Danfoss VLT FC 103 Programming Manual page 139

Parameter Description
22-82 Work Point Calculation
Option:
3 3
138
Function:
Example 1:
H
(head)
H
A
DESIGN
Set Point
H
MIN
Par.:
22-83/ Control Curve
22-84/
22-87
Q
(flow)
Illustration 3.53 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 point and the
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
DESIGN
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 which will also include the System design
Working Point A.
MG16H102 - VLT
®
VLT Refrigeration Drive Programming Guide
22-82 Work Point Calculation
Option:
[0] Disabled Work Point Calculation not active. To be used if
*
[1] Enabled Work Point Calculation is active. Enabling this
has
MIN
22-83 Speed at No-Flow [RPM]
Range:
Size
related
*
, Point C) the
,
DESIGN
®
is a registered Danfoss trademark
Function:
H (head)
H
RATED D
Par.
B
A
22-88
C
H
DESIGN
Set point
H
MIN
Par.:
22-83/
Control Curve
22-84/
22-87
Q Q
DESIGN RATED
(flow)
Par. Par.
22-90
22-89
Illustration 3.54
speed at design point is known (see Table 3.26).
parameter allows the calculation of the unknown
System Design Working Point at 50/60 Hz speed,
from the input data set in 22-83 Speed at No-Flow
[RPM] 22-84 Speed at No-Flow [Hz], 22-87 Pressure
at No-Flow Speed, 22-88 Pressure at Rated Speed,
22-89 Flow at Design Point and 22-90 Flow at Rated
Speed.
Function:
[ 0 - par. Resolution 1 RPM.
22-85 The speed of the motor at which flow Is
RPM] zero and minimum pressure H
achieved should be entered here in RPM.
Alternatively, the speed in Hz can be
entered in 22-84 Speed at No-Flow [Hz]. If
it has been decided to use RPM in
0-02 Motor Speed Unit then 22-85 Speed at
Design Point [RPM] should also be used.
Closing the valves and reducing the
speed until minimum pressure H
achieved will determine this value.
Q
is
MIN
is
MIN