Danfoss VLT AQUA Drive FC 200 Programming Manual page 150

Parameter Description
CAUTION
Carry out No-Flow tuning before setting the PI controller
parameters!
3 3
Figure 3.49
Head
1
2
Figure 3.50
No-Flow Detection is based on the measurement of speed
and power. For a certain speed, the adjustable frequency
drive calculates the power at no-flow.
This coherence is based on the adjustment of two sets of
speed and associated power at no-flow. By monitoring the
power, it is possible to detect no-flow conditions in
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FC
P
MG20O622 - VLT
®
VLT AQUA Drive Programming Guide
systems with fluctuating suction pressure, or if the pump
has a flat characteristic towards low speed.
The two sets of data must be based on measurement of
power at approximately 50% and 85% of maximum speed
with the valve(s) closed. The data are programmed in the
parameter group 22-3*. It is also possible to run a
22-20 Low Power Auto Set-up, automatically stepping
through the commissioning process and also automatically
storing the data measured. The adjustable frequency drive
must be set for Open-loop in 1-00 Configuration Mode,
when carrying out the Auto Set-up (See parameter group
22-3*, No-Flow Power Tuning).
CAUTION
If using the integrated PI controller, carry out No-Flow
tuning before setting the PI controller parameters!
Low speed detection
Low Speed Detection gives a signal if the motor is operating
with minimum speed as set in 4-11 Motor Speed Low Limit
[RPM] or 4-12 Motor Speed Low Limit [Hz]. Actions are
common with No-Flow Detection (individual selection not
possible).
The use of Low Speed Detection is not limited to systems
with a no-flow situation, but can be used in any system
where operation at minimum speed allows for a stop of
the motor until the load calls for a speed higher than
minimum speed, e.g., systems with fans and compressors.
NOTICE!
In pump systems, ensure that the minimum speed in
4-11 Motor Speed Low Limit [RPM] or 4-12 Motor Speed Low
Limit [Hz] has been set high enough for detection as the
pump can run with a rather high speed even with valves
closed.
Dry pump detection
No-Flow Detection can also be used for detecting if the
pump has run dry (low power consumption-high speed).
Can be used with both the integrated PI controller and an
external PI controller.
The condition for Dry Pump signal:
Flow
-
and
-
The signal must be active for a set time (22-27 Dry Pump
Delay) before selected action takes place.
Possible Actions to select (22-26 Dry Pump Function):
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Power consumption below no-flow level
Pump running at maximum speed or maximum
reference open-loop, whichever is lowest.