Danfoss VLT FC 103 Programming Manual page 130

Parameter Description
Head
1
2
Illustration 3.45
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 two 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 two sets of data must be based on measurement of
power at approx. 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 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
[0] Speed Open Loop in 1-00 Configuration Mode , when
carrying out the Auto Set Up (See No Flow Tuning
parameter group 22-3*).
CAUTION
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 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.
®
VLT Refrigeration Drive Programming Guide
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 the action takes place.
Possible Actions to select (22-26 Dry Pump Function):
No Flow Detection must be enabled (22-23 No-Flow
Function) and commissioned (parameter group 22-3*, No
Power Tuning).
22-20 Low Power Auto Set-up
Start of auto set-up of power data for No-Flow Power tuning.
Option:
[0]
[1]
NOTE
Auto Set Up must be done when the system has reached
normal operating temperature!
®
MG16H102 - VLT is a registered Danfoss trademark
CAUTION
- Power consumption below no flow level
- Pump running at maximum speed or maximum
reference open loop, whichever is lowest.
- Warning
- Alarm
Function:
Off
*
Enabled When set for Enabled, an auto set up sequence is
activated, automatically setting speed to approx.
50 and 85% of rated motor speed (4-13 Motor
Speed High Limit [RPM], 4-14 Motor Speed High
Limit [Hz]). At those two speeds, the power
consumption is automatically measured and
stored.
Before enabling Auto Set Up:
1. Close valve(s) in order to create a no
flow condition
2. The frequency converter must be set for
Open Loop (1-00 Configuration Mode).
Note that it is important also to set
1-03 Torque Characteristics.
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