Guidelines for the Planning and Installation of the Product
S5-95F
3.2.2
Most Important Basic Rules for Ensuring EMC
It is often sufficient to comply with a few elementary rules for ensuring EMC. When installing the
control system, therefore, observe the following five basic rules.
When installing the programmable controllers, provide large-area good quality grounding of
the inactive metal parts (see section 3.3.1)
•
Make a large-area low-impedance interconnection of all inactive metal parts.
•
For screw connections on painted and anodized metal parts, either use special contact washers
or remove the insulating protective layers.
•
If possible, do not use aluminium parts. Aluminium oxidizes easily and is therefore less suitable
for grounding.
•
Make a central connection between the chassis ground and the ground/protective ground
conductor system.
Ensure proper routing of lines when wiring (see sections 3.4.1 and 3.4.2)
•
Arrange the cabling in line groups.
(AC power cable, power supply lines, signal lines, data lines).
•
Always install AC power cables and signal or data lines in separate ducts or bunches.
•
Route the signal and data lines as closely as possible to grounded surfaces such as cabinet
elements, metal bars and cabinet panels.
Ensure that cable shields are properly secured (see section 3.4.3)
•
Data lines must be shielded. The shield should be connected at both ends.
•
Analog lines must be shielded. For the transfer of signals with low amplitudes, it may be
advisable to connect the shield at only one end.
•
Provide the line shields with a large-area connection to a shield/protective conductor bar
immediately after the cabinet inlet, and secure the shields with cable clamps. Route the
grounded shield as far as the module without interruption, but do not connect the shield there
again.
•
Ensure that the shield/protective ground bar has a low-impedance connection to the cabinet.
•
Use metal or metallized connector cases for shielded data lines.
Employ special EMC measures for particular applications (see section 3.4.4)
•
Fit quenching elements to all inductances which are not controlled by SIMATIC S5 modules.
•
Use incandescent bulbs for illuminating cabinets, and avoid fluorescent lamps.
•
Use suitable filters for all 24 V DC supplies.
Create a standard reference potential; ground all electrical apparatus if possible
•
Use specific grounding measures. Grounding of the control system is a protective and functional
measure.
•
System parts and cabinets with central controllers and expansion units should be connected to
the ground/protective conductor system in star configuration. This serves to avoid the creation of
ground loops.
•
In the case of potential differences between system parts and cabinets, install equipotential
bonding conductors of sufficient rating.
3-4
EWA 4NEB 812 6210-02
