NOTICE
3-41 Ramp 1 Ramp Up Time
and
3-42 Ramp 1 Ramp Down
Time
must be the same for the master drive and for all
follower drives in the system.
4.
Set the ramps fast enough to enable the PID
controller to maintain control of the system.
4.1.3 Closed Loop Control
The master drive is the primary controller for the system. It
monitors the output pressure, adjusts the speed of the
frequency converters and decides when to add or remove
stages.
To perform this function:
1.
setup the master drive closed loop mode with a
feedback sensor connected to an analog input of
the frequency converter.
2.
setup the PID controller of the master drive to
match the needs of the installation.
For further information on setting up the PID parameters,
see the
VLT
®
AQUA Drive Programming Guide
. See also
6.1 Master/Follower
.
4.1.4 Staging/De-staging of Variable Speed
Pumps
Staging occurs when the speed of the frequency converter
has reached the value in
27-31 Stage On Speed [RPM]
(
27-32 Stage On Speed [Hz]
). At this speed the system
pressure is still maintained but the pumps start to operate
outside of their peak efficiency points. Staging on an
additional pump will lower the speed of all running pumps
and provide a more energy efficient operation.
In master-follower configurations and mixed pump config-
urations the variable speed pumps are staged and de-
staged based on the speed of the frequency converters.
De-staging occurs when the speed of the frequency
converters drops below the value in
27-33 Stage Off Speed
[RPM]
(
27-34 Stage Off Speed [Hz]
). At this speed the system
pressure is still maintained but the pumps are beginning
to operate below their peak efficiency points. De-staging a
pump will cause the speed of the frequency converters to
increase into a more energy efficient range.
27-31 Stage On Speed [RPM]
(
27-32 Stage On Speed [Hz]
) and
27-33 Stage Off Speed [RPM]
(
27-34 Stage Off Speed [Hz]
) are
installation dependent. These parameters are indexed
parameters with one set of entries for each pump stage.
The stage on and de-stage off speed can be auto tuned
during automation or set manually. If Auto-tune is enabled
the system will start operation using default settings or the
pre settings done by the user in
27-31 Stage On Speed
[RPM]
(
27-32 Stage On Speed [Hz]
) and
27-33 Stage Off
Speed [RPM]
(
27-34 Stage Off Speed [Hz]
) before enabling
the auto-tune.
The tuning ensures optimum energy efficiency of the
system. See
Illustration 4.2
.
P
tot
A
B
C
t
1
2
130BB024.11
Illustration 4.2
1 1 pump running
2 2 pumps running
A Incorrect stage on speed adjustment
B Correct stage on speed adjustment
C Stage on speed pump 2
Table 4.2
During operation the system monitors the actual energy
consumption and optimises every time a stage or de-stage
takes place.
Parameter
Range
Default
27-30 Auto Tune
Staging Speeds
{[0] Disabled, [1]
Enabled}
[1] Enabled
Table 4.3
4.1.5 Staging/De-staging of Fixed Speed
Pumps
Fixed speed pumps are staged based or de-staged based
on system pressure.
To avoid rapid turning on and off of pumps, define an
acceptable range of system pressure along with a period
of time the pressure is allowed to be outside of this band
before staging or de-staging occurs. Set the values
through:
Configuring the System
VLT
®
AQUA Drive MCO 101/MCO 102
MI38C402 - VLT
®
is a registered Danfoss trademark
17
4
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