Omron PROFINET NX-PNC202, User Manual

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5 Designing the Power Supply System
5 - 12
NX-series PROFINET Coupler Unit User’s Manual (W623)
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Calculation Examples
Examples of calculating the current consumption from the IO power supply are given below for a
Digital Input Unit and Digital Output Unit.
Voltage drop occurs in the Profinet IO Device Terminal due to the contact resistance at the points where
Units are connected to each other. Design the IO power supply system to maintain the voltage specifi-
cations of the NX Unit IO circuits and connected external devices even if the voltage of the IO power
supply drops.
As shown in the following table, the voltage drop per Unit depends on the total current consumption
from the IO power supply. However, the total current consumption from the IO power supply must not
exceed the maximum IO power supply current of the Unit that supplies the IO power.
Here, the following Unit configuration example is used to show how to calculate the IO power that is
supplied by the PROFINET Coupler Unit. The same method can be used to calculate the IO power sup-
ply from an Additional IO Power Supply Unit.
Current consumption between
the NX Units and the connected
external devices
This is the current that is consumed between the NX Units and the con-
nected external devices.
For example, this is the current consumed by a Digital Input Unit to supply
power to photoelectric sensors or to turn ON the input circuits in the Digital
Input Unit.
The current consumption depends on the type of IO circuit in the NX Unit, the
number of IO points that are used, and the current consumption of the con-
nected external device. It must be calculated for each NX Unit.
Current consumption of Digital
Input Unit
= Current consumption from IO power (Input current × Number
of inputs used) + Total current consumption of connected input devices
Current consumption of Digital
Output Unit
= Current consumption from IO power Total load current of con-
nected loads + Total current consumption of connected output devices
Calculating the Voltage Drop in the IO Power Supply
Total current consumption from the IO power supply Voltage drop per Unit
10 A 0.20 V
8 A 0.16 V
6 A 0.12 V
4 A 0.08 V
3 A 0.06 V
2 A 0.04 V
1 A 0.02 V
Current consumption item Description