External Wiring Precautions - Mitsubishi FX3G SERIES User Manual

FX Series Programmable Controllers
3G
User's Manual - Hardware Edition

12.2.3 External wiring precautions

1. Protection circuit for load short-circuits
A short-circuit at a load connected to an output terminal could
cause burnout at the output element or the PCB. To prevent this,
a protection fuse should be inserted at the output.
Use a load power supply capacity that is at least 2 times larger
than the total rated fuse capacity.
2. Contact protection circuit for inductive loads
When an inductive load is connected, connect a diode
(for commutation) in parallel with the load as necessary.
The diode (for commutation) must comply with the following
specifications.
Item
Reverse voltage 5 to 10 times of the load voltage
Forward current Load current or more
3. Interlock
For loads such as forward/reverse contactors, etc.,
where a hazardous condition could result if switched ON
simultaneously, an external interlock should be provided
for interlocking the PLC's internal programs, as shown to
the right.
148
Guide
12 Output Wiring Procedures
12.2 External Wiring of Transistor Output (Sink/Source)
Load
Fuse
Load
Fuse
Inductive
Fuse
Inductive
Fuse
Interlock
Limit of normal
rotation
Limit of reverse
rotation
Interlock
Limit of normal
rotation
Limit of reverse
rotation
Sink output type
Y
COM1
PLC
Source output type
Y
+V0
PLC
Sink output type
load
Y
COM1
PLC
Source output type
load
Y
+V0
PLC
Normal
rotation
Reverse
rotation
PLC output
element
Normal
rotation
Reverse
rotation
PLC output
element