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
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
(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
, the frequency converter never starts.
N
RPM
T
N
1-86
T
1-79
T
1-71
0
1
T
1-71
Parameter 1-71 Start Delay
.
T
1-79
Parameter 1-79 Pump Start Max Time to Trip
. This time
includes the time in T
1-71
.
N
1-86
Parameter 1-86 Trip Speed Low [RPM]
. If the speed
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:
Function:
Size
related
*
[ 0 -
par.
4-13
RPM]
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
1-86 Trip Speed Low [RPM]
Range:
Function:
a stop) drops below the value in the
parameter, the frequency converter trips
with
alarm 49, Speed Limit
.
1-87 Trip Speed Low [Hz]
Range:
Function:
Size
related
*
[ 0 -
par.
4-14
Hz]
NOTICE
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
.
3.3.14 1-9* Motor Temperature
1-90 Motor Thermal Protection
Option:
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
.
•
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
M,N
and the rated motor
frequency f
M,N
. See
and
.
•
Via a mechanical thermal switch
(Klixon type). See
.
For the North American market: The ETR
functions provide class 20 motor overload
protection in accordance with NEC.
[0]
No
protection
Continuously overloaded motor, when no
warning or trip of the frequency converter is
required.
[1]
Thermistor
warning
Activates a warning when the connected
thermistor or KTY sensor in the motor reacts if
motor overtemperature occurs.
Parameter Description
VLT
®
AQUA Drive FC 202
58
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MG20OB02
3
3
Содержание VLT AQUA Drive FC 202
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