Danfoss VLT HVAC Series User Manual

3.14.9 No Trip at Inverter Overload
In some pump systems, the adjustable frequency drive 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 adjustable frequency drive. The adjustable frequency
drive can yield 110% of the rated current continuously for 60 sec. If still overloaded, the adjustable frequency drive 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 at 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 adjustable frequency drive trip.
The adjustable frequency drive 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 adjustable frequency drive 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, for example, to 95% a steady overload will cause the pump speed to fluctuate between values corre-
sponding to 110% and 95% of rated output current for the adjustable frequency drive.
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 adjustable frequency drive 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.
3 Parameter Description VLT
®
HVAC Drive Programming Guide
3-142 MG.11.C6.22 - VLT
®
is a registered Danfoss trademark
3

Danfoss VLT HVAC Series Specifications

General

Protection Features	Overcurrent, Overvoltage, Undervoltage, Overtemperature, Short circuit
Communication Interfaces	Profibus, Ethernet
Cooling Method	Forced convection
Ambient Temperature	-10°C to +40°C
Enclosure Rating	IP20, IP21, IP55
Output Voltage	0 - 100% of supply voltage