VLT® 7000 Booster
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Virtual control curve
The purpose of the Virtual Control Curve is to
compensate for additional friction loss in the pipe
work with increasing flow rate. When a stage is
added to the system, the actual set-point (head)
is increased. When a stage is removed from the
system, the set-point is decreased.
The system automatically calculates virtual set-points
for each stage number. The setpoints 1 and 2 (par.
418 and 419) defines the lowest and the highest
virtual set-points. The number of stages available,
due to pump combination, is part of the calculation,
that defines the virtual set-points.
When the system is running, the number of stages
running determines which virtual set-points to
use. The virtual set-points develop quadratic.
See the following example.
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Example
If the system consists of 4 100% pumps totally,
4 stages are available. Setpoint 1 is set to 50
hPa and setpoint 2 is 80 hPa.
If 1 stage is running, the setpoint is 50 hPa.
If 2 stages are running, the setpoint is 56 hPa.
If 3 stages are running, the setpoint is 66 hPa.
If 4 stages are running, the setpoint is 80 hPa.
The calculated virtual setpoints can be read
from parameter 725.
The virtual control curve is set as default in
par. 417
Feedback function
.
Please refer to par. 417 if another feedback
function is desired.
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Quick Menu 32 Par. 418 setpoint 1
Par. 418 Setpoint 1
(SETPOINT 1)
Value:
Par. 413 Feedback Min.
- Par. 414 Feedback Max.
✭
0.000
Function:
The default feedback process is used when a pressure
feedback signal is measured at the discharge of the
pumps. The cascade controller uses the feedback to
estimate the setpoint required at various rates of flow.
All other reference signals are ignored. Setpoint 1 is the
minimum pressure required when the system is running
with only the lead pump running at full speed.
Description of choice:
Set setpoint 1.
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Quick Menu 33 Par. 419 setpoint 2
Par. 419 Setpoint 2
(SETPOINT 2)
Value:
Par. 413 Feedback Min.
- Par. 414 Feedback Max
✭
0.000
Function:
The default feedback process is used when a pressure
feedback signal is measured at the discharge of the
pumps. The cascade controller uses the feedback to
estimate the setpoint required at various rates of flow.
All other reference signals are ignored. Setpoint 2 is
the maximum pressure required when the system is
running with all pumps at full capacity. A theoretical
value calculates pressure loss in the system under
maximum load. The controller adjusts the loading
based upon the number of pumps in operation.
Description of choice:
Set setpoint 2.
MG.70.A1.02 - VLT is a registered Danfoss trademark
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