Wiring   
6.4 Wiring the power supply module and the CPU 
  S7-300, CPU 31xC and CPU 31x: Installation 
6-6  Operating Instructions, Edition 08/2004, A5E00105492-05 
 
 
 
Warning 
Reversing the polarity of the M and L+ terminals trips the internal fuse on your CPU. 
Always interconnect the M and L+ terminals of the power supply module and of the CPU.
 
6.  Close the front panels. 
The figure below illustrates the procedures described earlier. 
L1
N
L+
M
M
L+
I
M
L+
230V/120V
1
2
3
 
 
Key to numbers in the figure 
(1)  Strain relief of the power supply cable 
(2)  Connection cables between the PS and CPU 
(3)  Removable power supply connector 
 
 
 
Note 
The PS 307 power supply module is equipped with two additional 24 VDC terminals L+ and 
M for the supply to I/O modules.