Siemens S7-1200 System Manual page 987

Table B- 1 Sample power budget
CPU power budget
CPU 1214C AC/DC/Relay
System requirements
CPU 1214C, 14 inputs
1 SB 1223 2 x 24 VDC Input/ 2 x
24 VDC Output
1 CM 1241 RS422/485, 5 V power
3 SM 1223, 5 V power
1 SM 1221, 5 V power
3 SM 1223, 8 inputs each
3 SM 1223, 8 relay coils each
1 SM 1221, 8 inputs each
Total requirements
Current balance
Current balance total
Form for calculating your power budget
Use the following table to determine how much power (or current) the S7-1200 CPU can
provide for your configuration. Refer to the technical specifications (Page 829) for the power
budgets of your CPU model and the power requirements of your signal modules.
Table B- 2 Calculations for a power budget
CPU power budget
System requirements
Total requirements
Current balance
Current balance total
S7-1200 Programmable controller
System Manual, 03/2014, A5E02486680-AG
5 VDC
1600 mA
Minus
5 VDC
-
50 mA
220 mA
3 * 145 mA = 435 mA
1 * 105 mA = 105 mA
-
-
-
810 mA
Equals
5 VDC
790 mA
5 VDC
Minus
5 VDC
Equals
5 VDC
Calculating a power budget
24 VDC
400 mA
24 VDC
14 * 4 mA = 56 mA
2 * 4 mA = 8 mA
-
-
3 * 8 * 4 mA = 96 mA
3 * 8 * 11 mA = 264 mA
8 * 4 mA = 32 mA
456 mA
24 VDC
(56 mA)
24 VDC
24 VDC
24 VDC
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