Safety Instruction
2
Safety Instructions when designing
Please, install protection circuit on the exterior of PLC to protect
the whole control system from any error in external power or PLC
module. Any abnormal output or operation may cause serious problem
in safety of the whole system.
- Install applicable protection unit on the exterior of PLC to protect
the system from physical
damage such as emergent stop switch,
protection circuit, the upper/lowest limit switch, forward/reverse
operation interlock circuit, etc.
- If any system error (watch-dog timer error, module installation error,
etc.) is detected during CPU operation in PLC, the whole output is
designed to be turned off and stopped for system safety. However,
in case CPU error if caused on output device itself such as relay or
TR can not be
detected, the output may be kept on, which may
cause serious problems. Thus, you are recommended to install an
addition circuit to monitor the output status.
Never connect the overload than rated to the output module nor
allow the output circuit to have a short circuit, which may cause a
fire.
Never let the external power of the output circuit be designed to
be On earlier than PLC power, which may cause abnormal output or
operation.
In case of
data exchange between computer or other external
equipment and PLC through communication or any operation of
PLC (e.g. operation mode change), please install interlock in the
sequence program to protect the system from any error. If not, it
may cause abnormal output or operation.
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