Danfoss VLT AQUA Drive FC 200 Programming Manual page 111

Parameter Description
3.13.7 No Trip at Inverter Overload
In some pump systems, the frequency converter has not
been sized properly to yield the current needed in all
points of the operational flow-head characteristic. At these
3 3 points, the pump will need a current higher than the rated
current of the frequency converter. The frequency
converter can yield 110% of the rated current continuously
for 60 s. If still overloaded, the frequency converter will
normally trip (causing the pump to stop by coasting) and
provide an alarm.
Current
% of rated
110
105
100
95
Inverter
load
counter
100
98
90.7
Illustration 3.42
It may be preferable to run the pump at reduced speed for
a while in case it is not possible to run continuously with
demanded capacity.
Select 14-61 Function at Inverter Overload to automatically
reduce pump speed until the output current is below
100% of the rated current (set in 14-62 Inv. Overload Derate
Current).
14-61 Function at Inverter Overload is an alternative to
letting the frequency converter trip.
The frequency converter estimates the load on the power
section by means of an inverter load counter, which will
cause a warning at 98% and a reset of the warning at 90%.
At the value 100%, the frequency converter trips and
provides an alarm.
Status for the counter can be read in 16-35 Inverter
Thermal.
If 14-61 Function at Inverter Overload is set to [3] Derate, the
pump speed will be reduced when the counter exceeds
98, and stay reduced until the counter has dropped below
90.7.
If 14-62 Inv. Overload Derate Current is set e.g. to 95% a
steady overload will cause the pump speed to fluctuate
110
VLT
~ ~
60s
Desired current>100%
Warning Warning
MG20O602 - VLT
®
AQUA Drive Programming Guide
between values corresponding to 110% and 95% of rated
output current for the frequency converter.
14-61 Function at Inverter Overload
Is used in case of steady overload beyond the thermal limits
(110% for 60 s).
Option:
[0] Trip
[1] Derate [1] Derate reduces pump speed in order to
*
14-62 Inv. Overload Derate Current
Range:
95 % [50 - 100
*
%]
Time
Time
®
is a registered Danfoss trademark
Function:
Choose [0] Trip to make the frequency converter
trip and provide an alarm.
decrease the load on the power section and
allowing this to cool down.
Function:
Defines the desired current level (in % of
rated output current for the frequency
converter) when running with reduced
pump speed after load on the frequency
converter has exceeded the allowable limit
(110% for 60 s).