Danfoss VLT Series Programming Manual page 157

Parameter Description
Parameter used
22-80 Flow Compensation
22-81 Square-linear Curve Approximation
3 3
22-82 Work Point Calculation
22-83 Speed at No-Flow [RPM]/22-84 Speed at No-
Flow [Hz]
22-85 Speed at Design Point [RPM]/22-86 Speed at
Design Point [Hz]
22-87 Pressure at No-Flow Speed
22-88 Pressure at Rated Speed
22-89 Flow at Design Point
22-90 Flow at Rated Speed
22-80 Flow Compensation
Option:
[0] Disabled Set-Point compensation not active.
*
[1] Enabled Set-Point compensation is active. Enabling this
22-81 Square-linear Curve Approximation
Range:
100 % [0 - 100 %] Example 1:
*
NOTE
Not visible when running in cascade.
H (head)
Control Curve
156
VLT
Function:
parameter allows the Flow Compensated Setpoint
operation.
Function:
Adjustment of this parameter allows the
shape of the control curve to be adjusted.
0 = Linear
100% = Ideal shape (theoretical).
MG.11.CC.02 - VLT
®
HVAC Drive Programming Guide
Speed at
Design Point
KNOWN
+
+
+
+
+
+
-
-
-
22-82 Work Point Calculation
Option:
Q ( ow)
®
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
DESIGN
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
been 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
DESIGN
flow at that pressure Q can be determined.
RATED
Similarly, by plotting the design flow (Q
Point D). the pressure H at that flow can be
D
determined. Knowing these two points on the
+
-
-
-
-
+
-
-
-
point and the
has
MIN
, Point C) the
,
DESIGN