Prevention Of Interference Sources - Siemens SIMATIC RF600 System Manual

When RFID modules are used, different components in the overall system can act as a coupling
path:
Table 4-2
Coupling path
Conductors and cables
Control cabinet or housing
4.8.5

Prevention of interference sources

A high level of immunity to interference can be achieved by avoiding interference sources. All
switched inductances are frequent sources of interference in plants.
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 4-17
SIMATIC RF600
System Manual, 06/2010, J31069-D0171-U001-A10-7618
Causes of coupling paths
Invoked by
● Incorrect or inappropriate installation
● Missing or incorrectly connected shield
● Inappropriate physical arrangement of cables
● Missing or incorrectly wired equalizing conductor
● Missing or incorrect earthing
● Inappropriate physical arrangement
● Components not mounted securely
● Unfavorable cabinet configuration
Suppression of inductance
Draft Version 02.06.2010
4.8 Guidelines for electromagnetic compatibility (EMC)
RF600 system planning
75