FILTER APPARATUS

Abstract

A filter apparatus for use in a converter in an alternating voltage supply system includes a choke unit, a capacitor unit and saturation reducing unit for the choke unit. A converter having the filter apparatus and to a method for operating the filter apparatus are also disclosed.

Claims

1.-15. (canceled)

16. A filter apparatus configured for a first operation of a converter connected via a first AC cable to a three-phase AC voltage network having a grounded external conductor or to a three-phase AC voltage network without a ground connector and for a second operation of the converter on a three-phase AC voltage network with a grounded network star point, the filter apparatus comprising: a choke unit comprising a first coil in a first AC voltage phase, a second col in a second AC voltage phase and a third coil in a third AC voltage phase, a capacitor unit which can be connected to a grounded protective conductor for current dissipation of a current and disconnected from the grounded protective conductor, and a saturation reducing unit comprising a fourth coil of the choke unit and having a first contact unit configured to open and close a first electrical connection of a circuit on the fourth coil for reducing saturation of the choke unit when the first electrical connection is closed, wherein the first, second, third and fourth coil have a common choke core.

17. The filter apparatus of claim 16, wherein the capacitor unit comprises a first capacitor having a first terminal connected to the first AC voltage phase, a second capacitor having a first terminal connected to the second AC voltage phase, and a third capacitor having a first terminal connected to the third AC voltage phase, and wherein second terminals of the first, second and third capacitors are connected at a capacitor star point.

18. The filter apparatus of claim 17, further comprising a second contact unit connected between the capacitor star point and the grounded protective conductor for opening and closing a second electrical connection of the capacitor unit to the grounded protective conductor.

19. The filter apparatus of claim 18, wherein at least one of the first and second contact units comprises an electromechanical connector or a semiconductor switch.

20. The filter apparatus of claim 18, wherein at least one of the first and second contact units is designed as an actuatable switch.

21. The filter apparatus of claim 20, wherein at least one of the first and second contact units is actuatable an actuation signal from a control unit.

22. The filter apparatus of claim 18, wherein the first and second contact units are designed as an electric changer.

23. A converter for operating an electric machine on a three-phase AC voltage network, the converter comprising the filter apparatus of claim 16.

24. The converter of claim 23, further comprising a converter housing, wherein the filter apparatus is integrated in the converter housing.

25. A method for operating a filter apparatus as claimed in claim 16, comprising: setting the filter apparatus for the first operation of the converter in the three-phase AC voltage network with a grounded external conductor or without a ground connector, or setting the filter apparatus for the second operation of the converter in the AC voltage network with a grounded network star point.

26. The method of claim 26, further comprising in the first operation of the converter, activating the saturation reducing unit of the choke unit and disconnecting the capacitor unit from the grounded protective conductor.

27. The method of claim 25, further comprising in the second operation of the converter, connecting the capacitor unit to the grounded protective conductor for current dissipation and deactivating the saturation reducing unit.

Description

[0056] FIG. 1 shows a schematic representation of a known filter apparatus 101 which is electrically arranged on a first AC voltage cable 113 and is electrically connected via the first AC voltage cable 113 to a rectifier 134 of a converter 124.

[0057] The converter 124 also has an inverter 135 which is electrically coupled to the rectifier 134 by means of a DC voltage intermediate circuit 136.

[0058] The converter 124 is coupled on the output side via the inverter 135 and a second AC voltage cable 126 to an electric machine 133, the electric machine 133 being connected to the ground potential via a grounded protective conductor 119.

[0059] The second AC voltage cable 126 has a cable shield 143 which is connected to the grounded protective conductor 119 and thus to the ground potential. During operation of the converter 124, cable capacitances 144 are formed, starting from the individual phases of the second AC voltage cable 126 with respect to the cable shield 134.

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

[0061] The choke unit 102 comprises a first coil 106 in a first AC voltage phase 110, a second coil 107 in a second AC voltage phase 111 and a third coil 108 in a third AC voltage phase 112 of the first AC voltage cable 113. Furthermore, the choke unit 102 forms a common choke core 129 on the first, second and third coils 106,107,108.

[0062] The capacitor unit 103 comprises a first, second and third capacitor 115,116,117. The first capacitor 115 is connected, on the one hand, to the first AC voltage phase 110 of the first AC voltage cable 113, the second capacitor 116 is connected on the other hand, to the second AC voltage phase 111 of the first AC voltage cable 113, and the third capacitor 117 is connected, on the other hand, to the third AC voltage phase 112 of the first AC voltage cable 113 and the capacitors 115,116,117, on the other hand form a capacitor star point 118.

[0063] The capacitors 115,116,117 of the capacitor unit 103 are connected to to grounded protective conductor 119 via the capacitor star point 118. Thus, a current 132 in the form of a common-mode current can be dissipated with respect to the ground potential.

[0064] It is possible that a further capacitor can be connected in the connection between the capacitor star point 118 and the grounded protective conductor 119 (not shown in FIG. 1).

[0065] The converter 124 with the filter apparatus 101 is connected on the input side by means of the first AC voltage cable 113 to an AC voltage network 127. The AC voltage network 127 is designed as a network with the grounded star point 128, here as a TN network with a grounded star point 128. The ground potential for the grounded star point 128 is connected to the protective conductor 119.

[0066] A dissipation of the current 124 is only possible in the known example insofar as the converter 124 is operated, as in FIG. 1, on the network with a grounded network star point 128 or with an additional isolating transformer (not shown in FIG. 1).

[0067] FIG. 2 shows a first schematic representation of the filter apparatus 1 according to the invention, which is electrically arranged on a first AC voltage cable 13 and is connected via the first AC voltage cable 13 to a rectifier 34 of a converter 24.

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

[0069] The converter 24 is coupled on the output side via the inverter 35 and a second AC voltage cable 26 to an electric machine 33, the electric machine 33 being connected to the ground potential via a grounded protective conductor 19.

[0070] The second AC voltage cable 26 has a cable shield 43 which is connected to the grounded protective conductor 19 and thus to the ground potential. During operation of the converter 24, cable capacitances 44 are formed, starting from the individual phases of the second AC voltage cable 26 with respect to the cable shield 34.

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

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

[0073] A means for reducing the saturation of the choke unit 2 has a fourth coil 9 of the choke unit 2.

[0074] The means for reducing saturation also comprises a first contact unit 4 for opening and closing a first electrical connection of a circuit 14 on the fourth coil 9. The choke unit 2 forms a common choke core 29 on the first, second, third and fourth coils 6,7,8,9. The circuit 14 on the fourth coil is shown in FIG. 2 as short-circuited by the first contact unit 4, the means for reducing saturation being activated.

[0075] The capacitor unit 3 comprises a first, second and third capacitor 15,16,17. The first capacitor 15 is connected, on the one hand, to the first AC voltage phase 10 of the first AC voltage cable 13, the second capacitor 16 is connected, on the other hand, to the second AC voltage phase 11 of the first AC voltage cable 13, and the third capacitor 17 is connected, on the one hand, to the third AC voltage phase 12 of the first AC voltage cable 13 and the capacitors 15,16,17, on the other hand, form a capacitor star point 18.

[0076] The capacitors 15,16,17 of the capacitor unit 3 are connected to the grounded protective conductor 19 via the capacitor star point 18 and the second electrical contact unit 5, the second contact unit 5 being electrically open. In FIG. 2, a current 32 in the form of a common-mode current for a second operation of the converter 24 is not dissipated with respect to the ground potential.

[0077] It is possible that a further capacitor in the connection between the capacitor star point 18 and the grounded protective conductor 19 can be connected in series with the first contact unit 5 (not shown in FIG. 2).

[0078] The two contact units 4,5, each with an actuatable switch 22 per contact unit 4,5, can each be actuated alone or together by means of an actuation signal 20 from a control unit 21. In FIG. 2, both contact units 4,5 are designed as an electric changer 8.

[0079] The converter 24 with the filter apparatus 1 is connected to an AC voltage network 27 on the input side by means of the first AC voltage cable 13. The AC voltage network 27 is designed as a network with a grounded external conductor 25, here as a TT network with a grounded external conductor 25. The ground potential for the grounded external conductor 25 is not connected to the protective conductor 19.

[0080] Accordingly, the schematic representation of the filter apparatus 1 shown in FIG. 2 is provided for a first operation of the converter 24 on the network designed as an AC voltage network 27 with a grounded external conductor 25.

[0081] Furthermore, the converter 24 with the filter apparatus 1 can also be operated in this connection on a ground-free network designed as an AC voltage network 27, for example, an IT network. In this case, the AC voltage network 27 is insulated from the ground potential (not shown in FIG. 2).

[0082] FIG. 3 shows a second schematic representation of the filter apparatus 1 according to the invention as a cut-out according to FIG. 2.

[0083] The filter apparatus 1 is electrically arranged on the first AC voltage cable 13.

[0084] The filter apparatus 1 has the choke unit 6 in the form of a common-mode choke (current-compensated choke) and the capacitor unit 3 on the first AC voltage cable 3.

[0085] The choke unit 2 comprises the first coil 6 in the first AC voltage phase 10, the second coil 7 in the second AC voltage phase 11 and the third coil 8 in the third AC voltage phase 12 of the first AC voltage cable 13.

[0086] The means for reducing the saturation of the choke unit 2 comprises the fourth coil 9 of the choke unit 2.

[0087] The means for reducing saturation also comprises the first contact unit 4 for opening and closing the first electrical connection of the circuit 14 on the fourth coil 9. The choke unit 2 forms the common choke core 29 on the first, second, third and fourth coils 6,7,8,9. The circuit 14 on the fourth coil is shown in FIG. 3 as short-circuited by the first contact unit 4, the means for reducing saturation being activated.

[0088] The capacitor unit 3 comprises the first, second and third capacitor 15,16,17. The first capacitor 15 is connected, on the one hand, to the first AC voltage phase 10 of the first AC voltage cable 13, the second capacitor 16 is connected, on the other hand, to the second AC voltage phase 11 of the first AC voltage cable 13 and the third capacitor 17 is connected, on the other hand, to the third AC voltage phase 12 of the first AC voltage cable 13, and the capacitors 15,16,17, on the other hand, form the capacitor star point 18.

[0089] The capacitors 15,16,17 of the capacitor unit 3 are connected to the grounded protective conductor 19 via the capacitor star point 18 and the second electrical contact unit 5, the second contact unit 5 being electrically open. A current 32 in the form of a common-mode current for the second operation of the converter is not dissipated with respect to the ground potential in FIG. 3.

[0090] The two contact units 4,5 are each designed as electromechanical connectors 23 in the form of screw connections 22 in FIG. 3. The screw connection 22 of the second contact unit 5 is shown in dashed lines, which is intended to show the electromechanical connector 23 as open.

[0091] It is possible that a further capacitor can be connected in series with the first contact unit 5 in the connection between the capacitor star point 18 and the grounded protective conductor 19 (not shown in FIG. 3).

[0092] Accordingly, the schematic representation of the filter apparatus 1 shown in FIG. 3 in detail according to FIG. 2 is suitable for a first operation of the converter on the network designed as an AC voltage network with a grounded external conductor (not shown in FIG. 3).

[0093] Furthermore, the converter with the filter apparatus 1 can also be operated in this connection on a ground-free network designed as an AC voltage network, for example, an IT network. In this case, the AC voltage network is insulated from the ground potential (not shown in FIG. 3).

[0094] FIG. 4 shows a schematic structure chart of a method 38 for the filter apparatus according to the invention.

[0095] The method 38 shows the operation of the filter apparatus, according to which the filter apparatus for the first operation 39 of the converter is set for the network designed as an AC voltage network with a grounded external conductor or for the ground-free network designed as an AC voltage network, or the filter apparatus for the second operation 40 of the converter is set for the network designed as an AC voltage network with a grounded network star point.

[0096] The user of the filter apparatus on the converter should decide upon one of the two operating modes of the converter, first operation 39 or second operation 40.

[0097] In the first operation 39 of the converter, the means for reducing the saturation 41 of the choke unit is activated and the capacitor unit is disconnected from the grounded protective conductor, the current dissipation 41 being deactivated.

[0098] In the second operation 40 of the converter, the capacitor unit is connected to the grounded protective conductor, the current dissipation 42 being activated and the means for reducing saturation 41 being deactivated.