Overview: Grounding; Table 4-10 Connecting The Load Voltage Reference Potential - Siemens Simatic S7-300 CPU 31xC Series Installation And Operating Instructions Manual

Configuring
4.9 Electrical assembly, protective measures and grounding
4.9.6

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 layout of the power connections does not
correspond with their physical arrangement; it was merely selected to give you a clear
overview.
L1
L2
L3
N
PE
1
Table 4-10
The figure illustrates the following
(1)
(2)
(3)
(4)
4-24
Profile rail
3
AC
AC
AC
DC
AC
DC
Connecting the load voltage reference potential
The main switch
The short-circuit / overload protection
The load current supply (galvanic isolation)
This connection is made automatically for the CPU 31xC
Low-voltage distribution
e.g. TN-S system (3 x 400 V)
Cabinet
CPU
PS
4
1
µP
L1
L +
M
N
Common grounding line in the cabinet
2
Load circuit
24 to 230 V AC for AC modules
2
Load circuit
4
5 to 60 V DC non-isolated DC modules
2
Load circuit
5 to 60 V DC for isolated DC modules
S7-300, CPU 31xC and CPU 31x: Installation
Operating Instructions, Edition 08/2004, A5E00105492-05
SM
Signal modules