Bosch Rexroth VCH 08.1 Manual page 50

48/117 Bosch Rexroth AG
Technical Data
device and the cable shield must be contacted on both ends. This prevents
interference produced by the device from being transmitted externally where it
could penetrate other systems. It also prevents the penetration of interference
signals back into connection wires that have already been filtered.
Line cable
(unshielded)
well-connected
line filter
Fig.4-35: Correct connection of a compact line filter outside the device
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 housings
are normally not suitable for this purpose.
Current-compensated chokes
Device manufacturers sometimes specify the use of current-compensating
chokes or the installation of ferrite loops in the power supply line. Many exam‐
ples of this can be found in motor lines that are fed by frequency inverters. Such
chokes (see the following figures) suppress common-mode interference cur‐
rents (I ) and allow the operating currents (I
S
noted that the operating currents in the core produce self-cancelling magnetic
fields so that the operating current does not saturate the ferrite cores. Such
throttles must also be placed at the inlet to the shielded housing of the device.
① Supply lines
② Ferrite loop
I Interference current
S
I Operating current
B
Fig.4-36: Current flow of a current-compensating choke
Ferrite Ferrites operating via data lines work in a similar way to current-compensating
chokes. The wanted signals (see figure) can pass unhindered and the interfer‐
ence signals are attenuated. A fundamental difference from current-compen‐
sating chokes is that in the case of ferrites the application range takes place at
DOK-SUPPL*-VCH*08.1***-PR02-EN-P
Rexroth IndraControl VCH 08.1 Hand-held Terminal
Clips for
screen
contacting
Line filter
L, N and PE -
Shield is required
as short as possible!
in this section!
) to pass unhindered. It should be
B
I
B
I
S
I
S
I I
B
I
S
Σ
I =0
B
Device
Shield housing
of the device
1
2
1
2