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2.2 Industrial Security and Installation Guidelines
• Electromagnetic fields (RF coupling)
• Magnetic fields with power frequency
• Bus system
• Power supply
• Protected earth conductor
Depending on the spreading medium (lead bound or lead free) and the distance to the interference cause, interfer-
ences to your control occur by means of different coupling mechanisms.
There are:
• galvanic coupling
• capacitive coupling
• inductive coupling
• radiant coupling
(4) Basic rules for EMC
In the most times it is enough to take care of some elementary rules to guarantee the EMC. Please regard the fol-
lowing basic rules when installing your PLC.
• Take care of a correct area-wide grounding of the inactive metal parts when installing your components.
– Install a central connection between the ground and the protected earth conductor system.
– Connect all inactive metal extensive and impedance-low.
– Please try not to use aluminium parts. Aluminium is easily oxidizing and is therefore less suitable for
grounding.
• When cabling, take care of the correct line routing.
– Organize your cabling in line groups (high voltage, current supply, signal and data lines).
– Always lay your high voltage lines and signal respectively data lines in separate channels or bundles.
– Route the signal and data lines as near as possible beside ground areas (e.g. suspension bars, metal rails, tin
cabinet).
• Proof the correct fixing of the lead isolation.
– Data lines must be shielded.
– Analog lines must be shielded. When transmitting signals with small amplitudes the one sided laying of the
isolation may be favorable.
– Cables for frequency inverters, servo and stepper motors must be shielded.
– Lay the line isolation extensively on an isolation/protected earth conductor rail directly after the cabinet
entry and fix the isolation with cable clamps.
– Make sure that the isolation/protected earth conductor rail is connected impedance-low with the cabinet.
– Use metallic or metallized plug cases for isolated data lines.
• In special use cases you should appoint special EMC actions.
– Consider to wire all inductivities with erase links.
– Please consider luminescent lamps can influence signal lines.
• Create a homogeneous reference potential and ground all electrical operating supplies when possible.
– Please take care for the targeted employment of the grounding actions. The grounding of the PLC serves for
protection and functionality activity.
– Connect installation parts and cabinets with your PLC in star topology with the isolation/protected earth con-
ductor system. So you avoid ground loops.
– If there are potential differences between installation parts and cabinets, lay sufficiently dimensioned poten-
tial compensation lines.
(5) Isolation of conductors
Electrical, magnetically and electromagnetic interference fields are weakened by means of an isolation, one talks
of absorption. Via the isolation rail, that is connected conductive with the rack, interference currents are shunt
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