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Technical specifications
6.4 Current consumption and power loss of the SINAUT ST7 components
Calculation of the current and power loss balance
The following table contains the power consumption and loss balance for the S7- 300
configuration described above. This current consumption and power loss balance does not
include any actuators connected to the outputs.
Table 6- 2
Current consumption and power loss balance
Module
Power supply PS 307; 2 A
CPU 314
2 digital input modules
SM 321; DI 16 x DC 24 V
1 relay module
SM 322; DO 8 x AC 230 V/5 A
1 analog input module
SM 331; AI 8 x 12 bits
1 analog output module
SM 332; AO 2 x 12 bits
1 communications module
TIM 4R
1 modem MD3
Total:
Result
The following results can be derived from the table above:
1. Current consumption from S7-300 backplane bus:
The current consumption of the signal and TIM modules from the backplane bus amounts
to a total of 270 mA. It does not therefore exceed the 1.2 A that the CPU 314 can supply
to the backplane bus.
2. Current consumption from the 24 V power supply:
The current consumption of the signal. TIM and modem modules from the 24 V load
power supply amounts to approx. 1.9 A. All additional loads must also be taken into
account. Depending on this, you can then select the PS 307 power supply. The PS 307
unit with 2 A output current would probably be not quite adequate for this example.
3. Power loss:
The power loss of the S7-300 configuration amounts to a total of 50.6 W.
The power loss of all the components used in a cabinet (including the S7-300
configuration with 50.6 W) must not exceed the maximum suppliable power of the
cabinet.
Note
When planning the dimensions of the cabinet, make sure that the temperature in the
cabinet does not exceed the permitted maximum of 60°C even when the temperature
outside the cabinet is high.
248
Current consumption
from S7-300 backplane
bus
-
-
(2 x 25 mA) = 50 mA
40 mA
60 mA
60 mA
60 mA
-
270 mA
Current consumption from 24
V load power supply
-
700 mA
(2 x 25 mA) = 50 mA
125 mA
200 mA
135 mA
500 mA
200 mA
1910 mA
System Manual, 09/2016, C79000-G8976-C178-10
Power loss
10 W
8 W
(2 x 3.5 W) = 7 W
4.2 W
1.3 W
3 W
12.3 W
4.8 W
50.6 W
SINAUT ST7 station control system
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