Siemens Simatic S7-300 CPU 31xC Series - Page 44

Configuring
4.9 Electrical assembly, protective measures and grounding
S7-300, CPU 31xC and CPU 31x: Installation
4-20 Operating Instructions, Edition 08/2004, A5E00105492-05
Example: Assembly with CPU 31xC and isolated modules
The figure below shows an example of such a configuration: A CPU 31xC with isolated
modules. The CPU 31xC (1) is automatically grounded.
N
L1
L+
M
PS
S7-300 CPU
µP
L1
N
M
external
L+
U
internal
M
internal
Data
L1
N
DI
DO
PE
Common grounding
line in the cabinet
230 V AC
load power supply
24 V DC load power supply
1
Common potential modules
In a configuration containing modules with common potential, the reference potentials of the
control circuit (M
internal
) and analog circuit (M
analog
) are not galvanically isolated.