Mitsubishi 13J851, User Manual

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A-2
[DESIGN PRECAUTIONS]
DANGER
(3) Depending on the failure of the output module ’ s relay or transistor, the
output status may remain ON or OFF incorrectly. For output signals that
may lead to a serious accident, create an external monitoring circuit.
If load current more than the rating or overcurrent due to a short circuit
in the load has flowed in the output module for a long time, it may
cause a fire and smoke. Provide an external safety device such as a
fuse.
Design a circuit so that the external power will be supplied after
power-up of the PLC.
Activating the external power supply prior to the PLC may result in an
accident due to incorrect output or malfunction.
For the operation status of each station at a communication error in
data link, refer to the respective data link manual.
The communication error may result in an accident due to incorrect
output or malfunction.
When controlling a running PLC (data modification) by connecting a
peripheral device to the CPU module or a PC to a special function module,
create an interlock circuit on sequence programs so that the whole system
functions safely all the time.
Also, before performing any other controls (e.g. program modification,
operating status change (status control)), read the manual carefully and
ensure the safety.
In these controls, especially the one from an external device to a PLC in a
remote location, some PLC side problem may not be resolved immediately
due to failure of data communications.
To prevent this, create an interlock circuit on sequence programs and
establish corrective procedures for communication failure between the
external device and the PLC CPU.
For the redundant power supply system, use the A37RHB redundant power
supply main base unit and the A68RB redundant power supply extension
base unit.
When using an old model, A3 B, A5 B or A6 B, set the output hold/reset
setting switch on the CPU module to the output reset mode. Inadvertently
using it in the output hold mode may result in an accident due to incorrect
output and/or malfunctions.
When setting up the system, do not allow any empty slot on the base unit.
If any slot is left empty, be sure to use a blank cover (A1SG60) or a dummy
module (A1SG62) for it.
When using the extension base unit, A52B, A55B or A58B, attach the
included dustproof cover to the module in slot 0.
Otherwise, internal parts of the module may be flied in the short circuit test or
when an overcurrent or overvoltage is accidentally applied to external I/O
section.