Control Cabinet - Mitsubishi GOT1000 GT11 User Manual

5.1.2

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 2 wire or thicker is recommended.)
(e) Holes made in the control cabinet must be 10 cm (3.94inch) diameter or less. If the holes are
10cm (3.94inch) 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.
(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
(11.18inch) 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.
(3) Electrical shock prevention
In order to such as the operators from electric shocks, the control box must have the following
functions :
(a) The control cabinet must be equipped with a lock so that only skilled or qualified personnel.
(b) The control cabinet must be fitted with advice which automatically stops the power supply
when the cabinet is opened.
(4) Dustproof and waterproof features
The control box also has the dustproof and waterproof functions. Insufficient dustproof and
waterproof features lower the insulation withstand voltage, resulting in insulation destruction.
The insulation in our GOT is designed to cope with the pollution level 2, so use in an environment
with pollution level 2 or better.
Pollution level 1: An environment where the air is dry and conductive dust does not exist.
Pollution level 2: An environment where conductive dust does not usually exist, but occasional
5 - 2 5.1 Requirements for Conformance to EMC Directive
5.1.2 Control cabinet
temporary conductivity occurs due to the accumulated dust.
Generally, this is the level for inside the control box equivalent a control room
or on the floor of a typical factory.