Danfoss VLT AQUA Drive FC 202 Programming Manual page 157

Parameter Description
stops energizing the motor. When in sleep mode, certain
conditions are monitored to find out when load has been
applied to the system again.
Sleep mode can be activated either from the no flow
detection/minimum speed detection or via an external
signal applied to one of the digital inputs (must be
programmed via the parameters for configuration of the
digital inputs, parameter group 5-1* Digital Inputs).
To make it possible to use e.g. an electro-mechanical flow
switch to detect a no flow condition and activate Sleep
Mode, the action takes place at raising edge of the
external signal applied (otherwise the frequency converter
would never come out of Sleep Mode again as the signal
would be steady connected).
If parameter 25-26 Destage At No-Flow, is set for [1] Enabled,
activating sleep mode applies a command to the cascade
controller (if enabled) to start de-staging of lag pumps
(fixed speed) before stopping the lead pump (variable
speed).
When entering sleep mode, the lower status line in the
LCP shows Sleep Mode.
See also signal flow chart, Illustration 3.54.
There are 3 different ways of using the sleep mode
function:
Illustration 3.57 Legend: FC=frequency converter;
f =frequency out; P =P system; P
O S
1) Systems where the integrated PI controller is used for
controlling pressure or temperature e.g. boost systems
with a pressure feed back signal applied to the frequency
converter from a pressure transducer.
MG20O702
Programming Guide
=P setpoint
SL
Danfoss A/S © Rev. 2014-01-21 All rights reserved.
Parameter 1-00 Configuration Mode, must be set for Closed
Loop and the PI Controller configured for desired reference
and feed back signals.
Example: Boost system.
p (Pressure)
P
Boost
P 22-45
P
Set
P 22-44
P
Wake
f (Frequency)
f
out
Ref
No/Low Flow
detected
Illustration 3.58 Boost System with Pressure Feedback
If no flow is detected, the frequency converter increases
the set point for pressure to ensure a slight over pressure
in the system (boost to be set in parameter 22-45 Setpoint
Boost).
The feedback from the pressure transducer is monitored
and when this pressure has dropped with a set percentage
below the normal set point for pressure (P
ramps up again and pressure is controlled for reaching the
set value (P ).
set
FC
External PID
controller
f
Ref
P
System
f
Out
P
Illustration 3.59 System with Pressure Feedback
2) In systems where the pressure or temperature is
controlled by an external PI controller, the wake up
P
System
Time
t
Time
Sleep mode
1
activated
p = p
System Wake
Boost
activated
), the motor
set
P
Set
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