External Wiring Precautions - Mitsubishi FX3G SERIES User Manual

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

20.7.4 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.
2. Contact protection circuit for inductive loads
An internal protection circuit for the relays is not provided for the relay output circuit in the terminal block. 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 (for commutation) parallel to the load.
The diode (for commutation) must comply with the
following specifications.
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.
Static electricity capacity
Forward current
Reference
Manufacturer
Okaya Electric Industries Co., Ltd.
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.
Guide
5 to 10 times of the load voltage
Load current or more
Guide
Approx. 0.1 F
Approx. 100 to 200
Model name
CR-10201
Load
0 to 7
Fuse
COMn
inductive load
PLC output
contact
Diode
(for commutation)
inductive load
PLC output
contact
Surge
absorber
Manufacturer
Rubycon Corporation 250MCRA104100M B0325
Interlock
PLC output
contact
PLC output
contact
*
Bad
*
Good
*
20 Terminal Block
20.7 FX-16EYR-TB
11
12
Terminal block
13
14
15
16
17
Model name
Forward
limit 18
Forward
Reverse
Reverse
limit
19
*
20
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