Wiring the S7-400
4-17
S7-400 and M7-400 Programmable Controllers Hardware and Installation
A5E00069481-04
Interference-Free Configuration for Remote Connections
If you connect the CR and ER via suitable interface modules (send IM and receive
IM), normally no particular shielding and grounding need be implemented.
Special shielding and grounding may become necessary if you operate your
system in an environment with an extremely high level of interference. In that case,
observe the following points:
•
In the cabinet, connect the cable shields to the shield bus immediately after
entry.
– Strip the outer cable insulation in the region of the shield bus without
damaging the braided shield.
– Ensure that the braided shield has the greatest possible contact area on the
shield bus, for example, with metal hose clamps surrounding the shield over
a large area.
•
Connect the shield bus(es) over a large area to the frame or cabinet wall.
•
Connect the shield bus(es) to the chassis ground.
In a remote connection, ensure that the VDE regulations for laying the protective
ground are not infringed.
Figure 4-8 shows the methods described here. If the permissible potential
difference between grounding points is exceeded, you must install an equipotential
bonding conductor (copper conductor with a cross-section of
16 mm
2
).
CR
ER
Send IM
Receive IM
Î
Î
Î
ÎÎ
ÎÎ
ÎÎ
Shield/
protective
ground bar
< 7 V
Figure 4-8
Shielding and Grounding the Connecting Cable for a Remote Connection
Special Cases
For remote connections, you must use precut/preassembled connecting cables of
fixed length. When the connecting cables are laid, therefore, there may be excess
lengths. These must be coiled with a bifilar winding and deposited.
