Power Supply; Control Box - Mitsubishi MELESEC-ST User Manual

11 EMC AND LOW VOLTAGE DIRECTIVE

11.2.3 Power supply

11.2.4 Control box

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The isolation specification of the power distribution module is designed assuming
installation category II. Make sure to use the installation category II power supply to the
MELSEC-ST series.
The installation category indicates the durability level against surge voltage generated by
a thunderbolt. Category I has the lowest durability; category IV has the highest durability.
Category IV
Category II indicates the power supply for which voltage is stepped down by using two
or more isolation transformers from the public power distribution.
Because the MELSEC-ST series is an open device (a device designed to be stored
within another module), make sure to use it after storing in the control box.
(1) Shock protection
In order to prevent those who are unfamiliar with power facility, e.g., an operator,
from getting a shock, make sure to take the following measures on the control
panel.
(a) Install MELSEC-ST series within the locked control panel, and allow only
those who are familiar with power facility to unlock the control panel.
(b) Build the structure in order that the power supply will be shut off when the
control panel is opened.
(2) Dustproof and waterproof features
The control box also has the dustproof and waterproof functions. Insufficient
dustproof and waterproof features lower the dielectric withstand voltage, resulting
in isolation destruction. The isolation in the MELSEC-ST series is designed to be
resistant to the pollution level 2, so use in the environment equivalent to pollution
level 2 or below.
Pollution level 1 :
Pollution level 2 :
Pollution level 3 :
Pollution level 4 :
As shown above, the MELSEC-ST series can work under the pollution level 2
when installed in a control box equivalent to IP54.
Category III
Figure 11.1: Installation Category
An environment where the air is dry and conductive
dust does not exist.
An environment where conductive dust
does not usually exist, but 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.
An environment where conductive dust exits and conductivity
may be generated due to the accumulated dust.
An environment for a typical factory floor.
Continuous conductivity may occur due to rain, snow,
etc. An outdoor environment.
MELSEC-ST
Category II Category I
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