ABB COMMANDER 1900 Series User Manual

Also see for COMMANDER 1900 Series: Programming guide Installation guide Programming guide Operating guide

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ABB COMMANDER 1900 Series User Manual Manual pdf 7 page image

52 CONTROL CONFIGURATION LEVEL…• Ramp/Soak2.1.3 Self-seeking Set Point – Fig. 2.5The Self-seeking Set Point function reduces the delay between the end of a program and the beginning of the next program. Theprocess variable value is used as the program start point and the set point steps up to the process variable value. This has theeffect of changing the overall segment time and maintains a constant ramp rate.2.1.4 Retort Function – Fig. 2.6The Retort function ensures safe operation of retorts under fault conditions. When the process variable falls below the holdbackhysteresis value the program is put on ‘hold’ (as for normal operation). The set point then tracks the process variable until theprocess variable starts to increase. The set point then ramps back up to the soak level at the rate of the previous ramp. When thesoak level is reached the program is released from its ‘hold’ state and depending on the retort mode selected either completes thesegment or repeats the entire segment.The retort mode is selected in the Ramp/Soak Profile Page, CONTROL CONFIGURATION LEVEL.2.1.5 Power Recovery FunctionNote. The Power Down Recovery Function is only available on instruments fitted with the Timer option.The Power Recovery function allows pre-selection of the restart position within a ramp/soak profile when power is restored aftera failure. If power is restored before the Power Down Time expires, the ramp/soak profile continues from the point at which powerfailed. If power is restored after the Power Down Time has expired, the profile resumes from one of the following user-selectedpoints: start of the current program; start of the current segment or from the profile position at the time of failure. In all three casesthe controller restarts in HOLD mode. When power is re-applied to instruments not fitted with the Timer option, the profile is turnedoff and control resumes at the local set point.Fig. 2.6 Retort FunctionProcess VariableSeg. 1 Seg. 2Set PointProgram on HoldHoldbackHysteresisBandwidthSegment eithercompleted orrepeatedSet Point RampsBack to Soak Levelat Previous RampRateEqual to the valueset in HoldbackHysteresis FrameFig. 2.5 Self Seeking Set PointSet PointProcess VariableSeg. 1 Seg. 2 Seg. 3Current Process Variableinserted as Program Start LevelSeg. 1 Seg. 2 Seg. 3 Seg. 1 Seg. 2 Seg. 3ProgramStartProgramStartProgramStartCurrent ProcessVariable Inserted asProgram Start Level