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MELSEC-Q
8 EMC AND LOW VOLTAGE DIRECTIVE
8.2.5 Grounding
There are the following two different grounding terminals.
Use either grounding terminal in an earthed status.
Protective grounding
: Maintains the safety of the PLC and improves the
noise resistance.
Functional grounding
: Improves the noise resistance.
8.2.6 External wiring
(1) 24VDC external power supply
For the MELSEC-Q series PLC 24VDC I/O modules and the intelligent function
modules (special function modules) which require external supply power, use a
model whose 24VDC circuit is intensively insulated from the hazardous voltage
circuit.
(2) External devices
When a device with a hazardous voltage circuit is externally connected to the
PLC, use a model whose circuit section of the interface to the PLC is intensively
insulated from the hazardous voltage circuit.
(3) Intensive insulation
Intensive insulation refers to the insulation with the dielectric withstand voltage
shown in Table 8.1.
Table 8.1 : Intensive Insulation Withstand Voltage
(Installation Category II, source : IEC664)
Rated voltage of hazardous voltage area Surge withstand voltage (1.2/50 s)
150VAC or below 2500 V
300VAC or below 4000 V