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During control system design
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Provide a safety circuit outside the PLC so that the control system can still work safely once
external power failure or PLC fault occurs.
overcurrent caused by operation above rated current or load short-circuit.
An emergency stop circuit, a protection circuit, a forward/reverse operation interlocked
circuit, and an upper position limit and lower position limit interlocked circuit must be set in
the external circuits of PLC to prevent damage to the machine.
To ensure safe operation, for the output signals that may cause critical accidents, design
external protection circuit and safety mechanism;
Once PLC CPU detects abnormality in the system , all outputs may be closed; however, when
a fault occurs in the controller circuit, the output may not be under control. Therefore, it is
necessary to design an appropriate external control circuit to ensure normal operation;
If the PLC output units such as relays or transistors are damaged, the output may fail to switch
between ON and OFF states according to the commands;
The PLC is designed to be used in indoor electrical environment (overvoltage category II). The
power supply must have a system-level lightning protection device, assuring that overvoltage
due to lightning shock cannot be applied to the PLC power supply input terminals, signal
input terminals and output terminals and so forth, so as to avoid damage to the equipment.
Installation
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Installation must be carried out by the specialists who have received the necessary
electrical training and understood enough electrical knowledge.
Disconnect all external power supplies of the system before removing/installing the
module. Failure to do so may result in electric shock, module fault or malfunction.
Do not use the PLC where there are dust, oil smoke, conductive dust, corrosive or
combustible gases, or exposed to high temperature, condensation, wind & rain, or
damage or deterioration to the product.
The PLC is open-type equipment that must be installed in a control cabinet with
necessary electrical training and understood enough electrical knowledge can open
the cabinet.
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