Siemens SIMATIC C7-635, Manual

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Installing and Wiring the C7-635
3-23
C7-635 Control System
A5E00155581-04
Cabinet Design
Devices that could introduce interference signals from outside into the cabinet
must be placed far below the cabinet. The grounding terminal must be placed
immediately at the cabinet entrance to directly ground cables capable of carrying
interference signals. All shielded cables must be laid here with the shield. For
double-shielded signal lines, only the outer shield is to be laid here.
Long signal lines must be installed along the cabinet walls. It is important to use an
EMC-compliant cabinet construction to reduce disturbance variables. All chassis
ground connections in the cabinet are to be made with a large cable cross section
and laid over a large surface.
Analog devices located in the control cabinet must be isolated and grounded at a
point in the cabinet (use a copper strip).
The materials used should always contain the same type of metal (as a rule, do
not use aluminum due to the risk of oxidation).
All doors and plates (side walls, back wall, and ceiling) of the cabinet must be
connected at least three times with cabinet framework (short, unpainted
connections over a large surface).
Note
The following applies for systems that generate large amounts of
electrostaticenergy (such as textile machines and special construction machines):
The grounding conductors of the machine parts exposed to interference signals
are to be connected to a special functional ground separated from the central
grounding point of the cabinet (surface grounding with building construction,
sheathing).
Functional Ground
Connect the functional ground (see Figure 3-17) to the cabinet ground with a
cable lug and a cable with a minimum cross section of 4 mm
2
.
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