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3.2.4 Control box
Because the PLC is an open device (a device designed to be stored within another
module), be sure to use it after storing in the control box.
(1) Electrical shock prevention
In order to prevent persons who are not familiar with the electric facility
such as the operators from electric shocks, the control box must have the
following functions :
(a) The control box must be equipped with a lock so that only the
personnel who has studied about the electric facility and have enough
knowledge can open it.
(b) The control box must have a structure which automatically stops the
power supply when the box is opened.
(2) 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 PLC is designed to cope with the pollution level 2, so use in an
environment with pollustion level 2 or below.
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 temporary conductivity
occurs due to the accumulated dust. Generally, this
is the level for inside the control box equivalent to
IP54 in a control room or on the floor of a typical
factory.
Pollution level 3 : An environment where conductive dust exits and
conductivity may be generated due to the
accumulated dust.
An environment for a typical factory floor.
Pollution level 4 : Continuous conductivity may occur due to rain,
snow, etc. An outdoor environment.
As shown above, the PC can realize the pollution level 2 when stored in a
control cabinet equivalent to IP54.
Summary of Contents for Melsec A Series
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