Danfoss VLT AQUA Drive FC 200 Programming Manual page 176

Parameter Description
25-22 Fixed Speed Bandwidth
Range:
Size [ par.
3 3
related 25-20 -
*
par.
25-21
%]
25-23 SBW Staging Delay
Range:
15 [1 -
s 3000 s]
*
25-24 SBW De-staging Delay
Range:
15 [0 -
s 3000 s]
*
3-150
Function:
When the cascade control system is running
normally and the adjustable frequency drive
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 de-staging 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.
If the issued alarm is a trip-lock alarm, 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.
SBW (27-20)
SBW (27-20)
SBW staging-vertr. (27-23)
Figure 3.70
Function:
Immediate de-staging of a fixed-speed pump is
not desirable during a momentary pressure
MG20O622 - VLT
®
VLT AQUA Drive Programming Guide
25-24 SBW De-staging Delay
Range:
25-25 OBW Time
Range:
10 [0 -
s 300 s]
*
Setpoint
Figure 3.72
®
is a registered Danfoss trademark
Function:
increase in the system that exceeds the staging
bandwidth (SBW). De-staging 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
Figure 3.71
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
stabilized and normal control has been established.
Set the timer to a value that allows the system to
stabilize after staging. The 10 second 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)