YOKOGAWA UT55A - Chapter 15: Power Failure Recovery and Other Settings; 15.1 Remedies if Power Failure Occurs during Operations

15-1
IM 05P01C31-01EN
PowerFailureRecoveryProcessing/SettingPowerFrequency/OtherSettings
15
15.1 RemediesifPowerFailureOccursduring
Operations
Description
The operation status and remedies after a power failure differ with the length of power
failure time:
Regardless of the length of power failure time, all functions of the controller cannot be
operated for about 10 seconds after recovery. However, the case of instantaneous power
failure is excepted.
•
100–240VAC:
Instantaneouspowerfailureof20msorless
• 24VAC/DC:Instantaneouspowerfailureof1ms
A power failure is not detected. Normal operation continues.
• Power failure of about less than 5 seconds
The following shows effects caused in “settings” and “operation status.”
Alarm action
Does not continue. Alarm with stand-by function will enter stand-by status.
Alarmlatchwillbeinitialized.
Setting parameter Set contents of each parameter are retained.
Auto-tuning Cancelled.
Control action Action before power failure continues.
Timer, counter (ladder
program)
Initialized.
• Power failure of about 5 seconds or more
The following shows effects caused in “settings” and “operation status.”
Alarm action
Does not continue. Alarm with stand-by function will enter stand-by status.
Alarmlatchwillbeinitialized.
Setting parameter Set contents of each parameter are retained.
Auto-tuning Cancelled.
Control action
Differs with setting of the parameter “R.MD” (restart mode).
R.MD setting Control action after recovery from power failure
CONT Continues action before power failure. (Factory default)
MAN
(*)
Outputs the preset output value (PO) of the PID group
used as control output and continues action in MAN
mode.
AUTO
(*)
The control computation is executed in AUTO mode
based on the preset output value (PO) of the PID group
used as control output.
*InHeating/coolingcontrol,startsactionfrom50%ofcontrolcomputation
output.
Timer, counter (ladder
program)
Initialized.
Setting Details
Parameter
symbol
Name
Display
level
Setting range Menusymbol
R.MD Restart mode STD
CONT: Continue action set before
power failure.
MAN: Start from MAN.
AUTO: Start from AUTO.
SYS
Chapter15PowerFailureRecoveryProcessing/PowerFrequency Setting/OtherSettings