Pulse circuit for supplying fault current in DC voltage supply networks

Abstract

The invention relates to a method for coupling devices (12 to 24) connected to a DC voltage supply network (10) with a power supply (26) using a supply voltage (28), wherein the power supply (26) is connected to a power supply interface (32), the electrical devices (12 to 24) are connected to the corresponding device interfaces (30), the device interfaces (30) are protected from overcurrent by means of a protective device (34) by having a sensor unit (50) detect the corresponding current and by means of a corresponding switching unit (48) disabling the corresponding device interface (30) in response to the detection of an overcurrent, and the power supply interface (32) is coupled to the protective device (34) by means of two electrical cables (38, 40), a pulse circuit (42) being connected to the electrical cables (38, 40), a charge quantity being discharged by means of the pulse circuit in the event of a voltage disturbance, the charge quantity being determined at least in response to the overcurrent and a predefined time period, wherein the switching element (36) is connected in series with a capacitor (44).

Description

Technical Field

[0001] The present invention relates to a power supply network for electrically coupling at least two electrical devices connected to the power supply network with at least one power supply connected to the power supply network using a predeterminable supply voltage, wherein the power supply network is designed as a DC voltage power supply network, the power supply network having: a power supply interface for connecting at least one power supply; an electrical device interface for connecting a corresponding one of the at least two electrical devices; a corresponding protection device electrically connected to the device interface for protecting the corresponding device interface from unexpected overcurrent, wherein each protection device has at least a sensor unit and a switch unit for detecting a current at the corresponding device interface, wherein the switch unit is designed to disable the corresponding device interface based on a determination of an overcurrent; and at least two electrical cables to which a supply voltage is applied, wherein at least one cable electrically couples at least one power supply interface to the protection device. The present invention also relates to a method for electrically coupling at least two electrical devices connected to a power supply network with at least one power source connected to the power supply network using a preset supply voltage, wherein the power supply network is designed as a DC voltage power supply network, wherein at least one power source is connected to a power supply interface of the power supply network, and at least two electrical devices are connected to corresponding electrical device interfaces of the power supply network, and the device interface is protected from unexpected overcurrent by means of a corresponding protective device electrically connected to the device interface by having a sensor unit of a corresponding protective device detect at least one corresponding current and disabling the corresponding device interface by means of a corresponding switching unit based on the determination of an overcurrent, and at least one power supply interface is electrically coupled to the protective device by means of at least one of the at least two electrical cables to which the supply voltage is applied. Background Art

[0002] Such a power supply network and such a method are generally known in the prior art, so that no special documentary proof is required for this. The power supply network and such a method are used to enable the exchange of electrical energy between a power supply and an electrical device, in particular an electrical consumer, so that the normal operation of the electrical device and the power supply connected to the power supply network can be realized. Here, the power supply does not need to operate as an energy source in every operating state, but it can also operate as an electrical consumer or as an electrical device according to the corresponding operating state of the power supply. In addition, this also applies in reverse to the electrical device, which is not forced to operate as an electrical consumer in every operating state, but can also be used as a power source according to the corresponding operating state of the electrical device. However, it is usually proposed that the power supply mainly provides electrical energy via the power supply network, and the electrical device mainly extracts electrical energy from the power supply network in order to realize its normal operation.

[0003] Power supply networks and methods for operating power supply networks are commonly used in the prior art. It is usually proposed that a protective device is provided for at least each electrical device connected to the power supply network to protect the electrical device from being affected by an overcurrent. For this purpose, the current is detected and evaluated at one of the corresponding power supply interfaces by means of a current sensor. In particular, the evaluation includes comparing the detected value of the current with a preset comparison value. If the value of the detected current is greater than the comparison value from the comparison, the current is determined as an overcurrent and a corresponding control signal is sent to a switching unit, by means of which the corresponding electrical device interface can be disabled according to the control signal. As a result, this protection principle can of course also be used for at least one power supply.

[0004] Electrical networks for distributing electrical energy in the prior art can generally have a correspondingly specific topology, in particular different energy distribution levels or supply levels, by which, for example, a tree-like structure can be formed.

[0005] In particular, when electrical devices are connected to the power supply network with different electrical powers, the problem that can arise is that in the case of an overcurrent, in particular a short-circuit current of a short-circuit fault, in the corresponding electrical device, it is not the protective device connected to the electrical device that first disables or disconnects the electrical device in which the overcurrent or short-circuit current occurs, but rather, for example, a protective device arranged adjacently, a superior protective device of a superior supply layer or the like is disabled or disconnected. However, this is undesirable because the normal operation of other electrical devices connected to the power supply network can be disturbed. The principle of first disconnecting the protective device in which the overcurrent occurs is also called selectivity.

[0006] Faults, in particular short circuits in an extended DC voltage supply network as a supply network are undesirable, ie selectivity must be reliably guaranteed. That is, the device interface at which a fault, such as an overcurrent or a short-circuit current, occurs should always be switched off by means of the protective device.

[0007] Many electrical devices, especially in the field of direct current applications, provide a not insignificant amount of capacitance on the device interface side. The capacitance can be realized, for example, by capacitors or the like. If such electrical devices of different power are now connected to a direct voltage supply network, faults, such as short circuits, can occur, resulting in corresponding short-circuit currents in electrical devices with high electrical power.

[0008] Usually, the protective device requires a certain time period to reliably detect a fault or a short circuit and disable the corresponding device interface by means of its switching unit. However, a correspondingly large current flows from the power supply network into the faulty electrical device until the corresponding device interface is switched off by means of the protective device. This current can be associated with adjacently arranged electrical devices due to cable inductances and the like, for example when they provide corresponding capacities on the interface side, if such electrical devices are designed for low electrical powers, it can happen that the capacity of the electrical device provides a corresponding current, which is provided to the faulty or short-circuited protective device via the protective device to which it is connected. In such a case, the principle of selectivity can no longer be guaranteed and the electrical device is switched off by means of the relevant protective device, even though there is no fault, because, for example, the comparison value of the corresponding protective device is smaller than the comparison value of the faulty or short-circuited protective device.

[0009] In power supply networks that apply an AC voltage as the supply voltage, it is known, for example, that the protection devices are coupled to one another via communication cables in a corresponding manner using communication technology. This allows the protection devices to communicate with one another in such a way that the principle of selectivity can be implemented. However, this is relatively complex and is less suitable in particular for the case of a DC voltage as the supply voltage, since short circuits must be disconnected very quickly to ensure selectivity and the requirements for the response speed of the communication are very high. Summary of the invention

[0010] It is therefore an object of the present invention to improve the selectivity in a power supply network, in particular when the power supply network applies a direct voltage as supply voltage.

[0011] It is particularly proposed for such a power supply network that at least two power cables are electrically coupled to a pulse circuit for discharging a predefined charge using at least one capacitor, the pulse circuit being designed to discharge the charge when a voltage disturbance of the supply voltage occurs, wherein the charge is determined at least as a function of an overcurrent and a predefined time period for discharging the charge.

[0012] It is particularly proposed for this method that a pulse circuit is connected to at least two electrical cables for discharging a preset amount of charge using at least one capacitor, wherein the charge is discharged by means of the pulse circuit when a voltage disturbance of the supply voltage occurs, wherein the charge is determined at least as a function of the overcurrent and a preset time period for discharging the charge.

[0013] The idea underlying the invention is that, by means of a pulse circuit, it is possible to deliver a predetermined amount of charge to the power supply network for a predetermined time period or a predeterminable time period on the power supply network side, the amount of charge being dependent in particular on the overcurrent and preferably being available for the predetermined time period. In other words, it is possible to achieve that in the event of a fault or a short circuit in one of the electrical devices, the overcurrent at least does not have to be completely provided by one or more of the other electrical devices, so that reliable disabling of the device interface in question that has failed or short-circuited can be ensured without the need to associate other electrical devices or at least one power supply. In particular, selectivity can be improved thereby and operational readiness of other electrical devices can be likewise reliably ensured.

[0014] The invention thus makes it possible to significantly improve selectivity with relatively little effort. Problems with the prior art arise in that irrelevant electrical devices are undesirably disabled, so that problems can be significantly reduced, in particular but not exclusively in power supply networks operated with direct voltage.

[0015] Preferably, the power interface is designed, for example, in accordance with the power supply to be connected, involving an electromagnetic interface, the number of interface electrodes and / or the like. Thus, the power supply can have at least two interface electrodes, to which a power supply of a corresponding two-pole design can be connected. In addition, the power interface can also be connected to a corresponding protection device, which can advantageously be designed according to the protection device, the protection device being electrically connected to the corresponding device interface. In addition, it can be provided that in a plurality of power supplies, not all power interfaces are required to be connected to the corresponding protection device. This can depend on the respective properties of the power supply network in conjunction with the correspondingly connected power supply. Therefore, the power interface is designed so that it has at least two interface electrodes, so that a correspondingly designed electrical device can be connected thereto.

[0016] Furthermore, the power supply network has at least two electrical cables, by means of which the protection device is electrically coupled to at least one power supply connection. One of the electrical cables can also be formed via a reference potential, such as device ground or the like. Furthermore, it can of course also be provided that one of the cables is looped through the protection device only. The cable can also be connected directly to the device connection next to the protection device. Combinations of such electrical cables can also be provided.

[0017] In particular, the number of cables can depend on which supply voltage is used for distributing the electrical energy. Thus, in the case of two cables, the supply voltage can be a DC voltage. In addition, the power supply network can additionally also include a single-phase or multi-phase AC voltage. Furthermore, it is of course possible to provide cables for distributing the energy according to the number of phases when using a multi-phase AC voltage as the supply voltage. This design can, for example, use a three-phase supply voltage, which therefore uses at least three cables, more precisely at least one cable for each phase. Furthermore, it can be additionally provided that in the case of a three-phase AC voltage as the supply voltage, a fourth cable is provided, to which a zero potential is applied. However, the present invention is not limited to the aforementioned voltage application.

[0018] In addition, a corresponding protective device is provided for at least each of the device interfaces to which the electrical device can be connected, which is used to protect the corresponding device interface from being affected by unexpected overcurrent. For this purpose, the protective device includes a sensor unit, by means of which at least one current at the corresponding device interface can be detected. For this purpose, the sensor unit can include a current sensor, such as a Hall probe, a Rogowski coil, a shunt and / or the like. Preferably, the sensor unit is designed to provide a comparison function, in which the current value detected by means of the sensor unit can be compared with a comparison value. For this comparison, it can be proposed to determine the absolute value, the effective value or the like of the current in advance so that the comparison can be carried out. The control signal is then prepared by the sensor unit based on the comparison.

[0019] In addition, the protection device includes a switching unit, which is designed to disable the corresponding device interface based on the detection of an overcurrent. For this purpose, the switching unit is connected to the sensor unit by means of communication technology and can preferably be controlled in a desired manner by means of a control signal of the sensor unit. If an overcurrent is measured or determined by means of the sensor unit, for example, when the absolute value of the detected current is greater than a comparison value, the switching unit can be controlled by means of a control signal to disable the device interface accordingly. For this purpose, the switching unit can have an electromagnetic switching element, such as a repeater, a protector or the like, so as to be able to provide the desired switching function. In addition, in particular, the switching unit can also have at least one semiconductor switching element, by means of which the desired switching function can be at least partially realized. However, the switching unit is usually not designed to realize a current limiting function, so that undesirable effects of the connected electrical equipment can be avoided as much as possible.

[0020] It is preferred that the semiconductor switching element or the switching element in the disclosure is a controllable electrical switching element, for example a controllable semiconductor switch, such as a transistor operated in switching mode, a thyristor, a combination thereof preferably with a parallel-connected reverse diode, a gate turn-off thyristor (GTO), an insulated gate bipolar transistor (IGBT), a combination thereof or the like. However, it is also advantageous that the switching element is formed by a field effect transistor, in particular a metal oxide semiconductor field effect transistor (MOSFET).

[0021] In order to realize the desired switching function by means of the transistor, it is operated in switching mode. Switching mode in terms of semiconductor switches using transistors means that in the switched-on switching state there is a very low resistance between the interfaces of the transistor forming the switching path, so that a large current can be supplied at a very low residual voltage. In the switched-off switching state, on the other hand, the switching path of the transistor is high-ohmic, i.e. it offers a high resistance, so that even when a high voltage is applied to the path, there is essentially no or only a very low, in particular negligible, current. In contrast, linear mode in transistors is used, which is however usually not used in switching mode.

[0022] The switching element has at least one control interface in order to realize the control function, at which the switching element can be applied with a control signal, so that the desired switching function of the switching element can be realized. The control signal can be a binary switching signal, which can have two state values, so as to provide the desired switching function of the switching element. For example, the switching signal can be formed by a pulse sequence, by means of which it is applied to the control interface. It is first suitable in thyristors and GTOs. In addition, it can be proposed in transistors that the switching signal is a rectangular signal, wherein the corresponding switching state of the switching element can correspond to one of the potentials of the rectangular signal. Such a signal is advantageous for transistors, in particular bipolar transistors, field effect transistors or the like.

[0023] According to the invention, a pulse circuit for discharging a preset charge quantity is connected to at least two electrical cables. The pulse circuit is used to discharge a preset charge quantity when a voltage disturbance of the supply voltage occurs. Usually, such a voltage disturbance occurs when a fault, especially a short circuit, occurs on the connected electrical device, which leads to a particularly large current demand at the corresponding device interface. This current demand, also called overcurrent, is outside the normal operation of the electrical device and the power supply network and therefore represents an unexpected overcurrent. Because the electrical cable usually provides at least an inductive characteristic, it can especially cause in a spatially distributed power supply network: the voltage disturbance can have a great influence on the electrical devices connected directly adjacent to each other in space due to the unexpected overcurrent. What can now be achieved by the pulse circuit is that the preset or preset charge quantity is discharged, so that this influence of the unexpected overcurrent can be reduced or limited to the electrical devices arranged adjacent to each other in particular in space. It can be achieved that the undesired disabling of electrical devices without faults can be better avoided. Therefore, the selectivity can be significantly improved by the pulse circuit. Preferably, the pulse circuit is coupled to the electrical cable, so that the conventional function can be provided without depending on the operating state of the protection device. Particularly preferably, the pulse circuit is not connected on the load side.

[0024] In order to be able to provide the charge, the pulse circuit has at least one capacitor. Of course, the pulse circuit can also have a plurality of capacitors, which are moreover connected to different positions of the electrical cable. Thus, the pulse circuit can in this case be designed to be distributed, for example via the power supply network. Therefore, the pulse circuit does not need to have only one single capacitor. In addition, this design allows that the individual capacitors can be designed to be small in terms of their capacitance value.

[0025] For the design of the capacitance of the at least one capacitor, it can be taken into account that the at least two cables provide a predetermined cable inductance in the event of an unexpected overcurrent, which can be at least partially compensated by means of the pulse circuit. In addition, the capacitance value of the at least one capacitor is also selected at least partially as a function of how large the unexpected overcurrent can be and for which predetermined time period this function of the pulse circuit is necessary. This allows the determination of a predetermined or predeterminable charge amount, which can then be used to determine the capacitance value of the at least one capacitor taking into account the supply voltage. Of course, empirical studies can also be considered in addition here in order to be able to better take into account the special characteristics of the power supply network.

[0026] An overcurrent is a current at the device interface of the corresponding protective device, which is greater than the comparison value of the corresponding protective device. The overcurrent is therefore dependent on the respectively set comparison value of the protective device. Thus, the predeterminable charge amount can be determined, for example, based on the minimum overcurrent that occurs. However, the charge amount can also be determined as a minimum value for the overcurrent based on a greater value of the overcurrent, in order to influence the triggering reliability, etc. It can be taken into account here how large the overcurrent at the corresponding device interface can become. Thus, an overcurrent is a current detected by means of a sensor, whose value is greater than the comparison value.

[0027] Furthermore, one or more triggering characteristic curves of the protective device, in particular the switching unit, can also be taken into account. Thus, the triggering speed of the protective device, in particular the switching unit, can depend, for example, on the magnitude of the overcurrent value. For example, the triggering speed in the case of a larger overcurrent value can be lower than the triggering speed in the case of a smaller overcurrent value.

[0028] The predeterminable time period can be determined, for example, based on such a triggering behavior or such a triggering characteristic. It can thereby be achieved that the charge quantity can preferably be discharged in the predeterminable time period, so that the reliability can be improved at least in terms of selectivity. The predeterminable time period can, for example, extend from about 0.0001 s to about 0.1 s, preferably from about 0.001 s to about 0.01 s. In particular, the predeterminable charge quantity can be determined taking into account the predeterminable time period and the overcurrent. The capacity of the at least one capacitor can thereby subsequently be determined.

[0029] Thus, the predeterminable charge amount and / or the predeterminable time period can be selected or predetermined for a specific adaptation to the triggering characteristics of at least one of the protective devices. If there are a plurality of pulse circuits corresponding to the respective protective devices, the respective predeterminable time period and / or charge amount can be at least partially adapted to the respectively corresponding protective device. The pulse circuit can thus be designed to be adapted to the respective special requirements. Thus, just as the protective devices can have different triggering properties or triggering characteristics, the pulse circuits can also have different predeterminable time periods and / or charge amounts.

[0030] The pulse circuit preferably automatically supplies the charge when a voltage disturbance of the power supply network occurs. This advantageously requires no additional effort in order to discharge or supply the charge in the desired manner.

[0031] The power supply network is designed as a DC voltage power supply network. The invention is particularly suitable for DC voltage power supply networks, since it can achieve a significant improvement in selectivity with respect to reliable functionality at a low cost. The invention is therefore applicable in principle to power supply networks which use at least a DC voltage for their supply voltage or, in addition to a DC voltage, also an AC voltage.

[0032] It is also preferred that the pre-settable or pre-set time period can be determined as a function of how the protective device reacts to an unexpected overcurrent, for example which trigger characteristic it uses for deactivation in the event of an unexpected overcurrent. This need not be the same for all protective devices. For example, it is also possible to introduce trigger characteristics that are not optimal for the determination of the time period. Furthermore, in pulse circuits arranged via a spatial extension of the power supply network, it can be provided that the time period is determined as a function of the corresponding position in the power supply network. For this purpose, special characteristics of the power supply network and of the electrical devices and / or power sources connected thereto can be taken into account.

[0033] The switching element is connected in series with at least one capacitor, and the switching element is preferably designed as a semiconductor switching element. This makes it possible to provide a charge in the manner according to the invention, but at the same time reduce the influence of the at least one capacitor and the pulse circuit on the power supply network as a whole.

[0034] Preferably, the time period is determined as a function of at least one characteristic property of at least one of the protection devices. The characteristic property can be, for example, a trigger current, a trigger characteristic and / or the like. The trigger current can be determined, for example, as a function of a comparison value. Furthermore, the cable inductance can be taken into account in order to determine the time period. Overall, the power supply network can thereby be further improved.

[0035] Furthermore, it is proposed that in the case of protective devices designed for unexpected overcurrents of different sizes, the charge quantity is determined at least as a function of the maximum overcurrent. This ensures that selectivity is also ensured in the case of protective devices that permit particularly large unexpected overcurrents.

[0036] Preferably, the switching element comprises a first diode or consists of a first diode. This design is particularly suitable for power supply networks whose supply voltage is a DC voltage. This allows a normal discharge of the charge without requiring additional control overhead when the switching element only comprises the first diode. At the same time, the effect of the capacitor or the pulse circuit can be reduced during normal operation, that is, when no unexpected overcurrent occurs. The diode is selected accordingly with reference to its voltage stability and its limiting load integral. If the pulse circuit is a pulse circuit with a plurality of capacitors, it can be proposed that each of the capacitors is connected to the electrical cable by means of a respective diode.

[0037] Alternatively or additionally, it can also be provided that the switching element is designed to be controllable by means of a control signal. In this design, a voltage sensor can be designed, by means of which a voltage disturbance can be detected. Based on the detection of the voltage disturbance, the switching element is switched to the switched state, so that the pulse circuit can provide the desired amount of charge. Of course, in particular in pulse circuits designed for distribution via a power supply network, this design can also be combined with a diode as a switching element. Preferably, the switching element can be a semiconductor switching element such as a transistor, a thyristor or the like.

[0038] In particular, it can be provided that the power supply network has a control unit coupled to the sensor unit in a signaling manner for providing a control signal for the switching element of the pulse circuit. This makes it possible to detect and evaluate the corresponding current, preferably depending on the function of the protective device, and to generate a control signal for the switching element of the pulse circuit. This makes it possible to further improve the functionality. In particular, this embodiment is suitable for applications in which the supply voltage is set to an AC voltage by means of a controllable switching element.

[0039] An improved solution proposes that the pulse circuit is designed to be at least partially integrated with at least one of the protection devices. The pulse circuit can be arranged, for example, at least partially in the housing of at least one of the protection devices. It can also be proposed that the pulse circuit is integrated in a plurality of, in particular all, protection devices. Preferably, the pulse circuit is connected in the protection device so that the current provided by it, if possible, or the charge discharged by it can be discharged to at least two electrical cables to which the supply voltage is applied, without the need for the sensor unit to detect it. Therefore, the sensor unit detects the charge only when the overcurrent involves a device directly connected to the device interface. In addition, preferably, the pulse circuit is connected in the protection device so that the current provided by it, if possible, can be discharged at the corresponding device interface of the protection device, which can be detected by the sensor unit. Preferably, the pulse circuit is connected in the protection device so that the function of the pulse circuit can be provided basically independently of the switching state of the switch unit of the protection device. Therefore, the discharge of the charge to the electrical cable is preferably achieved.

[0040] For example, it can be proposed that at least one capacitor is integrated into the protection device so that the amount of charge that is discharged or can be discharged can be provided directly within the scope of the protection device in the event of an unexpected overcurrent. This can particularly advantageously reduce the impact on the power supply network and other electrical devices. At the same time, this design can achieve that the pulse circuit is integrated into the power supply network in a simple manner and that the corresponding functionality is automatically provided with the supply of the power supply network. In this design, it is no longer required to set up a separate pulse circuit. However, of course, a separate pulse circuit can also be provided in addition. The pulse circuit can of course also be designed to be integrated into multiple of the protection devices. In addition, each of the protection devices can include its own pulse circuit. It can be individually designed to match the corresponding protection device.

[0041] It is further proposed that the pulse circuit has a series circuit connected in parallel with the first diode, the series circuit consisting of a second diode connected in reverse to the first diode and a resistor, in particular a varistor. The first diode enables the pulse circuit to discharge a predetermined charge in a conventional manner. The second diode is used to enable the capacitor to be charged via a resistor or a varistor. If a varistor is provided, a voltage limiting function can thereby also be implemented simultaneously by the pulse circuit. By means of the reverse connection of the diode, the diode thus determines the relative current direction on the capacitor side and therefore also on the pulse circuit side.

[0042] It is further proposed that the switching unit has a semiconductor switching element and that the pulse circuit has a third diode connected to the second diode, so that the second diode and the third diode are connected in anti-series connection and their intermediate connection is connected to the capacitor via a resistor, in particular a varistor, wherein the anti-series connected diodes are connected in parallel with the semiconductor switching element. In this case, the varistor is thus used not only for voltage limitation but also for charging at least one capacitor. Finally, this development also makes it possible to charge the capacitor on the device connection side when the switching unit is in the off state and an electrical device connected thereto provides a voltage, for example a supply voltage or the like.

[0043] The advantages and effects given for the power supply network according to the invention are of course also suitable for the method according to the invention, and vice versa. Therefore, device features can of course also be expressed as method features, and vice versa. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Further advantages and features emerge from the following description of exemplary embodiments with reference to the drawings. In the figures, identical features and functions are denoted by identical reference numerals.

[0045] The accompanying drawings show:

[0046] Figure 1A schematic block diagram of a circuit diagram of a DC voltage supply network having two supply levels, to which a common supply network is connected as a power source and to which electrical devices are connected in series as energy consumers;

[0047] Figure 2 Shown for use according to Figure 1 Schematic diagram of the circuit of the protection equipment of the power supply network;

[0048] Figure 3 Shown Figure 1 A schematic block circuit diagram in which the current flow in the event of a short circuit at one of the connected electrical devices is shown by means of energy flow arrows;

[0049] Figure 4 Shown Figure 1 Such a circuit diagram, in which a pulse circuit is supplementarily connected;

[0050] Figure 5 A circuit schematic diagram showing a protection device with an integrated pulse circuit; and

[0051] Figure 6 Shown based on Figure 5 Circuit diagram of an integrated pulse circuit protection device. DETAILED DESCRIPTION

[0052] Figure 1 The schematic block diagram of a DC voltage supply network 10 is shown, by means of which electrical devices 12 to 24 connected to the supply network are electrically coupled to a power source 26 connected to the DC voltage supply network 10. In the present case, the power source 26 is formed by a common supply network 62, which provides a three-phase AC voltage of approximately 400 V. In addition, the three-phase AC voltage is provided by a protective device 64, which is connected on its side to a rectifier 66, which rectifies the three-phase AC voltage in a predetermined manner and provides a corresponding DC voltage 28 as a supply voltage at a capacitor 68. The power source 26 is connected to a power supply interface 32 of the DC voltage supply network 10.

[0053] The DC voltage supply network 10 has a first supply level 70 and a second supply level 72, which are electrically coupled to one another via a protection device 74. Connected to the first supply level 70 is also a protection device 34, which provides a power supply connection 32, to which the power supply 26 is connected.

[0054] The supply layers 70, 72 each include two electrical cables 38, 40, which in the coupled state are supplied with a DC voltage 28 provided by the capacitor 68 via a protective device 74. A protective device 34 is connected to the first supply layer 70 by way of example only, which provides a corresponding device interface 30. The heating element 20, the converter 22 and the converter 24 are connected to the protective device 34. The corresponding motors (not further labeled) are connected to the converters 22, 24. However, the first supply layer 70 can also include further protective devices 34 with further electrical devices.

[0055] In the present case, four protective devices 34 are connected to a second supply level 72, which is advantageously designed similarly to the first supply level 70. The two converters 12, 14, the lighting device 16 and the heating element 18 are connected to these protective devices. The second supply level 72 can also include further protective devices 34 with further electrical devices connected thereto. The corresponding unmarked motors are connected to the converters 12, 14.

[0056] The protection device 34 and the protection device 74 are used to protect the corresponding device interface 30 or power interface 32 from being affected by unexpected overcurrent. For this purpose, each of the protection devices 34 and 74 includes a sensor unit 50 for detecting the current at the corresponding device interface 30 or power interface 32.

[0057] Furthermore, each of the protection devices 34 includes a switching unit 48 ( Figure 2 ), the switch unit is designed to disable the corresponding device interface 38 or power supply interface 32 according to the determination of overcurrent. For this purpose, the sensor unit 50 is designed to compare the detected current with a comparison value and send a control signal to the switch unit 48 when the absolute value of the current exceeds the comparison value, so that it disables the corresponding device interface 30 or power supply interface 32.

[0058] The protective devices 34 are electrically coupled to one another and to the power supply connection 32 by means of electrical cables 38 , 40 . The first supply level 70 is coupled to the second supply level 72 via the protective device 74 .

[0059] A respective capacitor 76 is provided at each of the converters 12 , 14 , 22 , 24 , which capacitor 76 is electrically coupled to the respective electrical cable 38 , 40 via the respective device interface 30 .

[0060] Figure 2 1 shows a circuit diagram of a protection device 34. It can be seen that the protection device 34 provides a device interface 30 for connecting a corresponding electrical device. A cable interface 80 is provided in contrast, by means of which the protection device 34 can be connected to electrical cables 38, 40. A switch unit 48 is designed between the cable interface 80 and the device interface 30, by means of which the device interface 30 can be disabled.

[0061] The switching unit 48 has an electromagnetic switching element 82, which can be actuated by means of a control signal, not shown in detail, in a manner not described in further detail. In addition, two transistors T1, T2 connected in series in reverse are connected in series with the electromagnetic switching element 82 in series with a reverse diode, not shown. The semiconductor switching element 84 can be controlled in terms of signal states by means of a further control signal. In the present case, the transistors T1, T2 are composed of IGBTs. However, in an alternative embodiment as transistors, field effect transistors, in particular MOSFETs or the like can also be used.

[0062] Furthermore, the protective device 34 includes a current sensor 50, by means of which the current of the connected electrical device can be detected. Furthermore, the electrical sensor 50 has an evaluation circuit (not shown) which compares the detected value of the current, more precisely the detected absolute value of the current, with a comparison value. If the absolute value of the detected current is greater than the comparison value, the switch unit 48 is placed in the open switching state by means of a control signal, so that the device interface 30 is disabled.

[0063] Figure 1 It is shown that a short circuit 78 has occurred in the converter 14. This has the result that a very high current is briefly required from the DC supply voltage 10, which also flows through the corresponding protective device 34. The switching device 34 detects the overcurrent and switches the switching unit 48 to the open switching state, thereby disabling the corresponding corresponding device interface 30.

[0064] However, due to the short circuit 78, the current detected accordingly becomes very large until the disconnection takes effect, which can cause problems with selectivity as explained below.

[0065] In the present case, the converter 14 is designed for a greater electrical power than the converter 12 , and the protective device 34 associated with the respective device interface 30 is correspondingly adjusted to match the respective power of the converters 12 , 14 .

[0066] As a result of the short circuit 78 , it can occur that a very large current is briefly drawn from the capacitor 76 and also from the capacitor 68 , which current is supplied to the short circuit 78 . Figure 3 picture Figure 1 The current course in the DC voltage supply network 10 is likewise shown by the corresponding current arrows 86. This can now result in the protective device 34 connected to the converter 12 being acted upon with such a high current that its switching unit 48 is also switched to the open switching state, whereby the corresponding device interface 30 is then also disabled, although there is no fault in the electrical device. Advantageously, the same situation can also be provided for the other protective devices 34 connected to the converters 22, 24, which also involve the power supply 26. This is an undesirable effect that impairs the selectivity principle.

[0067] Now, Figure 4 Shows an image Figure 1 The circuit diagram of such a feasible solution reduces or even completely avoids the aforementioned problems. Figure 4 It is provided that a pulse circuit 43 , which in the present case has a series circuit consisting of a capacitor 44 and a diode 36 , is connected to the electrical cables 38 , 40 , in this case at the second supply level 72 .

[0068] The series connection and polarity of the diode 36 are selected so that, in the event of a voltage disturbance in the supply voltage 28, a charge is automatically provided on the cables 38, 40 for a preset period of time, thereby generating an additional current which is provided to the short circuit 78. This makes it possible to reduce or even almost avoid the use of the capacitor 76. Figure 3 The current arrow 86 of the current shown and the current required from the capacitor 68, so that in this embodiment only the protective device of the converter 14 is triggered, in which a short circuit 78 also occurs. In this case, the other protective device 34 is not required or does not participate in the operation. As a result, the connected devices are also not impaired in terms of their normal function.

[0069] Even in Figure 4 Although only a single pulse circuit 42 is shown in the figure, it can also be provided in an alternative solution, for example, at least one separate pulse circuit 42 is provided for each supply layer 70, 72. Of course, it can also be provided for the supply layers 70, 72 to provide more than one separate pulse circuit 42. It can be provided particularly advantageously that a pulse circuit 42 is provided for each of the protective devices 34, which is preferably directly connected to the corresponding protective device 34. This makes it possible to achieve particularly good functionality in terms of selectivity.

[0070] according to Figure 5 A further improvement is shown, which shows a circuit diagram of a protection device 34. The protection device 34 is advantageously based on the Figure 2 The description supplements the protection device 34 of the relevant embodiment. Figure 2 Supplement of protective equipment 34, according to Figure 5 The protective device 34 comprises an integrated pulse circuit 42. The series circuit consisting of the capacitor 44 and the diode 36 is connected between the electromagnetic switching element 82 and the semiconductor switching element 84 on the one hand and to the reference potential interface 88 implemented on the other hand. The function of the pulse circuit 42 corresponds to that already described according to Figure 4 In an alternative embodiment, the reference potential connection 88 does not need to be implemented by the protective device 34 . It can also be connected directly to the device connection 30 while bypassing the protective device 34 .

[0071] In addition, according to Figure 5 The pulse circuit 42 comprises a resistor 46 which is connected in parallel with the diode 36. The capacitor 44 can be loaded via the resistor 46 so that it can provide the desired amount of charge.

[0072] In the present case, the capacity of the capacitor 44 is also determined as a function of which charge quantity should be provided for which time period so that the corresponding protective device 34 can be triggered reliably without affecting other adjacent protective devices 34. For this purpose, the triggering characteristics of the protective device 34 can also be taken into account. In this case, the cable inductances L1, L2 of the DC voltage supply network 10 can also be taken into account.

[0073] This embodiment has the advantage, among other things, that the DC voltage supply network 10 can be designed and expanded in any desired manner, wherein the desired functions can also be implemented selectively by means of the provided protection device 34, without the need to connect separate supplementary components, such as separate pulse circuits 42, to the electrical cables 38, 40. Likewise, it is of course also possible to provide additional pulse circuits 42 in a supplementary manner.

[0074] Figure 6 Shown according to Figure 5 An improved solution of the protection device 34 of the present invention can also realize overload voltage protection. For this purpose, the diodes 52 and 54 connected in reverse series are connected in parallel with the semiconductor switch 84, and the intermediate interface thereof is connected to the capacitor 44 via the varistor 56. The capacitor 44 can also be charged to its preset voltage via the varistor 56, so that it can provide the desired amount of charge. In addition, the design solution can intercept the voltage pulse whose amplitude exceeds the preset value, and partially store its energy in the capacitor 44 and / or partially convert it into heat by means of the varistor 56.

[0075] In addition, according to Figure 6 The protective device 34 comprises a series circuit consisting of a further electromagnetic switching element 58 and a further resistor 60, by means of which an electrical connection can be established between the cable interface 80 and the device interface 30. This allows a possible precharging of the capacitor 76, so that large current pulses can be avoided or reduced when the switched-mode power supply 48 is switched on.

[0076] Capacitor 44 should preferably have a low self-inductance, for example be designed as a film capacitor or the like. Diode 36 should for this purpose be designed to be able to conduct large current pulses, ie therefore have a large limiting load integral.

[0077] When the pulse circuit 42 is integrated into the protection device 34 , it is possible to also detect faults in the pulse circuit 42 , such as a defective diode 36 or a defective capacitor 44 , for example by detecting a capacitor voltage of the capacitor 44 .

[0078] What is made possible by the invention is that the overcurrent caused by the short circuit 78 can be supplied from a separate source, namely the capacitor 44, which does not need to be protected via a protective switch or the like. In the event that the capacitor 44 has a fault, such as a short circuit or the like, this can be absorbed by the diode 36, which in this case provides a blocking effect. As a result, the damaged capacitor 44 is disconnected from the DC voltage supply network 10 and cannot be negatively influenced. In order to also absorb the case of a damaged diode, two diodes can be connected in series.

[0079] The invention is particularly suitable for use with semiconductor switching devices. It can be achieved that the predeterminable time period is significantly less than 1 ms. The time period can preferably be, for example, approximately 100 μs or even less.

[0080] Furthermore, the invention is of course also particularly suitable for spatially extending the DC voltage supply network 10. It can therefore be provided that a plurality of pulse circuits 42 are connected to the electrical cables 38, 40 at a predetermined distance, for example at a distance of less than approximately 100 m, preferably approximately 50 m or less. If the cable inductance of the cables 38, 40 is low, the distance between the protective device 34 and the pulse circuit 42 should be as small as possible, for example less than approximately 10 m or the like. The cable inductance is Figure 6 Marked with L1 and L2.

[0081] The examples are only for illustrating the present invention and should not be limited thereto.

[0082] Furthermore, the present invention is not limited to the use of power supply networks using DC voltages. It can of course also be used in power supply networks using AC voltages as supply voltages. The AC voltage can be a single-phase or multi-phase, in particular a three-phase AC voltage.

Claims

1. A power supply network (10) for electrically coupling at least two electrical devices connected to the power supply network (10) with at least one power source (26) connected to the power supply network (10) using a predeterminable supply voltage, wherein: The power supply network (10) is designed as a DC voltage power supply network, and the power supply network has: - a power supply interface (32) for connecting at least one of the power supplies (26), - an electrical device interface (30) for connecting a respective one of at least two of the electrical devices, - a respective protective device (34) which is electrically connected to the device interface (30) and is used to protect the respective device interface (30) from an unexpected overcurrent, wherein each protective device (34) has at least a sensor unit (50) for detecting a current at the respective device interface (30) and a switch unit (48), wherein the switch unit (48) is designed to disable the respective device interface (30) as a function of the detection of the overcurrent, and at least two electrical cables (38, 40), to which the supply voltage is applied, at least one of the electrical cables electrically coupling at least one of the power supply connections (32) to the protection device (34), wherein at least two of the electrical cables (38, 40) are electrically coupled to a pulse circuit (42) for discharging a predeterminable charge quantity using at least one capacitor (44), the pulse circuit being designed to discharge the charge quantity when a voltage disturbance of the supply voltage occurs, wherein the charge quantity is determined at least as a function of the overcurrent and a predeterminable time period for discharging the charge quantity, It is characterized in that A switching element is connected in series with at least one of the capacitors (44), and the switching element is designed as a semiconductor switching element.

2. The power supply network according to claim 1, characterized in that: The time period is determined as a function of at least one characteristic property of at least one of the protection devices (34).

3. The power supply network according to claim 1 or 2, characterized in that: In the case of a protection device (34) designed for unexpected overcurrents of different sizes, the charge amount is determined at least according to a maximum overcurrent among the overcurrents.

4. The power supply network according to claim 1, characterized in that: The switching element comprises a first diode (36) or consists of a first diode (36).

5. The power supply network according to claim 1 or 2, characterized in that: The switching element is designed to be controllable by means of a control signal.

6. The power supply network according to claim 1 or 2, characterized in that: A control unit is provided which is coupled to the sensor unit (50) in terms of signal technology and is used to provide a control signal for the switching element.

7. The power supply network according to claim 1 or 2, characterized in that: The pulse circuit (42) has a charging unit for charging the capacitor (44) with the presettable charge amount.

8. The power supply network according to claim 1 or 2, characterized in that: The pulse circuit (42) is designed to be at least partially integrated with at least one of the protection devices (34).

9. The power supply network according to claim 4, characterized in that: The pulse circuit (42) has a series circuit connected in parallel with the first diode (36), the series circuit consisting of a second diode (52) connected in reverse to the first diode (36) and a resistor.

10. The power supply network according to claim 9, characterized in that: The resistor is a varistor (56).

11. The power supply network according to claim 9 or 10, characterized in that: The switch unit (48) has a semiconductor switch element (84), and the pulse circuit (42) has a third diode (54) connected to the second diode (52), so that the second diode and the third diode are connected in reverse series, and an intermediate interface of the second diode and the third diode is connected to the capacitor (44) via the resistor, wherein the diodes connected in reverse series are connected in parallel with the semiconductor switch element (84).

12. A method for electrically coupling at least two electrical devices connected to a power supply network (10) to at least one power source (26) connected to the power supply network (10) using a predetermined supply voltage, wherein: The power supply network (10) is designed as a DC voltage power supply network, wherein: - a power supply interface (32) for connecting at least one of the power supplies (26) to the power supply network (10), - a corresponding electrical device interface (30) for connecting at least two of the electrical devices to the power supply network (10), - protecting the device interface (30) from an unexpected overcurrent by means of a corresponding protective device (34) electrically connected to the device interface (30), by having a sensor unit (50) of the corresponding protective device (34) detect at least one corresponding current and disabling the corresponding device interface (30) by means of a corresponding switching unit (48) in response to the determination of an overcurrent, and, - electrically coupling at least one of the power supply connections (32) to the protective device (34) by means of at least one of the at least two electrical cables (38, 40) to which the supply voltage is applied, wherein a pulse circuit (42) is connected to at least two of the electrical cables (38, 40) for discharging a predetermined amount of charge using at least one capacitor (44), wherein the charge is discharged by means of the pulse circuit (42) when a voltage disturbance of the supply voltage occurs, wherein the charge is determined at least as a function of the overcurrent and a predetermined time period for discharging the charge, It is characterized in that A switching element is connected in series with at least one of the capacitors (44), and the switching element is designed as a semiconductor switching element.

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