Deragging Overview - Danfoss VLT AQUA Drive FC 202 Design Manual

Product Features
5.5.1.1 Pump Staging with Lead Pump
Alternation
With lead pump alternation enabled, a maximum of 2
pumps are controlled. At an alternation command, the PID
stops, the lead pump ramps to minimum frequency (f
and, after a delay, it ramps to maximum frequency (f
When the speed of the lead pump reaches the destaging
frequency, the fixed-speed pump is cut out (destaged). The
lead pump continues to ramp up and then ramps down to
a stop and the 2 relays are cut out.
Alternation
command/PID stops
f
max
Destaging freq.
f
min
f
max
Staging freq.
AC line operation
Figure 5.11 Lead Pump Alternation
After a time delay, the relay for the fixed-speed pump cuts
in (staged) and this pump becomes the new lead pump.
The new lead pump ramps up to maximum speed and
then down to minimum speed. When ramping down and
reaching the staging frequency, the old lead pump is now
cut in (staged) on the mains as the new fixed-speed pump.
If the lead pump has been running at minimum frequency
(f ) for a programmed amount of time, with a fixed-
min
speed pump running, the lead pump contributes little to
the system. When the programmed value of the timer
expires, the lead pump is removed, avoiding water heating
problems.
5.5.1.2 System Status and Operation
If the lead pump goes into sleep mode, the function is
shown on the LCP. It is possible to alternate the lead pump
on a sleep mode condition.
When the cascade controller is enabled, the LCP shows the
operation status for each pump and the cascade controller.
Information shown includes:
•
Pump status is a readout of the status for the
relays assigned to each pump. The display shows
pumps that are disabled, off, running on the
drive, or running on the mains/motor starter.
•
Cascade status is a readout of the status for the
cascade controller. The display shows the
following:
MG22B222
Design Guide
)
min
).
max
AC line operation
Time
PID contr.
starts
5s
Time
Danfoss A/S © 01/2018 All rights reserved.
- Cascade controller is disabled.
- All pumps are off.
- An emergency has stopped all pumps.
- All pumps are running.
- Fixed-speed pumps are being staged/
destaged.
- Lead pump alternation is occurring.
•
Destage at no-flow ensures that all fixed-speed
pumps are stopped individually until the no-flow
status disappears.

5.6 Deragging Overview

The purpose of the deragging feature is to free the pump
blade of debris in waste-water applications so that the
pump operates normally.
A deragging event is defined as the time when the drive
starts to derag to when the deragging finishes. When a
derag is started, the drive ramps first to a stop and then
an off delay expires before the first cycle begins.
Speed
Derag
function
activated
+/- Derag
Speed:
Par.: 29 -13
Par.: 29 -14
Derag O Delay:
Par. 29 -15
0 Hz / RPM
Deragging Run Time : Par . 29-12
1 Cycle
Number of Cycles : Par . 29 -10
Figure 5.12 Derag Function
5 5
29