Danfoss VLT AQUA Drive FC 202 Programming Manual page 178

Parameter Description
25-21 Override Bandwidth
Range:
3 3
25-22 Fixed Speed Bandwidth
Range:
Size [ par.
related 25-20 -
*
par.
25-21
%]
25-23 SBW Staging Delay
Range:
15 [0 -
s 3000
*
s]
176
Function:
controller, initially leave the OBW at the factory
setting of 100% (Off). When the fine tuning is
completed, the OBW should be set to the
desired value. An initial value of 10% is
suggested.
Function:
When the cascade control system is running
normally and the frequency converter issues
a trip alarm, it is important to maintain the
system head. The cascade controller does
this by continuing to stage/destage the fixed
speed pump on and off. Due to the fact that
keeping the head at the setpoint would
require frequent staging and destaging when
only a fixed speed pump is running, a wider
Fixed Speed Bandwidth (FSBW) is used
instead of SBW. It is possible to stop the
fixed speed pumps, in case of an alarm
situation, by pressing [Off] or [Hand On] or if
the signal programmed for Start on digital
input goes low.
In case the issued alarm is a trip-lock alarm
then the cascade controller must stop the
system immediately by cutting out all the
fixed speed pumps. This is basically the same
as Emergency Stop (Coast/Coast inverse
Command) for the cascade controller.
Function:
Immediate staging of a fixed speed pump is not
desirable when a momentary pressure drop in the
system exceeds the Staging Bandwidth (SBW).
Staging is delayed by the length of time
programmed. If the pressure increases to within the
SBW before the timer has elapsed, the timer is
reset.
Illustration 3.76 SBW Staging Delay
Danfoss A/S © Rev. 2014-01-21 All rights reserved.
Programming Guide
25-24 SBW Destaging Delay
Range:
15 [0 -
s 3000
*
s]
25-25 OBW Time
Range:
10 [0 -
s 300 s]
*
Illustration 3.78 OBW Time
Function:
Immediate destaging of a fixed speed pump is not
desirable when a momentary pressure increase in
the system that exceeds the Staging Bandwidth
(SBW). Destaging is delayed by the length of time
programmed. If the pressure decreases to within
the SBW before the timer has elapsed, the timer is
reset.
(27-24) SBW destage delay
Illustration 3.77 SBW Destaging Delay
Function:
Staging a fixed speed pump creates a momentary
pressure peak in the system, which might exceed
the Override Bandwidth (OBW). It is not desirable to
destage a pump in response to a staging pressure
peak. The OBW Time can be programmed to
prevent staging until the system pressure has
stabilised and normal control established. Set the
timer to a value that allows the system to stabilise
after staging. The 10 s factory setting is appropriate
in most applications. In highly dynamic systems, a
shorter time may be desirable.
OBW (27-71)
SBW (27-70)
Actual head
Setpoint
SBW (27-70)
OBW (27-71)
OBW timer (27-25)
SBW
(27-20)
Setpoint
SBW
(27-20)
MG20O702