Danfoss VLT HVAC Drive FC 102, Programming Manual, Page: 163 / 250

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, 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, for
example 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:
•
Power consumption below no-flow level
and
•
Pump running at maximum speed or maximum reference open loop, whichever is lowest.
The signal must be active for a set time ( parameter 22-27 Dry Pump Delay ) before the selected action takes place.
Possible actions to select ( parameter 22-26 Dry Pump Function ):
•
Warning
•
Alarm
No-flow detection must be enabled ( parameter 22-23 No-Flow Function ) and commissioned (parameter group 22-3* No-Flow
Power Tuning ).
22-20 Low Power Auto Set-up
Start of auto set-up of power data for no-flow power tuning.
Option: Function:
[0]
*
Off
[1] Enabled
NOTICE
Auto set-up must be done when the
system has reached normal operating
temperature!
NOTICE
It is important that parameter 4-13 Motor
Speed High Limit [RPM] or
parameter 4-14 Motor Speed High Limit [Hz]
is set to the maximum operational speed
of the motor.
It is important to do the auto set-up before
configuring the integrated PI controller as
settings are reset when changing from
closed to open loop in
parameter 1-00 Configuration Mode .
22-20 Low Power Auto Set-up
Start of auto set-up of power data for no-flow power tuning.
Option: Function:
NOTICE
Carry out the tuning with the same
settings in
parameter 1-03 Torque Charac-
teristics , as for operation after the tuning.
An auto set-up sequence is activated, automat-
ically setting speed to approximately 50% and
85% of rated motor speed (
parameter 4-13 Motor
Speed High Limit [RPM] , parameter 4-14 Motor
Speed High Limit [Hz] ). At those 2 speeds, the
power consumption is automatically measured
and stored.
Before enabling auto set-up:
1. Close valve(s) to create a no-flow
condition.
2. Set the frequency converter to open-
loop (
parameter 1-00 Configuration Mode ).
Note that it is important also to set
parameter 1-03 Torque Characteristics .
Parameter Descriptions Programming Guide
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