Filter device

Abstract

The invention relates to a filter device (1) for an inverter (24) at an alternating voltage network (27), having an inductor unit (2), a capacitor unit (3) and a means (41) for reducing the saturation of the inductor unit (2). The invention also relates to an inverter (24) with a filter device (1) and a method (38) for operating a filter device (1).

Description

Technical Field

[0001] The present invention relates to a filter device for an inverter at an AC voltage network, which has a choke coil unit and a capacitor unit. Background Technology

[0002] Drive and automation technologies, as well as electrical equipment in energy supply systems, can generate line-dependent and / or field-dependent electrical interference during operation. To reduce such interference emissions, common-mode chokes are typically used in conjunction with capacitor cells for corresponding filters to reduce or avoid common-mode current.

[0003] Common-mode current is the current in each phase of a wire. Unlike differential-mode current, they have the same sign in terms of current direction.

[0004] Conversely, differential-mode currents add up to zero in their current-direction relationship, especially in the absence of a fault; their total current is zero, meaning the amount of current flowing from the phase of the wire to the power consumer is equal to the amount of current returning from the phase of the power consumer. This also applies particularly well when a neutral conductor is used. The resulting interference variable is also known as symmetrical interference or differential-mode interference.

[0005] Since the common-mode currents flowing to the power consumers have the same current direction, their return currents reach the energy generator through electrostatic capacitance, especially through line capacitance, through the grounding components of the electrical equipment, or through surrounding grounding.

[0006] Interference caused by common-mode current is also called asymmetric interference or common-mode interference.

[0007] For example, common-mode interference is caused by spark interference from brushed motors, through the motor's switching power supply and frequency converter. Significant electrical losses or loads can occur in electrical equipment, in the wires connected to it, and ultimately in the energy distribution system (network, transformer) and energy generator (generator).

[0008] For common-mode filters, current-compensated chokes with choke cores are often used as common-mode chokes; for example, the corresponding coils around a common choke core have the same number of coils per phase.

[0009] Furthermore, the common-mode filter, as a capacitor unit, has a so-called Y-configured capacitor (Y capacitor unit), which is connected to the ground potential by means of a protective conductor (PE).

[0010] This common-mode filter, with its very low impedance connection of Y capacitor cells connected to ground potential via a protective conductor, is particularly suitable for dissipating common-mode currents (interference variables) in TT networks (Terre Terre in French) or TN networks (Terre Neutre in French) with star contacts on the generator side of the network grounded to ground potential when operating electrical equipment (such as inverters).

[0011] These networks have at least one of the following designs or connections for a network star connection to the ground potential, according to which the protective conductor of the electrical line is connected separately, by means of a neutral conductor (N) and at least a portion of the protective conductor, or the neutral conductor of the electrical line is connected separately to a grid star connection grounded at the generator side of the corresponding grid (power source).

[0012] However, Y-capacitor cells with common-mode filters and common-mode chokes, connected to ground potential via protective conductors, used in electrical equipment (e.g., inverters), cannot operate on, for example, IT (Isole Terre) networks used for monitoring electrical faults. These networks are designed to be ungrounded, i.e., insulated from ground potential, particularly on the generator side (power supply). Here, in fault-free operation, leakage current is not permitted, or only very low leakage current is allowed, especially via the Y-capacitor cells and protective conductors to ground potential.

[0013] If electrical equipment such as converters are operating on a TT or TN network, where, unlike the star connection of the grounding network, the outer conductor (i.e., the phase of the TT or TN network) is connected to the ground potential on the generator side (power supply), leakage current may be not allowed or only very low leakage current may be allowed for certain operating conditions, especially through the Y capacitor cell and the protective conductor to the ground potential.

[0014] Therefore, as a precaution, it is common practice to operate such electrical equipment in ungrounded IT networks or TN and TT networks with grounded external conductors by means of an upstream isolation transformer, where the isolation transformer must have a grounded network star connection on the secondary side, and is very expensive and space-consuming.

[0015] It is also possible to remove the Y capacitor unit at the corresponding electrical equipment or disconnect it from the protective conductor of the ground, thereby breaking the ground potential. However, this is usually only feasible when a current-compensating choke is not used in the filter of the electrical equipment.

[0016] Isolating the Y capacitor cell from the grounded protective conductor can prevent or at least reduce leakage current and lower the voltage load on the capacitor. However, this also allows the current-compensating choke to periodically saturate because the common-mode current discharge path for common-mode interference becomes ineffective at that point due to the isolation of the Y capacitor cell. This can cause the choke core of the current-compensating choke to overheat and potentially damage the common-mode choke.

[0017] Of course, it is also possible to design a current compensation choke that is too large. When the connection between the Y capacitor unit and the grounded protective conductor is broken, it is equipped for all possible use cases. This approach leads to high cost and large installation space usage in an inefficient manner.

[0018] EP 2 048 771 A1 discloses a filter device for a drive connected between the rectifier module of a frequency converter and an AC power network. The filter device includes an electromagnetic compatibility filter (EMC filter) with a common-mode inductance, having a winding in each phase of the power network, wherein the windings are magnetically coupled to each other. Saturation of the common-mode inductance of the EMC filter should be avoided within the sampling frequency range of the drive and the resonant frequency range of the EMC filter.

[0019] WO 2017 / 127856A1 illustrates a circuit arrangement for a frequency converter, including a passive network-side EMC filter and an active filter. The passive network-side EMC filter has a capacitor arrangement consisting of three capacitors connected to the respective phases of the network, forming a star connection. The star connection can be electrically connected to ground potential via a switch through another capacitor. Summary of the Invention

[0020] Therefore, the purpose of this invention is to provide a high-efficiency filter device with a common-mode choke and a capacitor unit, which is suitable for networks with grounded star contacts, networks with grounded external conductors, or ungrounded networks, without allowing heating of the common-mode choke.

[0021] To achieve this objective, a filter device for an inverter at an AC voltage network is proposed, which has a choke coil unit, a capacitor unit, and components for reducing the saturation of the choke coil unit.

[0022] The components used to reduce the saturation of the choke coil unit advantageously prevent the common-mode inductor from being heated in an unacceptable manner. Filter devices with choke coil units can therefore be used together with capacitor units as common-mode chokes, for example, in inverters at networks with different grounding concepts.

[0023] In a first advantageous design, the filter device is configured for the inverter to operate on a network with a grounded outer conductor designed as an AC voltage network or on an ungrounded network designed as an AC voltage network, wherein components for reducing saturation can be activated and capacitor units can be isolated from the grounded protective conductor.

[0024] An AC voltage network having a grounded external conductor is advantageously understood, especially as a TT network or a TN network, wherein only one external conductor is connected to the ground potential at the generator side of the respective network, and an ungrounded network designed as an AC voltage network is advantageously understood, especially as an IT network, wherein the electrical phase is electrically isolated from the ground potential, particularly at the generator side of the network.

[0025] In order to operate filter devices on networks with grounded external conductors or on ungrounded networks, it is advantageous to forgo isolation transformers.

[0026] Therefore, in this first operation, it is advantageous to activate the component for reducing saturation, so that the unacceptable heating of the choke unit, which can operate as a common-mode choke, can be reduced by saturation reduction for as many electrical states as possible during the first operation. In this first operation, the capacitor unit can be isolated from the grounded protective conductor, which preferably supports the prevention of unacceptable heating of the common-mode choke.

[0027] In another advantageous design of the filter device, the filter device is designed for secondary operation of the inverter at a network with a grounded network star connection designed as an AC voltage network, wherein the capacitor unit can be connected to a grounded protective conductor for current draw and can be shut off to reduce saturation.

[0028] An AC voltage network having a grounded network star connection is advantageously understood as, in particular, a TT network or a TN network, wherein the network star connection constructed on the generator side of the respective network is connected to the ground potential.

[0029] Therefore, in this second operation, it is advantageous to connect the capacitor cell to a grounded protective conductor so that current that can be generated as a common-mode current can be drawn out. The components used to reduce saturation can preferably be turned off in the second operation, which effectively supports the current drawing out of the common-mode current.

[0030] In another advantageous design of the filter device, the choke unit includes a first coil in a first AC voltage phase of a first AC voltage conductor, a second coil in a second AC voltage phase, and a third coil in a third AC voltage phase. The component for reducing saturation has a fourth coil of the choke unit, the choke unit having a common choke core formed at the first, second, third, and fourth coils, and the component for reducing saturation has a first contact unit for disconnecting and connecting the circuit at the fourth coil.

[0031] The fourth coil at the common choke core of the choke unit (which can operate as a common-mode choke, particularly as a current-compensating choke) and the circuit shorted via the first contact unit at the fourth coil can advantageously prevent unacceptable heating of the common choke core. The common-mode current generated as current during the first operation can be neutralized at the common-mode choke, preventing the common-mode choke core from being driven to saturation in an unacceptable manner (e.g., periodically). Current extraction of the common-mode current through the capacitor unit to the grounding conductor is not necessary to prevent saturation of the common choke core.

[0032] This is advantageously applicable to the use of filter devices in networks with grounded external conductors designed as AC voltage networks or in ungrounded networks designed as AC voltage networks.

[0033] In another advantageous design of the filter device, the capacitor unit includes a first, second, and third capacitor, which is connected to a first AC voltage of a first AC voltage conductor, a second capacitor is connected to a second AC voltage of the first AC voltage conductor, and a third capacitor is connected to a third AC voltage of the first AC voltage conductor, and the capacitors are configured as capacitor star contacts.

[0034] In another advantageous design of the filter device, the second contact unit is designed to disconnect and connect the capacitor unit to the grounded protective conductor, and wherein the capacitor of the capacitor unit is electrically connected to the grounded protective conductor through the capacitor star contact and the second contact unit.

[0035] The common-mode current that can be generated as current during the second operation can be advantageously led from the capacitor cell to the grounded protective conductor via the second contact unit.

[0036] In another advantageous design of the filter device, at least one contact unit has an electromechanical connector or a semiconductor switch.

[0037] In a simple form, electromechanical connectors can be advantageously designed as, for example, threaded connections and as electrical switches.

[0038] In another advantageous design of the filter device, at least one contact unit is designed as a driveable switch.

[0039] A controllable switch can be designed as, for example, an IGBT or a MOSFET, or it can be designed as a relay or a contactor.

[0040] In another advantageous design of the filter device, at least one of the contact units can be driven by a drive signal from the control unit.

[0041] The control unit can be included by the filter device, but it can also be included, for example, by the control unit of the inverter.

[0042] It can also be designed as a control unit, such as a superimposed drive controller, automation controller, or energy controller. If the network topology changes, the filter devices can be switched efficiently and advantageously, allowing them to be used for either the first or second operation of the inverter.

[0043] In another advantageous design approach for filter devices, the contact unit is designed as an electrical converter.

[0044] With the aid of an electrical converter, also known as a changeover switch, the first and second contact units are switched simultaneously, and thus the contact units are switched simultaneously. For example, in the first switching state of the converter, the first contact unit is turned on and the second contact unit is turned off. After the converter is activated, the first contact unit is turned off and the second contact unit is turned on in the second switching state of the converter. This switching process of simultaneously switching two contact units by the electrical converter can be performed in a reversible manner.

[0045] To achieve this objective, an inverter with a filter device according to the invention is also proposed for operating a motor at an AC voltage network.

[0046] In the first advantageous design approach for inverters, the filter device is integrated into the inverter housing.

[0047] Integrating filter devices into the inverter housing of the inverter has the following advantages: for example, the inverter is always designed with filter devices in a compact manner for connecting to the first and second operations of the inverter, and customers are able to make decisions about the corresponding operation by means of the inverter settings.

[0048] To achieve this objective, a method for operating the filter device according to the invention is also proposed, wherein the filter device is configured for a first operation at a network with a grounded outer conductor designed as an AC voltage network or a first operation at an ungrounded network designed as an AC voltage network, or the filter device is configured for a second operation of the inverter at a network with a grounded network star connection designed as an AC voltage network.

[0049] In a first advantageous design of the method, during the first operation of the inverter, the components for reducing the saturation of the choke coil unit are activated, and the capacitor unit is separated from the grounded protective conductor.

[0050] In another advantageous design of this method, during the second operation of the inverter, the capacitor cells are connected to a grounded protective conductor for current outflow, and the components for reducing saturation are turned off. Attached Figure Description

[0051] The features, characteristics, and advantages of the invention described above, as well as the ways in which they are implemented, will become clearer and more readily understood in conjunction with the following description of embodiments with reference to the accompanying drawings. The drawings show:

[0052] Figure 1 A schematic diagram of a known filter device is shown.

[0053] Figure 2 A first schematic diagram of a filter device according to the present invention is shown.

[0054] Figure 3 It is shown in accordance with Figure 2 A second schematic diagram of the filter device according to the present invention in a cross-sectional view, and

[0055] Figure 4 A schematic diagram of the structure of the filter device method of the present invention is shown. Detailed Implementation

[0056] Figure 1 A schematic diagram of a known filter device 101 is shown, which is electrically arranged on a first AC voltage conductor 113 and electrically connected to the rectifier 134 of an inverter 124 via the first AC voltage conductor 113.

[0057] Inverter 124 also has converter 135, which is electrically coupled to rectifier 134 by means of DC voltage intermediate circuit 136.

[0058] The inverter 124 is coupled to the motor 133 on the output side via the converter 135 and the second AC voltage line 126, wherein the motor 133 is connected to the ground potential via the grounded protective conductor 119.

[0059] The second AC voltage conductor 126 has a line shield 143, which is connected to the ground protection conductor 119 and thus to the ground potential. When the inverter 124 is operating, line capacitors 144 are constructed relative to the line shield 134, starting from each phase of the second AC voltage conductor 126.

[0060] The filter device 101 has a choke unit 106 and a capacitor unit 103 in the form of a common-mode choke (current-compensated choke) on the first AC voltage conductor 113.

[0061] The choke unit 102 includes a first coil 106 in the first AC voltage phase 110 of the first AC voltage conductor 113, a second coil 107 in the second AC voltage phase 111, and a third coil 108 in the third AC voltage phase 112. The choke unit 102 also has a common choke core 129 constructed on the first, second, and third coils 106, 107, and 108.

[0062] The capacitor unit 103 includes a first, a second, and a third capacitor 115, 116, and 117. The first capacitor 115 is connected to the first AC voltage phase 110 of the first AC voltage line 113, the second capacitor 116 is connected to the second AC voltage phase 111 of the first AC voltage line 113, and the third capacitor 117 is connected to the third AC voltage phase 112. The capacitors 115, 116, and 117 are configured to form a capacitor star connection 118.

[0063] Capacitors 115, 116, and 117 of capacitor unit 103 are connected to a grounded protective conductor 119 via a capacitor star contact 118. Therefore, current 132 can be drawn out in the form of a common-mode current relative to the ground potential.

[0064] In the connection between the star contact 118 of the capacitor and the grounded protective conductor 119, another capacitor can be connected. Figure 1 (Not shown in the image).

[0065] The inverter 124, which includes a filter device 101, is connected to an AC voltage network 127 on its input side via a first AC voltage conductor 113. The AC voltage network 127 is designed as a network with a grounded star contact 128, specifically a TN network with the grounded star contact 128. The ground potential of the grounded star contact 128 is connected to a protective conductor 119.

[0066] In the known examples, only inverter 124 is such. Figure 1 In the case of a grounded network star connection 128 or an additional isolation transformer (as in the example), Figure 1 It can only output a current of 124 when operating at a network (not shown in the image).

[0067] Figure 2 A first schematic diagram of a filter device 1 according to the present invention is shown, which is electrically arranged on a first AC voltage conductor 13 and connected to the rectifier 34 of an inverter 24 via the first AC voltage conductor 13.

[0068] Inverter 24 also has converter 35, which is electrically coupled to rectifier 34 by means of DC voltage intermediate circuit 36.

[0069] The inverter 24 is coupled to the motor 33 on the output side via the converter 35 and the second AC voltage line 26, wherein the motor 33 is connected to the ground potential via the grounded protective conductor 19.

[0070] The second AC voltage conductor 26 has a line shield 43, which is connected to the grounded protective conductor 19 and thus to the ground potential. During the operation of the inverter 24, a line capacitor 44 is constructed relative to the line shield 34, starting from each phase of the second AC voltage conductor 126.

[0071] The filter device 1 has a choke unit 6 and a capacitor unit 3 in the form of a common-mode choke (current-compensated choke) on the first AC voltage conductor 3.

[0072] The choke unit 2 includes a first coil 6 in the first AC voltage phase 10 of the first AC voltage conductor 13, a second coil 7 in the second AC voltage phase 11, and a third coil 8 in the third AC voltage phase 12.

[0073] The component used to reduce the saturation of the choke coil unit 2 has a fourth coil 9 of the choke coil unit 2.

[0074] The components for reducing saturation also include a first contact unit 4 for connecting and disconnecting the first electrical connection of the circuit 14 at the fourth coil 9. The choke unit 2 is constructed with a common choke core 29 at the first, second, third, and fourth coils 6, 7, 8, and 9. The circuit 14 at the fourth coil... Figure 2 The first contact unit 4 is shown as short-circuited, in which the component for reducing saturation is activated.

[0075] Capacitor unit 3 includes first, second, and third capacitors 15, 16, and 17. First capacitor 15 is connected to the first AC voltage phase 10 of the first AC voltage line 13, second capacitor 16 is connected to the second AC voltage phase 11 of the first AC voltage line 13, and third capacitor 17 is connected to the third AC voltage phase 12 of the first AC voltage line 13. Furthermore, capacitors 15, 16, and 17 are configured as a capacitor star junction 18.

[0076] The capacitors 15, 16, and 17 of capacitor unit 3 are connected to the grounded protective conductor 19 via capacitor star contact 18 and second electrical contact unit 5, wherein the second contact unit 5 is electrically disconnected.

[0077] The current 32, in the form of common-mode current for the second operation of inverter 24, is... Figure 2 The potential relative to the ground is not derived.

[0078] In the connection between the capacitor star contact 18 and the grounded protective conductor 19, another capacitor can also be connected in series with the first contact unit 5. Figure 2 (Not shown in the image).

[0079] Two contact units 4, 5, each with a corresponding driveable switch, can be driven individually or jointly by the drive signal 20 of the control unit 21. Figure 2 In the middle, the two contact units 4 and 5 are configured as an electrical converter 8.

[0080] The inverter 24, equipped with filter device 1, is connected to AC voltage network 27 on the input side via a first AC voltage conductor 13. AC voltage network 27 is designed as a network with a grounded outer conductor 25, specifically a TT network with a grounded outer conductor 25. The ground potential of the grounded outer conductor 25 is not connected to the protective conductor 19.

[0081] Accordingly, Figure 2 The schematic diagram of the filter device 1 shown is provided for the first operation of the inverter 24 at a network with a grounded outer conductor 25, which is designed as an AC voltage network 27.

[0082] Furthermore, the inverter 24 with filter device 1 can also operate in this connection at an ungrounded network (e.g., an IT network) designed as an AC voltage network 27. In this case, the AC voltage network 27 is isolated from the ground potential. Figure 2 (Not shown in the image).

[0083] With the help of Figure 3 It shows as a basis Figure 2 A second schematic diagram of the cross-section of the filter device 1 according to the present invention.

[0084] The filter device 1 is electrically connected at the first AC voltage conductor 13.

[0085] The filter device 1 has a choke unit 6 and a capacitor unit 3 in the form of a common-mode choke (current-compensated choke) at the first AC voltage conductor 3.

[0086] The choke unit 2 includes a first coil 6 in the first AC voltage phase 10 of the first AC voltage conductor 13, a second coil 7 in the second AC voltage phase 11, and a third coil 8 in the third AC voltage phase 12.

[0087] The fourth coil 9 of the choke coil unit 2 has a component for reducing the saturation of the choke coil unit 2.

[0088] The saturation-reducing components also include a first contact unit 4 for connecting and disconnecting the circuit 14 at the first electrical connection at the fourth coil 9. The choke unit 2 is configured at the first, second, third, and fourth coils 6, 7, 8, and 9 to form a common choke core 29. The circuit 14 at the fourth coil... Figure 3 The circuit is shown as short-circuited through the first contact unit 4, wherein the component for reducing saturation is activated.

[0089] Capacitor unit 3 includes first, second, and third capacitors 15, 16, and 17. First capacitor 15 is connected to the first AC voltage phase 10 of the first AC voltage line 13, second capacitor 16 is connected to the second AC voltage phase 11 of the first AC voltage line 13, and third capacitor 17 is connected to the third AC voltage phase 12 of the first AC voltage line 13. Furthermore, capacitors 15, 16, and 17 are configured to form a capacitor star junction 18.

[0090] The capacitors 15, 16, and 17 of capacitor unit 3 are connected to the grounded protective conductor 19 via capacitor star contact 18 and second electrical contact unit 5, wherein the second contact unit 5 is electrically disconnected.

[0091] The current 32 in the form of common-mode current for the second operation of the inverter is in Figure 3 The potential relative to the ground was not derived.

[0092] exist Figure 3 In the diagram, the two contact units 4 and 5 are designed as electromechanical connectors 23 in the form of threaded connections 22. The threaded connection 22 of the second contact unit 5 is shown in dashed lines, which is intended to indicate that the electromechanical connector 23 is in the open state.

[0093] In the connection between the capacitor star contact 18 and the grounded protective conductor 19, another capacitor can also be connected in series with the first contact unit 5. Figure 3 (Not shown in the image).

[0094] Accordingly, as a basis Figure 2 Details Figure 3 The schematic diagram of filter device 1 shown is suitable for the first operation of the inverter at a network with a grounded outer conductor, designed as an AC voltage network. Figure 3 (Not shown in the image).

[0095] Furthermore, the inverter with filter device 1 can also operate in this connection at an ungrounded network (e.g., an IT network) designed as an AC voltage network. In this case, the AC voltage network is isolated from the ground potential. Figure 3 (Not shown in the image).

[0096] exist Figure 4 A schematic structural diagram of a method 38 for a filter device according to the present invention is shown.

[0097] Method 38 illustrates the operation of the filter device, whereby the filter device is configured for a first operation 39 of an inverter for a network with a grounded external conductor designed as an AC voltage network or for an ungrounded network designed as an AC voltage network, or the filter device is configured for a second operation of an inverter for a network with a grounded network star connection designed as an AC voltage network.

[0098] Users of the filter equipment at the inverter should select one of the two operating modes of the inverter: first operation mode 39 or second operation mode 40.

[0099] In the first operation 39 of the inverter, the component 41 for reducing the saturation of the choke coil unit is activated, and the capacitor unit is disconnected from the grounded protective conductor, wherein the current output 41 is turned off.

[0100] In the second operation 40 of the inverter, the capacitor unit is connected to a grounded protective conductor, wherein the current output 42 is activated and the component 41 for reducing saturation is turned off.

Claims

1. A filter device (1) for an inverter (24) at an AC voltage network (27), the filter device having a choke coil unit (2), a capacitor unit (3), and a component (41) for reducing the saturation of the choke coil unit (2), configured for a first operation (39) of the inverter (24) at a network of the AC voltage network (27) having a grounded outer conductor (25) or at a network of the AC voltage network (27) not grounded, wherein, The inverter (24) is capable of activating the component (41) for reducing saturation, and the capacitor unit (3) is capable of being disconnected from the grounded protective conductor (19), and configured for a second operation (40) of the inverter (24) at a network with a grounded network star connection (28) designed as an AC voltage network (27), wherein the capacitor unit (3) is capable of being connected to the grounded protective conductor (19) for current outflow (42) of current (32), and is capable of shutting off the component (41) for reducing saturation, wherein, - The choke coil unit (2) includes a first coil (6) in the first AC voltage phase (10) of the first AC voltage conductor (13), a second coil (7) in the second AC voltage phase (11), and a third coil (8) in the third AC voltage phase (12). - The component (41) for reducing saturation has a fourth coil (9) of the choke coil unit (2), - The choke unit (2) has a common choke core (29) constructed at the first coil, the second coil, the third coil, and the fourth coil (6, 7, 8, 9), and - The component (41) for reducing saturation includes a first contact unit (4) for disconnecting and connecting the first electrical connection of the circuit (14) at the fourth coil (9).

2. The filter device (1) according to claim 1, wherein - The capacitor unit (3) includes a first capacitor, a second capacitor, and a third capacitor (15, 16, 17). The first capacitor (15) is connected to the first AC voltage phase (10) of the first AC voltage conductor (13), the second capacitor (16) is connected to the second AC voltage phase (11) of the first AC voltage conductor (13), and the third capacitor (17) is connected to the third AC voltage phase (12) of the first AC voltage conductor (13). - On the other hand, the capacitors (15, 16, 17) are configured as capacitor star contacts (18).

3. The filter device (1) according to claim 2, wherein, The second contact unit (5) is designed to disconnect and connect the second electrical connection of the capacitor unit (3) to the grounded protective conductor (19), and wherein the capacitors (15, 16, 17) of the capacitor unit (3) are electrically connected to the grounded protective conductor (19) via the capacitor star contact (18) and the second contact unit (5).

4. The filter device (1) according to any one of the preceding claims, wherein, At least one of the contact units (4, 5) has an electromechanical connector (23) or a semiconductor switch.

5. The filter device (1) according to any one of the preceding claims, wherein, At least one of the contact units (4, 5) is designed as a driveable switch (22).

6. The filter device (1) according to claim 5, wherein, At least one of the contact units (4, 5) can be driven by the drive signal (20) of the control unit (21).

7. The filter device (1) according to any one of the preceding claims, wherein, The contact units (4, 5) are designed as electrical converters (31).

8. An inverter (32) having a filter device (1) according to any one of claims 1 to 7, the inverter being used to operate a motor (33) at the AC voltage network (27).

9. The inverter (32) according to claim 8, wherein, The filter device (1) is integrated in the inverter housing (37) of the inverter (32).

10. A method (38) for operating the filter device (1) according to any one of claims 1 to 7, wherein, The filter device (1) is configured for a first operation (39) of the inverter (24) at a network with a grounded outer conductor (25) of an AC voltage network (27), or at an ungrounded network of an AC voltage network (27), or the filter device (1) is configured for a second operation (40) of the inverter (24) at a network with a grounded network star connection (28) of an AC voltage network (27).

11. The method (38) according to claim 10, wherein, During the first operation (39) of the inverter (24), the component (41) for reducing the saturation of the choke coil unit (2) is activated, and the capacitor unit (3) is separated from the grounded protective conductor (19).

12. The method (38) according to claim 10, wherein, During the second operation (40) of the inverter (24), the capacitor unit (3) is connected to the grounded protective conductor (19) for current outflow (42), and the component (41) for reducing saturation is turned off.

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