Danfoss VLT AQUA Drive FC 202 Programming Manual page 153

Parameter Description
CAUTION
Carry out No Flow tuning before setting the PI controller
parameters!
FC
P
Illustration 3.55 No Flow Detection Scheme
Head
1
2
Illustration 3.56 No Flow Detection Graph
No Flow Detection is based on the measurement of speed
and power. For a certain speed the frequency converter
calculates the power at no flow.
This coherence is based on the adjustment of 2 sets of
speed and associated power at no flow. By monitoring the
power it is possible to detect no flow conditions in
systems with fluctuating suction pressure or if the pump
has a flat characteristic towards low speed.
The 2 sets of data must be based on measurement of
power at approx. 50% and 85% of maximum speed with
MG20O702
Programming Guide
the valve(s) closed. The data are programmed in the
parameter group 22-3* No Flow Power Tuning. It is also
possible to run a parameter 22-20 Low Power Auto Set-up,
automatically stepping through the commissioning process
and also automatically storing the data measured. The
frequency converter must be set for open loop in
parameter 1-00 Configuration Mode, when carrying out the
Auto Set-Up (See parameter group 22-3* No-Flow Power
Tuning).
CAUTION
When 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 parameter 4-11 Motor Speed
Low Limit [RPM] or parameter 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
parameter 4-11 Motor Speed Low Limit [RPM] or
parameter 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:
•
and
•
Flow
The signal must be active for a set time
(parameter 22-27 Dry Pump Delay) before selected the
action takes place.
Possible Actions to select (parameter 22-26 Dry Pump
Function):
•
•
Enable the low power detection in parameter 22-21 Low
Power Detection. Perform the tuning using parameter
group 22-3*, No-Flow Power Tuning.
Danfoss A/S © Rev. 2014-01-21 All rights reserved.
Power consumption below no flow level
Pump running at maximum speed or maximum
reference open loop, whichever is lowest.
Warning
Alarm
3 3
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