Mitsubishi MELSEC-A A1SCPUC24-R2, User Manual

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3.2.3 Power supply
The insulation specification of the power module was designed
assuming installation category II. Be sure to use the installation
category II power supply to the programmable controller.
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.
Figure 1. : Installation Category
Category II indicates a power supply whose voltage has been reduced
by two or more levels of isolating transformers from the public power
distribution.
3.2.4 Control panel
Because the programmable controller is an open device (a device
designed to be stored within another module), be sure to use it after
storing in the control panel.
(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 panel
must have the following functions :
(a) The control panel 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 panel must have a structure which automatically
stops the power supply when the box is opened.
(c) For electric shock protection, use IP20 or greater control
panel.
Category IV Category I Category II Category III