Guaranteed Ramp/Soak - ABB COMMANDER 360 User Manual

3.2.2 Guaranteed Ramp/Soak

If the process variable deviates from the set point by more than the hysteresis value, the program status is set to
'HOLD' and Guaranteed ramp/soak is applied automatically. Each program has two associated hysteresis values:
– applied to ramping segments, and
HYS. r
– applied to soak segments.
HYS. S
The hysteresis value can be set within the limits '0' to '9999' where a setting of '0' implies that no deviation from
the set point value can be tolerated.
Hysteresis can be applied in one of four ways, with individual settings for each segment:
OFF – hysteresis not applied, ramp/soak not guaranteed.
HI – hysteresis applied above set point ( Holdback ('HOLD') set if PV > [SP + Hysteresis]).
LO – hysteresis applied below set point ( 'HOLD' set if PV < [SP – Hysteresis]).
HI. L O – hysteresis applied above and below set point
( 'HOLD' set if PV > [SP + Hysteresis] or PV < [SP – Hysteresis]).
Adjustable ramp rates
Manual
Pause
Adjustable Holdback Hysteresis
1. for Ramp segments
2. for Soak segments
Set
Point
Seg. 1
Start
Process
Note. Ramping segments can have a different hysteresis to soak segments.
3.2.3 Power Recovery Function
The Power Recovery function allows pre-selection of the restart position within a ramp/soak profile when power is
restored after a failure.
With options A, b or C, if power is restored before the
from the point at which power failed. If power is restored after the
from one of the following user-selected points: start of the current program; start of the current segment or from the
profile position at the time of failure. In all three cases the controller restarts in
With option d, the profile continues in run mode from the position on the profile that would have been reached had
the power failure not occurred.
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Holdback Active
outside hysteresis
limits
Seg. 2 Seg. 3
Fig 3.4 Typical 6-segment Ramp/Soak Profile
Hysteresis applied Hi-Lo
(above and below the set point)
Seg. 4 Seg. 5
expires, the ramp/soak profile continues
Power Down Time
Power Down Time
3 PROFILES...
Hysteresis applied Hi
(above the set point)
End of Profile (revert
to Local Set Point or
repeat of profile)
Time (Hours or Minutes)
has expired, the profile resumes
mode.
HOLD
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