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Module Installation; Grounding; External Wiring - Mitsubishi Electric MELSEC A Series User Manual

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3.2.5 Module installation

(1) Installing modules contiguously
In A series PCs, the left side of each I/O module is left open.
installing an I/O module to the base, do not make any open slots between
any two modules.
with 100/200VAC rating, the printed board which contains the hazardous
voltage circuit becomes bare. When it is unavoidable to leave an open slot,
be sure to install the blank module (AG60).
When using the A5 B expansion base with no power supply, attach the
cover packaged with the expansion base to the side of the leftmost

3.2.6 Grounding

There are two kinds of grounding terminals as shown below. Either grounding
terminal must be used grounded.
Be sure to ground the protective grounding for the safety reasons.
Protective grounding
Functional grounding

3.2.7 External wiring

(1) 24VDC external power supply
For special modules that require a 24 V DC I/O module or external power
supply, use a model whose 24 V DC 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) Insulation requirements
Voltages are shown in Table 2.
Table 2 : Intensive Insulation Withstand Voltage
Rated voltage of hazardous voltage
150VAC or below
300VAC or below
If there is an open slot on the left side of a module
: Maintains the safety of the PC and improves the noise
: Improves the noise resistance.
(Installation Category II, source : IEC664)
Surge withstand voltage (1.2/50µ µ µ µ s)


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