EP4249345A1 - Operation of a field element in a railway engineering system via a four-wire interface - Google Patents

Abstract

A device (20) for operating a field element in a railway system comprises a monitoring device (21) with a monitoring DC voltage source (210) for generating a monitoring voltage (U_sup) and two current detectors (211, 213) for measuring the currents (I₁, I₂) through the third and fourth connection (X3) of the four-wire interface. An evaluation device (215) determines and outputs a monitoring signal (E) based on the currents (I₁, I₂) measured by the first and second current detectors (211, 213). out of. A changeover control (22) controls the field element in order to change it from a first end position to a second end position, and for this purpose comprises a changeover DC voltage source (220) and a changeover target position selector switch (224). Also disclosed are a field element with a nonlinear element for generating an auxiliary voltage and a railway system that includes a device of the type mentioned and a field element.

Description

TECHNICAL FIELD

The present invention relates to a device for operating a field element in a railway system, the device having a four-wire interface to the field element. The invention also relates to a field element that is suitable for operation with such a device and to a railway system that has such a device and a field element.

STATE OF THE ART

Railway technical systems can have a variety of motor-driven field elements such as switches, barriers or gauge changing systems. The field elements are located in an outdoor system, while the components for controlling and monitoring the field elements are located in an indoor system.

For example, in a switch to provide a route, moving parts of the switch are mechanically adjusted between a left and a right end position. In order to switch the switch between the left and right end positions, a switch drive with a drive motor is used. The drive motor is traditionally operated with a three-phase alternating voltage. In the Fig. 1A A switch 11 with a switch drive 12 and push rod 13 is schematically illustrated in its left end position L, in which Fig. 1B in its right end position R. The terms “left” and “right” refer to the position in relation to the direction of travel F in which the switch forms a branch. The switch drive 12 is electrically controlled and monitored by a control and monitoring device in the indoor system that is spatially separate from the switch. The control and monitoring device in turn communicates with a signal box computer.

For several decades, the so-called "four-wire interface" has been a standardized electrical interface between the control and monitoring device in the indoor system and the point drive in the outdoor system. Examples of switch drives that work with the four-wire interface are the Siemens S 700 K, Thales FieldTrac 6341 L700H and Thales FieldTrac 6343 L826H systems.

In the Fig. 2 the traditional interaction of a switch machine 12 with a control unit 20 is illustrated via a four-wire interface. The point drive 12 has a drive motor with three windings L1, L2, L3, the mutual interconnection of which is determined by the position of two limit switches m1 and m2. The switch drive 12 and the control unit 20 each have a four-wire interface X1-X4. These four-wire interfaces are connected to one another via a four-wire cable 30.

The four-wire interface can be operated in two operating modes, namely in monitoring mode or in changeover mode. In order to switch between the two operating modes, the control unit 20 has an operating mode switch 23 in the form of a four-pole isolating relay. The operating mode switch 23 connects the switch drive 12 either to an end position monitoring device 21 or a changeover control 22. In monitoring mode, the end position monitoring device 21 applies a DC voltage to two of the four connections of the four-wire interface and, on the one hand, determines the resulting current through these connections and on the other hand the voltage resulting at the other two connections. The voltage and current measurements can be used to determine whether the switch is in the end position to be monitored. In changeover operation, the changeover control 22 applies a three-phase alternating voltage (typically 3 x 400 VAC) to the windings L1-L3 of the drive motor via the four-wire interface X1-X4.

For a further explanation of the two operating modes, see Figures 3A-3D The positions of the limit switches m1, m2 are illustrated for different states of the switch. In the Fig. 3A the limit switches m1, m2 are in the position they assume in the left end position L of the switch Fig. 3B in the position that they assume in the right end position R of the switch. In the Fig. 3C the limit switches m1, m2 are in the position that they assume when the switch is "cut open", ie in a state in which the switch is between its left and right end position. The switch assumes this state on the one hand during the changeover, and on the other hand in the following situations: when the switch is blocked during the changeover so that it cannot reach its end position, or when the switch has been opened. The position of the Fig. 3D is never taken in the company.

In changeover mode, the drive motor starts from the left end position Fig. 3A or the right end position of 3B initially operated in two phases until the limit switches reach the position of the Fig. 3C assume. The further changeover now takes place in normal three-phase operation. The phase position on the windings L1-L3 determines the direction of rotation of the drive motor. When the desired end position is reached, the changeover control 22 recognizes this and switches the isolating relay 23 to the position for monitoring operation.

The monitoring operation is based on the Figures 4A and 4B explained in more detail. In the Fig. 4A The end position monitoring device 21 monitors whether the switch occupies the left end position. For this purpose, a monitoring DC voltage source 210 is provided in the end position monitoring device 21, which applies a monitoring voltage U _sup of typically 48 ... 60 VDC to the connections X2 and X3. A low-resistance current detector 211, typically a low-resistance relay that switches above a certain current threshold, is arranged in series with the DC voltage source 210 and determines a measure of the current I ₁ caused by the DC voltage source 210 through the connection X3. A high-resistance voltage detector 212, typically a high-resistance relay that switches above a certain voltage threshold, is connected to terminals X1 and X4. The current detector 212 determines a measure of the voltage U ₁ , which is formed at the connections X1 and X4 due to the monitoring voltage U _sup . The windings L1-L3 have low resistance to direct currents (typically 10-15 Q). When the switch occupies the left end position (ie when the limit switches m1 and m2 reach the in Fig. 3A position shown), current flows serially through the low-resistance windings L1-L3, the low-resistance current detector 211 and the high-resistance voltage detector 212. The resulting current I ₁ is limited by the high internal resistance of the voltage detector 212 and is correspondingly small. The resulting voltage U ₁ is correspondingly relatively large. If, on the other hand, the switch assumes the cut state (ie if the limit switches m1 and m2 reach the in Fig. 3C assume the position shown), the current only flows through the low-resistance windings L2 and L3 and the low-resistance current detector 211, but not through the Winding L1 and the voltage detector 212. The resulting current I ₁ is correspondingly high. At the same time, the voltage U ₁ at the voltage detector 212 becomes zero. This allows a clear distinction to be made between the left end position and the cut state. Analogous considerations also apply to monitoring the right end position, which is in the Fig. 4B is illustrated.

In this traditional state of the art, the monitoring of the end positions via the four-wire interface is always carried out via a voltage measurement (high-impedance) and a current measurement (low-impedance). All elements in the outdoor system (windings L1-L3 and limit switches m1 and m2) are low-resistance with respect to direct currents, and the high-resistance voltage detector is arranged in the indoor system.

Similar controls are also used for other types of motorized field elements such as barriers or gauge changing systems.

Traditionally, the control unit 20 is arranged together with the signal box computer in a central signal box building, i.e. the indoor system is centralized in a single location. Between the signal box building and the field elements, cables run in a tree-like arrangement and can be up to several kilometers long. This type of arrangement is referred to below as “traditional signal box architecture”.

More recently, however, developments have been moving towards a decentralized interlocking architecture ("digital decentralized interlockings"). With a decentralized signal box architecture, the control and monitoring devices are located decentrally in control cabinets close to the assigned field elements. The control and monitoring devices are connected to a central interlocking computer via data lines (copper or fiber optic). This makes it possible, in particular, to record more complex diagnostic functions directly on the field elements and to transmit them to the signal box computer via the data line. The corresponding specification is referred to as “NeuPro” at Deutsche Bahn. Corresponding products are provided, for example, by Thales under the product name “Distributed Controller Architecture (DCA)” or by Siemens AG under the product names “SiNet” and “SiGrid”. A decentralized signal box architecture also requires a changed energy supply concept. Thales proposed that the distributed control cabinets be connected via a so-called "PowerBus" with a direct voltage of 400 VDC or 750 VDC to supply.

EP3643579A1 discloses a device for monitoring the operating status of a switch, in which a readout signal is generated in the form of an AC signal. The value of the frequency of this readout signal depends on the determined operating state of the switch. A coupling device couples the readout signal into an electrical line between a switch drive of the switch and a signal box. An evaluation device arranged remotely from the switch couples the readout signal out of the line, carries out a spectral analysis of the extracted readout signal and, depending on a result of the spectral analysis, generates an output signal which represents the operating state of the switch.

PRESENTATION OF THE INVENTION

It is an object of the present invention to develop a device for operating a field element via a four-wire interface in such a way that it is particularly suitable for a decentralized signal box architecture with a DC voltage supply.

This object is achieved by a device according to claim 1 or 5. Further embodiments are specified in the dependent claims.

• eine Überwachungs-Gleichspannungsquelle zur Erzeugung einer Überwachungsspannung zwischen zwei Anschlüssen der Vierdraht-Schnittstelle;
• einen ersten Stromdetektor zur Messung eines Stroms durch einen derjenigen Anschlüsse der Vierdraht-Schnittstelle, an denen die Überwachungsspannung erzeugt wird;
• einen zweiten Stromdetektor zur Messung eines Stroms zwischen denjenigen Anschlüssen der Vierdraht-Schnittstelle, zwischen denen nicht die Überwachungsspannung erzeugt wird; und
• eine Auswerteeinrichtung, die dazu ausgebildet ist, basierend auf den vom ersten und zweiten Stromdetektor gemessenen Strömen ein Überwachungssignal zu ermitteln und das Überwachungssignal auszugeben.

The present invention provides a device (“field element control unit”) for operating a field element in a railway system, with a four-wire interface with a first, second, third and fourth connection. According to a first aspect of the invention, the device has a monitoring device for monitoring an operating state of the field element. The monitoring facility includes:

• a monitoring DC voltage source for generating a monitoring voltage between two terminals of the four-wire interface;
• a first current detector for measuring a current through one of those terminals of the four-wire interface at which the monitoring voltage is generated;
• a second current detector for measuring a current between those terminals of the four-wire interface between which the monitoring voltage is not generated; and
• an evaluation device that is designed to do this, based on the data from the first and second current detector to determine a monitoring signal and to output the monitoring signal.

With this monitoring device, unlike classic monitoring using a four-wire interface, monitoring is carried out using two current measurements instead of one voltage and one current measurement. This enables particularly reliable monitoring. In particular, insulation faults or wire shorts can be detected and localized particularly reliably, as these have a direct effect on the measured current values.

The evaluation device is preferably designed to compare the currents measured by the first and second current detectors and to determine the monitoring signal taking this comparison into account. This makes determining the operating status particularly easy and reliable. The evaluation device can optionally also be designed to compare the current measured by the first current detector and the current measured by the second current detector with a reference value and to determine the monitoring signal taking this comparison into account. This allows the reliability of determining the operating state to be further increased, and additional error states such as wire shorts or insulation faults, which manifest themselves in deviations from expected current values, can be detected.

For fundamental reasons, current detectors have a relatively low resistance. The first and second current detectors preferably each have an internal resistance with respect to direct currents of less than 20 Ω, particularly preferably less than 10 Ω and in particular less than 5 Ω. Preferably, the internal resistances of the first and second current detectors match to facilitate a direct comparison.

The device can in particular be designed for alternative monitoring of two target positions of the field element, for example the end positions of a switch or barrier. In particular, the device can be used with a field element with a first and a second limit switch, these limit switches being as explained above Figures 3A-3D are interconnected and connected to the four-wire interface of the field element. Specifically, the device can have a monitoring target position selection switch, which is designed to switch between a first monitoring state for monitoring a first target position and a second To switch the monitoring state to monitoring a second target location. In the first monitoring state, the monitoring voltage is present between the second and third terminals of the four-wire interface, and the second current detector measures the current between the first and fourth terminals, and in the second monitoring state, the monitoring voltage is present between the first and third terminals of the four-wire interface , and the second current detector measures the current between the first and fourth terminals. The first current detector always measures the current through the third connection of the four-wire interface, regardless of the monitoring status.

• eine Umstell-Gleichspannungsquelle zur Erzeugung einer Umstellspannung; und
• einen Umstell-Ziellagenwahlschalter, der dazu ausgebildet ist, die Umstellspannung alternativ mit einer ersten Polarität für die erste Ziellage oder mit einer dazu entgegengesetzten zweiten Polarität für die zweite Ziellage an zwei Anschlüsse der Vierdraht-Schnittstelle, insbesondere an den zweiten und vierten Anschluss, anzulegen.

According to a second aspect of the invention, the device has a changeover control for changing the field element between a first and a second target position. This includes:

• a changeover DC voltage source for generating a changeover voltage; and
• a changeover target position selector switch, which is designed to alternatively apply the changeover voltage with a first polarity for the first target position or with an opposite second polarity for the second target position to two connections of the four-wire interface, in particular to the second and fourth connection.

The changeover control is also designed to apply the changeover voltage to the other two connections of the four-wire interface, in particular to the first and third connections, preferably with a fixed polarity.

In this way, the device is designed in a special way to supply a field element via the four-wire interface with energy for switching from a DC voltage source. The desired target position is coded via the polarity of the changeover voltage at two of the four connections of the four-wire interface. Energy is transferred via all four connections of the four-wire interface to minimize line losses.

The first and second aspects of the invention can be advantageously combined. For this purpose, the device can have a master operating mode switch, which is designed to switch the device between a monitor operating mode and a changeover operating mode, wherein in the monitor operating mode the master operating mode switch connects the monitoring device to the four-wire interface and in the changeover operating mode the master operating mode switch The changeover control connects to the four-wire interface. The changeover voltage and the monitoring voltage are preferably polarized in such a way that they cause currents with opposite current directions through one of the connections of the four-wire interface, preferably the third connection, when a field element is operated with the device. Specifically, in the monitor operating mode, a pole of the monitoring DC voltage source is preferably connected to the relevant connection of the four-wire interface, and in the changeover operating mode, a pole of the changeover DC voltage source is connected to this connection of the four-wire interface, these poles having opposite signs .

The device can have a master control which is designed to receive a changeover command from a signal box function for changing the field element to a new target position and, depending on the changeover command, to bring the master operating mode switch from the monitor operating mode to the changeover operating mode as well as to operate the monitoring target position selector switch and the changeover target position selector switch according to the new target position.

In order to enable an automatic switch back to the monitor operating mode as soon as a changeover process has been completed, the changeover control can have a changeover current detector for measuring a changeover current that is caused in the field element by the changeover voltage, and the master control can be designed to detect the changeover current detector to record the measured changeover current and, depending on the changeover current, to switch the master operating mode switch back from the changeover operating mode to the monitor operating mode. This is based on the knowledge that the changeover current drops sharply after the changeover process has ended. This drop can be detected by the master control and used to switch the operating mode.

• eine Vierdraht-Schnittstelle mit einem ersten, zweiten, dritten und vierten Anschluss;
• einen ersten Endlagenschalter; und
• einen zweiten Endlagenschalter,
• wobei der erste Endlagenschalter eine erste Stellung einnimmt, wenn sich das Feldelement in einer ersten Endlage befindet und eine zweite Stellung einnimmt, wenn sich das Feldelement ausserhalb der ersten Endlage befindet,
• wobei der zweite Endlagenschalter eine erste Stellung einnimmt, wenn sich das Feldelement in einer zweiten Endlage befindet und eine zweite Stellung einnimmt, wenn sich das Feldelement ausserhalb der zweiten Endlage befindet,
• wobei jeder der Endlagenschalter als Wechselschalter mit einem Mittenkontakt und zwei Aussenkontakten ausgebildet ist,
• wobei jeder der Aussenkontakte jedes Endlagenschalters mit jeweils einem der Aussenkontakte des anderen Endlagenschalters verbunden ist, um jeweils einen gemeinsamen Aussenkontakt zu bilden, und
• wobei das Feldelement dazu ausgebildet ist, einen Betriebsmodus einzunehmen, in dem der Mittenkontakt des ersten Endlagenschalters mit dem ersten Anschluss der Vierdraht-Schnittstelle verbunden ist, der Mittenkontakt des zweiten Endlagenschalters mit dem zweiten Anschluss der Vierdraht-Schnittstelle verbunden ist, einer der gemeinsamen Aussenkontakte mit dem dritten Anschluss der Vierdraht-Schnittstelle verbunden ist, und der andere gemeinsame Aussenkontakt mit dem vierten Anschluss der Vierdraht-Schnittstelle verbunden ist.

The present invention also provides a field element which is designed to operate with a device of the above type. The field element has:

• a four-wire interface having first, second, third and fourth terminals;
• a first limit switch; and
• a second limit switch,
• wherein the first limit switch assumes a first position when the field element is in a first end position and assumes a second position when the field element is outside the first end position,
• wherein the second limit switch assumes a first position when the field element is in a second end position and assumes a second position when the field element is outside the second end position,
• whereby each of the limit switches is designed as a changeover switch with a center contact and two external contacts,
• wherein each of the external contacts of each limit switch is connected to one of the external contacts of the other limit switch in order to form a common external contact, and
• wherein the field element is designed to assume an operating mode in which the center contact of the first limit switch is connected to the first connection of the four-wire interface, the center contact of the second limit switch is connected to the second connection of the four-wire interface, one of the common external contacts the third connection of the four-wire interface is connected, and the other common external contact is connected to the fourth connection of the four-wire interface.

The field element also has an element which is non-linear with respect to direct currents and which is arranged in the field element in such a way that a current flowing through the third connection of the four-wire interface flows through it and thereby generates an auxiliary voltage which depends non-linearly on this current.

In terms of circuitry, the field element is basically constructed according to the principles as described above based on Figures 3A-3D were explained. In addition, a non-linear element generates an auxiliary voltage. This means that a flexible energy source is available in the field element, which can be used to supply energy for additional functions of the field element, regardless of the size of the current flowing through the four-wire interface, without the need for additional wires between the control and monitoring device and the field element become. The auxiliary voltage can be used in particular to power an auxiliary power supply and/or to charge an energy storage device. With the auxiliary power supply, for example, a device for generating an AC design signal as in EP3643579A1 operate. Further possible uses of the auxiliary voltage are described in more detail below.

• eine Motorsteuerung;
• einen von der Motorsteuerung angesteuerten Antriebsmotor, wobei es sich bei dem Antriebsmotor vorzugsweise um einen Gleichstrommotor, insbesondere um einen bürstenlosen, elektronisch kommutierten Gleichstrommotor handelt, und wobei die Motorsteuerung dazu ausgebildet ist, Antriebsenergie für den Antriebsmotor über die Vierdraht-Schnittstelle zu beziehen; und
• einen Feldelement-Betriebsmodus-Umschalter, der dazu ausgebildet ist, abhängig von einer Stromrichtung des durch den dritten Anschluss der Vierdraht-Schnittstelle fliessenden Stroms das Feldelement zwischen einem Überwacher-Betriebsmodus und einem Umstell-Betriebsmodus des Feldelements umzuschalten, wobei der Feldelement-Betriebsmodus-Umschalter vorzugsweise dazu ausgebildet ist, Energie aus der Hilfsspannung zu beziehen,
• wobei im Überwacher-Betriebsmodus der Mittenkontakt des ersten Endlagenschalters mit dem ersten Anschluss der Vierdraht-Schnittstelle verbunden ist, der Mittenkontakt des zweiten Endlagenschalters mit dem zweiten Anschluss der Vierdraht-Schnittstelle verbunden ist, einer der gemeinsamen Aussenkontakte mit dem dritten Anschluss der Vierdraht-Schnittstelle verbunden ist, und der andere gemeinsame Aussenkontakt mit dem vierten Anschluss der Vierdraht-Schnittstelle verbunden ist,
• wobei im Umstell-Betriebsmodus alle vier Anschlüsse der Vierdraht-Schnittstelle mit der Motorsteuerung verbunden sind,
• wobei die Motorsteuerung vorzugsweise dazu ausgebildet ist, eine Polarität einer Spannung, die zwischen dem zweiten und vierten Anschluss der Vierdraht-Schnittstelle anliegt, zu bestimmen und eine Bewegungsrichtung des Antriebsmotors in Abhängigkeit von der Polarität zu steuern, und
• wobei die Motorsteuerung vorzugsweise dazu ausgebildet ist, einen ersten Teil der Antriebsenergie für den Antriebsmotor aus der Spannung, die zwischen dem zweiten und vierten Anschluss der Vierdraht-Schnittstelle anliegt, unabhängig von der Polarität dieser Spannung zu beziehen und einen zweiten Teil der Antriebsenergie aus einer Spannung, die zwischen dem ersten und dritten Anschluss anliegt, zu beziehen.

The field element can also have:

• an engine controller;
• a drive motor controlled by the motor control, the drive motor preferably being a direct current motor, in particular a brushless, electronically commutated direct current motor, and the motor control being designed to obtain drive energy for the drive motor via the four-wire interface; and
• a field element operating mode switch, which is designed to switch the field element between a monitor operating mode and a changeover operating mode of the field element depending on a current direction of the current flowing through the third connection of the four-wire interface, the field element operating mode switch is preferably designed to obtain energy from the auxiliary voltage,
• wherein in the monitor operating mode, the center contact of the first limit switch is connected to the first connection of the four-wire interface, the center contact of the second limit switch is connected to the second connection of the four-wire interface, one of the common external contacts is connected to the third connection of the four-wire interface is, and the other common external contact is connected to the fourth connection of the four-wire interface,
• whereby in the changeover operating mode all four connections of the four-wire interface are connected to the motor control,
• wherein the motor control is preferably designed to determine a polarity of a voltage that is present between the second and fourth terminals of the four-wire interface and to control a direction of movement of the drive motor depending on the polarity, and
• wherein the motor control is preferably designed to obtain a first part of the drive energy for the drive motor from the voltage that is present between the second and fourth connection of the four-wire interface, regardless of the polarity of this voltage, and a second part of the drive energy from a voltage , which is located between the first and third connections.

The field element is therefore designed in a special way to be operated with a DC voltage supply via the four-wire interface and to be controlled by a device of the type described above.

The field element can have a rechargeable energy storage device which is designed to charge energy at least in the monitor operating mode of the field element from the auxiliary voltage and, if necessary, deliver additional energy to the motor control.

The present invention also provides a railway system which has a field element in its outdoor system and a device for operating the field element of the type specified above in its indoor system. A four-wire cable connects the four-wire interface of the device to the four-wire interface of the field element. The field element has a first limit switch and a second limit switch. The first limit switch assumes a first position when the field element is in a first end position and a second position when the field element is outside the first end position. The second limit switch assumes a first position when the field element is in a second end position and a second position when the field element is outside the second end position. The field element is designed to assume an operating mode in which the limit switches are connected to the four-wire interface of the field element in such a way that the monitoring voltage causes a current that flows through both the first and the second current detector when the first limit switch is in the first position and the second limit switch is in the second position or if the second limit switch is in the first position and the first limit switch is in the second position, and that the monitoring voltage causes a current that flows through the first current detector but not the second current detector, when both the first and second limit switches are in the second position. The field element can in particular be designed as described in more detail above.

The system can also have one or more reference resistors which are arranged in the field element and/or in the device for its operation in such a way that they influence currents through the connections of the four-wire interface of the field element, which are caused by the monitoring voltage. Preferably, at least two reference resistors are present, with at least one of the reference resistors being arranged in the field element and at least one of the reference resistors being arranged in the device, with the reference resistors preferably having the same resistance value. This makes it easier to detect wire shorts and insulation faults. The reference resistors each preferably have a resistance value between 20 and 200 Ω.

In a preferred embodiment, at least a first and second reference resistor are present, wherein the first reference resistor is arranged such that a current flows through it through the first connection of the four-wire interface, and wherein the second reference resistor is arranged such that it is supplied by a Current flows through the second connection of the four-wire interface. Optionally, a third reference resistor is also present, with the third reference resistor being arranged in such a way that a current flows through it through the fourth connection of the four-wire interface. The first and second reference resistors are preferably arranged in the field element and the third reference resistor is arranged in the monitoring device.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1A

eine schematische Darstellung einer Weiche in ihrer linken Endlage;

Fig. 1B

eine schematische Darstellung einer Weiche in ihrer rechten Endlage;

Fig. 2

einen schematischen Schaltplan einer traditionellen Vierdraht-Schnittstelle mit einem zugehörigen Weichenantrieb und einer zugeordneten Steuereinheit;

Fig. 3A-3D

mögliche Stellungen der Endlagenschalter des Weichenantriebs der Fig. 2 für verschiedene Zustände der Weiche;

Fig. 4A-4B

Diagramme zur Illustration der Funktionsweise einer traditionellen Endlagenüberwachung über eine Vierdraht-Schnittstelle;

Fig. 5A-5D

Diagramme zur Illustration der Funktionsweise einer Endlagenüberwachung über eine Vierdraht-Schnittstelle gemäss einer Ausführungsform der Erfindung; und

Fig. 6A-6B

ein Diagramm zur Illustration der Funktionsweise einer vollständigen Weichensteuerung gemäss einer Ausführungsform der Erfindung.

Preferred embodiments of the invention are described below with reference to the drawings, which serve only for explanation and are not to be interpreted in a restrictive manner. In the drawings show:

Fig. 1A

a schematic representation of a switch in its left end position;

Fig. 1B

a schematic representation of a switch in its right end position;

Fig. 2

a schematic circuit diagram of a traditional four-wire interface with an associated switch machine and an associated control unit;

Figs. 3A-3D

possible positions of the limit switches of the point drive Fig. 2 for different states of the switch;

Figs. 4A-4B

Diagrams illustrating how traditional end position monitoring works over a four-wire interface;

Figs. 5A-5D

Diagrams to illustrate the functionality of end position monitoring via a four-wire interface according to an embodiment of the invention; and

Figs. 6A-6B

a diagram to illustrate the functionality of a complete switch control according to an embodiment of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS Definitions and conventions

Field element: A “field element” is a railway technical facility that is usually located on a railway line and is used to control, signal or monitor the railway line. Field elements can be motor-driven. Examples of motor-driven field elements in stationary railway technology are switches, barriers (level crossings), switching posts and gauge changing systems.

Field element control unit (object controller): A field element control unit is assigned to a field element and is used to control and/or monitor the field element. The field element control unit receives commands from an interlocking computer ("interlocking function") and interacts with the assigned field element based on these commands. The field element control unit can be designed to monitor the operating state of the assigned field element and to output a monitoring result to the signal box function.

Indoor system: The place where a field element control device is arranged is called the indoor system. The indoor facility can, for example, be a signal box room in a traditional signal box architecture. In a decentralized signal box architecture, the indoor system can, for example, be a control cabinet that is spatially separated from the signal box between the signal box and the outdoor system or can include such a control cabinet. The control cabinet can be located near the track. At Thales, such a control cabinet is also referred to as a “Trackside Control Unit (TCU)”.

Outdoor facility: The place where the field element is located is called the outdoor facility.

Current directions: The sign convention chosen for the current directions is that a current from the indoor system to the outdoor system has a positive sign and a current from the outdoor system to the indoor system has a negative sign.

Limit switch: In the context of the present disclosure, an at least single-pole changeover switch (often referred to as a "single pole changeover switch", SPCO switch) serves as the limit switch, the position of which depends on the operating state of a field element. The changeover switch alternatively connects a middle connection (“Common”, COM) to one of two external connections. The limit switch can be of the “make-before-break” (MBB) or “break-before-make” (BBM) type.

End position monitoring

An exemplary embodiment of a device according to the invention for end position monitoring is explained below using the control and monitoring of a field element in the form of a switch. The switch has a switch drive in the outdoor area. This is connected to a control unit in the indoor system via a four-wire interface. Unlike the example of Fig. 2 However, the required drive energy is not transferred from the control unit to the point drive by feeding in a three-phase alternating voltage via the four-wire interface. Instead, the drive energy is provided by a DC voltage supply. An exemplary embodiment of this type of energy transmission is described below in connection with Figures 6A and 6B explained in more detail. First, however, should be based on the Figures 5A to 5D an exemplary embodiment of an end position monitoring device can be illustrated. For reasons of better clarity, Figures 5A to 5D the components for transmitting the drive energy are omitted.

Instead of the three windings of the drive motor, three reference resistors R _{ref ,1} , R _{ref ,2} and R _{ref ,4} are provided in this exemplary embodiment. In the present exemplary embodiment, two of these reference resistors, namely R _{ref ,1} and R _{ref ,2} , are arranged in the external system (ie in or near the point drive) and connected to the respective center connection of the limit switches m1 and m2. The reference resistor R _{ref ,1} is in a line to connection X1 of the four-wire interface, the reference resistor R _{ref ,2} is in a line to connection X2. These two reference resistors replace the windings L1 and L2 Fig. 2 . The third reference resistor, R _{ref, 4} , on the other hand, is arranged in the indoor system (ie at the control device). The reference resistor R _ref , ₄ is located in a line to the connection X4, so that the current flows through the connection X4 through this reference resistor. The reference resistor R _ref , ₄ does not directly replace the winding L3 Fig. 2 , which is located in the outdoor system and is connected to connection X3 of the four-wire interface. The reference resistors all have the same value R _ref = R _{ref, 1} = R _ref , ₂ = R _{ref, 4} .

A four-core cable runs between the indoor system and the outdoor system, each of which has a cable resistance R _line .

As in the prior art Figures 4A and 4B a DC voltage source 210 is present, which provides a monitoring voltage U _sup , and a first low-resistance current detector 211 is connected in series with the DC voltage source 210, so that it determines the current I ₁ flowing through the connection X3. Unlike in the prior art, a second low-resistance current detector 213 is provided. This is connected in series with the reference resistor R _ref , ₄ and determines the current I ₂ flowing through the connection X4. The output signals of the two current detectors 211, 213 are led to an evaluation device 215, which compares these output signals with one another and with reference values in order to draw conclusions about the operating state of the switch.

A monitoring target position selector switch 214 in the form of a relay with a two-pole changeover switch (“Double Pole Double Throw [DPDT] Switch” or “Double Pole Changeover [DPCO] Switch”) connects, depending on the position, the pole of the DC voltage source 210 that is not connected to X3 with the connection X1 of the four-wire interface and the connection of the current detector 213 that is not connected to X4 with the connection X2, or vice versa. The position of this target position selector switch 214 determines which of the two end positions (left or right end position) should be monitored.

A non-linear component in the form of a Zener diode (nowadays usually referred to as a Zener diode) D1 is located in the external system (ie in or near the point drive) in a line to connection X3. The monitoring voltage U _sup and the Z diode D1 are polarized relative to one another in such a way that the Z diode D1 is flowed through in the reverse direction, so that a breakdown voltage drops across it, which forms an auxiliary voltage U _aux . An auxiliary power supply 14 is connected in parallel to the Zener diode, the function of which is related to the Fig. 6 will be explained in more detail. Part of the current I ₁ feeds the auxiliary power supply 14, another part flows through the Zener diode D1. The auxiliary voltage U _aux depends only slightly on the current portion that flows through the Zener diode and can therefore be viewed as constant in a first approximation. This arrangement makes it possible to supply the auxiliary power supply 14 with an electrical power whose maximum, in a first approximation, corresponds to the product of the auxiliary voltage U _aux and the current I ₁ . The auxiliary voltage U _aux is preferably in the range of 5%-60% of the monitoring voltage U _sup , in absolute numbers preferably between 3 and 30 V.

During monitoring operation, the outdoor system has a higher impedance than the indoor system and is thereby determining the current, unlike in the prior art Figures 4A and 4B , where the indoor system has a higher resistance and therefore determines the current.

In the Fig. 5A the switch takes its left end position. The limit switches m1, m2 are in the position Fig. 3A , and the target position selector switch 214 is in the left position, in which the end position monitoring device checks whether the field element actually occupies the left end position. The current caused by the monitoring voltage U _sup flows through all three reference resistors and all four wires of the connecting cable. The following current values result: $$I_1=I_2=\frac{U_{\mathit{sup}}-U_{\mathit{aux}}}{3R_{\mathit{ref}}+4R_{\mathit{line}}}.$$

In a calculation example, U _sup = 48 V, U _aux = 24 V, R _ref = 39 Ω, R _line = 2 Ω. This then follows I ₁ = I ₂ = 192 mA. The evaluation device 215 determines whether the two currents I ₁ and I ₂ are the same and whether their amount is in the expected range, and thereby concludes that the left end position is correct.

In the Fig. 5B the field element assumes its right end position. The limit switches m1, m2 are in the position Fig. 3B , and the target position selector switch 214 is in the right position, in which the end position monitoring device checks whether the field element actually occupies the right end position. The currents I ₁ and I ₂ take the same values as in Fig. 5A and accordingly it can be concluded in the same way that the right end position is correct.

$$I_2=0.$$

In the Fig. 5C the field element is in transit from the right to the left end position or in an opened state out of the left end position. An opened state is when a switch with a correct end position is driven incorrectly from the point heart. The turnout tongue is pushed away by the wheel flange. The same switching condition can also result from “not reaching the end position”. The cause can be jammed stones, mechanical adjustment errors, mechanical distortion or malfunctions in the limit switches m1 and m2. One also speaks more generally of a “cut open” switch. In this state, the limit switches m1, m2 are in the position Fig. 3C , and the target position selector switch 214 is in the left position, in which the end position monitoring device checks whether the field element occupies the left end position. The circuit now only contains the DC voltage source 210, the current detector 211, the Zener diode D1, the reference resistor R _ref,2 and two wires for the connections X2 and X3 of the four-wire interface. The resulting current values are: $$I_1=\frac{U_{\mathit{sup}}-U_{\mathit{aux}}}{R_{\mathit{ref}}+2R_{\mathit{line}}},$$

$$I_2=0.$$

In the calculation example above: I ₁ = 558 mA, I ₂ = 0. The current I ₁ is therefore significantly more than twice as high as when the end position was reached, and the current I ₂ is zero. The evaluation device 215 determines whether the current I ₂ is actually zero and whether the current I ₁ is in the expected range, and thus concludes that the cut state exists.

In the Fig. 5D the field element is in transit from the right to the left end position or in an opened/cut state from the right end position. As can be easily verified, the same current values result as in the Fig. 5C .

As can also be easily verified, this arrangement can also be used to detect wire shorts between the individual wires in the connecting cable or insulation faults. All possible combinations of wire connections result in current values I ₁ and I ₂ that deviate from the current values in the end positions. The evaluation device 215 can accordingly be designed to compare these current values with reference values in order to determine and localize wire shorts or insulation faults, ie to assign a detected wire short to a pair of lines. In the present arrangement, this is made easier by the fact that the reference resistor R _ref , ₄ is located in the indoor system, while the other two reference resistors R _{ref , 1} and R _ref , ₂ are located in the outdoor system, so that in the case of certain wire connections, these reference resistors each current no longer flows through it after the operating state.

Depending on the operating state, some possible wire shorts (X2 to X3 or X1 to X3) cause a short circuit in which only the DC voltage source 210 and the current detector 211 are in the circuit. To limit the short-circuit current, the DC voltage source 210 can be equipped with a current limiting function. Optionally, a fourth reference resistor can be provided in the indoor system in the line to connection X3, which limits the short-circuit current. However, this makes the signal-to-noise ratio less favorable for resolving the other wire connection combinations.

Complete switch drive

In the Figures 6A and 6B An exemplary embodiment will now be explained in which not only the end position monitoring takes place via the four-wire interface, but also the drive energy is provided by a DC voltage supply via the four-wire interface. This illustrates Fig. 6A the circuitry structure of the indoor system, Fig. 6B that of the outdoor area.

A control unit 20 in the indoor system includes, on the one hand, a monitoring device 21 and, on the other hand, a changeover control 22. A master operating mode switch 23 in the form of a isolating relay with a four-pole changeover switch connects the outdoor system either to the monitoring device 21 ("monitoring operation") or the changeover control 22 ( "conversion operation"). The master operating mode switch 23 is actuated by means of a master control 25, which receives digital control commands from a signal box function.

The monitoring device 21 of the indoor system is as in the Figures 5A and 5B constructed, and the above statements are referred to Figures 5A and 5B referred. For reasons of better clarity, the evaluation device 215 was in the Fig. 6A omitted.

The changeover control 22 includes a high-power DC voltage source 220, which provides a drive voltage U _D. In the present exemplary embodiment, the drive voltage U _D has the same amount as the monitoring voltage U _sup . A changeover current detector 221 is connected in series with the DC voltage source 220. The changeover current detector 221 outputs an output signal, which depends on the current I _D through the changeover current detector 221, to the master controller 25. The connection X3 of the four-wire interface is connected to the negative pole of the DC voltage source 220 in changeover mode, the connection The polarity of the connections X2 and X4 depends on the desired direction of rotation or the target position: To change towards the left end position, the connection Polarity reversed. A two-pole changeover switch connected as a pole inverter is used for this purpose, which is referred to below as the changeover target position selector switch 224 and which is connected to the monitoring target position selector switch 214 of the end position monitoring device 21 is forcibly coupled and is actuated together with this as a common relay 24 by the master control 25. Based on the polarity of the voltage between the connections X2 and Unlike in the prior art, the target position is not determined by the phase position of a three-phase alternating voltage at the connections X1, X2 and X3, but rather by the polarity of a direct voltage at the connections X2 and X4.

Due to the differently polarized voltage sources 210, 220, the direction of the current that flows through the connection X3 in monitoring mode is opposite to the direction of the current that flows through this connection in the changeover mode. This enables the components of the point drive in the outdoor system to recognize in which operating mode the point drive should be operated without the need for another wire in the cable 30 to transmit this information.

Overall, the control unit 20 in the indoor system codes the operating mode by the direction of the current through the connection X3 and the target position in the changeover mode by the polarity of a direct voltage at the connections X2 and X4.

The field element 12 in the outdoor system has a two-pole changeover switch 123, which serves to switch the field element between the monitoring mode and the changeover mode depending on the direction of the current through the connection X3. For this purpose, the changeover switch 123 connects the connections X2 and Together, the changeover switch 123 and the control elements 142, 143 form a field element operating mode switch in the outdoor system.

The motor control 121 controls a DC motor 120. The DC motor is preferably a brushless motor with Hall element-controlled electronic commutation. The motor controller 121 has several connections as follows. Two connections DP+ and DP- are used to supply energy to the motor control in changeover mode. In changeover mode, these connections are connected to the connections X1-X4 of the four-wire interface via diodes D7 and D8 in such a way that regardless of the selected target position (i.e. regardless of the polarity of the connections X2 and Both connections of the four-wire interface carry the current flowing in the opposite direction from the negative connection DP- (namely X3 and, depending on the target position, X4 or X2). This even distribution of the supply current to the four connections of the four-wire interface minimizes line losses in the individual wires of the connecting cable 30 between the indoor system and the outdoor system.

Two "Uml" connections, together with two diodes D9, are used to detect the desired target position based on the polarity between the connections X2 and X4 of the four-wire interface. Depending on which of these two connections a positive voltage is present, the desired target position and thus the desired direction of rotation of the motor 120 are determined.

Two further “EL” connections are used to detect whether the desired target position has actually been reached (end position detection). Based on the voltages at these connections, the motor control 121 recognizes which position the limit switches m1, m2 are in.

An auxiliary power supply 14 is supplied with a voltage U _aux by a bipolar nonlinear element (specifically: an arrangement of two series-connected Z diodes D2, D3 with opposite polarity) and a bridge rectifier 141. The auxiliary power supply 14 supplies, in particular, the two actuating elements 142, 143 with energy. The actuators 142, 143 sense the direction of current through the bipolar nonlinear element by sensing the polarity of the voltage across that element, thereby determining the direction of current through the terminal X3 of the four-wire interface. If the current direction is positive, the actuating element 142 actuates the changeover switch 123 in such a way that it reaches the position for monitoring operation. If the current direction is negative, the actuating element 143 actuates the changeover switch 123 in such a way that it moves into the position for changeover operation, and at the same time transmits a signal to the motor control 121 that the changeover should begin.

Optionally, a rechargeable energy storage device 144 (eg a rechargeable battery) is also provided, which supplies the engine control 121 with power in the changeover mode Drive energy supported. The energy storage is continuously charged by the actuating element 142 in monitoring mode and can deliver energy to the motor control 121 in the changeover mode. Such an energy storage device is particularly useful for long lines between the indoor and outdoor systems, where the line losses in changeover operation can be significant, since the supply voltage U _D is relatively low and the currents through the cable 30 are therefore relatively high.

Two diodes D3, D4 ensure that in changeover mode a current can flow from connection X1 to connection X3 through the outdoor system, while in monitoring mode a current is led from connection X3 to the end position contacts m1, m2.

Operation of the switch control

If the switch is to be changed to a new target position, proceed as follows. Initially, both the master operating mode switch 23 of the indoor system and the field element operating mode switch of the outdoor system with the changeover switch 123 are in the position for monitoring operation. The master control device 25 receives a command to change to a new target position. The master control device 25 now controls the elements 23 and 24 in such a way that the new target position is set with the target position selector switches 214, 224 and the master operating mode switch 23 is brought into the position for changeover operation. These processes cause a reversal of the current direction through the X3 connection of the four-wire interface. This activates the control element 143 in the outdoor system and automatically switches the changeover switch 123 to the position for changeover operation. The motor control 121 now receives, on the one hand, a signal for switching from the actuating element 143 and, on the other hand, is supplied with drive energy for the drive motor 120 via the four-wire interface. The motor control 121 determines the desired target position based on the voltages at the “Uml” connections. The motor control 121 now controls the motor 120 so that it starts smoothly in the required direction. After a certain time or a certain number of motor revolutions (or commutator pulses), the motor control 121 reduces the speed of the motor 120 until the limit switches m1, m2 of the motor control 121 signal at the "EL" connections that the desired end position has been reached. The motor control 121 now stops the motor 120. The motor control 121 therefore draws massively less energy via the four-wire interface. As a consequence, the changeover current detector 221 in the changeover controller 22 detects a greatly reduced current I _D . The corresponding signal from the changeover current detector 221 causes the master controller 25 to return the master operating mode switch 23 to the position for monitoring operation. As a result, the direction of the current through the connection

Monitoring in the monitor operation now takes place in the same way as in connection with the Figures 5A and 5B was explained.

Modifications

The invention was explained above using an exemplary embodiment. Of course, many modifications are possible.

In particular, controlled semiconductor switching elements such as MOSFETs can also be used instead of mechanical switches. Instead of Zener diodes, other non-linear elements can also be used, which enable the decoupling of an auxiliary voltage U _aux .

In the present exemplary embodiment, all polarities can be reversed as long as the flow directions of the diodes are adjusted accordingly.

The monitoring voltage U _sup and the drive voltage U _D can be different. In particular, the drive voltage U _D must be higher than the monitoring voltage U _sup in order to reduce the currents through the cable 30 during the changeover operation and thereby minimize line losses. This can be particularly useful with a long cable 30.

The end position monitoring device can also be operated with just a single current detector; However, this is associated with a reduction in the informative value of the monitoring results.

The number of reference resistors can vary from three, but there should be at least one reference resistor to avoid a short circuit. At least two reference resistors are preferably used, which are arranged in such a way that the current flows through them through the connections X1 and X2.

While the drive motor 120 is preferably a brushless, electronically commutated DC motor, other types of motors also come into consideration. In particular, it can also be an AC motor, and the motor controller 121 can accordingly have an inverter that generates an AC voltage for the motor.

REFERENCE SYMBOL LIST

11

Soft

12

Switch drive/field element

13

push rod

20

Control device

21

End position monitoring device

22

Changeover control

23

Operating mode switch

24

Relay for target position selector switch

25

Master control

30

Cable

120

drive motor

121

Motor control

141

Bridge rectifier

142

Control element for monitoring operation

143

Control element for changeover operation

144

Energy storage

210

Monitoring DC voltage source

211

Current detector

212

Voltage detector

213

Current detector

214

Monitoring target position selector switch

215

Evaluation device

220

Conversion DC voltage source

221

Changeover current detector

224

Changeover target position selector switch

m1, m2

Limit switch

D1-D10

diodes

L1-L3

windings

X1-X4

Connections of a four-wire interface

Usup

Monitoring voltage

U.D

Drive voltage

Usup

Auxiliary voltage

I1, I2

streams

Rref,1...4

Reference resistors

Rline

Cable resistance

Claims (15)

Device (20) for operating a field element (12) in a railway system, with a four-wire interface with a first, second, third and fourth connection (X1-X4) and with a monitoring device (21) for monitoring an operating state of the field element ( 12), the monitoring device (21) having: a monitoring DC voltage source (210) for generating a monitoring voltage ( U _sup ) between two connections (X2-X3 or X1-X3) of the four-wire interface; and a first current detector (211) for measuring a current ( I ₁ ) through one of those connections (X3) of the four-wire interface at which the monitoring voltage ( U _sup ) is generated, characterized in that the monitoring device (21) also has: a second current detector (213) for measuring a current ( I ₂ ) between those connections (X1-X4 or X2-X4) of the four-wire interface between which the monitoring voltage ( U _sup ) is not generated; and an evaluation device (215) which is designed to determine a monitoring signal (E) based on the currents ( I ₁ , I ₂ ) measured by the first and second current detector (211, 213) and to output the monitoring signal. Device (20) according to claim 1, wherein the evaluation device (215) is designed to compare the currents ( I ₁ , I ₂ ) measured by the first and second current detectors (211, 213) and the monitoring signal (E) taking this into account to determine comparison,
wherein the evaluation device (215) is optionally also designed to compare the current ( I ₁ ) measured by the first current detector and the current ( I ₂ ) measured by the second current detector with a reference value and the monitoring signal (E) taking this comparison into account to determine. The device (20) according to claim 1 or 2, wherein the first and second current detectors (211, 213) each have an internal resistance of less than 20 Ω, and preferably the internal resistances of the first and second current detectors (211, 213) match. Device (20) according to one of the preceding claims, comprising:
a monitoring target position selector switch (214) which is designed to switch between a first monitoring state for monitoring a first target position and a second monitoring state for monitoring a second target position, wherein the first current detector (211) detects the current ( I ₁ ) through the third connection (X3) of the four-wire interface, whereby in the first monitoring state the monitoring voltage ( U _sup ) is present between the second and third connections (X2, X3) of the four-wire interface and the second current detector (213) measures the current ( I ₂ ) between the first and fourth connections (X1, X4), and wherein in the second monitoring state the monitoring voltage ( U _sup ) is present between the first and third connections ( X1 _, ) between the first and fourth connection (X1, X4). Device (20) for operating a field element (12) in a railway system, with a four-wire interface with a first, second, third and fourth connection (X1-X4) and a changeover control (22) for changing the field element (12) between a first and a second target location,
characterized in that the changeover control (22) has: a changeover DC voltage source (220) for generating a changeover voltage (U _D ); and a changeover target position selector switch (224), which is designed to send the changeover voltage ( _UD ) alternatively with a first polarity for the first target position or with an opposite second polarity for the second target position to two connections (X2, X4) of the four-wire create an interface, wherein the changeover control (22) is also designed to apply the changeover voltage ( _UD ) to the other two connections (X1, X3) of the four-wire interface, preferably with a fixed polarity. Device (20) according to one of claims 1 to 4, wherein the device (20) is also designed according to claim 5, and wherein the device (20) has a master operating mode switch (23) which is designed to switch the device (20) between a monitor operating mode and a changeover operating mode, the master operating mode switch being in the monitor operating mode (23) the monitoring device (21) with the Four-wire interface connects and in the changeover operating mode the master operating mode switch (23) connects the changeover control (22) to the four-wire interface, wherein the monitoring DC voltage source (210) and the changeover DC voltage source (220) are preferably polarized such that the changeover voltage ( U _D ) in the changeover operating mode has an opposite polarity than the monitoring voltage (U _sup ) in the monitoring operating mode at one of the Connections (X3) of the four-wire interface are present. Device (20) according to claim 6, further comprising:
a master control (25), which is designed to receive a changeover command from a signal box function for changing the field element to a new target position and, depending on the changeover command, the master operating mode switch (23) from the monitor operating mode to the changeover operating mode and to operate the monitoring target position selector switch (214) and the changeover target position selector switch (224) according to the new target position. Device according to claim 7, wherein the changeover control (22) has a changeover current detector (221) for measuring a changeover current (I _D ), which is caused in the field element (12) by the changeover voltage ( U _D ), and wherein the master control (25) is designed to detect the changeover current ( _ID ) measured by the changeover current detector (221) and, depending on the changeover current ( _ID ), the master operating mode switch (23) from the changeover operating mode to the monitor -Switch back operating mode. Field element (12), which is designed for operation with a device according to one of claims 1 to 8, comprising: a four-wire interface with first, second, third and fourth connections (X1-X4); a first limit switch (m1); and a second limit switch (m2), wherein the first limit switch (m1) assumes a first position when the field element (12) is in a first end position and assumes a second position when the field element (12) is outside the first end position, wherein the second limit switch (m2) assumes a first position when the Field element (12) is in a second end position and assumes a second position when the field element (12) is outside the second end position, wherein each of the limit switches (m1, m2) is designed as a changeover switch with a center contact and two external contacts, wherein each of the external contacts of each limit switch (m1, m2) is connected to one of the external contacts of the other limit switch in order to form a common external contact, and wherein the field element (12) is designed to assume an operating mode in which the center contact of the first limit switch (m1) is connected to the first connection (X1) of the four-wire interface, and the center contact of the second limit switch (m2) is connected to the second connection (X2) is connected to the four-wire interface, one of the common external contacts is connected to the third connection (X3) of the four-wire interface, and the other common external contact is connected to the fourth connection (X4) of the four-wire interface, characterized in that the field element (12) also has:
an element (D1, D2) which is non-linear with respect to direct currents and which is arranged in the field element (12) in such a way that a current flowing through the third connection (X3) of the four-wire interface flows through it and thereby generates an auxiliary voltage ( U _aux ), which depends non-linearly on this current. Field element (12) according to claim 9, further comprising: a motor control (121); a drive motor (120) controlled by the motor control (121), the drive motor (120) preferably being a direct current motor, in particular a brushless, electronically commutated direct current motor, and the motor control (121) being designed to provide drive energy for to obtain the drive motor (120) via the four-wire interface; and a field element operating mode switch (123, 142, 143), which is designed to switch the field element (12) between a monitor operating mode and a changeover depending on a current direction of the current flowing through the third connection (X3) of the four-wire interface -To switch operating mode, the field element operating mode switch (123, 142, 143) preferably being designed to obtain energy from the auxiliary voltage ( U _aux ), wherein in the monitor operating mode, the center contact of the first limit switch (m1) is connected to the first connection (X1) of the four-wire interface, and the center contact of the second limit switch (m2) is connected to the second Connection (X2) of the four-wire interface is connected, one of the common external contacts is connected to the third connection (X3) of the four-wire interface, and the other common external contact is connected to the fourth connection (X4) of the four-wire interface, wherein in the changeover operating mode all four connections (X1-X4) of the four-wire interface are connected to the motor control (121), wherein the motor control (121) is preferably designed to determine a polarity of a voltage that is present between the second and fourth connections (X2, X4) of the four-wire interface and to determine a direction of movement of the drive motor (120) depending on the polarity control, and wherein the motor control (121) is preferably designed to generate a first part of the drive energy for the drive motor (120) from the voltage that is present between the second and fourth connections (X2, X4) of the four-wire interface, regardless of the polarity of this voltage to obtain and to obtain a second part of the drive energy from a voltage that is present between the first and third connections (X1, X3). Field element (12) according to claim 10, further comprising:
a rechargeable energy storage device (144), which is designed to obtain charging energy from the auxiliary voltage ( U _aux ) at least in the monitor operating mode and, if necessary, to deliver additional energy to the motor control (121). Railway technical system, comprising: a device (20) according to any one of claims 1 to 8; a field element (12) having a four-wire interface with first, second, third and fourth terminals (X1-X4); and a cable (30) with four wires that connects the four-wire interface of the device (20) to the four-wire interface of the field element (12), wherein the field element (12) has a first limit switch (m1) and a second limit switch (m2), wherein the first limit switch (m1) assumes a first position when the field element (12) is in a first end position and assumes a second position when the field element (12) is outside the first end position; wherein the second limit switch (m2) assumes a first position when the field element (12) is in a second end position and assumes a second position when the field element (12) is outside the second end position, wherein the field element is designed to assume an operating mode in which the limit switches (m1, m2) are connected to the four-wire interface of the field element in such a way that the monitoring voltage ( U _sup ) causes a current that affects both the first and the second Current detector (211, 213) flows through when the first limit switch (m1) is in the first position and the second limit switch (m2) is in the second position or when the second limit switch (m2) is in the first position and the first limit switch ( m1) is in the second position, and that the monitoring voltage ( U _sup ) causes a current that flows through the first current detector (211), but not the second current detector (213), when both the first and the second limit switch (m1 , m2) are in the second position. Railway technical system according to claim 12, comprising: one or more reference resistors ( R _{ref, 1} -R _{ref, 4} ) , which are arranged in the field element (12) and/or in the device (20) for operating the field element (12) in such a way that they pass currents through the connections (X1 -X4) the four-wire interface of the field element (12), which is caused by the monitoring voltage ( U _sup ), influence, wherein preferably at least two reference resistors ( R _{ref, 1} -R _{ref, 4} ) are present, at least one of the reference resistors ( R _{ref, 1} -R _{ref, 4} ) being arranged in the field element (12) and at least one of the reference resistors ( R _{ref , 1} -R _{ref, 4} ) is arranged in the device (20), wherein the reference resistors ( R _{ref, 1} -R _{ref, 4} ) preferably have the same resistance value. Railway technical system according to claim 13, wherein at least a first and second reference resistor ( R _{ref, 1} , R _{ref, 2} ) are present, the first reference resistor ( R _{ref , 1} ) being arranged such that it receives a current through the first connection (X1) of the four-wire Interface is flowed through, and wherein the second reference resistor ( R _ref , ₁ ) is arranged such that a current flows through it through the second connection (X2) of the four-wire interface, wherein optionally a third reference resistor ( R _{ref ,4} ) is also present, the third reference resistor ( R _{ref ,4} ) being arranged in such a way that a current flows through it through the fourth connection (X4) of the four-wire interface, wherein preferably the first and second reference resistors ( R _{ref, 1} , R _{ref, 2} ) in the field element (12) and the third reference resistor ( R _{ref , 4} ) in the Monitoring device (21) is arranged. Railway technical system according to one of claims 12 to 14, wherein the field element (12) is designed according to one of claims 9 to 11.

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