CN101889323B

CN101889323B - Switching arrangement and method for controlling an electromagnetic relay

Info

Publication number: CN101889323B
Application number: CN200780101582.0A
Authority: CN
Inventors: 哈拉尔德·卡普; 哈拉尔德·斯特罗迈尔
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2007-11-15
Filing date: 2007-11-15
Publication date: 2013-06-19
Anticipated expiration: 2027-11-15
Also published as: WO2009062536A1; CN101889323A; EP2208215B1; EP2208215A1

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 ( U mess ) 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

Switching device and method for controlling an electromagnetic relay

Technical Field

The invention relates to a switching device for controlling an electromagnetic relay having a relay coil and a relay contact, wherein two switching means are arranged in a current path having the relay coil in such a way that a first switching means is connected to a first connection of the relay coil and a second switching means is connected to a second connection of the relay coil; a control device is provided which is designed to close the two switching devices for generating a current through the relay coil and to open the two switching devices for interrupting the current through the relay coil. The invention also relates to a corresponding method for controlling an electromagnetic relay.

Background

In electrical devices, in order to perform controlled switching operations, electromagnetic relays are generally used. Electromagnetic relays are generally composed of a relay coil and at least one pair of relay electrical contacts. If a current is applied to the relay coil, a magnetic field is generated around the relay coil, thereby (in the case of a self-opening relay) causing the relay contacts to close so that a current can pass through the relay contacts. If the current flowing through the relay coil is again interrupted, the movable part of the relay contact is moved back to its original position, for example by means of a spring device, which causes the relay contact to open and the current passing through it to be interrupted. In the case of a self-closing relay, the contacts are closed in the currentless state of the relay coil and open in the currentless state.

Electromagnetic relays are often used where relatively large currents in the switching circuit are to be switched on or off by means of relatively small currents in the control circuit. In this case the electromagnetic relay forms an electrical coupling of the control circuit and the switching circuit.

Electromagnetic relays are used, for example, in electrical protection devices for monitoring electrical supply networks, in order to trigger an electrical circuit breaker and thus to open a fault current in the event of a fault (e.g. a short circuit) in the electrical supply network by closing relay contacts of a so-called "control relay". It is of great importance in the case of the use of electromagnetic relays in these safety-relevant fields to reliably prevent undesired switching on and off in order to ensure, on the one hand, a high level of safety in the event of a fault and, on the other hand, to avoid the need for costly false triggering.

For the state monitoring of the relay contacts, the actual state thereof (i.e. open or closed) can first be fed back to the control device of the relay coil. In the event of a deviation between the nominal state and the actual state of the relay contacts, an error in the control of the relay can be inferred.

However, such monitoring is comparatively complicated, since the electrical decoupling between the control circuit and the switching circuit, which is effected by the relay, must be exceeded here in order to feed back information about the state of the relay contacts. Furthermore, a fault can only be identified when it has occurred (i.e. the relay contacts have had an undesired state). Prospective monitoring is not possible.

This is intended to ensure that the control circuit of the relay coil is opened as reliably as possible in the event of a fault. In the case of switching devices, for example, faults are formed by melting of the switching contacts due to too high switching power or too high a temperature, so that the respective switching device is permanently short-circuited. A similar effect in semiconductor switches such as transistors is known as so-called "fusion" of the contacts of the semiconductor switch. This also occurs in mechanical switching devices and in semiconductor switches, the current being cut off continuously as a result of internal faults. Furthermore, faults can also occur in the relay coil itself, wherein, for example, due to a wire break, no current can flow through the relay coil anymore.

In order to design the control circuit as fail-safe as possible, the relay coil is not controlled only by the single switching device which can be susceptible to failure, but by two switching devices which are located in the current path of the relay coil. The relay coil is only controlled when both switching devices are closed simultaneously. As soon as one switching device is open, the current through the relay coil is switched off. This achieves a relatively high degree of reliability of the control with respect to undesired actuation of the relay coil, since only one harmful short-circuit-sustaining switching device cannot cause undesired actuation of the relay coil. Such a switching device is known, for example, from german patent document DE 4409287C 1, from which a relay coil is derived, which is located in the current path together with two switching devices in the form of transistors.

Disclosure of Invention

The object of the invention is to provide a switching device and a method of the type mentioned at the beginning which allow a prospective inspection of the occurrence of faults of the relay coil and of the two switching means.

The object is achieved by a switching device of the type mentioned at the outset, in which the control device is designed to send a test signal to the first and second switching devices, the test signal being implemented such that it does not influence the instantaneous state of the relay contacts; a measurement voltage tapped off between the terminal of the relay coil and one of the switching devices is applied to an input of a conversion device, the conversion device being designed to convert the measurement voltage into a binary response signal; and a monitoring device is connected to the output of the switching device, which during the transmission of the test signal evaluates a change in the binary response signal by the control device and indicates a fault in the relay coil or in one of the switching devices if the binary response signal deviates from the expected change.

A particular advantage of the switching device according to the invention is that the correct functioning of the relay coil and of the two switching means can be monitored relatively simply already when a faulty switching operation of the relay has not yet been carried out. In this way, a possible failure of the relay coil and of the two switching devices can be detected proactively. The term "prospective" means that the functionality can be checked without causing a switching operation of the relay contacts. For this purpose, only one single measurement signal in the form of a measurement voltage is tapped and monitored in a comparatively simple manner. By using test signals applied to both switching devices (which however do not affect the instantaneous state of the relay contacts), a malfunction of both switching devices or of the relay coil can preferably be detected both in the closed state and in the open state of the relay coil.

If a fault is detected in one of the switching devices or in the relay coil during monitoring, an operator of the device in which the electromagnetic relay is installed (for example, the operator of the corresponding electrical protection device) can be informed about the fault alarm associated therewith, so that it can initiate a replacement of the component with the relay and its control circuit.

According to a preferred embodiment, the two switching devices are semiconductor switches, in particular transistors. The semiconductor switches can be switched on or off particularly quickly and with low switching power.

In a further preferred embodiment of the switching device according to the invention, in the current path of the relay coil, a connection of a damping capacitor is provided between a connection of the relay coil and a switching device. The damping action of the capacitor can temporally delay (getterckt) the change in the measurement voltage and thus the change in the binary response signal, so that an especially simple evaluation is possible.

In a further preferred embodiment of the switching device according to the invention, the switching means has a voltage divider arranged parallel to the current path of the relay coil, the tap of which voltage divider is applied to the measurement voltage on the one hand and is transmitted to the control input of the other switching means in order to obtain a binary response signal on the other hand. In this way, a binary response signal can be generated from the measurement voltage without a large circuit complexity.

The further switching device may be, for example, a semiconductor switch, in particular a MOSFET (metal oxide semiconductor field effect transistor). The field effect transistor is controlled by a voltage and is therefore particularly well suited in the present case for measuring the conversion of a voltage into a binary response signal.

The above-mentioned object is achieved by a method for controlling an electromagnetic relay having a relay coil and relay contacts, wherein two switching devices are closed for generating a current through the relay coil and are opened for interrupting the current through the relay coil, wherein the switching devices are arranged in a current path having the relay coil such that a first switching device is connected to a first connection of the relay coil and a second switching device is connected to a second connection of the relay coil, wherein in the method according to the invention the control device outputs a test signal to the two switching devices which does not influence the momentary state of the relay contacts; measuring a measurement voltage between a terminal of the relay coil and one of the switching devices; the measurement voltage is converted into a binary answer signal; and if the change in the binary answer signal deviates from the expected change, a fault in the relay coil or in one of the two switching devices is indicated. With the method, the control circuit of the electromagnetic relay can be checked in a preferred manner.

In a preferred embodiment, time-shifted test signals are output to the two switching devices in the open state of the relay contacts, which test signals are shorter than the response time of the relay. The following time is considered here as the response time of the relay: in the case where the voltage applied to the relay coil changes suddenly, the magnetic field generated by the relay coil requires that time to respond with a change in the switching state of the relay contacts.

For example, if the relay coil is switched off at a completely established magnetic field, the magnetic field decays first with a certain time delay. The relay contacts change their state only when the magnetic field strength is no longer sufficient to keep the relay contacts in their position so far. If the relay coil is again switched on in good time, the magnetic field is built up again and the relay contacts remain without changing their state.

In the opposite case, when a voltage is suddenly applied to the (previously currentless) relay coil, the magnetic field of the relay coil needs a certain duration until its magnetic field strength is sufficient to control the relay contacts. If the current is again switched off in time, the relay contacts do not change their state.

The test signal must therefore be so short in terms of its duration that no change in the state of the relay contacts occurs due to the inertia of the magnetic field which is established or reduced.

With the method according to the invention, both the switching devices and the relay coil can be checked for possible faults both in the currentless state and in the currentless state of the relay coil.

In particular, in the currentless state of the relay coil and with the measurement voltage tapped between the second connection of the relay coil and the second switching device, the test is carried out by outputting test signals in the following order:

a) outputting the test signal to a second switching device;

b) not outputting the check signal during the signal pause period;

c) the check signal is output to the first switching device.

In the case of a measurement voltage being tapped between the first terminal of the relay coil and the first switching device, the test signal is correspondingly distributed in the opposite direction to the switching device.

According to a preferred development, the test can be carried out with a current flowing through the relay coil by continuously controlling the first switching device and by pulsing the test signal to control the second switching device.

For example, a change in the binary answer signal can be continuously compared with an expected change. In a particularly preferred embodiment of the method according to the invention, however, the binary response signal is compared with the expected change at least two characteristic times in order to determine whether a fault has occurred in one of the relay coil or the switching device, wherein at least one change in state of at least one test signal has occurred between the characteristic times. The computational performance of the monitoring device required for the comparison in this embodiment remains relatively small, since in the simplest case only the change in the binary response signal and the expected change at two particular characteristic times have to be compared and therefore no continuous comparison is required. Since it is often difficult to achieve the same one hundred percent of the binary answer signal and the expected change, a further advantage of this embodiment is that insignificant deviations between the change of the binary answer signal and the expected change do not lead to a malfunction alarm in an efficient choice of investigation instants-i.e. at a sufficient distance from those instants at which the change of the test signal occurs.

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

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

Drawings

The invention is explained in detail below with the aid of examples. Wherein,

figure 1 shows a schematic block diagram of a general embodiment of a switching device for controlling an electromagnetic relay,

figure 2 shows a circuit diagram of a possible embodiment of a switching device for controlling an electromagnetic relay,

fig. 3 shows a plurality of diagrams for explaining exemplary test signals and the resulting measurement voltages and binary response signals in the case of a test in the currentless state of the relay coil,

figure 4 shows a method flow diagram for explaining an embodiment of the test in the currentless state of the relay coil,

figure 5 shows a check signal sequence for monitoring of the current-free state of the relay coil,

fig. 6 shows several diagrams for explaining exemplary test signals and the resulting measurement voltages and binary response signals in the case of a test of a relay coil in the current state, an

Fig. 7 shows a method flowchart for explaining an exemplary embodiment of a test of a current state of a relay coil.

Detailed Description

Fig. 1 shows a schematic block diagram of an embodiment of a switching device for controlling an electromagnetic relay. The control circuit of the electromagnetic relay comprises in the current path 10 a series circuit of a relay coil 11 in series with a first switching device 12a and a second switching device 12b, wherein the

switching devices

12a and 12b are represented in fig. 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.

The high voltage level and the low voltage level are denoted by "V +" and "V-". For example, the high voltage level may be at 10V, while the low voltage level may be at 0V. The first switching device 12a is connected to the first terminal 11a of the relay coil 11 on the high voltage level V + side, and the second switching device 12b is connected to the second terminal 11b of the relay coil 11 on the low voltage level V-side.

The first and

second switching devices

12a and 12b are connected with their control inputs to the control device 13. The

switching devices

12a and 12b can be switched on or off by the control device 13. The control device 13 is designed to output a test signal to the control inputs of the first and

second switching devices

12a and 12b, as explained in more detail below.

The measurement voltage U is tapped via a branch 14 during the connection of the second terminal 11b of the relay coil 11 to the second switching device 12b_messAnd transmitted to the conversion means 15. The switching device 15 is used for measuring the voltage U_messConverted into a binary answer signal BS and output it to its output. The binary response signal BS is transmitted to a monitoring device 16, which can exchange information with the control device 13. As shown in fig. 1, the monitoring device 16 may either form a separate unit or (unlike the one shown in fig. 1) be integrated into the control device 13. Both the control means 13 and the monitoring means 16 may have a microprocessor or other logic component (e.g. an ASIC) controlling their operating mode.

The voltage U is measured differently from that shown in fig. 1_messIt is also possible to provide a connection between the first switching means 12a and the first connection of the relay coil 11. In this case, the sequence of the test signals described below for monitoring the current path 10 is distributed in each case in reverse to the two

switching devices

12a and 12b, and the fault conditions described below are likewise adjusted accordingly. However, in the following example, the voltage U is measured from the voltage U according to fig. 1 (i.e. between the second switching device 12b and the second connection of the relay coil 11)_messThe amount of (1) is calculated.

In one possible specific embodiment, a switching device for controlling an electromagnetic relay is configured, for example, as shown in fig. 2. The same reference numerals are used in fig. 2 for corresponding components in fig. 1.

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

The

switching devices

12a and 12b are illustrated in fig. 2 as semiconductor switches in the form of transistors.

The frame shown by means of dashed lines illustrates the group of switching elements, which corresponds to the switching device according to fig. 1. The core component of the switching device 15 in the embodiment according to fig. 2 forms a voltage divider 22, which is composed, for example, of two

ohmic resistors

22a and 22 b. Between the 3 two

ohmic resistors

22a and 22b is located a voltage divider tap 2 which is connected on the one hand to the branch 14 for measuring the voltage and on the other hand to the control input of a further switching device 24.

A series circuit 25, which is arranged in parallel with the relay coil 11 and the switching device 12a and is composed of an ohmic resistor 25a and a diode 25b, serves to capture an overvoltage which may occur in the event of a current interruption through the relay coil 11. The other ohmic resistor 26 is used to adjust the voltage level of the binary answer signal BS.

A first damping capacitor 27a, which is connected with its other connection to the low voltage level V-, is connected with one connection to the first switching device 12a and to the first connection 11a of the relay coil 11. Correspondingly, a second damping capacitor 27b, whose second connection is likewise located at the low voltage level V-, is connected with its one connection to the connection between the second switching device 12b and the second connection 11b of the relay coil 11.

The operating principle of the switching device shown in fig. 2 is explained in detail below, in particular with regard to the checking of possible errors of the two

switching devices

12a and 12b and of the relay coil 11. For this purpose, reference is made to fig. 3 to 7 in addition to fig. 2.

The control device 13 is first used to generate or interrupt the current through the relay coil 11 by simultaneously opening or closing the

switching devices

12a and 12 b. The current through the relay coil 11 is generated by simultaneously closing the two

switching devices

12a and 12b, as a result of which a corresponding magnetic field is generated in the relay coil 11 and, starting from a certain magnetic field strength, a change in the state of the relay contacts (not shown) of the electromagnetic relay results. In order to interrupt the current flow 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 is reduced again. If the field strength generated by the magnetic field is not sufficient to hold the relay contacts in their position, the relay contacts are switched to their normal position, for example by the action of a spring force.

In the event of a fault in one of the two

switching devices

12a and 12b or in the relay coil 11, a defined control of the relay coil 11 and of the switching circuit provided thereby at the relay contacts is no longer ensured. For the exemplary case in which an electromagnetic relay is a control relay for controlling an electrical circuit breaker, an undesired false triggering of the circuit breaker or a desired triggering of the circuit breaker is prevented, for example, by such a fault. The current path 10, which is composed of the two

switching devices

12a and 12b and the relay coil, is thus checked. Depending on whether the relay coil 11 is in the currentless state or the currentless state, different test signals P _ A, P _ B are output at the control device 13 to the control devices 12a and 12B, which result in a change in the voltage level at the branch 14.

A measurement voltage U applied to this branch 14_messAnd also to the conversion means 15 where the measurement voltage is converted into a binary answer signal BS. The monitoring device 16 compares the change of the binary answer signal BS with the expected change and identifies a fault in the current path 10 when the expected change and the actual change of the binary answer signal BS deviate from each other. In order to be able to compare the expected changes and the actual changes of the binary answer signal BS with one another, the monitoring device 16 can exchange information with the control device 13, for example, in order to know about the start of the transmission of the test signal P _ A, P _ B to the two switching devices 12a and 12B.

When the monitoring device 16 identifies a fault in the current path 10, a corresponding fault alarm can be output, which informs the operator of the apparatus in which the electromagnetic relay is installed about the fault. The operator of the respective device can then replace the respective faulty component before the actual failure of the electromagnetic relay has occurred.

The checking of the current path 10 for possible faults can be carried out both in the currentless state of the relay coil and in the current-flowing state and accordingly in the open or closed state of the relay contacts without influencing the state of the relay contacts.

In the following, it is first explained in conjunction with fig. 2, 3 and 4 how the checking of the current path 10 can be carried out with a (desired) currentless relay coil.

In fig. 3, the change of the test signal P _ A, P _ B is shown for this purpose in the upper two diagrams, while in the following ten diagrams the measurement voltage applied to the branch 14 is shown on the left for the non-faulty situation and for different faulty situations, and the binary response signal resulting from the respective measurement voltage is shown on the right for the non-faulty situation and for different faulty situations.

As can be gathered from fig. 3, at the beginning of the test process, the test signal P _ B is first transmitted to the second switching device 12B. The check signal P _ B brings the second switching means 12B into its closed state.

The duration of the test signal P _ B is implemented in such a way that, in the event that the first switching device 12a should continue to short-circuit due to a fault, the duration of the current which is then generated by the relay coil 11 has no influence on the state of the relay contacts. The duration of the check signal P _ B must therefore be less than the response time of the relay already explained above. For this purpose, the duration of the test signal can generally be selected between a lower limit and an upper limit, the lower limit giving the time required for generating a correct binary response signal in the switching device 15 and the upper limit being to be situated at a sufficiently safe interval from the response time of the relay. For example, the possible range for the duration of the test signal may be between about 40 and about 200 mus.

As can be gathered from fig. 3, the output of the test signal P _ B to the second switching device 12B is ended again after the short duration thus selected, and a signal pause follows, during which no test signal is output to the switching device 12a or 12B. After the switch has been suspended, a further test signal P _ a is output to the first switching means 12a, which test signal causes the switching means 12a to close. The duration of the test signal P _ a must also be completed so short that the state of the relay contacts is not affected even if the second switching device 12b should be in a permanent short-circuit state when it fails. The duration of the check signal P _ a must therefore also be lower than the response time of the relay.

After ending the sequence of check signals, ending the checking process; the verification process may continue after any pauses. So that a new test procedure can be started every 250 mus, for example.

In the diagram in the second row of fig. 3, the measured voltage is shown for the

switching devices

12a and 12b and the relay coil 11 in the correct, i.e. non-defective, state

(correct) is used. The measurement voltage will now be explained with reference to fig. 2

A change in (c). For this purpose, it is assumed that the two

switching devices

12a and 12b operate without problems and that both are initially in the blocking state.

First, the voltage is measured

At an intermediate voltage level predetermined by the voltage divider 22. Binary answer signal BS^korrAt a high level because of the measurement voltageIt is sufficient to switch on (durchzusteuern) the further switching means 24. By outputting the test signal P _ B to the second switching device 12B, the switching device 12B is closed and the voltage is measured at the branch 14

Is brought to a low voltage level V-because the second switching means 12b is connected across the lower resistor 22b of the voltage divider 22. The voltage is thus measured from fig. 3 as soon as the test signal P _ B closes the switching device 12B

Can learn of a sudden drop. Accordingly, the binary answer signal BS^korrFalls to a low level because of the low measuring voltage applied by the other switching device

And is cut off. After the end of the test signal P _ B, the second switching means 12B again switches to the blocking state, and the previously discharged damping capacitors 27a and 27B are charged via the upper resistor 22a of the voltage divider 22. When the damping

capacitors

27a and 27b and the ohmic resistor 22a of the voltage divider are sufficiently large, the charging process is however so slow that the voltage is measured during signal pauses

The increase in (c) is hardly noticeable. Measuring voltage

Is at least insufficient to switch the further switching means 24 of the switching means 15 into a state in which it has a current flowing, so that the binary answer signal BS^korrFurther remaining low during signal pauses. When, after a signal pause, the test signal P _ a is applied to the first switching means 12a and brings it into a state in which it is flowing through, the damping

capacitors

27a and 27b are charged comparatively quickly, since the upper resistor 22a of the voltage divider 22 is bridged and a high voltage level V + is applied directly to the damping

capacitors

27a and 27 b. At the measuring voltageThis rapid charging process can also be seen on the change in (which rises steeply during the output of the second measurement signal P _ a). Finally measuring the voltage

At a high voltage level V +. As long as the voltage is measuredTo a level which permits the second switching means 24 to be switched on, a binary answer signal BS is reached^korrSuddenly rising to its high level. If the output of the first test signal P _ a ends after the lapse of the corresponding time duration, the voltage is set again on the branch 14 via the lower resistor 22b of the voltage divider 22 after the discharge of the damping

capacitors

27a and 27b to an intermediate voltage level, which is predetermined by the voltage divider 22 accordingly.

As already explained in connection with fig. 2, the binary answer signal is transmitted to the monitoring device 16, which compares the change of the binary answer signal with the expected change. Such a comparison can be carried out either continuously over the entire checking process or discontinuously only at specific characteristic times, in order to save on the one hand the computational capacity of the monitoring device and on the other hand to be insensitive to insignificant deviations of the binary response signal from the expected change, which do not indicate a fault in the current path 10.

For this purpose, fig. 3 shows two monitoring times t₁And t₂Which are respectively indicated by circles in the binary change of the answer signal. For a correct change of the binary answer signal, it is therefore necessary to measure the time t₁Set low signal level and at measurement time t₂A high signal level is set. If the monitoring device 16 identifies a correct change from the signal level measured at this point in time, a fault-free current path 10 is deduced and no further processing is carried out until the next test procedure is started.

The change of the respective measurement voltages and the binary response signals generated therefrom are discussed below for the case of a fault in which one of the two

switching devices

12a or 12b is permanently short-circuited or permanently switched off or a wire break occurs in the relay coil 11.

First, a fault situation F1 is considered in which the second switching device 12b is continuously switched off as a result of a fault. In this case, the output of the check signal P _ B to the second switching device 12B has no effect, because the interception is continuedThe stationary switching device 12b can thus not be brought into a state in which a current flows. Thus corresponding measured voltage

Is maintained at the intermediate voltage level set by the voltage divider 22 and the correct measurement voltage as indicated by the dashed line

Is expected not to drop to the low voltage level V-. Accordingly, a binary answer signal BS^F1Remains at its high level. No test signal is output to the

switching device

12a or 12b during the signal pause, so thatAnd the generated binary answer signal BS^F1And accordingly does not change. By checking the output of signal P _ a to first switching device 12a, which, because it is operating correctly, is brought into a state in which it has a current flowing, the measurement voltage applied to branch 14 rises to a high voltage level V + after damping

capacitors

27a and 27b have been charged. However measuring the voltage

This rise to the high voltage level V + is for the binary answer signal BS^F1Has no influence because of the binary answer signal BS^F1Already at its high level. After the end of the test signal P _ a, the first switching device 12a is again switched off and the damping

capacitors

27a and 27b discharge to an intermediate voltage level predetermined by the voltage divider 22. The monitoring device 16 therefore collects the binary response signal BS during the test procedure^F1The answer signal is continuously at a high level. At time t₁And t₂In the case of discrete investigation, the monitoring device 16 is at time t₁Identification of binary answer signals BS^F1Deviation from the expected variation (indicated by the dashed line) because of the binary answer signal BS^F1At a high level rather than at a low level as expected. Thereby monitoring the device 16A fault in the current path 10 is inferred and a fault signal is output in order to warn an operator of the electrical apparatus comprising the electromagnetic relay.

Next, a fault condition F2 is considered in which the second switching device 12b is continuously short-circuited and thus there is always a current through the switching device 12 b. For this case, the measurement voltage applied to the branch 14

The low voltage level V-is already present before the start of the test process due to the short-circuited switching means 12 b. The switching on of the test signal P _ B has no effect on this, since the switching device is in the off state. Generated binary answer signal BS^F2And therefore is continuously at its low level before the start of the verification process and during the output of the verification signal P _ B. Measuring voltage during signal pauses

And binary answer signal BS^F2Is not changed because the short-circuited switching means 12b keep the branch 14 continuously at the low voltage level V-. The output of the test signal P _ a to the first switching means 12a may also be unchanged here; the branch 14 is also continuously held at the low voltage level V-by the short-circuited switching device 12b in the case of the closed switching device 12 a. The meaning of the duration of the test signal can be recognized from this fault situation F2, since in the case of a test signal P _ a that is too long, the response time of the relay is exceeded in the switching device 12b of the continuity circuit, and the state of the relay contacts is thereby undesirably changed. This can only be achieved by a correspondingly short output of the test signal P _ a, although on the one hand a binary signal BS can be detected^F2But on the other hand does not exceed the response time of the relay so that the state of the relay contacts does not change. Binary answer signal BS, which is to be continuously at low level in this fault situation F2^F2To the monitoring device 16. At time t₁And t₂Discrete investigation of binary answer signal BS^F2In the case of (1), at time t₂Identify deviations inWhere a binary answer signal BS^F2Not at the intended high level but at the low level. The monitoring device 16 thus outputs a fault signal for indicating a fault in the current path 10.

The next fault condition F3 includes two faults, namely, the switching device 12a is continuously off or a wire break occurs in the relay coil 11 (or both), so that no current flows through the relay coil 11. In this case, the voltage is measured

Starting from an intermediate voltage potential predetermined by the voltage divider 22 and dropping to a low voltage level in the case of the output of the test signal P _ B due to the second switching means 12B which is then short-circuited. Binary answer signal BS^F3And correspondingly drops to its low level. During the signal pause (in the event of a wire break in the relay coil 11), the damping capacitor 27b or (in the event of a continuous blocking of the first switching device 12a) the two damping

capacitors

27a and 27b are charged via the upper resistor 22a of the voltage divider 22, the charging process, as already mentioned, proceeding so slowly that no change in state of the other switching device 24 takes place. So that the binary answer signal BS^F3Continues to be at a low level. Since, in the fault situation F3 considered here, either the first switching device 12a or the relay coil 11 (or both) are continuously switched off, the output of the test signal P _ a to the first switching device 12a does not result in a current flow through the switching device 12a and the relay coil 11, so that the charging process of the damping

capacitors

27a and 27b via the resistor 22a continues correspondingly slowly, so that the measurement voltage applied to the branch 14 during the output of the test signal P _ a is present

Is not sufficient to conduct (durchzusteuern) the further switching device 24. So that the binary answer signal BS^F3Remains at a low level. At time t₁And t₂Respectively sending binary answer signals BS^F3Is transmitted to the monitoring means 16 so that it is at time t₂A deviation from the expected variation is determined and a fault signal is output.

Finally, the fault situation F4 in which the first switching device 12a is permanently short-circuited is examined. Since the upper resistor 22a of the voltage divider 22 is continuously bridged in this case, the upper resistor 22a is connected in this caseThe high voltage level V + is already started before the start of the test process. Accordingly, a binary answer signal BS^F4At a high level. The output of the test signal P _ B closes the second switching means 12B and thus the voltage level on the branch 14 drops to the low voltage level V-. Accordingly, the voltage is measuredAnd also on the binary answer signal BS generated therefrom^F4Identifies the transition. After the end of the test signal P _ B, the second switching device 12B is switched off again, so that the capacitors 27a and 27B are charged very quickly to the high voltage level V + via the continuously short-circuited switching device 12 a. So that the binary answer signal BS^F4And transitions back to high during the signal pause. The output of the test signal P _ a to the first switching device 12a therefore no longer corresponds to the measured voltage

And a binary answer signal BS generated therefrom^F4Any influence is produced because the first switching means 12a is in any case permanently short-circuited and the branch 14 is already at the high voltage level V +. In this case, the binary answer signal BS will therefore be shown in fig. 3^F4Is transmitted to the monitoring device 16. Also only at time t₁And t₂In the case of discrete investigation, the monitoring device 16 is at time t₁Identification of binary answer signals BS^F4Deviation from the expected variation and outputting a fault signal.

Fig. 4 again shows a schematic representation of the method at time t by means of a method flowchart₁And t₂Discrete inspectionThe course of the process over time is verified. After the start of the test procedure ("test start"), a test signal P _ B is first output by the control device 13 to the second switching device 12B in accordance with step 40. A certain time duration, for example 40 μ s, is waited according to step 41, and the second test signal P _ B is then switched off again in step 42. In step 43, a further predetermined time duration, for example again 40 μ s, is waited for during the signal pause, during which time duration no test signal is output. After the duration has elapsed, it is checked in step 44 whether the binary answer signal is at the expected low level (indicated as "0" in fig. 4). If not, a fault alarm is output. If, however, in step 44 the test has resulted that the binary answer signal is at the expected low level, the test signal P _ a is switched on in accordance with step 45 in order to switch on the switching means 12 a. In step 46, the test signal P _ a is held for a predetermined time duration, for example, again 40 μ s, and then in step 47 it is checked by means of the monitoring device 16 whether the binary answer signal is at the expected high level (this high level is exemplarily indicated by "1" in fig. 4). If a deviation of the binary response signal is determined, a fault alarm is output again. If a correct binary answer signal is recognized, the test signal P _ a is interrupted in a next step 48 and the test procedure is successfully ended ("test OK").

The test procedure can be re-introduced by activating the sequence "test start" after the lapse of a predetermined time duration in order to ensure a continuous test of the current path 10.

The monitoring of the current path 10 for the case of a (undesired) current flowing through the relay coil 11 is now to be shown with the aid of fig. 5 to 7. In this case, the following requirements apply: this check does not allow any influence on the state of the relay contacts.

Fig. 5 first shows the switching and holding operation of the electromagnetic relay. It is known that, in order to control the relay contacts, for example during the switching-on of the relay contacts, the relay coil requires a higher energy supply than the holding of the relay contacts in their controlled stateShould be used. Thus at time t₀First, both switching

devices

12a and 12b are switched on simultaneously for the movement of the relay contacts. By simultaneously controlling the two

switching devices

12a and 12b, a continuously high current flow through the relay coil 11 is ensured, so that the contacts can be brought quickly into their active position. According to fig. 5, this activation phase of the relay contacts is initiated from a starting point t₀Continues until the time t at which the relay contact is brought into its active state^*。

By means of the pulsed control of the second switching device 12b, a so-called pulse-width-modulated holding current can then be driven through the relay coil 11, which produces a small power (and thus also a small power loss in the relay coil) in the interim and is sufficient to hold the relay contacts in their activated state. The inertia of the electromagnetic relay is also used here, since the magnetic field in the relay coil 11 (as already described above) is reduced only after a certain response time to the extent that the relay contacts are again switched to their deactivated state, so that in the case of correspondingly short pulses the response time is always below this and the relay contacts remain permanently in their activated state.

This operating principle of providing an electromagnetic relay with a generally small holding current by means of a pulse-width-modulated current in the relay coil 11 is known per se.

For monitoring the current path 10, the originally pulsating control of the second switching device 12b is preferably used as a control for monitoring the respective measurement voltage U at the branch 14_messTogether with the pulsed check signal P _ B. For the sake of explanation, fig. 6 in the upper two diagrams shows the change of the test signals P _ a and P _ B during a pulse of the test signal P _ B, as is highlighted by a circle in fig. 5. The check signal P _ a is continuously output and the check signal P _ B is output in a pulsating manner.

The resulting measurement voltage

And the binary answer signal generated therefrom

The correct variation of (d) is shown in the two diagrams in the second row in fig. 6. The measurement voltage is explained with reference to FIG. 2

And binary answer signalA change in (c).

In the event that both switching devices 12a and 12B and relay coil 11 are faultless, at the beginning of the test sequence switching device 12a is in its closed state, while switching device 12B is switched off due to the missing test signal P _ B. Therefore, a high voltage level V + is present on the branch 14, which leads to the conduction of the further switching device 24 and a binary response signalThus remaining high. The then closed switching device 12B will measure the voltage on the branch 14 when the test signal P _ B is output

Bringing a low voltage level V-because here the lower resistor 22b of the voltage divider 22 is connected across. Accordingly, the voltage is measured

And the generated binary answer signal

Both of which fall off abruptly. The measurement voltage is held at a low voltage level V and the binary response signal is output as long as the test signal P _ B is output

Remains at a low level. At the end of the check signal P _ BThe second switching device 12b is then switched off again. An overvoltage is induced in the relay coil 11 by the sudden interruption of the current and the magnetic field thus weakened, which overvoltage is slowly weakened by the current flowing through the resistor 25a and the diode 25 b. Correspondingly, the measurement voltage tapped off at the branch 14

First rising above the high voltage level V + and then gradually falling back again to the high voltage level V +. Before the current drops below the value of the holding current and the magnetic field strength is thus no longer sufficient to hold the relay contacts in their active position, the test signal P _ B must be switched on again in order to close the current path 10 again.

The voltage thus measured is derived from the voltage shown in FIG. 6Generating a binary answer signalThe response signal is due to the measuring voltage then rising after the end of the output of the test signal P _ B

And then jumps to its high level.

The change in the binary answer signal BS is transmitted to the monitoring means 16. As in the currentless state of the relay coil, the check for a correct change of the binary response signal can be carried out continuously or discretely. In fig. 6, two characteristic times t are selected for the discrete investigation₃And t₄At these moments the monitoring means 16 check for a change in the binary answer signal. In response to binary answer signals

And therefore a low level must be recognized at time t3 and a high level must be recognized at time t 4.

The following explains possible recognizable fault situations, namely a permanent short-circuited or permanent shut-off switching device 12b, a permanent shut-off switching device 12a or a wire break in the relay coil 11.

Since the switching device 12a is inherently kept in its closed state continuously by the output of the continuous test signal P _ a, the state of the first switching device 12a that is continuously short-circuited due to a fault cannot be detected by the test sequence if a current flows in the relay coil 11. However, the non-identifiability of the fault, since it does not lead to a fault of the electromagnetic relay in the first place (the first switching device 12a should have a permanent short circuit), is not a disadvantage of the test procedure. Such a fault can be easily identified in the test in the currentless state of the relay coil, which has already been described above.

The fault condition F5 in which the second switching device 12b is in the continuously blocking state is addressed first. In this case, the branch 14 is continuously held at the high voltage level V + by the desired short-circuited switching device 12 a. Since the output of the test signal P _ B has no influence on the switching state of the defective, permanently switched-off second switching device 12B, due to this second switching device 12B, the measurement voltage on the branch 14 is not affected

Remains at the high voltage level V + independent of the state of the verify signal P _ B. The binary answer signal BS thus produced^F5Remains at a high level so that the monitoring means 16 determine a binary answer signal BS^F5Deviation of the variation from the expected variation. At time t₃And t₄In the case of discrete investigation, the monitoring device 16 is at time t₃Determining a binary answer signal BS not at a low level but at a high level^F5And a fault signal may be generated.

The fault condition F6, in which the second switching device 12b is continuously short-circuited, is then to be dealt with. In this case, the measured voltage at branch 14

The measurement voltage is obtained by the switching device 12b, which is continuously short-circuited, being continuously at a low voltage level V

As shown in fig. 6. Where the voltage is measured

At a low voltage level V-independent of the test signal P _ B, thereby generating a binary response signal BS^F6And also continuously remains at a low level. The monitoring device 16 can therefore determine deviations from the expected change both continuously and discretely monitoring the change in the binary response signal; in the case of a discrete investigation, the monitoring device 16 is at time t₄Identification of binary answer signals BS^F6Rather than the expected high level, so that a fault signal can be output.

Finally, it is to be considered that the relay coil 11 has a fault condition F7 in which the line is broken or the first switching device 12a is continuously switched off. In this case, the measured voltage at branch 14

First, it starts at the intermediate voltage level set by the voltage divider 22, since the second switching means 12b also blocks the current. So that the binary answer signal BS^F7Starting at a high level. After the test signal P _ B has been switched on and the second switching device 12B has been closed as a result, the measurement voltage is present at the branch 14

Is brought to a low voltage level V-. This also results in a binary answer signal BS^F7Down to a low level. As long as the test signal P _ B keeps the second switching device 12B in the closed state, the voltage is measured

Kept at a low voltageThe level V-. After the end of the test signal P _ B, the damping capacitor 27B (in the case of a wire break in the relay coil 11) or both damping capacitors (in the case of a continuously closed first switching device 12a) are charged again to the intermediate voltage level via the upper resistor 22a of the voltage divider 22.

However, this occurs slowly, so that the binary answer signal BS^F7First at a low level. Whereby the monitoring means 16 recognize the binary answer signal BS^F7Deviation from expected variation. In the case of discrete investigation, the monitoring device 16 is at time t₄A low level of the binary answer signal is identified instead of the expected high level and a fault signal can be output.

Finally, fig. 7 shows the time t₃And t₄The binary response signal is monitored discretely, and the flow of the test procedure is carried out when a current flows in the relay coil 11. After the start of the test process ("test start"), the test signal P _ B is switched on in a first step 71. After waiting a short duration in step 72, a check is made in step 73 as to whether the binary answer signal BS has a low level ("0").

The length of the time duration required in step 72 is determined in such a way 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 correctly detected.

If at step 73 at time t₃If a deviation of the binary response signal BS from the expected low level is determined, a malfunction alarm is output. If, however, in step 73 the binary answer signal BS corresponds to the expected change, in step 74 after the lapse of a time duration sufficient for generating the required holding current, the test signal P _ B is switched off again in step 75 and a short time duration is waited again in step 76, the length of which time duration is determined in such a way that a reaction of the binary answer signal can be detected. In step 77 it is checked whether the binary answer signal BS is at the expected high level. If not, the flow is again outputAnd (4) failure occurs. However, if the binary answer signal is at the expected high level, the test procedure is successfully ended and the measurement procedure can be restarted after a predetermined duration has elapsed.

By means of the information exchange permitted between the control device 13 and the monitoring device 16, it is possible for the monitoring device 16 to include in its test the expected change in the binary response signal that is adapted to the respective setpoint state of the relay coil 11 (either no current flow or current flow).

Finally, it is also pointed out that, in the case of discrete testing at the respective measurement times of the two signatures, it is not always possible to precisely distinguish the type of fault occurring, since a plurality of fault types usually exhibit deviations at the time of the signature which correspond to the expected change in the binary response signal. However, it is often not necessary to accurately distinguish between the types of faults, as it is only of interest to the operator of the electrical equipment in which the electromagnetic relay is installed whether the relay control is normal or faulty. If a possible fault occurs, the operator opens the corresponding switch group with the relay control and the electromagnetic relay, regardless of the kind of fault, to ensure the correct operation of the electrical apparatus.

Nevertheless, if an exact fault differentiation is desired, either the monitoring of the binary response signal must be carried out continuously by means of the monitoring device or the times at which the number of times must be increased by further features are measured, since in this way further significant deviations of the binary response signal can be accounted for. In this case, the monitoring device also outputs the type of fault together with its fault alarm.

However, in the case of the described discrete investigation with only two measurement instants, it can be considered that the selection of the possible fault classes is at least limited accordingly. For example, in the case of a test in the on state of the relay coil 11, a specific fault alarm can be output in the case of a defined deviation of the test level in accordance with step 77 (see fig. 7), which indicates that either the second switching device 12b is continuously short-circuited or the first switching device 12a is continuously closed or the line is disconnected in the relay coil 11. When the level of the binary answer signal is checked in step 73 according to fig. 7, it is possible to limit to the second switching means 12b, which are continuously switched off. Such a malfunction warning is helpful, for example, in the case of repairing a malfunctioning relay assembly or in the case of locating the cause of a malfunction of the system.

Claims

1. A switching device for controlling an electromagnetic relay having a relay coil (11) and relay contacts, wherein,

-arranging two switching devices (12a, 12b) in the 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 is

-a control device (13) is provided, which is configured to close the two switching devices (12a, 12b) to generate a current through the relay coil (11) and to open the two switching devices (12a, 12b) to interrupt the current through the relay coil (11);

it is characterized in that the preparation method is characterized in that,

-the control device (13) is designed to send test signals (P _ a, P _ B) to the first switching device (12a) and the second switching device (12B), wherein the test signals (P _ a, P _ B) are implemented such that they do not influence the momentary state of the relay contacts;

-a measurement voltage (U) tapped between a connection of the relay coil (11) and one of the two switching devices (12a, 12b)_mess) Is applied to an input of a conversion device (15), wherein the conversion device (15) is designed to measure a voltage (U)_mess) -a reply signal (BS) converted to binary; and,

-monitoring means (16) are connected to the output of the switching means, which monitoring means analyze the change of the binary answer signal (BS) by the control means (13) during the transmission of the check signals (P _ a, P _ B) and indicate a fault in the relay coil (11) or in one of the two switching means (12a, 12B) if the binary answer signal (BS) deviates from the expected change.

2. The switchgear as claimed in claim 1,

-said two switching means (12a, 12b) are semiconductor switches.

3. The switchgear as claimed in claim 1 or 2,

-providing connections of a damping capacitor (27a, 27b) in the current path (10) of the relay coil (11) between the relay coil (11) and the connections of one switching device (12a or 12b), respectively.

4. The switchgear as claimed in claim 1,

-the switching device (15) has a coil parallel to the relay(11) Is provided with a voltage divider (22) whose voltage divider tap is applied to the measurement voltage (U)_mess) On the other hand, to the control input of a further switching device (24) in order to obtain a binary response signal (BS).

5. The apparatus of claim 4,

-the further switching device (24) is a semiconductor switch.

6. A method for controlling an electromagnetic relay having a relay coil (11) and relay contacts, in which method two switching devices (12a, 12b) are closed to generate a current through the relay coil (11) and the two switching devices (12a, 12b) are opened to break the current through the relay coil (11), wherein the two switching devices (12a, 12b) are arranged in a current path with the relay coil (11) 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);

it is characterized in that the preparation method is characterized in that,

-the control device (13) outputs to both switching devices (12a, 12B) a check signal (P _ a, P _ B) that does not affect the instantaneous state of the relay contacts;

-measuring a measuring voltage (U) between the relay coil (11) and the connection of one of the switching devices (12a, 12b)_mess)；

-the measurement voltage (U)_mess) Is converted into a binary answer signal (BS); and is

-indicating a fault in the relay coil (11) or in one of the two switching devices (12a, 12b) if the change in the binary answer signal (BS) deviates from the expected change.

7. The method of claim 6,

-outputting time-shifted test signals (P _ a, P _ B) to the two switching devices (12a, 12B) in the current-free state in the relay coil (11), which test signals are shorter than the response time of the relay.

8. The method of claim 7,

-measuring a measuring voltage (U) between a second connection of the relay coil (11) and a second switching device (12b)_mess) In the case of (2), the check signals (P _ a, P _ B) are output in the following order:

a) outputting a second check signal (P _ B) to a second switching device (12B);

b) not outputting the check signal during the signal pause period;

c) the first check signal (P _ A) is output to the first switching device (12 a).

9. The method of claim 7,

-a measuring voltage (U) is tapped between a first connection of the relay coil (11) and the first switching device (12a)_mess) In the case of (2), the check signals (P _ a, P _ B) are output in the following order:

a) outputting a first check signal (P _ A) to a first switching device (12 a);

b) not outputting the check signal during the signal pause period;

c) the second check signal (P _ B) is output to the second switching device (12B).

10. The method according to any of the preceding claims,

-continuously controlling the first switching device (12a) in a current-flowing state of the relay coil (11), while controlling the second switching device (12B) by means of a pulsating second test signal (P _ B).

11. The method of claim 6,

-comparing the binary answer signal (BS) with the expected change at least two characteristic instants (t1, t2), wherein at least one change in the state of at least one check signal (P _ a, P _ B) occurs between the characteristic instants (t1, t2) in order to determine whether a fault occurs in the relay coil (11) or one of the switching devices (12a, 12B).

12. The method of claim 6,

-repeating the method at regular time intervals.

13. The method of claim 6,

depending on the state of the relay contacts, different test signals (P _ A, P _ B) are output by the control device (13).

14. The apparatus of claim 1,

-said two switching means (12a, 12b) are transistors.

15. The switchgear as claimed in claim 4,

-the further switching device (24) is a MOSFET.