Operating instructions

3.14.9 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 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 sec. If still overloaded,
the frequency converter will normally trip (causing the pump
to stop by coasting) and provide an alarm.
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 Function at Inverter Overload, par. 14-61 Function at
Inverter Overload to automatically reduce pump speed until
the output current is below 100% of the rated current (set in
par. 14-62 Inv. Overload Derate Current).
The 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 par. 16-35 Inverter
Thermal.
If par. 14-61 Function at Inverter Overload is set to Derate, the
pump speed will be reduced when the counter exceeds 98,
and stay reduced until the counter has dropped below 90.7.
If par. 14-62 Inv. Overload Derate Current is set e.g. to 95% a
steady overload will cause the pump speed to fluctuate
between values corresponding to 110% and 95% of rated
output current for the frequency converter.
14-61 Function at Inverter Overload
Option: Function:
Is used in case of steady overload beyond the
thermal limits (110% for 60 sec.).
[0]
* Trip Choose Trip [0] to make the frequency converter trip
and provide an alarm.
[1] Derate Derate [1] to reduce pump speed in order to
decrease the load on the power section and allowing
this to cool down.
14-62 Inv. Overload Derate Current
Range: Function:
95 % * [50 - 100
%]
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 sec.).
Parameter Description
VLT
®
HVAC Drive Programming Guide
MG.11.CA.02 - VLT
®
is a registered Danfoss trademark 107
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