Siemens S5-135U/155U - Manual (Page 32)

3-6
System Manual
C79000-G8576-C199-06
3.1.2 The 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 3.2).
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Make a large-area low-impedance interconnection of all inactive metal
parts.
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For screw connections on painted and anodized metal parts, either use
special contact washers or remove the insulating protective layers.
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If possible, do not use aluminum parts. Aluminum oxidizes easily and is
therefore less suitable for grounding.
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Make a central connection between the chassis ground and the
ground/protective ground conductor system.
Ensure proper routing of lines when wiring (see Sections 3.3.1 and 3.3.2).
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Arrange the cabling in line groups. (AC power cable, power supply lines,
signal lines, data lines)
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Always install AC power cables and signal or data lines in separate ducts
or bunches.
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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 3.3.3).
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Data lines must be shielded. The shield should be connected at both ends.
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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.
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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.
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Ensure that the shield/protective ground bar has a low-impedance
connection to the cabinet.
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Use metal or metallized connector cases for shielded data lines.
Installation Guidelines