Keba KeTop T50VGA, Руководство пользователя, Страница: 155 / 165

Handheld Terminal CE Conformity, Directives and Standards
User's Manual, Version: 1.3 155
© KEBA 2007
Line filter
Shielded housing
of the device
Line cable
(unshielded)
Device
well connected
network filter
Shield is required
in this section! L, N and PE -
as short as possible!
Clips for screen
contacting
Correct connection of a compact line filter
When connecting line filters, attention should first be paid to the frequency
ranges to be filtered. If frequencies in the MHz range are also to be filtered,
such a line filter should have a metal housing. Line filters with plastic hous-
ings are normally not suitable for this purpose.
Current-compensating chokes
Device manufacturers sometimes specify the use of current-compensating
chokes or the installation of ferrite loops in the power supply line. Many ex-
amples of this can be found in motor lines that are fed by frequency invert-
ers.
Such chokes (see the following illustrations) suppress common-mode inter-
ference currents (I
s
) and allow the operating currents (I
B
) to pass unhin-
dered. It should be noted that the operating currents in the core produce
self-cancelling magnetic fields so that the operating current does not satu-
rate the ferrite cores. Such throttles must also be placed at the inlet to the
shielded housing of the device.
Ferrite hoop
Power supply
lines
I
O
I
O
I
I
I
I
I
I
... Interference current
I
O
... Operating current
Current flow of a current-compensating choke
Ferrite hoop
Power supply
lines
I
O
=0
I
I
I
I
... Interference current
I
O
... Operating current
Current flow of a current-compensating choke