Siemens Simatic S7-200 System Manual page 30

Installing an S7-200 Micro PLC
Calculating a Sample Power Requirement
Table 2-1 shows a sample calculation of the power requirements for an S7-200 Micro PLC
that includes the following modules:
CPU 214 DC/DC/DC
Three EM 221 Digital Input 8 x DC 24 V expansion modules
Two EM 222 Digital Output 8 x Relay expansion modules
The CPU in this example provides sufficient 5 VDC current for the expansion modules;
however, it requires an additional power supply to provide the 24 VDC power requirement.
(The I/O requires 448 mA of 24 VDC power, but the CPU provides only 280 mA.) Appendix B
provides a blank power calculation table.
Table 2-1
CPU Power Budget
CPU 214 DC/DC/DC
System Requirements
CPU 214 DC/DC/DC
Three EM 221 expansion modules
Two EM 222 expansion modules
Total Requirement
Current Balance
Current Balance Total
2-16
Power Budget Calculations for a Sample Configuration
minus
3 x 60 mA =
2 x 80 mA =
equals
5 VDC
660 mA
5 VDC
BASE UNIT 14 input x 7 mA =
180 mA 3 x 60 mA =
160 mA 2 x 85 mA =
340 mA
5 VDC
320 mA
S7-200 Programmable Controller System Manual
C79000-G7076-C230-02
24 VDC
280 mA
24 VDC
98 mA
180 mA
170 mA
448 mA
24 VDC
[168 mA]