Mitsubishi MELESEC-ST User Manual page 76

7 I/O MODULES
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(b) Measures against inrush current
Relay life significantly varies depending on its load type the characteristics of its
inrush current.
Take following measures since the inrush current may cause contact welding.
• In case of an increase in inrush current, select a load so that the inrush current
will be within the rated current of the module.
• Connect the relay that can sustain inrush current outside the module.
1) Inductive load
Inrush current of inductive load may flow 20 times as large as the rated
current depending on a load.
[Load of a solenoid]
i io 10 to 20 times
i
0.07 to 0.1
seconds
[Load of a magnetic contactor]
i io 3 to 10 times
i
0.017 to 0.033 seconds
(1 to 2 cycles)
io
i: Inrush current
io: Rated current
io
i: Inrush current
io: Rated current
MELSEC-ST
7 - 16