Danfoss VLT FC 102 Programming Manual page 201

Parameter Descriptions
NOTICE
Carry out no-flow tuning before setting the PI controller parameters.
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Table 3.25 No-flow Detection
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. Monitoring power enables
detection of no-flow conditions in systems with fluctuating suction pressure, or of the pump having a flat characteristic
towards low speed.
The 2 sets of data must be based on measurement of power at approximately 50% and 85% of maximum speed with the
valves closed. The data is programmed in parameter group 22-3* No-Flow Power Tuning. It is also possible to run a [0] Low
Power Auto Set Up (parameter 22-20 Low Power Auto Set-up) automatically stepping through the commissioning process and
storing the data measured. Set the frequency converter for [0] Open Loop in parameter 1-00 Configuration Mode, when
carrying out the auto set-up, see parameter group 22-3* No-Flow Power Tuning No-flow Power Tuning.
NOTICE
If to use 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 operates 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. Low-speed detection can be used in any
system where operation at minimum speed allows a stop of the motor until the load calls for a speed higher than minimum
speed. This could, for example, be in 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] is set high enough for detection as the pump can run with a rather high
speed even with valves closed.
Dry-pump detection
If the pump has run dry (low power consumption-high speed), no-flow detection can also be used for detecting. Can be
used with both the integrated PI controller and an external PI controller.
M0010001
Programming Guide
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