Compensation Filter and Method for Activating a Compensation Filter

Abstract

A compensation filter and a method for activating a compensation filter are disclosed. In an embodiment a compensation filter includes a power supply line, an electrical amplifier, an output-coupling circuit between the power supply line and an input of the electrical amplifier, an input-coupling circuit between an output of the amplifier and the power supply line, and a time switch. The time switch is connected in series with the input-coupling circuit between the output of the amplifier and the power supply line.

Claims

1-15. (canceled)

16. A compensation filter comprising: a first port; a second port; a power supply line between the first port and the second port; an electrical amplifier having an input and an output; an output-coupling circuit connected between the power supply line and the input of the amplifier; an input-coupling circuit connected between the output of the amplifier and the power supply line; and a time switch, wherein the compensation filter is configured to attenuate an instance of a common-mode interference in the power supply line, and wherein the time switch is connected in series with the input-coupling circuit between the output of the amplifier and the power supply line.

17. The compensation filter according to claim 16, wherein the input-coupling circuit comprises a capacitive element.

18. The compensation filter according to claim 17, wherein a capacitance value of the capacitive element is large enough so that leakage currents below 1 kHz are compensated for.

19. The compensation filter according to claim 16, wherein the output-coupling circuit comprises a first inductive element and a second inductive element, which is magnetically coupled to the first inductive element.

20. The compensation filter according to claim 16, wherein the amplifier comprises an operational amplifier, wherein a first resistive element is coupled between input-coupling circuit and the output of the amplifier, and wherein a second resistive element is connected between the input-coupling circuit and the input of the amplifier.

21. The compensation filter according to claim 16, wherein the compensation filter is configured to transmit a compensation signal with the same frequency, the same amplitude and inverse sign when the instance of the common-mode interference in the power supply line occurs.

22. The compensation filter according to claim 16, wherein the common-mode interference starts in a critical frequency range above a grid frequency.

23. The compensation filter according to claim 16, wherein the common-mode interference contains a leakage current.

24. The compensation filter according to claim 16, further comprising a supply circuit for the amplifier and/or the time switch.

25. The compensation filter according to claim 16, wherein the time switch comprises a relay and an actuating circuit for the relay.

26. The compensation filter according to claim 25, wherein the actuating circuit is configured to operate autonomously.

27. The compensation filter according to claim 25, wherein the actuating circuit is connected to the relay, and wherein the actuating circuit comprises a power supply connection and a series RC network.

28. The compensation filter according to claim 27, wherein the actuating circuit further comprises a first diode, a second resistive element, and a second diode.

29. The compensation filter according to claim 16, wherein the time switch is configured to couple the output of the amplifier to the power supply line only after a delay of 0.1 s or more after the compensation filter is turned on.

30. A method for activating a compensation filter having an amplifier and a power supply line, the method comprising: coupling the power supply line to a power source and/or to an electrical load; and delaying a coupling between amplifier and power supply line.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Core aspects of the compensation filter and details of preferred embodiments are shown in the schematic figures, in which:

[0056] FIG. 1 is an equivalent circuit of a simple embodiment of the compensation filter;

[0057] FIG. 2 is an equivalent circuit of an embodiment having a supply circuit, in which the power supply line comprises three conductors;

[0058] FIG. 3 shows a simple embodiment of an actuating circuit for the time switch; and

[0059] FIG. 4 shows typical voltage curves during turn-on and turn-off of the actuating circuit.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0060] FIG. 1 shows the equivalent circuit of a simple embodiment of the compensation filter KF. The compensation filter KF has a first port P1 and a second port P2. A power supply line SL is connected therebetween. In addition, the compensation filter KF comprises an amplifier, for instance an electronic amplifier ELV comprising electronic circuit components, for example an operational amplifier. The output-coupling circuit AKS is connected between the power supply line SL and the amplifier V. The input-coupling circuit EKS is connected between the amplifier V and the power supply line SL. The time switch ZS is connected between the amplifier V and the input-coupling circuit EKS.

[0061] The amplifier V can be supplied with electrical power via a supply connection VA.

[0062] The time switch ZS is used to conduct the compensation signal formed by the amplifier to the power supply line via the input-coupling circuit EKS only once transient processes in the amplifier V have come to an end and the amplifier V has starting working in full.

[0063] The output-coupling circuit AKS comprises coupled inductive elements in order to pass electrical power representative of the interference signal to the amplifier V.

[0064] FIG. 2 illustrates the possibility of providing different phases in the power supply line SL. FIG. 2 accordingly shows an embodiment in which the power supply line SL has three different conductors. The first port accordingly consists of three individual connections. The second port P2 also has three individual connections. The input-coupling circuit EKS has a neutral point SP, which ideally lies at the same electrical potential as ground. The neutral point SP is coupled to the amplifier V via a parallel circuit composed of a resistive element and the coupling capacitance CO. The time switch ZS, which can comprise a relay R or an electronic power switch, is connected therebetween. The switch of the time switch ZS is controlled here by an actuating circuit. The time switch ZS and the amplifier V are supplied with electrical power by a shared supply circuit PSU. Said supply circuit PSU may itself be supplied with electrical power from an external power source or by extracting electrical power from the power supply line SL.

[0065] FIG. 3 shows a possible topology of an actuating circuit AS for the relay R. The actuating circuit AS has a power input IN and an RC network RC. The RC network RC has a resistive element RE and a capacitive element CE, which are connected in series. If the actuating circuit AS is turned on, the capacitive element CE of the RC network RC is charged via the resistive element RE. This charging causes a time delay, after which a sufficiently high voltage to operate the relay lies across the coil of the relay R. A second resistive element RE serves as a pull-down resistor in order to assign a defined potential to the node between the resistive element RE and the capacitive element CE of the RC network RC in case a defined input voltage is not applied to the actuating circuit at the input IN.

[0066] The diode D1 is used to discharge the capacitive element CE of the RC network RC more quickly when the actuating circuit AS is turned off. The diode D2 serves as a protective element for protecting the circuit in the event of too high a voltage lying at the input IN.

[0067] The coil of the relay R acts in the actuating circuit AS effectively as a resistive element.

[0068] FIG. 4 shows voltage curves over time during turn-on and turn-off of the actuating circuit AS. After a time interval T1 after the actuating circuit AS of FIG. 3 is turned on, the voltage lying across the capacitive element CE of the RC network is high enough for a first critical voltage S1 to be reached. The voltage lying across the coil of the relay R in this case is now sufficient to turn on the relay and to couple the amplifier V to the power supply line SL.

[0069] A time difference T2 after the actuating circuit AS is turned off, i.e. after the voltage is removed from the input IN, the capacitive element CE of the RC network RC is discharged via the diode to such an extent that there is a drop in voltage to below a second critical voltage S2, with the result that the relay R disconnects again the connection between amplifier V and power supply line SL via the input-coupling circuit EKS.

[0070] Achieving the delay T1 in turning on the actuating circuit when the compensation filter is turned on means that the amplifier V is given enough time to settle and to reach the intended way of working.

[0071] In particular, interference situations caused by leakage currents when plugging in the power cableif the electrical load is connected directly to the second portare thereby prevented, and the electrical load can be operated safely on a power cable having a ground fault circuit.

[0072] The compensation filter and the method for activating a compensation filter are not restricted to the embodiments and details shown and described. The compensation filter may contain further circuit elements, and the method may comprise additional method steps.