8. LOADING AND INSTALLATION
8 - 14
MELSEC-
Precautions when wiring power supply cable are described.
(1) Wiring power supply
(a) Separate the PLC's power supply line from the lines for I/O devices and
power devices as shown below.
When there is much noise, connect an insulation transformer.
T1
PLC
200 V AC
Main power
supply
PLC power
supply
I/O power supply
Main circuit device
I/O devices
Main circuit device
Insulation
transformer
(b) 100 V AC, 200 V AC and 24 V DC wires should be twisted as dense as
possible. Connect the modules with the shortest distance.
Also, to reduce the voltage drop to the minimum, use the thickest wires
possible (maximum 2 mm
2
).
(c) As a countermeasure to power surge due to lightening, connect a surge
absorber for lightening as shown below.
AC
E1
E2
PLC/IO
devices
Surge absorber for lightening
POINT
(1) Separate the ground of the surge absorber for lightening (E
1
) from that of
the PLC (E
2
).
(2) Select a surge absorber for lightening whose power supply voltage does
no exceed the maximum allowable circuit voltage even at the time of
maximum power supply voltage elevation.
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