Danfoss VLT FC 103 Programming Manual page 134

Parameter Description
p (Pressure)
P
Boost
P 22-45
P
Set
P 22-44
P
Wake
f (Frequency)
f
out
Ref
No/Low Flow
detected
Illustration 3.47
If no flow is detected, the frequency converter will increase
the set point for pressure to ensure a slight over pressure
in the system (boost to be set in 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
will ramp up again and pressure will be controlled for
reaching the set value (P ).
set
FC 103
External PID
controller
f
Ref
p
System
f
Out
Illustration 3.48
®
VLT Refrigeration Drive Programming Guide
P
System
Time
t
Time
Sleep mode
1
activated
p = p
Boost System Wake
activated
), the motor
set
p
Set
®
MG16H102 - VLT is a registered Danfoss trademark
2) In systems where the pressure or temperature is
controlled by an external PI controller, the wake up
conditions can not be based on feedback from the
pressure/temperature transducer as the setpoint is not
known. In the example with a boost system, desired
pressure Pset is not known. Par. 1-00, Configuration mode,
must be set for Open Loop.
Example: Boost system.
p
(Pressure)
P
Set
f f
(Frequency)
Ref Out
f f
Ref / Out
f
Wake
t
1
No/Low Flow Sleep mode
detected activated
Illustration 3.49
When low power or low speed is detected the motor is
stopped, but the reference signal (f
controller is still monitored and because of the low
pressure created, the controller will increase the reference
signal to gain pressure. When the reference signal has
reached a set value f the motor restarts.
wake
The speed is set manually by an external reference signal
(Remote Reference). The settings (parameter group 22-3*)
for tuning of the No Flow function must be set to default.
p
System
Time
f
Ref
f
Out
Time
P = P
Ref Wake
) from the external
ref
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