System manual CECX / EC directives and standards
12.1 Why EMC-compatible wiring?
The interference immunity of an electrical system is crucially dependent on
EMC-compatible wiring and shielding. Experience in service shows that in-
adequate wiring and shielding of plant components are the most frequent
causes of faults and plant failures.
Faults caused by EMC are much more difficult to deal with than "conven-
tional" malfunctions:
Due to the type of symptom that occurs, they are often not recognized
as such and often resemble a fault in a module that is actually working
correctly.
They typically occur intermittently and are difficult to reproduce.
Troubleshooting is correspondingly complex and expensive.
Thus, from the very beginning, make sure you pay attention to careful
wiring and shielding in accordance with the guidelines described be-
low.
12.1.1 Basic structure of EMC measures
The EMC concept for the entire CECX modular control system is designed
in such a way that each module can independently withstand the influences
that occur in an electro-magnetically affected industrial environment.
A closed shield casing is assumed. This shield cover is correspondingly
expanded by shielded interfaces or, if unshielded interfaces are used, the
open shield cover is “closed” again via a filter (see figure).
GND
Shield connected to
GND via connector
shielded
interface
unshielded
interface
"Closed"
shield casing
print
filter
Corresponding connections on the modules are provided for shielded inter-
faces. It is therefore not necessary to connect this cable shield with the sys-
tem via additional shield clamps.
Unshielded interfaces are filtered at their connection points according to
their useful signal. Thus, it is not necessary to additionally filter these lines.
CECX-II 12-2
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