WO2009062536A1

WO2009062536A1 - Switching arrangement and method for controlling an electromagnetic relay

Info

Publication number: WO2009062536A1
Application number: PCT/EP2007/009999
Authority: WO
Inventors: Harald Kapp; Harald Strohmaier
Original assignee: Siemens Aktiengesellschaft
Priority date: 2007-11-15
Filing date: 2007-11-15
Publication date: 2009-05-22
Also published as: EP2208215A1; CN101889323A; CN101889323B; EP2208215B1

Abstract

The invention relates to a switching arrangement for controlling an electromagnetic relay comprising a relay coil (11) and relay contacts, two switching devices (12a, 12b) being arranged in a current path (10) with the relay coil (11). A control device (13) is provided and set up in such a way as to close the two switching devices (12a, 12b) in order to generate a current flow through the relay coil (11), and to open the two switching devices (12a, 12b) in order to interrupt a current flow through the relay coil (11). The aim of the invention is to provide a circuit arrangement and an above-mentioned method. In order to design such a circuit arrangement in such a way that an anticipatory check of the relay coil (11) and the two switching devices (12a, 12b) for errors is enabled, the control device (13) is designed to send test signals (P_A, P_B) to the first and the second switching devices (12a, 12b). A conversion device (15) is subjected to a measuring voltage ( Umess ) which is converted into a binary response signal (BS). An error in the relay coil (11) or one of the switching devices (12a, 12b) is displayed when the course of the binary response signal (BS) deviates from an expected course. The invention also relates to a corresponding method for controlling an electromagnetic relay.

Description

description

Switching arrangement and method for driving an electromagnetic relay

The invention relates to a switching arrangement for driving a relay coil having a relay relay and having electromagnetic relay in which in a current path with the relay coil two switching devices are arranged such that a first switching device with a first connection of the relay coil and a second switching device with a second connection the relay coil is in communication; a drive device is provided which is set up to close both switching devices in order to produce 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-releasing relays - a closing of the relay contacts is effected so that a current flow via 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 is 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 protection devices for monitoring electrical energy supply networks to cause in the case of a fault (eg a short circuit) in the electrical energy supply network by closing the relay contacts of a so-called "command relay" a draw of an electrical circuit breaker and so interrupt the fault current. When using electromagnetic relays in such safety-related areas, it is of utmost importance to prevent unwanted switching on or off safely, on the one hand to ensure a high level of security in the event of a fault and on the other hand to avoid costly false draws.

In order to carry out a monitoring of the state of the relay contacts, it is initially advisable to feed back their actual state, ie open or closed, to the control device of the relay coil. In the event 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 comparatively complicated, because in this case the galvanic decoupling achieved between the control circuit and the switching circuit for the feedback of the 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 too high switching power or too high temperature, so that the corresponding switching device is permanently short-circuited. In semiconductor switches, such as Transistors are also known to have a similar effect as a so-called "pass-through" of the semiconductor switch terminals, as well as mechanical switches and semiconductor switches that permanently block the current flow due to an internal fault Even an error occur in which, for example by line break no current flow through the relay coil is more lent.

For the most fail-safe configuration of the drive circuit, the relay coil is not only driven by a possibly fault-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 known for example from German Patent DE 44 09 287 Cl, from which a relay coil emerges, which lies with two switching devices in the form of transistors in a current path.

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 above, 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 the current state of the relay contacts influence; an input of a conversion device is acted upon by a measuring 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 with an output of the conversion device, a monitoring device is connected, which evaluates the course of the binary response signal during the transmission of the Prufsignale by the drive means and an error in the relay coil or one of

Indicates switching devices when the course of the binary response signal deviates from an expected course. The particular advantage of the inventive switching arrangement 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 triggering a switching action of the relay contacts, for which only a single measuring signal in the form of the measuring voltage is tapped and monitored in a comparatively inexplicable manner A malfunction of the two switching devices or of the relays - Spool can be achieved advantageously both when switched on and when the relay coil is switched off by the test switches are applied to the two switching devices, which 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 can cause a replacement of the relay and its drive circuit bearing assembly.

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 powers. A further advantageous embodiment of the inventive switching arrangement further provides that in the current path of the relay coil in each case between a terminal of the relay coil and a switching device, a terminal of a Dampfungskondensators is arranged. Due to the steaming effect of the capacitors, the course of the measuring voltage and thus the course of the binary response signal can be extended in time such 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 voltage divider arranged parallel to the current path of the relay coil, whose voltage divider tap on the one hand is acted upon by the measuring voltage and on the other hand fed to a control input of a further switching device for obtaining the binary response signal becomes. 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 suitable in the present case for the conversion of the measured 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, wherein both switching devices are closed to produce 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 with a second terminal of the relay coil in connection, wherein in the inventive method Control device emits test signals 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 displayed 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 when in the opened state of the relay contacts time-delayed Pruf- signals are delivered to the two switching devices, which are shorter than a response time of the relay. In this case, the time is regarded as the response time of the relay, which requires a magnetic field generated by the relay coil to react with sudden change in a voltage applied to the relay coil 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 constructed magnetic field, the magnetic field does not build up until a certain time delay has elapsed. 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 amount of time until its magnetic field strength is 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 to be built up or reduced.

A check of the two switching devices and the relay coil for possible errors can be carried out with the method according to the invention both in the de-energized and in the current-carrying state of the relay coil.

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, for example, be performed by the Pruf signals are issued in the following sequence:

a) a Prufsignal is delivered to the second switching device;

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

c) a Prufsignal 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 in that the first switching device is permanently driven, while the second switching device is controlled via a pulsed test signal.

The time profile of the binary response signal can be compared, for example, continuously with the expected course. A particularly advantageous embodiment of the inventive method, however, provides that to determine whether an error in the relay coil or one of the switching devices is present, the binary response signal is compared to at least two characteristic times with the expected course, wherein between the characteristic times at least a change has occurred with respect to the state of at least one check 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 at two particularly characteristic times must be compared and thus a continuous comparison is not necessary. Since a one-hundred percent congruence of the binary response signal and the expected course is usually difficult to achieve anyway, there is a further advantage of this embodiment is that with a sensible choice of the considered time points - namely in sufficient order at those times to which a Ver - Change of Prufsignale takes place - insignificant differences between the course of the binary response signal and the expected course did not lead to an error message.

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

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

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

1 shows a schematic block diagram of a general embodiment of a switching arrangement for actuating an electromagnetic relay,

FIG. 2 shows a circuit diagram of a possible embodiment of a switching arrangement for actuating an electromagnetic relay,

FIG. 3 shows a plurality of diagrams for explaining exemplary test signals and the measurement voltages and binary response signals produced thereby during a check in the currentless state of the relay coil,

FIG. 4 shows a method flow diagram for explaining an exemplary embodiment of a check in the de-energized state of the relay coil, FIG. 5 shows a test signal sequence for monitoring in the current-carrying state of the relay coil,

FIG. 6 shows a plurality of diagrams for explaining exemplary test signals and the resulting test signals

Measuring voltages and binary response signals in a review in the current-carrying state of the relay coil and

FIG. 7 shows a method flowchart for explaining an exemplary embodiment of a check in the current-carrying state of the relay coil.

FIG. 1 shows a schematic block diagram of an exemplary embodiment of a switching arrangement for actuating an electromagnetic relay. A control 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, wherein the switching devices 12a and 12b are symbolized in Figure 1 only by way of example by mechanical switching devices. The switching devices 12a and 12b may be formed by mechanical switches or semiconductor switches, such as transistors.

For example, the high voltage level V + may be at 10 V while the low voltage level V- is at 0 V. The first switching device 12a is connected to a first terminal IIa the relay coil 11 on the side of the high voltage level V + in conjunction, while the second switching means 12b on the side of the low voltage level V- with a second terminal IIb of the relay coil 11 is in communication. 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 drive device 13 is set up to supply test signals to the drive input of the first and the second switching devices 12a and 12b, as will be explained in more detail later.

At the connection of the second terminal IIb 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 adapted to the measurement voltage U _mess in a binary

Reply signal BS implement and deliver this at its output. The binary response signal BS is fed to a monitoring device 16, which can exchange information with the control device 13. The monitoring device 16 can either - as shown in FIG. 1 - form an independent unit or-in deviation from the representation in FIG. 1-can be integrated into the control device 13. Both the driver 13 and the monitor 16 may include a microprocessor or other logic device (e.g., an ASIC) that controls their operation.

Notwithstanding the representation in FIG. 1, the measuring voltage ε / _me "can also be arranged at the connection between the first switching device 12a and the first connection of the relay coil 11. The sequence of the test signals described below for monitoring the current path 10 is in such a case correspondingly reversed to the two Distribute switching devices 12a and 12b, the error trap described below are also adapted accordingly. In the following examples, however, a tapping of the measuring voltage U _me "according to FIG. 1, that is to say between the second switching device 12b and the second connection of the relay coil 11, should be assumed.

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

FIG. 2 shows a relay coil 11 which is connected on the high voltage level V + side to a first switching device 12a with its first connection IIa, while the second connection IIb of the relay coil 11 is on the low voltage V- side with a second switching device 12b communicates.

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 dashed outline is a

Specified group of switching elements, which corresponds to the conversion device 15 according to FIG. In the embodiment according to FIG. 2, the core piece of the conversion device 15 forms a voltage divider 22, which for example consists of two ohmic resistors 22a and 22b. 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 IIa of the relay coil 11, a terminal of a first Dampfungskondensators 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 IIb of the relay coil 11 is connected to its one terminal, a second Dampfungskondensator 27b, whose second terminal is also at the low voltage level V-.

In the following, the operation of the circuit arrangement shown in Figure 2, 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. For this purpose, reference is also made to FIGS. 3 to 7, with the exception of FIG.

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 go over 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 in which the electromagnetic relay is a command relay for driving an electric circuit breaker, such a malfunction can cause, for example, an unwanted tripping of the circuit breaker or a deliberate triggering 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 is in the de-energized or current-carrying state, different test signals P_A, P_B are output by the control device 13 to the switching devices 12a and 12b, which result in a change in the voltage level at the branch 14.

The voltage applied to this branch 14 measuring voltage U _meiS is fed to the converting device 15, where it is 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 with one another, the monitoring device 16 is able to use the control device 13 to provide information, for example about the beginning of sending the check 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 that 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.

In the following, it will first be explained, with reference to FIGS. 2, 3 and 4, how a check of the current path 10 can take place in the case of (intentionally) a currentless relay coil.

In FIG. 3, the course of the test signals P_A and PB are shown for this purpose in the two upper diagrams, while in the two upper diagrams 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 of each of the respective measured voltages resulting binary response signals for error-free case and for various error cases are.

As can be seen from FIG. 3, a test signal P_B is first supplied to the second switching device 12b to start a test run. This check signal P_B brings the second switching device 12b into 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 current flow resulting from the relay coil 11 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. Normally, the duration of a test signal can be chosen between a lower and an upper limit, the lower limit indicating the time required to be used in the test Umsetzzeinrichtung 15 to generate a correct binary response signal and the upper limit should be at a sufficiently safe distance from the response time of the relay. For example, the possible range for the duration of the test signals may be between about 40 and about 200 μs.

As can be seen from FIG. 3, the delivery of the test signal P_B to the second switching device 12b is ended again after such a short period of time has been selected, followed by a signal pause, during which no test signal is applied to the switching device. facilities 12a or 12b is delivered. Following the switching pause another Prufsignal P_A is delivered to the first switching device 12a, which causes a closing of the switching device 12a. The test signal P_A must also 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 another pause another test run can be started. For example, it can be provided that a renewed test run is initiated every 250 μs.

Arranged in the second line of Figure 3 are graphs showing the profile of the measurement voltage U ^ _e ^r _s ^r _s for the case that both the switching devices 12a and 12b as well as the relay coil 11 are located in a correct, that is error-free state (corr = correct). The course of the measuring voltage t / * ° "will now be explained with reference to Figure 2. For this purpose, it is assumed that the two switching devices 12a and 12b function perfectly and that both are initially in the locked state.

First, the measurement voltage U ^ _e " _{s is} on a mean voltage level predetermined by the voltage divider 22. The binary response signal BS ^k0 " is at a high level, since the measurement voltage ^ε "* is sufficient for the further switching device 24 durchzusteuern. 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

^K O ° _"s is pulled to the low voltage level V- at the branch 14, because the second switching device 12b to the lower resistor Wi 22b of the voltage divider 22 bridged. The profile of the measurement voltage U M in Figure 3 can thus be an abrupt

Be dropped when the test signal P_B the switching device 12b closes. Accordingly, the binary sinks

Response signal BS ^korr to a low level, since the further switching device due to the low-lying

Measuring voltage U ^k ° ^ _s blocks. 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 adequate dimensioning of the steaming 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 U ^ during the signal pause is barely noticeable. The increase in the measuring voltage {/ * "" is at least not sufficient to cause the further switching device 24 of the converter 15 to be in its current-passing state, so that the binary response signal BS ^k " ⁿ remains at the low level during the signal pause When the signal pause P_A acts on the first switching device 12a and brings it into its current-passing state, the damping capacitors 27a and 27b are charged comparatively quickly since the upper resistor 22a of the voltage divider 22 is bypassed and the high voltage level V + is directly applied the Dampfungskondensatoren 27 a and

27b is present. This fast charging process can also be recognized on the Course of the measurement voltage UZL _> ^which rises steeply during the delivery of the second measurement signal P_A. Finally, the measurement voltage ^"au f the high voltage level V +. As soon as the measuring voltage £ / * ° 'is £ / _OT ° has reached a level which causes the WEI tere switching device 24 for switching through that binary response signal BS increases ^corr abruptly to its high Level on. If the delivery of the first test signal P_A ends after the corresponding time has elapsed, the discharge capacitors 27a and 27b are again energized 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 explained in connection with FIG. 2, 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 times in order to save the computation capacity of the monitoring device and to be insensitive to insignificant deviations of the binary response signal from the expected curve Errors in rung 10 were suggestive.

In Figure 3, this two Uberwachungszeitpunkte ti and t ₂ are registered, which are indicated in the course of the binary response signals each with circles. For the correct course of binary response signal to a low signal level must consequently the measurement time ti and the time of measurement t ₂ set a high signal level. If the monitoring device 16 detects 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 course of the respective measured voltages and the resulting binary response signals for the error trap are to be discussed, such that one of the two switching devices 12a or 12b is permanently short-circuited or permanently blocked or a line break exists in the relay coil 11.

First, the error case Fl is to be considered that the second switching device 12b blocks permanently 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-passing state thereby. Consequently, the corresponding measured voltage U ^] _n remains at the value set by the voltage divider 22 average voltage level and does not decrease as expected by the dashed angege- surrounded course of the correct test voltage U ^ ^k _s, to the low voltage level V- from. Accordingly, the binary response signal BS ^hl 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 U ™ "and the resulting binary response signal BS ^F] do not change 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-passing state, as a result of which the measuring voltage applied to the branch 14 rises to the high voltage level V + after the steaming capacitors 27a and 27b have been charged. For the course of the binary response signal BS ^Fl , this raising of the measuring span However, there is no influence on the high voltage level V + since the binary response signal BS ^{r 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 vaporization capacitors 27a and 27b discharge to the middle voltage level predetermined by the voltage divider 22. The monitoring device 16 thus detects during the

Prufdurchlaufs a binary response signal BS ^F] , which is permanently at the high level. With discontinuous consideration at the times ti and t ₂ , the monitoring device 16 detects a deviation of the binary at the time ti

Response signal BS ^fi from the expected course (indicated by dashed lines), since the binary response signal BS ^Fi at a high

Level and not as expected at a low level. From this, the monitoring device 16 closes on a

Error in the current path 10 and outputs an error signal to warn the operator of an electrical device containing the electromagnetic relay.

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 U ™ _M is already before the start of the Prufdurchlaufes 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 the opened state anyway. Consequently, the resulting binary response signal BS ^h2 is permanently at its low level before the beginning of the test run as well as during the delivery of the test signal P_B. During the signal pause, the state of both the measuring voltage changes _M L ^a -L ^{s auc} h the binary response signal BS ^ri not because the shorted switching device 12 b the branch 14 permanently on the low voltage level V- stop. 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. The significance of the duration of the test signals can be recognized from this error case F2, since the response time of the relay was exceeded in the case of a test circuit signal P_A which was too long when the switching device 12b was permanently short-circuited and thus the state of the relay contacts was 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 with a permanently low-level binary response signal BS ^F2 in this error case F2. At more discreet

Considering the binary response signal BS ^ri at the times ti and t ₂ , a deviation is detected at the time t ₂ , where the binary response signal BS ^{12 is} at a low level instead of the expected high level. The monitoring device 16 therefore emits an error signal for indicating a fault in the current path 10.

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 measurement voltage £ / £ / "starts in this case on the by the Voltage divider 22 predetermined average voltage potential and drops at the delivery of the Prufsignals P_B due to the then shorted second switching device 12b to the low voltage level. Accordingly, the binary response signal BS ^F3 drops to its low level. During the

Signal Pause load the Dampfungskondensator 27b (in case of line break in the relay coil 11) or both damping capacitors 27a and 27b (with permanently locked first switching device 12a) on the upper resistor 22a of the voltage divider 22 again, this charging process as mentioned above is so slow, that no change in the state of the other switching device 24 takes place. The binary response signal BS ^F3 is therefore still low

Level. Since in the error case F3 considered here, either the first switching device 12a or the relay coil 11 (or both) permanently disable, 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 Dampfungskondensatoren continues correspondingly slowly through the resistor 22a 27a and 27b, so that even during the discharge of the voltage present at Prufsignals P_A branch 14 measurement voltage U ^F ^ _s is not sufficient in order to control the further switching device 24th The binary response signal BS ^F3 consequently remains at a low level. The monitoring device 16 is supplied at the times ti and t ₂ respectively a low level of the binary response signal BS ^Fi so that it detects a deviation from the expected course at time t2 and emits an error signal.

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, in this case, the measurement voltage C / ™ starts already at the high voltage level V + before the start of the test run. Accordingly, the binary response signal BS ^{1 "4 is} at the high level

Output 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 correspondingly on the course of the measuring voltage U _m ' ⁴ _ss and also on the resulting binary response signal BS ^r4 . To

Termination of the test signal P_B blocks the second switching device 12b 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 ¹⁴ thus jumps back to the high level already in the signal pause. A delivery of the test signal P_A to the first switching device 12a consequently no longer has any effect on the measuring voltage U ^F4 _SS and the resulting binary response signal BS ^F4 , since the first switching device 12a is permanently short-circuited anyway and the branch 14 is already at the high voltage level V + located. The Uberwachungsemrichtung 16 is thus supplied in this case error of the course shown in Figure 3 of the binary response signal BS ^h4 . Even with discrete consideration, only the time ti and t ₂ , the monitoring device 16 detects a deviation of the binary response signal BS ^F4 from the expected course at time ti and outputs an error signal.

The time sequence of the test run in the case of a discontinuous test at the times ti and t ₂ is shown 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 from the drive device 13 to the second switching device 12b according to step 40. According to step 41, a certain time duration, for example 40 μs, is waited for before the second test signal in step 42 P_B is again switched off in step 43. During the signal pause, again a predetermined time duration, for example 40 μs, is waited during which no test signal is output

Step 44 checks to see if the binary response signal is at the expected low level (denoted as "0" in Figure 4), if not, then an error message is output, but if the check in step 44 indicates that the binary response signal is on the the test device PA is turned on in step 45. The test signal P_A is maintained in step 46 for a predetermined period of time, for example 40μs again, before being checked by the monitoring device 16 in step 47, whether the binary response signal is at the expected high level (the high level is exemplified by "1" in Figure 4). 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 procedure can be initiated again with activation of the sequence "TEST start" in order to ensure a permanent check of the current path 10. The monitoring of the current path 10 for the case of a (wanted) current-carrying relay coil 11 will now be illustrated with reference to FIGS. 5 to 7. Again, the requirement that the check must have no influence on the state of the relay contacts applies again.

In Figure 5, the turn-on and hold operation of the electromagnetic relay is shown first. As is known, a relay coil for driving the relay contacts, for example during a switching on of the relay contacts, requires a higher energy supply than for holding the relay contacts in their activated position. Consequently, at the time t0, first, the two switching devices 12a and 12b are simultaneously turned on 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 Figure 5 from the start time to until the time t ^* , in which the relay contacts have been brought into its activated state.

Thereafter, by 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 time, produces less power (and thus also less power dissipation in the relay coil) and is sufficient to supply the relay contacts in their activated 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 were switched back to their deactivated state, so that with a correspondingly short pulsation, this Talk time is always below and the relay contacts 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 PB for monitoring the corresponding measuring voltage U _mes at the branch 14.

For explanation, in the upper two diagrams in FIG. 6 the course of the test signals P_A and P_B during a pulsing of the test signal P B, as highlighted by a border in FIG. 5, is shown. At this time, the test signal P_A is continuously output while the test signal P B is pulsed.

The resulting correct course of the measuring voltage U _mus ^and the resulting correct course of the binary response signal BS ^corr 'is shown in FIG. 6 in the two diagrams in the second line. The course of the measuring voltage UZ ^k l 'and the binary response signal BS ^corr ' will be explained with reference to FIG.

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 checking sequence, while the switching device 12b is disabled due to the missing check 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 'thus halted at a high level. When the test signal P_B is output, the then closed switching device 12b pulls the measuring voltage ^{on the} branch 14 to the lower voltage level V- since here the lower resistance 22b of the voltage divider 22 is bridged. Accordingly, both the measuring voltage U ^ 'and the resulting binary response signal BS ^korr ' abruptly decrease. As long as the test signal P_B is output, the measuring voltage at the low voltage level V and the binary response signal BS ^{corr '} remain at the low level. To

Termination of the test signal P_B blocks the second switching device 12b 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 is a current flow through the resistor 25a and the diode

25b slowly degrades. Accordingly, the measured at the branch 14 measuring voltage U ^k ° ^ 'first rises above the high

Voltage level V + and then gradually decreases again to the high voltage level V +. Before the current was dropped to a value below the holding current and thus the magnetic field strength was no longer 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.

Consequently, a binary response signal BS ^corr 'results from the measurement voltage UZ ^k l ^* shown in FIG. 6, which jumps back to its high level on completion of the output of the test signal P_B due to the then increasing measurement voltage ε. The monitoring device 16, the course of the binary response signal BS is 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, two characteristic times t ₃ and t ₄ are picked out for the discontinuous observation, 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 ^{kon '} , therefore, a low level must be detected at time t ₃ and a high level must be detected 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 kept permanently 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 short-circuited anyway - the undetectability of such a fault is not a disadvantage of the test run. Such an error was in the above-described review in the de-energized state of the relay coil it can easily be ^¬ known. 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 outputting 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 f / _v at the branch 14 remains independent of the state of the test signal PB at the high voltage level V +. The resulting binary response signal BS ^F5 thus remains continuously at the high level, so that the monitoring device 16 detects a deviation of the course of the binary response signal BS ^FS from the expected course. In a discontinuous view of the

At times t ₃ and t ₄ , the monitoring device 16 at time t _3, a deviation of the binary response signal

BS ^FS , which is high instead of low, and may generate an error signal.

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 U ^F * _it 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 U ^, as shown in Figure 6, results. In this case, the measuring voltage ε / ω _w is independent of the test signal PB at the low voltage level V-, so that the resulting binary response signal BS ^F6 remains permanently at a low level. The monitoring device 16 can be used in both continuous and discontinuous monitoring of the course of the binary response. Signal thus determine a deviation from the expected course; in a discontinuous view, the monitoring device 16 detects a low level of the binary response signal BS ^F6 at time t ₄ instead of an expected high level, so that an error signal can be output.

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 U _m ^r _e ^η _ss starts at the branch 14 initially at a set via the voltage divider 22 average voltage level, since the second switching device 12 b blocks the flow of current. The binary response signal BS ^fl 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 UJ ' _iS at the branch 14 is pulled to the low voltage level V-. This also results in a decrease of the binary response signal BS ¹¹ to the low level. The measuring voltage U ^ remains at the low voltage level V- as long as the test signal PB holds the second switching device 12b in the closed state. After completion of the test signal P_B, the steaming capacitor 27b (in the case of a line break in the relay coil 11) or both steaming capacitors (with the first switching device 12a permanently locked) recharge to the average 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 ^F1 initially remains at low level. The monitoring device 16 thus detects a Deviation of the binary response signal BS ^F1 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.

Finally, FIG. 7 shows the sequence of the test passage in the case of a relay coil 11 through which current flows, in the event of a discontinuous monitoring of the binary response signal at the times t ₃ and t ₄ . After an initiation of the

The test signal P_B is turned on in a first step 71. After waiting for a short period of time in step 72, a check is made in step 73 as to whether the binary response signal BS has reached a low level ("0").

The period of time 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 is detectable. 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.

Due to the enabled information exchange between the control device 13 and the monitoring device 16, it is 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 each of two characteristic measuring times an exact error differentiation on the type of error occurred is not continuously possible, since 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, the operator will be the corresponding one irrespective of the fault type

Replace the switch assembly with the relay driver and the electromagnetic relay to ensure correct operation of the electrical equipment.

However, should a precise error differentiation be desired, either a continuous monitoring of the binary response signal by means of the monitoring device must be carried out, or the number of measuring 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 the switched-on state of the relay coil 11 when checking the level in accordance with step 77 (see FIG. 7), a more specific error message is output at a detected deviation, indicating that either the second switching device 12b is permanently short-circuited or the first one Switching device 12a permanently locks or the relay coil 11 has a conductor break. When checking the level of the binary response signal in step 73 according to FIG. 7, a limitation to a permanently blocked second switching device 12b is already 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

claims

1. A switching arrangement for driving a relay coil (11) and relay contacts having electromagnetic relay, wherein

- In a current path (10) with the relay coil two switching devices (12a, 12b) are arranged such that a first switching device (12a) with a first terminal of the relay coil (11) and a second switching device (12b) with a second terminal of the relay coil (11) communicates; and

- A drive device (13) is provided, which is set to, for establishing a current flow through the

Relay coil (11) to close both switching devices (12a, 12b) and to open a current flow through the relay coil (11) to open both switching devices (12a, 12b); d a d u r c h e c e n c i n e s that

- The drive means (13) for emitting Prufsignalen (PA, PB) to the first and the second switching means (12a, 12b) is arranged, wherein the Prufsignale (P_A, P_B) are such that they do not the current state of the relay contacts influence;

- An input of a converting device (15) with a measuring voltage (U _{mes ^} ) is acted upon, which is tapped between a terminal of the relay coil (11) and one of the switching means (12a, 12b), wherein the converting means (15) for converting the measuring voltage (U _mess ) in a binary

Response signal (BS) is set up; and

a monitoring device (16) is connected to an output of the conversion device (15), which during the external dens of the test signals (P_A, P_B) by the control device (13) evaluates the course of the binary response signal (BS) and indicates an error in the relay coil (11) or one of the switching devices (12a, 12b), if the course of the binary response signal ( BS) deviates from an expected course.

2. Switching arrangement according to claim 1, characterized in that the two switching devices (12a, 12b) are semiconductor switches, in particular transistors.

3. A circuit arrangement according to claim 1 or 2, characterized in that - in the current path (10) of the relay coil (11) each between a terminal of the relay coil (11) and a switching device (12a or 12b) a connection respectively of a Dampfungskon- capacitor (27a, 27b) is arranged.

4. Circuit arrangement according to one of the preceding claims, d a d u r c h e c e n e c e s in that e

- The conversion device (15) has a parallel to the current path (10) of the relay coil (11) arranged voltage divider (22) whose Spannungssteilerabgriff (23) on the one hand with the measuring voltage (U _mL ") is applied and on the other hand to

Acquisition of the binary signal (BS) is supplied to a drive input of a further switching device (24).

5. Circuit arrangement according to claim 4, characterized in that a

- The further switching device (24) is a semiconductor switch, in particular a MOSFET.

6. A method for driving a relay coil (11) and relay contacts having electromagnetic relay, in which for establishing a current flow through the relay coil (11) two switching devices (12a, 12b) are closed and to interrupt a current flow through the relay coil (11) both Switching devices (12a, 12b) are opened, wherein the switching devices (12a, 12b) are arranged in a current path with the relay coil (11) such that the first switching device (12a) with a first terminal of the relay coil (11) and the second switching device (12b) is in communication with a second terminal of the relay coil (11); That is, a drive device (13) outputs test signals (P_A, P_B) to the two switching devices (12a, 12b) which do not influence the instantaneous state of the relay contacts;

between a connection of the relay coil (11) and one of the

Switching devices (12a, 12b) a measuring voltage (U _meiS ) is picked up;

- the measuring voltage (U _me ") is converted into a binary response signal (BS); and

- An error in the relay coil (11) or one of the two switching devices (12a, 12b) is displayed when the course of the binary response signal (BS) deviates from an expected course.

7. The method according to claim 6, characterized in that - in the de-energized state of the relay coil (11) with time delay Prufsignale (PA, P_B) to the two switching devices (12a, 12b) are delivered, which are shorter than a response time of the relay.

8. The method of claim 7, wherein a

- When the measurement voltage (U _mess ) between the second terminal of the relay coil (11) and the second switching device (12b) tap the test signals (P_A, P_B) are issued in the following sequence: a) a Prufsignal (P_B) is to the second switching device (12b) delivered; b) during a signal pause no test signal is emitted; c) a test signal (P_A) is delivered to the first switching device (12a).

9. The method of claim 7, wherein a

- When tapping the measuring voltage (f / _me ") between the first

Connection of the relay coil (11) and the first switching device (12b) the test signals (P_A, P_B) are delivered in the following sequence: a) a Prufsignal (P_A) is delivered to the first switching device (12a); b) during a signal pause no Prufsignal abge ^¬ give; c) a test signal (P_B) is delivered to the second switching device (12b).

10. The method according to any one of the preceding claims, characterized in that - in the current-carrying state of the relay coil (11), the first switching device (12a) is permanently driven, while the second switching device (12b) via a pulsed Prufsignal (PB) is driven.

11. The method according to any one of the preceding claims, d a d u r c h e c e n e c e in that e

to determine whether an error is present in the relay coil (11) or one of the switching devices (12a, 12b), the binary response signal (BS) is compared with the expected curve at at least two characteristic times (eg, t1 and t2), between at least one change with regard to the status of at least one test signal (P_A, P_B) has taken place at the characteristic times (eg, t1 and t2).

12. Method according to one of the preceding claims, characterized in that - it is repeated at regular intervals.

13. Method according to one of the preceding claims, characterized in that different test signals (P_A, P_B) are output by the drive device (13) depending on the state of the relay coil.