Appendix 8.1.2 Installation Instructions For Emc Directive - Mitsubishi Electric Q26UD(E)HCPU User Manual

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Appendix 8.1.2
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.
• Keep the diameter of the holes on the control panel to 10cm or less. If the diameter is larger than 10cm,
electromagnetic wave may leak.
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.
The tests were conducted by Mitsubishi Electric Corporation using a control panel having damping
characteristics of 37dB (maximum) and 30dB (average) (measured at 3m distance, 30 to 300MHz).
(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 30cm 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.
654
Installation instructions for EMC Directive
*1

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