Configuring An S7-300 With Ungrounded Reference Potential (Not Cpu 31Xc) - Siemens Simatic S7-300 CPU 31xC Series Installation And Operating Instructions Manual

Grounded reference potential of the CPU 31x
The figure shows an S7-300 configuration with grounded reference potential (factory state.)
1
The figure illustrates the following
(1)
(2)
(3)
Note
Do not pull out the grounding slide contact when you install an S7-300 with grounded
reference potential.
4.9.3

Configuring an S7-300 with ungrounded reference potential (not CPU 31xC)

Introduction
During installation of an S7-300 with ungrounded reference potential interference currents
are discharged to the ground conductor / to ground via an RC combination integrated in the
CPU.
Note
An S7-300 with a CPU 31xC cannot be configured ungrounded.
S7-300, CPU 31xC and CPU 31x: Installation
Operating Instructions, Edition 08/2004, A5E00105492-05
Grounding slide contact in grounded state
Ground of the internal CPU circuitry
The mounting rail
4.9 Electrical assembly, protective measures and grounding
L+ M
M
<100 nF
10M
2
3
Configuring
4-17