Installation Inside Control Box - Mitsubishi Electric A960GOT User Manual

1 OVERVIEW

1.2.2 Installation inside Control Box

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The GOT is an open type device (device installed to another device) and must be
installed in a conductive control pauel or cabinet.
It not only assure the safety but also has a large effect to shut down the noise
generated from GOT, on the control panel.
1) Control cabinet
a) Use a conductive control cabinet.
b) When attaching the control cabinet'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 cabinet, mask the paint on
the installation bolts of the inner plate in the control cabinet so that contact
between surfaces can be ensured over the widest possible area.
d) Earth the control cabinet with a thick wire so that a low impedance connection
to ground can be ensured even at high frequencies. (22mm
recommended.)
e) Holes made in the control cabinet must be 10cm (3.94in.) diameter or less. If
the holes are 10cm (3.94in.) 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 and ground wires
Ground and power supply wires for the GOT must be connected as described
below.
a) Provide an earthing point near the GOT. 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 (11.18in.) or shorter.)
The LG and FG terminals function is to pass the noise generated in the PC
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.
Note) A long conductor will become a more efficient antenna at high
frequency.
b) The earth wire led from the earthing point must be twisted with the power
supply wires. By twisting with the earthing wire, noise flowing from the power
supply wires can be relieved to the earthing. However, if a filter is installed on
the power supply wires, the wires and the earthing wire may not need to be
twisted.
MELSEC-GOT
2
wire or thicker is
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