Special Measures For Interference-Free Operation - Siemens SIMATIC S5-100U System Manual

S5-100U
Note the following when connecting the cable shield:
• Use metal cable clamps for fixing the braided shield. The clamps have to enclose the shield over
a large area and make good contact (see Figure 3-26).
• Connect the shield to a shield bar immediately at the point where the cable enters the cabinet.
Route the shield to the module; do not connect it to the module.
Figure 3-26. Fixing Shielded Cables with Various Types of Cable Clamps
3.4.5

Special Measures for Interference-Free Operation

Arc Suppression Elements For Inductive Circuits
Normally, inductive circuits (e.g. contactor or relay coils) energized by SIMATIC S5 do not require to
be provided with external arc suppressing elements since the necessary suppressing elements are
already integrated on the modules.
It only becomes necessary to provide arc supressing elements for inductive circuits in the following
cases:
• If SIMATIC S5 output circuits can be switched off by additionaly inserted contactors (e.g. relay
contactors for EMERGENCY OFF). In such a case, the integral suppressing elements on the
modules become ineffective.
If the inductive circuits are not energized by SIMATIC S5.
•
You can use free-wheeling diodes, varistors or RC elements for wiring inductive circuits.
Wiring coils activated by direct current
with diode
+ +
-
EWA 4NEB 812 6120-02b
with Zener diode
-
Figure 3-27. Wiring Coils
Installation Guidelines
Wiring coils activated by alternating current
with varistor with RC element
3-33