Danfoss VLT Programming Manual page 152

Parameter Description
Parameter used
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.
H (head)
Control Curve
®
VLT HVAC Drive Programming Guide
Speed at
Design Point
KNOWN
+
+
+
+
+
+
-
-
-
22-82 Work Point Calculation
Option:
Q ( ow)
®
MG.11.CB.02 - VLT is a registered Danfoss trademark
Speed at
Design Point Cascade Controller
UNKNOWN
+
+
+
+
-
+
+
+
+
Function:
Example 1: Speed at System Design Working Point is
known:
H
(head)
H
A
DESIGN
Set Point
H
MIN
Par.:
22-83/
Control Curve
22-84/
22-87
Q
(flow)
From the data sheet showing characteristics for the
specific equipment at different speeds, simply
reading across from the H
DESIGN
Q point allows us to find point A, which is the
DESIGN
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
achieved allows the speed at the no flow point to be
identified.
Adjustment of 22-81 Square-linear Curve Approxi-
mation 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
Point C) the flow at that pressure Q
determined. Similarly, by plotting the design flow
(Q , Point D). the pressure H
DESIGN
be determined. Knowing these two points on the
pump curve, along with H as described above,
MIN
allows the frequency converter to calculate the
reference point B and thus to plot the control curve
+
-
3 3
-
-
-
+
-
-
-
point and the
has been
,
DESIGN
can be
RATED
at that flow can
D
151