4-8 Power failure4-8 Power failure
If power is lost and then restored, while a profile is running, the behavior of
the profile is determined by the setting of the parameter " PFR " power fail
recovery in profile configuration. This can have one of 4 settings - ,
, and . If is selected, then when power is restored
the profile continues from where it was interrupted when power was lost.
The parameters such as set point value ( SV ), time remaining ( TIME ) and
cycle remaining ( CYCL ) will be restored to their power-down values. For
application that need to bring the process value to the set point value as
soon as possible, this is the best choice. The two diagrams below illustrate
the respective responses, Fig. 4.3 if power fails during a dwell segment and
Fig. 4.4 if it fails during a ramp segment.
Ramp
Segment
Set pointSet point
Time
t1
Segment dwell
time = t1+t2
Segment dwell
time
= t1+t2
power offpower off
power onpower on
t2
Dwell
Segment
Figure 4.3 Recovery from profile at dwell segment
Figure 4.3 Recovery from profile at dwell segment
Figure 4.4 Recovery from profile at ramp segmentFigure 4.4 Recovery from profile at ramp segment
Set pointSet point
Time
power onpower on
power offpower off
Ramp Segment Dwell Segment
Target Set pointTarget Set point
UM0P411A
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