Key To Example 1 - Siemens CPU 313C Hardware And Installation Manual

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The numbers in the following list refer to the numbers in the figure above.
Table 12-6
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1 Ground straps
2 Supporting bars
3 Mounting the rail
4 Signal cables
5 Cable clamp
6 Shielding busbar
7 Protective
conductor busbar
8 Cable to the
protective ground
system
(equipotential
ground)
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When operating your S7 in a low-noise environment that conform with permitted
ambient conditions (see Appendix $PELHQW FRQGLWLRQV), you can also mount your
S7 in frames or to the wall.
Interference coupling must be diverted to large metal surfaces. Therefore, always
mount standard profile/shielding/protective conductor rails on metal parts of the
construction. Steel sheet panels reference potential surfaces have been found
especially suitable for wall-mounting.
Provide a shielding busbar for connecting your cable shielding. This shielding
busbar can also be used as protective ground bar.
12-10

Key to example 1

If no large-surface metal-to-metal connections are available,
you must either interconnect inactive metal parts (e.g. cabinet
doors or mounting plates) or bond them to chassis ground using
ground straps. Use short ground straps with a large surface.
Interconnect the supporting bars on a large area to the cabinet
walls (metal-to-metal connection).
The mounting bar and rack must be interconnected with large-
area metal-to-metal connections.
Connect the shielding of signal cables on a large area of the
protective conductor/additional shielding busbar and fasten
them with cable clamps.
The cable clamp must cover a large area of the shielding braid
and ensure good contact.
Interconnect the shielding busbar on a large surface with the
supporting bars (metal-to-metal connection). The cable
shielding is terminated on the busbar.
Interconnect the protective conductor busbar on a large surface
with the supporting bars (metal-to-metal connection).
Interconnect the protective conductor busbar and the protective
ground system, using a separate cable (minimum cross-section
2
10 mm ).
Interconnect the cable on a large area with the protective
ground system (equipotential ground).
S7-300 Automation System, Hardware and Installation: CPU 31xC and CPU 31x
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A5E00105492-03