Basic Rules - Siemens SIMATIC RF 300 System Manual

RF 300 system planning
4.6 EMC Guidelines
4.6.3

Basic rules

It is often sufficient to follow a few elementary rules in order to ensure electromagnetic
compatiblity (EMC). The following rules must be observed when erecting a control cabinet:
Shielding by enclosure
• Protect the programmable logic controller against external interference by installing it in a
• Use metal plates to shield the programmable logic controller against electromagnetic
• Use metal connector housings to shield data conductors.
Laminar ground connection
• Bond all passive metal parts to chassis ground, ensuring large-area and low-HF-
• Establish a large-area connection between the passive metal parts and the central
• Don't forget to include the shielding bus in the chassis ground system. That means the
• Aluminium parts are not suitable for ground connections.
Plan the cable installation
• Break the cabling down into cable groups and install these separately.
• Always route high-voltage and signal cables through separated ducts or in separate
• Feed the cabling into the cabinet from one side only and, if possible, on one level only.
• Route the signal cables as close as possible to chassis surfaces.
• Twist the feed and return conductors of separately installed cables.
Shielding for the cables
• Shield the data cables and connect the shield at both ends.
• Shield the analog cables and connect the shield at one end, e.g. on the drive unit.
• Always apply large-area connections between the cable shields and the shielding bus at
• Feed the connected shield through to the module without interruption.
• Use braided shields, not foil shields.
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housing or enclosure. The housing or enclosure must be connected to the chassis
ground.
fields.
impedance contact.
grounding point.
actual shielding busbars must be connected to ground by large-area contact.
bundles.
the cabinet inlet and make the contact with clamps.
System Manual, 05/2005, (4)J31069 D0166-U001-A1-7618, --
RF 300