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4 Designing the Power Supply System
NX-series NX1P2 CPU Unit Hardware User’s Manual (W578)
4-4 Selecting External Power Supplies and Protective Devices
4
4-4-1 Selecting the Unit Power Supply
Blocks
A block consists of the Unit that supplies the NX Unit power and the range of Units to which that Unit
supplies the NX Unit power. For example, in the configuration in the following figure there are two
blocks in the CPU Rack: the block with the CPU Unit and the block with the Additional NX Unit
Power Supply Unit.
The total of the required Unit power supply capacity for these two blocks is the required power sup-
ply capacity of the Unit power supply for the CPU Rack.
Precautions for Correct Use
Use the same Unit power supply to supply the Unit power to the one CPU Rack. If you supply
power from different Unit power supplies, differences in electrical potential may cause unex-
pected currents in the NX Unit power supply, which may result in failure or malfunction.
Calculation Example
This section provides a calculation example for the configuration example that is given in 4-2-2 Cal-
culation Example for the NX Unit Power Supply on page 4-8.
• The NX Unit power supply efficiency of the CPU Unit is 80%.
In this configuration example, there is only one block, the CPU Unit block.
Required power supply capacity of Unit power supply to CPU Rack
= Required Unit power supply capacity of CPU Unit block
= (CPU Unit power consumption + Total power consumption from NX Unit power supply of NX
Units connected to CPU Unit)/NX Unit power supply efficiency of CPU Unit
= 7.05 W + (0.85 W × 1 + 0.90 W × 4 + 1.20 W × 3)/0.8
= Approx. 17.1 W
Name Model Quantity Power consumption/Unit
CPU Unit NX1P2-1140DT 1 7.05 W
Additional I/O Power Supply
Unit
NX-PF0630 1 0.85 W
Digital Input Unit NX-ID3317 4 0.90 W
Relay Output Unit NX-OC2633 3 1.20 W
Internal
circuits
End
Cover
NX Unit power supply
Internal
circuits
Internal
circuits
Internal
circuits
Internal
circuits
Internal
circuits
Internal
circuits
Internal
circuits
Internal
circuits
NX Unit power supply
Internal
power
supply
circuit
Unit power supply terminals
CPU Unit block Additional NX Unit Power Supply Unit block
NX Unit connected to the
CPU Unit
NX Unit connected to the Additional
NX Unit Power Supply Unit
Additional NX Unit
Power Supply Unit
Internal
power
supply
circuit
Unit power
supply
(24 VDC)
Unit power supply terminals
NX-series
NX1P2 CPU
Unit
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