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 suc-
tion pressure varies. Enhanced sleep mode provides
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
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.
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 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 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 frequency converter is running at maxi-
mum frequency (parameter 202
Output fre-
quency 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 frequen-
cy converter will trip.
The frequency converter can be set up for either man-
ual 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 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 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
frequency converter then automatically calculates all
data in-between those two sets of values and gener-
ates 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.
106
MG.27.E2.02 - VLT is a registered Danfoss trademark
