Network Router User Manual
Assembling and Installing Systems
A-7
Automation System S7-400 Hardware and Installation
A5E00850741-01
Five Basic Rules for Ensuring Electromagnetic Compatibility
In many cases, you can ensure electromagnetic compatibility by observing the
following five basic rules:
Rule 1: Large Area Grounding
When installing the programmable controllers, provide large-area good quality
grounding of the inactive metal parts (see Section A.3).
• Make a large-area low-impedance connection of all inactive metal parts to
chassis ground.
• For screw connections on painted or anodized metal parts, either use s pecial
contact w ashers or remove the insulating protective layers from the contact
points.
• If possible, do not use aluminum parts for grounding. Aluminum oxidizes easily
and is therefore less suitable for grounding.
• Make a central connection between chassis ground and the ground/protective
ground conductor system.
Rule 2: Correct Cable Routing
Ensure proper routing of lines when wiring (see Sections A.7 and A.8).
• Arrange the cabling in line groups (AC power cables, power supply cables,
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.
Rule 3: Secure Cable Shields
Ensure that cable shields are properly secured (see Section 4.9).
• Only use shielded data lines. The shield must have a large-area connection to
ground at each end.
• Analog lines must always be shielded. For the transfer of signals w ith low
amplitudes, it may be advisable to connect the shield to ground at only one end.
• Provide the line shields with a large-area connection to a shield/protective
ground bar immediately after the cabinet inlet, and secure the s hields with cable
clamps. Route the grounded shield as far as the module without interruption, but
do not ground it there again.
• There must be a low-impedance connection between shield/protective ground
bar and cabinet/housing.
• Use metal or metallized connector cases for shielded data lines.