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Parameter used
Speed at
Design Point
KNOWN
Speed at
Design Point
UNKNOWN
Cascade Controller
Flow Compensation, 22-80
+
+
+
Square-Linear Curve Approximation, 22-81
+
+
-
Work Point Calculation, 22-82
+
+
-
Speed at No Flow, 22-83/84
+
+
-
Speed at Design Point, 22-85/86
+
-
-
Pressure at No Flow, 22-87
+
+
+
Pressure at Rated Speed, 22-88
-
+
-
Flow at Design Point, 22-89
-
+
-
Flow at Rated Speed, 22-90
-
+
-
22-80 Flow Compensation
Option:
Function:
[0]
*
Disabled [0]
Disabled
: Set-Point compensation not active.
[1]
Enabled [1]
Enabled
:Set-Point compensation is active.
Enabling this parameter allows the Flow
Compensated Setpoint operation.
22-81 Square-linear Curve Approximation
Range:
Function:
100 %
*
[0 - 100 %] Example 1:
Adjustment of this parameter allows the
shape of the control curve to be adjusted.
0 = Linear
100% = Ideal shape (theoretical).
NOTE
Not visible when running in cascade.
Control Curve
(head)
(flow)
H
Q
130BA388.11
100%
P22-81 0%
22-82 Work Point Calculation
Option:
Function:
Example 1: Speed at System Design Working Point is
known:
A
130BA385.11
P22-85/22-86
Control Curve
H
MIN
H
DESIGN
Set Point
n
RA
TED
_
f
RA
TED
n
DESIGN
-
f
DESIGN
Q
(flow)
H
(head)
Par.:
22-83/
22-84/
22-87
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 character-
istics 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
22-81 Square-linear Curve Approxi-
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
Parameter Description
VLT
®
HVAC Drive Programming Guide
MG.11.CB.02 - VLT
®
is a registered Danfoss trademark
151
3
3
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