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4 Designing the Power Supply System
NX-series NX1P2 CPU Unit Hardware User’s Manual (W578)
4-3 Designing the I/O Power Supply System
4
4-3-5 Restrictions on Inrush Current for ON/OFF Operation
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
Also, maintain the peak inrush current 20 A maximum and maintain the pulse width 1 s maximum.
Refer to 4-4-3 Selecting Protective Devices on page 4-21 for the rated values of the items when the
CPU Rack is used.
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)
4-3-5 Restrictions on Inrush Current for ON/OFF Operation
Inrush Current Restrictions
Calculating the Effective Value of the I/O Power Supply Current
Irms= Ip
2
×D+Ia
2
×(1-D)
(D=
τ
/T)
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