YOKOGAWA FA-M3V e-RT3 Plus, Hardware Manual

Page: 177 / 274

A3-17
IM 34M06C11-01E
 Standard Mode (common to all power supply modules)

Momentary Power Failure Detection
- System operation continues without interruption even if the power fails momentarily
for no longer than 20ms (undetected momentary power failure).
- If a power failure longer than 20ms occurs, the controller may or may not recognize
a momentary power failure condition because an uncertainty is involved. When the
controller detects a momentary power failure, it suspends program execution while
retaining the current state of its outputs. It also records the date and time at which
the momentary power failure occurred into the error log file in the CPU. When
power is restored, the controller resumes the execution of the program.

Power Failure Detection
When the CPU operating voltage (+5V) falls below 95% of the rated voltage, the
controller stops operation, turns off its outputs, and then turn on the FAIL contact.
(Refer to Section A2.3 for details on how the FAIL contact works).

Automatic Recovery
The controller resumes normal operation automatically when the power recovers from a
momentary power failure condition and the CPU operating voltage (+5V) rises above
95% of the rated voltage. The controller restarts in the reset restart mode after a power
failure is detected.

Power on/off Sequences
ON
Allowable momentary
power failure time
Momentary power
failure detected
Power failure
detected
Power restored
Power shutdown
Power‐on 20 ms or less
Longer than
20 ms
Power failure detected
Power supply
Power Loss
Detected
CPU operating
voltage (+5V)
Reset
Program
FAIL 1 contact
OFF
Approx. 3 s
Approx. 2 s
Reset restart
Continued
operation
FA030306.VSD
Momentary power failure detected
Figure A3.14 Detection of Abnormal Supply Voltage Levels in Standard Mode