Enhanced Sleep Mode - Danfoss VLT 8000 AQUA series Operating Instructions Manual

Enhanced Sleep Mode

Using the frequency for initiating sleep-mode is
acceptable in many cases, but if the suction pressure
is varying or the pump has a flat pump curve toward
low speed, this method might not be accurate enough.
The enhanced sleep mode has been developed to
overcome problems under such conditions.
If operating with constant pressure control in the
system, for instance a drop in the suction pressure
will lead to an increase in frequency to maintain
pressure. Consequently there is a situation, where
the frequency will vary independent of the flow. This
can lead to inappropriate activation of sleep mode
or wake-up of the frequency converter.
Flat pump curves leads to a situation where there
will be little or no change in frequency in response
to flow variation. Consequently, the frequency
converter might not reach the sleep frequency
when setting it at a low value.
How Does It Work?
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:
• Power consumption is below the no/low flow power
curve and stays there for a certain time (parameter
463 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 463
Enhanced sleep mode timer).
If the feedback pressure falls below the wakeup
pressure (Parameter 464 Wakeup pressure), the
frequency converter restarts the motor.
Dry Run Detection
For most pumps, especially submersible bore-hole
pumps, it must be assured that the pump is
stopped in case of dry run. This is assured by
the Dry run detection feature.
= factory setting. () = display text [] = value for use in communication via serial communication port
MG.83.A2.02 - VLT is a registered Danfoss trademark
®
VLT 8000 AQUA
How Does It Work?
Dry run detection is based on power/frequency
monitoring and works in both closed and open loop.
Stop (trip) due to dry run is initiated under
following conditions:
• Closed loop:
• The frequency converter is running at maximum
frequency (parameter 202 Output frequency
high limit, f ) and
MAX
• Feedback is below minimum reference (parameter
204 Minimum reference, Ref,
• Power consumption is below the no/low flow
power curve for a certain time (parameter
470 Dry run time out)
• Open loop:
• Whenever the power consumption is below
the no/low flow power curve for a certain
time (parameter 470 Dry run time out) the
frequency converter will trip.
• The frequency converter can be set up for either
manual or automatic restart after stop (parameters 400
Reset function and 401 Automatic restart time).
Enabling and disabling the features
• Enhanced Sleep Mode and Dry Run Detection
can be enabled and disabled independently. This
is done in parameter 463 Enhanced sleep mode
timer and parameter 470 Dry run time out.
Centrifugal pumps with radial impellers show a clear
one-to-one relation between power consumption and
flow, which is utilized to detect a no or low flow situation.
It is only necessary to enter two sets of values for
power and frequency (min and max) at no or low flow.
The frequency converter then automatically calculates
all data in-between those two sets of values and
generates the no/low flow power curve.
If the power consumption falls below the power curve,
the frequency converter enters Sleep-mode or trips
due to dry run, depending on the configuration.
) and
MIN
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