FERRITE
TECHNOLOGY
The basis of this technology is a high quality ferrite powder.
EUPEN developed a special compound: a polymer material mixed with a
considerable quantity of homogeneously fine ferrite powder. This compound
is called EMC/COM and it can be extruded around copper conductors.
The ferrite
itself is a non-conducting material, but it has a very interesting
magnetic behaviour. As a ferromagnetic material, it will go through
hysteresis loops whenever it is under influence of an alternating
magnetic field. Consecutively magnetizing and demagnetizing the material
will cause considerable losses of high frequency energy. This energy is
absorbed in the ferrite grains and converted into heat.
This effect is more or less proportional to the field frequency.
By coating
conductors with a thin layer of ferrite compound, high frequencies will
be strongly attenuated, because their energy will be absorbed by the
ferrite powder.
This applies to high frequency disturbances that are propagating on the
conductor and which we don't want to disturb the environment, as well as
to surrounding interferences, which we want to prevent from disturbing
the signals on our cable.
The
attenuation that is obtained is proportional to the cable length.
Moreover,
the ferrite layer's continuous spreading over the whole cable length
makes sure that there will be no sudden changes in characteristic
impedance along the cable. Otherwise, such discontinuities might cause
high frequency signals to be reflected at those spots and to be sent back
to the mains or to other devices.
At last, it
is important to emphasize that a ferrite coated conductor will much less
divert disturbances to the earth; this is an interesting feature, because
disturbances that "disappear" to earth are not really gone.
They will reemerge elsewhere and cause problems.
The
HF components of the electromagnetic field are absorbed by the conductor's
ferrite coating (EMC/COM). Effective protection against 50 or 60 Hz magnetic
fields is obtained through a very short length of twist ; this considerably
reduces the radiated magnetic field. The ferrite layer keeps this reduced
magnetic field within the cable instead of allowing it to "break out".
The cable's static screen grants excellent protection against 50 or 60 Hz
electric fields
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