Control Cabinet - Mitsubishi 900 Series User Manual

8.1.2

Control cabinet

The GOT is an open type device (device installed to another device) and must be installed in a conductive
control panel 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
(e) Holes made in the control cabinet must be 10 cm (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 FG terminal (FG: Frame
Ground) with the thickest and shortest wire possible. (The wire length must be 30cm (11.18in.)
or shorter.)
The FG terminal function is to pass the noise generated in the GOT 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.
8 - 3
8.1 Requirements for conformance to EMC Directive
8.1.2 Control cabinet
2
wire or thicker is recommended.)