Mitsubishi Electric FX5U User Manual page 93

Wiring precautions
■Protection circuit for load short-circuiting
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.
■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 product life.
DC circuit
•
Connect a diode in parallel with the load.
The diode (for commutation) must comply with the following
specifications.
 Reverse voltage: 5 to 10 times the load voltage
 Forward current: Load current or more
AC circuit
•
Connect a surge absorber (CR composite parts like surge killer,
spark killer, etc.) parallel to the load. Select a surge absorber with
voltage rating that is suitable for the output used.
 Electrostatic capacity: Approx. 0.1 F
 Resistance: Approx. 100 to 200 
■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 along with an
interlock in the PLC program, as shown to the right.
■In-phase
PLC output contacts (*) should be used in an "in-phase" manner.
Load
Y0
Fuse
COM0
+
Inductive load
PLC output contact
Diode (for commutation)
Inductive load
PLC output contact
Surge
absorber
Limit of forward
Interlock
rotation
PLC output
Limit of reverse
contact
rotation
PLC output
contact
*
*
*
PLCs
-
6
Forward
rotation
Reverse
rotation
*
6 WIRING
91
6.6 Output Wiring