Mitsubishi Electric GT11 User Manual page 58

(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
Pollution level 3: An environment where conductive dust exits and conductivity may be
Pollution level 4: Continuous conductivity may occur due to rain, snow, etc.
Grounding
3
It is necessary to use the GOT grounding terminal only when it is in the grounded condition.
Be sure to ground the grounding for the safety reasons and EMC Directives.
Functional grounding : Improves the noise resistance.
5 - 3
5.2 EMC DIRECTIVE
5.2.1 Requirements for Conformance to EMC Directive
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.
generated due to the accumulated dust.
An environment for a typical factory floor.
An outdoor environment.