Siemens S7-300 - Grounding Concept for the S7-300 with CPU 31 X

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S7-300 Automation System, Hardware and Installation: CPU 312IFM - 318-2 DP
A5E00203919-01
5-29
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The figure below shows you an overall S7-300 configuration with TN-S power
supply. 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
Ground bus in cabinet
PS
CPU
SM
Signal modules
L1
N
L+
M
µP
AC
AC
AC
AC
DC
DC
L1
M
L2
L3
N
PE
1
Low-voltage distribution
e. g. TN-S system (3 x 400 V)
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
3
2
2
2
5
4
Figure 5-12 Grounding concept for the S7-300 with CPU 31 x
Table 5-11 Connection of the load voltage reference potential
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 The main switch
 Short-circuit/overload protection
 The load current supply (galvanic isolation)
 The removable connection to the equipment grounding conductor cable for ground
fault localization
 Grounding brackets of the CPU (removable jumper)