Grounding Concept For The S7-300 (Excluding Cpu 31Xc) - Siemens CPU 313C Hardware And Installation Manual

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The figure below shows you the complete assembly of an S7-300 with TN-S mains
supply (does not apply to CPU 31xC).
Apart from powering the CPU, the PS 307 also supplies the load current for the
24 VDC modules.
Note: The arrangement displayed does not correspond with the physical
arrangement; it was merely selected to give you a clear overview.
L1
L2
L3
N
PE
1
Figure 5-12 Grounding concept for the S7-300 (excluding CPU 31xC)
Table 5-11
Main switch

 Short-circuit/overload protection
 Load power supply (galvanic isolation)
Disconnectable connection to protective conductor in order to localize ground faults

 Grounding slide contact of the CPU (not CPU 31xC)
S7-300 Automation System, Hardware and Installation: CPU 31xC and CPU 31x
A5E00105492-03
Rail
L1
N
3
AC
AC
AC
DC
AC
DC
Connection of the load voltage reference potential
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Low-voltage distribution
e. g. TN-S system (3 x 400 V)
Cabinet
CPU
PS
µP
L +
M
M
5
Ground bus in cabinet
2
AC 24 to 230 V load circuit for AC modules
2
DC 5 to 60 V load circuit for
4
non-isolated DC modules
2
DC 5 to 60 V load circuit for
isolated DC modules
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Signal modules
5-27