Enhanced Sleep Mode
The enhanced sleep mode has been developed to
work under all conditions and to overcome problems
when using pumps with flat pump curves, or when
suction pressure varies. Enhanced sleep mode pro-
vides excellent control for shutting down the pump at
low-flow, thus saving energy.
If operating with constant pressure control in the SYS-
TEM, 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 in-
appropriate activation of sleep mode or wake-up of the
adjustable frequency drive.
Flat pump curves leads to a situation where there will
be 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:
•
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 refer-
ence when running at minimum speed and
stays there for a certain time (parameter 462
Enhanced sleep mode timer
).
If the feedback pressure falls below the wakeup pres-
sure (Parameter 464
Wakeup pressure
), the adjustable
frequency drive 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 detec-
tion feature.
How Does It Work?
Dry run detection is based on power/frequency moni-
toring and works in both closed and open loop.
Stop (trip) due to dry run is initiated under following
conditions:
Closed loop:
•
The adjustable frequency drive is running at
maximum frequency (parameter 202
Output
frequency high limit
, f
MAX
)
and
•
Feedback is below minimum reference (pa-
rameter 204
Minimum reference
, Ref,
MIN
)
and
•
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 adjust-
able frequency drive will trip.
The adjustable frequency drive can be set up for either
manual or automatic restart after stop (parameters 405
Reset function
and 406
Automatic restart time
).
•
Enhanced Sleep Mode and Dry Run Detec-
tion can be enabled and disabled independ-
ently. This is done in parameter 462
Enhanced sleep mode timer
and parameter
470
Dry run timeout
.
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 situa-
tion.
It is only necessary to enter two sets of values for pow-
er and frequency (min and max) at no or low flow. The
adjustable frequency drive then automatically calcu-
lates 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 adjustable frequency drive enters Sleep-mode or
trips due to dry run, depending on the configuration.
VLT
®
2800 Series
MG.27.A2.22 - VLT
®
is a registered Danfoss trademark
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