SWITCH MONITORING DEVICE

Description

[0001] The present disclosure relates to a switching monitoring device for monitoring a switching operation of a relay switching contact.

[0002] In electrical automation, actuators can each be switched with a relay. It may be necessary to detect the actual switching of a relay switching contact. Such monitored feedback via the relay switching is usually implemented using additional auxiliary contacts. Alternatively, contact positive guidance can be implemented to prevent incorrect relay switching. With contact positive guidance, the switching of further relay switching contacts and / or the connection of the welded buttons to another button can be prevented in the event of a faulty relay switching contact, which, for example, has defective, particularly welded, buttons. Forced contact guidance and / or feedback via auxiliary contacts can disadvantageously result in increased production costs during the manufacture of a relay.

[0003] The document DE 10 2009 006970 A1 discloses a test circuit for functional testing of a component, which has a transformer, a feed circuit for generating an alternating voltage with a definable frequency, and a measuring circuit for determining the impedance of the test circuit and the component at the definable frequency.

[0004] US 2007 / 115604 A1 discloses a system for monitoring an electrical relay. The system comprises an electrical relay; a resistor permanently connected in parallel with the relay; and a controllable electrical load device.

[0005] Document DE 10 2014 016218 A1 discloses a system for monitoring a relay contact. The system comprises an emitter configured to emit a signal and a receiver configured to detect a signal emitted by the emitter.

[0006] The publication DE 20 2017 002030 U1 discloses a circuit for testing the function of an electrical relay, which detects and signals mechanical defects of the relay.

[0007] The document WO 03 / 030198 A1 discloses a safety switching device for safely switching off an electrical machine.

[0008] The document EP 2 662 697 A1 discloses a measuring device for checking an electrical circuit breaker.

[0009] The document DE 10 2013 106487 A1 describes a monitoring circuit for detecting a switching state of an electrical switching contact.

[0010] It is the object of the present disclosure to provide a more efficient switching monitoring device which provides information about the switching state of a relay switching contact, in particular as a function of the relay control.

[0011] This object is achieved by the features of the independent claim. Advantageous embodiments are the subject of the dependent claims, the description, and the accompanying figures.

[0012] The present disclosure is based on the finding that the above object can be achieved by a switching monitoring device which is designed to apply a switching monitoring signal, in particular in the form of a high-frequency auxiliary power, to the relay switching contact by means of a signal generator and a transformer connected downstream of the signal generator. The switching monitoring signal is generated by the signal generator and coupled into the load circuit of the relay by the transformer. A change in the impedance of the load circuit, in particular due to switching of the relay switching contact, is fed back to the signal generator via the transformer and generates a signal change between the signal generator and the transformer, which can be used to detect switching of the relay switching contact.

[0013] According to a first aspect, the disclosure relates to a switching monitoring device for monitoring a switching operation of a relay switching contact of a relay. The switching monitoring device comprises a controller configured to generate an excitation signal and a control terminal configured to apply a control signal for switching the relay switching contact to the relay switching contact.

[0014] The switching monitoring device further comprises an impedance circuit with a signal input and a signal output, wherein the controller is configured to apply the excitation signal to the signal input. The impedance circuit is configured to convert the excitation signal into a switching monitoring signal and to output the switching monitoring signal at the signal output for actuating the relay switching contact.

[0015] The controller is further designed to monitor a change in a signal applied to the impedance circuit and, if the change in the signal occurs, to detect a switching operation of the relay switching contact.

[0016] In one embodiment, the signal comprises the excitation signal and / or the switching monitoring signal.

[0017] The controller is configured to monitor a change in the excitation signal applied to the impedance circuit and, upon the presence of the change in the excitation signal, to detect a switching operation of the relay switching contact. In particular, the controller can be configured to detect a change in the excitation signal instead of detecting the change in the switching monitoring signal. In particular, in addition to the impedance circuit, the controller can have a further signal monitoring circuit for detecting a change in the switching monitoring signal. This signal monitoring circuit can be configured to detect a change in the switching monitoring signal by means of capacitive or inductive coupling.

[0018] By monitoring the relay switching contact using the switching monitoring device, switching information relating to the transition of the relay switching contact between a first switching state, in which the relay switching contact is electrically non-conductive, and a second switching state, in which the relay switching contact is electrically conductive, can be generated when the relay is supplied with the control signal. This ensures that the relay switches with the control signal and, accordingly, that there is no fault in the relay switching contact and / or a magnetic system of the relay. Accordingly, if the control signal is present at the relay and the relay switching contact does not switch, a malfunction of the relay can be detected. Furthermore, switching off of the relay when the switching signal drops can also be monitored.

[0019] The switching monitoring device offers the advantage of enabling clear detection of the switching state of the relay switching contact from a functional safety perspective, particularly according to the IEC 61508 standard. Accordingly, increased diagnostic coverage can be achieved.

[0020] In one embodiment, the relay is provided to transmit signals in a first frequency range and the switching monitoring signal is in a second frequency range, wherein the second frequency range has higher frequencies than the first frequency range, and wherein the impedance circuit has a higher impedance in the first frequency range than in the second frequency range.

[0021] The impedance circuit can form a frequency filter, in particular a bandpass filter, which has a lower impedance for the switching monitoring signal and / or the excitation signal than for electrical signals with other frequencies. Accordingly, coupling of electrical signals from a voltage source and / or another signal source with a corresponding power transmission can be prevented and / or attenuated. For example, the first frequency range can comprise frequencies from 0 Hz to 100 Hz and / or the second frequency range can comprise frequencies above 10 kHz, in particular the frequency range from 100 kHz to 500 kHz. With the higher impedance in the first frequency range, in particular, an output-side current flow can be reduced. Accordingly, by coupling the signal input to the signal output in the first frequency range, an input-side current flow can be reduced.

[0022] The impedance circuit can, in particular, comprise a two-port circuit formed by a 2x2 impedance matrix. The impedance at the signal output can be higher for low frequencies, for example, in the frequency range from 10 Hz to 100 Hz, in particular 50 Hz, than for high frequencies, for example, in the frequency range from 100 kHz to 1 MHz, in particular 500 kHz. For example, the impedance can be 13 MOhm at a frequency of 50 Hz and 3 kOhm at a frequency of 500 kHz. Accordingly, a frequency-dependent impedance difference of three to four orders of magnitude can be achieved between the first frequency range and the second frequency range.

[0023] In one embodiment, the controller is configured to generate the excitation signal in the second frequency range. This provides the advantage that the impedance circuit can efficiently convert the excitation signal into the switching monitoring signal due to the lower impedance in the second frequency range.

[0024] In one embodiment, the controller comprises a measuring circuit for detecting the change in the excitation signal. The measuring circuit can be configured, in particular, to detect an amplitude change in the excitation signal, for example, a voltage amplitude change and / or a current amplitude change. Furthermore, the measuring circuit can be configured to detect a frequency deviation of the frequency of the excitation signal. Furthermore, the measuring circuit can comprise an analog-to-digital converter and / or a measurement signal amplifier to further process the measurement signal, in particular a current and / or voltage change in the excitation signal.

[0025] The controller has a signal generator for generating the excitation signal. The signal generator can be configured, in particular, to generate the excitation signal in the form of a periodic voltage signal. For example, the excitation signal can have a rectangular, sawtooth, or sinusoidal signal shape. The frequency of the excitation signal can be adjusted to a predetermined value by means of the signal generator. Furthermore, the signal generator can be configured to generate the excitation signal with a fixed frequency value.

[0026] In one embodiment, the measuring circuit comprises a current sensor which is connected between the signal generator and the impedance circuit, wherein the current sensor is designed to detect a current flow between the signal generator and the impedance circuit and to provide it to the controller as a current measurement value, and wherein the controller is designed to detect a change in the current flow between the signal generator and the impedance circuit based on the current measurement value.

[0027] The current sensor can be formed by a resistor, in particular an ohmic resistor, at which a current flow between the signal generator and the impedance circuit can be tapped in the form of a measuring voltage. The controller can further comprise a voltmeter configured to detect the measuring voltage.

[0028] Furthermore, the controller may comprise a voltage sensor configured to detect a change in a voltage amplitude of the excitation signal in order to detect switching of the relay switching contact.

[0029] In one embodiment, the impedance circuit is designed to galvanically isolate the relay switching contact from the signal generator and / or the controller. The relay switching contact can be supplied with electrical power, whereby coupling of this electrical power into the controller and / or the signal generator can be prevented by means of the galvanic isolation in the impedance circuit. This electrical power can, in particular, be greater than the power supplied by the signal generator to the impedance circuit.

[0030] The impedance circuit comprises a transformer having a primary coil and a secondary coil, wherein the secondary coil is connected in parallel to the relay switching contact, and wherein the primary coil is connected to the signal generator.

[0031] The transformer can be configured, in particular, to convert the excitation signal into the switching monitoring signal, wherein a current amplitude and / or a voltage amplitude of the switching monitoring signal are proportional to a current amplitude and / or a voltage amplitude of the excitation signal depending on the winding ratio of the primary-side coil to the secondary-side coil. The primary-side coil and the secondary-side coil can be electromagnetically coupled, so that changes in the switching monitoring signal can affect the excitation signal on the input side by means of the transformer.

[0032] If the relay switching contact is in the first switching state, a low-impedance connection for the switching monitoring signal may not be available, so that a current with a lower current intensity than in the second switching state can flow through the secondary-side coil.

[0033] The capacitor arranged in parallel with the relay switching contact can form a resonant circuit with a predetermined resonant frequency with the secondary-side coil. This resonant circuit can have lower attenuation with the relay switching contact in the second switching state than with the relay switching contact in the first switching state. Accordingly, when the resonant circuit is excited by the signal generator, an oscillation amplitude of the resonant circuit with the relay switching contact in the second switching state can be higher than an oscillation amplitude of the resonant circuit with the relay switching contact in the first switching state. The controller can be designed to detect this change in the amplitude of the oscillation by means of a resistor arranged between the signal generator and the signal input.

[0034] In one embodiment, an additional electromagnetic coil can be arranged on the primary-side coil of the transformer, which is designed to detect a change in the excitation signal when the switching monitoring signal changes due to switching of the relay switching contact. The controller can be designed to evaluate a signal induced in the additional electromagnetic coil in order to detect switching of the relay switching contact. The additional electromagnetic coil can be arranged next to the primary-side coil on a ferromagnetic core of the transformer. In one embodiment, the additional electromagnetic coil can at least partially enclose the primary-side coil, in particular be wound over the primary-side coil.

[0035] The impedance circuit comprises a capacitor arranged in series with the secondary-side coil, wherein the capacitor is designed to form a reactance for alternating voltage signals applied to the relay switching contact.

[0036] The impedance circuit can apply a switching monitoring signal, in particular a periodic one, to the relay switching contact. In the first switching state, an impedance at the signal output can be determined by the capacitor. In the second switching state, the impedance at the signal output can be lower than the impedance at the signal output when the relay switching contact is in the first switching state. With a lower impedance at the signal output, a current flowing through the signal output of the impedance circuit can be greater than with a higher impedance at the signal output. The impedance circuit can be configured to couple a corresponding change in current to the signal input, so that a current flowing through the signal input increases with a reduced output-side impedance.

[0037] Furthermore, when the relay switching contact is switched, a voltage amplitude of the switching monitoring signal can change, whereby a current and / or voltage amplitude of the excitation signal can change with the change in the voltage amplitude of the switching monitoring signal.

[0038] The capacitor can also form a reactance for AC voltage signals generated by a voltage source and applied to the relay switching contact. Furthermore, the capacitor can be configured to reduce power loss at the signal output and / or leakage currents that can flow through the signal output when the relay switching contact is in the first switching state.

[0039] The capacitor can be designed to withstand an AC voltage and / or a DC voltage of 230 V including expected transients without damage.

[0040] In one embodiment, the capacitor can be formed by a plate capacitor in the form of conductor tracks on a printed circuit board. The properties of the capacitor can be determined by the printed circuit board material and / or the printed circuit board thickness, so that a defined dielectric strength can be achieved by a distance between two conductor track sections and / or conductor surfaces. The printed circuit board material can, in particular, be FR4, which is formed from a glass fiber fabric, in particular with a di / tetra-epoxy matrix.

[0041] In one embodiment, the signal input is bipolar with a first input terminal and a second input terminal and the signal output is bipolar with a first output terminal and a second output terminal, and a first capacitor is arranged between the first output terminal and the first input terminal and a second capacitor is arranged between the second output terminal and the second input terminal in order to capacitively couple the switching monitoring signal to the relay switching contact.

[0042] In one embodiment, the impedance circuit has an inductance connected downstream of the first capacitor, wherein the inductance forms an oscillating system with the first capacitor between the first output terminal and the first input terminal.

[0043] In one embodiment, the switching monitoring device comprises a first decoupling capacitor, a second decoupling capacitor, and a signal monitoring circuit. The first decoupling capacitor is connectable to the first output terminal and the second decoupling capacitor is connectable to the second output terminal. The decoupling capacitors are connected to the signal monitoring circuit and are configured to convert the switching monitoring signal into a test signal and provide the test signal to the signal monitoring circuit. The signal monitoring circuit is configured to monitor a change in the test signal and, if the change in the test signal is present, to detect a switching operation of the relay switching contact.

[0044] Furthermore, the first decoupling capacitor, the second decoupling capacitor, and / or the signal monitoring circuit can be integrated into the controller. In one embodiment, the impedance circuit can include the decoupling capacitors.

[0045] In one embodiment, the controller is connectable to the control terminal and is designed to generate a control signal for switching the relay switching contact and / or to apply the control signal to the control terminal.

[0046] The inductance may in particular be an electromagnetic coil having an electrical inductance matched to the capacitance of the upstream capacitor such that the combined impedance of the electromagnetic coil and the capacitor is minimal at a resonant frequency.

[0047] The signal generator can, for example, be designed to generate the excitation signal at the resonance frequency.

[0048] In one embodiment, the impedance circuit has a further inductance which is connected downstream of the second output terminal, wherein the further inductance forms a further oscillatable system with the second capacitor between the second output terminal and the second input terminal.

[0049] In one embodiment, the impedance circuit is configured to apply the switching monitoring signal to the relay switching contact in the form of a high-frequency auxiliary energy, which in particular has a frequency in the range from 10 kHz to 1 MHz. Preferably, the signal generator generates the excitation signal with a frequency of 100 kHz to 500 kHz, which can in particular be a rectangular clock signal. The frequency of the excitation signal can be fixed and / or predetermined by the controller. The impedance circuit can be configured to convert the excitation signal with a coupling frequency into the switching monitoring signal with the coupling frequency.

[0050] In one embodiment, the controller comprises a switching controller which is designed to generate the control signal for switching the relay switching contact and to apply the control signal to a magnet system of the relay in order to switch the relay switching contact.

[0051] The controller can further be configured to supply the signal generator with electrical energy. Control of the relay can be coupled with the generation of the excitation signal by the signal generator, so that, for example, the excitation signal can be generated simultaneously with the control of the relay and the switching monitoring signal can be applied to the relay switching contact.

[0052] In one embodiment, the controller is configured to apply the control signal to the signal generator, and the signal generator is configured to generate the excitation signal using the switching signal. This provides the advantage that the signal generator can be powered by the same electrical signal that is also used to control the relay. Accordingly, a separate power supply for the signal generator and / or the controller is unnecessary.

[0053] In one embodiment, the controller may be configured to detect a current intensity of the switching signal and / or a current intensity of the current flowing through a relay coil of the magnet system, in particular by means of a shunt resistor.

[0054] The relay switching contact can have a typical switch-on delay of 1 ms to 50 ms. With simultaneous activation of the relay and the signal generator with the control signal, the switching monitoring signal is applied to the relay switching contact before the relay switching contact switches between the first switching state and the second switching state according to the control signal. The signal chain from the signal generator via the impedance circuit to the relay switching contact can accordingly have a shorter signal propagation time than the relay's switch-on delay.

[0055] Furthermore, the signal generator can be designed to continue generating the excitation signal after a drop in the control signal for a time interval which is in particular greater than a typical switch-off delay of the relay in order to detect a change of the relay switching contact from the second switching state to the first switching state.

[0056] The switching monitoring device can be configured to apply a relay control signal applied to the controller, the signal generator, the impedance circuit, and / or the magnetic system of the relay to control the relay in order to supply the respective component with electrical energy. Accordingly, a separate energy source and / or power supply for the signal generator, the impedance circuit, and / or the controller can be omitted, as these can be supplied with electrical energy directly via the relay control signal.

[0057] In one embodiment, the signal generator is designed to generate the excitation signal in the form of a periodic clock signal, and the controller is designed to detect, on the basis of the constant period of the excitation signal, a time interval between the generation of the excitation signal and a change in the excitation signal when the impedance at the signal output changes in order to detect a switching time delay of the relay switching contact.

[0058] The controller can be configured, in particular, to detect a number of periods and / or clock cycles of the excitation signal and, in accordance with the fixed frequency of the excitation signal, to detect the time interval between the generation of the excitation signal and the switching of the relay switching contact. Upon switching of the relay switching contact, an output-side impedance can change, causing a change in the excitation signal. The excitation signal change can be detected by the controller using a sensor to determine the switching of the relay switching contact and the end of the time interval between relay activation and the switching of the relay switching contact.

[0059] The controller can further be configured to actuate the signal generator before the relay switching contact switches. Accordingly, the switching monitoring signal can be present at the relay switching contact during a switch-on operation of the relay switching contact and / or during a switch-off operation of the relay switching contact. Advantageously, the switching monitoring signal can be switched off while the relay switching contact is in the first switching state or the second switching state. In particular, the switching monitoring signal is only present during a switching time in which the relay switching contact alternates between the first switching state and the second switching state.

[0060] In one embodiment, the controller has a control output, and the controller is configured to provide a status signal at the control output, which status signal is active after the relay switching contact is switched on and is inactive after the relay switching contact is switched off.

[0061] This provides the advantage that status signals of a plurality of switching monitoring devices can be aggregated at a central location in order to be able to monitor the switching of a plurality of relays centrally and, in particular, remotely from the installation location of the respective relay of the plurality of relays.

[0062] The control output can also be an error reporting contact and / or an image of the relay switching contact. Furthermore, the control output can comprise an analog and / or digital interface configured to transmit information about the relay and the switching state of the relay.

[0063] In one embodiment, the switching monitoring device comprises a first damping element and the signal output has a first output terminal, downstream of which the first damping element is connected in order to dampen high-frequency signals which are applied to the relay switching contact and / or an electrical load and / or voltage source coupled to the relay switching contact by means of the impedance circuit.

[0064] This provides the advantage that the properties of the switching monitoring device with respect to electromagnetic compatibility can be improved. The damping elements can, in particular, be designed to attenuate a signal amplitude of the switching monitoring signal in order to reduce electromagnetic radiation of the switching monitoring signal into the environment of the switching monitoring device and / or the relay.

[0065] In one embodiment, the switching monitoring device comprises a second damping element and the signal output has a second output terminal, downstream of which the second damping element is connected in order to dampen high-frequency signals which are applied to the relay switching contact and / or to an electrical load and / or voltage source coupled to the relay switching contact by means of the impedance circuit.

[0066] In one embodiment, the first damping element and / or the second damping element each have an inductance, and wherein the respective inductance forms a minimum impedance for the switching monitoring signal in order to prevent a bypass of the switching monitoring signal via the electrical load and / or the voltage source.

[0067] This provides the advantage that switching of the relay switching contact between the first switching state and the second switching state can be reliably detected even with a low-impedance current source and / or a low-impedance electrical load. If a current path through the current source and the electrical load has a lower impedance than, for example, the capacitor connected in parallel with the relay switching contact, the switching monitoring signal can flow via the current source and / or the electrical load, so that switching of the relay switching contact does not affect the impedance registered at the signal output, or only to a reduced extent.

[0068] The inductors are advantageously designed with low resistance to minimize power losses when a current flows through them. In one embodiment, the inductors are designed to be traversed by a total load current that flows through the relay switching contact and is determined by the power of a voltage source and the impedance of a load connected to the relay switching contact. The inductors can be arranged together on a coil core, in particular a magnetic core, and in particular form a current-compensated choke. The inductors can also be interleaved with opposite winding directions to form the highest possible differential-mode impedance for the switching monitoring signal.

[0069] Further embodiments are explained with reference to the accompanying figures. They show: Fig. 1 shows a switching monitoring device in one embodiment; Fig. 2 shows a switching monitoring device in one embodiment; Fig. 3 shows a switching monitoring device in one embodiment; Fig. 4 shows signal shapes when a relay is controlled by the switching monitoring device in one embodiment; Fig. 5 shows an event sequence when a relay is switched on by the switching monitoring device in one embodiment; Fig. 6 shows an event sequence when a relay is switched off by the switching monitoring device in one embodiment; and Fig. 7 shows a schematic representation of a switching monitoring device for monitoring a switching operation of a relay switching contact of a relay.

[0070] Fig. 1shows a schematic representation of a switching monitoring device 100 for monitoring a switching operation of a relay switching contact 101 of a relay 103. The switching monitoring device 100 has a controller 105 which is designed to generate a control signal for switching the relay switching contact 101 and an excitation signal.

[0071] Furthermore, the switching monitoring device 100 comprises an impedance circuit 107 with a signal input 109 and a signal output 111. The controller 105 is configured to apply the excitation signal to the signal input 109. The impedance circuit 107 is configured to convert the excitation signal into a switching monitoring signal and to output the switching monitoring signal at the signal output 111 for actuating the relay switching contact 101.

[0072] Furthermore, the controller 105 is designed to monitor a change in a signal applied to the impedance circuit 107, in particular the excitation signal and / or the switching monitoring signal, and to detect a switching operation of the relay switching contact 101 when the signal change occurs.

[0073] Relay 103 is configured to transmit signals in a first frequency range, and the switching monitoring signal is configured to transmit signals in a second frequency range, wherein the second frequency range has higher frequencies than the first frequency range. Furthermore, impedance circuit 107 has a higher impedance in the first frequency range than in the second frequency range.

[0074] Furthermore, the controller 105 includes a signal generator 113 configured to generate the excitation signal in the second frequency range. The impedance circuit 107 is configured to galvanically isolate the relay switch contact 101 from the signal generator 113 and / or the controller 105.

[0075] Furthermore, the controller 105 comprises a measuring circuit 115 for detecting the change in the excitation signal. The measuring circuit 115 has a current sensor 121, which is connected between the signal generator 113 and the impedance circuit 107. The current sensor 121 is configured to detect a current flow between the signal generator 113 and the impedance circuit 107 and to provide it to the controller 105 as a current measurement value. Furthermore, the controller 105 is configured to detect a change in the current flow between the signal generator 113 and the impedance circuit 107 based on the current measurement value.

[0076] The impedance circuit 107 comprises a transformer 117 with a primary-side coil 119-1 and a secondary-side coil 119-2, wherein the secondary-side coil 119-2 is connected in parallel to the relay switch contact 101, and the primary-side coil 119-1 is connected to the signal generator 113. Furthermore, the impedance circuit 107 comprises a capacitor 123 arranged in series with the secondary-side coil 119-2. The capacitor 123 is configured to form a reactance for AC voltage signals applied to the relay switch contact 101.

[0077] Furthermore, the impedance circuit 107 is designed to apply the switching monitoring signal in the form of a high-frequency auxiliary energy to the relay switching contact 101, which in particular has a frequency in the range from 10 kHz to 1 MHz.

[0078] Furthermore, the controller 105 comprises a switching controller which is designed to generate the control signal for switching the relay switching contact 101 and to apply the control signal to a magnet system 125 of the relay 103 in order to switch the relay switching contact 101.

[0079] In one embodiment, the controller 105 is configured to apply the control signal to the signal generator 113, and the signal generator 113 is configured to generate the excitation signal using the switching signal.

[0080] Furthermore, the signal generator 113 is designed to generate the excitation signal in the form of a periodic clock signal, and the controller 105 is designed to detect, on the basis of the constant period of the excitation signal, a time interval between the generation of the excitation signal and a change in the excitation signal when the impedance at the signal output 111 changes in order to detect a switching time delay of the relay switching contact 101.

[0081] Furthermore, the controller 105 comprises a control output 127 and the controller 105 is designed to provide a status signal at the control output 127, which is active after the relay switching contact 101 is switched on and inactive after the relay switching contact 101 is switched off.

[0082] The controller 105 further comprises a control input 133, via which the controller 105 can be supplied with electrical energy. In particular, the controller 105 can be configured to receive electrical energy in the form of a direct voltage in the range of 3 V to 24 V.

[0083] Fig. 2shows a schematic representation of a switching monitoring device 100 for monitoring a switching operation of a relay switching contact 101 of a relay 103 in one embodiment. The signal input 109 is bipolar with a first input terminal 201-1 and a second input terminal 201-2, and the signal output 111 is bipolar with a first output terminal 203-1 and a second output terminal 203-2. Furthermore, a first capacitor 205-1 is arranged between the first output terminal 203-1 and the first input terminal 201-1, and a second capacitor 205-2 is arranged between the second output terminal 203-2 and the second input terminal 201-2 in order to capacitively couple the switching monitoring signal to the relay switching contact 101.

[0084] Furthermore, the impedance circuit 107 comprises an inductance 207 which is connected downstream of the first capacitor 205-1, wherein the inductance 207 forms an oscillating system with the first capacitor 205-1 between the first output terminal 203-1 and the first input terminal 201-1.

[0085] Fig. 3 shows a schematic representation of a switching monitoring device 100 for monitoring a switching operation of a relay switching contact 101 of a relay 103 according to the Fig. 1 shown embodiment.

[0086] In addition, the switching monitoring device 100 comprises a first damping element 301-1 and a second damping element 301-2. The signal output 111 has a first output terminal 203-1 and a second output terminal 203-2, wherein the first damping element 301-1 is connected downstream of the first output terminal 203-1 and the second damping element 301-2 is connected downstream of the second output terminal 203-2 in order to attenuate high-frequency signals which are applied to the relay switching contact 101 and / or an electrical load 129 and / or voltage source 131 coupled to the relay switching contact 101 by means of the impedance circuit 107.

[0087] The first damping element 301-1 and the second damping element 301-2 each have an inductance 303-1, 303-2, which form a minimum impedance for the switching monitoring signal in order to prevent a bypass of the switching monitoring signal via the electrical load 129 and / or the voltage source 131.

[0088] Fig. 4 shows a schematic representation of signal waveforms 400 when a relay is controlled by the switching monitoring device. At a first time t1, an electromagnetic relay coil of the relay's magnetic system is supplied with a relay control signal. Accordingly, a coil voltage 401 is applied to the electromagnetic relay coil. With the application of coil voltage 401 to the electromagnetic relay coil, a coil current 403 in the electromagnetic relay coil increases.

[0089] Furthermore, starting at time t1, the signal generator of the switching monitoring device generates the excitation signal 405 in the form of a rectangular signal, which in particular has an exclusively positive signal amplitude. The impedance circuit converts the excitation signal 405 into the switching monitoring signal 407, which is applied to the relay switching contact. Starting at time t2, the switching monitoring signal 407 has the signal shape of the excitation signal 405.

[0090] Until time t2, the relay switching contact is in the first switching state and accordingly electrically non-conductive or high-impedance. The total resistance that can be detected at the two-pole signal output of the impedance circuit can be determined by the external circuit consisting of an electrical load and / or a voltage source. Furthermore, in one embodiment, the damping elements, particularly in the form of inductors, can contribute to the total resistance. Depending on the total resistance, a current flow can be detected between the signal generator and the impedance circuit using the current sensor.

[0091] From time t2, the relay switching contact switches from the first switching state to the second switching state, with the time interval between t2 and t3 determining a bounce duration of the relay switching contact. When the relay switching contact switches, the switching monitoring signal 407 breaks down in the form of a voltage at the relay switching contact. The total resistance at the signal output of the impedance circuit changes accordingly, since the electrically conductive relay switching contact with the capacitor arranged parallel to the relay switching contact has a lower impedance compared to the electrically non-conductive relay switching contact. The change in the total resistance can generate a change in a primary-side signal at the signal input or the signal generator, which can be, for example, a changed current amplitude that can be detected by the current sensor.

[0092] The controller is configured to detect the current change at time t2 and, accordingly, to detect switching of the relay switching contact at time t2. The controller can further be configured to switch off the signal generator and, accordingly, the excitation signal 405 at time t5. Alternatively, the controller can be configured to continuously generate the excitation signal 405 in order to continuously apply the switching monitoring signal 407 to the relay switching contact. In particular, the excitation signal 405 can be generated in the time interval Δ2 between time t5 and time t7.

[0093] In one embodiment, the controller is configured to cyclically control the signal generator to generate the excitation signal 405 at recurring intervals and to monitor the switching state of the relay switching contact. Accordingly, the controller can be configured to detect, based on an absolute amplitude value and / or effective amplitude value of an amplitude of the excitation signal 405, whether the relay switching contact is in the first switching state or in the second switching state. Accordingly, a periodic check of the relay switching contact using the switching monitoring device can ensure, for example, that the relay switching contact is electrically conductive.

[0094] When the relay switching contact is switched to the second switching state, the controller generates a status signal 409 at the control output in order to generate feedback about the switching of the relay switching contact.

[0095] Switching off the relay by changing the relay switching contact from the second switching state to the first switching state can be achieved by switching off the relay control signal at time t7. Starting at time t7, the signal generator can be switched on to generate the excitation signal 405 and accordingly apply the switching monitoring signal 407 to the relay switching contact. The signal generator can be switched off at time t10.

[0096] The relay switching contact begins to open at time t8, thus breaking the electrical connection via the relay switching contact. From time t9, the switching contact is fully open and no longer electrically conductive. An arc between the opening contact points of the relay switching contact may be extinguished from time t9.

[0097] A time interval between times t2 and t3, during which the relay contact bounces, and a further time interval between times t8 and t9, during which an arc is formed at the relay contact, can vary for each switching operation. The signal generator remains switched on beyond the respective time interval in order to be able to record the time deviation of the respective time interval and / or the complete switching or switching off process of the relay contact.

[0098] The controller can further be configured to determine a number of bounces and / or a bounce duration based on the signal profile of the excitation signal 405 and the signal profile of the switching monitoring signal 407. Furthermore, the controller can be configured to compare the determined bounce duration and / or the determined number of bounces with a respective limit value.

[0099] The controller can further be configured to detect the coil current 403 and, based on the temporal amplitude curve of the coil current 403 when the switching signal is applied to the electromagnetic relay coil, to determine an armature impact time t6. The armature impact time t6 can be defined by the magnet system having maximally deflected an armature of the relay and, accordingly, a working air gap between a yoke of the relay and the armature having been completely overcome. Furthermore, at the armature impact time t6, a mechanical contact between buttons of the relay switching contact can be subjected to a maximum possible compressive force. The controller can be configured to determine the time t2 from which the relay switching contact becomes electrically conductive and the armature impact time t6.

[0100] Furthermore, the controller can be configured to determine a time interval Δ1 between time t2 and time t6. Using the signal curves of the excitation signal 405, the switching monitoring signal 407, and / or the coil current 403 in the time interval Δ1, the controller can be configured to determine typical relay characteristics. Furthermore, the controller can be configured to determine the typical relay characteristics continuously or at periodic intervals in order to determine wear, a failure probability, and / or a maintenance or replacement time of the relay from a temporal curve of the relay characteristics. The controller can also be configured to detect a switching cycle of the relay.

[0101] Furthermore, the controller can be configured to switch the status signal 409 active from time t4 and correspondingly increase a signal amplitude of the status signal 409. Furthermore, the controller can be configured to switch the status signal 409 inactive from time t8 and correspondingly reduce a signal amplitude of the status signal 409.

[0102] Fig. 5shows an event sequence 500 of a relay being switched on by means of the switching monitoring device in one embodiment. The event sequence 500 begins with the start of the switch-on 501, which is characterized by a relay control signal being present at the control input of the controller. Subsequently, the controller applies the control signal to the relay's magnetic system, thereby controlling the relay 503. Subsequently, the signal generator is switched on to generate the clock signal, designated by Clock On 505. After the relay's switch-on delay has elapsed, the relay switching contact closes and the relay is switched on 507.

[0103] When the relay switching contact closes, the current flow through the relay switching contact and accordingly through the signal output of the impedance circuit changes, resulting in a current change 509 on the input side. By activating the runtime detection 511, a switch-on time of the relay switching contact can be determined and recorded by the controller.

[0104] The controller then activates the feedback signal 513 by activating the status signal 409 at the control output. The relay is thus switched on, and the event sequence 500 ends 515.

[0105] Fig. 6shows an event sequence 600 of a relay deactivation by means of the switching monitoring device in one embodiment. The event sequence 500 begins with the start of the deactivation 601, which is characterized by the fact that a relay control signal is no longer present at the control input of the controller. Accordingly, the control signal is not present at the relay's magnetic system. Subsequently, the signal generator is switched on to generate the clock signal, designated by Clock On 605. After the relay deactivation delay has elapsed, the relay switching contact opens and the relay is switched off 507.

[0106] When the relay switching contact opens, the current flow through the relay switching contact and accordingly through the signal output of the impedance circuit changes, resulting in a current change 609 on the input side. By disabling the runtime determination 611, a switch-off time can be detected by the controller in order to determine a runtime of the relay based on the difference between the switch-on time and the switch-off time.

[0107] The controller then deactivates the feedback signal 613 by deactivating the status signal 409 at the control output. The relay deactivation is thus completed, and the event sequence 600 ends 615.

[0108] Fig. 7shows a schematic representation of a switching monitoring device 100 for monitoring a switching operation of a relay switching contact 101 of a relay 103. The switching monitoring device 100 further comprises two coupling capacitors 701, 703 and a signal monitoring circuit 705. The capacitors 701, 703 are connected on the input side to the signal output 111 and on the output side to the signal monitoring circuit 705. Furthermore, the coupling capacitors 701, 703 are designed to capacitively couple a signal present at the relay switching contact, in particular the switching monitoring signal, to the signal monitoring circuit 705.

[0109] This provides the advantage that the impedance circuit 107 can inductively couple the switching monitoring signal to the relay switching contact 101, and a change in the switching monitoring signal can be capacitively detected by means of the coupling capacitors 701, 703 and provided to the signal monitoring circuit 705. The signal monitoring circuit 705 can be configured to detect a change in the switching monitoring signal and provide the status signal. Furthermore, the coupling capacitors 701, 703 and / or the signal monitoring circuit 705 can be part of the controller 105 and / or integrated therein. List of reference symbols

[0110] 100Switch monitoring device 101Relay switching contact 103Relay 105Control 107Impedance circuit 109Signal input 111Signal output 113Signal generator 115Measuring circuit 117Transformer 119-1Primary coil 119-2Secondary coil 121Current sensor 123Capacitor 125Magnet system 127Control output 129Electrical load 131Voltage source 133Control input 201-1First input terminal 201-2Second input terminal 203-1First output terminal 203-2Second output terminal 205-1First capacitor 205-2Second capacitor 207Inductance 301-1First damping element 301-2Second damping element 303-1Inductance 303-2Inductance 400Signal forms 401Coil voltage 403Coil current 405Excitation signal 407Switching monitoring signal 409Status signal t1Time t2Time t3Time t4Time t5Time t6Time t7Time t8Time t9Time t10Time Δ1Time Interval Δ2Time Interval 500Event sequence 501Start switching on 503Relay control 505Clock on 507Relay has switched on 509Current change 511Runtime determination switching on 513Feedback active 515End switching on 600Event sequence 601Start Switch off 603Relay switch off 605Clock on 607Relay has switched off 609Current change 611Runtime determination Switch off 613Feedback Inactive 615End Switch off 701 Coupling capacitor 703 Coupling capacitor 705 Signal monitoring circuit

Claims

1. Switching monitoring device (100) for monitoring a switching operation of a relay switching contact (101) of a relay (103), the switching monitoring device (100) comprising the following features: a control terminal (102), which is adapted to apply a control signal for switching the relay switching contact (101) to the relay switching contact (101), a controller (105), which is adapted to generate an excitation signal, wherein the controller (105) comprises a signal generator (113) for generating the excitation signal, and an impedance circuit (107) comprising a signal input (109) and a signal output (111), wherein the controller (105) is adapted to apply the excitation signal to the signal input (109), wherein the impedance circuit (107) is adapted to convert the excitation signal into a switching monitoring signal and to output the switching monitoring signal at the signal output (111) for applying it to the relay switching contact (101); wherein the impedance circuit (107) comprises a transformer (117) with a primary-side coil (119-1) and a secondary-side coil (119-2), and wherein the secondary-side coil (119-2) is connected in parallel to the relay switching contact (101), and wherein the primary-side coil (119) is connected to the signal generator (113), characterized in that the impedance circuit (107) comprises a capacitor (123), which is arranged in series with the secondary-side coil (119-2), wherein the controller (105) is further adapted to detect a change in a signal present at the impedance circuit (107) and, if the change in the signal is present, to detect a switching operation of the relay switching contact (101).

2. Switching monitoring device (100) according to claim 1, wherein the signal comprises the excitation signal and / or the switching monitoring signal.

3. Switching monitoring device (100) according to one of the preceding claims, wherein the controller (105) comprises a measuring circuit (115) for detecting the change in the excitation signal.

4. Switching monitoring device (100) according to one of the preceding claims, wherein the measuring circuit (115) comprises a current sensor (121), which is connected between the signal generator (113) and the impedance circuit (107), wherein the current sensor (121) is adapted to detect a current flow between the signal generator (113) and the impedance circuit (107) and to provide it to the controller (105) as a measured current value, and wherein the controller (105) is adapted to detect a change of the current flow between the signal generator (113) and the impedance circuit (107) on the basis of the measured current value.

5. Switching monitoring device (100) according to one of the preceding claims, wherein the impedance circuit (107) is adapted to galvanically separate the relay switching contact (101) from the signal generator (113) and / or the controller (105).

6. Switching monitoring device (100) according to one of the preceding claims, wherein the capacitor (123) is adapted to form a reactance for alternating voltage signals, which are applied to the relay switching contact (101).

7. Switching monitoring device (100) according to one of the preceding claims, wherein the controller (105) is connectable to the control terminal (102) and is adapted to generate a control signal for switching the relay switching contact (101) and / or to apply the control signal to the control terminal (102).

8. Switching monitoring device (100) according to claim 7, wherein the controller (105) comprises a switching controller, which is adapted to generate the control signal for switching the relay switching contact (101) and to apply the control signal to a magnet system (125) of the relay (103) to switch the relay switching contact (101).

9. Switching monitoring device (100) according to claim 7 or 8, wherein the controller (105) is adapted to apply the control signal to the signal generator (113), and wherein the signal generator (113) is adapted to generate the excitation signal using the switching signal.

10. Switching monitoring device (100) according to one of claims 7 to 9, wherein the signal generator (113) is adapted to generate the excitation signal in the form of a periodic clock signal, and wherein the controller (105) is adapted to detect a time interval, based on the constant period of the excitation signal, between the generation of the excitation signal and a change in the excitation signal upon a change of the impedance at the signal output (111), in order to detect a switching time delay of the relay switching contact (101).

11. Switching monitoring device (100) according to one of the preceding claims, wherein the controller (105) comprises a control output (127), and wherein the controller (105) is adapted to provide a status signal at the control output (127), which is active after the relay switching contact (101) is switched on and which is inactive after the relay switching contact (101) is switched off.

12. Switching monitoring device (100) according to one of the preceding claims, comprising a first damping element (301-1), wherein the signal output (111) comprises a first output terminal (203-1), which is upstream of the first damping element (301-1) in order to dampen high-frequency signals, which are applied by means of the impedance circuit (107) to the relay switching contact (101) and / or an electrical load (129) and / or a voltage source (131) coupled to the relay switching contact (101).

13. Switching monitoring device (100) according to one of the preceding claims, comprising a second damping element (301-2), wherein the signal output (111) comprises a second output terminal (203-2), which is upstream of the second damping element (301-2) in order to dampen high-frequency signals, which are applied by means of the impedance circuit (107) to the relay switching contact (101) and / or to an electrical load (129) and / or a voltage source (131) coupled to the relay switching contact (101).