Configuration Of Position Limits, Position Rate Limits And Final_Value_Cutoff And Characterization - GE Baker Hughes Masoneilan SVI FF Installation And Operation Manual

An example to highlight the difference between the travel and user domains, is the effect of
FINAL_VALUE_CUTOFF_HI, a user-configurable parameter, on the Quick Open and EQ% 50
curves. The Quick Open curve has a much more dramatic increase/decrease near the curve
extremes than the EQ% 50. For the Quick Open curve, if you a enter a
FINAL_VALUE_CUTOFF_HI value, it causes a large deviation between the working setpoint
(travel domain and the FINAL_VALUE (user domain) (see the red arrows in Figure 64). Entering
the same FINAL_VALUE_CUTOFF_HI value for the EQ% 50 causes a much smaller deviation.
If you were to do the same for both curves using the FINAL_VALUE_CUTOFF_LO value the
effects would swap.
Configuration of Position Limits, Position Rate Limits and
FINAL_VALUE_CUTOFF and Characterization
Figure 65 graphically explains how setpoint and position interact.
Final Value
Final Value.d
Final Value.dint
Final Position Value
Final Position Value.d
Final Position Value.dint
Figure 66 shows the interplay between a configured position limit, in this case 10% and its
effect for two characterization types:
For Linear (red curve), the 10% limit causes an effective setpoint limit of 10%.
For EQ% 50 (green curve with triangles), the 10% limit causes an effective limit of 45%.
This type of behavior must be kept in mind when choosing a characterization and associated
limits.
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BHGE
Setpoint
source
Actual
position
Figure 65 ValVue SVIFF Setpoint to Position Schema
Characterization
Reverse
Characterization
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Working Setpoint
(characterized)
Working
Position