (12a or 12b).
4. Circuit arrangement according to one of the preceding claims, characterized in that

   - the conversion device (15) has a voltage divider (22) which is arranged in parallel with the current path (10) of the relay coil (11), and to whose voltage divider tap (23) a measurement voltage (U_meas ) is on the one hand applied, and on the other hand the voltage divider tap (23) is connected to a control input of a further switching device (24) in order to obtain the binary signal (BS).
5. Circuit arrangement according to Claim 4, characterized in that

   - the further switching device (24) is a semiconductor switch, in particular a MOSFET.
6. Method for operating an electromagnetic relay which has a relay coil (11) and relay contacts, in which two switching devices (12a, 12b) are closed in order to produce a current flow through the relay coil (11), and two switching devices (12a, 12b) are opened in order to interrupt a current flow through the relay coil (11), wherein the switching devices (12a, 12b) are arranged in a current path with the relay coil (11) such that the first switching device (12a) is connected to a first connection of the relay coil (11), and the second switching device (12b) is connected to a second connection of the relay coil (11); characterized in that

   - a control device (13) emits test signals (P_A, P_B) to the two switching devices (12a, 12b), which test signals (P_A, P_B) do not influence the instantaneous state of the relay contacts;

   - a measurement voltage (U_meas ) is tapped off between one connection of the relay coil (11) and one of the switching devices (12a, 12b);

   - the measurement voltage (U_meas ) is converted to a binary response signal (BS); and

   - a fault in the relay coil (11) or in one of the two switching devices (12a, 12b) is indicated if the profile of the binary response signal (BS) differs from an expected profile.
7. Method according to Claim 6, characterized in that

   - test signals (P_A, P_B) which are shorter than a response time of the relay are emitted to the two switching devices (12a, 12b) with a time offset when no current is flowing through the relay coil (11).
8. Method according to Claim 7, characterized in that

   - when the measurement voltage (U_meas ) is tapped off between the second connection of the relay coil (11) and the second switching device (12b), the test signals (P_A, P_B) are emitted in the following sequence:

   a) a test signal (P_B) is emitted to the second switching device (12b);

   b) no test signal is emitted during a signal pause;

   c) a test signal (P_A) is emitted to the first switching device (12a).
9. Method according to Claim 7, characterized in that

   - when the measurement voltage (U_meas ) is tapped off between the first connection of the relay coil (11) and the first switching device (12b), the test signals (P_A, P_B) are emitted in the following sequence:

   a) a test signal (P_A) is emitted to the first switching device (12a).

   b) no test signal is emitted during a signal pause;

   c) a test signal (P_B) is emitted to the second switching device (12b);
10. Method according to one of the preceding claims, characterized in that

    - when no current is flowing through the relay coil (11), the first switching device (12a) is operated all the time, while the second switching device (12b) is operated via a pulsed test signal (P_B).
11. Method according to one of the preceding claims, characterized in that

    - in order to determine whether there is a fault in the relay coil (11) or one of the switching devices (12a, 12b), the binary response signal (BS) is compared with the expected profile at at least two characteristic times (for example t1 and t2), wherein at least one change relating to the state of at least one test signal (P_A, P_B) has taken place between the characteristic times (for example t1 and t2).
12. Method according to one of the preceding claims, characterized in that

    - the method is repeated at regular time intervals.
13. Method according to one of the preceding claims, characterized in that the control device (13) emits different test signals (P_A, P_B) depending on the state of the relay coil.

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