Safety Instruction
Safety Instructions for Design Process
 Please install a protection circuit on the exterior of PLC so that the whole system may
operate safely regardless of failures from external power or PLC. Any abnormal output or
operation from PLC may cause serious problems to safety in whole system.
- Install protection units on the exterior of PLC like an interlock circuit that deals with opposite
operations such as emergency stop, protection circuit, and forward/reverse rotation or install
an interlock circuit that deals with high/low limit under its position controls.
- If any system error (watch-dog timer error, module installation error, etc.) is detected during
CPU operation in PLC, all output signals are designed to be turned off and stopped for
safety. However, there are cases when output signals remain active due to device failures
in Relay and TR which can’t be detected. Thus, you are recommended to install an addition
circuit to monitor the output status for those critical outputs which may cause significant
problems.
 Never overload more than rated current of output module nor allow to have a short
circuit. Over current for a long period time may cause a fire .
 Never let the external power of the output circuit to be on earlier than PLC power, which
may cause accidents from abnormal output operation.
 Please install interlock circuits in the sequence program for safe operations in the
system when exchange data with PLC or modify operation modes using a
computer or
other external equipments Read specific instructions thoroughly when conducting control
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