Connect the shield of analog signal lines at one end over a large surface area,
normally in the control cabinet at the analog device. Make sure the connection
to ground/housing is short and over a large surface area.
Connect the shield of digital signal lines at both ends over a large surface area
and in short form. In the case of potential differences between beginning and
end of the line, run an additional bonding conductor in parallel. This prevents
compensating current from flowing via the shield. The guide value for the cross
section is 10 mm
2
.
You absolutely have to equip separate connections with connectors with groun-
ded metal housing.
In the case of non-shielded lines belongs to the same circuit, twist feeder and
return cable.
11.3.9 General Measures of Radio Interference Suppression for Relays,
Contactors, Switches, Chokes and Inductive Loads
If, in conjunction with electronic devices and components, inductive loads, such
as chokes, contactors, relays are switched by contacts or semiconductors, ap-
propriate interference suppression has to be provided for them:
● By arranging free-wheeling diodes in the case of d.c. operation
● In the case of a.c. operation, by arranging usual RC interference suppression
elements depending on the contactor type, immediately at the inductance
Only the interference suppression element arranged immediately at the induc-
tance does serve this purpose. Otherwise, the emitted noise level is too high
which can affect the function of the electronic system and of the drive.
If possible, mechanical switches and contacts should only be realized as snap
contacts. Contact pressure and contact material must be suited for the corre-
sponding switching current.
Slow-action contacts should be replaced by snap switches or by solid-state
switches, because slow-action contacts strongly bounce and are in an undefined
switching status for a long time which emits electromagnetic waves in the case
of inductive loads. These waves are an especially critical aspect in the case of
manometric or temperature switches.
EFC 3600
Bosch Rexroth AG
Electromagnetic Compatibility (EMC)
DOK-RCON03-EFC-3600***-IT03-EN-P
159/259
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