Appendix
S7-300 Programmable Controller Hardware and Installation
A5E00105492-01
11-3
11.2 protection against electromagnetic interference
11.2.1 Basic points for system installations conforming with EMC
requirements
Definition: EMC
EMC (electromagnetic compatibility) describes the capability of electrical
equipment to operate free of errors in a given electromagnetic environment, without
being subject to external influence and without influencing external devices in any
way.
Introduction
Although your S7-300 and its components are developed for an industrial
environment and high electromagnetic compatibility, you should draw up an EMC
installation plan before you install the controller under consideration of all possible
interference sources.
Possible effects of interference
Electromagnetic noise can influence a PLC in various ways:
• Electromagnetic fields having a direct influence on the system
• Interference via bus signals (PROFIBUS-DP etc.)
• Interference coupling via the system wiring
• Interference influencing the system via the power supply and/or protective
ground
The figure below shows the likely paths of electromagnetic interference.
electromagnetic
fields
power supply module
protective earth
bus signal
process wiring
SF
BUSF
DC5V
FRCE
RUN
STOP
SIEMENS
Figure 11-1 Possible paths of electromagnetic interference
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