Configuring
S7-300 Automation System, Hardware and Installation: CPU 31xC and CPU 31x
5-26 A5E00105492-03
5.8.6 Overview: Grounding
CPU 31xC
The figure below shows you the complete assembly of an S7-300 with CPU 31xC
with a power supply from TN-S mains.
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.
Cabinet
Rail
PS
CPU
SM
L1
N
L+
M
µP
AC
AC
AC
AC
DC
DC
L1
L2
L3
N
PE
1
Low-voltage distribution
e. g. TN-S system (3 x 400 V)
Ground bus in cabinet
AC 24 to 230 V load circuit for
AC modules
DC 5 to 60 V load circuit for
non-isolated DC modules
DC 5 to 60 V load circuit for
isolated DC modules
Signal modules
1
3
2
2
2
4
Figure 5-11 Grounding concept for the S7-300 with CPU 31xC
Table 5-10 Connection of the load voltage reference potential
The diagram illustrates under number
(1) Main switch
(2) Short-circuit/overload protection
(3) Load power supply (galvanic isolation)
(4) This connection is automatically generated for the CPU 31xC
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