Grounding; External Wiring - Mitsubishi MELESEC-ST User Manual

11 EMC AND LOW VOLTAGE DIRECTIVE

11.2.5 Grounding

11.2.6 External wiring

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There are the following two different ground terminals.
Either of them must be grounded for use.
Protective grounding
Functional grounding
(1) External power supply
For the MELSEC-ST series I/O modules and the intelligent function modules
which require external supply power, use a model of which 24VDC circuit is
reinforced-isolated from the hazardous voltage circuit.
(2) External devices
When a device with a hazardous voltage circuit is externally connected to the
MELSEC-ST series, use a model of which circuit section of the interface to the
MELSEC-ST series is reinforced-isolated from the hazardous voltage circuit.
(3) Reinforced isolation
Reinforced isolation refers to the isolation with the dielectric withstand voltage
shown in Table 11.1.
Table 11.1 : Reinforced Isolation Withstand Voltage
Rated voltage of hazardous voltage area
150VAC or below
300VAC or below
: Maintains the safety of the MELSEC-ST series and
improves the noise resistance.
: Improves the noise resistance.
(Installation Category II, source : IEC664)
Surge withstand voltage (1.2/50
MELSEC-ST
s)
2500 V
4000 V
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