Precautions for Correct Use
Select an I/O power supply with sufficient capacity by considering the inrush current when the
power is turned ON. Sometimes, the I/O power supply may not be turned ON caused by inrush
current when the power is turned ON.
Calculation Example for Power Supply Capacity of I/O Power Supply
An example of calculating the required power supply capacity of the I/O power supply is given be-
low.
a.
Configuration and Conditions
I/O power
supply
(24 VDC)
Additional I/O
Power Supply Unit
NX-PF0730
End Cover
Digital Input
Unit
NX-ID3317
Connected
input
devices
Digital
Output Unit
NX-OD3121
Connected
output
devices
(loads)
Item Condition
I/O power supply voltage 24 VDC
Inputs Number of inputs used (that turn ON si-
multaneously)
4 points
Current consumption of connected input
devices
50 mA/point
Outputs Number of outputs (that turn ON simulta-
neously)
4 points
Load current of connected loads 125 mA/point
Current consumption of connected output
devices
50 mA/point
I/O power is supplied to the NX-ID3317 and NX-OD3121 from the NX bus.
b. Unit Specifications
Model
Current consumption from I/O power
supply
Input current
NX-PF0730 10 mA ---
NX-ID3317 0 mA 6 mA/point
NX-OD3121 10 mA ---
c. Calculations
The current consumption from the I/O power supply for each Unit is calculated as follows.
4 Installation and Wiring
4-36
NX-series System Units User's Manual (W523)
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