Omron NX-ECC201 User Manual page 95

Calculating the Voltage Drop in the I/O Power Supply
Voltage drop occurs in the EtherCAT Slave Terminal due to the contact resistance at the points where
Units are connected to each other. Design the I/O power supply system to maintain the voltage specifi-
cations of the NX Unit I/O circuits and connected external devices even if the voltage of the I/O power
supply drops.
As shown in the following table, the voltage drop per Unit depends on the total current consumption
from the I/O power supply.
Total current consumption from the I/O
power supply
4 A
3 A
2 A
1 A
Here, the following Unit configuration example is used to show how to calculate the I/O power that is
supplied by the EtherCAT Coupler Unit. The same method can be used to calculate the I/O power sup-
ply from an Additional I/O Power Supply Unit.
Example:
EtherCAT Coupler Unit NX Units
Power Consumption of Individual Units
*1
(1): 0 A (Supplied from the NX bus.)
(2) and (3): 1.5 A each (Supplied from the NX bus.)
(4) and (5): 0 A (Supplied from external source.)
(6) and (7): 0.5 A each (Supplied from the NX bus.)
*1. The current consumption of the EtherCAT Coupler Unit is not actually 0 A. However, a value of 0 A is used in
this calculation example.
In actual calculations, use the current consumption from the I/O power supply that is given elsewhere in this
manual.
 Outline
Find the I/O power supply voltage of the NX Unit that is the farthest from the EtherCAT Coupler Unit.
In this example, the I/O power supply voltage of Unit (7) is found.
 Conditions
Assume that an I/O power supply voltage of 24.00 VDC is supplied to the I/O power supply terminals
on the EtherCAT Coupler Unit.
NX-series EtherCAT Coupler Unit User's Manual (W519)
0.08 V
0.06 V
0.04 V
0.02 V
● Total current consumption from the Units
that are supplied I/O power from the
EtherCAT Coupler Unit (total for (1) to
(7) = 4 A)
(1) (2) (2) (4) (5) (6)
I/O power
To external To external
supply
devices devices
(24 VDC)
5 Designing the Power Supply System
Voltage drop per Unit
● Units that are supplied I/O
power from the Additional I/O
Power Supply Unit
Additional I/O Power Supply Unit
(7)
To external
devices
I/O power
supply
(24 VDC)
End Cover
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