Mitsubishi FX3UC SERIES User Manual page 237

FX Series Programmable Controllers
3UC
User's Manual - Hardware Edition
8.8.4 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.
Counter voltage
Forward current
2) AC circuit
C o n n e c t t h e s u r g e a b s o r b e r ( c o m b i n e d C R
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
Static electricity capacity
Forward current
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.
Guide
5 to 10 times of the load voltage
Load current or more
Guide
Approx. 0.1µF
Approx. 100 to 200Ω
Model name
8 Terminal Block Specifications and External Wiring
Load
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
*
8.8 FX-16EYR-TB
0 to 7
Terminal block
Model name
Forward limit
Reverse limit
*
10
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