*1. The current consumption of the Additional I/O Power Supply Unit is not actually 0 A. However, a value of 0 A
is used in this calculation example.
In actual calculations, add the current consumption from the I/O power supply that is given in the NX-series
Data Reference Manual (Cat. No. W525).
l
Outline
Find the I/O power supply voltage of the NX Unit that is the farthest from the Additional I/O Power
Supply Unit 1. In this example, the I/O power supply voltage of Unit (5) is found.
l
Conditions
Assume that an I/O power supply voltage of 24.00 VDC is supplied to the I/O power supply termi-
nals on the Additional I/O Power Supply Unit 1.
l
Procedure
1 Use the following formula to calculate the total current consumption from the I/O power supply.
Total current consumption from the I/O power supply = (1) + (2) + (3) + (4) + (5)
= 0.0 A + 0.5 A + 0.5 A + 0.0 A + 2.0 A
= 3 A
2 Find the I/O power supply voltage and make sure that it is within the voltage specifications of
the I/O circuits of the NX Units and the connected external devices.
I/O power supply voltage at (5) = I/O power supply voltage on I/O power supply terminals − Voltage drop per
Unit × Number of Units passed through
= 24.00 V − 0.06 V × (5 − 1 Units)
= 23.76 V
Design to Separate the I/O Power Supply
If the I/O power supply voltages of the connected external devices are different, connect an Additional
I/O Power Supply Unit at the point where the I/O power supply voltage changes and then perform sim-
ilar calculations to design a system that meets the power supply conditions. The same method is used
to separate the power supply systems. Connect an Additional I/O Power Supply Unit at the point
where the power supply systems to be separated and then perform similar calculations to design the
overall system to meet the power supply conditions.
4-3-3
Designing the I/O Power Supply from External Sources
Unlike supplying power from the NX bus, there is no specific design method for supplying I/O power
from external sources.
Calculate the total current consumption from the I/O power supply for the NX Units to be supplied
power from an external source.
Refer to the user
’
s manuals of the NX Units for the total current consumption from the I/O power sup-
ply.
4-3-4
Designing I/O Power Supply for the Built-in I/O
The I/O power supply for built-in I/O is separated from NX bus, so there is no specific design method.
4 Designing the Power Supply System
4-19
NX-series NX1P2 CPU Unit Hardware User’s Manual (W578)
4-3 Designing the I/O Power Supply System
4
4-3-3 Designing the I/O Power Supply from External Sources
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