External Wiring Precautions - Mitsubishi FX3U SERIES User Manual

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

12.2.4 External wiring precautions

1. Protection circuit for load short-circuiting
A short-circuit at a load connected to an output terminal could
cause burnout at the PCB. To prevent this, a protection fuse
should be inserted at the output.
2. Contact protection circuit for inductive loads
An internal protection circuit for the relays is not provided for the relay output circuit in this product. It is
recommended to use inductive loads with built-in protection circuits. When using loads without built-in
protection circuits, insert an external contact protection circuit, etc. to reduce noise and extend the product
life.
1) DC circuit
Connect a diode in parallel with the load.
The diode (for commutation) must comply with the following
specifications.
Item
Reverse voltage
Forward current
2) AC circuit
Connect the surge absorber (combined CR components
such as a surge killer and spark killer, etc.) parallel to the
load.
Select the rated voltage of a surge absorber that is suitable
for the load being used. Refer to the table below for other
specifications.
Item
Electrostatic capacity
Resistance value
Reference
Manufacturer
Okaya Electric Industries Co., Ltd. CR-10201
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.
4. In-phase
PLC output contacts (*) should be used in an "in-phase"
manner.
210
Guide
5 to 10 times the load voltage
Load current or more
Guide
Approx. 0.1µF
Approx. 100 to 200Ω
Model name
12 Output Wiring Procedures
12.2 External Wiring for Relay Output
Load
Fuse
PLC output
contact
(for commutation)
PLC output
contact
Manufacturer
Rubycon Corporation 250MCRA104100M B0325
PLC output
contact
PLC output
contact
Bad
Good
Y 0
COM1
PLC
Inductive load
Diode
Inductive load
Surge
absorber
Model name
Inter- Limit of normal
lock rotation
Limit of reverse
rotation
*
*
*
*