Danfoss VLT AQUA Programming Manual page 209

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VLT AQUA Drive Programming Guide 2. Parameter Description
Example 1: Speed at System Design Working Point is known:
2
From the data sheet showing characteristics for the specific
equipment at different speeds, simply reading across from the
H point and the Q point allows us to find point A,
DESIGN DESIGN
which is the System Design Working Point. The pump charac-
teristics at this point should be identified and the associated
speed programmed. Closing the valves and adjusting the speed
until H has been achieved allows the speed at the no flow
MIN
point to be identified.
Adjustment of par. 22-81 Square-Linear Curve Approximation
then allows the shape of the control curve to be adjusted infin-
itely.
Example 2:
Speed at System Design Working Point is not known: Where the
Speed at System Design Working Point is unknown, another
reference point on the control curve needs to be determined by
means of the data sheet. By looking at the curve for the rated
speed and plotting the design pressure (H , Point C) the
DESIGN
flow at that pressure Q can be determined. Similarly, by
RATED
plotting the design flow (Q , Point D). the pressure H at
DESIGN D
that flow can be determined. Knowing these two points on the
pump curve, along with H as described above, allows the
MIN
frequency converter to calculate the reference point B and thus
to plot the control curve which will also include the System de-
sign Working Point A.
209
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