Calculating A Power Budget - Siemens SIMATIC S7-1200 System Manual
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Also See for SIMATIC S7-1200:
- Function manual (527 pages) ,
- Manual (364 pages) ,
- System manual (338 pages)
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Calculating a power budget
The CPU has an internal power supply that provides power for the CPU itself, for any
expansion modules, and for other 24 V DC user power requirements.
There are four types of expansion modules:
● Signal modules (SM) are installed on the right-side of the CPU. Each CPU allows a
maximum number of signal modules possible without regard to the power budget.
– CPU 1214C, CPU 1215C and CPU 1217C allows 8 signal modules
– CPU 1212C allows 2 signal modules
– CPU 1211C allows no signal modules
● Communication modules (CM) are installed on the left-side of the CPU. A maximum of 3
communication modules is allowed for any CPU without regard to the power budget.
● Signal boards (SB), communications boards (CB), and battery boards (BB) are installed
on top of the CPU. A maximum of 1 signal board, communication board, or battery board
is allowed for any CPU.
Use the following information as a guide for determining how much power (or current) the
CPU can provide for your configuration.
Each CPU supplies both 5 V DC and 24 V DC power:
● The CPU provides 5 V DC power for the expansion modules when an expansion module
is connected. If the 5 V DC power requirements for expansion modules exceed the power
budget of the CPU, you must remove expansion modules until the requirement is within
the power budget.
● Each CPU has a 24 V DC sensor supply that can supply 24 V DC for local input points or
for relay coils on the expansion modules. If the power requirement for 24 V DC exceeds
the power budget of the CPU, you can add an external 24 V DC power supply to provide
24 V DC to the expansion modules. You must manually connect the 24 V DC supply to
the input points or relay coils.
S7-1200 Programmable controller
System Manual, V4.2, 09/2016, A5E02486680-AK
WARNING
Connecting an external 24 V DC power supply in parallel with the DC sensor supply can
result in a conflict between the two supplies as each seeks to establish its own preferred
output voltage level.
The result of this conflict can be shortened lifetime or immediate failure of one or both
power supplies, with consequent unpredictable operation of the PLC system.
Unpredictable operation could result in death, severe personal injury and/or property
damage.
The DC sensor supply on the CPU and any external power supply should provide power
to different points. A single connection of the commons is allowed.
B
1555
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