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
.
Inrush Current Restrictions
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 4-25 for the rated values of the items when the
CPU Rack is used.
Calculating the Effective Value of the I/O Power Supply Current
The formula to calculate the effective value of the I/O power supply current, Irms, is given below.
Irms= Ip
2
×
D+Ia
2
×
(1-D)
(D=
τ/T)
• Ip: Peak inrush current (A)
• Irms: Ef
fective value of I/O power supply current (A)
• Ia: Total current consumption from the I/O power supply (A)
• D: Inrush current duty
• t: Inrush current pulse width (s)
• T: Inrush current period (s)
4 Designing the Power Supply System
4-21
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
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