Installation Inside The Control Panel - Mitsubishi Electric MELSEC-Q Series User Manual

3.1.2

Installation inside the control panel

The programmable controller is open equipment and must be installed
within a control panel for use.* This not only ensures safety but also
ensues effective shielding of programmable controller-generated
electromagnetic noise.
* Also, each network remote station needs to be installed inside the
control panel.
However, the waterproof type remote station can be installed outside
the control panel.
(1) Control panel
(a) Use a conductive control panel.
(b) When attaching the control panel's top plate or base plate,
mask painting and weld so that good surface contact can be
made between the panel and the bolt.
(c) To ensure good electrical contact with the control panel, mask
the paint on the installation bolts of the inner plate in the control
panel so that contact between surfaces can be ensured over
the widest possible area.
(d) Earth the control panel with a thick wire so that a low
impedance connection to ground can be ensured even at high
frequencies.
(e) Holes made in the control panel must be 10 cm (3.94 in.)
diameter or less. If the holes are 10 cm (3.94 in.) or larger,
radio frequency noise may be emitted.
(2) Connection of power and earth wires
Earthing and power supply wires for the programmable controller
system must be connected as described below.
(a) Provide an earthing point near the power supply module. Earth
the power supply's LG and FG terminals (LG : Line Ground, FG
: Frame Ground) with the thickest and shortest wire possible.
(The wire length must be 30 cm (11.18 in.) or shorter.) The LG
and FG terminals function is to pass the noise generated in the
programmable controller system to the ground, so an
impedance that is as low as possible must be ensured. As the
wires are used to relieve the noise, the wire itself carries a
large noise content and thus short wiring means that the wire is
prevented from acting as an antenna.
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