Technical specifications
8.3 Current consumption and power loss
TIM DNP3
System Manual, 12/2015, C79000-G8976-C253-04
305
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 8- 4 Current consumption and power loss balance
Current consumption
from S7-300 backplane
bus
Current consumption from 24
V load power supply
CPU 314 - 700 mA 8 W
2 digital input modules
(2 x 25 mA) = 50 mA (2 x 25 mA) = 50 mA (2 x 3.5 W) = 7 W
1 relay module
SM 322; DO 8 x AC 230 V/5 A
40 mA 125 mA 4.2 W
1 analog input module
60 mA 200 mA 1.3 W
1 analog output module
60 mA 135 mA 3 W
The following results can be derived from the table above:
1. Current consumption from the S7--300 backplane bus:
The current consumption of the signal and TIM modules from the backplane bus amounts
to a total 410 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 load power supply:
The current consumption of the signal, TIM and modem modules from the 24 V load
power supply amounts to approx. 1.6 A. All additional loads must also be taken into
account. Depending on this, you can then select the PS 307 power supply.
Check whether the assumed PS 307 with 2 A output current is adequate for this example.
3. Power loss:
The power loss of the S7-300 configuration amounts to a total of 42.6 W.
The power loss of all the components used in a cabinet (including the S7-300
configuration with 42.6 W) must not exceed the maximum power that the cabinet can
discharge.
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.
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