An Example - Calculation Of Power Supply - Weidmuller SAI Active Universal Pro Series Manual

Project Planning with the Universal Pro
Voltage drop / max. expansion
The maximum expansion of the sub-bus system de-
pends on four factors:
• The number of stations
• The distance between stations
• The current load of each participant and there in-
puts
• The resistance of the wires in use
The following formula results:
Voltage drop of the line =
current consumption of module x (line resistance x
line length x 2)
3.3 An example - calculation of
power supply
A sub-bus system should be set up for 45 sensors
and 14 actuators. The extension distance is 30 m.
No. Cat. No.
1 1938610000
2 1938680000
3 1938610000
4 1938610000
5 1938640000
6 1938610000
7 1938640000
8 1938610000
9 1938610000
Table 3 Current consumption of the modules
18
Total voltage drop =
voltage drop of line 1 + voltage drop of line 2 + volt-
age drop of line x
Voltage on last module =
Supply voltage to gateway I/O - 0.9V - total voltage
drop
Result:
When voltage to last module is greater then 18V DC
= Okay
When voltage to last module is less than 18V DC =
Not okay
We have made available a software tool to help you
calculate the residual current and voltage drop. It
can be downloaded from the Weidmueller home-
page at www.weidmueller.com.
The following modules have been selected:
1 x 1938550000 Gateway IO Module 16DI M12
6 x 1938610000 Extension IO Module 8DI M12
2 x 1938640000 Extension IO Module 8DI/DO M12
1 x 1938680000 Extension I/O Module 8DO M12 2A
All sensors consume 10 mA current each.
Current for module
50 mA
50 mA
50 mA
50 mA
50 mA
50 mA
50 mA
50 mA
50 mA
Current for sensors
6 x 10 mA = 60 mA
6 x 10 mA = 60 mA
6 x 10 mA = 60 mA
4 x 10 mA = 40 mA
6 x 10 mA = 60 mA
4 x 10 mA = 40 mA
6 x 10 mA = 60 mA
6 x 10 mA = 60 mA
Total current
110 mA
50 mA
110 mA
110 mA
90 mA
110 mA
90 mA
110 mA
110 mA
5663600000/1.4/09.09