Installation Instructions For Emc Directive - Mitsubishi MELSEC-A A2USHCPU-S1 User Manual

9. EMC AND LOW VOLTAGE DIRECTIVES
9.1.2

Installation instructions for EMC directive

The programmable controller is open equipment and must be installed within a control
panel for use.
programmable controller-generated electromagnetic noise.
(1)
(2)
*
This not only ensures safety but also ensues effective shielding of
* 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.
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 cabinet and plate.
(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 10cm (3.94inch) diameter or less. If the
holes are 10cm (3.94inch) or larger, radio wave may be emitted.
Connection of power cable and ground wires
Earthing and power supply cable for the programmable controller system must be
connected as described below.
(a) Provide a grounding 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 30cm (11.18inch)
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.
In addition, make sure to wire the ground cable short as the wires are used to
relieve the noise, the wire itself carries large noise content and thus short wiring
means that the wire is prevented from acting as an antenna.
(b) The ground wire led from the grounding point must be twisted with the power
cables. By twisting with the ground wire, noise flowing from the power cables can
be relieved to the earthing. However, if a filter is installed on the power cables,
the wires and the ground wire may not need to be twisted.
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