Coupling mechanism
Cause
Typical source
Inductive coupling
Inductive or magnetic coupling occurs
between two current active line loops.
The magnetic flows associated with
the currents induct interference vol-
tages. The coupling is proportional to
the time related change of the current.
n
Transducers, motors, electric
welding devices
n
Parallel net cables
n
Cables with toggled currents
n
Signal cable with high frequency
n
Unused coils
Radiate power coupling
One talks of radiate power coupling,
when an electromagnetic wave meets
a line circuit. The hit of the wave
inducts currents and voltages.
n
Sender in the neighbourhood (e.g.
walkie-talkie)
n
Sparking lines (sparking plugs,
collector of electric motors,
welding devices)
In the most times it is enough to take care of some elementary rules to guarantee the
EMC. Please regard the following basic rules when installing your PLC.
n
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 there-
fore less suitable for grounding.
n
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).
n
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 favourable.
–
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 impe-
dance-low with the cabinet.
–
Use metallic or metallised plug cases for isolated data lines.
Basic rules for EMC
HMI
Industrial Security and Installation guidelines
Installation guidelines > Basic rules for the EMC-equitable assembly of installations
HB160 | TP-smart | H71-71A41-0 | en | 23-10
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