Mitsubishi Melsec-Q Series User Manual page 199

9.1.2 Installation instructions for EMC Directive
Programmable controller is an open type device and must be installed inside a control panel for use.
This not only ensures safety but also ensures effective shielding of programmable controller-generated
electromagnetic noise.
*1: 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
• Use a conductive control panel.
• 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 plate.
• 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.
• Ground the control panel with a thick wire so that a low impedance connection to ground can be ensured
even at high frequencies.
• Holes made in the control panel must be 10 cm (3.94 inches) diameter or less. If the holes are 10 cm (3.94
inches) or larger, radio frequency noise may be emitted.
In addition, because radio waves leak through a clearance between the control panel door and the main unit,
reduce the clearance as much as practicable.
The leakage of radio waves can be suppressed by the direct application of an EMI gasket on the paint
surface.
Our tests have been carried out on a panel having the damping characteristics of 37 dB max. and 30 dB mean
(measured by 3 m method with 30 to 300 MHz).
(2) Connection of power line and ground wire
Ground wire and power supply cable for the programmable controller system must be connected as described
below.
• Provide an grounding point near the power supply module. Ground 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 (11.81 inches) 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.
• The ground wire led from the grounding point must be twisted with the power supply wires. By twisting with
the ground wire, noise flowing from the power supply wires can be relieved to the ground. However, if a filter
is installed on the power supply wires, the wires and the ground wire may not need to be twisted.
CHAPTER9 EMC AND LOW VOLTAGE DIRECTIVES
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