Danfoss VLT AQUA Drive FC 202 Programming Manual page 60

Parameter Description
3.3.13 Advanced Minimum Speed
Monitoring for Submersible Pumps
Some pumps are sensitive to operating at low speed.
Insufficient cooling or lubrication at low speed are typical
3 3
reasons.
Under overload conditions, the frequency converter
protects itself using its integral protection features, which
include lowering the speed. For example, the current limit
controller can lower the speed. Sometimes, the speed may
go lower than the speed specified in parameter 4-11 Motor
Speed Low Limit [RPM] and parameter 4-12 Motor Speed Low
Limit [Hz].
If the speed drops below a certain value, the advanced
minimum-speed monitoring feature trips the frequency
converter. If the pump motor does not reach the speed
specified in parameter 1-86 Trip Speed Low [RPM] within the
time specified in parameter 1-79 Pump Start Max Time to
Trip (ramping up takes too long), the frequency converter
trips. Timers for parameter 1-71 Start Delay and
parameter 1-79 Pump Start Max Time to Trip start at the
same time when the start command is issued. For instance,
this means that if the value in parameter 1-71 Start Delay is
more than or equal to the value in parameter 1-79 Pump
Start Max Time to Trip, the frequency converter never starts.
T Parameter 1-71 Start Delay.
1-71
T Parameter 1-79 Pump Start Max Time to Trip. This time
1-79
includes the time in T
N Parameter 1-86 Trip Speed Low [RPM]. If the speed
1-86
drops below this value during normal operation, the
frequency converter trips.
1 Normal operation.
Illustration 3.11 Advanced Minimum Speed Monitoring
1-86 Trip Speed Low [RPM]
Range:
Size [ 0 -
related par.
*
4-13
RPM]
58
VLT
N
RPM
1
N
1-86
0 T T
T
1-79
1-71
.
1-71
Function:
NOTICE
This parameter is only available if
parameter 0-02 Motor Speed Unit is set
to [11] RPM.
Enter the low limit for the motor speed at
which the frequency converter trips. If the
value is 0, the function is not active. If the
speed at any time after the start (or during
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®
AQUA Drive FC 202
1-86 Trip Speed Low [RPM]
Range:
1-87 Trip Speed Low [Hz]
Range:
Size
related par.
*
4-14
Hz]
3.3.14 1-9* Motor Temperature
1-90 Motor Thermal Protection
Option:
[0] No
protection
[1] Thermistor
warning
Function:
a stop) drops below the value in the
parameter, the frequency converter trips
with alarm 49, Speed Limit.
Function:
NOTICE
[ 0 -
This parameter is only available if
parameter 0-02 Motor Speed Unit is set
to [1] Hz.
Enter the low limit for the motor speed at
which the frequency converter trips. If the
value is 0, the function is not active. If the
speed at any time after the start (or during a
stop) drops below the value in the
parameter, the frequency converter trips with
alarm 49, Speed Limit.
Function:
Motor thermal protection can be implemented
using a range of techniques:
•
Via a PTC sensor in the motor
windings connected to 1 of the
analog or digital inputs
(parameter 1-93 Thermistor Source).
See chapter 3.3.15 PTC Thermistor
Connection.
•
Via calculation (ETR = Electronic
Thermal Relay) of the thermal load,
based on the actual load and time.
The calculated thermal load is
compared with the rated motor
current I and the rated motor
M,N
frequency f . See chapter 3.3.16 ETR
M,N
and chapter 3.3.17 ATEX ETR.
•
Via a mechanical thermal switch
(Klixon type). See
chapter 3.3.18 Klixon.
For the North American market: The ETR
functions provide class 20 motor overload
protection in accordance with NEC.
Continuously overloaded motor, when no
warning or trip of the frequency converter is
required.
Activates a warning when the connected
thermistor or KTY sensor in the motor reacts if
motor overtemperature occurs.
MG20OB02