22-82 Work Point Calculation
Option:
Function:
[0]
*
Disabled
Disabled [0]
: Work Point Calculation not active. To be used if speed at design point is known (see table above).
[1]
Enabled
Enabled [1]
: Work Point Calculation is active. Enabling this parameter allows the calculation of the unknown
System Design Working Point at 50/60 Hz speed, from the input data set in par.22-83/84, 22-87, 22-88, 22-89
and 22-90.
Example 1
: Speed at System Design Working Point is known:
From the data sheet showing characteristics for the specific equipment at different speeds, simply reading across
from the H
DESIGN
point and the Q
DESIGN
point allows us to find point A, which is the System Design Working Point.
The pump characteristics at this point should be identified and the associated speed programmed. Closing the
valves and adjusting the speed until H
MIN
has been achieved allows the speed at the no flow point to be identified.
Adjustment of par. 22-81 Square-Linear Curve Approximation then allows the shape of the control curve to be
adjusted infinitely.
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
DESIGN
, Point C) the flow at that
pressure Q
RATED
can be determined. Similarly, by plotting the design flow (Q
DESIGN
, Point D). the pressure H
D
at
that flow can be determined. Knowing these two points on the pump curve, along with H
MIN
as described above,
allows the frequency converter to calculate the reference point B and thus to plot the control curve which will
also include the System design Working Point A.
VLT
®
HVAC Drive Programming Guide
3. Parameter Description
MG.11.C5.02 - VLT
®
is a registered Danfoss trademark
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