Calculating A Sample Power Requirement; Power Budget Calculations For A Sample Configuration - Siemens SIMATIC S7-200 System Manual

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:
CPU 224 AC/DC/Relay
3 each EM 223 8 DC In/8 Relay Out
1 each EM 221 8 DC In
This installation has a total of 46 inputs and 34 outputs.
The CPU in this example provides sufficient 5 VDC current for the expansion
modules, but does not provide enough 24 VDC current from the sensor supply for
all of the inputs and expansion relay coils. The I/O requires 400 mA and the CPU
provides only 280 mA. This installation requires an additional source of at least
120 mA at 24 VDC power to operate all the included 24 VDC inputs and outputs.
Table 2-1
CPU Power Budget
CPU 224 AC/DC/Relay
System Requirements
CPU 224, 14 inputs
3 EM 223, 5 V power required
1 EM 221, 5V power required
3 EM 223, 8 inputs each
3 EM 223, 8 relay coils each
1 EM 221, 8 inputs each
Total Requirements
Current Balance
Current Balance Total
S7-200 Programmable Controller System Manual
A5E00066097-02

Power Budget Calculations for a Sample Configuration

minus
3 * 80 mA =
1 * 30 mA =
equals
Installing an S7-200 PLC
5 VDC
660 mA
5 VDC
14 * 4 mA =
240 mA
30 mA
3 * 8 * 4 mA =
3 * 8 * 9 mA =
8 * 4 mA =
270 mA
5 VDC
390 mA
24 VDC
280 mA
24 VDC
56 mA
96 mA
216 mA
32 mA
400 mA
24 VDC
[120 mA]
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