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4 Installation and Wiring
NX-series Digital I/O Unit User’s Manual (W521)
4-2 Power Supply Types and Wiring
4
4-2-2 Calculating the Total Current Consumption from I/O Power Supply
The total current consumption of I/O power supplied from the NX bus must be within the range of the
maximum I/O power supply current of the Communications Coupler Unit or the Additional I/O Power
Supply Unit. However, for a CPU Rack, the specification for the maximum I/O power supply current is
restricted regardless of the model of the Additional I/O Power Supply Unit. Refer to the hardware user’s
manual for the CPU Unit to which NX Units are connected for information on the restrictions for the
CPU Rack.
To confirm this and to calculate the I/O power supply capacity, calculate the total current consumption
from I/O power supply from the NX bus.
The total current consumption from I/O power supply from the NX bus is the total sum of current con-
sumption from I/O power supply of the NX Unit that supplies the I/O power from the NX bus, the current
consumption of each applicable I/O circuit, and current consumption of any connected external
devices.
Note that the current consumption from I/O power supply indicated in the data sheet for each Unit type
does not include the load current of any external connection load and current consumption of any con-
nected external devices.
The total current consumption from I/O power supply of the Digital I/O Units is calculated as follows.
z Total Current Consumption from I/O Power Supply of the Digital Input Units
= (Current consumption from I/O power supply of the Digital Input Units) + (Input current of the Digi-
tal Input Units × Number of input points used) + (Total current consumption of connected external
devices)
z Total Current Consumption from I/O Power Supply of the Digital Output Units
= (Current consumption from I/O power supply of the Digital Output Units) + (Total load current of
connection load) + (Total current consumption of connected external devices)
Refer to A-1 Data Sheet on page A-2 for the current consumption from I/O power supply for each Digital
I/O Unit model and input current for each Digital Input Unit model.
There are no above confirmations if you use the NX Unit that supplies the I/O power from external
source.
Use the total current consumption from I/O power supply from external source and the total current con-
sumption from the I/O power supply from the above NX bus together to calculate the I/O power supply
capacity.
Use the I/O power supply current for the CPU Rack of the NX-series NX1P2 CPU Unit at 4 A or
less. Using the currents that are outside of the specifications may cause failure or damage.
4-2-2 Calculating the Total Current Consumption from I/O Power Sup-
ply
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