power line filter (power supply) (PLF)
The term mains filter stands on the one hand for overvoltage protection with which the mains voltage is filtered against interference, glitches, spikes or electrosmog, but it is also used on the other hand for content filters on the Internet to prevent user access to undesirable, violent, extreme right-wing or pornographic websites.
Line filters or mains suppression filters for filtering mains voltage are passive low-pass filters consisting of inductors and capacitors. They are constructed in such a way that there is a low-pass filter in each current-carrying outer conductor and in the neutral conductor, and the capacitors of both low-pass filters are connected to ground at a junction point.
The current-compensating chokes are located in the neutral conductor and in the phase-carrying outer conductor, they consist of several identical windings and use a common ferrite core. This construction allows the chokes to compensate well for similar disturbances occurring on both current-carrying conductors. The cut-off frequency of the low-pass filters is selected so that they do not form a reactance for the mains frequency.