Mitsubishi Electric LCPU-U-HW Safety Manuallines page 68

The power-on procedure is as follows:
• For AC and DC power
1) Power on the programmable controller.
2) Set the CPU module to RUN.
3) RA2 turns on when DC power is on.
4) Timer (TM) turns on when DC power establishes the rated voltage.
(The timer value is the period of time from when RA2 turns on to when
DC power establishes the rated voltage. Set this value to 0.5 seconds.)
5) Turn on the start switch.
6) When the electromagnetic contactor (MC) turns on, the output devices
will be activated by the program.
(If a voltage relay is used at RA2, no timer (TM) is required in the
program.)
(2) Fail-safe measures against failure of CPU module
The self-diagnostic function can detect failure of the CPU module
and a SD memory card. However, if an error occurs in an area
such as I/O control part, the CPU module may not detect failure.
In this case, all points may turn on or off depending on the failure,
and normal operation and safety cannot be ensured.
Although Mitsubishi programmable controllers are manufactured
under strict quality control, it is recommended to configure external
fail-safe circuits to prevent mechanical damage or accidents due to
failure of the programmable controller.
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