Enhanced Sleep Mode - Danfoss VLT 2800 Design Manual

Programming
457 Phase loss function
Value:
Trip (TRIP)
Autoderate & warning (AUTODERATE & WARNING)
Warning (WARNING)
Function:
Select the function which is to be activated if the mains
imbalance becomes too high or if a phase is missing.
Description of choice:
At [0] Trip, the adjustable frequency drive stops the motor
within a few seconds (depending on frequency converter
size).
If [1] Autoderate & warning is selected, the frequency
converter exports a warning and reduces the output
current to 50 % of I to maintain operation.
VLT,N
At [2] Warning, only a warning is exported when a mains
failure occurs, but in severe cases, other extreme
conditions might result in a trip.
WARNING
If Warning is selected, the life expectancy of the drive
may be reduced when the mains failure persists.
461 Feedback conversion
Value:
Linear (LINEAR)
Square root (SQUARE ROOT)
Function:
In this parameter, a function is selected which converts a
connected feedback signal from the process to a feedback
value that equals the square root of the connected signal.
This is used, e.g. where regulation of a flow (volume) is
required on the basis of pressure as feedback signal (flow
pressure ). This conversion makes it
= constant x
possible to set the reference in such a way that there is a
linear connection between the reference and the flow
required.
Description of choice:
If [0] Linear is selected, the feedback signal and the
feedback value is proportional. If [1] Square root is selected,
the frequency converter translates the feedback signal to a
squared feedback value.
MG27E402
Design Guide

4.6 Enhanced Sleep Mode

The enhanced sleep mode has been developed to work
under all conditions and to overcome problems when
[0]
using pumps with flat pump curves or when suction
[1]
pressure varies. Enhanced sleep mode provides excellent
[2]
control for shutting down the pump at low flow, thus
saving energy.
If the system operates with constant pressure control, a
drop in the suction pressure may lead to an increase in
frequency to maintain pressure. Consequently, the
frequency may vary independent of the flow. This can lead
to inappropriate activation of sleep mode or wake-up of
the adjustable frequency drive.
Flat pump curves leads to a situation where there is little
or no change in frequency in response to flow variation.
Consequently, the adjustable frequency drive might not
reach the sleep frequency when setting it at a low value.
Enhanced sleep mode is based on power/frequency
monitoring and works in closed loop only. Stop due to the
enhanced sleep mode function is initiated under the
following conditions:
•
•
[0]
[1]
If the feedback pressure drops below the wake-up pressure
(parameter 464 Wake-up pressure), the adjustable frequency
drive restarts the motor.
Danfoss A/S © Rev. May/2014 All rights reserved.
Power consumption is below the no/low flow
power curve and stays there for a certain time
(parameter 462 Enhanced sleep mode timer) or
The pressure feedback is above the reference
when running at minimum speed and stays there
for a certain time (parameter 462 Enhanced sleep
mode timer).
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