5 Designing the Power Supply System
5 - 14
NX-series EtherNet/IP Coupler Unit User’s Manual (W536)
the power supply systems are to be separated and then perform similar calculations to design the over-
all system to meet the power supply conditions.
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 supply.
This section describes the restrictions on inrush current from the I/O power supply that occurs when
connected external devices turn ON and OFF.
If inrush current to the I/O power supply occurs when a connected external device turns ON or OFF, do
not allow the effective value of the I/O power supply current to exceed the following rated values when
the inrush current is added to the current consumption from the I/O power supply.
• Maximum I/O power supply current
• Current capacity of power supply terminals for the I/O power supply
Do not allow the inrush current to exceed the values given in the following table.
The formula to calculate the effective value of the I/O power supply current, Irms, is given below.
• Ip: Peak inrush current (A)
• Irms: Effective value of I/O power supply current (A)
• Ia: Total current consumption from the I/O power supply (A)
• D: Inrush current duty
• τ: Inrush current pulse width (s)
• T: Inrush current period (s)
5-3-3 Designing the I/O Power Supply from External Sources
5-3-4 Restrictions on Inrush Current for ON/OFF Operation
Inrush Current Restrictions
Unit Model Peak value Pulse width
EtherNet/IP
Coupler Unit
NX-EIC202 50 A 1 s
Calculating the Effective Value of the I/O Power Supply Current
Irms= Ip
2
×D+Ia
2
×(1-D)
(D=
Ï„
/T)
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