Protection Against Electromagnetic Interference; Basic Points For System Installations Conforming With Emc Requirements - Siemens SIMATIC S7-300 Hardware And Installation Manual

12.2

Protection against electromagnetic interference

12.2.1 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.
bus signal
protective earth
Figure 12-1 Possible paths of electromagnetic interference
S7-300 Programmable Controller Hardware and Installation
A5E00105492-02
electromagnetic
fields
SF
SIEMENS
BUSF
DC5V
FRCE
RUN
STOP
power supply module
Appendix
process wiring
12-3