Siemens Simatic S7-300 CPU 31xC Series User Manual

Configuring
4.9 Electrical assembly, protective measures and grounding
S7-300, CPU 31xC and CPU 31x: Installation
Operating Instructions, Edition 08/2004, A5E00105492-05
4-25
All CPUs except CPU 31xC
The figure below shows you the complete assembly of an S7-300 with TN-S mains supply
(does not apply to CPU 31xC). 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.
Cabinet
Profile rail
PS
CPU
SM
Signal modules
L1
N
L+
M
µP
AC
AC
AC
AC
DC
DC
L1
M
L2
L3
N
PE
Load circuit
24 to 230 V AC for AC modules
Load circuit
5 to 60 V DC for non-isolated DC modules
Load circuit
5 to 60 V DC for isolated DC modules
Low-voltage distribution
e.g. TN-S system (3 x 400 V)
Common grounding line in the cabinet
1
2
2
2
3
4
5
Table 4-11 Connecting the load voltage reference potential
The figure illustrates the following
(1) The main switch
(2) The short-circuit / overload protection
(3) The load current supply (galvanic isolation)
(4) The removable connection to the grounding conductor, for ground fault localization
(5) The grounding slide contact of the CPU (not CPU 31xC)

Siemens Simatic S7-300 CPU 31xC Series Specifications

General

Series	S7-300 CPU 31xC
Power Supply	24 V DC
Communication Interfaces	MPI, PROFIBUS DP
Programming Languages	LAD, STL, FBD, SCL
Operating Temperature	0°C to +60°C
Memory	48 KB - 512 KB
Dimensions	40 x 125 x 130 mm (varies by model)