Equipotential Bonding - Siemens SIMATIC RF600 System Manual

RF600 system planning
4.7 Guidelines for electromagnetic compatibility (EMC)
Suppression of inductance
Relays, contactors, etc. generate interference voltages and must therefore be suppressed
using one of the circuits below.
Even with small relays, interference voltages of up to 800 V occur on 24 V coils, and
interference voltages of several kV occur on 230 V coils when the coil is switched. The use
of freewheeling diodes or RC circuits prevents interference voltages and thus stray
interference on conductors installed parallel to the coil conductor.
Figure 4-11
Note
All coils in the cabinet should be suppressed. The valves and motor brakes are frequently
forgotten. Fluorescent lamps in the control cabinet should be tested in particular.
4.7.6

Equipotential bonding

Potential differences between different parts of a plant can arise due to the different design
of the plant components and different voltage levels. If the plant components are connected
across signal cables, transient currents flow across the signal cables. These transient
currents can corrupt the signals.
Proper equipotential bonding is thus essential.
● The equipotential bonding conductor must have a sufficiently large cross section (at least
● The distance between the signal cable and the associated equipotential bonding
● A fine-strand conductor must be used (better high-frequency conductivity).
88
Suppression of inductance
10 mm ).
2
conductor must be as small as possible (antenna effect).
System Manual, 05/2012, J31069-D0171-U001-A13-7618
SIMATIC RF600