Lexikon Netzfilter specifications

Category : Lexicon

A mains filter is a component that is looped into the mains line of a device in order either not to let interference get into a device, or not to let interference get out of it. This is about line-bound interference, a network filter does not help against interference emitted as a radio wave.

Mains filters are already installed in many devices. This typically happens with devices with a switched-mode power supply, because the legislator requires that the disturbances generated by such power supplies must not come out of the device to an excessive extent. So this is more about protecting the environment than about the device itself, from interference. However, a mains filter usually has a certain effect in both directions.

These mains filters are usually designed in such a way that interference frequencies above 100 kHz are sufficiently damped. So it's about radio frequencies. Harmonic distortions of the mains frequency, on the other hand, are hardly damped, because their frequencies are much lower. It is assumed that these do not harm.

For mains filters for external connection, which are available as accessories, it makes sense to make the line between the filter and the device short so that interference is not caught here again.

Most devices are already filtered well enough by themselves, so that additional mains filters do not bring any advantage. It is therefore worthwhile to check whether there is a corresponding problem at all before the purchase. The available filters also have different characteristics, so that the filters should be selected according to the problem if necessary.

A simple and inexpensive filter measure consists in the use of ferrite cores, which are placed either as a folding ferrite around the mains line, or as a ferrite ring through which the line is passed one or more times. The ferrite should be close to the device.