Mitsubishi Electric MELSEC iQ-R Series User Manual page 100

■Influence on the relay life by a connected load
An actual relay life can be substantially shorter than the relay life curve depending on the type of a connected load and the
characteristics of its inrush current.
Page 97 Relay life (contact switching life)
The inrush current generated by a connected load can lead to contact welding of the module. To prevent shortening of the
relay life and contact welding, take the following measures:
• Considering the possibility of a high inrush current, select a load so that the inrush current generated by the connected load
falls within the range of the rated current of the module.
• Connect a relay capable of withstanding the inrush current, outside the module.
The following table lists the relations between typical loads and each inrush current.
Select a load so that the inrush current, i, and rated current, io, fall within the range of the rated switching current described in
the module specifications. In some loads, the inrush current flows for a long time.
Load type Waveform
Inductive load Load of a solenoid
i
i: Inrush current
io: Rated current
t: 0.07 to 0.1 seconds
Lamp load Load of an incandescent lamp
i
t
i: Inrush current
io: Rated current
t: Approx. 0.33 seconds
Load of a fluorescent lamp
i
i: Inrush current
io: Rated current
t: within 10 seconds
6 INSTALLATION AND WIRING
98
6.1 Before Using the I/O Modules
io
t
io
io
t
Inrush current Waveform
i/rated current
io
Approx. 10 to 20 Load of an electromagnetic contactor
times
i
t
i: Inrush current
io: Rated current
t: 0.017 to 0.033 seconds (1 to 2 cycle)
Approx. 3 to 10 Load of a mercury lamp
times
i
t
i: Inrush current
io: Rated current
t: 180 to 300 seconds (3 to 5 minutes)

Approx. 5 to 10
times
io
io
Inrush current
i/rated current
io
Approx. 3 to 10
times
*1
Approx. 3 times
