Appendix
A.1 General rules and regulations for S7-300 operation
S7-300, CPU 31xC and CPU 31x: Installation
A-2
Operating Instructions, Edition 08/2004, A5E00105492-05
Mains voltage
The table below shows what you have to watch with respect to the mains voltage.
Table A-2
Mains voltage
In the case of ...
the ...
Stationary systems or systems without all-pole
mains disconnect switch
building installation must contain a mains
disconnect switch or a fuse.
Load power supplies, power supply modules
set rated voltage range must correspond to local
mains voltage.
All circuits of the S7-300
rated mains voltage fluctuation / deviation must
lie within the permitted tolerance (refer to
Technical Data of S7-300 modules).
24 VDC power supply
The table below shows what you must observe for the 24 VDC power supply.
Table A-3
Protection against external electrical interference
In the case of ...
you need to observe ...
Buildings
external lightning protection
24 VDC power supply cables, signal
cables
internal lightning protection
Install lightning protection
(e.g. lightning conductors).
24 VDC power supply
safe (electrical) extra-low voltage isolation
Protection against external electrical interference
The table below shows how you must protect your system against electrical interference or
faults.
Table A-4
Protection against external electrical interference
In the case of ...
Make sure that ...
All plants or system in which the S7-300 is
installed
the plant or system is connected to a protective
conductor for the discharge of electromagnetic
interference.
Supply / signal / bus cables
the cable routing and installation is correct.
Signal and bus cables
a cable/conductor break does not cause
undefined plant or system states.