Electromagnetic interference filter

1 . Electromagnetic interference filter, having line-side terminals for a connection to an electric supply and load-side terminals for a connection to a load device, the electromagnetic interference filter comprising:

a load-side passive electromagnetic interference filter stage connected to the load-side terminals and configured to suppress common-mode noise, a line-side electromagnetic interference filter stage connected to the line-side terminals, and configured to suppress differential-mode noise, wherein the load side passive electromagnetic interference filter stage is configured to suppress differential mode noise and the line-side electromagnetic interference filter stage is a line-side active electromagnetic interference filter stage, further comprising an intermediate active electromagnetic interference filter stage between the load-side electromagnetic interference filter stage and the line-side electromagnetic interference filter stage, configured to suppress common-mode noise, in combination with the load device injecting noise with a fundamental frequency onto an electric supply line, wherein the load-side passive electromagnetic interference filter stage exhibits a resonance frequency that is smaller or greater than the fundamental frequency of the noise.

2 . The electromagnetic interference filter of claim 1 , wherein the resonance frequency of the load-side passive electromagnetic interference filter stage is at least two times, preferably five times, smaller or greater than the fundamental frequency of the noise.

3 . The electromagnetic interference filter of claim 1 , wherein the load-side passive electromagnetic interference stage comprises a first inductive filtering element and a second inductive filtering element each being inductively coupled to the electric supply line and each of the inductive filtering elements being configured to suppress common-mode noise, and a capacitive filtering element, electrically connected to the electric supply line and configured to suppress common-mode and differential-mode noise.

4 . The electromagnetic interference filter of claim 1 , wherein the intermediate active electromagnetic interference filter stage includes a common-mode current sensor generating a common-mode signal in relation to a common-mode noise circulating in the electric supply line and a current amplifier receiving the common-mode noise signal and whereas the current amplifier is configured to inject a noise cancellation current into the electric supply line.

5 . The electromagnetic interference filter of claim 1 , wherein the line-side active electromagnetic interference filter stage comprises a voltage amplifier circuit connected to the electric supply line and configured to receive a noise voltage and provide a noise cancellation voltage to the supply line through an actuation transformer inductively coupled to the electric supply line.

6 . The electromagnetic interference filter of claim 5 , wherein the noise cancellation voltage comprises differential-mode and/or common-mode components.

7 . The electromagnetic interference filter of claim 5 , wherein the actuation transformer comprises:

a first and a second magnetic core element, and

a plurality of separate coil elements each being wound around at least one of the magnetic core elements, wherein

the magnetic core elements are arranged to enclose a plurality of conductors of the electric supply line to form a closed magnetic circuit.

8 . The electromagnetic interference filter of claim 7 , wherein the electric supply line is a single-phase or three-phase or multiphase AC line, and the actuation transformer is configured as a single-phase, respectively a three-phase, respectively multiphase transformer with a single magnetic core formed by the first and second magnetic core elements.

9 . Method for manufacturing the electromagnetic interference filter of claim 7 , the method comprising the steps of:

providing the first and the second magnetic core element

uniting the first and the second magnetic core element for providing a closed magnetic circuit

securing the first and the second magnetic core elements

connecting the separate coil elements to the load-side terminals on a first side of the actuation transformer and to the line-side terminals on a second side of the actuation transformer opposed the first side.

10 . The electromagnetic interference filter of claim 1 , wherein

the intermediate active electromagnetic interference filter stage and/or the line-side active electromagnetic interference filter stage include an amplifier circuit with a first control loop and a second control loop, wherein

the first control loop comprises an amplifier module with a transfer function and a gain function for adjusting a gain of the amplifier module, wherein

the second control loop comprises a gain control function configured to adjust the gain function of the first control loop in order to avoid saturation in the amplifier circuit, depending on an input signal.

11 . The electromagnetic interference filter of claim 10 , wherein the gain control function of the second control loop adjusts the gain function of the first control loop following a linear function with an upper end.

12 . The electromagnetic interference filter of claim 11 , wherein the upper end of the linear function corresponds to a peak threshold value setpoint in the gain control function.

13 . The electromagnetic interference filter of claim 10 , wherein the first control loop and the second control loop each is configured to have a time constant, wherein the time constant of the second control loop is greater than the time constant of the first control loop.