Siemens SIMATIC C7-613, Manual

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Installing and Wiring the C7-613
2-18
C7-613 Control System
A5E00138934-03
Control cabinet installation
Devices which may introduce external interference to the control cabinet should be
mounted in the bottom area of the cabinet. Always mount the grounding busbar at
a position close to the cable inlet, so that you can connect noise-carrying cables
directly to earth potential. All shielded cables are to be laid here with the shield.
Terminate only the outer shielding of cables equipped with double shielding.
Route longer signal cables along the cabinet walls. It is important to use an
EMC-compliant cubicle construction to reduce disturbance variables. All ground
connections of the cabinet must be interconnected by means of cables with a large
conductor cross-section, and with appropriate contact to a large area of the steel
chassis.
Analog devices installed in the control cabinet should be electrically isolated, and
bonded at least once to chassis ground by means of a copper braid.
Always use metal materials of the same grading. Never use aluminum, because of
the risk of oxidation.
Connect all the doors and sheet-metal parts (side walls, rear walls and cover) of
the cabinet at least three times to the cabinet frame. Ensure that connections are
short, large-area and free of paints.
Note
In plants generating a high electrostatic discharge level (e.g. in textile processing
systems, or particular construction machinery), always connect machine parts
which are subject to interference to a separate functional ground, i.e. bond the
central grounding busbar of the cabinet to a separate equipotential earth (surface
grounding to the building construction, steel reinforcement).
Functional ground
Connect the functional ground (see Fig. 2-13) to chassis ground of the
control cabinet, using a cable lug on a cable with a minimum conductor
cross-section of 4 mm
2
.